\jC) lu * Ck^ HARVARD UNIVERSITY Ernst Mayr Library of the Museum of Comparative Zoology TfieWlsonBulletin PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY VOL. 117, NO. 1 MARCH 2005 PAGES 1-112 (ISSN 0043-5643) libf?ary THE WILSON ORNITHOLOGICAL SOCIETY FOUNDED DECEMBER 3, 1888 Named after ALEXANDER WILSON, the first American Ornithologist. President — Charles R. Blem, Dept, of Biology, Virginia Commonwealth Univ., Richmond, VA 23284, USA; e-mail: cblem@saturn.vcu.edu First Vice-President — Doris J. Watt, Dept, of Biology, Saint Mary’s College, Notre Dame, IN 46556, USA; e-mail: dwatt@saintmarys.edu Second Vice-President — James D. Rising, Dept, of Zoology, Univ. of Toronto, Toronto, ON M5S 3G5, Canada; e-mail: rising@zoo.utoronto.ca Editor — James A. Sedgwick, U.S. Geological Survey, Fort Collins Science Center, 2150 Centre Ave., Bldg. C, Fort Collins, CO 80526, USA; e-mail: wilsonbulletin@usgs.gov Secretary — Sara R. Morris, Dept, of Biology, Canisius College, Buffalo, NY 14208, USA; e-mail: morriss@canisius.edu Treasurer — Martha Vaughan, 9 Bennets Neck Dr., Pocasset, MA 02559, USA; e-mail: jkricher@wheatonma.edu Elected Council Members — Albert R. Buckelew, R. Todd Engstrom, and E. Dale Kennedy (terms expire 2005); Robert C. Beason, Mary Gustafson, and Timothy O’Connell (terms expire 2006); Mary Bomberger Brown, Robert L. Curry, and James R. Hill, III (terms expire 2007). Membership dues per calendar year are: Active, $21.00; Student, $15.00; Family, $25.00; Sustaining, $30.00; Life memberships $500 (payable in four installments). The Wilson Bulletin is sent to all members not in arrears for dues. THE JOSSELYN VAN TYNE MEMORIAL LIBRARY The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed in the Univ. of Michigan Museum of Zoology, was established in concurrence with the Univ. of Michigan in 1930. Until 1947 the Library was maintained entirely by gifts and bequests of books, reprints, and ornithological mag- azines from members and friends of the Society. Two members have generously established a fund for the purchase of new books; members and friends are invited to maintain the fund by regular contribution. The fund will be administered by the Library Committee. Terry L. Root, Univ. of Michigan, is Chairman of the Committee. The Library currently receives over 200 periodicals as gifts and in exchange for The Wilson Bulletin. For information on the library and our holdings, see the Society’s web page at http://www.ummz.lsa.umich.edu/birds/wos.html. With the usual exception of rare books, any item in the Library may be borrowed by members of the Society and will be sent prepaid (by the Univ. of Michigan) to any address in the United States, its possessions, or Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers, as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to: Josselyn Van Tyne Memorial Library, Museum of Zoology, The Univ. of Michigan, 1 109 Geddes Ave., Ann Arbor, MI 48109-1079, USA. Contributions to the New Book Fund should be sent to the Treasurer. THE WILSON BULLETIN (ISSN 0043-5643) THE WILSON BULLETIN (ISSN 0043-5643) is published quarterly in March, June, September, and December by the Wilson Ornithological Society, 810 East 10th St., Lawrence, KS 66044-8897. The subscription price, both in the United States and elsewhere, is $40.00 per year. Periodicals postage paid at Lawrence, KS. POSTMASTER; Send address changes to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. All articles and communications for publications, books and publications for reviews should be addressed to the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology, Ann Arbor, Michigan 48109. Subscriptions, changes of address and claims for undelivered copies should be sent to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. Phone: (254) 399-9636; e-mail: business@osnabirds.org. Back issues or single copies are avail- able for $12.00 each. Most back issues of the Bulletin are available and may be ordered from OSNA. Special prices will be quoted for quantity orders. All issues of The Wilson Bulletin published before 2000 are accessible on a free Web site at the Univ. of New Mexico library (http://elibrary.unm.edu/sora/). The site is fully searchable, and full-text reproduc- tions of all papers (including illustrations) are available as either PDF or DjVu files. © Copyright 2005 by the Wilson Ornithological Society Printed by Allen Press, Inc., Lawrence, Kansas 66044, U.S. A. 0 This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). MCZ library MAY 2 2005 , harvard UNIVERSITY FRONTISPIECE. Bicknell’s Thrush (Catharus hicknelli) in its favored high-elevation, coniferous-torest habitat in the northeastern United States. Lambert et al. mapped the distribution of BickneU’s Thrush based on then- model that predicts presence above an elevation threshold that decreases with increasing latitude. Original painting (acrylic and gouache) by Barry Kent MacKay. THE WILSON BULLETIN A QUARTERLY JOURNAL OL ORNITHOLOGY Published by the Wilson Ornithological Society VOL. 117, NO. 1 March 2005 PAGES 1-112 Wilson Bulletin 117(1): 1-11, 2005 A PRACTICAL MODEL OL BICKNELL’S THRUSH DISTRIBUTION IN THE NORTHEASTERN UNITED STATES J. DANIEL LAMBERT,>’3 KENT P. McFARLAND,^ CHRISTOPHER C. RIMMER,' STEVEN D. FACCIO,' AND JONATHAN L. ATWOOD^ ABSTRACT. Bicknell’s Thrush {Catharus hicknelli) is a rare habitat specialist that breeds in dense balsam fir {Abies balsamea) and red spruce (Picea rubens) forests at high elevations in the northeastern United States. Ongoing and projected loss of this forest type has led to increased demand for information on the species’ status throughout the region. We used elevation, latitude, and forest type to construct a model of Bicknell’s Thrush distribution in New York, Vermont, New Hampshire, and Maine. The model predicts the species to be present in coniter-dominated forests above an elevation threshold that descends with increasing latitude. The slope of the threshold (-81.63 m/l° latitude) reflects climatic effects on forest composition and structure. The distribution model encompasses 136,250 ha of montane forest, including extensive areas of the White Mountains in New Hampshire and Adirondack Mountains in New York. To test model performance, we conducted point count and playback surveys along 1-km routes established in conifer forests above and below the threshold. The model accurately predicted the presence or presumed absence of Bicknell’s Thrush on 61 of 72 routes (84.7%). When areas within 50 vertical m of the threshold were excluded, accuracy improved to 98.1%. The distribution model is a practical tool tor conservation planning at local and regional levels. Potential applications include projecting eftects of climate change on Bicknell’s Thrush distribution, assessing risks of habitat alteration, and setting priorities for conservation and management. Received 9 February 2004, accepted 20 December 2004. BicknelTs Thrush (Cathanis hicknelli), once considered a subspecies of Gray-cheeked Thrush (C. mininnis), gained full species sta- tus in 1995 (American Ornithologists’ Union 1995). It has since been considered one of the most “at-risk” passerines in eastern North America. Partners in Flight (Pashley et al. 2()()0) ranks Bicknell’s Thrush as the lop con- .servalion priority among Neotropical migrants in the Northeast, while the International Union for the Conservation of Nature (BirdLife In- ternational 2()()0) classifies the species as “vulnerable” on its list of threatened species. ' Vermont Inst, of Natural Science. 2723 (’lunch Mill Rd.. Woodstock. V'f 0509 1, USA. -Antioch New Ihigland (iraduate School. 40 Avon St., Keene. NH 03431-3552. VSA. ^ Corresponding author; e-mail: dlambertOiA insweb.org Although there is no conclusive evidence of widespread population declines, reports of re- gional declines (Rompre et al. 1999, Rimmer et al. 200 lb) and local extinctions (Christie 1993, Atwood et al. 1996, Nixon 1999, Lam- bert et al. 2001 ) have elevated concern for this rare species. BicknelTs Thrush is a habitat specialist that occupies a naturally fragmented breeding range from the Catskill Mountains of New York to the Gulf of St. Lawrence and Cape Breton Island, Nova Scotia (Atwood et al. 1996. Rimmer et al. 2001a). It is the region's only endemic bird species. In New ^’ork, northern New I-nglaiul, and the nearby listrie region of (Quebec. BickiicH's riimsh inhabits montane forests dominated by balsam fir (Abies balsamea), with lesser amounts of s|-)rucc (Picea rubens and P. mariana), white birch (lU’tula papyrijera \ar. cordifolia). and 1 2 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 mountain ash {Sorhus amehcana and S. de- cora) (Atwood et al. 1996, Rimmer et al. 2001a, Connolly et al. 2002). Structural attri- butes of Bicknell’s Thrush habitat include a dense understory of softwoods (Sabo 1980, Hale 2001, Pierce-Berrin 2001), low canopy height (Sabo 1980, Noon 1981, Hale 2001), and high incidence of snags, stumps, and dead fallen trees (Connolly 2000). These features typify chronically disturbed sites and regen- erating fir waves (Sprugel 1976). Favorable habitat conditions for Bicknell’s Thrush also may arise following disturbance by hurricane, ice storm, debris avalanche (Reiners and Lang 1979)^ or logging (Connolly 2000). Habitat suitability generally decreases with greater prominence of hardwoods (Sabo 1980, Noon 1981, Atwood et al. 1996, Hale 2001, Con- nolly et al. 2002); however, in the spruce-fir highlands of New Brunswick, BicknelTs Thrush inhabits both young conifer stands and regenerating hardwoods (Nixon 1996, Nixon et al. 2001). BicknelFs Thrush also occurs in maritime spruce-fir forests at sites scattered along both shores of the St. Lawrence Seaway (Gauthier and Aubry 1996) and throughout the Gulf of St. Lawrence (Nixon 1999). Locations in the Gulf include the western tip of Anticosti Is- land, the Magdalen Islands (Gauthier and Au- bry 1996), Cape Breton Island and small is- lands offshore of Cape Breton (Erskine 1992; D. Busby pers. comm.). Historic or sporadic records exist for several additional locations around the Bay of Fundy (Erskine 1992, Christie 1993). In the northeastern United States, climate change could greatly reduce or eliminate bal- sam fir habitat as growing conditions become more favorable for hardwood species (Iverson and Prasad 2002). Over the long term, a shift in forest composition may impair the viability of BicknelFs Thrush populations in the region. Meanwhile, ski area expansion, communica- tions tower construction, and wind power de- velopment incrementally reduce and fragment montane fir forests with unknown conse- quences for BicknelFs Thrush (Rimmer et al. 2001a). In order to conserve and properly manage remaining BicknelFs Thrush habitat, natural resource managers require reliable, site-specific occurrence information. Because it is not feasible to survey all potential habi- tats, a predictive habitat map is required for effective conservation planning. Wildlife habitat maps enable natural re- source managers to identify suitable habitat and predict effects of management alterna- tives. When constructed in a geographic in- formation systems (GIS) environment, such maps can be produced efficiently and applied consistently over large areas; however, the value of a GIS habitat model depends on its predictive capability. Therefore, model vali- dation is a critical step in the habitat mapping process. Validation procedures yield measures of model performance that provide a basis for determining appropriate applications to re- search and management. An accurate GIS model is a flexible tool that focuses limited resources where they will have the greatest effect. In a previous study, Atwood et al. (1996) identified forest type, latitude, and elevation as important factors underlying the distribu- tion of BicknelFs Thrush in New England and New York. The goal of our study was to con- struct and test a predictive distribution model that incorporates forest type and accounts for the effect of latitude on the elevational occur- rence of BicknelFs Thrush. METHODS To investigate the effect of latitude on the elevational occurrence of BicknelFs Thrush, we examined records from distribution sur- veys of BicknelFs Thrush conducted between 1992 and 1995. In these surveys, Atwood et al. (1996) surveyed 443 locations across a wide range of elevations (0 to 1,451 m) in New York, Vermont, New Hampshire, and Maine. We plotted the elevation and latitude of each survey location, including those where BicknelFs Thrush was detected {n = 234) and was not detected {n = 209). If multiple indi- viduals were observed during a survey, we plotted the lowest-elevation encounter. If no individuals were observed during a survey that spanned a range of elevations, we plotted the highest point surveyed. Next, we used the Quantreg library in R (http://lib.stat.cmu.edu/RyCRAN) to estimate the 0.05 quantile regression (Cade and Noon 2003) of elevation as a linear function of lat- itude for locations where BicknelFs Thrush was observed. This produced an elevation Lambert et al. • BICKNELL’S THRUSH DISTRIBUTION MODEL 3 threshold above which 95% of the detections occurred. We then converted the linear thresh- old into an elevation mask, formed as a raster data set of 30 X 30 m cells in ArcMap 8.2 (Environmental Systems Research Institute 2002). Cell values were calculated with the 0.05 quantile regression equation: elevation = -81.63(latitude) + 4,474.9 m. Next, we laid the elevation mask over a digital elevation model of the northeastern United States (U.S. Geological Survey 1999). Summits, ridge- lines, and slopes emerged above the mask as a vast complex of high-elevation habitat units. To identify potential BicknelTs Thrush habitat within these units, we mapped conifer-domi- nated stands. For this, we used forest com- position data from the National Land Cover Data set, which classifies 30 X 30 m cells based on canopy dominance (Vogelmann et al. 2001). To test model performance, we conducted surveys between 2000 and 2002 on 53 moun- tains (>800 m in elevation) not surveyed by Atwood et al. (1996). These mountains were scattered throughout the region and were se- lected based on availability of trails and vol- unteer observers. On each mountain, we es- tablished hve survey stations, separated by 200 to 250 horizontal m, in areas dominated by conifers. Routes were designed to include the highest forested areas accessible by trail, often the summit, as well as adjacent ridges and slopes. Where conifer cover was limited, we located survey stations in mixed forests. Trained technicians and volunteers per- formed point-count surveys under acceptable weather conditions (no precipitation, temper- ature >2° C, wind speed <32 km/hr) from 1 to 21 June. Surveys were conducted between 04:00 and 08:00 EDT, usually between 04:30 and 06:30. Observers listened quietly for 5 min, recording the number of Bicknell’s Thrushes seen or heard at each station. They also recorded BicknelTs Thrushes seen or heard along the route, between survey sta- tions. Observers who completed the route without detecting BicknelTs Thrush broadcast playbacks at each station on their way back to the starting point. Playbacks consisted of a 3- min, standardized recording of BicknelTs Thrush songs and call notes, followed by 2 min of silent listening. Playbacks were stopped upon first detection of the species. Observers who completed the playback sur- vey without encountering BicknelTs Thrush conducted follow-up, playback surveys at dusk or dawn before 15 July. This time, play- back stations were located at 100-m intervals along the route. If no observations of Bick- nelTs Thrush were made during the second visit to a given site, the species was presumed to be absent. Observers conducted the full sampling sequence (point counts and up to two playback surveys, as needed) in at least 1 of the 3 years. Follow-up playbacks were not conducted at six locations that were >80 m below the elevation mask. Atwood et al. (1996) surveyed 95 locations below this level without a confirmed encounter of BicknelTs Thrush. Observers reported incidental encounters with BicknelTs Thrushes on 19 additional mountains not previously surveyed. These ob- servations, made during one or more breeding seasons between 2000 and 2002, were added to the 53 original test routes for a total of 72 independent sample locations (New York: ti = 34, Vermont: n = 19, New Hampshire: n = 16, Maine: n = 3). Twenty-one of the 72 lo- cations were within 50 vertical m of the ele- vation mask. Also during 2000-2002, with the same combination of systematic surveys and incidental sightings, we recorded the presence or presumed absence of BicknelTs Thrush on 130 mountains hrst sampled by Atwood et al. (1996) (New York: n = 30, Vermont: n = 56, New Hampshire: n = 26, Maine: n = 18). Nineteen of 130 resampled locations occurred within 50 vertical m of the elevation mask. For model assessment, we used one elevation and one latitude value for each sample unit (1-km survey route or site of incidental en- counter). At locations where BicknelTs Thrush was present, we calculated average el- evation and latitude values based on all points of encounter. Where the species was not en- countered, we calculated averages from the five survey stations. We entered presence-absence data from new and resampled locations into separate er- ror matrices (Table 1 ) and calculated a variety of accuracy measures (after Tickling and Bell 1997), including correct classification rate, scnsitixily (proportion of true positi\es cor- rectly predicted), specificity (proportion of true negatives ccMTOctly predicted), false pos- 4 THE WILSON BULLETIN • Vol. J 17, No. 1, March 2005 TABLE 1. Error matrices for new Bicknell’s Thrush survey locations and for resampled locations (hrst surveyed by Atwood et al. 1996), from 20()()-2002 surveys. . Observed present Observed absent New locations Predicted present Predicted absent 56 1 Resampled locations Predicted present Predicted absent 1 14 1 10 5 5 10 itive rate, false negative rate, positive predie- tive power, and negative predietive power. We also ealculated prevalenee, the proportion of loeations at which Bicknell’s Thrush was pre- sent. This variable affects the predictive pow- er of species distribution models (Fielding and Bell 1997, Manel et al. 2001). Finally, we cal- culated Cohen’s kappa, a statistic that mea- sures the proportion of specific agreement af- ter accounting for prevalence. RESULTS Survey results from Atwood et al. (1996) show a strong, linear relationship between lat- itude and the lowest elevations occupied by Bicknell’s Thrush (Fig. 1). The lower limit of the species’ distribution, as estimated by the 0.05 quantile regression, descends 81 .63 m for every one-degree increase in latitude (p, = -81.63, 95% Cl = -112.08 to -38.13; Po = 4,474.86, 95% Cl = 729.50 to 5,753.27). The regression slope differed significantly from zero (Hq: (3i = 0) for this quantile (quantile rankscore test, P < 0.001). The elevation mask, developed in CIS from the 0.05 quantile regression, covers areas as high as 1,045 m in the Catskills (42° N). In northern Maine (46.3° N), areas as low as 695 m emerge above the mask. Throughout the re- gion, 720 distinct land units occur above the 42 43 44 45 46 47 48 Latitude (° N) LIG. 1. Elevation and latitude of locations where Bicknell’s Thrush (BITH) was detected (n 234) and not detected {n = 209) during 1992-1995 surveys in the northeastern United States. Line is 0.05 quantile regression estimate of elevation as a linear function of latitude, incorporating only locations where Bicknell’s Thrush was detected: elevation = —81.63 (latitude) + 4,474.9 m. Lambert et al. • BICKNELL’S THRUSH DISTRIBUTION MODEL 5 FIG. 2. Predicted distribution of Bicknell’s Thrush in the northeastern United States. Shaded areas represent conifer forests (Vogelmann et al. 2001) above the model’s elevation mask. mask and contain 1 36,250 ha of conifer-dom- inated forest (Fig. 2), nearly all of which (99.7%) occurs in 387 units containing at least 5 ha of conifer — an amount sufficient to con- tain the average home range of a male Bick- nell’s Thrush (4.5 ha; Rimmer et al. 2001a). The average extent of conifer forest within the 387 units is 351.0 ha ± 56.8 SE, with highest values occurring in the White Mountains of New Hampshire and in the High Peaks region ol New York’s Adirondack Mountains. Of all states. New Hampshire has the most potential Bicknell’s Thrush breeding habitat (59,024 ha; 43.4%), followed by Maine (33,662 ha; 24.7%), New York (31,985 ha; 23.5%), and Vermont (1 1,580 ha; 8.5%). The BicknelTs Thrush distribution model correctly classified 61 of 72 locations (84.7%) that had never been surveyed for this species (Fig. 3, Table 2). Fifty-six of 57 occupied lo- cations (98.2%) were correctly classified, compared with just 5 out of 15 (33.3%) un- occupied locations. Locations within 50 ver- tical m of the elevation mask accounted for both errors of omission (false negatives) and 9 out of 10 errors of commission (false posi- tives). The average, vertical deviation of mis- classified locations from the elevation mask was 28.2 m ± 5.2 SE. When the 21 locations within 50 m of the elevation mask were ex- cluded from the analysis, 51 of 52 locations (98.1%) were correctly classified. The model correctly classified 124 of 130 locations (95.4%) first surveyed by Atwood et al. (1996). Four of the six errors occurred within 50 m of the elevation mask. When all new (/? = 72) and resampled (// = 130) sites were combined, the model correctly classified 185 ol 202 (91.6%) locations. Classification accuracy >50 m above and below the eleva- tion mask was 98.8%r. with 160 of 162 loca- tions correctly classified. Prevalence ol BicknelTs Thrush was high among new locations (0.792) and resampled locations (0.877; Table 2). Cohen's kappa, which accounts for |')revalence. measured 6 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 EIG. 3. Elevation and latitude of locations where Bicknell’s Thrush (BITH) was detected {n 172) and not detected {n = 30) during 2000-20002 surveys in the northeastern United States, shown in relation to elevation mask. Large circles represent new survey locations {n = 72); small circles represent locations first surveyed by Atwood et al. (1996) and resampled for this study {n = 130). 0.405 among new routes and 0.745 among re- sampled routes. Values of 0.4-0. 6 indicate moderate model performance. Higher values (up to 1.0) are achieved when model perfor- mance ranges from substantial to perfect (after Landis and Koch 1977). TABLE 2. Accuracy measures for Bicknell’s Thrush distribution model. Values are calculated after Eielding and Bell (1997) with data from 72 new lo- cations and from 130 (resampled) locations (2000- 2002) first surveyed by Atwood et al. (1996). New Resampled locations locations Correct classification rate 0.847 0.954 Sensitivity 0.982 0.991 Specificity 0.333 0.667 Ealse positive rate^ 0.667 0.333 Ealse negative rate'" 0.018 0.009 Positive predictive power 0.848 0.958 Negative predictive power 0.833 0.909 Prevalence 0.792 0.877 Kappa 0.405 0.745 ^ Rate of commission error. Rate of omission error. DISCUSSION The slope of the latitude-elevation relation- ship for Bicknell’s Thrush occurrence (-81.63 m/l° latitude) is nearly identical to the lati- tude-elevation relationship for treeline in the northern Appalachian Mountains (-83 m/l° latitude); it also resembles that of the spruce- fir/deciduous forest ecotone (—100 m/l° lati- tude; Cogbill and White 1991). The similarity in these slopes and the known association of Bicknell’s Thrush with naturally disturbed for- est stands suggest that the same factors gov- erning stratification of mountain forest types regulate the availability of suitable habitat for Bicknell’s Thrush. On a local scale, these in- clude topography (slope shape, slope position, steepness, and aspect), substrate, and distur- bance (Cogbill and White 1991). At regional and continental scales, temperature appears to be the primary, controlling factor (Wolfe 1979). Cogbill and White (1991) found that the lower and upper spruce-fir ecotones were cor- related with mean July temperatures of ap- Lambert et al. • BICKNELL’S THRUSH DISTRIBUTION MODEL 7 proximately 17° C and 13° C, respectively. If a warming climate were to elevate these iso- therms, an upslope advance of hardwoods, and a corresponding loss of Bicknell’s Thrush habitat might be expected. Tree-species distri- bution models project a major loss or extir- pation of balsam fir habitat from the Northeast in four out of five climate change scenarios (Iverson and Prasad 2002). However, damage to hardwoods from ice- and snow-loading could moderate effects of climate change on forest composition at high elevations. The bal- sam fir’s conical form allows it to shed snow more effectively than broad-branching hard- woods (Nykanen et al. 1997). Steep slopes might also provide refugia for balsam fir, which readily establishes in shallow, mineral soils (Frank 1990). Nevertheless, the persis- tence of Bicknell’s Thrush in the Northeast may depend upon its ability to adapt to chang- ing forest conditions. A warming climate could enable mountain- top encroachment from species believed to be restricted to lower elevations by colder tem- peratures, including both a potential compet- itor of Bicknell’s Thrush and a known pest of balsam fir. Swainson’s Thrush (Catharus us- tulatus) is a potential competitor (Noon 1981) whose distribution overlaps the lower reaches of Bicknell’s Thrush habitat (Able and Noon 1976). A rise in summer temperatures could reduce separation between the two species by nullifying Bicknell’s Thrush’s greater toler- ance for cold, considered by Holmes and Saw- yer (1975) to confer a thermoregulatory ad- vantage. Balsam woolly adelgid {Adelges pi- cecie) is an exotic pest introduced from central Europe. It is currently controlled in the North- east by cold winter temperatures, but has dec- imated stands of balsam fir in the southern Appalachians (Iverson et al. 1999). The mechanisms by which a warming cli- mate might affect Neotropical migrants are numerous and largely unpredictable, although even small changes could have far-reaching effects on productivity and survivorship (Ro- denhouse 1992). Susceptibility to extinction is high for species like BicknelTs 'fhrush that occupy restricted and patchy habitat within small ranges (Huntley et al. 1997). In recent decades, extirpations of BicknelTs Thrush have occurred at coastal locations in C'anatla (Tufts 1986, Christie 1993, Nixon 1999) and along the southern periphery of the species’ breeding range (Atwood et al. 1996, Lambert et al. 2001). Although there is no evidence for a link to climate change, the observed pattern is consistent with range shifts attributed to global warming in other animal species (Par- mesan and Yohe 2003, Root et al. 2003). Our model of BicknelTs Thrush habitat provides the opportunity to predict changes in the spe- cies’ distribution under different climatic con- ditions. Information gained through this ex- ercise might be used to develop strategies to mitigate anticipated habitat loss. Overall, the distribution model achieved high measures of classification accuracy, pos- itive predictive power, and negative predictive power (Table 2). However, such levels can be achieved by chance alone where the preva- lence of a species is high (Olden et al. 2002), as it was in this study. Cohen’s kappa provides a measure of improvement over chance that places prediction success in perspective (Fielding and Bell 1997, Manel et al. 2001). The kappa values we calculated for new routes (0.406) and resampled routes (0.745) correspond with moderate and substantial model performance, respectively. An im- proved test of the model, including low and middle elevations, would almost certainly yield higher kappa values because more lo- cations would be correctly classified as un- occupied. By concentrating sampling effort at high elevations, we limited the interpretive value of this statistic. The model’s predictive success was nearly perfect at locations >50 m above or below the elevation mask (Fig. 3). By comparison, error rates were high within 50 m of the mask, where hardwoods become scarce and conifers achieve dominance. Able and Noon (1976) described this band as a principal distribution- al limit for songbirds on northeastern moun- tains and measured its breadth as approxi- mately 100 m in the Adirondack and Green mountains. Cogbill and White (1991) pro\ id- ed a similar measure (87 m) for the average breadth of the decitluous rorest/spruce-lir eco- tone in the Adirondack and northern Apjiala- chian mountains. Our liiulings are consistent with these measures and \erit'y this boundarv as an important I'actor in organi/ing a\ ian community structure across four degrees ot latitikle. 8 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 Low densities of Bicknell’s Thrush may have resulted in reduced detectability at some locations, particularly during silent counts (Penteriani et al. 2002). Even playbacks can fail to elicit detectable responses from Bick- nelLs Thrush (Nixon et al. 2001), which may exhibit agonistic postures in dense vegetation rather than vocalize (Noon 1981). Indeed, the failure to detect Bicknell’s Thrush at many ap- parently suitable sites during the 1990s may indicate sampling error. Such error could have resulted from limited sampling (a single visit to 80 locations) and a relatively loose time- frame for broadcasts (“usually within three hours of sunrise or sunset”; Atwood et al. 1996). The possibility of error during model testing (2000-2002) was reduced by multiple visits and strict broadcast guidelines. The higher frequency of detection above the ele- vation mask, compared with the results of At- wood et al. (1996), provides evidence of im- proved methodology. Accuracy rates vary widely among habitat- relationship models that have been tested for songbirds (e.g., 20-33%, Bart et al. 1984; 60- 90%, Rice et al. 1986; 53-93%, Kilgo et al. 2002). Models constructed for habitat special- ists are more likely to generate accurate pre- dictions than those developed for generalists (Kilgo et al. 2002). This presents conservation planning opportunities for rare species with narrow habitat requirements, like BicknelLs Thrush. Our model of BicknelLs Thrush dis- tribution can be used as a practical tool to guide research, stewardship, and land protec- tion initiatives in the mountains of New York and northern New England. Specific applica- tions include: identification of monitoring and research sites, reserve design, recreational planning, regulatory review and impact as- sessment (as for tower construction or ski area expansion), and assignment of management responsibility to specific landowners. To evaluate tradeoffs in each of these ap- plications, it is important to consider the sig- nificance of model error. In general, excessive commission error may result in undue expen- diture of limited resources at marginal sites, while excessive omission error may result in failure to identify important, occupied sites. Fortunately, GIS provides the flexibility to ad- just the BicknelLs Thrush elevation mask to achieve an acceptable ratio between these two types of error. Such adjustments can be made according to project resources and objectives. For example, a risk-averse strategy to protect BicknelLs Thrush habitat might lower the el- evation mask to identify all potential breeding areas, including those along the lower spruce- fir ecotone. Though sparsely populated by BicknelLs Thrush, this zone is extensive in mountainous landscapes and could contribute substantially to overall numbers (Hale 2001). A research initiative seeking to maximize en- counters with the species might take a more selective approach and raise the mask. For projects that seek information on the status of BicknelLs Thrush at sites within 50 m of the elevation mask, we recommend the use of playback surveys in June and early July. Six or more visits may be required to detect all individuals in a given year (Nixon et al. 2001). If initial attempts to verify pres- ence fail, additional effort is advised in at least 2 successive years or until presence is con- firmed. Repeat surveys will reduce errors as- sociated with low density (i.e., low detect- ability) and irregular occupancy of marginal sites. Our own repeat surveys confirm their value. Since 2003, we have observed Bick- nelLs Thrush at 6 of 15 locations where it was predicted to occur, but was not detected during model assessment (Vermont Institute of Nat- ural Science [VINS] unpubl. data). The model’s estimate of BicknelLs Thrush habitat in the Northeast (136,250 ha) falls within the previously published range of val- ues derived from land cover and land area above the 915-m contour line (100,000 to 150,000 ha; Atwood et al. 1996). However, the addition of latitude as a variable eliminates areas in southern portions of the range once thought suitable for BicknelLs Thrush and adds sites at northern latitudes once consid- ered too low. Despite this important advance, the model does not distinguish early- to mid- successional or stunted forests from tall stands, which are of lesser importance to the species. Extensive surveys (Noon 1981, Hale 2001; VINS unpubl. data) and intensive, ra- dio-telemetry studies (VINS unpubl. data) in- dicate that BicknelLs Thrushes make little use of large patches of mature, montane conifer that lack well-developed shrub and subcanopy layers. Nonetheless, such stands may be just an ice storm, fir wave, or hurricane away from Lambert et al. • BICKNELL’S THRUSH DISTRIBUTION MODEL 9 developing the structural characteristics of suitable habitat. Likewise, the habitat value of a young forest sheltered from disturbance may diminish over time. Conservation and mitigation strategies should recognize that the location of suitable habitat patches shifts due to the dynamic na- ture of forests at high elevations. Rather than focus at the stand level, a prudent long-range approach would treat the entire unmasked area as the management unit. Such an approach would benefit other species that nest in mon- tane forests of the Northeast, such as Black- backed Woodpecker {Picoides arcticus). Yel- low-bellied Flycatcher {Empidonax ficiviven- tris), Blackpoll Warbler (Dendroica striata), and White-winged Crossbill {Loxia leucop- tera). We advise caution in the application of this model north of 45° N latitude. Unmasked ar- eas in this region include >40,000 ha of man- aged timberland in Maine (VINS unpubl. data), some of which occurs as mixed, regen- erating forest. The Canadian Wildlife Service has documented use of this forest type by breeding Bicknell’s Thrushes in highland re- gions of Quebec (Y. Aubry pers. comm.). New Brunswick (Nixon 1996), and Nova Scotia (D. Busby pers. comm.). Furthermore, model test- ing in northern Maine was limited, allowing for the possibility that BicknelFs Thrush oc- curs at lower elevations than predicted by the model. Such a possibility is supported by Wolfe’s (1979) treeline model, which slopes gradually from 20° N to about 45° N and then begins to steepen. Cogbill and White’s (1991) models of Appalachian Mountain ecotones maintain their linear shape until about 47° N, where the relationship between elevation and the spruce-fir/deciduous ecotone changes to a steeper slope. Records of Bicknell’s Thrush at low elevations in Quebec (175-1,160 m; Ouellet 1993), New Brunswick (450-700 m; Nixon et al. 2001), and Nova Scotia (<175 m; D. Busby pers. comm.) underscore the need for further model testing in northern Maine. The absence of evaluation sites below the mask in the Catskills (42.0-42.5° N) is of less concern. We are eonlident that the model is sufficiently inclusive in this area, since it cap- tures virtually all of the region's ui^land spruce- fir. Recently developed and evolving modeling techniques will enable construction of region- al models of habitat importance for BicknelFs Thrush, based on topographic and lithographic features (Banner 2002), remotely sensed for- est physiognomy (Hale 2001), and/or land- scape structure (Hale 2001, Lambert et al. 2002). Incorporation of abundance data into more sophisticated models will permit reason- able estimates of population size and provide a benchmark for establishing range-wide pop- ulation objectives. However, construction and validation of such models will require consid- erable time and resources. Though basic in its parameters and predictions, the current model is accurate and effective for most applications. It is built from elevation and land cover data that are widely available, inexpensive, consis- tent across state boundaries, and easily updat- ed. Furthermore, it depicts habitat over a ma- jor portion of the species’ range. Together, these qualities make it a practical tool for con- servation planning. ACKNOWLEDGMENTS We thank the scores of dedicated volunteers who helped with fieldwork. They were recruited with assis- tance from the Adirondack Mountain Club, Appala- chian Mountain Club, Audubon New York, Green Mountain Club, Maine Department of Inland Fisheries and Wildlife, Wildlife Conservation Society, and Won- alancet Outdoor Club. We also thank our research as- sistants; N. K. Banfield, C. R Dugan. M. Gaige. C. Rabatin, and S. A. Schulte. We are grateful for site access provided by the Carthusian Monastery. Essex Timber Company, Green Mountain Club. Maine De- partment of Environmental Conservation. Maine De- partment of Inland Fisheries and Wildlife, National Park Service, New York State Department of Environ- mental Conservation. The Nature Conser\ ancy, Stowe Mountain Resort. Stratton Mountain Resort. IkS. R'or- est Service, University of Vermont, and Vermont Agency of Natural Resources. We thank the New '^\)rk State Breeding Bird Atlas for sharing BickneH’s Thrush site records. .1. D. Schlagel and A. roeplei pro- vided technical assistance with the habitat model. We are grateful to B. S. (\ule for coiulucting the ciuantile regression analysis. We also thank I). Busby. IE .S. C’aiie. J. If Goet/. .S. K. Hale. .1. .lones. K. Kenirew. C. A. kibic. and an anonymous re\iewer for helpful comments on etirlier drafts of the manuscript, l uiuling for this iiroject was pro\ iikxl by the U..S. l ish aiul Wikllile Scr\ ice. with aiklitional support tidin the trustees ;md members ol the Vermont Institute of Nat- ural Science. 10 THE WILSON BULLETIN • VoL 117, No. I, March 2005 LITERATURE CITED Able, K. P. and B. R. Noon. 1976. Avian community structure along elevational gradients in the north- eastern United States. Oecologia 26:275-294. American Ornithologists’ Union. 1995. Fortieth sup- plement to the American Ornithologists’ Union check-list of North American birds. Auk 1 12:819- 830. Atwood, J. L., C. C. Rimmer, K. P. McFarland, S. H. Tsai, and L. R. Nagy. 1996. Distribution of Bicknell’s Thrush in New England and New York. Wilson Bulletin 108:650-661. Banner, A. 2002. Cookbook: methods for mapping fish and wildlife habitat in multi-state study areas in USFWS Region 5. Unpublished report, U.S. Fish and Wildlife Service, Falmouth, Maine. Bart, J., D. R. Petit, and G. Linscombe. 1984. Field evaluation of two models developed following the habitat evaluation procedures. Transactions of the North American Wildlife and Natural Resources Conference 49:489—499. BirdLiee International. 2000. Threatened birds of the world. BirdLife International, Cambridge, United Kingdom and Lynx Edicions, Barcelona, Spain. Cade, B. S. and B. R. Noon. 2003. A gentle intro- duction to quantile regression for ecologists. Fron- tiers in Ecology and the Environment 1:412-420. Christie, D. S. 1993. Survey of breeding birds in Fun- dy National Park, 1992. Contract Report, no. FNP92-004, Canadian Parks Service, Alma, New Brunswick. COGBILL, C. V. AND P. S. WHITE. 1991. The latitude- elevation relationship for spruce-fir forest and treeline along the Appalachian Mountain chain. Vegetatio 94:153-175. Connolly, V. 2000. Characterization and classification of Bicknell’s Thrush {Catharus bicknelli) habitat in the Estrie region. M.Sc. thesis, McGill Univer- sity, Montreal, Canada. Connolly, V., G. Seutin, J.-P. L. Savard, and G. Rompre. 2002. Habitat use by Bicknell’s Thrush in the Estrie Region, Quebec. Wilson Bulletin 114:333-341. Environmental Systems Research Institute. 2002. ArcMap GIS, ver. 8.2. Environmental Systems Research Institute, Inc., Redlands, California. Erskine, a. j. 1992. Atlas of the breeding birds of the Maritime provinces. Nova Scotia Museum, Hali- fax, Canada. Fielding, A. H. and J. F. Bell. 1997. A review of methods for the assessment of prediction errors in conservation presence/absence models. Environ- mental Conservation 24:38—49. Frank, R. M. 1990. Abies balsamea (L.) Mill., balsam fir. Pages 26-35 in Silvics of North America, vol. 1: conifers (R. M. Burns and B. H. Honkala, Tech. Coords.). Agriculture Handbook, no. 654, USDA Forest Service, Washington, D.C. Gauthier, J. and Y. Aubry (Eds.). 1996. The breeding birds of Quebec. Province of Quebec Society for the Protection of Birds and the Canadian Wildlife Service, Quebec Region, Montreal, Canada. Hale, S. R. 2001. Using satellite remote sensing to model and map the distribution of Bicknell’s Thrush {Catharus bicknelli) in the White Moun- tains of New Hampshire. Ph.D. dissertation. Uni- versity of New Hampshire, Durham. Holmes, R. T. and R. H. Sawyer. 1975. Oxygen con- sumption in relation to ambient temperature in five species of forest-dwelling thrushes {Hylocich- la and Catharus). Comparative Biochemistry and Physiology 50A:527-531. Huntley, B., W. P. Cramer, A. V. Morgan, H. C. Prentice, and J. R. M. Allen. (Eds.). 1997. Past and future rapid environmental changes: the spa- tial and evolutionary responses of terrestrial biota. Springer- Verlag, Berlin, Germany. Iverson, L. R. and A. M. Prasad. 2002. Potential re- distribution of tree species habitat under five cli- mate ehange scenarios in the eastern U.S. Forest Ecology and Management 155:205-222. Iverson, L. R., A. M. Prasad, B. J. Hale, and E. K. Sutherland. 1999. Atlas of current and potential future distributions of common trees of the eastern United States. General Technical Report NE-265, USDA Forest Service, Northeastern Research Sta- tion, Radnor, Pennsylvania. Kilgo, j. C., D. L. Gartner, B. R. Chapman, J. B. Dunning, Jr., K. E. Franzreb, S. A. Gauth- REAUX, C. H. Greenberg, D. J. Levey, K. V. Miller, and S. F. Pearson. 2002. A test of an expert-based bird-habitat relationship model in South Carolina. Wildlife Society Bulletin 30:783- 793. Lambert, J. D., S. D. Faccio, and B. Hanscom. 2002. Mountain birdwatch: 2001 final report to the U.S. Fish and Wildlife Service. Unpublished report, Ver- mont Institute of Natural Science, Woodstock, Ver- mont, w ww. vins web.org/assets/pdf/200 1 report.pdf. Lambert, J. D., K. P. McFarland, C. C. Rimmer, and S. D. Faccio. 2001. Mountain birdwatch 2000: fi- nal report to the U.S. Fish and Wildlife Service. Unpublished report, Vermont Institute of Natural Science, Woodstock, Vermont, www.vinsweb.org/ assets/pdf/2000report.pdf. Landis, J. R. and G. G. Koch. 1977. The measurement of observer agreement for categorical data. Bio- metrics 33:159-174. Manel, S., H. C. Williams, and S. J. Ormerod. 2001. Evaluating presence-absence models in ecology: the need to account for prevalence. Journal of Ap- plied Ecology 38:921-931. Nixon, E. A. 1996. A distribution survey of Bicknell’s Thrush {Catharus bicknelli) in New Brunswick. Unpublished report, Canadian Wildlife Service and Canadian Forest Service, Sackville, New Brunswick and Sault Ste. Marie, Ontario, Canada. Nixon, E. A. 1999. Status report on Bicknell’s Thrush {Catharus bicknelli) in Canada. Unpublished re- port, Environment Canada, Ottawa, Canada. Lambert et al. • BICKNELL’S THRUSH DISTRIBUTION MODEL 11 Nixon, E. A., S. B. Holmes, and A. W. Diamond. 2001. Bicknell’s Thrushes (Catharus bicknelli) in New Brunswick clear cuts: their habitat associa- tions and co-occurrence with Swainson’s Thrushes {Catharus iistiilatiis). Wilson Bulletin 113:33-40. Noon, B. R. 1981. The distribution of an avian guild along a temperate elevational gradient: the impor- tance and expression of competition. Ecological Monographs 51:105-124. Nykanen, M.-L., H. Peltola, C. Quine, S. Kello- MAKi, AND M. Broadgate. 1997. Factors affecting snow damage of trees with particular reference to European conditions. Silva Fennica 31:193-213. Olden, J. D., D. A. Jackson, and P. R. Peres-Neto. 2002. Predictive models of fish species distribu- tions: a note on proper validation and chance pre- dictions. Transactions of the American Fisheries Society 131:329-336. OuELLET, H. 1993. Bicknell’s Thrush: taxonomic status and distribution. Wilson Bulletin 105:545-572. Parmesan, C. and G. Yohe. 2003. A globally coherent fingerprint of climate change impacts across nat- ural systems. Nature 421:37-42. Pashley, D. N., C. J. Beardmore, J. A. Fitzgerald, R. P. Ford, W. C. Hunter, M. S. Morrison, and K. V. Rosenberg. 2000. Partners in Flight: con- servation of the land birds of the United States. American Bird Conservancy, The Plains, Virginia. Penteriani, V., M. Gallardo, and H. Cazassus. 2002. Conspecific density biases passive auditory surveys. Journal of Field Ornithology 73:387- 391. Pierce-Berrin, C. 2001. Distribution and habitat se- lection of Bicknell’s Thrush {Catharus bicknelli) in the Catskill Mountains of New York State. M.Sc. thesis, Antioch New England Graduate School, Keene, New Hampshire. Reiners, W. A. and G. E. Lang. 1979. Vegetational patterns and processes in the balsam fir zone. White Mountains, New Hampshire. Ecology 60: 403-417. Rice, J. C., R. D. Ohmart, and B. W. Anderson. 1986. Limits in a data-rich model: model experi- ence with habitat management on the Colorado River. Pages 79-86 in Wildlife 2000: modeling habitat relationships of terrestrial vertebrates (J. Verner, M. L. Morrison, and C. J. Ralph, Eds.). University of Wisconsin Press, Madison. Rimmer, C. C., K. P. McFarland, W. G. Ellison, and J. E. Goetz. 2001a. Bicknell’s Thrush {Catharus bicknelli). The Birds of North America, no. 592. Rimmer, C. C., K. P. McFarland, and J. D. Lambert. 2001b. Bicknell’s Thrush {Catharus bicknelli) conservation assessment. Unpublished report, Vermont Institute of Natural Science, Woodstock, Vermont. Rodenhouse, N. L. 1992. Potential effects of climatic change on a Neotropical migrant landbird. Con- servation Biology 6:263-272. Rompre, G., V. Connolly, Y. Aubry, J.-P. Savard, AND G. Seutin. 1999. Repartition, abondance et preferences ecologiques de la Grive de Bicknell {Catharus bicknelli) au Quebec. Rapport tech- nique, Service Canadien de la Faune, Quebec, Canada. Root, T. L., J. T. Price, K. R. Hall, S. H. Schneider, C. Rosenzweig, and j. A. Pounds. 2003. Finger- prints of global warming on wild animals and plants. Nature 421:57-60. Sabo, S. R. 1980. Niche and habitat relations in sub- alpine bird communities of the White Mountains of New Hampshire. Ecological Monographs 50: 241-259. Sprugel, D. G. 1976. Dynamic structure of wave-re- generated Abies balsamea forests in the north- eastern United States. Journal of Ecology 64:889- 911. Tufts, R. W. 1986. Birds of Nova Scotia, 3rd ed. Nova Scotia Museum, Halifax, Canada. U.S. Geological Survey. 1999. National elevation dataset. Earth Science Information Center, Sioux Falls, South Dakota. VOGELMANN, J. E., S. M. HOWARD, L. YaNG, C. R. Larson, B. K. Wylie, and N. Van Driel. 2001. Completion of the 1990s National Land Cover Data set for the conterminous United States from Landsat Thematic Mapper data and ancillary data sources. Photogrammetric Engineering and Re- mote Sensing 67:650-662. Wolfe, J. A. 1979. Temperature parameters of humid to mesic forests of eastern Asia and relation to forests of other regions of the Northern Hemi- sphere and Australasia. Geological Survey Profes- sional Paper, no. I 106, U.S. Geological Sur\ey, Washington, D.C. Wilson Bulletin 1 17(1): 12-1 4, 2005 OFFSHORE MARINE OBSERVATION OE WILLOW PTARMIGAN, INCLUDING WATER LANDINGS, KUSKOKWIM BAY, ALASKA CHRISTIAN E. ZIMMERMAN,'-^ NICOLA HILLGRUBER,^ SEAN E. BURRIL,^ MICHELLE A. ST PETERS,' AND JENNIEER D. WETZEL' ABSTRACT. — We report an observation of Willow Ptarmigan {Lagopiis lagopus) encountered 8 to 17 km from the nearest shoreline on Kuskokwim Bay, Alaska, on 30 August 2003. The ptarmigan were observed flying, landing on our research vessel, and landing and taking off from the water surface. We also report on one other observation of ptarmigan sitting on the water surface and other marine observations of ptarmigan from the North Pacific Pelagic Seabird Database. These observations provide evidence that Willow Ptarmigan are capable of dispersing across large bodies of water and landing and taking off from the water surface. Received 19 July 2004, accepted 4 January 2005. Willow Ptarmigan {Lagopus lagopus) have a Holarctic distribution and are found throughout much of Alaska, typically occu- pying alpine and arctic tundra (Hannon et al. 1998). In contrast to the residential habits of most other grouse species (Gruys 1993, Han- non et al. 1998), Willow Ptarmigan are known to make seasonal migrations that may cover distances of several hundred kilometers. Al- though their wing morphology and muscle composition suggest that they are better adapt- ed to longer migrations and sustained flight than other galliforms (Drovetski 1996), galli- forms generally are considered to have limited ability for sustained flight (Tobalske et al. 2003). For Willow Ptarmigan, migration be- tween breeding and wintering habitats typi- cally occurs in early fall, with return migra- tion occurring in spring (Hannon et al. 1998); Gruys (1993) reported that Willow Ptarmigan migrating from summer to winter habitats moved in flocks of up to 200 birds. Ptarmigan, upland birds not commonly associated with water, normally do not swim or dive (Hannon et al. 1998), but Dixon (1927) observed a Wil- low Ptarmigan wade into shallow creek water to forage on insects, and Hannon et al. (1998) report that 1 -day-old chicks can swim if they fall into water. Because ptarmigan are not usually associ- ' U.S. Geological Survey, Alaska Science Center, 1011 E. Tudor Rd., Anchorage, AK 99503, USA. 2 Univ. of Alaska Fairbanks, School of Fisheries and Ocean Sciences, 11120 Glacier Hwy., Juneau, AK 99801, USA. ^ Corresponding author; e-mail: czimmerman@usgs.gov ated with water and generally exhibit limited flight endurance, it is not clear whether ptar- migan would be able to migrate long distances over bodies of water. Determining the extent of this ability may be a key element to un- derstanding dispersal patterns and population structure. Rock Ptarmigan (L. muta) breeding on the Aleutian Islands, for example, are char- acterized by genetic divergence among major island groups with little gene flow between island populations (Holder et al. 2000, 2004). Holder et al. (2000) further pointed out that no inter-island movement of individual ptar- migan has ever been reported, although the distances between islands are often less than those covered by migrations of inland ptar- migan. On 30 August 2003, during a survey for pelagic juvenile salmon in Kuskokwim Bay, Alaska (60° 0' N, 162° 15' W), we encoun- tered a group of 100 to 125 Willow Ptarmi- gan. We observed the ptarmigan for approxi- mately 2 hr (08:00 to 10:00 Alaska Standard Time) as we cruised south along the 162° 16' W longitude line. We first encountered the ptarmigan when we were approximately 8 km from shore. Our track was roughly parallel to the east coast of Kuskokwim Bay and distance to shore ranged from 8 to 17 km. Initially, two ptarmigan (a female and male) landed on our vessel and rested for approximately an hour before flying away. Over the next hour (09:00-10:00), approximately 125 birds re- peatedly flew around the vessel. A few landed on the vessel and rested for short periods (<15 min) before flying off in the distance and returning to the vicinity of the boat (Fig. 12 Zimmerman et al. • PTARMIGAN AT SEA 13 F’lG. 1. Willow Ptarmigan in flight, on a research vessel, and on the water, Kuskokwim Bay, Alaska, 30 August 2003. See additional photographs at www. absc.usgs.gov/research/Fisheries/Western_Alaska/ ptarmigan.htm. I ). All birds appeared to be exhausted after landing on the vessel, exhibiting rapid breath- ing with open beaks. At least 10 ptarmigan were observed landing on the wtiter sui laee, resting (<1() min), then taking off from the water surfaee. When we encountered the ptar- migan, the sea was calm, winds were light, and the sky was overcast. The nearest weather station, at Cape Newenham on the southern boundary of Kuskokwim Bay and approxi- mately 120 km from our location, reported calm winds, visibility of 16 km, and an air temperature of 13° C (Federal Aviation Ad- ministration automated weather monitoring station). To determine whether other ptarmigan had been observed at sea or landing on water, we queried the North Pacihe Pelagic Seabird Da- tabase (www.absc.usgs.gov/research/NPPSD/), which contains pelagic seabird survey data collected over the last 30 years in the North Pacific Ocean, Bering Sea, and adjacent wa- ters. Of 57 ptarmigan records — including 16 Willow Ptarmigan, 6 Rock Ptarmigan, and 35 unidentified ptarmigan — all were associated with shorelines of the Chuckchi Sea, Arctic Ocean, or Norton Sound, Alaska. Only 1 ptar- migan was sitting on the water, 12 were not classified according to behavior, 12 were fly- ing in a consistent heading, 9 were flying be- low the crests of waves or swells (suggesting flight over water), 2 were bathing, 15 exhib- ited courtship behavior (likely terrestrial ob- servations), and 6 were sitting or standing fol- lowed by flushing (likely terrestrial observa- tions). Of the behaviors reported, 12 appear to have been associated with water, including sit- ting on water, bathing, or flying below wave crests. The single record of a ptarmigan sitting on the water was of a Rock Ptarmigan ob- served on 26 June 1976 at Kasegaluk Lagoon (68° 5 1 ' N, 165° 50' W), adjacent to the Chuk- chi Sea. It is not clear why the ptarmigan we ob- served on Kuskokwim Bay were Hying off- shore. Since the weather was calm at the time and had been so for several days, it is unlikely that this group had been displaced by wind. Willow Ptarmigan are common on the coastal plain adjacent to Kuskokwim Bay and typi- cally migrate in September — from the coastal plain to mountains in the east (approximately 90 km; M. Rearden i^eis. comm.). It seems likely that the ptarmigan we encountered had gathered as they migriited from breeding hab- itats on the coastal plain to wintering habitats. (liven the distribution of ptarmigan on off- shore islands, such as the Aleutian Islands, Alaska, it is not unlikely that dispersal occurs 14 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 over water. Understanding the dispersal ca- pabilities and patterns of animals is a critical step in examining population structure and metapopulation dynamics (Weins 1996). Dis- persal among islands is regulated by the dis- persal capabilities of a species and the dis- tance between islands. Our observation of Willow Ptarmigan on Kuskokwim Bay and the observation of Rock Ptarmigan at Kase- galuk Lagoon are the first records of ptarmi- gan not only landing and sitting on the water surface, but also successfully taking off after resting on the water surface. These observa- tions add to our understanding of dispersal by ptarmigan and may provide insight concern- ing dispersal of ptarmigan across large bodies of water. ACKNOWLEDGMENTS We thank Captain J. Peacock of the research vessel Eileen O’Earrell. J. E Piatt encouraged us to publish our unusual observation. Eunding for the Kuskokwim Bay juvenile salmon research is provided by the North Pacific Research Board; the North Pacific Pelagic Sea- bird Database is funded by the North Pacific Marine Research Institute. We thank three anonymous review- ers for comments on an earlier draft. LITERATURE CITED Dixon, J. 1927. Contribution to the life history of the Alaska Willow Ptarmigan. Condor 29:213-223. Drovetski, S. V. 1996. Influence of the trailing-edge notch on flight performance of galliforms Auk 1 13:802-810. Gruys, R. C. 1993. Autumn and winter movements and sexual segregation of Willow Ptarmigan. Arc- tic 46:228-239. Hannon, S. J., P. K. Eason, and K. Martin. 1998. Willow Ptarmigan (Lagopus lagopus). The Birds of North America, no. 369. Holder, K., R. Montgomerie, and V. L. Friesen. 2000. Glacial vicariance and historical biogeog- raphy of Rock Ptarmigan {Lagopus mutiis) in the Bering region. Molecular Ecology 9:1265-1278. Holder, K., R. Montgomerie, and V. L. Friesen. 2004. Genetic diversity and management of Ne- arctic Rock Ptarmigan {Lagopus mutus). Canadian Journal of Zoology 82:564-575. Tobalske, B. W., T. L. Hedrick, K. P. Dial, and A. A. Biewener. 2003. Comparative power curves in bird flight. Nature 421:363-366. Weins, J. A. 1996. Wildlife in patchy environments: metapopulations, mosaics, and management. Pag- es 53-84 in Metapopulations and wildlife conser- vation (D. R. McCullough, Ed.). Island Press, Washington, D.C. Wilson Bulletin 1 17(1): 15-22, 2005 MINIMUM POPULATION SIZE OF MOUNTAIN PLOVERS BREEDING IN WYOMING REGAN E. PLUMB, 1 ERITZ L. KNOPF,^^ AND STANLEY H. ANDERSON' ABSTRACT. — As human disturbance of natural landscapes increases, so does the need for information on declining, threatened, and potentially threatened native species. Proposed listing of the Mountain Plover (Char- adrius montanus) as threatened under the U.S. Endangered Species Act in 1999 was found unwarranted in 2003, but this species remains of special concern to management agencies and conservation groups. Whereas large concentrations of breeding Mountain Plovers occur in Montana and Colorado, estimates of the numbers of Mountain Plovers in Wyoming have ranged from only 500 to 1,500 individuals and are based largely on conjecture. In 2002, we visited all known breeding locales in the state to define areas of concentrated sightings in the Laramie, Shirley, Washakie, Great Divide, and Big Horn basins. In 2003, we used distance sampling to estimate breeding bird densities in these five areas. We pooled these estimates and applied the resulting density to a minimum occupied range for the Mountain Plover based on the documented sightings and a previously derived home-range size of 56.6 ha ± 21.5 (SD) to generate a minimum population estimate for the state. Average Mountain Plover density was 4.47 ± 0.55 (SE) birds/km-. We calculated a minimum population estimate of 3,393 birds for Wyoming. The Mountain Plover population breeding in Wyoming appears to contribute substantially to a revised continental population estimate of 11,000 to 14,000 birds. Our approach may have applications to quantifying minimum population status of other uncommon species or species of special con- servation concern using current database records, such as those compiled in Natural Heritage Programs at the state level. Received 28 January 2004, accepted 10 December 2004. The Mountain Plover (Charadrius montan- us) is one of 12 avian species endemic to the grasslands of North America (Mengel 1970). Plovers nest on the shortgrass prairie and shrub-steppe of the western Great Plains and Colorado Plateau, especially in areas used his- torically by large assemblages of herbivores, such as prairie dogs (Cynomys spp.), bison {Bison bison), and pronghorns (Antilocapra aniericana; Knopf 1996a). The species win- ters from north-central California to Arizona, Texas, and northern Mexico. Once numerous in Colorado and Wyoming and common in western Kansas, South Da- kota, and Nebraska, Mountain Plovers began to decline throughout their range early in the 20th century (Laun 1957). They have contin- ued to do so over the past 30 years at a rate approximating 3% per year (Knopf 1996a). As a result, the species’ continental breeding range has been significantly reduced. Today the majority of the Mountain Plover's breed- ' Wyoming Coop. I'ish und Wildlife Research Ihiil, Univ. ol Wyoming, liox 3166 Uuiv. .Station. I.aramie. WY 8207 I -3 1 66, USA. ‘ U..S. Geological .Survey, l-ort Collins .Science ('en- ter. 2l5()-(' (’entre Ave., fort ('ollins, CO 80526-81 18. USA. ’Corresponding author; e-mail; t’rit/_knopr(«fiisgs.gov ing range is restricted to east-central Montana (Skaar 2003), the tablelands of Wyoming (Oakleaf et al. 1992), and eastern Colorado (Andrews and Righter 1992, Kingery 1998). The North American population was recently estimated at 8,000 to 10,000 birds (Knopf 1996a). In response to evidence of the species' widespread decline, in 1999 the U.S. Fish and Wildlife Service (USFWS) proposed listing the Mountain Plover as threatened under the U.S. Endangered Species Act (ESA) (U.S. Fish and Wildlife Service 1999). The USFWS recently determined that threats to Mountain Plovers and their habitat are not likely to en- danger the species in the foreseeable future: thus, the proposed listing of the bird was with- drawn (U.S. Fish and Wildlife Service 2003). Regardless, the Mountain Plover remains as a species of special concern to wildlife and laiul managers throughout its range. Although significant breeding po|')ulations occur in Montana and C'olorado, there is e\ i- dcnce that Wyoming may provide habitats for many brcctling Mountain ldo\ers as well. Sur- vey efforts for plovers in Wyoming. cs|X'cially in the wake of the recent I-2SA proposal, ha\e rcN’calcd i-HK'kcts of breeding birds throughout the state, particularly in south-central and eastern Wyoming. I'hc contribution of Moun- 16 THE WILSON BULLETIN • Vol. 1 17, No. I, March 2005 tain Plovers in Wyoming to the continental breeding population is poorly understood, as no reliable statewide population estimate ex- ists. Rough estimates, based largely on con- jecture, have ranged from 500 to 1,500 indi- viduals (FLK). Wunder et al. (2003) recently estimated the size of a similarly undefined population of Mountain Plovers in South Park, (Park Coun- ty), Colorado. Distance sampling was used to estimate density of breeding plovers, from which a population estimate was extrapolated based on an estimate of occupied habitat. Plo- vers in South Park occurred at an average den- sity of 7.9 ± 0.9 (SE) birds/km^ across sam- pled portions of >80,000 ha of potential hab- itat. Wunder et al. (2003) concluded that South Park, with an estimated population of >2,300 Mountain Plovers, contributes 15- 20% of breeding plovers to the continental population. Following the success of Wunder et al. (2003) in generating a population estimate in South Park, Colorado, we used distance sam- pling to generate density estimates of breeding plovers in Wyoming. Although we used dis- tance sampling following Wunder et al. (2003), plovers are much more widely scat- tered in fragmented habitats across Wyoming compared with their single-county study in Colorado. Our objectives were to (1) compile all documented sightings of Mountain Plovers in Wyoming, (2) visit all locals of documented sightings in 2002 to confirm presence of breeding plovers, (3) conduct surveys of adult plovers at selected areas in 2003, and (4) ex- trapolate plover densities over the documented breeding range to obtain a minimum popula- tion estimate for Mountain Plovers in Wyo- ming. METHODS Documented sightings and statewide recon- naissance. — We collected information about documented locations of Mountain Plovers from state and federal agencies, non-profit and consulting firms, and individuals in Wyoming. We mapped these locations using a Geograph- ic Information System (GIS; ESRI ArcMap 8.3). More than 40 agencies, firms, and indi- viduals contributed to the compiled database representing the documented distribution of Mountain Plovers throughout the state. Between 12 May and 18 July 2002, we vis- ited all locations in Wyoming with one or more pre-2002 plover sightings and surveyed for presence of Mountain Plovers. We mod- eled survey protocol after Mountain Plover survey guidelines set forth by the USFWS (U.S. Pish and Wildlife Service 2002). We drove transects along established roads and two-track roads, stopping at 0.4-km intervals to conduct visual scans for plovers. We con- ducted these scans outside of the vehicle to prompt movement of nesting or resting plo- vers and maximize their detectability. There was no predetermined length of time for each visual scan; rather, each lasted as long as nec- essary to cover a 360-degree panorama around the vehicle. Surveys were conducted in the morning between local sunrise and 1 1 :00 MST, and in the afternoon between 16:30 and local sunset to take advantage of horizontal lighting that facilitates detection of plovers. Playback calls were not used. GPS coordi- nates were taken at the site where each Moun- tain Plover was first observed. As time al- lowed, we also surveyed surrounding areas of acceptable habitat from which there were no prior records of plovers; these new sightings were added to the pre-2002 database. Mountain plover study areas. — We identi- fied five Mountain Plover breeding areas for our study. We stratified these areas into two grassland landscapes and three desert-shrub landscapes. The two grassland landscapes were located in the Laramie and Shirley ba- sins, and the desert-shrub areas were in the Big Horn, Great Divide, and Washakie basins. The five areas were selected based upon ac- cessibility for field personnel and the avail- ability of adequate potential habitat to find a minimum of 40 plovers in a 5-day survey pe- riod. Accessibility was limited on many pri- vately owned lands and occasionally vehicle access was limited on public lands. Study areas in the Laramie and Shirley ba- sins included a portion of the Laramie Plains that extends north and west from Laramie to Medicine Bow and Foote Creek Rim, and the central portion of Shirley Basin, roughly de- lineated by the two intersections of Wyoming highways 77 and 487 in northeastern Carbon County. These basins represent the highest-el- evation grasslands in Wyoming (Knight 1994) and are characterized by interspersed short- Plumb et al. • MOUNTAIN PLOVERS IN WYOMING 17 and mixed-grass prairie. Shortgrass species in- clude blue grama (Bouteloua gracilis) and buffalograss (Buchloe dactyloides). Common- ly occurring mixed-grass species include nee- dle-and-thread grass {Stipa comata), western wheatgrass (Agropyron smithii), Sandberg bluegrass (Poa sandbergii), threadleaf sedge {Carex filifolia), and Indian ricegrass (Oryzop- sis hymenoides). Several shrub species, in- cluding pricklypear cactus {Opiintia polyacan- tha), big sagebrush {Artemisia tridentata), budsage {A. spinescens), and fourwing salt- bush (Atriplex canescens) are present. Vege- tation communities vary with topography, which ranges from basins and saltpans to el- evated plateaus. White-tailed prairie dog {Cy- nomys leucurus) colonies are common and grazing by domestic cattle and pronghorn an- telope is pervasive. The desert-shrub study areas included the Mexican Flats, located west of Dad between Wamsutter and Baggs in the Washakie Basin (Carbon County); a portion of the Great Di- vide Basin of the Red Desert located south of Cyclone Rim in northern Sweetwater County; and parts of the Big Horn Basin near Cody and Powell (Park County) and Greybull (Big Horn County), particularly Polecat and Chap- man benches. These shrubland areas are typ- ified by saline soils and are dominated by greasewood {Sarcohatus vermiculatus), shad- scale {Atriplex confertifolia), fourwing salt- bush, and Gardner’s saltbush {A. gardneri), with winterfat {Ceratoides lanata) and prick- lypear cactus interspersed. A mosaic is often formed with stands of big sagebrush, saltbush, and greasewood. Mixed-grass species such as western wheatgrass, prairie junegrass {Koeler- ia macrantha), saltgrass {Distich I is stricta), and ncedle-and-thread grass also occur. Com- munity composition is highly dependent on topography, moisture availability, and soil type. Oil and gas development is common, particularly in the Mexican Flats area. The landscape is grazed by domestic sheep and cattle, and by pronghorn. Wild horses are also present in the Washakie and Great Divide ba- sins to the south. White-tailed prairie dog col- onies are common throughout. Population sampling. — During two lO-day surveys in 2003, we surveyed tor adult Moun- tain Plovers at the five study areas delined in 2002. riie initial survey occurred in late May, when most breeding birds were on nests. This survey was designed to detect all adult plo- vers, but especially those that ultimately might nest unsuccessfully and leave the area before the second survey. The second survey oc- curred in late June to coincide with the chick- rearing phase. The courtship phase in late April and early May was avoided, as survey estimates from that period would be subject to error incurred by detections of migrating birds. Using an ATV driven at <15 km/hr, two observers conducted surveys in each study area along transects with a minimum of 400- m spacing between lines. Plovers move eva- sively in response to observers on foot, but are more tolerant of slow-moving vehicles; thus, we used an ATV to help ensure detection of birds at their initial location. Each transect began on a road or two-track that ran along- side (narrow strips) or through (large patches) potential plover habitat. We used a random numbers table to determine the distance (from the access road or two-track) driven into each survey area before beginning the transect per- pendicular to the access road. We stopped at 0.4-km intervals while surveying and stepped off the ATV. This approach encouraged plo- vers to stand from their nests, and thus be- come more visible. All transects were con- ducted simultaneously by two observers (the double-observer method). Playback calls were not used. We used a laser range hnder (Bush- nell Yardage Pro Sport, rated to 450 m) to measure the distance to each bird detected and a standard compass to establish the sighting angle from the transect line. We look GPS co- ordinates on the transect line for each detec- tion. We conducted all sampling between local sunrise and 1 1:00 and between 16:30 and lo- cal sunset to take advantage of horizontal lighting (reducing the effects of plumage counter-shading) and peak activity levels of the birds. We further reduced the sampling window on exceptionally warm days (>30 C) when heat may have reduced activity le\els and heat waves may ha\e reduced detectabil- ity. Sampling was not conducted when in- clement weather or poor lighting threatenctl to bias probability of detection. Occupied range. Jo define the known oc- cupietl range for Mountain Plovers in Wyo- ming. we combined Mountain Plover loca- 18 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 tions from the reconnaissance phase in 2002, the distance-sampling phase in 2003, and the locations documented elsewhere. We then overlaid onto the GIS map a lattice with grid size equal to the average home range of the Mountain Plover during brood rearing (56.6 ha). The average home-range size of 56.6 ha was first determined from a study in Weld County, Colorado, by affixing radio transmit- ters to adult plovers that were attending chicks, and recording daily movements (Knopf and Rupert 1996). Comparable home- range sizes have since been found in other Mountain Plover habitats (Dreitz et al. 2005). We calculated the minimum breeding range of Mountain Plovers in Wyoming by summing the area of the grids in the overlaid lattice that intersected at least one Mountain Plover lo- cation. A minimum estimate of population size for Wyoming was based on the 2003 den- sity estimates extrapolated across this mini- mum breeding range. Distance analyses. — Using program DIS- TANCE 3.5 (Thomas et al. 1998), we esti- mated overall Mountain Plover densities, as well as densities for subsets of grassland and desert-shrub habitats. Distance sampling (Buckland et al. 2001) uses a set of robust models to estimate densities on the basis of measured distances between detected objects and a central point or transect from which the objects were detected. With regard to under- lying assumptions, methodological self-as- sessment, and efficiency in the field, DIS- TANCE is superior to relative-abundance es- timates generated using point counts (Norvell et al. 2003). We treated the distance data as continuous estimates and considered each of six models suggested by Buckland et al. (2001). These models were each composed of a key function or general shape proposed to fit the detection function, and a nonparametric flexible form called a “series expansion” that adjusted the key function. The six models used were the uniform key function with co- sine and simple polynomial expansion series, the half-normal key function with cosine and hermite polynomial expansion series, and the hazard-rate key function with cosine and sim- ple polynomial expansion series. The uniform and half-normal key functions are proposed shapes for the detection function, based on a priori assumptions about the detection pro- cess, whereas the hazard-rate key function is a derived model. We pooled plover sightings recorded from the two 2003 surveys and trun- cated the largest 10% of sampled distances to reduce error incurred by outliers, as recom- mended by Buckland et al. (2001). Histo- grams of the probability of detection were in- spected for violation of statistical assump- tions. We also considered the six suggested models with stratification by habitat, but strat- ified models were inferior to unstratified mod- els. Comprehensive explanations of sampling procedure and model selection are given in Buckland et al. (2001) and Burnham and An- derson (2002). Our analytic approach was similar to that used by Wunder et al. (2003) for estimating Mountain Plover densities in Park County, Colorado. We used Akaike’s Information Criterion (AIC) to evaluate the relative strength of each of the 12 models. Because AIC identifies the best of a set of competing models but does not reflect the quality of fit, goodness-of-fit P- values were also considered to identify poorly fitting models {P < 0.05), should any exist. To avoid bias incurred by basing parameter estimates on a single model from a set of closely competing models, we used model av- eraging based on weighted AIC contributions from all 12 models to generate overall density estimates. We estimated density, detection probability, and detection strip half-width for grassland and desert-shrub habitat subsets us- ing model averaging across a set of unstrati- fied models for each habitat. RESULTS Inventory and occupied range. — We com- piled and mapped >2,000 sightings of Moun- tain Plovers representing input from >40 sources. These records included 1,347 sight- ings from the Wyoming Natural History Di- versity Database, —93% and —57% of which were reported in the last 20 and 10 years, re- spectively. Virtually all documented sightings from other sources were made within the last 10 years. In 2002, we detected 171 Mountain Plovers on 1,416 km of roads and two-tracks during reconnaissance visits to previously documented sites. We added these 2002 plo- ver locations and 449 new locations recorded during distance sampling in 2003 to the da- tabase of documented sightings to map the Plumb et al. • MOUNTAIN PLOVERS IN WYOMING 19 TABLE 1. Estimates (SE) of Mountain Plover density, probability of detection, and effective detection strip half-width in grassland and desert-shrub habitats in Wyoming for 2003. Estimates (SE) are derived from DIS- TANCE 3.5 (Thomas et al. 1998). Birds detected Density (plovers/km^) Detection probability Effective strip half-width (m) Grassland Desert-shrub 113 5.17 (1.06) 0.82 (0.13) 114.70 (18.68) 190 4.23 (0.67) 0.73 (0.06) 111.50 (8.6) known occupied range of Mountain Plovers in Wyoming. The resulting 2,695 compiled ob- servations intersected 1,341 cells in the over- laid 56.6-ha “home range” grid. Therefore, the known occupied range of Mountain Plo- vers in Wyoming included at least 75,901 (i.e., 1,341 X 56.6) ha of potential habitat. The five study areas for the randomized distance sam- pling in 2003 overlapped 44% of the known plover locations in Wyoming. Density and minimum population esti- mates.— We detected 303 Mountain Plovers during distance sampling along 276 km of transects, roughly divided among the five study areas in 2002. Pooled data across the two 2003 sampling efforts yielded a minimum of 40 detections for each study area. Estimates of density, detection probability, and effective strip half-width were similar for grassland and desert-shrub habitats (Table 1). Although the hazard-rate key function with cosine and simple polynomial expansion se- ries provided the best fit to the detection func- tion for the unstratified data, all 12 models (six unstratified, six stratified) had AAIC < 5.0 and goodness-of-fit P-values >0.1. The overall density estimate, averaged over 12 models, was 4.47 ± 0.55 birds/km^ (Table 2). In general, the unstratified models showed lower AIC values than the stratified models. Although the poorest fitting unstratified model was as likely as the best stratified model (AAIC = 2.2, w, = 0.07 for both), the unstrat- ified models contributed 78% of the weighted estimates. All of the models fit the data well: goodness-of-fit test statistics for the unstrati- fied models (from lowest to highest P-value) ranged from = 3.56 {P = 0.17) to - 2.12 {P = 0.35). Assuming an average home-range size of TABLE 2. Models used to generate density estimates for Mountain Plovers in five breeding areas in Wyo- ming for 2003. Both pooled and stratified models are included. Models were run using 303 detections and 10% truncation. Models are ordered by increasing AAIC. The AIC weight (vr,), density estimate, and coefficient of variation (CV) are provided for each model. Model AAIC AIC weight (ve,) Density (birds/kn4) cv Unstratified Hazard rate + cosine ().(P 0.20 4.37 0.12 Hazard rate + simple polynomial ().(P 0.20 4.37 0.12 Uniform simple polynomial 0.6 0. 1 5 4.60 0.1 1 Half normal + hermite polynomial 1.7 0.09 4.45 0.15 Half normal -f cosine 2.2 0.07 4.53 0.15 Uniform + cosine 2.2 0.07 4.52 0.14 Stratified^ Uniform -I- simple polynomial 2.2 0.07 4.59 0.10 Hazard rate + simple polynomial 3.0 0.05 4.37 0.12 Hazard rate -f cosine 3.0 0.05 4.37 0.12 Half normal + hermite polynomial 4.2 0.02 4.80 0.1 1 1 lalf normal + cosine 4.2 0.02 4.80 0.1 1 Uniform -1- cosine 5.0 0.02 4.55 0.1 1 •AIC IWIJ. Stralilicil by habiial type. 20 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 56.6 ha (Knopf and Rupert 1996) for Moun- tain Plovers, the overall density estimate can be applied to the 75,901 ha of geographic range documented in Wyoming to generate a population estimate of 3,393 birds (75,901 ha X 4.47 birds/km-). The lower confidence limit for average Mountain Plover home range (35.1 ha) can be used to generate a more con- servative estimate of 2,270 birds. Because the occupied range for Mountain Plovers in Wy- oming is surely underestimated, the upper confidence limit for home range (78.1 ha) may be a better approximation, yielding a popula- tion estimate of 4,427 birds. DISCUSSION Generating reasonable population estimates is particularly challenging for low-density species of conservation concern, such as the Mountain Plover. Distance sampling is a pow- erful tool for developing such estimates given the time and resources to collect adequate data. Buckland et al. (2001) recommend a sample size of at least 60-80 detections, but admit that suitable precision may require sev- eral hundred detections. Reasonable sample sizes were only achieved in this study by fo- cusing sampling efforts on areas with rela- tively high concentrations of recent (<20 years) Mountain Plover sightings. Those areas occur either where plovers are most visible or where people look for plovers. Much (perhaps most) of the potential plover habitat in Wyo- ming has never been surveyed for the species. The validity of the extrapolated minimum population estimates described here largely rests on the accuracy of estimates of occupied range and average home-range size for Moun- tain Plovers. Given the impracticality (scale of effort, access to private lands) of surveying all potential Mountain Plover habitat in Wyo- ming, we initially considered a habitat-based model that employed satellite imagery for es- timating the occupied range of the species. This model was deemed unsuitable because Mountain Plovers in Wyoming frequently oc- cupy habitat patches of such small size or sub- tle distinction, relative to the dominant cover type, that suitable patches cannot be distin- guished remotely. Therefore, we compiled documented sightings of plovers collected by field biologists to represent a best-available approximation of a statewide survey for Mountain Plovers. It is likely that many breeding locales are still unknown and un- surveyed, thus affirming the minimum nature of our estimates. The second assumption, that the home-range size from Weld County, Col- orado, can be applied to other areas, has re- cently been confirmed by studies that revealed comparable home-range size in dissimilar habitats at various locales (Dreitz et al. 2005). Finally, we assumed that densities in sampled areas are representative of densities through- out the species’ occupied range. This latter as- sumption was supported by the similar plover densities calculated in grassland versus desert- shrub habitats. We did not need to assume plover occupan- cy of all pre-2003 grid cells in our extrapo- lation of calculated plover density across the pre-2003 sightings template. Distance sam- pling in the 2003 survey areas was indepen- dent of both the pre-2003 cell distribution and any knowledge of statewide plover-density patterns. The 2003 distance-sampling tran- sects (covering 44% of the pre-2003 area) would have been as likely to sample 2003- occupied as 2003-unoccupied cells in the pre- 2003 database. Thus, the distance sampling effort in 2003 included “occupancy” infor- mation relative to the earlier sightings. Plover densities were comparable across habitat types. The overall density in grassland habitats was slightly higher (5.17 birds/km-) than in desert-shrub habitats (4.23 birds/km-), with considerable overlap between confidence intervals. Eighty-six percent of the desert- shrub confidence interval was contained by the grassland confidence interval. The congru- ence of density estimates across habitats sup- ports the calculation of a pooled density esti- mate to represent plover habitats statewide. The average density of Mountain Plovers in documented breeding areas in Wyoming (4.47 ± 0.55 birds/km-) is somewhat lower than most density estimates within the species’ breeding range. Finzel (1964) reported 6.2 birds/km- near Laramie and 12.3 birds/km^ near Cheyenne, Wyoming. Wunder et al. (2003) reported densities of 6. 0-9.0 birds/km^ for South Park, Colorado, and Knopf (1996a) reported densities of up to 4.7 birds/km- on Pawnee National Grassland in Colorado and 1.3-6. 8 bird/km“ on prairie dog towns in Montana. Graul and Webster (1976) estimated Plumb et al. • MOUNTAIN PLOVERS IN WYOMING 21 plover densities at 8.0 birds/km^ in areas of Wyoming and Montana. Our calculated potential habitat of 759 km^ for Mountain Plovers in Wyoming is an un- derestimation. Most private lands have never been surveyed for plovers. These lands are primarily used for grazing, a major component of plover habitats throughout the year (Knopf 1996a, Wunder and Knopf 2003). The only desert regions of Wyoming being surveyed consistently at present are those targeted for 011 and gas leasing or development. We also note that whereas the most productive grazing lands in Wyoming are in private ownership, our surveys were conducted on publicly owned, less productive landscapes. Mountain Plover densities are likely higher in the pri- vately owned and more productive land- scapes, and those landscapes are under-repre- sented in our potential-habitat database. Considering that the recent global popula- tion estimate for Mountain Plovers is 8,000 to 10,000 individuals (Knopf 1996a), and that Wyoming’s conservative estimate of 3,393 plovers may not include birds that (1) occupy large expanses at low densities, (2) occur in isolated small patches of habitat (e.g., historic buffalo wallows; FLK pers. obs.), or (3) breed at undiscovered spots, Wyoming’s Mountain Plovers appear to contribute substantially to a revised continental population estimate of 1 1,000 to 14,0()0 birds. Furthermore, manage- ment strategies for Mountain Plover habitat in Wyoming often emulate the historical ecolog- ical drivers (e.g., drought and grazing; Knopf and Samson 1997) to a greater extent than do practices in neighboring states where cultiva- tion and urbanization are more widespread. When rangeland conversion to row cropping does occur in Wyoming, it is generally to a lesser extent than in other states within the plover’s range. Between 1982 and 1997, more than three times as much rangeland within the occupied breeding range of Mountain Plovers was converted in Montana than in Wyoming; 12 times as much potential habitat was con- verted in Colorado (U.S. Fish and Wildlife Service 2003). Wyoming’s population of Mountain Plovers and relatively intact ex- panses of grazed rangeland may become in- creasingly important for the species as urban and agricultural development continues in contiguous states. Mountain Plovers, like many species of conservation interest, occur in low densities and in a variety of landscapes. Plovers often are not detected in general biotic surveys due to their relative inconspicuousness. Our study took advantage of an existing database of mostly casual observations to focus intensive surveys for estimating population status in Wyoming. This approach may be useful for quantifying minimum population size of other species of conservation concern. Existing da- tabase records, such as those available from state Natural Heritage Programs, may be par- ticularly useful. ACKNOWLEDGMENTS We are especially grateful to V. L. Sepulveda for invaluable field assistance spanning two seasons. Thanks to M. B. Wunder for assistance with program DISTANCE, and to the U.S. Fish and Wildlife Service, U.S. Geological Survey, U.S. Bureau of Land Man- agement, and the Wyoming Game and Fish Depart- ment for funding assistance. B. A. Banulis, S. R. Moh- ren, N. P. Nibbelink, J. C. Oakleaf, and S. J. Slater provided critical GIS support. Field biologists G. P. Beauvais, T. W. Byer, L. D. Hayden-Wing, L. G. Keith, T. Maechtle, S. H. Nicholoff, R. J. Oakleaf, M. S. Reid, D. F. Saville, and L. Van Fleet deserve recognition. S. J. Dinsmore provided helpful comments on the man- uscript. We are indebted to landowners in the Laramie and Shirley basins for providing access to their private lands. We acknowledge R. L. Leachman for his tireless years of effort to secure the future of Mountain Plo- vers. LITERATURE CITED Andrews, R. and R. Richter. 1992. Colorado birds: a reference to their distribution and habitat. Den- ver Museum of Natural History, Denver. Colora- do. Bucki.and, S. T, D. R. Anderson, K. P. Bl rnha.m, J. L. Laake, D. L. Borchers, and L. Thomas. 2001. Introduction to distance sampling. O.xfcnd Uni- versity Press. New York. Burnham, K. P. and D. R. Ander.son. 2002. Model .selection and multi-model inference: a practical information-theoretic approach. Springer- Verlag. New York. DrEIT/, V. L.. M. B. Wl NDI R. AND 1. L. Knoit. 200.S. Movements and home ranges of Mountain PIo\ers raising broods in three C'olorado landscapes. W il- son Bulletin, in press. l iN/i I , .1. F. 1904. Avian populations of four herba- ceous communities in southeastern Wyoming, (’ondor 00:490 510. ('iRAi i, W. I). AND L. p;. WiMsriR. 1970. Breeding status of the Mountain Plover, (’ondor 78:205 207. 22 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 Kingery, H. E. (Ed.). 1998. Colorado breeding bird atlas. Colorado Bird Atlas Partnership and Colo- rado Division of Wildlife, Denver, Colorado. Knight, D. H. 1994. Mountains and plains: the ecol- ogy of Wyoming landscapes. Yale University Press, New Haven, Connecticut. Knopf, E L. 1996a. Mountain Plover {Charadrius montanus). The Birds of North America, no. 211. Knopf, E L. 1996b. Prairie legacies — birds. Pages 135-148 in Prairie conservation: preserving North America’s most endangered ecosystem (E B. Sam- son and E L. Knopf, Eds.). Island Press, Covelo, California. Knopf, E L. and J. R. Rupert. 1996. Reproduction and movements of Mountain Plovers breeding in Colorado. Wilson Bulletin 108:28-35. Knopf, E L. and E B. Samson. 1997. Conservation of grassland vertebrates. Ecological Studies 125: 273-289. Laun, H. C. 1957. A life history study of the Mountain Plover, Eupoda montana, Townsend, on the Lar- amie Plains, Albany County, Wyoming. M.Sc. thesis. University of Wyoming, Laramie. Mengef, R. M. 1970. The North American central plains as an isolating agent in bird speciation. Pag- es 280-340 in Pleistocene and recent environ- ments of the Central Great Plains (W. Dort and J. K. Jones, Eds.). University of Kansas Press, Law- rence. Norvell, R. E., E P. Howe, and J. R. Parrish. 2003. A seven-year comparison of relative-abundance and distance-sampling methods. Auk 120:1013- 1028. Oakleaf, B., B. Luce, S. Ritter, and A. Cerovski, (Eds.). 1992. Wyoming bird and mammal atlas. Wyoming Game Fish Department, Lander. Skaar, P. D. 2003. P. D. Skaar’s Montana bird distri- bution, 6th ed. Montana Natural Heritage Pro- gram, Helena. Thomas, L., J. L. Laake, J. F. Derry, S. T. Buckland, D. L. Borchers, D. R. Anderson, K. P. Burnham, ET AL. 1998. Distance 3.5, release 6. Research Unit for Wildlife Population Assessment, Univer- sity of St. Andrews, United Kingdom. U.S. Fish and Wildlife Service. 1999. Endangered and threatened wildlife and plants: proposed threatened status for the Mountain Plover. Federal Register: 64(30):7587-7601 . U.S. Fish and Wildlife Service. 2002. Mountain Plo- ver survey guidelines, http://montanafieldoffice. fws.gov/Endangered_Species/Survey_Guidelines/ Mountain_Plover_Survey_Guidelines.pdf (accessed March 2002). U.S. Fish and Wildlife Service. 2003. Endangered and threatened wildlife and plants: withdrawal of the proposed rule to list the Mountain Plover as threatened. Federal Register 68( 1 74):53083- 53101. WuNDER, M. B. AND F. L. Knopf. 2003. The Imperial Valley of California is critical to wintering Moun- tain Plovers. Journal of Field Ornithology 74:74- 80. WuNDER, M. B., F. L. Knopf, and C. A. Pague. 2003. The high-elevation population of Mountain Plo- vers in Colorado. Condor 105:654-662. Wilson Bulletin 1 17( l):23-34, 2005 NEST SURVIVAL RELATIVE TO PATCH SIZE IN A HIGHLY FRAGMENTED SHORTGRASS PRAIRIE LANDSCAPE SUSAN K. SKAGEN,*-^ AMY A. YACKEL ADAMS, ^ AND ROD D. ADAMS* ^ ABSTRACT. — Understanding the influences of habitat fragmentation on vertebrate populations is essential for the protection and ecological restoration of strategic sites for native species. We examined the effects of prairie fragmentation on avian reproductive success using artificial and natural nests on 26 randomly selected, privately owned patches of shortgrass prairie ranging in size from 7 to 454 ha within a cropland matrix in Washington County, Colorado, summer 2000. Survival trends of artificial and natural nests differed. Daily survival of artificial nests increased with patch size up to about 65 ha and differed little at larger patch sizes, whereas daily survival of Lark Bunting {Calamospiza melanocorys) and Horned Lark (Eremophila alpesths) nests decreased with increasing size of the grassland patch. We hypothesize that our unexpected findings of lower survival of natural nests with increasing patch sizes and different trends between artificial and natural nests are due to the particular structure of predator communities in our study area and the ways in which individual predators respond to artificial and natural nests. We recommend that the value of small habitat patches in highly fragmented landscapes not be overlooked. Received 1 April 2004, accepted 3 November 2004. Understanding the influences of habitat structure and habitat fragmentation on the vi- ability of grassland species is essential to con- servation planning, especially for protection and ecological restoration of strategic sites for native species. Many grassland bird species, including those of the shortgrass prairie, have experienced population declines in the past 3 decades (Knopf 1994, Murphy 2003, Sauer et al. 2003). Between 1966 and 2002, popula- tions of Lark Buntings (Calamospiza melan- ocon's) and Horned Larks (Eremophila alpes- tris) declined 2.0 and 1.6% per year, respec- tively, in the High Plains physiographic region (Sauer et al. 2003). Although mechanisms for these declines have not been identified, factors influencing reproductive success are among the possibilities. Shortgrass is the least dis- turbed of the three prairie types in North America, with as much as 40% remaining un- plowed (Samson and Knopf 1996). Even though the extent of habitat loss is consider- ably less than in the tallgrass prairie (82-99%; Samson and Knopf 1996), habitat loss and fragmentation of breeding areas may contrib- ute to population declines of shortgrass prairie birds. ' U.S. Geological Survey, 1-ort Gollins Science ('en- ter, 2150 ('enlre Ave., Bldg. (', bort ( ollins, ( () K0526-S1 18, USA. ' C'urrent address: Dept. ol Philosophy, Golorado State Univ., f-ort (’ollins. (’() 80523. U.S A. ' ('orrespoiuling author; e-mail: susaii-skagen («■’ usgs.gov Broad generalizations regarding the nega- tive effects of habitat fragmentation on den- sity and reproductive success of avian species are common in the scientific literature of the past 2 decades (Ambuel and Temple 1983, Herkert 1994, Donovan et al. 1995, Freemark et al. 1995). Studies on the effects of habitat fragmentation, specifically patch size and iso- lation, initially were stimulated by island bio- geography theory (MacArthur and Wilson 1967, Diamond and May 1981) and subse- quently by emerging landscape perspectives (Fahrig and Merriam 1994, Wiens 1995). When detected, patch size effects typically show that smaller habitat patches have lower habitat quality, more edge habitat, fewer spe- cies, fewer or no individuals of area-sensitive species, and/or lower reproductive output — due to increased predation and brood parasit- ism or decreased food abundance (Britting- ham and Temple 1983, Herkert 1994. Burke and Nol 1998, Robinson 1998). These gener- alities are now being incorporated as assump- tions in quantitative models of the effects of habitat fragmentation and edge effects on the demography of birds (Donovan and Lamber- son 2001, Bollinger and .Switzer 2002). Despite broad support Tor these generalities, inconsistencies ha\e been documented in well-studied systems. Although larger forest l^atches in h)iested landscapes are thought to provide better habitat (Donovan et al. 1995. Robinson et al. 1995. rhompson et al. 2002), not all studies supjrort that pattern (Mar/lut’l 23 24 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 and Restani 1999). For example, in western forests, predation rates in fragments are often lower than in unfragmented sites (Tewksbury et al. 1998, Cavitt and Martin 2002). Current paradigms are rapidly evolving with the in- creased scrutiny of inconsistencies in the for- est fragmentation literature (Donovan et al. 1997, Walters 1998, Marzluff and Restani 1999, Heske et al. 2001, Thompson et al. 2002). A major challenge to our understand- ing of the effects of habitat fragmentation on birds is the variability in their responses to fragmentation, or “differential sensitivity” (Walters 1998) — across regions, landscapes, habitats, species, and populations. The effects of prairie fragmentation on re- productive success of grassland birds have been documented primarily in tallgrass prairie and in artificial nest studies. The effects are equivocal. Several bird species have experi- enced lower nest success in smaller grassland patches or near woody edges in field-forest ecotones (Herkert et al. 2003), but such effects do not universally apply to all grassland hab- itats and species (Gates and Gysel 1978, John- son and Temple 1990, Winter and Faaborg 1999, Winter et al. 2000). Of five studies that employed artificial nest techniques in grass- lands, only one (Burger et al. 1994) reported increased mortality of artificial nests with de- creasing grassland patch size and distance from edges (in this case forest edges). Four of these studies reported no differences in mor- tality of artificial nests relative to grassland patch size or distance to edge, including for- ested and agricultural edges (Mankin and Warner 1992, Clawson and Rotella 1998, Pas- itschniak-Arts et al. 1998, Howard et al. 2001). The lack of a patch size effect in these studies may result, in part, from the range in patch sizes being above or below a threshold at which an effect could be detected. The search for generalities is often a search for clear and consistent trends reported by several studies. “Similar conclusions obtained from studies of the same phenomenon con- ducted under widely differing conditions will give us greater confidence in the generality of those findings than would any single study” (Johnson 2002). To contribute to our knowl- edge of potential effects of prairie fragmen- tation on birds, we conducted a study in a highly fragmented shortgrass prairie land- scape (<15% grassland). The primary objec- tive of our study was to determine the effects of patch size on reproductive success of prai- rie birds. We selected our study sites randomly so that we could make inferences to our entire target population (see Site selection) rather than just to the individual grassland patches. METHODS Study area. — The shortgrass prairie land- scape is dominated by xeric grasses, such as buffalograss (Buchloe dactyloides) and blue grama (Bouteloua gracilis). Common breed- ing birds are Horned Larks, Western Mead- owlarks {Sturnella neglecta). Lark Buntings, Chestnut-collared Longspurs (Calcarius or- natus), and Grasshopper Sparrows (Ammodra- mus savannarum). Potential mammalian pred- ators of ground-nesting birds include thirteen- lined ground squirrels (Spermophilus tride- cemlineatus), coyotes (Canis latrans), swift foxes {Vulpes velox), long-tailed weasels (Mustela frenata), badgers (Taxidea taxus), and striped skunks {Mephitis mephitis). Com- mon snake species that opportunistically prey on birds include bullsnakes {Pituophis melan- oleucus), western hognose snakes (Heterodon nasicus), and prairie rattlesnakes (Crotalus v. viridis). Our study was conducted during the sum- mer of 2000 in a 4,842-km^ agricultural region of Washington County in northeastern Colo- rado (39° 34' N to 40° 27' N; 102° 48' W to 103° 28' W). Land-use cover types in the study area include dryland wheat (non-irrigat- ed wheat production in a 2-year rotation sys- tem; 73.9%), shortgrass prairie rangeland (14.3%), Conservation Reserve Program (CRP) fields (6.1%), and irrigated crops (3.7%). This agricultural area was adjacent to three large grasslands, totaling 1 ,689 km^, that were not considered in this study. Site selection. — We used satellite imagery (provided by the Colorado Division of Wild- life) to quantify land cover and restricted ran- domization to select study sites. Using Arc- Info, we identified all {n = 557) polygons of short- and midgrass prairie and measured cor- responding area and perimeter. We calculated a diversity index (D7; Patton 1975) as Skagen et al. • NEST SURVIVAL IN PRAIRIE FRAGMENTS 25 where TP is the total perimeter of the polygon and A is the area of the polygon. For refer- ence, a circle has a /)/ of 1 and a square has a DI of 1.3. Of the 557 identified grassland polygons, the median area was 35.7 ha (mean = 125.5 ± 367.6 SD; range 2.1-4,886.8 ha) and mean DI = 2.0 ± 0.7 SD. We omitted 96 polygons with DI >2.5 to eliminate the po- tentially confounding effect of highly elon- gated patches. We sorted the polygons into several size classes (in increments of 10 ha between 0 and 150 ha, and in increments of 50 ha between 150 and 500+ ha) and randomly selected 2- 4 from each size class as possible study sites. We ground-truthed the polygons (hereafter grassland patches) to verify their size and iso- lation and to update the surrounding land-use type. We considered only grassland patches that were at least 0.4 km from other grassland habitats. Grassland patches that were within 0.4 km of human habitation or riparian trees were also omitted to minimize the effects of predation by farm cats or corvids (Delisle and Savidge 1996). We obtained permission from landowners and conducted our study on 26 grassland patches ranging from 7 to 454 ha in size (mean = 106.4 ± 109.4 SD, CV = 1.03; n = 4 patches 7-20 ha, n = 6 patches 21-50 ha, n = 1 patches 50-100 ha, n = 5 patches 100-200 ha, n = A patches >200 ha). Artificial nests. — Nests consisted of a scrape on the ground where we placed two fresh Japanese quail (Coturnix japonica) eggs and one clay egg (mean = 22 X 15 mm, n 20) made of soft modeling compound (Scul- pey 111 brand) to approximate the size of Lark Bunting eggs (mean = 22 X 17 mm; Baicich and Harrison 1997). Clay eggs aided in the idenlihcalion of nest predators (by examining tooth impressions) and enabled us to record predation by predators too small to handle quail eggs (i.c., small rodents; Major and Ken- dal 1996). We inserted an orange-painted nail in the ground under the eggs to facilitate lo- cating the nests after a disturbance. Artificial nests in = 312) were set out at 24 sites be- tween 31 May and 3 June and at 2 additional sites on 8 June 2()0(). At each site, we placed six nests near an edge (a grassland/! allow- field interface at 18 sites and a grassland/ planted-field interface at 8 sites; planted sites were primarily wheat). At l()()-m intervals along the edge, we paced a random distance (5-30 m) toward the interior and placed the artificial nest. We also placed six nests in the interior of each site (generally 100-500 m from the edge). In small sites, interior nests were placed as far from the edge as possible; 95% of all interior nests were >100 m from an edge and only one interior nest was <75 m. Interior nests were also placed 100 m apart; however, nests were placed closer to- gether in small sites (50 m in four and 25 m in one) to enable the placement of six nests. Distance from the patch edge averaged 17.9 m ± 7.1 for edge nests and 259.1 m ± 121.1 for interior nests. For nest survival analyses, we coded distance from edge as 1 = edge, 2 = interior. We checked nests twice, at 5 and 9 days after placement; eggs were removed from dis- turbed nests at the first check and from all remaining nests during the second check. Nests were classified as intact or disturbed based on signs of disturbance to either quail or clay eggs. Nests were considered disturbed if quail eggs were missing, broken, or moved, or if clay eggs were missing, moved, or had tooth impressions. We classified markings on the clay eggs as rodent, non-rodent, insect, or unknown by comparing them with known tooth impressions made from skulls in the zo- ology collection at Colorado State University, Fort Collins. In the absence of other signs of disturbance, nests containing clay eggs with only insect marks were considered intact. Natural nests. — All grassland patches were systematically searched for nests by dragging a rope between two observers —28 m apart and by observing adult behavior. We marked the location of nests with unmarked wooden stakes (2.9 X 28.5 cm) positioned 10 m from nests; painted wooden stakes (2.9 X 28.5 cm) were also placed 30 m from nests (aligned with the unmarked stake and nest) to facilitate relocating nests. When nests were finind, we floated two eggs to determine their age, using a technic|ue described by Westerskov (1950) and modified for Lark Buntings aiul Horned Larks. We mofiitoretl the nests and recorded numbers, ages, and status of eggs and nest- lings at 2- to 4-ilay intervals until nests were empty. During the last nest check, we fiotetl signs that woukl help determine whether yoiuig fledged (parents feeding young or call- 26 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 ing in the vicinity, fecal droppings outside of the nest [deposited only when young hop out; A AY A pers. obs.]). For each nest, we esti- mated distance from patch edge, coded as 1: <30 m, 2: 30-100 m, and 3: >100 m. Vegetation sampling. — Vegetation structure and composition of grassland patches were characterized by sampling between 31 May and 7 June at six random points along line transects through the center of each site. Mea- surements included visual estimates of the percent cover of grasses (identified to spe- cies), sedges, forbs, shrubs, cacti, and bare ground within 5-m radius plots, as well as measurements of grass height and vegetation density at distances of 1, 3, and 5 m due east from the point. Vegetation density was re- corded as the total number of vegetation hits on a 1-cm-diameter pole at intervals of 0-5, 5-10, 10-20, and 20-30 cm above ground. We constructed a variable (VegStruc) to de- scribe overall vegetation structure as percent cover of green vegetation X median grass height X vegetation density. Analyses. — We used Pearson correlation to assess relationships between patch area (In- transformed to improve normality) and nine vegetation-structure variables: percent cover of grasses, forbs, shrubs, bare ground, and green vegetation (grasses, sedges, forbs, shrubs, and cacti); maximum grass height; median grass height; vegetation density; and overall vegetation structure. We used the “Mayfield logistic regression” approach recently described by Hazier (2004) to examine daily survival of artificial and nat- ural nests as a function of three variables: patch size (Patch area), distance from edge (Edge), and vegetation structure (VegStruc). Mayfield logistic regression is an alternative to typical logistic regression (i.e., 1 nest = 1 trial) because it accounts for the number of exposure days (i.e., 1 exposure day = 1 trial). We used the “Last Active-B” approach of Manolis et al. (2000) to calculate exposure days, and we censored the last nest check in- terval for nests with unknown fate (Stanley 2004). During nest checks after the fledge date, we assumed nests were successful if we observed fledglings, parental behavior near nests that suggested presence of fledglings (calling, feeding young), or fecal droppings immediately outside the nest. We fitted models with PROC LOGISTIC (SAS Institute, Inc. 1999) and evaluated these models using AIC (Akaike 1973, Burnham and Anderson 2002) corrected for small sam- ple size (AIC^,). The difference (A,) between model / and the model with the minimum AIC^ value allows for a quick comparison and ranking of models. The model with the small- est AIC^. is the best-approximating model of the candidate models, given the data. The AIC^ weight (w,) for model i, calculated as (where R is the number of candidate models in the set), is useful in assessing the weight of evidence in favor of a model. Burnham and Anderson (2002:167) recommend the use of summed Akaike weights (Sw,) to evaluate the relative importance of variables when a bal- anced model set is used (e.g., in our analysis each variable appeared in four models). We computed a relative importance measure for each variable by summing Akaike weights over every model in which that variable ap- peared. Because of model-selection uncertainty (it is plausible that models with AAIC^ values <7 are reasonable), we model-averaged the SAS- generated effect sizes (P, regression coeffi- cients) over the entire set of models with a weighted average based on Akaike weights (Burnham and Anderson 2002:253, equation 5.8). We computed unconditional standard er- rors for the effect sizes, thereby incorporating model-selection uncertainty into precision es- timates, and used the Z distribution to calcu- late 95% confidence intervals (Cl). Because PROC LOGISTIC models nest failure, signs of all coefficients were reversed to interpret effects on survival (see Hazier 2004). Herein we present a positive p to indicate increased nest survival and a negative P to indicate de- creased nest survival relative to a given pre- dictor variable. The strength of the effect (P) is indicated by whether the 95% Cl of the re- gression coefficient includes zero. A 95% Cl where p does not overlap zero is analogous to P < 0.05, and a 90% Cl where the P does not overlap zero is analogous to P < 0.10. Skagen et al. • NEST SURVIVAL IN PRAIRIE ERAGMENTS 27 TABLE 1. Summary of model-selection results for survival of artificial and natural nests (Lark Bunting and Horned Lark) in Washington County, Colorado, summer 2000. Models with the lowest AAIC^ and the greatest Akaike weight (Wj) have the most support and are highlighted in boldface. K is the number of parameters in each model, including the intercept and each explanatory variable; n = total number of trials (nest-exposure days). Nest survival models Artificial nests (n = 1,492) Lark Bunting (/; = 204) Horned Lark (n =321) K AAIC,. H7 K AAIC,. W, K AAIC,. H', Patch area"" + Edge + VegStruc 5 1.61 0.138 4 3.99 0.056 4 3.94 0.039 Patch area"* + Edge 4 1.63 0.137 3 1.96 0.155 3 1.89 0.110 Patch area"* + VegStruc 4 0.00 0.308 3 2.04 0.149 3 1.78 0.1 16 Edge + VegStruc 3 4.83 0.027 3 6.18 0.019 3 4.11 0.036 Patch area“ 3 0.09 0.294 2 0.00 0.414 2 0.00 0.282 Edge 2 6.44 0.012 2 4.59 0.042 2 2.10 0.099 VegStruc 2 3.30 0.059 2 4.22 0.050 2 2.33 0.088 Constant 1 5.05 0.025 1 2.58 0.114 1 0.40 0.231 We used a quadratic function of patch area in artificial nest models; patch area was used in Lark Bunting and Horned Lark models. We In-transformed patch area (hereafter patch area) to improve normality. Because we were unsure of the shapes of curves describ- ing relationships between nest survival and patch area, we compared AIC values of mod- els that included (1) patch area and (2) a qua- dratic function of area (patch area + patch area^) before formalizing the candidate mod- els. We then ran all possible additive combi- nations, including a constant model, for a total of eight models. We present calculated estimates of overall nest survival, artificial nest survival for each grassland patch, and natural nest survival in small (<8() ha) and large (>80 ha) patches using the Mayfield technique (Mayfield 1975) and standard errors of the estimates following Johnson (1979). We used the 8()-ha cutoff to ensure adequate sample sizes for Mayfield es- timates of natural nest survival. Overall nest success was calculated as the daily survival rate (DSR) raised to the power of the length of the nesting period (21 and 20 days for Horned Larks and Lark Buntings, respective- ly). All estimates are reported ± SH, unless noted otherwise. RHSUIXS Vegetation composition and structure. — The dominant grasses in the study sites, in order of percent cover, were bulfalograss, western wheatgrass {Agropyron smithii), blue grama, needleandlhread (Hesperostipa conui- ta), sixweeks fescue {Vidpia octoflora), and red threeawn {Aristida purpurea). Median grass height was 10.0 cm and ranged from 1 to 20 cm across all patches. There were no differences in vegetation structure that related to patch area; none of the nine vegetation structure variables was correlated with patch area (| r | < 0.270, P > 0.15 in all cases). The matrix immediately surrounding the grassland patches was primarily dryland wheat (approx- imately 78% of patch perimeter), CRP mono- cultures of smooth brome (Bronius inermis, 18%), and irrigated crops (4%). The influence of grassland patch size on predation rates on artificial nests. — Mean dai- ly survival of artificial nests across all sites was 0.834 ± C.OlO (95% Cl = 0.815-0.853, n = 312). Edge nests had slightly greater daily survival than interior nests (0.841 ± 0.013; 95% Cl = 0.815-0.867, n = 156 edge ne.sts; and 0.826 ± 0.014; 95% Cl - 0.799-0.853, n = 156 interior nests). For artificial nests, we chose the quadratic rather than the linear function of patch area to represent area in the candidate models, based on relative AIC, values of 1339.35 and 1343.75, respectively. Daily survival of arti- ficial nests was best explained by the c|ua- dratic function of patch area and VegSlruc ( fable 1 ). Distance from edge had little intlu- ence on survival of artificial nests, as denoted by low Akaike model weights ( fables 1. 2). fhe predictor variables ordered by their esti- mated importance are area, vegetation struc- ture, anti etlge, as jiortrayed by the summed weights of 0.876. 0.532, and 0.314. re- spectively ( fable 2). 28 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 > ^ a ^ 'B ^ ^ S s o ^ J Ijj . , hJ — ^ TO wj ’C c/2 u C3 W -H c O S U 3 y H ^ ^ ^ c^ ^ c C <-r^ H-H ^ O s 1/3 C/3 ’S) 2 o o u o (N (U w .5 "O l^^li * i i a (o ^ t: > > •' o «3 o ^ o- -i 3 -o ^ r- (li C3 t? O l> § = 3 c3 -C: -O C3 ^ ^ 2 1/ W s ^ !=^T3 2^5 3 ^ p O O 3 ^ (U rj cd -a U QJ ^ c/3 g 3 n ^ 2 2 o ^ td &0 x; ^ o o c 2 -i£ o '-S '2 3 cd c c/3 ^ ^ -d "“ > <+H D C ° 1 - g a S -i o o (U -o -3 2 cj C c ^ ^ c d C d 5 3 73 ^ C ^ Q .2 o ^ -o T3 2 II -1 i '2 I ^ ^ ^ o C o OJ 3 3 -d 2 ^ ^ ^ w 00 ^ > ^ 2 ^ g S C/3 P ^ C (L) C _ T3 O c/3 (1) "d (u o d t3 3 d .2 ^ Um ^ •S I ^ y I w ^ -*^ C/3 C3 r,> w W [JLl t/5 (L> c/D = d 3 ^ d ^3: ^ 2 2 d o 3 2 o o. I ^ 1 ■— 1 3 ^ ^ d 03 ^ d O 3= < d d ^ C! H ^ d -o o c 3: d- O' d- tX) r-- in (d (d d d d ON 0 ON m 0 rn 0 0 0 m ro d d d d d d d ' — ' ' — ' ' — ' m «n (d (L) 0 (U ■0 > 13 > > T3 > 3 0 3 *3 0 3 3 0 3 d E OJ g X. 0 S t; Lh ^ m 0 s 0 ° bO 2 bJO c/3 Q u 0 CQ S 3 3 T3 -2 cx Cu w > Skagen et al. • NEST SURVIVAL IN PRAIRIE FRAGMENTS 29 1 0.6 - 1 2 3 4 5 6 7 Ln (patch size, ha) FIG. 1. Daily survival of artificial nests increased relative to ln(patch size) across 26 grassland patches in Washington County, Colorado, 2000. Artificial nest survival increased with patch area up to about 65 ha (ln65 is approximately 4.2). Artificial nest survival increased with patch area up to about 65 ha and differed little at larger patch sizes (Fig. 1; note that ln65 is approximately 4.2). The strength of the rela- tionship between patch area and daily nest survival is indicated by whether the 95% Cl overlaps zero (Table 2). The 95% Cl around the effect estimate for patch area^ did not in- clude 0 for the best model and slightly over- lapped zero for the model-averaged estimate (that incorporates model-selection uncertain- ty). Nest survival increased as overall vege- tation structure (VegStruc, a function of cover, height, and density) decreased, as indicated by the negative coefficients for the explanatory variable in the model-averaged estimate (Ta- ble 2); this relationship, however, is weak, as indicated by the extent of overlap of the 95% CT with zero. Nest success of Lark Buntings and Horned Larks. — We found 36 Lark Bunting nests in 15 sites and 46 Horned Lark nests in 16 sites. Mean clutch size was 4.4 ± 0.17 (/? = 22) and 3.4 ± 0.12 (/; = 33) and number of young Hedged per successful nest was 2.9 ± 0.26 (/; = 15) and 2.8 ± 0.25 (/? = 13) I'or Lark Bun- tings and Horned Larks, respectively. Daily survival rates of I. ark Bunting and Horned Lark nests across all sites were 0.891 ± 0.022 (95% Cl = 0.847-0.935) and 0.9(K) ± 0.017 (95% Cl = 0.867-0.933). Overall nest surviv- al was low, with only 10% of Lark Bunting nests and I 1% of Horned I. ark nests Hedging at least one young. N(^ nests were censored from analyses due to suspected abandonment. Predator sightings in the grassland sites in- cluded ground squirrels, snakes, coyotes, striped skunks, and badgers. The total area searched by rope-dragging during the season was 1,890 ha; 42% of this effort was within 50 m of site edges. Only 12 Lark Bunting and 6 Horned Lark nests were found within 50 m of the edge, which were fewer than expected if we assumed nest dis- tribution to be random or uniform relative to habitat edges (x^ = 5.6, df = 1, P < 0.010, and x" = 14.58, df = 1, P < 0.001 for Lark Buntings and Horned Larks, respectively). We chose patch area to represent area in the candidate models for Lark Buntings and Horned Larks because the quadratic form did not improve model performance (AIC^ values differed by only 0.65 and 0.04 for Lark Bun- tings and Horned Larks, respectively) and the use of patch area offered greater parsimony. Daily survival of both Lark Bunting and Horned Lark nests was best explained by patch area alone (Table 1). For both species, nest survival decreased with increasing patch area, as indicated by the negative coefficients (P) for the explanatory variable in best models and model-averaged estimates (Table 2). For Lark Buntings, the 95% Cl on the effect es- timate for patch area did not include 0 (Cl = —0.85, —0.02) in the best model but did slightly overlap zero with its model-averaged estimate (Table 2). In contrast, the 95% Cl for Horned Larks barely overlapped zero in the best model and overlapped zero more so with the model-averaged estimate. The relative im- portance of patch area in iuHuencing natural nest survival was stronger for Lark Buntings (^H - = 0.775) than for Horned Larks = 0.546). Edge and VegSlruc had substantially smaller summed weights. An alternative approach to examining patch-size effects on natural nest survival for this data set is to compute standard Maylield (1975) estimates for grassland patches grouped as small (<80 ha) and large (>8() ha). Although not within the information-the- oretic paradigm, the results of this analysis yielded similar results ( fable 3). Nest survival was greater in small than in large patches for both species, with a somewhat stronger effect for Lark Buntifigs tlum for Horned I. arks. 30 THE WILSON BULLETIN • Vol. 1 17, No. I, March 2005 TABLE 3. Daily survival rates (SE, 95% Cl) for Lark Bunting and Horned Lark nests were greater in small (<80 ha) than in large (>80 ha) grassland patches in Washington County, Colorado, summer 2000. Lark Bunting Horned Lark Grassland patch size n Daily survival rate (SE) 95% Cl Daily survival rate (SE) 95% Cl Small ( <80 ha) 15 0.925 (0.026) 0.874-0.975 25 0.912 (0.020) 0.873-0.952 Large (> 80 ha) 21 0.851 (0.038) = 6.94, P < 0.001 0.776-0.925 21 0.881 (0.029) /45 = 4.19, P < 0.001 0.824-0.937 DISCUSSION Ejfects of prairie fragmentation on nest sur- vival— In this study, survival of artificial nests increased with increasing patch size. This finding is consistent with general expectations of the effects of patch size on nest survival and with findings of grassland studies that in- corporated patch sizes below 31 ha (Johnson and Temple 1990, Burger et al. 1994, Clawson and Rotella 1998, Winter et al. 2000). Grass- land studies with minimum patch sizes ex- ceeding 50 ha, however, found no effect of patch size on predation rates of artificial nests (Pasitschniak-Arts et al. 1998, Howard et al. 2001). Our finding of a positive relationship be- tween artificial nest survival and patch size, however, is the opposite of our findings on the survival of natural nests. Nests of Lark Bun- tings and Horned Larks had lower survival in the more extensive grassland patches in our study area. Ours is not the only study to doc- ument this unexpected trend. Higher daily sur- vival was experienced by Baird’s Sparrows {Ammodramus bairdii) in smaller patches of mixed-grass prairie (S. K. Davis pers. comm.), by several species of forest birds in forest fragments in western United States (Cavitt and Martin 2002), and by American Redstarts {Setophaga ruticilla) breeding in small, iso- lated stands of quaking aspen (Populus trem- uloides-, S. J. Hannon pers. comm.). Understanding the effects of fragmentation on predator communities. — Predator commu- nities exert a strong influence on avian fecun- dity. Numerous authors recently have sug- gested that effects of fragmentation on avian fecundity are highly complex and depend on predator dynamics within local landscapes, varying predator responses to fragmentation, and extent of fragmentation (e.g., Tewksbury et al. 1998, Heske et al. 2001, Patten and Bol- ger 2003). In general, the response of nest predators to fragmentation is complex, taxon- specific, and landscape context-dependent (Chalfoun et al. 2002). Further, there are even within-species differences in responses to fragmentation and land conversion; for ex- ample, swift foxes in eastern Colorado and Wyoming tend to avoid agricultural lands (Finley 1999), whereas they do not do so in Kansas (Sovada et al. 2001b). Once it is clearly acknowledged that pred- ator communities differ across locales and re- gions, and that predator species differ in their hunting strategies and responses to habitat fragmentation (Chalfoun et al. 2002), there should be less expectation of clear and con- sistent relationships between fragmentation metrics and fecundity. Rather than simply ask- ing what are the effects of fragmentation (de- gree of fragmentation, type of matrix, patch size, distance from edge) on avian fecundity, perhaps the pertinent questions should in- clude: (1) what are the effects of fragmenta- tion on predator communities, and (2) how do the resulting predator communities influence avian fecundity? We hypothesize that our unexpected find- ings (of lower survival of natural nests with increasing patch area and different trends be- tween artificial and natural nests) are due to differing composition of predator communi- ties relative to patch sizes. Although we did not quantify predator populations, we did find patterns in artificial nest destruction relative to patch size that suggest that predator compo- sition differs with patch size. The proportion of disturbed nests with broken quail eggs (rather than missing quail eggs or disturbed clay eggs) increased with increasing patch size (F, 23 = 6.340, P = 0.019). It is likely that one (or just a few) predator species are responsible for the broken eggs, assuming that egg handling varies between predator species and is consistent within species. Skagen et al. • NEST SURVIVAL IN PRAIRIE ERAGMENTS 31 Additional information to support that pred- ator community composition differs with patch size is the variation in home-range sizes and area-sensitivity of local predators. The small grassland patches may be devoid of the larger mammalian predators because small patches provide insufficient habitat not com- pensated for by use of the matrix (agricultural fields). That mammalian predators are absent or in lower densities in the matrix habitat than in the grassland habitats is suggested by lower predation rates on Mountain Plover {Charad- rius montanus) nests in agricultural fields than in native prairie (F. L. Knopf and V. J. Dreitz pers. comm.), by small mammal movements out of barren cropland (Streubel and Fitzger- ald 1978, Cummings and Vessey 1994), and by lower security of den sites in tilled agri- cultural lands. All of our grassland patches, even the smallest 7-ha patch, contained thirteen-lined ground squirrels (average home range = 1-5 ha; Streubel and Fitzgerald 1978) and snakes. We suspect that only the larger patches are frequented by the larger mammalian carni- vores, such as badgers (mean home range = 725 ha; Long 1973), striped skunks (mean home range = 378-512 ha; Wade-Smith and Verts 1982), coyotes (mean home range = 19.8 km^; Kitchen et al. 1999), and possibly swift foxes (mean home range = 7.6 km^; Kitchen et al. 1999). Additionally, densities of thirteen-lined ground squirrels may be greater in the smaller fragments; if larger predators are absent, numerical increases of ground squirrels may occur in a process similar to “mesopredator release” (Crooks and Soule 1999, Heske et al. 2001). This reasoning is consistent with Vander Haegen et al. (2002), who report that the composition of predator communities differs between fragments and I contiguous tracts of shrubsleppe habitat. Our study and other recent studies have demonstrated that trends in mortality of arti- ficial nests do not always mimic trends of nat- ural nests (Valkama et al. 1999, Zanette 2002, Mezquida and Marone 2003). riiese discrep- ancies may be due to ditferences in predator communities between treatments and the ways in which individual predators respond to ar- tificial and natural nests. L'ggs in artificial I nests cannot be camoullaged by incubating I adults or protected by the defensive actions of parents. In natural nest trials, on the other hand, parental presence can either attract or deter nest predators. Adult Lark Buntings, and probably Horned Larks, can deter ground squirrel nest predation; several Lark Buntings have been filmed chasing ground squirrels from their nests (J. B. Barna and A. S. Chaine pers. comm., but see Pietz and Granfors 1994). We also commonly witnessed adults of both species chasing ground squirrels. Paren- tal behavior and scent may attract the larger mammalian predators, but nest defense prob- ably cannot deter them. The idea that small grassland patches have greater densities of small predators or ground squirrels, which search for nests randomly, is consistent with our finding of lower survival of artificial nests in smaller patches. Likewise, the idea that larger patches have more predators that use cues of adults to find nests rather than random search is consistent with our finding of lower survival of natural nests in larger patches. Implications for management. — For man- agement to be effective in reversing popula- tion declines in grassland birds, the ultimate factors underlying the declines must be iden- tified and addressed. Even if it is determined that low reproductive success due to predation in breeding areas is a primary driver of pop- ulation declines, the available management tools are not extensive. Predator control as a means of improving reproductive success of songbirds is generally not advocated because removal of one subset of predators at a local site is compensated for by numerical increases or changes in foraging habits of another subset (Reitsma et al. 1990; Dion et al. 1999, 2()()(); Heske et al. 2001). Manipulations of habitat features at a local scale, although labor-inten- sive and costly, have met with some success in improving avian reproductive output (Morse and Robinson 1999, Heske et al. 2001. Sovada et al. 2001a). Current recommendations for acquisition, restoration, and management of forest and grassland habitats are often based on patch size (Robinson et al. 1995, Heske et al. 2001 ), and landscai'ie manipulations often include the protection and consolidation of large habitat tracts, fhis aj-iproach is justilictl by the many studies with positive relationshij'is between forest area and bird abuiulance and/or nest survival anti is especially applicable to laiul- 32 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 scapes with considerable native habitat re- maining. We question, however, as do others (Friesen et al. 1999, Bakker et al. 2002, Cavitt and Martin 2002, Patten and Bolger 2003), whether the effects of habitat fragmentation can be generalized across regions, landscapes, and habitats — and whether the protection of only large habitat tracts is the best approach in all areas. The value of small habitat patches in agricultural landscapes is often overlooked (Friesen et al. 1999); even small patches can function as population sources in some years (S. J. Hannon pers. comm.). We do not ques- tion the value of extensive grasslands nor jus- tify further fragmentation of native grassland, but we do encourage additional incentive pro- grams for habitat conservation of small patch- es, when appropriate, in fragmented agricul- tural landscapes. ACKNOWLEDGMENTS T. Cronk, B. Lamont, H. D. Lyons, and A. Maurer provided field assistance. We thank participating land- owners of Washington County for allowing us to con- duct research on their property. S. L. Haire and T. Giles provided GIS support. B. S. Cade offered statistical advice. S. K. Davis, V. J. Dreitz, S. J. Hannon, P. L. Kennedy, S. Kettler, and three anonymous referees provided comments on earlier drafts of the manuscript. The study was funded by the U.S. Geological Survey. LITERATURE CITED Akaike, H. 1973. Information theory as an extension of the maximum likelihood principle. Pages 267- 281 in Second International Symposium on Infor- mation Theory (B. N. Petrov and E Csaki, Eds.). Adademiai Kiado, Budapest, Hungary. Ambuel, B. and S. a. Temple. 1983. Area-dependent changes in the bird communities and vegetation of southern Wisconsin forests. Ecology 64:1057- 1068. Baicich, P. j. and C. j. O. Harrison. 1997. A guide to nests, eggs, and nestlings of North American birds, 2nd ed. Academic Press, San Diego, Cali- fornia. Barker, K. K., D. E. Naugle, and K. E Higgins. 2002. Incorporating landscape attributes into mod- els for migratory grassland bird conservation. Conservation Biology 16:1638-1646. Bollinger, E. K. and P. V. Switzer. 2002. Modeling the impact of edge avoidance on avian nest den- sities in habitat fragments. Ecological Applica- tions 12:1567-1575. Brittingham, M. C. and S. A. Temple. 1983. Have cowbirds caused forest songbirds to decline? BioScience 33:31-35. Burger, L. D., L. W. Burger, Jr., and J. Eaaborg. 1994. Effects of prairie fragmentation on preda- tion on artificial nests. Journal of Wildlife Man- agement 58:249-254. Burke, D. M. and E. Nol. 1998. Influence of food abundance, nest-site habitat, and forest fragmen- tation on breeding Ovenbirds. Auk 1 15:96-104. Burnham, K. P. and D. R. Anderson. 2002. Model selection and inference: a practical information- theoretic approach, 2nd ed. Springer- Verlag, New York. Cavitt, J. P. and T. E. Martin. 2002. Effects of forest fragmentation on brood parasitism and nest pre- dation in eastern and western landscapes. Studies in Avian Biology 25:73-80. Chalfoun, a. D., E R. Thompson, III, and M. J. Rat- NASWAMY. 2002. Nest predators and fragmenta- tion: a review and meta-analysis. Conservation Biology 16:306-318. Clawson, M. R. and J. J. Rotella. 1998. Success of artificial nests in CRP fields, native vegetation, and field borders in southwestern Montana. Jour- nal of Pield Ornithology 69:180-191. Crooks, K. R. and M. E. Soule. 1999. Mesopredator release and avifaunal extinctions in a fragmented system. Nature 400:563-566. Cummings, J. R. and S. H. Vessey. 1994. Agricultural influences on movement patterns of white-footed mice (Peromyscus leucopus). American Midland Naturalist 132:204-218. Delisle, J. M. and J. A. Savidge. 1996. Reproductive success of Grasshopper Sparrows in relation to edge. Prairie Naturalist 28:107-113. Diamond, J. M. and R. M. May. 1981. Island bioge- ography and the design of nature reserves. Pages 228-252 in Theoretical ecology: principles and applications, 2nd ed. (R. M. May, Ed.). Blackwell, Oxford, United Kingdom. Dion, N., K. A. Hobson, and S. Lariviere. 1999. Ef- fects of removing duck-nest predators on nesting success of grassland songbirds. Canadian Journal of Zoology 77:1801-1806. Dion, N., K. A. Hobson, and S. Lariviere. 2000. In- teractive effects of vegetation and predators on the success of natural and simulated nests of grassland songbirds. Condor 102:629—634. Donovan, T. M., P. W. Jones, E. M. Annand, and E R. Thompson, III. 1997. Variation in local-scale edge effects: mechanisms and landscape context. Ecology 78:2064-2075. Donovan, T. M. and R. H. Lamberson. 2001. Area- sensitive distributions counteract negative effects of habitat fragmentation on breeding birds. Ecol- ogy 82:1170-1179. Donovan, T. M., E R. Thompson, III, J. Eaaborg, and J. R. Probst. 1995. Reproductive success of mi- gratory birds in habitat sources and sinks. Con- servation Biology 9:1380—1395. Fahrig, L. and G. Merriam. 1994. Conservation of fragmented populations. Conservation Biology 8: 50-59. Finley, D. J. 1999. Distribution of the swift fox (Vul- Shagen et al. • NEST SURVIVAL IN PRAIRIE FRAGMENTS 33 pes velox) on the eastern plains of Colorado. M.A. thesis, University of Northern Colorado, Greeley. Freemark, K. E., J. B. Dunning, S. J. Hejl, and J. R. Probst. 1995. A landscape ecology perspective for research, conservation, and management. Pag- es 381-427 in Ecology and management of Neo- tropical migratory birds (T. E. Martin and D. M. Finch, Eds.). Oxford University Press, New York. Friesen, L., M. D. Cadman, and R. J. MacKay. 1999. Nesting success of Neotropical migrant songbirds in a highly fragmented landscape. Conservation Biology 13:338-346. Gates, J. E. and L. W. Gysel. 1978. Avian nest dis- persion and fledging success in field-forest eco- tones. Ecology 59:871-883. Hazler, K. R. 2004. Mayfield logistic regression: a practical approach for analysis of nest survival. Auk 121:707-716. Herkert, j. R. 1994. The effects of habitat fragmen- tation on Midwestern grassland bird communities. Ecological Applications 4:461-471. Herkert, J. R., D. L. Reinking, D. A. Wiedenfeld, M. Winter, J. L. Zimmerman, W. E. Jensen, E. J. Finck, et al. 2003. Effects of prairie fragmenta- tion on the nest success of breeding birds in the midcontinental United States. Conservation Biol- ogy 17:587-594. Heske, E. j., S. K. Robinson, and J. D. Brawn. 2001. Nest predation and Neotropical migrant songbirds: piecing together the fragments. Wildlife Society Bulletin 29:52-61. Howard, M. N., S. K. Skagen, and P. L. Kennedy. 2001. Does habitat fragmentation influence nest predation in the shortgrass prairie? Condor 103: 530-536. Johnson, D. H. 1979. Estimating nest success: the Mayfield method and an alternative. Auk 96:651- 661. Johnson, D. H. 2002. The importance of replication in wildlife research. Journal of Wildlife Management 66:919-932. Johnson, R. G. and S. A. Temple. 1990. Nest preda- tion and brood parasitism of tallgrass prairie birds. Journal of Wildlife Management 54:106-1 1 1. Kitchen, A. M., E. M. Gese, and E. R. Schauster. 1999. Resource partitioning between coyotes and swift foxes: space, time, and diet. Canadian Jour- nal of Zoology 77:1645-1656. Knopp, F! E. 1994. Avian assemblages on altered grass- lands. Studies in Avian Biology 15:247-257. Long, C. A. 1973. Taxidea taxus. Mammalian Species, no. 26. MacAkihur, R. H. and E. O. Wii son. 1967. riie the- ory of island biogeography. Princeton University Press, Princeton, New Jersey. Major, R. P7 and C'. E. Ki ndai.. 1996. Ihc contri- bution of artificial nest experiments to understaiul- ing avian reproductive sueeess: a review ol meth- ods anil conelusions. Ibis 1 38:298- 307. Mankin, P. C'. and K. Pi. Wnrni r. 1992. Vulnerability of grountl nests to predation on an agricultural habitat island in east-central Illinois. American Midland Naturalist 28:281-291. Manolis, j. C., D. E. Andersen, and F. J. Cuthbert. 2000. Uncertain nest fates in songbird studies and variation in Mayfield estimation. Auk 117:615- 626. Marzluff, j. M. and M. Restani. 1999. The effects of forest fragmentation on avian nest predation. Pages 155-169 in Forest fragmentation: wildlife and management implications (J. A. Rochelle, L. A. Lehmann, and J. Wisniewski, Eds.). Brill, Koln, Germany. Mayreld, H. 1975. Suggestions for calculating nest success. Wilson Bulletin 87:456-466. Mezquida, E. T. and L. Marone. 2003. Are results of artificial nest experiments a valid indicator of suc- cess of natural nests? Wilson Bulletin 115:270- 276. Morse, S. F. and S. K. Robinson. 1999. Nesting suc- cess of a Neotropical migrant in a multiple-use, forested landscape. Conservation Biology 13:327- 337. Murphy, M. T. 2003. Avian population trends within the evolving agricultural landscape of eastern and central United States. Auk 120:20-34. Pasitschniak-Arts, M., R. G. Clark, and F. Messier. 1998. Duck nesting success in a fragmented prai- rie landscape: is edge effect important? Biological Conservation 85:55-62. Patten, M. A. and D. T. Bolger. 2003. Variation in top-down control of avian reproductive success across a fragmentation gradient. Oikos 101:479- 488. Patton, D. R. 1975. A diversity index for quantifying habitat “edge.” Wildlife Society Bulletin 3:171- 173. PiETZ, P. J. AND D. A. Granfors. 1994. Identifying predators and fates of grassland passerine nests using miniature video cameras. Journal of Wildlife Management 64:71-87. Reitsma, R. R., R. T. Holmes, and T. W. Sherry. 1990. Effects of removal of red squirrels. Tamia- sciiirus hudsonicus. and eastern chipmunks. Tcnn- iiis siriatns, on nest predation in a northern hard- wood forest: an artificial nest experiment. Oikos 57:375-380. Robinson, S. K. 1998. Another threat posed by forest fragmentation: retiuced food supply. Auk 115:1-3. Robinson. S. K., E R. riioMPSoN. Ill, f. M. Donovan. D. R. Win 1 1, HEAD. AND .1. Eaaborg. 1995. Re- gional forest fragmentation and the nesting suc- cess of migratory birils. .Science 267:1987 1990. Samson, li B. and 1; Knopi . 1996. Prairie conserva- tion: preserving America's most endangereil eco- system. Island Press. Washington. D.C'. SAS iNsnii II . lN( . 1999. SA.S/SrAI users guide, ver. 8. SAS Institute. Inc., ('ary. North ('arolina. S\11R. .1. k.. .1. I:. IIINI s. AND J. I ailon. 2003. The North American Breeding Birtl .Sur\ey. results and analysis I9G6 2002. ver. 2003.1. U.S. Geo- 34 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 logical Survey Patuxent Wildlife Research Center, Laurel, Maryland. SovADA, M. A., R. M. Anthony, and B. D. J. Batt. 2001a. Predation on waterfowl in arctic tundra and prairie breeding areas: a review. Wildlife So- ciety Bulletin 29:6-15. SovADA, M. A., C. C. Roy, and D. J. Telesco. 2001b. Seasonal food habits of swift fox {Vulpes velox) in cropland and rangeland landscapes in western Kansas. American Midland Naturalist 145:101- 1 11. Stanley, T. R. 2004. When should Mayfield model data be discarded? Wilson Bulletin 1 16:267-269. Streubel, D. P. and j. P. Eitzgerald. 1978. Spermo- philus tridecemlineatiis. Mammalian Species, no. 103. Tewksbury, J. J., S. J. Hejl, and T. E. Martin. 1998. Breeding productivity does not decline with in- creasing fragmentation in a western landscape. Ecology 79:2890-2903. Thompson, E R., Ill, T. M. Donovan, R. M. DeGraaf, J. Faaborg, and S. K. Robinson. 2002. A multi- scale perspective of the effects of forest fragmen- tation on birds in eastern forests. Studies in Avian Biology 25:8-19. Valkama, j., D. Currie, and E. Korpimaeki. 1999. Differences in the intensity of nest predation in the curlew Nwnenius arquata: a consequence of land use and predator densities? Ecoscience 6: 497-504. Vander Haegen, W. M., M. A. Schroeder, and R. M. DeGraaf. 2002. Predation on real and artifi- cial nests in shrubsteppe landscapes fragmented by agriculture. Condor 104:496—506. Wade-Smith, J. and B. J. Verts. 1982. Mephitis me- phitis. Mammalian Species, no. 173. Walters, J. R. 1998. The ecological basis of avian sensitivity to habitat fragmentation. Pages 181- 192 in Avian conservation: research and manage- ment (J. M. Marzluff and R. Sallabanks, Eds.). Island Press, Washington, D.C. Westerskov, K. 1950. Methods for determining the age of game bird eggs. Journal of Wildlife Man- agement 14:56-67. Wiens, J. A. 1995. Habitat fragmentation: island v landscape perspectives on bird conservation. Ibis I37:S97-S104. Winter, M. and J. Faaborg. 1999. Patterns of area sensitivity in grassland-nesting birds. Conserva- tion Biology 13:1424-1436. Winter, M., D. H. Johnson, and J. Faaborg. 2000. Evidence for edge effects on multiple levels in tallgrass prairie. Condor 102:256-266. Zanette, L. 2002. What do artificial nests tell us about nest predation? Biology Conservation 103:323- 329. Wilson Bulletin 117(1):35^3, 2005 COMPARISON OF DAILY AVIAN MORTALITY CHARACTERISTICS AT TWO TELEVISION TOWERS IN WESTERN NEW YORK, 1970-1999 ARTHUR R. CLARK,i COLLEEN E. BELL, 2 AND SARA R. MORRIS^ 23 ABSTRACT. — Recent increases in the demand for communication towers have renewed interest in the impact of these towers on birds, particularly during migration. The objective of this study was to investigate avian mortality at two television towers (WGRZ and WKBW) in western New York from 1970 through 1999. Daily mortality totals ranged from 1 to 1,089 birds. The majority of the kill events were small, involving 10 or fewer birds; however, the majority of birds died in larger kill events. Both kill events and the numbers of individuals salvaged peaked in September. Patterns in avian mortality at the towers that we studied were consistent with normal migration events, during which the number of birds migrating varies substantially between nights. The two towers differed significantly in kill characteristics. At the WGRZ tower, median daily mortality generally ranged from 1 to 10 birds and was usually lower than at the WKBW tower. The size of kill events varied across the 3 decades, with no very large kill events (>500 birds) occurring in the 1990s. Because most birds salvaged in the 1970s and 1980s were killed in medium and large kill events, the absence of any very large kill events in the 1990s could explain the previously published decline in birds salvaged at these towers. Received 24 May 2004, accepted 7 February 2005. Although the Migratory Bird Treaty Act of 1918 prohibits human interference with mi- gratory birds, lighted man-made structures, such as communication towers, have been re- sponsible for the deaths of many nocturnal mi- grants (Avery et al. 1980). Avian mortality at communication towers (tower kill) results from collisions of birds with the towers them- selves or their supporting guy cables. In the United States, there are more than 83,000 tow- ers (Federal Communications Commission 2004), and the number of tower kills is likely to increase as tower construction continues. Many factors affect the number of nocturnal migrants colliding with towers, including den- sity of migrants aloft, weather, tower location and elevation, tower height, number and lo- cation of guy cables, and lighting. Northerly winds spur bird migration in the fall, and overcast conditions may disorient birds, re- sulting in their gravitation toward lighted tow- ers (Clark 1973). Only a few long-term studies have docu- mented the effects of specific towers on avian mortality. Crawford and Pfiigstrom (2001 ) not- ed that the pattern of avian mortality they wit- ' Buffalo Museum ol .Science, 1020 llumbolclt I’kwy., Buffalo. NY 1421 I. USA. - Dept, of Biology, C’anisius College. 2001 Maiti .St.. Buffalo, NY 14208. USA. ' C'onespoiuling author; e-mail; morriss Co'' can isius.edu nessed at a northern Florida television tower was “distinctly seasonal,” with most of the kill events occurring during fall migration. In a study of tower mortality in western New York and Ohio, Morris et al. (2003) docu- mented a signiheant decline in the number of salvaged birds over a 30-year period. This de- crease could result from fewer kill events, smaller kill events, or both. The goal of our study was to examine pat- terns of avian mortality at two television tc:>w- ers in western New York. Specihcally, we documented temporal patterns in the kill events, both within the autumnal migratory period and among the last 3 decades. METHODS We examined fall avian mortality at two television towers in southern Erie County dur- ing the 30-year period from 1970 to 1999. The WGRZ tower is located in Wales, New York (78"33'N, 42°43'W); it is 261 m tall, not including a 32-m antenna, and v\as erected in 1968. riiis tower sits at an ele\ation of 412 m asl and is supportetl by 13 guy cables. Ad- ditionally, it is illuminated at night by three levels of constantly burning, red obstruction- warning lights (three lights jK'r level, I 16 watts each) aiul three levels of slowly Hash- ing, red beacon lights (1.240 or 1.400 watts each). Ihe WKBW tower is located in C'ol- den. New York (78°37'N, 42°38'W); it is 33 36 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 TABLE 1. Annual variation in fall migration, 1970-1999. daily avian kill events at two television towers in western New York during Year WGRZ WKBW Number of visits Number of kill events Median^ Range Total no. of birds killed Number of visits Number of kill events Median^ Range Total no. of birds killed 1970 NA^’ 18 14.5 1-630 1,828 NA^ 12 14.5 1-90 240 1971 67 23 11 1-361 852 67 28 5 1-72 434 1972 NA^’ 9 5 1-98 174 NA*’ 2 4.5 2-7 9 1973 NA^’ 11 5 1-88 158 NAf’ 8 7 1-17 69 1974 NA^’ 15 9 1-51 237 NA^’ 8 27.5 1-307 829 1975 NA*’ 9 38 3-458 1,066 NA'’ 8 64 3-686 1,312 1976 17 14 8.5 1-110 304 12 8 13.5 2-55 170 1977 15 10 7.5 1-170 391 13 11 5 1-445 1,026 1978 27 12 10 1-70 209 13 8 4 1-114 171 1979 25 14 6 1-63 179 15 15 9 1-138 345 1980 29 13 9 1-135 331 15 9 4 1-659 984 1981 13 5 5 1-100 116 6 4 12.5 1-91 117 1982 24 19 13 1-437 1,189 18 15 35.5 1-1,089 3,306 1983 21 7 2 1-76 97 11 3 11 3-23 37 1984 16 12 3 1-42 116 9 5 22 1-98 178 1985 20 9 4 1-68 173 8 4 45.5 1-159 251 1986 17 6 4 1-40 63 7 3 11 6-1 13 130 1987 12 1 1 1 1 5 4 1.5 1-42 46 1988 10 4 7 3-98 115 7 4 17.5 1-262 298 1989 12 3 1 1-72 74 5 3 58 2-332 392 1990 16 9 4 1-43 83 8 5 22 2-65 140 1991 13 5 1 1-8 19 4 2 5 1-9 10 1992 10 4 I 1-2 5 2 1 1 1 1 1993 8 6 3 1-60 75 4 3 6 3-15 24 1994 12 6 1 1-15 23 3 2 37.5 12-63 75 1995 10 7 2 1-10 20 4 3 2 1-3 6 1996 12 8 3 1-13 36 9 5 28 2-294 426 1997 12 7 1 1-10 26 5 3 3 1-9 13 1998 15 8 1 1-3 12 5 2 1 1 2 1999 23 11 3 1-13 45 13 7 5 1-23 51 Total 518 285 4c 8,017 306 195 6^ 11,092 ^ Median number of birds collected after nights with kill events (nights with no birds were excluded). *’The number of days visited without finding birds was not recorded in the early 1970s. Overall median was based on all kill events, not on annual medians. 305 m tall, not including a 23-m antenna, and was erected in 1958. This tower sits at an el- evation of 529 m asl and is supported by 18 guy cables. The WKBW tower has four levels of red obstruction-warning lights and four lev- els with red beacon lights and is located ap- proximately 8 km south-southwest of the WGRZ tower. Both towers are a lattice of steel, and triangular in cross-section, typical of many television and radio towers. Both tower sites have paved driveways, small park- ing lots, and transmitter buildings. Immediate- ly surrounding the facilities are grass lawns cut lower than surrounding grass. At WKBW, the taller grass helds were cut in early fall during most years of the study. At WGRZ, there were larger areas of cut grass and pave- ment to the south of the tower. The taller grass helds were used as pasture in the early years of the study, with occasional cuttings in the later years. With the assistance of volunteers, ARC sal- vaged birds from the WGRZ and WKBW towers. Visits to towers generally occurred from late August to early November, follow- ing nights with overcast or mostly overcast skies and with northerly winds or winds be- coming northerly. Although records were kept of most visits during which no salvaged birds were recovered, this information was more thoroughly documented after 1975 (Table 1). The search procedure involved checking the Clark et al. • TELEVISION TOWER MORTALITY 37 TABLE 2. Top five families of birds killed at two television towers in western New York, 1970-1999. Most of the birds salvaged at both towers were mem- bers of Parulidae, Turdidae, Vireonidae, and Reguli- dae. Total birds killed at each tower by family WGRZ WKBW 5,055 Parulidae 7,410 Parulidae 1,030 Turdidae 1,694 Turdidae 689 Vireonidae 1,086 Vireonidae 624 Regulidae 346 Regulidae 337 Emberizidae 207 Mimidae paved and grassy areas around the towers for birds by walking in loops (ranging out to ap- proximately 50 m at WGRZ and 60 m at WKBW) through the lower-cut grass lawns and by walking straight lines under the guy cables to about 65 m from the base of the tower, and by returning about 2 m south of the cables. The searches included additional loops out into taller grass to approximately 30 m from the tower in the two southerly facing angles of the guy cables. Searchers increased coverage of grassy ar- eas when specimens were found, walking a series of parallel paths approximately 1 m apart on the lower-cut grass lawns. Searchers walked similar patterns in the taller grass, ex- tending well beyond the last specimen col- lected. Using binoculars, searchers also checked the angled roof of the WGRZ trans- mitter building for birds (Morris et al. 2003). To compare avian mortality across decades, we designated kill sizes as small (1-10 birds). medium (11-100 birds), and large (>100 birds). We used likelihood ratio chi-square tests to analyze differences in kill sizes be- tween towers and among decades at each tow- er, and differences in the number of individ- uals in kill events among the 3 decades. We examined temporal patterns during fall migra- tion by 10-day periods beginning 1 August. We salvaged birds between 12 August and 16 November, resulting in 10 pooling intervals. Because of limited collections in August and November, we combined the first two periods into a single initial interval, and the last two periods into a single final interval, resulting in eight intervals for statistical analysis. We pooled data across each decade to investigate temporal changes during the 30-year period. We present median kill sizes because distri- butions were not normal. All analyses were performed using SYSTAT (SPSS, Inc. 2002). Significance levels were determined after se- quential Bonferroni correction for multiple tests (Rice 1989), although uncorrected P-val- ues are presented. RESULTS From 1970 through 1999, 11,092 birds were collected at the WKBW-TV tower, and 8,017 birds were collected at the WGRZ-TV tower. At least one bird was salvaged most nights (WGRZ: 55.0%, n = 518; WKBW: 63.7%, n — 306), although nights on which no birds were collected were not always not- ed, particularly in the early 1970s (Table 1 ). The families represented most frequently were similar at the two towers (Table 2). The top TABLE 3. The most commonly killed avian York, 1970-1999. species were similar at two television towers in western New Species Total killed at WGRZ Species Total killed at WKBW Ovenbird (Seiurus aurocapilla) 907 Bay-breasted Warbler 1 .359 Magnolia Warbler (Dcndroica maf>tu>Ha) 555 Ovenbird 1 ,303 .Swainson's Thrush (Catharus iistiilatus) 531 Magnolia Warbler 986 Bay-breasted Warbler (Dcndroica castanea) 494 Swainson's riirush 865 Blackpoll Warbler (Dcndroica striata) 487 Red-eyed Vireo 806 Red-eyed Vireo (Virco olivaccns) 472 Black-lhroiitcd Blue Warbler 437 Golden-crowned Kinglet (Rcfpdus satrapa) 444 Blackpoll Warbler 405 Black-throated Blue Warbler (Dcndroica ,U8 renncssee Warbler (Vcnnivora 391 cacndcsccns) American Restart (Sctopliat’a rnticilla) 239 pcrct^rina) ('ommon Yellowthroat (Ccothlypis 366 Black-throated Green Warbler (Dcndroica vircns) 227 trie has ) Bkick-lhroaied Green Warbler 325 38 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 (A) Both towers 60 -1 c/) None Small (1-10) Medium (1 1-100) Kill size ■ WGRZ (n= 517) qWKBW (n = 329) Large (>100) (B) WGRZ Medium (11-100) □ 1970s (n = 213) ■ 1980s (n= 173) □ 1990s (n= 131) Large (>100) Kill size (C) WKBW 60 -| (/) O) 45 - None Small (1-10) □ 1970s (n= 179) ■ 1980s (n = 93) □ 1990s (n = 57) Medium (11-100) Large (>100) size EIG. 1. Kill events at two television towers in western New York, 1970—1999: (A) totals for each tower; (B and C) totals by decade for the WGRZ and WKBW towers. The majority of collections resulted in 100 or fewer birds killed during a single night. ten species killed at each tower represented >50% of the total individual birds killed, and all but one of these species were Neotropical migrants (Table 3). The number of birds killed per night ranged from 1 to 1,089 at WKBW and from 1 to 630 at WGRZ. Kill events on most nights involved 10 or fewer birds (Fig. 1). The median kill size (all years) was four at WGRZ and six at WKBW (Table 1). We detected a slight but significant difference in the proportion of small, medium, and large kill events between the two towers (x^ = 8.5, df = 2, F = 0.014; Fig. lA). The proportion of small, medium, and large kill events was dependent on decade (WGRZ: = 30.6, df = 4, P < 0.001; Clark et al. • TELEVISION TOWER MORTALITY 39 (A) Both towers ■ WGRZ (n= 8,017) □ WKBW(n= 11,092) Small (1-10) Medium (11-100) Kill size Large (>100) (B) WGRZ □ 1970s (n = 5,398) ■ 1980s (n = 2,275) □ 1990s (n = 344) Small (1-10) Medium (11-100) Kill size Large (>100) (C) WKBW CO 100 1 ■Q 5 80 - o 60 - c CD O 40 - CL 20 - C3 1970s (n = 4,605) ■ 1980s (n= 5,739) □ 1990s (n=748) Small (1-10) Medium (1 1-100) Kill size Large (>100) FIG. 2. Birds salvaged at two television towers in western New York. 1970-1999; (A) percent salvaged at each tower; (B and C) percent salvaged by decade for the WGRZ and WKBW towers. A relatively small percentage of salvaged birds was collected after nights when kill sizes were small (10 or fewer). WKBW: X" = 10.0, elf = 4, P = ().()40), with a higher proportion of small kill events in the 1990s at both towers (h'ig. IB, C). Although most kill events involved 10 or fewer birds, the majority of birds were sal- vaged after medium to large kill events (>I0 birds; Fig. 2). Fhe majority of indivitluals were killed in large evetits during the 1970s and 1980s at both towers, while the majority of individuals were killed in small and medi- um events in the 1990s (WCiR/: X' ~ 987.7. d| = 4, /^ < ().()() 1; WKBW': x“ = 1, 1 01.3. df = 4, P < 0.001: Fig. 2B, CO. During the 1990s, there were substantially fewer birds eolleeted overall, ami no single kill e\ent re- sulted in a very large kill (>300 iiuli\ iduals). Fhe largest kill event during that deeade al W'CiK/. was only Ci) birtls; only one kill e\ent was >100 birds al WKBW (294 birds on 10 .September 199fi). 40 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 (A) WGRZ Aug Aug Aug Sep Sep Sep Oct Oct Oct Nov Nov Nov (B) WKBW EIG. 3. Kill events (%) by 10-day salvage intervals at two television towers in western New York, 1970- 1999. At both towers, the largest percentage of nights during which birds were killed occurred during September. Kill events occurred throughout autumn mi- gration, with most occurring during Septem- ber (Fig. 3). The proportion of kill events by 10-day salvage interval did not differ among the 3 decades (WGRZ: x" = 20.1, df = 14, P = 0.126; WKBW: = 25.9, df = 14, P = 0.027; not significant after Bonferroni correc- tion). Similar to the timing of kill events, the largest proportion of migrants was salvaged in September (Fig. 4). In the 1970s and 1980s, the largest kill events occurred in mid-Sep- tember, while in the 1990s, the largest kill events occurred in early September. This pat- tern was observed at both WGRZ and WKBW; additionally, the proportion of sal- vaged birds by 10-day interval differed among the 3 decades (WGRZ: x" = 926.2, df = 14, P < 0.001; WKBW: x^ = 2,583.8, df = 14, P < 0.001). These analyses are dependent on the timing of visits to the tower sites; thus, we investigated whether the timing of visits var- ied across the 3 decades. We found no differ- ence in the proportion of visits to towers by 10-day salvage interval for both towers (WGRZ: likelihood ratio x^ = 12.7, df = 14, P = 0.22; WKBW: likelihood ratio x^ = 24.6, df = 14, P = 0.039; not significant after Bon- ferroni correction). The slight difference in the timing of visits at WKBW across the 3 de- cades was due to the highest percentage of visits occurring in mid-September in the 1990s (30.4% of all visits) versus late Septem- ber in the 1970s (19.3%) and 1980s (27.0%). DISCUSSION Avian mortality at towers may reflect not only the abundance of migrants, but also the weather conditions migrants experience. Fur- thermore, individual communication towers appear to differ in their impact on migrants. Clark et al. • TELEVISION TOWER MORTALITY 41 (A) WGRZ Aug Aug Aug Sep Sep Sep Oct Oct Oct Nov Nov Nov (B) WKBW FIG. 4. Salvaged birds (%) by 10-day intervals at two television towers in western New York, 1970-1999. Most birds were collected during September. Thus, finding dead birds at either tower in this study most likely indicated migration was oc- curring. However, even nights with appropri- ate wind conditions for migration (northerly) did not always result in substantial avian mor- tality. Most visits to both television towers re- sulted in the salvage of migrants. Although most visits resulted in the salvage of 10 or fewer birds, on some we recorded large kill events (>1()() birds). These results are similar to those from a study in northern Florida, in which small kill events occurred on more than 80% of days (Crawford and Engstrom 2001). IJkcwisc, Crawford and Faigstrom (2001) re- ported a very low percentage of very large kill events (0.1% of days resulted in the salvage of >500 individuals); the combination of ap- propriate wind conditions and cloud cover were necessary for substantial kill events (Clark 1973, Crawford and Faigstrom 2001). Nights with no birds salvaged were frequent in this study and may reflect a lack of migra- tion or weather conditions that were not con- ducive to tower kills. Crawford and Engstrom (2001) noted that more than 40% of birds were salvaged from kill events of 1 1-100 birds. Furthermore, al- though only one bird was salvaged after >30% of nights, only approximately 2% of all individuals were salvaged after those nights. Our results are similar in that only a \ery small percentage of birds were from salvages of single individuals, and most of the birds we salvaged were collected after medium (11- 100 birds) or large (>100 birds) kill events. We did find slight but significant differenc- es in the si/es of kill events between the two towers studied. Detailed comparisons of avian mortality can be hamj'icred by a number of variables whose effects may be diflicult or im- possible to isolate. 'Fhc two towers in this study, although structurally similar, dilTcr in 42 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 elevation at ground level, tower and antenna height above ground, number and placement of guy cables, building and grounds lighting, surrounding habitat, and proximity to other towers (Clark 1973, Morris et al. 2003). The WKBW tower had a higher proportion of large kill events than the WGRZ tower, was taller and located at a higher elevation, and had more guy cables. Previous work has documented that signif- icantly more birds were killed at these tele- vision towers in the 1970s and 1980s than in the 1990s (Morris et al. 2003). Thus, it is not surprising that the majority of individuals were salvaged from large kill events (>100 individuals) during the 1970s and 1980s. The decrease in the number of birds salvaged dur- ing the 1990s reflects the smaller kill events documented in the results presented here. Rea- sons for the decline in the number of birds salvaged remain unknown, although the de- clines may reflect a decline in migrant popu- lations (Goodpasture 1984), a change in weather patterns (Goodpasture 1984), selec- tion against lower-flying migrants, an increase in anthropogenic nocturnal lighting (Morris et al. 2003), and/or an increase in predation on the avian casualties at towers (Stoddard 1962, Goodpasture 1984, Crawford and Engstrom 2001). Peak kill events at both towers occurred in mid-September during the 1970s and 1980s, whereas during the 1990s, kill events peaked in early September. Likewise, the majority of individual birds were salvaged in mid-Sep- tember for both towers in the 1970s and 1980s, while in the 1990s the peak occurred in early September. Fall migration in western New York generally shows a peak in Septem- ber, particularly among Neotropical migrants (Buffalo Ornithological Society 2002). Be- cause there were few large kill events in the 1 990s (and, therefore, our salvage data for the 1990s are based only on small and medium kill events), our results may not reflect any real change in migration timing across de- cades. Although most tower kill events, particu- larly in recent years, have been small at in- dividual communication towers, the cumula- tive impact of small kill events at thousands of towers may greatly impact migrant popu- lations. Migration is an extremely hazardous period for birds. Among Black-throated Blue Warblers (Dendroica caerulescens), for ex- ample, approximately 85% of annual mortal- ity may occur during this period (Sillett and Holmes 2002). Many causes may contribute to mortality during migration, but clearly col- lisions with communication towers have an impact on migrant populations. It is speculat- ed that millions of birds are killed at com- munication towers annually, and this threat is expected to double in the next decade as the proliferation of communication towers contin- ues (Holden 2001). The relative impact of col- lisions with towers and other causes of mor- tality during migration require additional study. ACKNOWLEDGMENTS We would like to thank the many people involved in gathering specimens over the 30-year period. We especially thank WKBW and WGRZ television broad- casting companies and their personnel for allowing ac- cess to their transmitter sites. This research was gen- erously supported by the Buffalo Museum of Science (support of ARC), Buffalo Ornithological Society re- search grants to ARC, Canisius College (support of SRM and CEB), and a Howard Hughes Medical Insti- tute research internship to CEB. This manuscript was improved by the constructive comments of R. J. Mor- ris, M. C. Clark, and three anonymous referees. LITERATURE CITED Avery, M. L., R E Springer, and N. S. Dailey. 1980. Avian mortality at man-made structures: an an- notated bibliography (revised). U.S. Fish and Wildlife Service, Biological Service Program, FWS/OBS-80-54. Buffalo Ornithological Society. 2002. Seasonal checklist of the birds: the Niagara Frontier region. Buffalo Ornithological Society, Buffalo, New York. Clark, A. R. 1973. Avian mortality at three western New York television towers. M.A. thesis, Buffalo State College, Buffalo, New York. Crawford, R. L. and R. T. Engstrom. 2001. Char- acteristics of avian mortality at a north Florida television tower: a 29-year study. Journal of Field Ornithology 72:380-388. Federal Communications Commission. 2004. Antenna structure registration, http://wireless2.fcc.gov/ UlsApp/AsrSearch/asrAdvancedSearch.jsp (accessed 27 September 2004). Goodpasture, K. A. 1984. Television tower casualties, Nashville, Tennessee 1976-1983. Migrant 55:53- 57. Holden, C. 2001. Curbing tower kill. Science 291: 2081. Morris, S. R., A. R. Clark, L. H. Bhatti, and J. L. Clark et al. • TELEVISION TOWER MORTALITY 43 Glasgow. 2003. Television tower mortality of mi- grant birds in western New York and Youngstown, Ohio. Northeastern Naturalist 10:67-76. Rice, W. R. 1989. Analyzing tables of statistical tests. Evolution 43:223-225. SiLLETT, T. S. AND R. T. HoLMES. 2002. Variation in survivorship of a migratory songbird throughout its annual cycle. Journal of Animal Ecology 71: 296-308. SPSS, Inc. 2002. SYSTAT, ver. 10.2. SPSS, Inc., Chi- cago, Illinois. Stoddard, H. L., Sr. 1962. Bird casualties at a Leon County, Elorida TV tower, 1955-1961. Bulletin of the Tall Timbers Research Station, no. 1. Wilson Bulletin 1 1 7( 1 );44-55, 2005 A NEW MODEL TO ESTIMATE DAILY ENERGY EXPENDITURE EOR WINTERING WATERED WL RICHARD A. McKinney^ 3 and SCOTT R. MCWILLIAMS^ ABSTRACT. — Current models to estimate daily energy expenditure (DEE) for free-living birds are limited to either those that use fixed thermoregulatory costs or those that more accurately estimate thermoregulatory costs, but require extensive and often logistically difficult measurements. Here, we propose a model based on basal metabolic rate (BMR), activity budgets, and site-specific energetic costs of thermoregulation that requires only simple measures of ambient temperature and wind speed to provide estimates of DEE. We use the model to calculate the DEE of Buffleheads (Bucephala albeola) wintering at six habitats that afford differing degrees of protection from exposure within Narragansett Bay, Rhode Island. Bufflehead activity budget data collected during the winters of 2001-2002 and 2002-2003, along with average temperatures and wind speeds at the sites, were used to calculate DEE that ranged from 46.9 to 52.4 kJ/hr and increased with increasing wind speed. The energetic cost of thermoregulation composed as much as 28% of total DEE and increased with wind speed. Our DEE values were 13.4% higher, and thermoregulatory costs were up to 2X higher than those calculated using an existing model that incorporates fixed thermoregulatory costs. We also saw an increase in feeding activity with increasing wind speed; sensitivity analysis of the effects of wind speed and feeding activity showed that a 1 m/sec increase in wind speed at our sites increased DEE by 2.5%, whereas a corresponding increase in feeding activity increased DEE by 4.5%. This suggests that in temperate winter habitats, increased feeding activity may have a greater impact on Bufflehead DEE than wind exposure. Site-specific model estimates of DEE could also provide additional insight into the relative contribution of environmental conditions and changes in waterfowl behavior to DEE. Received 27 May 2004, accepted 12 January 2005. The daily energy expenditure (DEE) of a species is the sum of basal metabolic rate (BMR), thermoregulatory requirements, and the energetic cost of daily activities such as feeding, locomotion, and social behaviors. Quantitative assessments of the daily activities of wintering waterfowl have been used both to identify important habitats for these species and to assess their response to changes in hab- itat quality (Fredrickson and Drobney 1979, Brodsky and Weatherhead 1985a, Baldassarre et al. 1988, Paulus 1988). Waterfowl activity budgets may be influenced by habitat type (Turnbull and Baldassarre 1987, Rave and Baldassarre 1989) and site characteristics such as food abundance, protection from exposure, and level of disturbance (Nilsson 1970, Jorde et al. 1984, Paulus 1984, Quinlan and Baldas- sarre 1984, Brodsky and Weatherhead 1985b, Miller 1985). Changes in waterfowl activity may also be tied to changes in DEE that result ' U.S. Environmental Protection Agency, Office of Research and Development, National Health and En- vironmental Effects Research Lab., Atlantic Ecology Div., 27 Tarzwell Dr., Narragansett, RI 02882, USA. ^ Dept, of Natural Resources Science, Univ. of Rhode Island, Kingston, RI 02881, USA. Corresponding author; e-mail; mckinney.rick@epa.gov from the influence of habitat characteristics. For example, increased exposure to cold and wind may increase thermoregulatory energy costs, and therefore require increased feeding to offset higher energetic costs (Bennett and Bolen 1978, Hickey and Titman 1983). Mod- els that allow comparison between the ener- getic costs of thermoregulation and specific waterfowl behaviors could be used to deter- mine the relative magnitude of these costs, and may also provide insight into the effects of habitat quality on the DEE of resident wa- terfowl. Traditional measures of DEE for birds from time-activity budgets use multiples of BMR to estimate energetic costs of activities, but may differ in how the thermoregulatory com- ponent of DEE is estimated (Weathers et al. 1984). Early estimates of DEE included either a fixed cost of thermoregulation or one based solely on ambient temperature (Kendeigh 1949, Schartz and Zimmerman 1971, Koplin et al. 1980). Models subsequently evolved to include a means to more accurately estimate thermoregulatory costs, but only by the exten- sive measurement of many variables (e.g., whole-body thermal resistance, forced-con- vective resistance), some of which may be lo- gistically difficult to obtain for free-living 44 McKinney and McWilliams • WATERFOWL DEE MODEL 45 wildlife (Pearson 1954, Stiles 1971, Walsberg 1977). Weathers et al. (1984) proposed the use of standard operative temperature, or indices that allow single-number representations of complex thermal environments, to overcome some of these difficulties. However, while providing a much more rigorous estimate of thermoregulatory costs, this approach is lim- ited by the need for the construction and cal- ibration of taxidermic mounts, and may be best suited for aviary or well-controlled field applications. To date, researchers estimating DEE for free-living birds using published ac- tivity-based models are limited to either those that use fixed thermoregulatory costs or those that more accurately estimate thermoregula- tory costs, but at the expense of extensive and often logistically difficult measurements of many variables. Previous studies estimating DEE for win- tering waterfowl have employed models that use factorial increases of BMR and that as- sume a fixed cost of thermoregulation (Wool- ey and Owen 1978, Albright et al. 1983, Mor- ton et al. 1989, Parker and Holm 1990). For wintering waterfowl in northern areas exposed to low temperatures and high winds, thermo- regulation may compose as much as 80% of daily energetic costs (Ettinger and King 1980, Walsberg 1983). These costs may vary be- tween wintering habitats because of differing degrees of protection from exposure to wind and cold (Porter and Gates 1969, Goldstein 1983, Bakken 1992). If estimates of DEE are to be useful in assessing habitat quality for wintering waterfowl, they need to include some measure of the energetic cost of ther- moregulation based on local environmental conditions. Here, we present an activity-based model that includes habitat-specilic measures of ther- moregulatory costs to estimate DEE of water- fowl in different habitats. Our model requires only simple measures of ambient temperature and wind speed, along with waterfowl activity budgets and morphological measurements. Thermoregulatory costs are calculated by us- ing heat loss via conduction and convection as a function of temperature anti wiiul spcetl tt) estimate the metabolic heat protluctioii re- quired to maintain body temperature (Birkc- bak 1966, Goldstein 1983). Because of the ability to estimate site-specific D1T{ based on local conditions, the model may be useful in evaluating habitats that provide differing de- grees of protection from high winds and ex- treme temperatures. Model estimates could also be used to provide insight into the rela- tive contribution of environmental conditions and differences in waterfowl behavior to changes in DEE. In this study, we used our model to estimate the DEE of Buffleheads (Bucephala cilbeola) at six wintering habitats in Narragansett Bay, Rhode Island, that afford differing degrees of protection from exposure to wind and cold temperatures. Our specific objectives were to (1) compare estimates of DEE obtained using our model with those obtained using a previ- ously published model that incorporates a fixed cost of thermoregulation, and (2) ex- amine changes in DEE across the sites and determine the relative contribution of wind speed and waterfowl feeding behavior to changes in DEE. METHODS DEE site-specific thermoregulation mod- el.— Our model incorporating site-specific thermoregulatory costs into DEE for winter- ing Buffleheads (hereafter, SST model) con- sists of (1) a thermoregulatory component (EEjhermoreg) — cstimatc of thc mctabofic heat production required to balance heat loss from the bird to the environment through conduc- tion and convection, and (2) an activity com- ponent (EEAetivity) — at! estimate of additional energetic costs resulting from specific daily activities of wintering Buffiehead expressed as multiples of basal metabolic rate (BMR). We sum these components to arrive at an esti- mated DEE. In our model, metabolic heat pro- duction includes resting energy expenditure in a thermoneutral environment (i.e., BMR) and the additional energy expenditure required to maintain thermal equilibrium. The model uses average temperatures and wind speeds that co- incide with activity budget sampling at the sites: DEE is reported in k.I/hr. Basal metabolic rates were estimated from those ol’ 16 North American thick species summari/cd in McNab (2003). A plot of BMR versus botly mass for these species gave the relation: BMR 4.05M"^‘f where BMR is basal metabolic rate in ml (),/hr. aiitl M is body mass in g. L!sti males of BMR were con- 46 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 verted to kJ/hr using a conversion factor of 18.8 kJ/L O2, derived from the average com- position of the Bufflehead’s winter diet (Schmidt-Nielsen 1997). Body mass was ap- proximated at 450 g for males and 325 g for females (Gauthier 1993). Before calculating metabolic heat produc- tion, we first determined when this component of a Bufflehead’s DEE is necessary by com- paring ambient temperature with their lower critical temperature, or the temperature below which metabolic heat production is required to maintain body temperature (Schmidt-Niel- sen 1997). Lower critical temperature (LCT) was estimated by the empirical relation: LCT = 47. where LCT is in ° C, and M is body mass in g (Kendeigh 1977). We com- pared effective ambient temperature (T^^ or the ambient temperature corrected for the ef- fect of wind speed; Siple and Passel 1945) to LCT to determine whether metabolic heat pro- duction would be required to maintain the duck’s body temperature. If T^/ was less than LCT, we assumed that metabolic heat produc- tion was required to maintain body tempera- ture; we then calculated this energy require- ment and included it in the final DEE. On the other hand, if T^^ was greater than the lower critical temperature, we did not include met- abolic heat production. Effective temperature was calculated using the relationship derived by Siple and Passel (1945): Tef = T, - {T, - rj X (0.474 + 0.239 X Vu - 0.023 X w), where T^j is the effective temperature (° C) used for comparison with the lower critical temperature, T;, is body temperature (° C), T^, is ambient temperature (° C), and u is wind speed (m/sec). If T^f was less than LCT, we used an em- pirical model to estimate metabolic heat pro- duction as a function of temperature and wind speed (Goldstein 1983): where u is wind speed (m/sec) and is metabolic heat production (watts). The coef- ficient b is determined empirically from data summarized by Goldstein (1983) on seven species of birds (body size 13.5-3,860 g) by the relation: h = 0.0092M°^^ X where M is body weight in g and AT is the difference between lower critical temperature and ambi- ent temperature in ° C. The coefficient a is de- termined under conditions of free convection (u = 0.06 m/sec) by the relation: a = Hj- foVa06, where Hj is an adjusted metabolic rate in watts at ambient temperature (Goldstein 1983). We estimated Hj using a heat transfer model proposed by Birkebak (1966) that cal- culates conductive heat loss from different an- atomical regions of the bird to the environ- ment using geometrical representations (e.g., head represented as a sphere, body represent- ed as a cylinder) and heat transfer theory (Ap- pendix; Birkebak 1966). Morphological mea- sures of body dimensions (Eig. 1) can be ob- tained from the literature (e.g., Belrose 1980, Gauthier 1993) or from measurements of mu- seum specimens. Average values for live Buf- fleheads {n = 4, obtained from the Connecti- cut Waterfowl Trust, Earmington, Connecti- cut) and Bufflehead study skins {n = 16, ob- tained from the Harvard Museum of Comparative Zoology, Cambridge, Massachu- setts) are summarized in the Appendix. Also summarized in the appendix are the equations drawn from Birkebak (1966), which were used to calculate metabolic heat production. For these equations, a heat transfer coefficient {k) of 0.102 cal/cm/° C was used for the entire body surface (Calder and King 1974). The thermal conductance of Common Eider {So- materia mollissima) in water (i.e., wet thermal conductance) has been shown to be 57% greater than it is in the air (Jenssen et al. 1989); therefore, we used a heat transfer co- efficient of 0.160 cal/cm/° C to calculate heat loss from the ventral body surface to the wa- ter. Metabolic heat production was calculated as: BMR + Qhead Qneck Qbreast Qbody Q,e„.r3i surface, where BMR is basal metabolic rate and Q is the heat loss term for each body component. Estimates of additional energetic costs re- sulting from specific daily activities (EEActivity) were calculated by multiplying the proportion of time spent in a particular activity by the energetic cost of that activity. We used pre- viously reported multiples of BMR, summa- rized in Table 1, to calculate the energetic costs of activities by multiplying the propor- McKinney and McWilliams • WATERFOWL DEE MODEL 47 FIG. 1. Body dimension measurement points required for input into the SST model to estimate DEE (see Appendix). A = head length, B = head height, C = head width, D = body width, F = body length, G = body height, H = neck length, I = neck width, J = neck height. TABI.E 1. Energetic costs as a multiple of basal metabolic rate (BMR) of activities used in the site-specific and fixed-cost thermoregulation DEE models. Activity Opcratioiuil cletinition Multiple of BMR Retorenee Dive Diving for food 5.\ de Leeuw I9db Surface Surface and pause between dives .^.1 de Leeuw 199b Look Peering through the water at the cove bottom I.S Wooley and Owen I97S Courtship .Social tlisplay toward indi\ idual of the opposite gender 2.4 Albright et al. I9S.^ Agonistic Hostile interaction between two itidi\ idiuiK I.S Wooley and Ovsen I97S Switn I .ocomotion Butler 2()()() Fly Locomotion \2.5 Wooley and Owen I97S Preen Maintenance of feathers 2.1 Albright et al. I9S.^ Alert Not moving, but actively observitig surroundings I.S Wooley and Owen I97S Rest Not moving with bill tucked in feathers 1.4 Wooley and Owen I97S 48 THE WILSON BULLETIN • Vol. 1 17, No. I, March 2005 tion of time spent in that activity by the cor- responding multiple of BMR. The contribu- tion of physical activity to DEE (Table 2; EE^^^ti^jjy) was then calculated by summing the energetic costs of all activities in which Buf- fleheads engaged. DEE fixed-cost thermoregulation model. — Estimates of DEE were calculated using a method that incorporates a fixed cost of ther- moregulation (fixed-cost model; Morton et al. 1989). In this model, the thermoregulatory component (EE^hermoreg) is fixed and estimated at 5.9 kJ/hr (Morton et al. 1989). Additional energetic costs resulting from specific daily activities (EE^^-tj^ity) were calculated as in the SST model by multiplying the proportion of time spent in a particular activity by the en- ergetic cost of that activity. These two com- ponents were then summed to arrive at fixed- cost model estimates of DEE. DEE-habitat correlations. — We identified six Bufflehead wintering habitats within well- defined coves or embayments of the Narra- gansett Bay estuary. Included were two me- sotrophic, rocky- and sandy-bottom embay- ments (Sheffield Cove: 41° 29' 41" N, 71° 22' 89" W; and Mackeral Cove: 41° 29' 28" N, 71° 20' 86" W), two mesotrophic soft-bottom coves (Coggeshal Cove: 41° 39' 32" N, 71° 20' 52" W; and Brush Neck Cove: 41° 41' 47" N, 71° 24' 48" W), and two eutrophic soft-bot- tom coves (Apponaug Cove: 41° 41' 40" N, 71° 28' 58" W; and Watchemoket Cove 41° 48' 00" N, 71° 22' 75" W). Cove areas ranged from 18.6 to 86.1 ha, with an average of 42.2 ha. Each cove supported consistent numbers of Buffleheads throughout the winter (Novem- ber through April); the median flock size at the six sites (determined by bimonthly cen- suses during the winters of 2001-2002 and 2002-2003) was 18, ranging from 13 to 41. In winter, Buffleheads spend the majority of their time on the water and tend to favor shal- low water habitats (<3 m) in protected coves (Stott and Olson 1973, Gauthier 1993). They feed by diving to the cove bottom where they consume benthic invertebrates including crus- taceans, gastropods, and bivalves (Yocum and Keller 1961, Wiemeyer 1967, Gauthier 1993). We used focal animal sampling to quantify activities of Buffleheads at each of the study sites during the winters of 2001-2002 and 2002-2003 (Altmann 1974). We completed 965 observations on individual birds, resulting in over 80 hr of activity budget data. Obser- vations were randomly distributed over sam- ple sites and time during the daytime through- out the winter period when ducks were present (November-April). We chose individual ducks at random (i.e., observations began with the ith duck from the left in each flock, where i was a randomly generated number) and ob- served through a 32-60 X spotting scope or through 10 X 50 binoculars for 5 min; behav- iors were categorized as dive, surface, look (i.e., peering through the water at the cove bottom), courtship, agonistic, swim, fly, preen, alert, and rest (Table 1). Preening included wing flapping, stretching, and scratching. Gender for each individual was identified when possible, except in rare instances when we were unable to distinguish between fe- males and first-year males that had not yet de- veloped breeding plumage (Carney 1992). Therefore, we report results for “males” (showing breeding plumage) and “females” (includes first year males). Activity data were collected using an observational software pro- gram installed on a laptop computer (JWatch- er. Animal Behaviour Laboratory, Macquarie University, Australia; http://www.jwatcher. ucla.edu/). Prior to analysis, data were aggre- gated into the following categories: feeding (dive, surface, look), social (courtship, ago- nistic), locomotion (swim, fly), maintenance (preen, alert), and resting. Each sampling event at a site consisted of 20-30 five-min observations; final data were averaged by sampling event and by site. Sensitivity analysis. — We used linear re- gression analysis of SST model estimates of DEE versus wind speed and feeding behavior, respectively, to assess the relative contribution of each to DEE. First, we estimated DEE us- ing average values of feeding activity across all sites, and plotted DEE versus wind speed over the range of wind speeds recorded during the study (i.e., feeding activity held constant, wind speed varied; regression equation: DEE = [1.1 X wind speed] + 42.1). Second, we estimated DEE using average wind speed and temperature across the sites and plotted DEE versus the proportion of feeding activity (i.e., wind speed held constant, feeding activity var- ied; regression equation: DEE = [43.1 X pro- portion of time spent feeding] + 17.3). In each TABLE 2. Thermoregulatory costs (EEnK-rmoreg)- energetic costs resulting from specific daily activities (EEAc,,vity)» and daily energy expenditure (DEE) of Buffle- heads at six winter habitats in Narragansett Bay. Rhode Island, 200 1-2003. Values were calculated using thermoregulatory costs based on site-specific temperature and wind speed (site-specific thermoregulation model), and a previous method using fixed thermoregulatory costs (fixed-cost thermoregulation model; Morton et al. 10S9). Values are in kJ/hr ± SD. McKinney and McWilliams • WATERFOWL DEE MODEL 49 00 On CN 00 in in o cn ON r- q q in q q q q (N >n ON d no' ON d NO 00 (N 00 oi d d 00 d d 00 UJ PJ + 1 + 1 + 1 +1 +1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 +1 + 1 + 1 + 1 +1 + 1 +1 +1 1 1 1 Q ON in 00 o ON q (N q q q q q q q q q q 1 1 (d rd (N (N d T— < (N d d d d ri d d d d d d c 'It 'it 'it 'It 'it 'it 'It of of 3 00 00 O in in On o r-; (N q q q o q q q o q q q E d d d 00 d d 00 d d d d d 00 d d d d d d -C +1 +1 + 1 + i + 1 + 1 + 1 + 1 +1 + 1 +1 + 1 + 1 +1 + 1 + 1 + 1 +1 + 1 + 1 + 1 1 1 1 < 1 1 1 W (N o NO (N in On o q (N q q q NO q 00 q f- q ON d d NO NO NO NO NO 00 ON 00 00 NO d d d NO d NO d *s C) r<-) m CO C) cn m m m m m m m m fO m ro ro E H c B ON ON On On ON ON On ON q q q q q q q q q q q q q 1 1 1 vi IT) d d in d d d d d d d d d d d d d d d d 1 1 1 UP U 00 ON a. > u u a; > O /-N > d < > U ll I > u X o 7 X u cn 7? o \PFX V Apponaug Cove; BRI CV Brush Neck Cove; COGCV - Coggeshal Cove; MAKCV = Mackerel Cove; SHFCV = Sheffield Cove; WATCV = Watchemoket Cove. 50 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 case, we used average values of temperature and all other activities in the model. Regres- sion equations generated from each analysis were used to estimate the relative contribution of wind speed and feeding behavior to DEE. For wind speed, we calculated the average percent increase in DEE per 1 m/sec increase in wind speed. For proportion of time spent feeding, we calculated the average percent in- crease in DEE per 5% increase in the propor- tion of time spent feeding. Statistical analyses. — Differences in the proportion of time spent on different activities by males versus females were investigated us- ing two-tailed Student’s Utests on data aver- aged across all sample sites. Site-specific time budgets were calculated by averaging individ- ual observations by sampling event and then by averaging sampling events by site. Propor- tions were arcsine-square-root transformed prior to regression analysis (Fowler et al. 1998:87-88). Wind speed and temperature were averaged by sampling event and by site. Regression analysis and analysis of varianee were used to assess the influence of environ- mental eonditions on DEE and feeding behav- ior. Statistieal analyses were performed using SAS (SAS Institute, Inc. 2001). RESULTS Estimates of DEE for wintering Buffleheads generated using the SST model averaged 49.0 ± 8.4 kJ/hr, or 1,176 ± 202 kJ/day, and dif- fered by up to 12% among sites (Table 2). The mean thermoregulatory component of DEE (EExhermoreg; Table 2) was 11.7 ± 1.1 kJ/hr or 23.9% of total DEE; EEyhermoreg increased with increasing wind speed (r- = 0.61, P = 0.067). DEE did not differ between males and fe- males; however, thermoregulatory costs were higher for females (mean = 12.5 ± 1.2 versus 10.9 ± 1.0 kJ/hr for males; t^ = —7.2, P < 0.001). The mean DEE (all sites) calculated using the SST model was 13.4% higher than that calculated using the fixed-cost model (Table 2). The thermoregulatory component of DEE, 5.9 kJ/hr, composed 13.7% of total DEE cal- eulated with the fixed-cost model. Daily energy expenditures of Buffleheads ealculated with the SST model increased with increasing wind speed for males (P = 0.67, P = 0.046), females (U = 0.64, P = 0.055), and 0.0 1.0 2.0 3.0 4.0 5.0 Wind speed (m/sec) EIG. 2. Correlation of wind speed with (A) DEE and (B) time spent feeding for Buffleheads (males and females combined) wintering at six coastal habitats in Narragansett Bay, Rhode Island, 2001-2003. Wind speeds are means of all sampling sessions conducted at a site. Error bars are ± SE. males and females combined (P = 0.76, P = 0.023; Fig. 2A). The proportion of time spent feeding by Buffleheads also inereased with in- creasing wind speed (r- = 0.67, P = 0.047 Fig. 2B). Estimates of DEE that were gener- ated using the fixed-cost model showed no re- lationship between DEE and wind speed. Buffleheads spent 75.7 ± 4.3% of their time feeding during daylight hours, and females fed more often than males (77.1 ± 5.4% versus 74.2 ± 6.9%; ^545 = -2.6, P = 0.004; Table 3). Males, however, spent more of their time engaged in courtship activities (2.39% versus 0.43%; ^545 = 7.4, P < 0.001). Males and fe- males (combined) averaged 16.8% of their time engaged in loeomotion and maintenance, and 4.5% of the time resting (Table 3). Buf- fleheads at Mackerel Cove spent the greatest proportion of time feeding and the least in all other activities, whereas those at Coggeshal Cove spent the least time feeding and the most in all other activities, except resting. Overall, Buffleheads spent between 0.3 and 2.6% of McKinney and McWilliams • WATERFOWL DEE MODEL 51 •O *0 C CN X X q q q q a (N X d ON d 00 ON ON On in d d d X 00 X d 00 X d flj c X 00 00 in r- ON ON ON r- in, ■q- ’> X 00 r- O X q q q q in q ON m q q r<~, X q X in, q E CJ r3 -S in (N in x' X in d x’ d d d in in d in X X d d ri ■a C3 E + 1 +1 + 1 +1 +1 +1 + 1 + 1 +1 + 1 + 1 +1 + 1 + 1 tl + 1 +1 + 1 + 1 + 1 + 1 CJ Q r- ON _ 00 00 00 q q X X o ON X q 00 — X _ in. X E (N X X X d X d d q X X d X On d q in. V tJj 3 CQ d On ' ' in NO in X in X d o< 00 d C > in o 00 X X X X X On (N 00 O > u d > u o o d > o SI a: 0 q < X. u j'. III III I 1 I I I I I 1 I I I 1 I I I O X X X O ^ AI'K'V .\pp«>n;iiig C’nvc; BKl'CV Brush Neck Cove; COCiCV — C'oggeshal C'ove; MAKCV — Mackerel Cove; SHFCV = Sheffield Cove; WATCV — Watchemoket Cove. 52 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 their time in social activities, and this time decreased as the ducks increased feeding (r^ == 0.71, P = 0.043). Similarly, the amount of time spent in maintenance activities (range = 3. 7-9. 7%) decreased as time spent feeding in- creased (r^ = 0.96, P = 0.001). Sensitivity analysis of model estimates of DEE versus wind speed at constant proportion of time spent feeding showed that a 1 m/sec increase in wind speed resulted in a 2.5% in- crease in DEE. Analysis of DEE versus the proportion of time spent feeding at constant wind speed showed that a 0.05 increase in proportion of time spent feeding resulted in a 4.5% increase in DEE. DISCUSSION Our estimates of DEE using the SST model for Buffleheads at the Narragansett Bay win- tering sites (1,175 ± 202 kJ/day) are higher than those predicted from the fixed-cost model (1,036 ± 202 kJ/day), which uses a single en- ergetic cost of thermoregulation. Thermoreg- ulatory costs predicted by the SST model con- stitute up to 28% of the animal’s total DEE and are approximately twice as high on av- erage as that used in the fixed-cost model. DEE estimates for Buffleheads at our sites were also higher than a field metabolic rate predicted by an allometric relation of energy expenditure based on empirical studies (606 kJ/day, non-passerines; Nagy et al. 1999). However, many of the studies from which this relation was derived were carried out in the breeding season in warm ambient tempera- tures, so our higher DEE estimates may be attributed in part to environmental conditions and the inclusion of thermoregulatory energy costs. Our model does not include the contribu- tion of heat gained from solar radiation or heat lost through evaporative water loss because these effects are likely relatively small (less than 10% of heat loss; Scholander et al. 1950, Strunk 1971, Wolf and Walsberg 2000), and were likely similar between our study sites. Nonetheless, these constraints limit the appli- cation of our model to comparative, single- species studies between habitats that are lo- cated in a similar geographic region. It is also important to note that the SST model is lim- ited by the availability of empirically derived energetic equivalents of specific waterfowl be- haviors, as is the fixed-cost model. We applied the model to Buffleheads, but were restricted to using literature-based energetic equivalents that were not specific to that species. There- fore, the DEE estimates presented here, while higher than those calculated from the fixed- cost model and from body mass alone, fall well within the probable error of 20-40% pro- posed by Weathers et al. (1984) for models that rely on generic energetic equivalents. However, while it would be difficult to argue that our model estimates are more accurate than those calculated from fixed-cost or body mass models, the utility of our model lies in the ability to determine the relative contribu- tion of wind speed, temperature, and specific waterfowl behaviors to DEE across sites with different environmental conditions and levels of activity. Wintering waterfowl may incur substantial thermoregulatory costs depending on ambient temperatures and the combined effect of wind and cold, and these may lead to increases in DEE. Changes in the relative amounts of ac- tivities exhibited by wintering Buffleheads may also alter DEE. In our study, estimates of DEE calculated with the SST model were cor- related with wind speed (Fig. 2A). However, feeding activity also increased with increasing wind speed (Fig. 2B), which could also con- tribute to an increase in DEE. Sensitivity anal- ysis of the effects of increases in wind speed and feeding activity on DEE showed that in- creases in feeding activity resulted in a rela- tive increase in waterfowl DEE nearly twice that of a corresponding increase in wind speed. Feeding activity may increase because of decreased prey abundance, or because of changes in the availability or energetic content of prey. Further studies at our sites have shown that feeding activity increased with de- creasing prey abundance, and also with de- creasing prey energy density resulting from changes in available prey species at a site and inter-specific differences in the energetic con- tent of prey (RAM and SRM unpubl. data). However, other factors, such as intra- and in- ter-specific competition and increased ener- getic demands, may also influence the amount of feeding activity. Although we are uncertain as to the cause of increases in time spent feed- ing at our sites, our results show that increased McKinney and McWilliams • WATERFOWL DEE MODEL 53 feeding activity may have a greater impact than wind exposure on DEE of Buffleheads. Increased feeding activity may also affect the short- and long-term survival of Buffle- heads. For example, if wintering Buffleheads need to spend more time feeding, time for oth- er activities such as courtship and pair for- mation may be limited (Drent and Daan 1980, Meijer and Drent 1999). Although they exhib- it long-term pair bond formation and a high degree of flock synchrony, which results in a relatively small proportion of time spent in so- cial behaviors, courtship and maintenance ac- tivities are still important for their overall re- productive success (Robertson et al. 1998). Our results indicate that as Buffleheads at our sites spent more time feeding, they had less time available for maintenance and social be- haviors, which may have an impact on both their short- and long-term survival. This, cou- pled with the greater increases in energetic costs due to feeding activity predicted from model sensitivity analysis, suggests that DEE of wintering waterfowl in harsh climates would be lower in habitats with both high prey density and adequate protection from ex- posure. For example, sites such as Brush Neck Cove, which had the highest prey abundance (RAM and SRM unpubl. data) and also the lowest thermoregulatory costs for Buffleheads (Table 2), may be better candidate sites for protection as waterfowl wintering habitats compared with sites such as Mackerel Cove, which had low prey abundance and high ther- moregulatory costs. In summary, our SST model estimated DEE as the sum of basal metabolic rate and site- specific energetic costs of activity and ther- moregulation. The primary benefits of the SST model compared to other approaches in- clude its ability to (1) evaluate the effect of thermoregulatory costs on DEE of wintering waterfowl using simple measurements of wind speed and ambient temperature, (2) predict the extent to which the behavior of waterfowl dur- ing winter affects DEE, and (3) track changes in DEE over different time scales (i.e., hourly, daily, or seasonally) if the corresponding ac- tivity and environmental data are available. Also, because of its ability to estimate site- specilic DEE^ based on local conditions, the model may be useful in evaluating the quality of waterfowl habitats that have different attri- butes such as prey abundance, or degree of protection from high winds and extreme tem- peratures. However, further studies will be needed to establish the independence of be- havioral responses to environmental condi- tions from the primary effect of the conditions themselves on the DEE of resident waterfowl before model estimates can be used in habitat assessment. ACKNOWLEDGMENTS We would like to thank K. Bannick and B. Timm for assistance collecting field data. Access to Buffle- head study skins at the Harvard Museum of Compar- ative Zoology was obtained with the kind assistance of J. Trimble and A. Pirie. We also thank K. Appier and the Connecticut Waterfowl Trust for access to live birds, and D. T. Blumstein, C. S. Evans, and J. C. Daniel for assistance with behavioral data analysis. S. Walters, S. A. Ryba, C. Wigand, and T. R. Gleason provided insightful comments on the manuscript. We also thank M. R. Miller and two anonymous referees for thoughtful comments on an earlier version of this paper. Mention of trade names or commercial products in this report does not constitute endorsement or rec- ommendation. Although the research described in this article has been funded wholly by the U.S. Environ- mental Protection Agency, it has not been subjected to Agency-level review. Therefore, it does not necessarily reflect the views of the Agency. This paper is the Of- fice of Research and Development, National Health and Environmental Effects Research Laboratory, At- lantic Ecology Division contribution number AED-04- 074. LITERATURE CITED Albright, J. J., R. B. Owen, Jr., and P. O. Corr. 1983. The effects of winter weather on the behavior and energy reserves of Black Ducks in Maine. Trans- actions of the Northea.st Section of the Wildlife Society 40:1 18-128. Altmann, j. 1974. Observational study of behavior: sampling methods. Behaviour 49:227-26.‘i. Barken, G. S. 1992. Measurement and application of operative and standard operative temperature in ecology. American Zoologist 32:194-216. Baldassarre, G. A.. S. L. Pallus, A. Ta.smisii;r, and R. D. Titman. 1988. WorkslK>p summary: tech- niques for timing activity of wintering waterfowl. Pages 181-188 in Waterfowl in winter: selected papers from symposium anti workshop held in Galveston. Texas, 7-IO.Ianuary I98.S (M. W. Wel- ler, lid.). University ol Minnesota Press. Minne- apolis. Bi i ROM . p; 1980. Ducks, geese, and swans of North America, 3rd ed. .Stackpole Books. Harrisburg. Pennsylvania. Benni ri. .1. W. and li. G. Bolen. 1978. .Stress response in wintering Green-w ingetl Teal. Journal of Wikl- life Management 42:81 86. 54 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 Birkebak, R. C. 1966. Heat transfer in biological sys- tems. International Reviews of General and Ex- perimental Zoology 2:269-344. BROD.SKY, L. M. AND R J. Weatherhead. 1985a. Div- ing by wintering Black Ducks: an assessment of atypical foraging. Wildfowl 36:72-76. Brodsky, L. M. and P. J. Weatherhead. 1985b. Var- iability in behavioural response of wintering Black Ducks to increased energy demands. Ca- nadian Journal of Zoology 63:1657-1662. Buteer, P. j. 2000. Energetic costs of surface swim- ming and diving of birds. Physiological and Bio- chemical Zoology 73:699-705. Calder, W. a. and j. R. King. 1974. Thermal and caloric relations of birds. Avian Biology 4:259- 413. Carney, S. M. 1992. Species, age, and sex identifi- cation of ducks using wing plumage. U.S. Fish and Wildlife Service, Washington, D.C. DE Leeuw, j. j. 1996. Diving costs as a component of daily energy budgets of aquatic birds and mam- mals: generalizing the inclusion of dive-recovery costs demonstrated in Tufted Ducks. Canadian Journal of Zoology 74:2131-2142. Drent, R. H. and S. Daan. 1980. The prudent parent: energetic adjustments in avian breeding. Ardea 68:225-252. Ettinger, a. O. and j. R. King. 1980. Time and en- ergy budgets of the Willow Flycatcher (Empidon- ax traillii) during the breeding season. Auk 97: 533-546. Fowler, J., L. Cohen, and P. Jarvis. 1998. Practical statistics for field biology. John Wiley & Sons, New York. Fredrickson, L. H. and R. D. Drobney. 1979. Habitat utilization by postbreeding waterfowl. Pages 239- 272 in Waterfowl and wetlands: an integrated re- view (T. A. Bookhout, Ed.). LaCrosse Printing, LaCrosse, Wisconsin. Gauthier, G. 1993. Bufflehead (Bucephala albeola). The Birds of North America, no. 67. Goldstein, D. L. 1983. Effect of wind on avian met- abolic rate with particular reference to Gambel’s Quail. Physiological Zoology 56:485-492. Hickey, T. E. and R. D. Titman. 1983. Diurnal activity budgets of Black Ducks during their annual cycle on Prince Edward Island. Canadian Journal of Zo- ology 61:743-749. Jenssen, B. M., M. Ekker, and C. Bech. 1989. Ther- moregulation in winter-acclimatized Common Ei- ders {Somateria mollissima) in air and water. Ca- nadian Journal of Zoology 67:669-673. JoRDE, D. G., G. L. Krapu, R. D. Craweord, and M. A. Day. 1984. Effects of weather on habitat se- lection and behavior of Mallards wintering in Ne- braska. Condor 86:258-265. Kendeigh, S. C. 1949. Effect of temperature and sea- son on energy resources of the English Sparrow. Auk 66:113-127. Kendeigh, S. C., V. R. Dol’nik, and V. M. Gavrilov. 1977. Avian energetics. Pages 127-204 in Graniv- orous birds in ecosystems: their evolution, popu- lations, energetics, adaptations, impact, and con- trol (J. Pinowski and S. C. Kendeigh, Eds.). Cam- bridge University Press, New York. Koplin, j. R., M. W. Collopy, A. R. Bammann, and H. Levenson. 1980. Energetics of two wintering raptors. Auk 97:795-806. McNab, B. K. 2003. The energetics of New Zealand’s ducks. Comparative Biochemistry and Physiology A 135:229-247. Meher, T. and R. H. Drent. 1999. Re-examination of the capital and income dichotomy in breeding birds. Ibis 141:399-414. Miller, M. R. 1985. Time budgets of Northern Pintails wintering in the Sacramento Valley, California. Wildfowl 36:53-64. Morton, J. M., A. C. Fowler, and R. L. Kirkpatrick. 1989. Time and energy budgets of American Black Ducks in winter. Journal of Wildlife Man- agement 53:401-410. Nagy, K. A., I. A. Girard, and T. K. Brown. 1999. Energetics of free-ranging mammals, reptiles, and birds. Annual Reviews of Nutrition 19:247-277. Nilsson, L. 1970. Food-seeking activity of south Swedish diving ducks in the non-breeding season. Oikos 21:145-154. Parker, H. and H. Holm. 1990. Patterns of nutrient and energy expenditure in female Common Eiders nesting in the high arctic. Auk 107:660-668. Paulus, S. L. 1984. Activity budgets of nonbreeding Gadwalls in Louisiana. Journal of Wildlife Man- agement 48:371-380. Paulus, S. L. 1988. Time-activity budgets of non- breeding Anatidae: a review. Pages 135-152 in Waterfowl in winter: selected papers from sym- posium and workshop held in Galveston, Texas, 7-10 January 1985 (M. W. Weller, Ed.). Univer- sity of Minnesota Press, Minneapolis. Pearson, O. P. 1954. The daily energy requirements of a wild Anna Hummingbird. Condor 56:317- 322. Porter, W. P. and D. M. Gates. 1969. Thermodynam- ic equilibria of animals with environment. Eco- logical Monographs 39:227-244. Quinlan, E. E. and G. A. Baldassarre. 1984. Activ- ity budgets of non-breeding Green-winged Teal on playa lakes in Texas. Journal of Wildlife Manage- ment 48:838-845. Rave, D. P. and G. A. Baldassarre. 1989. Activity budgets of Green-winged Teal wintering in coastal wetlands of Louisiana. Journal of Wildlife Man- agement 53:753-759. Robertson, G. J., E Cooke, R. I. Goudie, and W. S. Boyd. 1998. The timing of pair formation in Har- lequin Ducks. Condor 100:551-555. SAS Institute, Inc. 2001. SAS for Windows, ver. 6.12. SAS Institute, Inc., Cary, North Carolina. ScHARTZ, R. L. AND J. L. ZiMMERMAN. 1971. The time and energy budget of the male Dickcissel (Spiza americana). Condor 73:65-76. Schmidt-Nielsen, K. 1997. Animal physiology: ad- aptation and environment, 5th ed. Cambridge Uni- versity Press, Cambridge, United Kingdom. SCHOLANDER, P. E, R. HOCK, V. WALTERS, E JOHNSTON, AND L. Irving. 1950. Heat regulation in some arc- McKinney and McWilliams • WATERFOWL DEE MODEL 55 tic and tropical mammals and birds. Biological Bulletin 99:225-236. SiPLE, R A. AND C. F. Passed. 1945. Measurements of dry atmospheric cooling in subfreezing tempera- tures. Proceedings of the American Philosophical Society 89:177-199. Stiles, F. G. 1971. Time, energy, and territoriality of the Anna Hummingbird (Calypte anna). Science 173:818-821. Stott, R. S. and D. P. Olson. 1973. Food-habitat re- lationship of sea ducks on the New Hampshire coastline. Ecology 54:996-1007. Strunk, T. H. 1971. Heat loss from a Newtonian an- imal. Journal of Theoretical Biology 33:35-61. Turnbull, R. E. and G. A. Baldassarre. 1987. Ac- tivity budgets of Mallards and American Wigeon wintering in east-central Alabama. Wilson Bulle- tin 99:457-464. Walsberg, G. E. 1977. Ecology and energetics of con- trasting social systems in Phainopepla nitens (Aves: Ptilogonatidae). University of California Publications in Zoology, no. 108, Berkeley. Walsberg, G. E. 1983. Avian ecological energetics. Avian Biology 7:138-172. Weathers, W. W., W. A. Buttemer, A. M. Hayworth, AND K. A. Nagy. 1984. An evaluation of time- budget estimates of daily energy expenditure in birds. Auk 101:459-472. WiEMEYER, S. N. 1967. Bufflehead food habits, para- sites, and biology in northern California. M.Sc. thesis, Humboldt State College, Areata, Califor- nia. Wole, B. O. and G. E. Walsberg. 2000. The role of plumage in heat transfer processes of birds. Amer- ican Zoologist 40:575-584. Woolly, J. B., Jr. and R. B. Owen, Jr. 1978. Energy costs of activity and daily energy expenditure in the Black Duck. Journal of Wildlife Management 42:739-745. Yocum, C. F. and M. Keller. 1961. Correlation of food habits and abundance of waterfowl, Hum- boldt Bay, California. California Fish and Game 47:41-54. APPENDIX. Variables used to calculate heat transfer, an adjusted metabolic rate at ambient temperature, using a heat transfer model proposed by Birkebak (1966). Representative values are from repeated measurements on live and preserved Buffleheads from northeastern estuaries. Equations are taken from Birkebak (1966); k is the heat transfer coefficient, AT is the difference between body temperature (39° C) and ambient temperature. Variable Symbol Equation Representative value (cm ± SD) Head length A — 5.9 ± 0.4 Head height B — 5.0 ± 0.8 Head width C — 3.2 ± 0.4 Body width D — 9.1 ± 0.9 Body length F — 18.2 ± l.l Body height G — 6.3 ± 0.6 Neck length H — 2.0 ± 0.3 Neck width I — 2.9 ± 0.4 Neck height J — 2.9 ± 0.4 Integument depth-body ‘^^hody — 0.4 ± 0.1 Integument depth-head ‘^^hcad — 0.7 ± 0.2 Integument depth-neck — 0.7 ± 0.2 Inner radius of body ^1 b + d)/2 10.5 ± 0.5 l.ength of neck ^ 'neck = //-(/ + ./)/2 0.9 0.1 Outer radius of body h« b II X to 96.0 1 21.6 Heat loss from head Qhead tt,w = (2n X X r„„„, X k X A/-)/ — Heat loss from neck Qne.k 1 flu tiil ^ difiiil 1 = (2tt X X k X A /V|ln( Hi Heat loss from breast Qhie.m X X X k X A/V — Heat loss from body Qh.H.y ^ fdxxld Cwv (2tt X X k X A/Vlln(/„,.,.,y/„,,0| Heat loss from ventral Qv. X X — surface Heat loss Irom tail G..n, G/wi/ Qhrr,nl — Wilson Bulletin 1 1 7( 1 ):56-62, 2005 APPARENT PREDATION BY CATTLE AT GRASSLAND BIRD NESTS JAMIE L. NACKi 3 AND CHRISTINE A. RIBIC^ ABSTRACT. — We document the first cases of cattle behaving as avian predators, removing nestlings and eggs from three active ground nests in continuously grazed pastures in southwestern Wisconsin, 2000-2001. Cows removed three of four Savannah Sparrow {Passerculus sandwichensis) eggs from one nest (the fourth egg was damaged), all four Eastern Meadowlark (Sturnella magna) nestlings from another, and all three Savannah Sparrow nestlings from a third. We found only two of three missing eggs (intact) and one of seven missing nestlings (dead) near two of the nests. Cows may have eaten the egg and nestlings we were unable to account for; alternatively, the egg and nestlings may have been scavenged by predators or removed from the area by the adult birds. Without videotape documentation, we would have attributed nest failure to traditional predators and cattle would not have been implicated. We may be underestimating the impact of cattle on ground nests by not considering cattle as potential predators. Received 10 May 2004, accepted 6 December 2004. Over the last 30 years, grassland birds have declined more rapidly and consistently than any other avian guild in the Midwest (Vickery and Herkert 2001). One possible cause is the loss and fragmentation of native and second- ary grasslands (Sample et al. 2003). Herkert et al. (1996) found a significant correlation be- tween the decline of grassland birds in the Midwest and the conversion of hay and pas- ture acreage to row crops and other unsuitable habitat. Since the conversion of land from na- tive prairie to agriculture during European set- tlement, secondary grasslands, such as pas- tureland, have become critical components of grassland passerine conservation (Herkert 1991, Herkert et al. 1996, Sample and Moss- man 1997). Nest predation is a major factor in the nest- ing failure of most passerine species (Lack 1968, Ricklefs 1969, Martin 1988). This may be a particular problem in grassland ecosys- tems where generalist predators, such as rac- coons {Procyon lotor) and skunks {Mephitis spp.), have responded positively to human dis- turbance and landscape fragmentation (Sar- geant et al. 1993, Warner 1994). In actively grazed pastures, ground-nesting grassland birds face additional risks from cattle. In southwestern Wisconsin, Temple et al. (1999) thought that many of the nest losses incurred ' Dept, of Wildlife Ecology, Univ. of Wisconsin- Madison, Madison, WI 53706, USA. ^ uses Wisconsin Coop. Wildlife Research Unit, Dept, of Wildlife Ecology, Univ. of Wisconsin-Madi- son, Madison, WI 53706, USA. ^ Corresponding author; e-mail; jlnack@wisc.edu by grassland birds in grazed pastures were a result of cattle trampling and nest desertion after cattle had grazed down the vegetation surrounding the nest. In previous literature on cattle disturbance to bird nests, authors have used sign to inter- pret the occurrence of cattle disturbance, mainly at artificial nests and under rotational grazing regimes (Paine et al. 1996, 1997). Un- der a rotational grazing regime at the Univer- sity of Wisconsin’s Lancaster Agricultural Re- search Station in southwestern Wisconsin, Paine et al. (1996) documented cattle distur- bance resulting in nest failure at simulated ground nests in which Ring-necked Pheasant (Phasianus colchicus) eggs had been placed. Ninety-four percent of failed nests were the result of cattle damage. Nest disturbance in- cluded nest contents being trampled, kicked out, crushed by the animal’s muzzle, or cov- ered with a manure pile. The mean percentage of nests {n = 15) having >1 egg trampled by a bovine hoof was 63% for the 1-day treat- ment, 52% for the 4-day treatment, and 41% for the 7-day treatment. In a refinement of their 1996 study, Paine et al. (1997) documented cattle sniffing, lick- ing, and occasionally picking up contents of simulated ground nests (clay pigeon targets and pheasant eggs). Their study was not de- signed to represent natural conditions, but rather to assess intentional and inadvertent nest disturbances. Overall trampling levels for clay pigeon targets and pheasant eggs were 35 and 36%, respectively. Cattle intentionally disturbed 25% of clay targets and 8% of egg 56 Nack and Ribic • CATTLE AND GRASSLAND BIRDS 57 nests. In a few instances, cattle picked up sin- gle eggs with their mouths and carried them “several feet” without damaging them. Whereas several studies have evaluated cat- tle trampling and/or disturbance at artificial ground nests in rotationally grazed pastures (Koerth et al. 1983; Jensen et al. 1990; Paine et al. 1996, 1997), few studies have docu- mented cattle disturbances to nests in contin- uously grazed systems under conditions oc- curring in the Midwest. Cattle have not previously been document- ed deliberately removing eggs and young from active passerine nests. Other herbivores that have been documented eating or remov- ing eggs and/or young include white-tailed deer {Odocoileus virginianus\ Pietz and Gran- fors 2000) and caribou {Rangifer tarandus; Abraham et al. 1977) in North America, and sheep (Ovis) and red deer {Cerx’us elaphus) in the British Isles (Furness 1988a, 1988b; Pen- nington 1992). Our study is unique in provid- ing direct documentation of cattle effects on real nests of grassland passerines under a con- tinuous grazing regime. METHODS We searched for ground-nesting grassland bird nests in continuously grazed pastures in 2000 {n — 10) and 2001 {n = 9) in south- western Wisconsin (Nack 2002). Stocking rates in pastures (May-August) ranged from 0.61 to 4.28 animal units (AU)/ha (mean = 2.09, SE = 0.37, n = 10) and from 0.75 to 4.33 AU/ha (mean = 2.19, SE = 0.34, n = 9) in 2000 and 2001, respectively. To capture video footage of nest predators, we used methods and camera equipment sim- ilar to those used by Renfrew and Ribic (2003). Sentinel"^ all-weather miniature video camera surveillance systems (Sandpiper Tech- nologies, Manteca, California) were deployed at nests between 15 May and 31 July 2000- 2001. In a pilot study during 2000, cameras were placed in a single pasture at 13 of 198 nests. In 2001, cameras were set up in six pas- tures (including the pasture used in 2000) at 41 of 196 nests. In total, we monitored 54 ground nests with cameras: 34 Savannah Sparrow {l^isscrcuhts sandwichensis), 12 meadowlark {StunicHa magna and S. ncglec- ta)-, 4 Bobolink {DoUchonyx otyz.ivorns), 3 Grasshopper Sparrow (Ammodramus savnn- narum), and 1 Upland Sandpiper (Bartramia longicauda). Cameras were mounted 5-30 cm above ground on a wooden dowel and placed ap- proximately 12-25 cm from nests. Cameras were concealed in surrounding vegetation in an attempt to avoid detection by predators. Because vegetation height in the pastures was relatively short and birds preferred to nest in small clumps of grass, we were forced to place cameras closer to nests than we would have liked. Each camera’s field of view in- cluded the nest and a small area surrounding the nest. Each camera was 4X4X4 cm (64 cm^) in size and had infrared light-emitting diodes (LEDs) mounted around the lens to provide illumination at night. The camera was con- nected by a 25-m cable to a 24-hr, time-lapse videocassette recorder (VCR) and a deep-cy- cle marine battery. The cable was buried just underneath the sod layer to protect it from cat- tle and rodents. The VCR was enclosed in a waterproof case, and the battery and case were eovered with a pyramid made from metal hog- fencing panels. The pyramid was then staked into the ground to prevent cattle disturbance and covered with a piece of green canvas to shade the VCR and prevent it from overheat- ing. Nests were checked remotely each day by using a monitor at the VCR to view the nest without having to disturb the nesting birds. The battery powering the VCR was changed every other day and the tape was changed dai- ly. The VCR recorded 4 frames/sec; thus, a standard VHS tape would last for a 24-hr pe- riod. Videotapes were reviewed to determine nest fates and identify predators. We consid- ered a nest successful if one nestling Hedged. We used head size, shape, and position to identify images as cattle. We refer to the cattle as cows (pastures were stocked with cows, cow/calf pairs, and one bull). We categorized nest failure attributed to cattle as either apparent nest predatioti or in- advertent disturbances (e.g., trampling, knock- ing the camera into the nest bowl and subse- cjucntly breaking eggs). We definetl apparent nest predation as the delibcFate removal of nest contents by cattle, but with the ultimate fate (i.e., consumption) unknown. 58 THE WILSON BULLETIN • Vol. 1 17, No. I, March 2005 LIG. 1. Sequence of images documenting a cow removing three Savannah Sparrow eggs from an open-cup nest and crushing the fourth egg in a southwestern Wisconsin pasture, 1 1 June 2001. RESULTS Of the 54 nests monitored by cameras, 7 were abandoned after the camera was de- ployed, 12 were successful, 21 were depre- dated by “traditional” predators, and 14 failed due to cattle disturbance. Seven of the 14 (50%) cattle-caused nest failures were inad- vertent disturbances; a cow lay down on one nest, one was abandoned, two were trampled, and the camera was knocked down at three nests, crushing the eggs. Apparent nest pre- dation occurred at 3 of the 14 (21%) nests. At four others, we were unable to categorize the nest failure attributed to cattle. In three of these four cases, the camera was either knocked over or tipped by a cow, but there was no clear footage of events; some of the nest contents were missing but we could not be certain they were removed by the cow (they may have been removed by one of the adult birds). In the fourth case, grass was pushed up against the camera and it was un- clear whether a cow killed the nestlings with its muzzle or trampled them. After the cow left, camera footage revealed that an adult bird returned and removed all five dead nestlings. The following summarizes the three in- stances of apparent nest predation by cattle. Event l.—On 11 June 2001 at 18:53:27 CST, an adult Savannah Sparrow flushed from its open-cup nest containing four eggs (Fig. lA, 18:53:38). The grass surrounding the nest began to move 9 sec later. At 18:54:02, a cow’s muzzle was visible at the nest bowl, where it remained for 13 sec (Fig. IB, 18:54: 05). At 18:54:15, the cow moved its muzzle out of the nest and the videotape showed two intact eggs and one broken egg in the nest (Fig. 1C). At 18:54:21, the cow’s muzzle was again visible at the nest bowl and remained there for 37 sec (Fig. ID, 18:54:27), during which time the cow continued to remove eggs. At 18:54:35, there was a clear view of one intact egg and one broken egg (Fig. IE). At 18:54:49, only a piece of the broken egg was in the nest bowl (Fig. IF). The cow’s muzzle Nack and Ribic • CATTLE AND GRASSLAND BIRDS 59 moved out of view at 18:54:58, but the cow continued to stay near the nest and returned to the empty nest bowl a few times, apparently licking the grass. At 18:56:46, the cow tipped I the camera over and nuzzled it until 18:57:45, ^ when the cow presumably left. In summary, the cow was at the nest bowl for at least 50 ' sec during two visits. After examining the nest bowl and surrounding area, we found two in- i tact eggs approximately 20 cm from the nest and a piece of eggshell in the nest bowl. The nest bowl was slightly pulled apart. Event 2.— On 23 May 2001 at 06:45:07, an adult Eastern Meadowlark left its domed nest after feeding four 5-day-old nestlings. At 07: 00:27, grass movement was visible on the vid- I eotape and it was apparent that the camera I was being nudged. At 07:03:25, a cow put its I muzzle in the nest bowl, where it remained i for 8 sec before moving out of camera view. ! At 07:03:33, only three nestlings remained. ! During the next 6 min, the cow stayed in the area of the nest, as evidenced by grass and camera movement. At 07:09:29, the cow re- ! turned and placed its muzzle in the nest bowl I for 4 sec. At 07:09:33, there were only two nestlings in the nest (cow not visible in the frame). At 07:1 1:13, an adult meadowlark re- turned to the nest with a caterpillar, fed the j remaining two nestlings, and sat on the nest, j The nest was tended for the next 1 1 hr (07:09 I to 18:07). We inspected the nest area at 14:00 I and found no sign of the two missing nest- I lings; there were still two live nestlings in the ; nest. An adult fed the nestlings at 18:07:46 and I left at 18:12:16 with a fecal sac. The grass 1 began to move at 18:18:17 and the camera { was jostled. At 18:18:28, a cow placed its ! muzzle in the nest bowl, where it remained for 3 sec. The camera was then moved so that I the nest was out of view, but the cow's dark muzzle could be detected occasionally through the vegetation until 18:18:53. In sum- mary, a cow was at the nest for at least 15 sec ! during three visits. We inspected the nest area I again on 24 May at 13:30, and found no young in the nest; however, 30 cm from the nest was a dead nestling that had no visible i signs of injury, fhe edges of the nest bowl were llattened and the camera was turned j slightly. In our study area, Ihisiern Meadow- larks typically fledge at 10 days, so it is un- likely that the missing nestlings survived. Event 3.— On 7 July 2001 at 05:11:37, an adult Savannah Sparrow fed three 7-day-old nestlings in its open-cup nest. At 05: 1 1 :44, the adult left carrying a fecal sac. At 05:15:46, grass movement was detected on the video. At 05:16:03, a cow’s muzzle was visible at the nest (Fig. 2A), where it remained for 5 sec, but the cow did not remove any of the nest- lings (Fig. 2B, 05:16:21). At 05:16:45, a cow’s muzzle passed over the nestlings again for 3 sec without removing anything. At 05: 16:53, a cow’s muzzle was visible at the nest for a third time for 13 sec, during which time the cow pulled its muzzle out of the nest bowl with at least one nestling in its mouth (pre- sumably two nestlings; Fig. 2C, 05:17:01). The cow then dropped one nestling back into the nest bowl (Fig. 2D, 05:17:02) and moved out of camera view. Two nestlings remained in the nest bowl (Fig. 2E, 05:17:26). At 05: 17:30, a cow’s muzzle was again visible at the nest bowl and remained there for 5 sec, during which time it removed both of the remaining nestlings (Fig. 2F, G). At 05:17:35, the nest bowl was empty (Fig. 2H). In summary, the cow was at the nest for at least 26 sec during four visits. We examined the nest and sur- rounding area on 7 July at 12:50, and found no sign of the three nestlings; the nest bowl was flattened on one side and the grass sur- rounding the nesi was trampled. The nestlings showed no attempt to fledge during filming and we think it is unlikely that they survived. DISCUSSION This study was designed to document the predators of ground-nesting grassland bird nests in continuously grazed pastures in south- western Wisconsin. The use of cameras al- lowed us to document — for the first lime — apparent nest predation by cattle. Cattle re- moved eggs and nestlings, then either con- sumed nest contents that were unaccounted for or simply carried them off. Alternati\ ely, missing nest contents may ha\ e been sca\ - enged by other animals or removctl from the nest area by the adult birds after the cattle left. All of our jiastures were on private land where stocking rates were at the tliscretion ol the landowner. In the Midwest, a light, con- tinuous grazing regime would be about I 60 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 A EIG. 2. Sequence of images documenting a cow removing three 7-day-old Savannah Sparrow nestlings from an open-cup nest in a southwestern Wisconsin pasture, 7 July 2001. AU/ha, and a moderate, continuous grazing regime would be about 2 AU/ha under aver- age environmental conditions (D. J. Undersan- der pers. comm.). Stocking rates in the pas- tures we studied appeared to be moderate. Al- though camera equipment in the pastures may have contributed to cattle disturbance of nests, we do not believe that stocking rates per se influenced cattle disturbance to the cameras or the nests. Instead, cattle-caused nest failure appeared to be associated more with the be- havior of individual herds rather than stocking rates (Nack 2002). Our observations suggest that curiosity and behavior of cattle toward the camera and VCR system varied among herds. The range of behavior we observed was sim- ilar to that described by Renfrew and Ribic (2003) in southwestern Wisconsin. In some pastures, cattle were uninterested in camera equipment; they only investigated it initially Nack and Ribic • CATTLE AND GRASSLAND BIRDS 61 and then ignored it. In a few pastures, cattle frequently knocked over the cameras, but did not necessarily cause nests to fail. Whether or not cattle found nests as a result of their attraction to the cameras, we docu- mented that once a cow discovers a nest, it does not necessarily ignore it. Similar events likely occur when cattle incidentally discover nests while grazing, much like any other pred- ator that forages opportunistically. Based on the evidence (or lack thereof), we would have assigned nest fate correctly as predation, but would not have considered cattle as possible predators. Videotaped evidence of cattle re- moving nestlings and eggs from ground nests suggests that the impact of cattle on grassland bird nests has been underestimated in the past. Future studies should be conducted to quan- tify the extent to which cattle disturb nests while minimizing their attraction to camera equipment. To reduce curiosity and habituate cattle to camera equipment, Renfrew and Ri- bic (2003) suggest deploying “fake” camera systems 2 to 3 weeks prior to use. Conducting research on ground-nesting grassland birds in actively grazed pastures is challenging. Future advances in camera tech- nology may benefit researchers. For example, cameras that can be placed in close proximity to nests while providing a wider field of view I would help with identifying larger predators and determining the fate of each egg and/or nestling. Wireless camera systems (e.g.. King et al. 2001) designed to operate from outside of the pasture fencing would eliminate the need to have the VCR, battery, and protective pyramid, which seem to attract the cattle. This would also reduce set-up time, as there would : be no need to bury video cable. ACKNOWLEDGMENTS We thank 1’. J. fhet/., D. W. Sample, L. l^aine, M. J. Gu/.y, and S. M. Vos for providing helpful comments on an earlier version of this manuscript. We also thank M. J. Gu/y for reviewing videotaj^cs and helping to capture figure images. P. J. Piet/ and two anonymous referees provided thoughtful reviews of this manu- script. Punding for this project was proviticd by the Department of Wildlife Pxology at the University of Wisconsin-Madison, IJSGS Wisconsin C\)0|icrative Wildlife Research Unit. Wisconsin Department of Nat- ural Resources, USIAV’S Partnerships for Wildlife, and the USDA C'ooperalive State Research, lulucation, and PAtension Service. We thank the Max Mefiraw WiUl- life Foundation for assistance with publication expens- es. Mention of a company or trade name does not con- stitute endorsement of a product. LITERATURE CITED Abraham, K. F, P. Mineau, and F. Cooke. 1977. Un- usual predators of Snow Goose eggs. Canadian Field-Naturalist 91:317-318. Furness, R. W. 1988a. Predation on ground-nesting seabirds by island populations of red deer Cervus elaphus and sheep Ovis. Journal of Zoology 216: 565-573. Furness, R. W. 1988b. The predation of tern chicks by sheep. Bird Study 35:199-202. Herkert, j. R. 1991. Prairie birds of Illinois: popula- tion response to two centuries of habitat change. Illinois Natural History Survey Bulletin 34:393- 399. Herkert, J. R., D. W. Sample, and R. E. Warner. 1996. Management of Midwestern grassland land- scapes for the conservation of migratory birds. Pages 89-116 in Managing Midwestern land- scapes for the conservation of Neotropical migra- tory birds (F. R. Thompson, III, Ed.). General Technical Report GTR-NC-187, USDA Forest Service, North Central Forest Experiment Station, St. Paul, Minnesota. Jensen, H. P, D. Rollins, and R. L. Gillen. 1990. Effects of cattle stock density on trampling loss of simulated ground nests. Wildlife Society Bul- letin 18:71-74. King, D. I., R. M. DeGraaf, P. J. Champlin, and T. B. Champlin. 2001. A new method for wirele.ss video monitoring of bird nests. Wildlife Society Bulletin 29:349-353. Koerth, B. H., W. M. Webb, F. C. Bryant, and F. S. Guthery. 1983. Cattle trampling of simulated ground nests under short duration and continuous grazing. Journal of Range Management 36:385- 386. Lack, D. 1968. Ecological adaptations for breeding in birds. Methuen, London, United Kingdom. Martin, T. E. 1988. Habitat and area effects on forest bird assemblages: is nest predation an influence? Ecology 69:74-84. Nack, J. L. 2(K)2. Effects of predators and cattle on ground-nesting grassland birds in southwestern Wisconsin pastures. M.Sc. thesis. University t)f Wi.sconsin, Madison. I*aini;, L., D. j. Undi rsandi r, D. W. Sampli;, G. A. Barii;i r, and T. A. SciiAriiMAN. 1996. CAttle trampling of simulated ground nests in rotation- ally grazed pastures. Journal of Range Manage- ment 49:294 .JOO. Paini , L., D. J. Undi.rsandi R, D. W. Sampli , G. A. Barii I r, and '!'. A. .SciiAniMAN. 1997. ('ompar- ison of simulated grouiul nest types for grazing/ trampling research. Journal of Range Management .50:231 233. 1*1 NNiNGTON, M. (i. 1992. Pretlation of binls’ eggs and 62 THE WILSON BULLETIN • Vol. 1 17, No. I, March 2005 chicks by herbivorous mammals. Scottish Birds 16:285. PiETZ, P. J. AND D. A. Granfors. 2000. White-tailed deer (Odocoileus virginianus) predation on grass- land songbird nestlings. American Midland Nat- uralist 144:419-422. Renfrew, R. B. and C. A. Ribic. 2003. Grassland pas- serine nest predators near pasture edges identified on videotape. Auk 120:371-383. Ricklefs, R. E. 1969. An analysis of nesting mortality in birds. Smithsonian Contributions in Zoology, no. 9. Sample, D. W. and M. J. Mossman. 1997. Managing habitat for grassland birds: a guide for Wisconsin. Wisconsin Department of Natural Resources, Madison, Wisconsin. Sample, D. W., C. A. Ribic, and R. B. Renfrew. 2003. Linking landscape management with the conser- vation of grassland birds in Wisconsin. Pages 359-385 in Landscape ecology and resource man- agement: linking theory with practice (J. A. Bis- sonette and I. Storch, Eds.). Island Press, Wash- ington, D.C. Sargeant, a. B., R. j. Greenwood, M. A. Sovada, AND T. L. Shaffer. 1993. Distribution and abun- dance of predators that affect duck production — Prairie Pothole region. Resource Publication, no. 194. U.S. Pish and Wildlife Service, Washington, D.C. Temple, S. A., B. M. Pevold, L. K. Paine, D. J. Un- DERSANDER, AND D. W. SAMPLE. 1999. Nesting birds and grazing cattle: accomodating both on Midwestern pastures. Studies in Avian Biology 19:196-202. Vickery, P. D. and J. R. Herkert. 2001. Recent ad- vances in grassland bird research: where do we go from here? Auk 1 18:1 1-15. Warner, R. E. 1994. Agricultural land use and grass- land habitat in Illinois: future shock for Midwest- ern birds? Conservation Biology 8:147-156. Wilson Bulletin 1 17(1 ):63-7 1, 2005 INFLUENCE OE EORAGING AND ROOSTING BEHAVIOR ON HOME-RANGE SIZE AND MOVEMENT PATTERNS OF SAVANNAH SPARROWS WINTERING IN SOUTH TEXAS DANIEL L. GINTERi AND MARTHA J. DESMOND^ ^ ABSTRACT. — We used radio telemetry to examine Savannah Sparrow (Passerculus sandwichensis) home- range size and foraging and roosting behavior on Padre Island National Seashore in south Texas during January and February, 2002 and 2003. Savannah Sparrows maintained fixed home ranges in winter. Mean home-range size (95% Kernel Home Range [KHR]) was 9.1 ha with a mean core area (50% KHR) of 0.9 ha. Within home ranges, mean foraging and roosting areas were 5.6 and 6.6 ha, respectively. Three distinct habitat types were used by Savannah Sparrows on the island: foredunes (adjacent to the ocean), interior grasslands, and lagoons. Birds using the foredunes had significantly larger home ranges and traveled longer distances between their foraging and roosting locations, always moving inland to roost. Roosting and foraging areas overlapped less for these birds (20%) compared with the overlap for birds found in interior grasslands (45%) and lagoons (55%). The greater distance traveled to roost sites by birds foraging in the foredune habitat appeared to be related to increased exposure in that habitat type. Savannah Sparrows selected foraging areas with less vegetative biomass and more bare ground than random sites. Roost sites had greater total (live) cover than foraging and random sites. Savannah Sparrows foraged alone or in loose aggregations with conspecifics. Birds roosted alone or in aggregations of up to 30 individuals. Savannah Sparrows often roost outside of their foraging areas; this study draws attention to differences in space use for roosting and foraging Savannah Sparrows. Although Savannah Sparrows maintained relatively small home ranges, they occasionally moved at larger spatial scales, suggesting a need for intact grassland patches much larger than the average home-range size. Received 18 February 2004, accepted 6 December 2004. The relationship among foraging- and roost-site selection, behavior, and home-range size is not well understood for non-breeding emberizid sparrows. This is related, in part, to the small size, cryptic coloration, and nomadic nature of some members of this group. The degree of nomadic behavior varies among species and possibly within and among re- gions (Gordon 2000). In Arizona, where seed abundance can vary substantially among patches and winters, Gordon (2000) found that four species of emberizid sparrows all tended to occupy fixed home ranges during the winter period, with the wSavannah Sparrow {Fasser- culus sandwichensis) exhibiting the greatest variation in movcFiicnt patterns. Gordon (2000) found that local movement patterns of wSavannah wSparrows differed between study sites. There is little evidence of .Savannah .Spar- row fidelity to wintering grounds, and move- ment patterns appear to be variable (Odum ' Dept, of I'ishery and Wikllile Sciences, F.O. Box .3()()()3, MSC’ 4901, New Mexico State Univ., I.as rm- ces, NM 88003, USA. ^ C’orresponding author; e-mail: mdesmond Cofiimsu.edu and Hight 1957, Wheelwright and Rising 1993, Gordon 2000, Ginter 2004). Under- standing factors that contribute to variation in the extent of this sparrow’s movements is im- portant for its management and conservation on wintering grounds. Using flush-netting techniques, Odum and Hight (1957) found that winter home-range sizes in Georgia var- ied from 6 to 60 ha. Gordon (2000) did not estimate home-range sizes, but found that Sa- vannah Sparrows in southeastern Arizona tended to remain within a fixed home range and moved an average distance of 186 m be- tween consecutive locations. Using flush-net- ting, Gordon (2000) detected sedentary be- havior at one site and high mobility at another. Intraspecific differences in behavior may re- sult in variation in response to capture using flush-netting (Gordon 2000, Ginter 2004). Ra- dio-telemetry may pro\ ide a better estimate of movement patterns and the degree of seden- tary behavior. Variation in movement patterns may be re- lated to (he distribution of seed resources across the laiulscapc, predator axoitlance. or the distribution of suitable foraging and roost- ing habitat. Other studies have found winter sparrow abundance to be correlated \\ ith seed 63 64 THE WILSON BULLETIN • Vol. 1 17, No. 1, March 2005 production, suggesting that sparrows track re- source abundance (Pulliam and Parker 1979, Grzybowski 1982). Unlike more sedentary grassland sparrows, such as Grasshopper {Am- moclrarnus savannarum), Baird’s {A. bairdii), Henslow’s (A. henslowii), and Cassin’s spar- rows {Airnophila cassinii) that forage within dense grass cover (Pulliam and Mills 1977, Plentovich et al. 1999, Gordon 2000, Carrie et al. 2002), Savannah Sparrows have been observed to forage in open areas with little cover (Grzybowski 1982, Lima 1990, Lima and Valone 1991). Lima and Valone (1991) suggest that predator avoidance is an impor- tant aspect of foraging-site selection for grass- land sparrows. Through experimental manip- ulation, they found that the availability of cov- er changes the composition of the winter avian community. Savannah Sparrows seem to for- age within a matrix of open areas and denser cover (Watts 1991). Although little is known of Savannah Sparrow roost-site selection, most avian species are thought to select winter roost sites with greater vegetative cover due to enhanced microclimate and predator pro- tection (Walsberg and King 1980, Buttemer 1985). We hypothesized that Savannah Spar- row foraging and roosting habitats would dif- fer, and that the distribution of these habitats would contribute to variation in movement patterns. Movement patterns may also be re- lated to seed abundance and we predicted that home-range size would be inversely correlated with seed abundance and biomass. METHODS Study area. — We conducted our study along the Texas coast on Padre Island National Sea- shore. North Padre Island is a long, narrow barrier island approximately 120 X 4 km (Wiese and White 1980), and is characterized by strong, moisture-laden gulf winds (Drawe et al. 1981). Winter temperatures rarely drop below freezing (Drawe and Kattner 1978). Unlike other coastal barrier islands in the Gulf of Mexico, Padre Island has a distinct grass- land component; woody vegetation accounts for less than 0.2% of the plant community (Negrete et al. 1999). The interior grasslands are dominated by little bluestem {Schizachyr- ium scoparium littorale), gulfdune paspalum (Paspalum monostachyum), and bushy blue- stem (Andropogon glomeratus). Upland dune habitats are characterized by seaoats (Uniola paniculata), beach morning-glory (Ipomoea imperati), and partridge pea (Chamaecrista fasciculata). Dominant plants found in and ad- jacent to freshwater marshes are gulf cord- grass (Spartina patens), bulrush (Scirpus pun- gens), and spikerush {Eleocharis flavescens). Primary plants in saltwater marshes are halo- phytic, including shoregrass {Monant hochloe littoralis), saltgrass (Distichlis spicata), glass- wort {Salicornia bigelovii), beachwort (Batis maritima), and sea-ox-eye (Borrichia frutes- cens) (Hatch et al. 1999). Radio telemetry. — We captured birds in- mist nets at 7 sites in 2002 and 1 1 sites in 2003 across the northern 32- X 4-km section of the island. Radio transmitters were placed on 57 Savannah Sparrows during January and February of 2002 and 2003 (21 in 2002 and 36 in 2003). We fitted birds with 0.72-g BD- 2 transmitters (Holohil Systems, Ontario, Can- ada; 4. 0-4. 5% of body weight; mean life span = 26.6 days ± 0.9 SE, range = 21-37 days). We attached transmitters using the leg-back harness technique (Rappole and Tipton 1991). Harness fit was evaluated for each bird prior to release by placing the bird in an enclosure and observing its movements. If a bird’s movements were restricted, the transmitter was removed and the bird was released (C. E. Gordon pers. comm.). Initially, we attempted collecting data at a minimum of four foraging and three roosting locations per week for each bird; however, in 2003 we increased the number of locations be- cause our 2002 data were insufficient for an- alyzing home-range sizes of most birds. Data on foraging locations were collected between 07:00 and 17:00 CST, whereas data on roost- site selection were collected between 20:00 and 05:00. We located most birds visually. If a bird appeared to respond to the observer’s presence before being observed, we used the strength of the radio signal to mark its initial position (Vega Rivera et al. 2003). For each radio-tagged Savannah Sparrow, we recorded whether it was solitary or found in a flock, and we recorded whether the flocks were sin- gle- or mixed-species flocks. We did not re- cord the number of individuals within flocks due to difficulty in determining flock mem- bership. Roosting Savannah Sparrows re- mained stationary when approached and we Ginter and Desmond • SAVANNAH SPARROW WINTER MOVEMENTS 65 tried to avoid flushing them. If we flushed a radio-tagged sparrow from its roost site, we recorded the number of individuals in close proximity (within a 2-m radius) to the radio- tagged bird. All locations where birds were first observed were marked in UTM coordi- nates with handheld Garmin GPS units. We examined Savannah Sparrow use of three distinct habitat types within specific geo- graphic areas on the island: (1) foredunes, which separate the beach front from the inte- rior habitats; (2) interior grasslands; and (3) the edge of the lagoon (Laguna Madre). We classified radio-tagged Savannah Sparrows by habitat type and calculated foraging and roost- ing areas for each habitat. We calculated the distance from the center of the bird’s estimat- ! ed foraging area to each nocturnal roost lo- cation to determine the mean distance traveled between foraging and roost sites. We also cal- t culated the percentage of the roosting home range that overlapped with the foraging area. Habitat measurements. — Over the two win- I ters, we measured the structural characteristics j of the vegetation at five randomly selected i foraging locations per bird {n = 46 Savannah Sparrows), five roosting locations per bird {n = 44 Savannah Sparrows), and at paired ran- dom points. Random locations were selected I by choosing a random azimuth (0-360°) and ' a random distance between 0 and 50 m; we used the foraging and roosting locations as I center points and the algorithm suggested by Skalski (1987) to correct for bias when sam- i pling in circular plots. A visual obstruction reading (VOR, an index of vegetation bio- mass), was taken using a Robel pole at each I location with four readings per point (Robel et al. 1970). A Daubenmire frame (20 X 50 cm) was used to estimate percent grass, forb, litter, woody, and total (all live vegetation) cover and bare ground (Daubenmire 1959). We measured maximum height of grass and forbs (the tallest plant in each frame) and the depth of horizontal vegetation within the Dau- benmire frame (Desmond 2004). In 2003, we quantified seed abunckmcc and I biomass by collecting surface soil samples at 10 foraging locations and 10 randomly se- lected paired points for nine Savannah Spar- ; rows selected randomly from our radio-tagged birds. Random points were selected using the same criteria outlined above. We collected four subsamples at each location and each ran- dom point. The four subsamples were chosen randomly from within a 1-m radius. We placed an 8.6-cm-diameter metal hoop on the ground and scooped the soil from inside the hoop to a depth of 0.8 cm for a total of 46.4 X 4 cm^ of soil per sample. This technique is a modification of the method used by Grzy- bowski (1982). Samples were placed in la- beled bags and dried at 50° C for approxi- mately 24-48 hr. To analyze seed samples, a hydropneumatic root elutriator was used to separate inorganic from organic material (Gross and Renner 1989). Seeds were separated from the remain- ing organic material using tweezers and a lOX magnification microscope (Pulliam and Brand 1975). Seeds were identified to genus, and, when possible, to species. For each sample, seeds were counted and weighed to the nearest one-thousandth of a gram. Seeds >5 mm in length or width were not included in the anal- yses. Data analyses. — We used a non-parametric Kernel Home Range (KHR) estimator to de- termine the size of the home range for each bird; the KHR estimates the minimum area in which a Savannah Sparrow had a specific probability of being located (Worton 1995, Seaman and Powell 1996). We calculated a fixed KHR at 50% (core area) and 95%, and calculated smoothing parameters using least squares cross-validation (Seaman and Powell 1996, Hooge and Eichenlaub 1997). Cross- validated fixed-kernel home ranges have been found to be the most accurate of the home- range estimators (Seaman and Powell 1996). We used the ANIMAL MOVEMENTS exten- sion program for AreView 3.2 to perform cal- culations of the 50% and 95% KHR estimates (Hooge and Eichenlaub 1997). KHR estimates were calculated separately for foraging and roosting locations, and all locations combined (combined home range). Consecuti\e loca- tions for individual sparrows were separated by a minitnum of 12 hr and we used only those birds for which we had >20 telemetry locations, 'fhis resulted in >20 locations for foraging areas and combined home-range siz- es but fewer (mean = 13) for roosting areas. However, the standartl errors for foraging- aiul roosting-arca estimates were similar and we believe the tiata pro\idcd a good estimate of 66 THE WILSON BULLETIN • Vol. 1 17, No. I, March 2005 TABLE 1. Mean and range (ha) of winter home-range size, foraging area, roosting area, and core foraging area, and number of telemetry locations (SE) for Savannah Sparrows (n = 28) on Padre Island National Seashore, Texas, during January and Lebruary, 2002 and 2003. Home ranges and forging and roosting areas were calculated using a 95% Kernel Home Range (KHR) estimator; a 50% core estimator was used for core foraging areas. Area estimated Size (SE) Range in area No. telemetry locations 95% KHR Home range 9.1 (1.8) 0.2-31.7 35 (1.8) Loraging area 5.6 (0.8) 1.0-19.8 22 (1.2) Roosting area 6.6 (1.0) 0.4-17.9 13 (0.8) 50% KHR Core foraging area 0.9 (0.2) 0.9-4. 1 22 (1.2) roosting patterns (Table 1). Each bird was fol- lowed until the transmitter battery died, the bird lost its transmitter, the signal disappeared, or there was a conhrmed mortality. A Kruskal-Wallis test was used to examine, by habitat type, size differences in foraging areas, roosting areas, and home-ranges. We also compared mean distance traveled be- tween foraging and roosting sites and tested for differences in percentage overlap between roosting and foraging areas among the three habitat types. For all Kruskal-Wallis tests we report the exact chi-square. All statistical anal- yses were performed using SAS 8.02 (SAS Institute, Inc. 1990). Vegetation associations were evaluated by comparing foraging and roosting locations with each other and with paired randomly se- lected points; we used paired r-tests to analyze these data. We performed Shapiro-Wilkes tests to determine whether variables were nor- mally distributed. When appropriate, we trans- formed data using a square-root transforma- tion. To adjust for significance when perform- ing multiple tests, we used the sequential Bon- ferroni correction (Rice 1989). We used Spearman rank correlation to test for a rela- tionship between seed abundance and size of the 95% foraging KHR. Home-range sizes and vegetation characteristics are reported as means ± SE. RESULTS Of 57 Savannah Sparrows fitted with trans- mitters, we had a sufficient number of loca- tions to calculate home-range size for 28 birds. With the exception of four birds dis- cussed below, the birds excluded from anal- yses were those that died, slipped their trans- mitters, or for which we had insufficient data (in 2002). There were three confirmed mor- talities in 2002 and five in 2003. Because we detected no differences in between-year home-range sizes, we combined data from the two winters. The mean home-range size (95% KHR) was 9.1 ha and mean foraging and roosting areas were 5.6 and 6.6 ha, respec- tively; the mean core foraging area (50% KHR) was 0.9 ha (Table 1). We had difficulty locating four birds: two disappeared and two exhibited large-scale movement. One sparrow moved to a site approximately 2 km from its point of capture, where it remained for 5 days before returning and then permanently disap- pearing. A second bird moved 800 m from its point of capture, where it remained until it lost its transmitter 6 days later. Each radio-tagged sparrow foraged within a flock on at least one occasion. When foraging in flocks. Savannah Sparrows always foraged with conspecifics in loose aggregations (birds 1-10 m apart but ap- parently in vocal communication). We ob- served a mean of 1.3 ± 0.4 (n = 43) sparrows roosting within approximately 2 m of radio- tagged Savannah Sparrows. Although we sus- pect that radio-tagged Savannah Sparrows were roosting only with conspecifics, this could not be confirmed due to the difficulty of identifying them at night. There were no detectable differences in siz- es of foraging and roosting areas among birds using foredune, lagoon, and interior habitats (xWg = 1-38, df = 2, P = 0.50; x^oosung = 5.15, df = 2, P = 0.081; Table 2). Home- range size did differ among the three habitat types (x^ = 8.73, df = 2, P - 0.010; Table 2); mean home-range size of sparrows using the foredune habitat was larger than that of Ginter and Desmond • SAVANNAH SPARROW WINTER MOVEMENTS 67 TABLE 2. Kernel Home Range (95%) size (SE) for Savannah Sparrows, by habitat type, on Padre Island National Seashore, Texas, during January and February, 2002 and 2003. Different letters within columns denote significant between-habitat differences (Kruskal-Wallis test: P < 0.05). Habitat (/;) Home range (ha) No. locations Foraging area (ha) No. locations Roosting area (ha) No. locations Foredune (7) Grassland (13) Laguna Madre (8) 16.6 (3.3) A 7.0 (1.6) B 5.9 (1.7) B 34.0 (4.5) 33.2 (2.5) 41.2 (3.6) 5.7 (1.3) A 6.1 (1.0) A 4.4 (1.0) A 21.9 (3.1) 20.8 (1.5) 25.0 (2.0) 9.9 (1.4) A 10.0 (4.6) A 5.7 (1.8) A 12.1 (1.5) 12.4 (1.1) 16.2 (1.7) sparrows using the other two habitat types. The mean distance traveled between the center of the estimated foraging areas and roosting locations differed among the three habitat types (x^ = 10.29, df = 2, = 0.026). Spar- rows using foredune habitat traveled farther between the centers of their foraging areas and roosting locations (mean = 337 m) than birds using interior grasslands (mean = 108 m) or lagoons (mean = 107 m). The percentage of overlap between roosting and foraging areas differed among the three habitat types (x“ = 7.43, df = 2, P = 0.020). Overlap for spar- rows using foredune habitat was minimal (20%), whereas it was 45 and 55% for birds using interior grassland or lagoon habitats, re- spectively (Fig. 1 ). For example, there was no overlap of roosting and foraging areas for bird #279, but some birds using interior grassland and lagoon habitats had roosting areas com- pletely contained within the foraging area (#840) or vice versa (#71); others had some overlap, but also maintained distinct foraging and roosting areas (#959). Foraging areas had more bare ground and less VOR and horizontal depth than randomly selected points. When compared with roosting sites, foraging sites had more bare ground, less total cover, and lower horizontal depth. Roost sites had greater total cover and grass cover than randomly selected sites (Table 3). Seed biomass did not differ between for- aging and random sites and was positively correlated with the size of the 95% foraging KHR (Spearman rank correlation: r = 0.68, P = 0.042). On the other hand, seed abundance was significantly greater in samples collected at foraging sites compared with random sites ( Wilcoxon-Mann-Whitney (/-test = 62.5, = 0.043). 'fhere was no relationship between seed abundance at foraging sites and size of the 95% foraging KHR (Spearman rank cor- relation: r = 0.28, P = 0.46). Seed biomass and abundance included seeds of all shapes and sizes that could be reasonably consumed by Savannah Sparrows; seeds >5 mm in width or diameter were excluded from the analyses. The most common seed species were present at both foraging and random lo- cations and included little bluestem, Cypenis spp., Eleocharis spp., camphorweed {Hetero- theca subaxillaris), Dichanthelium spp., Pas- palum spp., fall witchgrass (Digitaria cogna- ta), and panicgrass {Panicum amarum). DISCUSSION Savannah Sparrows exhibited strong sed- entary behavior within winters; the majority of their foraging movements were restricted to an average core area of approximately 1 ha. The scale of movement detected in this study was smaller than previously estimated. How- ever, we did observe extremes in home-range size ranging from 0.15 to 31.7 ha. We also observed large-scale movements of two Sa- vannah Sparrov.'s not included in the home- range analyses, with one moving as far as 2 km from its point of capture. Two radio- tagged sparrows disappeared altogether from the study area. Using a flush-netting tech- nique, Gordon (2()()0) recaptured 3.8% (within winters) of the Savannah Sparrows banded on 7-ha plots, but had much higher recapture rates for Baird's, Grasshopper, Vesper {Pooe- cetes gra/ninens), and Cassin's sparrows. The low recapture rate for Savannah Sparrows in Arizona may indicate that the average winter home-range size is larger there than it is in coastal south fexas. or it may indicate that radio telemetry is a more reliable method for estimating home-range size and the tlegree of sedentary behavior for this species. Our study is the first to use radio telemetry to estimate winter home-range size for Savannah Spar- rows. 'file small, average home-range size in south fcxas may iiulicate a reliable resource 68 THE WILSON BULLETIN • Vol. H7, No. I, March 2005 Foraging VTA Roosting Bird #840 (grassland) Bird #959 (grassland) Bird #71 (lagoon) 0.4 0.8 5 km Bird #279 (foredune) FIG. I. Examples of distribution of foraging and roosting areas within home ranges of four Savannah Sparrows wintering on Padre Island National Seashore, Texas, January and February, 2002 and 2003. The roosting area of bird #840 (interior grasslands habitat) was 100% contained within its foraging area; 71% of the roosting area of bird #959 (interior grasslands habitat) was contained within its foraging area; 100% of the foraging area of bird #7 1 fell within its roosting area. There was no overlap between roosting and foraging areas of bird #279 (foredune habitat). base to maintain sparrows within a small area throughout the winter period. Alternatively, Savannah Sparrows may tend to occupy rel- atively small areas (1 ha) for short periods of time (1-2 months), but may occasionally wan- der at larger spatial scales during the course of the winter (November-March). This could explain the large-scale movement we ob- served for two sparrows in this study, and the high degree of variability in recapture rates between sites in Arizona (Gordon 2000). Movement patterns between roosting and foraging sites have not been previously re- ported for wintering Savannah Sparrows. The mean distance moved from the center of for- aging areas to roosting sites was 165 m, with Ginter and Desmond • SAVANNAH SPARROW WINTER MOVEMENTS 69 TABLE 3. Comparisons of mean vegetative structure at foraging, random, and roosting areas within Savan- nah Sparrow home ranges during January and February, 2002 and 2003 on Padre Island National Seashore, Texas. Asterisks denote significant differences (paired r-test: P < 0.05) between paired locations. Foraging versus Roosting versus Foraging versus random areas (SE) random areas (SE) roosting areas (SE) Variable Foraging Random Roosting Random Foraging Roosting % Grass 66.2 (3.3) 59.1 (3.0) 76.9 (3.3)* 62.7 (3.4)* 68.9 (3.3) 69.0 (3.7) % Forb 24.9 (3.0) 32.1 (2.8) 21.6 (3.3) 25.2 (2.5) 22.8 (3.0) 27.7 (3.7) % Bare ground 41.7 (2.2)* 31.2 (2.1)* 30.6 (2.5) 35.8 (2.7) 41.8 (2.2)* 32.2 (2.2)* % Leaf litter 8.1 (1.7) 7.4 (1.7) 4.1 (0.7) 8.5 (2.0) 7.7 (1.7) 6.0 (1.2) % Total cover'’ 50.8 (2.0) 58.5 (2.4) 65.3 (2.2)* 53.8 (2.9)* 50.6 (2.0)* 61.8 (2.5)* Vegetation biomass*’ 1.1 (0.1)* 1.5 (0.1)* 1.3 (0.1) 1.4 (0.1) 1.1 (0.1) 1.3 (0.1) Horizontal depth (cm) 3.6 (0.5)* 6.8 (0.8)* 5.7 (0.6) 5.1 (0.7) 3.7 (0.5)* 5.4 (0.5)* Maximum grass height (cm) 25.5 (1.7) 31.6 (1.9) 33.2 (1.8) 34.4 (2.4) 26.6 (1.7) 28.3 (1.5) ^ Total cover (grass, forb, woody). •’Vegetation biomass as indexed by visual obstruction readings (Robel et al. 1970). some iruJividuals traveling 400-600 m. BircJs foraging along the foredunes (nearest to the ocean) always moved inland to roost and trav- eled the greatest distance to roosting sites; there was little overlap between roosting and foraging areas of these birds. The home-range configuration of sparrow #279 illustrates the separation of foraging and roosting locations used by birds in foredune habitat (Fig. 1). Foredunes, which sometimes extend no far- ther inland from the ocean than 100 m, are subject to the harshest environmental condi- tions on the island. Movement inland by roosting Savannah Sparrows is likely an at- tempt to escape exposure to the persistent winds coming off the Gulf of Mexico and to find appropriate roosting microhabitat. Savannah Sparrows, the dominant winter sparrows on the island, foraged in open areas either as solitary individuals or as members of loosely spaced aggregations of conspecifics. Open areas likely provide easier access to available resources. These birds also foraged in areas with higher seed abundance than ran- domly selected locations, suggesting that they may cue in on resource abundance. Gr/y- bowski (1982, 1983) also found individual and loose aggregations of Savannah Sparrows foraging in areas with low vegetation height and density. Although he did not examine Sa- vannah Sparrows specifically, he found a pos- itive relationship between avian density and seed abundance. Variation in the abundance of wintering emberi/id sparrows has been linked to .seed production in southeastern Arizona (Pulliam and Brand PJ75, Dunning and Brown 1982). We predicted that foraging ar- eas would be smaller where abundance and biomass of seeds were greater. The lack of a negative relationship suggests that factors oth- er than seed abundance — such as proximity to the coast, the distribution of suitable foraging and roosting patches, or predator avoidance — influence winter home-range size and may also influence the variation observed in Sa- vannah Sparrow movements. The small sam- ple size (nine birds) also may have contributed to the lack of an observed relationship. Savannah Sparrows foraged in open areas within a matrix of open areas and denser veg- etation. This was evident from the greater vegetative biomass at random points com- pared with that of foraging sites within indi- vidual home ranges. Other studies report that wintering Savannah Sparrows forage in open areas adjacent to cover, and suggest that near- by vegetative cover may offer protection from predators (Pulliam and Mills 1977, Watts 1991). This has also been reported for other wintering sparrow species (Lima 1990, Lima and Valone 1991). The foredune habitat u.sed by some sparrows on Padre Island is espe- cially patchy, and may be attractive as forag- ing habitat, despite the longer distances be- tween foredunes and roosting sites. Savannah Sparrow roosting sites were often interspersed within or around foraging loca- tions (Pig. 1 ), aiul they had greater total cover than foraging and random sites. Greater hori- zontal vegetation tlepth at roost sites may be important because it provides space for birds to roost aiul move under the vegetation with- 70 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 out being exposed. Although temperatures rarely dip below freezing in south Texas, fre- quent winter storms and winds coming off the Gulf Coast likely affect the energy expendi- ture of roosting individuals. As a result, spar- rows roost in areas that provide greater pro- tection from climatic factors, and individuals foraging close to the coast travel farther inland to roost. Other studies of roost-site selection suggest that individuals select sites with the greatest microclimate protection (Kendeigh 1960, Gottfried and Franks 1975, Gyllin et al. 1976, Buttemer 1985). Greater cover could serve to reduce predation risk and provide in- creased protection from exposure, thus reduc- ing overnight energy expenditure (Walsberg and King 1980). We were able to approach roosting Savannah Sparrows within 1 m, but we were unable to determine the exact prox- imity of individuals roosting in aggregations. It was apparent, however, that some individ- uals roosted close together. The mean number of birds roosting in close proximity to each other was low (<5 sparrows), but variation was high. We sometimes observed as many as 30 sparrows roosting in close proximity, sug- gesting that Savannah Sparrows may derive a benefit from communal roosting, such as re- duced predation risk or energy conservation. Other avian species also roost in aggregations during the winter months (Walsberg 1990, Heinrich 2003). With the exception of studies on species that form large communal roosts, studies of nonbreeding passerines have gen- erally disregarded roosting behavior and roost-site selection, often with the assumption that diurnal movement patterns encompass the roosting areas. Our study shows that the dis- tribution of foraging and roosting habitat in- fluences movement patterns and overall home- range size; Savannah Sparrows often roost outside of their foraging areas, and they have specific habitat requirements for foraging and roosting locations. ACKNOWLEDGMENTS We thank D. L. Echols and all the personnel at Padre Island National Seashore for their support and assis- tance throughout this study. We thank I. D. Parker for his dedication and long hours in the field. L. B. Abbott generously provided access to her root elutriator for separating seed samples. M. D. Gill and R. L. Ko- chevar assisted with seed identification. W. R. Gould provided statistical advice. D. E Caccamise, C. E. Gor- don, W. R. Gould, J. D. Rising, J. M. Ruth, J. H. Vega Rivera, and N. T. Wheelwright provided helpful com- ments on earlier drafts of this manuscript. Eunding was provided by the National Park Service through the De- sert Southwest Cooperative Ecosystem Study Unit and the U.S.-Mexico Affairs Office; T & E, Inc.; the Na- tional Science Eoundation-funded ADVANCE Insti- tutional Transformation Program at New Mexico State University, fund #NSE0 123690; and New Mexico State University. This is a contribution of New Mexico State University, College of Agriculture and Home Economics, Agricultural Experiment Station. LITERATURE CITED Buttemer, W. A. 1985. Energy relations of winter roost-site utilization by American Goldfinches (Carduelis tristis). Oecologia 68:126-132. Carrie, N. R., R. O. Wagner, K. R. Moore, J. C. Sparks, E. L. Keith, and C. A. Melder. 2002. Winter abundance and habitat use by Henslow’s Sparrows in Louisiana. Wilson Bulletin 114:221- 226. Daubenmire, R. E 1959. Canopy coverage method of vegetation analysis. Northwest Science 33:43-64. Desmond, M. J. 2004. Effects of grazing practices and fossorial rodents on a winter avian community in Chihuahua, Mexico. Biological Conservation 1 16: 235-242. Drawe, D. L. and K. R. Kattner. 1978. Effect of burning and mowing on vegetation of Padre Is- land. Southwestern Naturalist 23:273-278. Drawe, D. L., K. R. Kattner, W. H. McEarland, and D. D. Neher. 1981. Vegetation and soil properties of five habitat types on North Padre Island. Texas Journal of Science 33:145-157. Dunning, J. B. and J. H. Brown. 1982. Summer rain- fall and winter sparrow densities: a test of the food limitation hypothesis. Auk 99:123-129. Ginter, D. L. 2004. Wintering ecology and behavior of grassland sparrows on North Padre Island, Tex- as. M.Sc. thesis. New Mexico State University, Las Cruces. Gordon, C. E. 2000. Movement patterns of wintering grassland sparrows in Arizona. Auk 1 17:748-759. Gottfried, B. M. and E. C. Eranks. 1975. Habitat use and flock activity of Dark-eyed Juncos in win- ter. Wilson Bulletin 87:375-383. Gross, K. L. and K. A. Renner. 1989. A new method for estimating seed numbers in soil. Weed Science 37:836-839. Grzybowski, j. a. 1982. Population structure in grass- land bird communities during winter. Condor 84: 137-152. Grzybowski, J. A. 1983. Patterns of space use in grassland bird communities during winter. Wilson Bulletin 95:591-602. Gyllin, R., H. Kallander, and M. Sylven. 1976. The microclimate explanation of town centre roosts of Jackdaws Corvus monedida. Ibis 119:358-361. Hatch, S. L., J. L. Schuster, and D. L. Drawe. 1999. Ginter and Desmond • SAVANNAH SPARROW WINTER MOVEMENTS 71 Grasses of the Texas gulf prairies and marshes. Texas A&M University Press, College Station. Heinrich, B. 2003. Overnighting of Golden-crowned Kinglets during winter. Wilson Bulletin 115:113- 114. Hooge, P. N. and B. Eichenlaub. 1997. Animal move- ments extension for ARC- VIEW, ver. 1.1. Alaska Biological Science Center, U.S. Geological Sur- vey, Anchorage, Alaska. Kendeigh, S. C. 1960. Energy of birds conserved by roosting in cavities. Wilson Bulletin 73:140-147. Lima, S. L. 1990. Protective cover and the use of space: different strategies in finches. Oikos 58: 151-158. Lima, S. L. and T. J. V alone. 1991. Predators and avian community organization: an experiment in a semi-desert grassland. Oecologia 86:105-112. Negrete, I. G., A. D. Nelson, J. R. Goetze, L. Macke, T. Wilburn, and A. Day. 1999. A check- list for the vascular plants of Padre Island National Seashore. Sida, Contributions to Botany 18:1227- 1245. Odum, E. P. and G. L. Hight. 1957. The use of mist nets in population studies of wintering fringillids on the AEC Savannah River Area. Bird-Banding 28:203-213. Plentovich, S. N., R. Holler, and G. E. Hill. 1999. Habitat requirements of Henslow’s Sparrows win- tering in silvicultural lands of the Gulf Coastal Plain. Auk 1 16:109-1 15. Pulliam, H. R. and M. R. Brand. 1975. The produc- tion and utilization of seeds in a desert grassland. Ecology 56:1 158-1 166. Pulliam, H. R. and G. S. Mills. 1977. The use of space by wintering sparrows. Ecology 58:1393- 1 399. Pulliam, H. R. and T. A. Parker, 111. 1979. Popula- tion regulation of sparrows. Eortshritte der Zool- ogie 25:137-147. Rappole, j. H. and a. R. Tipton. 1991. New harness design for attachment of radio transmitters to small passerines. Journal of Eield Ornithology 62: 335-337. Rice, W. R. 1989. Analyzing tables of statistical tests. Evolution 43:223-225. Robel, R. j., j. N. Briggs, A. D. Dayton, and L. C. Hulbert. 1970. Relationships between visual ob- struction measurements and height of grassland vegetation. Journal of Range Management 23: 295-298. SAS Institute, Inc. 1990. SAS/STAT user’s guide, ver. 8, 4th ed. SAS Institute Inc., Cary, North Car- olina. Seaman, D. E. and R. A. Powell. 1996. An evaluation of the accuracy of Kernel density estimators for home range analysis. Ecology 77:2075-2085. Skalski, j. R. 1987. Selecting a random sample of points in circular field plots. Ecology 68:749-749. Vega Rivera, J. H., D. Ayala, and C. A. Haas. 2003. Home range size, habitat use, and reproduction of the Ivory-billed Woodcreeper (Xiphorhynchns fla- vigaster) in dry forest of western Mexico. Journal of Eield Ornithology 74:141-151. Walsberg, G. E. 1990. Communal roosting in a very small bird: consequences for the thermal and res- pirating gas environment. Condor 92:795-798. Walsberg, G. E. and J. R. King. 1980. The thermo- regulatory significance of the winter roost-sites se- lected by robins in eastern Washington. Wilson Bulletin 92:33-39. Watts, B. D. 1991. Effects of predation risk on dis- tribution within and between habitats in Savannah Sparrows. Ecology 72:1515-1519. Weise, B. R. and W. a. White. 1980. Padre Island National Seashore: a guide to the geology, natural environments, and history of a Texas barrier is- land. Bureau of Economic Geology. University of Texas, Austin. Wheelwright, N. T. and J. D. Rising. 1993. Savannah Sparrow {Passercidns sandwichensis). The Birds of North America, no. 45. WoRTON, B. J. 1995. Using Monte Carlo simulations to evaluate Kernel-based home range estimators. Journal of Wildlife Management 59:794-800. Wilson Bulletin 1 1 7( 1 ):72-84, 2005 BREEDING ECOLOGY OF THE PUAIOHI (MYADESTES PALMER!) THOMAS J. SNETSINGER,' 23.6 CHRISTINA M. HERRMANN,* 23 DAWN E. HOLMES,'^ CHRISTOPHER D. HAYWARD,'3 AND STEVEN G. FANCY* 5 ABSTRACT— We studied the breeding ecology of the critically endangered Puaiohi (Myadestes palrneri) a poorly known Hawaiian thrush endemic to the island of Kauai. From 1996 through 1998, we monitored 96 active nests over the course of three breeding seasons. Mean clutch size was 2.0, and pairs produced an average of 1 .5 fledglings/successful nest. Pairs renested after failure and some raised multiple broods. The mean annual reproductive effort was 2.1 nesting attempts/territory, and pairs produced a mean 1.1 fledglings/attempt. Large differences m nesting effort and productivity occurred among years, with mean number of fledglings/territory ranging from 0.4 to 4.9. Predation by owls (probably Short-eared Owls, Asia flammeiis) and introduced rats (probably black rats, Rattus rattus) accounted for most nest failures. The presence of non-breeding floaters in the population and their largely unsuccessful attempts to gain territories in the study area suggest that the population IS near carrying capacity. The high reproductive potential of the Puaiohi may help explain its per- sistence despite the species’ historical rarity. Received 29 April 2004, accepted 22 November 2004 The Puaiohi {Myadestes palrneri) is a rare and poorly known thrush restricted to forests above 1 ,000 m elevation on the island of Kau- ai in the Hawaiian Islands. Of the five Ha- waiian thrushes, it is the most divergent vo- cally, morphologically, and behaviorally (Pratt 1982). Except for the Omao (M. obscurus) on the island of Hawaii, the other species are considered critically endangered or extinct (Collar et al. 1994, Reynolds and Snetsinger 2001). Intensive efforts over the last 4 decades to document the status of Hawaii’s forest birds suggested that the Puaiohi was exceedingly rare and had experienced a range contraction since the 1960s (Sincock et al. 1984, Scott et al. 1986, Pyle 1994). In the course of these studies, a number of factors were implicated in the loss of Hawaii’s forest bird populations. It is thought that habitat modification, avian disease, competition, and predation have acted in concert to diminish available habitat and * U.S. Geological Survey, Pacific Island Ecosystems Research Center, RO. Box 44, Hawaii National Park, HI 96718, USA. 2 Pacific Coop. Studies Unit, Dept, of Botany, Univ. of Hawaii, Honolulu, HI 96822, USA. 3 Current address; 35289 Washburn Heights Dr., Brownsville, OR 97327, USA. ^ Current address; 54 Wildflower Dr., Amherst, MA 01002, USA. ^ Current address; National Park Service, 1201 Oak Ridge Dr., Ste. 200, Fort Collins, CO 80525-5596, USA. ^Corresponding author; e-mail; puaiohi@peak.org reduce survival and reproduction. Surveys conducted by the U.S. Fish and Wildlife Ser- vice (USFWS) and Hawaii Department of Land and Natural Resources (DLNR) in 1993 and 1994 suggested that the Puaiohi was on the brink of extinction (USFWS, DLNR un- publ. data). Published descriptions of three known Pu- aiohi nests suggest that the Puaiohi usually nests on cliffs along streambeds (Kepler and Kepler 1983, Ashman et al. 1984, Harrity et al. 1995). These descriptions, along with a few incidental observations and a sparse rec- ord of published anecdotal information (Per- kins 1903, Richardson and Bowles 1964), were all that was known of the breeding bi- ology and life history of the Puaiohi. The dis- covery in April 1995 of a fledgling Puaiohi and at least three breeding pairs on the Alakai Plateau of Kauai, near the Koaie Stream Gauging Station (Harrity et al. 1995), prompt- ed a 3-year interagency study. The goals of the study were to determine the status of the population, collect life-history information, assess limiting factors, and develop and eval- uate management strategies to promote the protection and expansion of this species into appropriate habitat within its historical range. Concurrently, the Zoological Society of San Diego (ZSSD) and U.S. Geological Survey (USGS) developed captive propagation and release techniques for the closely related Omao to assist in expanding the range of the Hawaiian Myadestes (Kuehler et al. 2000, 2001; Fancy et al. 2001). 72 Snetsinger et al. • PUAIOHI BREEDING ECOLOGY 73 Kauai Area of detail Hawaiian Islands Hanalei FIG. 1. Upper Mohihi, lower Mohihi, and upper Kawaikoi Puaiohi study areas (shaded) on the island of Kauai (1995-1998). Contours are 150 m apart. METHODS Study area. — We established a base camp at the Koaie Gauging Station at the 4.0-mile (6.5 km) marker along the Mohihi-Waialae Trail (Fig. 1) due to its proximity to previously not- ed Puaiohi breeding activity. During Septem- ber 1995-January 1 996, we conducted prelim- inary surveys in this area and other areas of suitable habitat. We monitored these areas Irom 1996 through 199S. I hrough our initial surveys we located a population concentration at 1,250 m elevation along the upper stretches of the Mohihi Stream and its tributaries, and we selected a 2-km- study area that included 66 ha along 3.8 km of the Mohihi Stream bot- tom. We also found several isolated Puaiohi pairs in the neighboring Koaie drainage and monitored their breeding activity as well. Lastly, we selected 4 km of stream bottom on the lower Mohihi Stream (where Puaiohi were rare) and 8 km of stream bottom and trails in the upper Kawaikoi Stream tlrainage (where Puaiohi were not detectetl) to conduct Puaiohi surveys aiul habitat-related research. riic vegetation at each of the three study areas (upper Mohihi and territories in the ad- 74 THE WILSON BULLETIN • Vol. Ill, No. 1, March 2005 jacent Koaie drainage, lower Mohihi, and up- per Kawaikoi) was dominated by a dense ohia (Metrosideros polymorpha) canopy. A wide variety of other trees and shrubs made the for- est structurally diverse with a dense, well-de- veloped understory. The rainy season extend- ed from November through March and was wet but variable, with an average daily rainfall of 19.2 mm/day for 1995-1996 and 1996- 1997. The mean daily rainfall for the same period in 1997-1998 was just 6.5 mm/day. The upper Mohihi differed from both the low- er Mohihi and upper Kawaikoi in having nar- rower, steeper drainages with more vertical cliff walls. Nest monitoring. — We searched for nests at known activity centers at least once every 3 days from the onset of breeding in March through the end of breeding in September (August in 1998). Weather permitting, we checked nests every other day and recorded the status: inactive (under construction, fledged, failed, or in latency — the lag between nest completion and the first egg), laying, in- cubating, hatching, nestling, or unknown. We counted nestlings and/or eggs when this could be done without undue disturbance to the nest. Using a combination of clues, we attempted to determine the cause of nest failures. We attributed predation to owls if the nest was completely removed and if we had observed owl activity nearby prior to predation. If we found partially eaten remains of young or adults or the presence of rat feces in the nest, we concluded that rat predation was the cause of nest failure. For each year we report the mean ± SD for the various stages of nesting and the length of the breeding season (annual period from mean first egg laid date through mean final nest failure or fledge date), which was determined for pairs in which all breeding activity was documented within a year. Every 1-3 days we monitored selected {n = 43) nests for 1-4 hr during all stages of nesting to determine nest attendance rates and nestling food requirements. We monitored ac- tivity with a spotting scope or binoculars from a blind (15-50 m from the nest) or, if blind placement was not possible, from a sufficient distance so as not to influence normal behav- ior. Observers recorded all nest activity (sex and age of the attending bird, behavior, time, and weather conditions) by dictating into a micro-cassette recorder. When a bird was not identifiable by the presence of a unique breast pattern of retained juvenile feathers or color bands, age was determined by the presence or absence of retained juvenile scalloping. Sex of unknown birds was determined by behavior (brooding and incubating were associated only with females in this study), evidence of a brood patch (females; Ashman et al. 1984, this study), or the concurrent observation of the bird’s known-sex mate (e.g., the male was singing from a perch near the nest; only males sang in this study) and no evidence of helper activity at the nest. Additionally, in 1997, while adults were absent from nests, we mea- sured and described eggs {n = 29) and color- banded, weighed, and measured nestlings {n = 20). We found nearly all Puaiohi nests on shelves or in cavities of streamside cliff walls. Once nests were no longer active, we recorded wall height at the nest, nest height on the wall, cavity or shelf dimensions (maximum depth, height, width), concealment (single ground- based visual estimate of how obscured [%] the nest was from a distance of 5 m from the nest), wall vegetation, distance to flowing stream, and direction of exposure. We record- ed nest material for nests in fresh condition and took the following nest measurements: overall height, depth of cup, width of rim, and diameter of cup. Nest characteristics are re- ported as means ± SD. Sample sizes varied for some characteristics, as nest and cavity measurements required close inspection of the nest site and many nests were too high to al- low for this. In other cases we failed to collect complete information. Territory size and spacing. — The rugged terrain made it impossible to follow individual Puaiohi and map territory boundaries. How- ever, we were able to map locations of nests and sightings of color-banded birds using compass bearings and measured distances from known points on a 1:1,000 scale map of the study area. Using plotted positions for ac- tive nests, we measured the straight-line dis- tance to the nearest neighbor’s active nest, and report the mean of this value as a measure of nest density. When an active nest was sur- rounded by neighboring territories that were occupied by non-nesting Puaiohi, we recorded no value. Snetsinger et al. • PUAIOHI BREEDING ECOLOGY 75 Management intervention. — We removed eggs from some nests for captive propagation and poisoned rats in the vicinity of active nests to reduce rodent predation. Eggs were taken from one inactive and six active nests over the course of the study (seven eggs from three nests in 1996 and eight eggs from four nests in 1997). We distributed four tamper-re- sistant bait stations containing 227 g each of Eaton’s Bait Block Rodenticide (contains 0.005% diphacinone) evenly on the ground below nests {n = 27) and 5-20 m from the base of the nest cliff. Bait stations were placed only around nests that were found at least 1 week before fledging. Rats must repeatedly in- gest the diphacinone bait over approximately 7 days for the bait to be effective, and recent fledglings often perch low in bushes or on the ground for a few days after leaving the nest, making them susceptible to rat predation. We checked and replaced bait weekly according to label instructions. Because protecting nests of this species was a high priority, nests were not randomly selected for bait treatment. We did not treat nests discovered within 7 days of fledging, those >20 m high, those where ter- rain did not allow access to the base of the nest wall, and those discovered when person- nel were insufficient to maintain the bait sta- tions. We tested for independence of nest fate for nests that were and were not protected by rat poisoning using a chi-square test (Statistix for Windows 2.0, a = 0.05). Nest fate was cate- gorized as failed (four categories) or fledged. The four failure categories were rat predation, owl or unknown predation, non-predation fail- ure, and unknown. We attempted to minimize the effects of our interventions on our data. We did not use data on nests from which eggs were removed for captive propagation in the calculation of breeding season length or fecundity statistics. In determining nest survival rates (see below), we used data only from unprotected nests. As most of the nests from which eggs were re- moved for captive propagation were in the middle of our study area, the effect of these artilicial failures could have had unknown ef- fects on neighboring territories. Similarly, rat control at nests may have inllucficetl rat pop- ulations at neighboring nests where there was no rat control. Both etfects are likely negli- gible, given the Puaiohi’s propensity to rap- idly renest following nest failure and the rel- atively large nearest-neighbor distances be- tween active nests. Reproductive ejfort and success. — We used Mayfield’s (1961, 1975) method to determine daily and overall survival rates for the incu- bation (n = 633 egg-days [43 nests]), hatch (n = 90 eggs [45 nests]), and nestling (n = 715.5 nestling-days [41 nests]) stages for nests in the upper Mohihi study area that were not protected against rats. When nests fledged or failed between visits, fate was assigned to the midpoint between observations. We present 3- year daily survival rates for the incubation and nestling periods as mean ± SE. Because we were uncertain of hatching period length, we treated hatching as either successful or unsuc- cessful and report hatching survival simply as percent eggs hatched. We calculated egg-to- fledging survival as the product of survival probabilities (incubation, hatch, and nestling). We documented the season-long reproduc- tive success for 48 territories over the 3 years of our study. A few individuals (n = 6 birds at 12 territories) were color marked, and we could occasionally identify individuals (// = 13 birds at 1 1 territories) through the presence of unique residual scalloping on the breast feathers in second-year (SY) birds. No color- banded individuals were observed actively breeding until 1997. We report measures of reproductive success per territory (rather than per female). To count the number of young fledged, we visited all nests within 3 days of the fledge date and again <1 week later. Accurate counts were possible because ( I ) parents fed new fledg- lings often, (2) new fledglings were poor fli- ers, (3) they remained perched in low shrubs <50 m from the nest during the first few days after fledging, and (4) they typically stayed within 100 m ol' the nest during the next feu weeks. We used the maximum count of ob- served young lledgetl to calculate fecundity statistics. We report annual means and 3-year means ± .SI) for llctlglings/tcrritory. young lledgcd/successful nest, nesting attempts/ter- ritory. afitl llcdglings/attcmpt. We compared lletlging dates of one- and two-chick nests us- ing ANOVA, aiul ue com|-)arcd the time from nest completion (for successful versus failed 76 the WILSON BULLETIN • Vol. 1 17, No. I. March 2005 14 Month nestl^ound Tu 5 d-e. We bacic-da.ed fo rr;a™ -- -eTo e-d nests) until the onset of renesting with a r-test (Statistix for Windows 2.0, a = 0.05). Survival~As time allowed, we trapped, banded, and color marked Puaiohi using mist nets set up in the vicinity of active nests or along ridgetops where Puaiohi were regularly observed. Sample sizes were too small to use capture-recapture modeling to estimate sur- vival, and we report minimum annual survival based on resightings for two age categories (HY, AHY) from one breeding year to the next, using April as the start of the breeding season. RESULTS The Puaiohi breeding season began in March-April and usually ended in August, al- though in one year it continued into Septem- ber. We found no active nests after August, but a recently fledged juvenile was observed m late September, indicating nesting can con- tinue into that month. Breeding season lengths were 87 days (1996), 132 days (1997), and 51 days (1998). The complete nesting cycle took 46 days- nest construction lasted 2.9 ± 2.0 days (range days, n = 15), the latency period was 9 ± 0.6 days (range = 8-10 days, n = 12) incubation lasted 13.5 ± 0.6 days (range = 13-14 days, n = 4), and the nestling period was 18.3 ± 1.7 days (range = 16-22 days, n 13). Eggs were laid one/day. Incubation be- gan with clutch completion and hatching was synchronous (<24 hr) within broods. Territory occupation and nest density. We found 1 12 nests, 96 of which were active (Fig. 2). The active nests were distributed over the 3 years as follows: 1996 — 29 nests (repre- sendng a complete reproductive effort in 12 territories plus a partial effort in 8 territories); 1 997 — 47 nests (representing complete repro- ductive effort in 14 territories plus partial ef- fort in 10 territories); 1998—20 nests (repre- senting complete reproductive effort in 22 ter- ritories plus partial effort in 4 territories). The remaining nests either were not used or were found after use and were distributed over the period of the study as follows: 4 nests (1996), 10 nests (1997), 2 nests (1998). In addition, we found 97 Puaiohi nests that had been con- structed and possibly used in a year prior to their discovery. Puaiohi pairs were distributed at approxi- mately 150-m intervals along 3.8 km of the Mohihi Stream. Mean straight-line distance between active nests was 86 ± 17 m (range = 59-119 m) in 1996, 79 ± 14 m (range - 58-103 m) in 1997, and 133 ± 40 m (range = 98-204 m) in 1998. Twenty-four territories were occupied by territorial pairs within the accessible portion of our study area through- out the study. The density of territorial Pu- Snetsinger et al. • PUAIOHI BREEDING ECOLOGY 77 TABLE 1. Puaiohi nest and nest-site characteristics, Mohihi drainage, Alakai Swamp, Kauai, 1996-1998. n Mean SD Maximum Minimum Height of wall (m) 157 9.5 4.8 35 3 Height above ground (m) 172 4.2 2.6 16 0.6 Distance from stream (m) 151 7.6 9.7 40 0 Width of nest cavity (cm) 46 39.4 23.4 90 7 Height of nest cavity (cm) 46 26.9 13.2 70 10 Depth of nest cavity (cm) 38 21.4 10.8 50 0 Nest concealment (%) 153 69 31.2 100 0 Outer diameter of nest (cm) 33 14.3 2.7 21 10 Inner diameter of nest (cm) 27 8.0 1.3 10 6 Height of nest (cm) 31 8.1 3.5 14 2 Nest-cup depth (cm) 27 5.4 1.5 8.7 3 Nest-rim thickness (cm) 29 3.2 0.7 4.5 2 Direction of exposure (°) 144 161 106 338 0 aiohi in the Mohihi study area was 6.3 pairs/ km of primary stream bottom. The additional length of feeder streams that were too short to support more than a single territory were not included in the calculation of primary stream bottom. Non-territorial, single birds were also observed throughout the study area; however, because many of these birds were unbanded and could not be sexed accurately, we could not determine the size or structure of this pop- ulation. Individual birds within a territory were occasionally replaced, but only one new territory was established in 3 years. When uniquely plumaged (n = 13) or color-banded (n = 6) individuals held territories, we ob- served only one case of turnover of a bird within a breeding season. All banded birds (two adult males and one adult female) that we monitored on breeding territories in 1997 returned to defend the same territory in the 1998 breeding season. At least 10.0% of territories had SY females and >6.7% had SY males (/? = 60 pair-years). At 8.0% of 87 nests, we noted some form of helper activity in which non-breeding Puaiohi helped in the defense and maintenance of nests and/or feeding of young. These birds were fledglings from previous clutches of the same pair (/; = 2) or SY non-breeding birds with an unknown relationship to the breeding adults (// = 5); in one case, the SY helper was known not to be related to either breeding adult. /Vc'.s'f sites, nests, and eggs. — Most nests were constructed in cavities or on shelves of I streamside cliff faces. Only 3% of active nests (n = 93) were in other locations: four were in secondary cavities in dead ohia snags, and one was in a crevice along the side of fallen log that bridged a small stream. One inactive nest was found in the trunk of a hapuu (Cibotinm sp.) tree fern. Nest sites ranged from true cavities, in which the nest was completely concealed and accessed through a small hole in the cliff wall, to exposed flat shelves with little protective cover (Table 1). The majority of nests were positioned on flat shelves partially concealed from above by a protective “umbrella” of ferns and a slight overhang of the cliff nest wall. While two nest walls were dry and cov- ered with only a light growth of lichen, 97% (n = 77) were damp and covered with a ver- dant growth of small, native plants: native ferns (predominantly Sadleria sc/narrosa), liv- erworts, and scattered small shrubs and trees (e.g., olapa and lapalapa, Cheirodendron spp.; Cyanea hirtelUr, kanawao, Bronssaisia argu- ta\ pukiawe, Styplielia tanieiameiae: and ohe- lo, Vaccininm spp.). Nests in = 110) were open-cupped with an outer matrix composed of mounded native mosses, uluhe (false staghorn fern, Dicran- opteris linearis), liverworts, other bryophytes, painiu (a native lily, Astelia spp.) and sedge iCare.x spp.) leaves, clubmosses {Lyeopodiinn spp.), other ferns, grasses, and ohia rootlets, fhe cup lining was woven of pulu (a soft hair- like substance from hapuu), moss sporo- phytes, shredtied grasses and sedges, or painiu leaves. Usually, an untitly mass of nesting ma- terial formed a tail, up to 20 cm long, extend- 78 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 LIG. 3. Lemale Puaiohi nest attendance and nest-visit duration. Numbers of nests monitored are shown above bars. Error bars are ± SE. ing out of the cavity mouth or off the shelf ledge from the base of the nest. All clutches consisted of 2 eggs {n = 39). Eggs had a smooth surface and their shape varied from sub-elliptical to ovoid. Eggs {n = 29) measured 24.77 ± 1.70 mm (range = 22.11-29.80 mm) X 18.18 ± 1.23 mm (range = 15.75-21.16 mm), and eggshell thickness = 3) was 0.14 ± 0.02 mm (range = 0.12- 0.16 mm). Background color of eggs varied, some- times within a clutch, from a very pale green- ish-blue at the light end of the spectrum to brownish-mauve at the dark end. All eggs had irregular rust, brown, mauve, and tan splotch- es and black and brown scrawls scattered over the surface, but concentrated at the blunt end. Nesting through fledgling observations.— During incubation, the male was responsible for territory defense; after hatching, he fed the female and young. Incubation and brooding were performed solely by the female, but both adults shared provisioning and maintenance duties (females responsible for 56% of the nest visits, males 9%, and undetermined par- ent or helper 35%; n — 848 nest visits in 461 hr of observation at 42 nests). During the nest- ling period, female visitation rates were 2.8 ± 0.2 visits/hr. Males made 0.68 ± 0.08 visits/ hr during the same period. Overall nest attendance was fairly high dur- ing incubation and then gradually dropped off as brooding proceeded (Fig. 3). Female nest attendance was 81 ± 4% SE (n = 5) a day after clutch completion and averaged 77% {n = 73) during the incubation period. One day after hatch female attendance dropped to 56 ± 7% SE {n = 9). Over the entire nesting period, the relative frequencies of provisioning nestlings with in- vertebrates and fruit were nearly equal; how- ever, young were fed invertebrate prey exclu- sively until 6 days of age, when fruit was first incorporated into the nestling diet. Nestlings received fruit during 48% of the feedings in which the food item was observed {n = 79). In order of decreasing frequency, these fruits were olapa/lapalapa, painiu, kanawao, ohelo, and “thimbleberry” (West Indian raspberry, Rubus rosifolius). Invertebrates were fed to nestlings 51% of the time. In order of decreas- ing frequency, these were moths, damselflies, earthworms, caterpillars, dragonflies, spiders, beetle larvae, and beetles. On one occasion we observed a nestling being fed a skink. Young in one-chick nests in — 4 nests) had Snetsinger et al. • PUAIOHI BREEDING ECOLOGY 79 50.0 45.0 40.0 35.0 § 30.0 c« if) CO ^ 25.0 O) 2 20.0 15.0 10.0 5.0 0.0 FIG. 4. Puaiohi nestling growth curves (mean mass, standard error bars). Number of nestlings weighed are shown above (1 -nestling nests, n = 4) or below (2-nestling nests, n = 16) each point. Young in 1 -nestling nests fledged at days 16-19, and, in 2-nestling nests, they fledged at days 16-21. 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 Nestling age (days) mean weights that were greater than those of young in two-chick nests (/? = 16 nests) through early development, but once the chick’s growth in one-chick nests began to plateau around nestling day 12, there was little difference in weights (Fig. 4). The nestling pe- riod of two-chick (16.3 days) and one-chick (16.6 days) nests did not differ (one-way ANOVA; T, 33 = 0.36, P - 0.55). After fledging, males were responsible for 81% of the feedings, females accounted for 8%, and an unidentified parent or helper ac- counted for 11% (n = 62 feedings at 10 nests). Fledglings remained dependent on par- ents for 3-5 weeks after fledging (// = 73 nests). During this period no young were ob- served >100 m from the nest site. Reproductive effort and success. — Nesting effort and productivity differed among years (Table 2). In 1996 (// = 12 territories) and 1997 (// = 14 territories), median nesting ef- fort was three nests per territory. In 1998, a relatively poor year, the nesting season was restricted to 4 months (// = 22 territories) with a single nesting attempt being the median ef- fort among closely monitored territories, fhe interval between nesting attempts was 10.2 ± 4.0 days (range = 5-18 days, n = \2 nest- renest periods with exact dates known) fol- lowing nesting success or failure. The out- come of the first nest did not affect the time interval between nest attempts (r,,, = —0.12; P = 0.91). The most prolific pair fledged sev- en young from four (of five total) nesting at- tempts. Daily probability of survival (3 year mean ± wSE) during the incubation period was 0.949 ± 0.032 (n = 633 egg-days |43 nests]) and during the nestling period was 0.980 ± 0.012 (// = 715.5 nestling-days |41 nests]). The probability of a fully incubated egg hatching was 0.864 ± 0.052 (// = 90 eggs 1 45 nests])’. Hgg and nestling survival both showetl similar dramatic decreases in the 1998 field season, while the probability that an egg incubated to term would hatch remained near the overall average (Fig. 5). fhe probability of survi\al for the egg-to-lletlging iicriotl was 0.406 ± 0.176 (3-year mean ± SfO. Of 21 nest failures, we attributed 48^>^ to predation {\'^P7< rats ]probably black rats. Rat- tus rattus], \(Y/< owls ]we suspect the .Short- 80 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 TABLE 2. Distribution of number of young Puaiohi fledged per territory, by breeding season (all nesting attempts known), and summary of fecundity statistics, upper Mohihi study area, Kauai, 1996-1998. Number of young fledged 1996 1997 1998 Mean ± SD (1996-1998) 0 1 0 14 — 1 0 0 7 — 2 2 1 1 — 3 7 0 0 — 4 2 5 0 — 5 0 2 0 — 6 0 5 0 — 7 0 1 0 — Total territories 12 14 22 16 ± 5.3 Mean fledglings/territory 2.8 4.9 0.4 2.3 ± 2.2 Young fledged/successful nest (no. nests) 1.7 (20) 1.9 (37) 1.0 (9) 1.6 ± 0.4 Nesting attempts/territory (no. attempts) 2.2 (26) 3.3 (44) 1.1 (24) 2.4 ± 1.4 Fledglings/attempt 1.4 1.7 0.4 1.1 ± 0.7 eared Owl, Asia fiammeus, based on our ob- 4 failed nests at territories in which no sub- servation of this species near these nests], and 19% unknown), 14% to abandonment, 5% to weather, 5% to disturbance by non-nesting Pu- aiohi, 5% to hatch failure, and 24% to un- known causes. Puaiohi reused historically suc- cessful nest sites. We never observed reuse of a nest site that failed to produce young {n = sequent nesting attempt was made). We doc- umented reuse (1-3 times) of 18 historically successful nests in 1 1 different territories. Dispersal, fidelity, and philopatry. — Five of the 31 nestlings (16%) that we banded in 1997 exhibited territorial behavior within our study area the following year, establishing an area LIG. 5. Egg and nestling survival of Puaiohi for incubation, hatch, nestling, and egg-to-fledging stages by year and all years combined for nests without rat protection {n = 633 egg-days [43 nests], n = 90 eggs [45 nests], n = 715.5 nestling-days [41 nests]). Nesting stage survival values were calculated using Mayfield daily survival rates for the incubation (13.5 days) and nestling stages (18.3 days); hatching survival is simply percent eggs hatched. Egg-to-fledging survival is the product of egg, hatch, and nestling survivals. Error bars are ± SE. Snetsinger et al. • PUAIOHI BREEDING ECOLOGY 81 of activity that was occupied for at least 8 weeks. Distance to natal nest from the activity center was 279 ± 157 m (range = 137-538 m, n = 5). One male succeeded in nesting 300 m from its natal site. Two others were ob- served within 50 m of their natal sites on at least one occasion, and two additional SY birds were documented as floaters >300 m from their natal sites. Survival. — At least 25% of HY birds sur- vived until April of the year following their banding (7 of 34 unknown sex and 2 of 2 males), and 73% of AHY Puaiohi survived until the following April (2 of 5 unknown sex, 2 of 2 females, and 4 of 4 males). Predators and predator control ejforts. — We protected 27 nests during 576 nest-days with rat bait stations. We monitored an addi- tional 54 untreated nests over 1,038 nest-days. Nest fate and nest protection with rat poison were not independent (x^ =11 .62, df = 4, P = 0.020). At protected nests, rat predation was 0%, owl or unknown predation was 3.7%, non-predation failure was 0%, unknown fail- ure was 0%, and 96.3% fledged >1 young. At unprotected nests, rat predation was 7.4%, owl or unknown predation was 13.0%, non-pre- dation failure was 16.7%, unknown failure was 1.9%, and 61.1% fledged >1 young. Nest failures confirmed to have been caused by rat predation increased from 0% in 1996 and 1997 to 36% {n — 11 failures) in 1998, when eggs, nestlings, and an incubating female Pu- aiohi were depredated by rats. However, 8% of nests in 1996 and 3% of nests in 1997 failed due to unknown causes, at least a por- tion of which may have been caused by rat predation. There was no evidence of rat pre- dation at any of the nests with rat bait stations. DISCUSSION The Puaiohi is a species on the brink of extinction, but it is not too late for construc- tive, alTordable managefnent action. It is not so rare that researchers ponder whether or not it is extinct or debate the pros and cons ol removing the populatiofi from the wild. How- ever, the situation is dire enough to cause alarm and draw the attention of managers and researchers, fhe Puaiohi population numbers in the hundreds, not in the thousands, and even over the few stjuare kilometers where we found its population to be the most dense, the Puaiohi was uncommon or rare. Predation by rats is the one clear threat that our research documented, but others loom in the back- ground. Habitat modification through the es- tablishment of invasive plant species and in- creasing exposure to avian disease both rank as serious future threats. Through our limited surveys in three study areas, we found the Puaiohi was rare or absent over large areas of apparently suitable habitat. Expansion of the Puaiohi ’s current range to include all available habitat and efforts to in- crease the Puaiohi ’s density in sparsely occu- pied areas should rank high among efforts to manage this species’ recovery. Long-term ef- forts to slow the establishment of invasive weeds in the Alakai and to develop techniques to eradicate or reduce rat populations there are both important to the survival of the Puaiohi. Cultivating the political will to put these steps into action is just as crucial, and without this support no rat control will ever occur in the wild, where it is needed. If all of these efforts can be implemented, they will undoubtedly have ancillary benefits in promoting the sur- vival of other endemic species. While researchers have focused much atten- tion on the role of humans in the extinction or near extinction of much of Hawaii’s avi- fauna, Kauai offers a striking example of the effect of natural events on vulnerable avian populations. Hurricanes Dot (1959), Iwa (1982), and Iniki (1992) each caused serious damage on Kauai and likely negatively af- fected avian populations. Notably, following Hurricane Iwa, observers documented only a few sightings of four of Kauai’s live rarest species: Kamao {Myadestes myadestinus), Kauai Oo (Molio hraccatns), Ou {Psiftirostra psittacea), Nukupuu {Heniignatluis lucidus), and Puaiohi. None except Puaiohi has been seen since Iniki. The Puaiohi was apparently rarer than the Kamao or Ou from its discovery through the 1970s, but totlay it survives in numbers that appear to rival those of the past; the other spe- cies may be extinct (Perkins 1903, Richardson and Powics 1964, Panko 1980. Sincock et al. 1984, Scott et al. 1986, C\)iiant et al. 1998. Snetsinger et al. 1999, Reynolds and Snetsin- ger 2001). While life history information on Kauai's other endangered endemics is \ery limited (Snetsinger et al. 1998, Wakelee and 82 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 Fancy 1999, Sykes et al. 2000, Pratt et al. 2001), our data indicate that Puaiohi can be prolific breeders in comparison with Omao (Wakelee and Fancy 1999) and other Flawai- ian endemics. Their high fecundity may have been one key difference between the Puaiohi and Kauai’s other endangered forest birds and may help to explain their survival. Population structure and distribution. — Our surveys of the upper Mohihi study area indi- cated that there was a steady-state breeding population for the entire period of August 1995-August 1998. In 1998, a poor breeding year overall, we noted the establishment of one new territory. In all years we noted the presence of non-breeding floaters, which acted as helpers or made unsuccessful attempts to establish territories. This indicated that the population within the study area was saturated by the end of the 1995 breeding season. Kauai was hit by Hurricane Iniki in September 1992, and USFWS/DLNR surveys in early 1993 showed no indication of Puaiohi breeding and documented only a single individual. This suggests that, at best, 1993 was a poor breed- ing year. Therefore, Puaiohi either survived in good numbers through Hurricane Iniki, or within two breeding seasons (1994 and 1995) the species recovered enough to saturate the upper Mohihi study area with a full comple- ment of breeding pairs and a detectable floater population. While our data set was small, our resight- ings of color-banded birds suggest young Pu- aiohi exhibit relatively strong philopatry and protracted juvenile dispersal. It is likely that these factors contribute to the establishment of a buffer population of non-breeders and help- ers. As first documented by Ashman et al. (1984), we observed no obvious aggression by parents toward older fledglings. In fact, some fledglings assisted in raising subsequent clutches within the same year and were ob- served near natal territories between years. Adults also showed strong nest-site fidelity within and between years. Strong philopatry and adult nest-site fidelity combined with pro- tracted juvenile dispersal support the theory that Puaiohi dispersal is a slow process. Among Hawaiian forest bird species, the existence of floater populations is suspected in Omao (Wakelee and Fancy 1999) and docu- mented in Elepaio (Chasiempsis sandwichen- sis; Vanderwerf 1998). Vanderwerf (1998) found larger and older floater populations in high-quality habitat than in marginal habitat or in populations with high morality rates. The Puaiohi populations in the upper and lower Mohihi appear to offer the same contrast, with a well-developed floater population in the up- per Mohihi and no detectable floater popula- tion in the lower Mohihi study area. While the upper Mohihi’s floater population may serve as a buffer to the breeding population, the sed- entary nature of these birds also prolongs the process of recovery and recolonization in ar- eas that hold few or no Puaiohi, such as the lower Mohihi. Expansion into these areas is likely to be incremental, as only breeding birds on the periphery of a high-density area would be major contributors to range expan- sion, when young from their nests disperse into unsaturated habitat. Translocation of captive-reared birds may be the most effective technique for rapidly ex- panding the range of this species since cap- tive-reared birds should not demonstrate strong site fidelity — a trait that has proved to be a challenge in some translocation efforts (Eancy et al. 1997). Preliminary translocation efforts have met with mixed success (Kuehler et al. 2000, 2001; Tweed et al. 2003). Limiting factors affecting breeding. — The Puaiohi’s specific nest-site requirements are probably the most important limiting factor within the upper Mohihi study area. This is also probably the case at the lower Mohihi area, but the extremely low Puaiohi density there suggests that other limiting factors may also play an important role. Most nests were constructed in cavities or on shelves in streamside cliff faces, as de- scribed by earlier researchers (Kepler and Ke- pler 1983, Ashman et al. 1984). Kepler and Kepler (1983) suggested that Puaiohi nest-site selection could make them less susceptible to weather effects. Our results support this con- clusion as we noted only one nesting failure that we attributed to weather, despite a number of severe storms during breeding seasons. Parents provided nestlings with equal pro- portions of invertebrate prey and mature fruit, suggesting a dependence on both. Lower rain- fall in the winter (rainy) season of 1997-1998 may have resulted in low food availability during the 1998 breeding season. Our anec- Snetsinger et al. • PUAIOHI BREEDING ECOLOGY 83 dotal observations suggest a scarcity of ma- ture fruit on the Puaiohi’s dominant food plants (particularly olapa; kanawao; and ohia ha, Syzygiutn sandwicense) during that period. Low food availability may have contributed to poorer condition of adults and a lack of food for nestlings in that year, either of which could have contributed to poor nesting effort. An apparent increase in rat predation con- tributed to low reproductive success in 1998. While there are many possible explanations for the increase in rat predation, one reason- able theory is that a general scarcity of fruit forced the rats to search more widely for food than usual, exploring cliff walls and opportu- nistically finding and depredating Puaiohi nests. The combination of increased predation and a poor nesting effort reduced the number of fledglings/territory by more than 80% from that observed during each of the preceding 2 years. Predator control. — Results of rat control ef- forts indicated that rats have a significant im- pact on Puaiohi nests and fledglings. Limited poisoning around active nests resulted in a higher proportion of nests that fledged young. Our discovery in 1998 of the depredation of an incubating female and her two eggs by rats emphasized that rats can impact not only nest- ing productivity but also the adult breeding population. Predator control was labor intensive, as per- formed for this study, and would be cost pro- hibitive on a large scale. Given the protracted breeding season and difficult working envi- ronment, it would be exorbitantly expensive even on smaller area, such as the lower Mo- hihi study area. Large-scale rat control efforts such as those involving aerial distribution of rodenticide have the potential for substantial positive impacts (Veiteh and Bell 1990, Arm- strong and McT.ean 1995, Hmpson and Mis- kelly 1999), and these technit|ues are the only viable alternatives for rat control over large areas of Puaiohi habitat. However, in addition to cost and other management considerations (e.g., effects on non-target species, secondary poisoning, and potential water supply contam- ination), political, cultural, and social factors will need careful consideration before such methods can be attempted, even at experimen- tal levels. Conclusion. — fhe Puaiohi has proven itself a survivor. Its fecundity and adaptability to captive propagation make management tech- niques, such as the reintroduction of captive- bred birds, potentially powerful tools in ex- panding the current range of the Puaiohi and increasing population density in areas where their numbers are low. However, research into limiting factors in areas of low population density will be a crucial component in the de- velopment of a successful management strat- egy. Effective and politically acceptable, broad-scale rat control techniques will likely play an important role in future management efforts. ACKNOWLEDGMENTS J. Denny was a source of constant inspiration and anecdotal information, and we are indebted to him. T. Casey and M. Reynolds contributed to our research through their independent field efforts and willingness to share their observations. This research was made possible, in part, by financial and logistical support from USFWS, DOFAW, and ZSSD. We thank T. Teller, W. Souza, P. Conry, C. Terry, R. Smith, K. Rosa, A. Lieberman, C. Kuehler, M. Kuhn, and J. Kuhn for their assistance. We thank T Abe, S. Bartholf, S. Berla, B. Brosi, C. Foster, S. Kinghorn, J. Liebezeit, K. Lynch, M. Parks, S. Rao, C. Rideout, and J. Talbot for their hard work collecting field data. H. Love and L. Young provided much needed administrative assistance from afar. J. Jacobi helped maintain communication among the partners and offered helpful suggestions along the way. This manuscript was greatly improved through valuable comments by S. Conant, J. Nelson, H. D. Pratt, T. K. Pratt, C. van Riper, 111, E. VanderWerf. B. Woodworth, and an anonymous reviewer. Any use of trade, product, or firm names does not imply endorse- ment by the U.S. Government. LITERATURE CITED Ak.m.stronCi, D. P. and 1. G. McEe;an. 1995. New Zea- land translocations; theory and practice. Pacific Conservation Biology 2:39-54. Ashman, P. R.. P. Pyi.i:. and.!. .liaiRix. I9S4. A second nest of the Small Kaua'i riirush. ‘Elepaio 45:33- 34. Banko, W. Pi. 1980. History of endemic Hawaiian birds. Part 1. population histories — ^s|X’cies ac- counts: forest birds: Hawaiian thruslies. C'oopera- tive National Park Resources Studs Lnit. Lniscr- sity of I lawaii. 1 lonolulu. Coi I AR. N. .1.. M. .1. Cronus . \nd A. .1. S \ n i Rsi ii i n. 1994. Biuls to ssatch 2: the world list ol ihrcat- cnctl birils. Birillite International. Cambriilgc. Unite(.l Kingtiom. (’oNANi. S.. H. 1). Prsii, snd R. j. Sh si 1 I nui Rdl r. 1998. Rellections on a 1975 cspcilition to the lost ssorld ol the Alaka’i and other notes on the natural 84 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 history, systematics, and conservation of Kaua’i birds. Wilson Bulletin 1 10:1-22. Empson, R. a. and C. M. Miskelly. 1999. The risks, costs and benefits of using brodificoum to eradi- cate rats from Kaptiti Island, New Zealand. New Zealand Journal of Ecology 23:241-254. Fancy, S. G., J. T. Nelson, P. Harrity, J. Kuhn, M. Kuhn, C. Kuehler, and J. G. Giffin. 2001. Re- introduction and translocation of a Hawaiian sol- itaire: a comparison of methods. Studies in Avian Biology 22:347-353. Fancy, S. G., T. J. Snetsinger, and J. D. Jacobi. 1997. Translocation of the Palila, an endangered Hawai- ian honeycreeper. Pacific Conservation Biology 3: 39-46. Harrity, P, C. Kuehler, J. Kuhn, M. Kuhn, and A. Lieberman. 1995. Hawaiian endangered bird con- servation program: 1995 report to the U.S. Fish and Wildlife Service. The Peregrine Fund, Boise, Idaho. Kepler, C. B. and A. K. Kepler. 1983. A first record of the nest and chicks of the Small Kaua’i Thrush. Condor 85:497-499. Kuehler, C., A. Lieberman, P. Harrity, M. Kuhn, J. Kuhn, B. McIlraith, and J. Turner. 2001. Res- toration techniques for Hawaiian forest birds: col- lection of eggs, artificial incubation and hand-rear- ing of chicks, and release to the wild. Studies in Avian Biology 22:354-358. Kuehler, C., A. Lieberman, P. Oesterle, T. Powers, M. Kuhn, J. Kuhn, J. T. Nelson et al. 2000. De- velopment of restoration techniques for Hawaiian thrushes: collection of wild eggs, artificial incu- bation, hand-rearing, captive-breeding and reintro- duction to the wild. Zoo Biology 19:263-277. Mayfield, H. F. 1961. Nesting success calculated from exposure. Wilson Bulletin 73:255—261. Mayfield, H. F. 1975. Suggestions for calculating nest success. Wilson Bulletin 87:456-466. Perkins, R. C. L. 1903. Vertebrata [Aves]. Pages 368- 465 in Fauna Hawaiiensis (D. Sharp, Fd.), vol. 1, part IV. University Press, Cambridge, United Kingdom. Pratt, H. D. 1982. Relationships and speciation of the Hawaiian thrushes. Living Bird 19:73-90. Pratt, T. K., S. G. Fancy, and C. J. Ralph. 2001. Akiapolaau (Hemignathus rnunroi) and Nukupuu (Hemignathus lucidus). The Birds of North Amer- ica, no. 600. Pyle, R. L. 1994. Hawaiian Islands region. Field Notes 48:251-252. Reynolds, M. H. and T. J. Snetsinger. 2001. The Ha- waii rare bird search 1994-1996. Studies in Avian Biology 22:133-143. Richardson, F. and J. B. Bowles. 1964. A survey of the birds of Kauai, Hawaii. B. P. Bishop Museum Bulletin, no. 227. Honolulu, Hawaii. Scott, J. M., S. Mountainspring, F. L. Ramsey, and C. B. Kepler. 1986. Forest bird communities of the Hawaiian Islands: their dynamics, ecology, and conservation. Studies in Avian Biology 9:1- 431. SiNCOCK, J. L., R. F. Daehler, T. Telfer, and D. H. WooDSiDE. 1984. Kauai forest bird recovery plan. U.S. Fish and Wildlife Service, Portland, Oregon. Snetsinger, T. J., M. H. Reynolds, and C. M. Herr- mann. 1998. Ou {Psittirostra psittacea) and Lanai Hookbill {Dysmorodrepanis rnunroi). The Birds of North America, nos. 335-336. Snetsinger, T. J., K. M. Wakelee, and S. G. Fancy. 1999. Puaiohi (Myadestes palmeri). The Birds of North America, no. 461. Sykes, P. W., Jr., A. K. Kepler, C. B. Kepler, and J. M. Scott. 2000. Kauai Oo {Moho braccatus), Oahu Oo {Moho apicalis). Bishop’s Oo {Moho bishopi), Hawaii Oo {Moho nobilis), and Kioea {Chaetoptila angustipliima). The Birds of North America, no. 535. Tweed, F. J., J. T. Foster, B. L. Woodworth, P. Oes- terle, C. Kuehler, A. A. Lieberman, A. T. Pow- ers ET AL. 2003. Survival, dispersal, and home- range establishment of reintroduced captive-bred Puaiohi, Myadestes palmeri. Biological Conser- vation 3:1-9. Vanderwerf, F. a. 1998. Flepaio {Chasiempsis sand- wichensis). The Birds of North America, no. 344. Veitch, C. R. and B. D. Bell. 1990. Fradication of introduced mammals from the islands of New Zealand. Pages 137-146 in Fcological restoration of New Zealand islands (D. R. Towns, C. H. Daugherty, and I. F. Atkinson, Fds.). Conserva- tion Sciences Publication, no. 2. Department of Conservation, Wellington, New Zealand. Wakelee, K. M. and S. G. Fancy. 1999. Omao {Myadestes obscurus), Kamao {Myadestes my- adestinus), Olomao {Myadestes lanaiensis), and Amaui {Myadestes woahensis). The Birds of North America, no. 460. Wilson Bulletin 1 17(1):85— 91, 2005 EFFICACY OF USING RADIO TRANSMITTERS TO MONITOR LEAST TERN CHICKS JOANNA B. WHITTIER' ’-* AND DAVID M. LESLIE, JR.’ ABSTRACT. — Little is known about Least Tern {Sterna antillarum) chicks from the time they leave the nest until fledging because they are highly mobile and cryptically colored. We evaluated the efficacy of using radio- telemetry to monitor Interior Least Tern {S. a. athalassos) chicks at Salt Plains National Wildlife Refuge, Oklahoma. In 1999, we attached radio transmitters to 26 Least Tern chicks and tracked them for 2-17 days. No adults abandoned their chicks after transmitters were attached. Transmitters did not appear to alter growth rates of transmittered chicks {P = 0.36) or prevent feather growth, although dermal irritation was observed on one chick. However, without frequent reattachment, transmitters generally did not remain on chicks <1 week old for more than 2 days because of feather growth and transmitter removal, presumably by adult terns. Although the presence of transmitters did not adversely affect Least Tern chicks, future assessments should investigate nonintrusive methods to improve retention of transmitters on young chicks and reduce the number of times that chicks need to be handled. Received 27 May 2004, accepted 30 December 2004. Survival estimates for endangered Least Tern {Sterna antillarum) chicks — from hatch- ing until fledging — are obtained primarily through indirect measures, such as ratios of observed number of fledged birds to number of successful nests (Kirsch 1996, Woodrey and Szell 1998) or estimated number of breed- ing pairs (Schwalbach et al. 1993). Direct measurements of survival and determining the factors that impact survival have been hin- dered because Least Tern chicks are semi-pre- cocial, highly mobile, and cryptically colored. Furthermore, Least Terns nest colonially in open habitats, making undetected approach difficult. Approaches within 250 m result in alarm calls from adults, and, at that distance, chicks are difficult to see. Dugger et al. (2000) successfully used a mark-recapture technique to estimate survival of Interior Least Tern chicks {S. a. athalasso.s) nesting on islands. Because Least Tern chicks may move freely, mark-recapture techniques would be less use- ful in expansive nesting habitats (e.g., salt fiats) than in restricted habitats (e.g., islands). In either case, neither method can reveal fac- ' Oklahoma Coop. Pish and Wildlife Re.scaixh Unit, Dept, of Zoology, Oklahoma State IJniv., Stillwater, OK 74078, USA. ‘ U.S. Cleological Survey, Oklahoma C’oop. Pish and Wildlife Research Unit, Dept, of Zoology. Oklahoma State Llniv., Stillwater, OK 74078, USA. ’Current address; Kansas ('oop. l ish and Wikllife Research Unit, Div. of Biology, Kansas State Univ., Manhattan, KS 66506, USA. C'orresponding author; e-mail; whittierCoTsu.edu tors that affect survival of individual chicks. Accurate estimates of chick survivorship and cause-specific mortality are essential for de- termining management strategies to improve productivity of this endangered species (U.S. Fish and Wildlife Service 1990). With varying success, adult Least Terns have been marked with patagial tags and radio transmitters. Brubeck et al. (1981) detected high rates of nest desertion after attaching pa- tagial tags, but it was unclear whether the de- sertions were due to extended handling times or the tags. In two studies, adhesives were used to attach transmitters onto the backs of adult Least Terns (Massey et al. 1988, Hill and Talent 1990). In the 2-year study by Massey et al. (1988), terns marked in year one (/? = 4) were slow to return to their nests (>4 hr before return), and all terns marked in year two (/? = 3) exhibited various degrees of ab- normal incubation and abandonment. In con- trast, Hill and Talent (1990) found faster re- turn rates (<7() min) and .several transmiltered individuals resumed incubation immediately (some terns were trapped but not transmitter- ed). Nest desertion and nest and egg survival for radio-transmittered terns (// = 20 terns, n = 15 nests) did not differ from the control group (Hill and I'alent 1990). Advances in radio-telemetry ec]uipment have facilitated monitoring of small birtls (.Sykes et al. 1990, Yalden 1991). Previously, radio transmitters could be used only on mid- to large-si/ed animals because transmitter weights were excessive. C'urrently. one can 86 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 obtain transmitters that weigh <1.0 g and have a battery life of about 21 days. The life span of small transmitters limits their use for long-term monitoring of individuals, but Least Tern chicks fledge at about 20 days (Thomp- son et al. 1997); therefore, transmitter life is generally long enough to confirm survival to fledging. We evaluated the efficacy of radio-teleme- try to monitor Least Tern chicks from hatch- ing until fledging by assessing the impact of carrying radio transmitters. We also report on the technical details of this method. METHODS Study area. — Our study was conducted from 1 June to 15 August 1999 at Salt Plains National Wildlife Refuge (SPNWR), Alfalfa County, Oklahoma (98° 15' N, 36° 43' W). At this refuge. Least Terns nest on a salt flat of about 5,000 ha adjacent to Great Salt Plains Reservoir (Koenen et al. 1996). The nesting habitat is nearly level and has little vegetative cover, making detection distance of transmit- ter signals nearly optimal. We selected a study site at the south end of the Least Tern nesting habitat. Nest location. — We located nests by search- ing defended territories. To reduce distur- bance, we initially located nests from outside defended areas by observing adults returning to nests. If the number of potential pairs ex- ceeded the number of nests, we conducted a systematic search of the surrounding area to locate additional nests. We marked nests with a numbered dowel placed about 10 m away from the nest cup. Dowels were placed in ran- dom directions to discourage a learned re- sponse by predators. Nests were examined vi- sually from about 5 m away every 3-10 days until hatching. Nests that showed signs of dis- turbance (i.e., missing or broken eggs, etc.) were examined physically to determine cause of disturbance. Radio-marked chicks. — Chicks (ages 1-3 days) were placed into a mesh bag, weighed with a hanging spring scale, and then banded with U.S. Fish and Wildlife Service aluminum leg bands. Radio transmitters were placed on the largest chick in each nest at about 2-3 days of age; we also fitted transmitters on three chicks found away from their nests. As a precautionary measure, we hooded captured chicks to reduce stress (Hill and Talent 1990). Except for the type of glue used, we followed the transmitter attachment technique used by Hill and Talent (1990). Because cyanoacrylate glues have been linked with skin irritation and impaired skin functioning (i.e., blocked skin pores; Johnson et al. 1991), we used latex- based surgical glue (Skin Bond, Smith and Nephew, London, United Kingdom). We at- tached transmitters by first clipping down feathers of the interscapular region to expose the skin; then, surgical glue was brushed onto both the bare skin of the chick and the base of the transmitter. After the transmitter was in position, it was held in place for 1 min to seal the bond. When possible, surrounding feathers were glued over the top of the transmitter for camouflage and to reduce the likelihood of the transmitter being removed. Glue-on tech- niques have advantages over harnesses be- cause attachment is easier (Sykes et al. 1990) and harnesses have been found to alter behav- ior and survival in some birds (Kenward 1987, Hubbard et al. 1998). Using a mild sol- vent, we removed transmitters from chicks by 1 7 days of age to avoid hampering chicks dur- ing fledging. We attached 16 L.L. Electronics transmit- ters (model SMT-1-379-RS-T; Mahomet, Illi- nois) and 10 Holohil Systems Ltd. transmitters (model LB-2; Woodlawn, Ontario, Canada) to 26 chicks. Estimated life span of the trans- mitters was 2-3 weeks. L.L. Electronics trans- mitters averaged 0.8 g and measured 0.9 X 0.6 X 0.4 cm. Holohil transmitters averaged 0.6 g and measured 1.1 X 0.6 X 0.2 cm. Transmitter weight at the time of attachment was 5-8% of a chick’s weight (greater than the 3% benchmark recommended by the North American Bird Banding Laboratory but less than the 10% maximum recommended by Gaunt et al. 1997), but by 6 days of age, trans- mitter weight was ^3% of chick weight. All monitoring and handling protocols were ap- proved under U.S. Fish and Wildlife Service Endangered Species Permit TE820283-1. Radio-tracking. — The first three chicks fit- ted with transmitters were located once every 24 hr. When a transmitter was found to be loose, it was reattached. Because transmitters frequently became loose or detached, we lo- cated, captured, and physically examined the remainder of the chicks every 12 hr. Whittier and Leslie • USE OF RADIO TRANSMITTERS ON TERN CHICKS 87 Chicks were tracked during morning and evening hours, when temperatures were <35° C. We never tracked chicks during rainstorms. Once a week, we recaptured and weighed all chicks. When transmitters were removed, skin and feather condition were examined for dam- age. We calculated a growth curve for transmit- tered chicks by weighing them weekly. Few chicks without transmitters could be found again at SPNWR; thus, growth rates of trans- mittered chicks could not be compared with those of untransmittered chicks from the same location. Because we were unable to locate published data on daily growth rates of Inte- rior Least Tern chicks, we used growth data from California Least Tern {S. a. browni) chicks that also were captured and handled daily (Massey 1974) to estimate the impact of transmitters on growth of SPNWR chicks. We compared the straight-line segment between day 4 and 16 of each growth curve and inter- cepts using ANCOVA with chick age as the covariate (SAS Institute, Inc. 1996). RESULTS We attached radio transmitters to 26 Least Tern chicks. Because of flooding and preda- tion on the alkaline flat, loss of tern nests was common (e.g., Winton and Leslie 2003). Of 17 nests located in June 1999, 10 were lost before hatching and only three chicks were marked from 22 to 28 June. After adults re- nested, 23 additional chicks were marked from 24 July to 7 August 1999. Processing time per chick averaged 16 min ± 1.0 SE. No chicks were deserted or left unattended by adults after transmitters were attached. All chicks appeared to move normally after the transmitter was attached (Whittier 2001). Our initial intent was to relind chicks once a day to evaluate their condition and trans- mitter attachment, but, of the three chicks marked in June, only one was found again and its transmitter had to be reattached twice be- fore it was 5 days old (Table I ). fhe other two June chicks presumably lost their trans- mitters and could not be found again, fhere- t'ore, we changed our protocol to relocate chicks twice a day; transmitters were reat- tached whenever a light tug on the transmitter antenna revealed a partially detached trans- mitter. hour of 26 chicks were not fouiul again or died after 1 day and 4 (15%) retained their transmitters without reattachment for 3 {n = 2), 7, and 8 days (Table 1). Transmitters re- quiring reattachment were prevalent in the young age classes; 18 of 26 chicks (69%) <4 days of age were found with partially de- tached transmitters (Table 1). Transmitters on these 18 chicks had to be reattached, but the number of necessary reattachments decreased as the number of monitoring days increased (Fig. 1). Growth of chicks at SPNWR was sigmoidal (r° = 0.95; Fig. 2) and averaged 2.2 g/day. Based on growth curves, predicted fledging weight of chicks at SPNWR was 40 g (assum- ing fledging at 20 days; Thompson et al. 1997); chicks in California weighed 40.5 g at fledging (Massey 1974). A comparison of growth rates of transmittered chicks (/? = 20) at SPNWR with untransmittered chicks {n = 152) in California (Massey 1974) demonstrat- ed that chick weight at 4 days of age (our study: 11.25 g ± 1.76 SE; California: 13.81 g ± 0.28 SE; ANCOVA, F, .4 = 4.64, P = 0.043) differed, but mean growth rate did not differ (our study: 2.3 g/day; California: 2.4 g/ day; F, 24 = 0.17, P = 0.69; Fig. 2). Massey (1974) noted that weight gam and absolute weight of California tern chicks stabilized at about day 15 and varied between 35 and 40 g; chicks of the same age at SPNWR weighed between 36 and 39 g. We examined physical condition and feath- er growth when we removed transmitters from chicks that died (/? = 6) or were near fledging {n = 1). Those individuals carried a transmit- ter for a mean of 9 days. Tv/o chicks fledged before we removed the transmitters and the remainder disappeared (Table 1). Only one chick exhibited any sign of skin irritation, the skin was light pink, indicating only mild ir- ritation. and that chick successfully fledged. Two of the dead chicks did not exhibit any obvious signs indicating cause of death. J'he other four deaths were attributed to predation, flooding, or unusual exposure (one iiuli\ idiial was unable to escape from a 3eep hoofprint). I eather growth was not impaired on any of the chicks, and feathers were not \ isibly dam- agetl. l eather growth under the transmitter shiftetl the transmitter to a lov\er position on the back. 88 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 TABLE 1. Patterns of radio-transmitter retention for 26 Least Tern chicks in northcentral Oklahoma, June- August 1999. We often found chicks with partially detached transmitters that had to be reattached, but the frequency of occurrence decreased with chick age. Age of chick (days) No. of reattachments by age group in days Total no. of reattachments Chick fate Chick no. Transmitter attachment Transmitter removal No. of days monitored 2-4 5-8 9-12 13-17 June captures: monitored once/day 1 2 NA^ 1 0 Unknown 2 2 NA 4 2 0 2 Unknown 3 1 NA 1 0 Unknown July-August captures: monitored twice/day 4 2 NA 8 2 0 0 2 Unknown 5 1 NA 12 2 0 0 2 Unknown 6 2 5 3 0 0 Dead 7 2 NA 3 3 3 Unknown 8 2 NA 3 2 2 Unknown 9 4 NA 15 1 1 2 1 5 Pledged 10 2 10 8 2 1 0 3 Dead 1 1 1 2 1 0 Dead 12 1 NA 4 3 3 Unknown 13 2 17 15 2 1 2 0 5 Pledged 14 1 17 16 3 1 2 0 6 Unknown 15 2 5 3 1 1 Dead 16 2 13 11 2 1 0 3 Dead 17 3 16 13 1 1 1 0 3 Unknown 18 2 NA 3 2 2 Unknown 19 2 NA 1 0 Unknown 20 2 NA 8 2 1 0 3 Unknown 21 Unkf NA 8 0 Fledged 22 Unk Unk 3 0 Dead 23 2 NA 9 1 1 1 3 Unknown 24 Unk NA 7 0 Unknown 25 2 15 13 3 0 1 0 4 Unknown 26 2 14 12 1 1 1 0 3 Unknown ^ Not applicable; not all transmitters were removed from chicks; several individuals disappeared and two flew away with the transmitter still attached. ^ Chick age was unknown when transmitter was attached. DISCUSSION Radio telemetry is a reliable technique for ascertaining life-history traits of precocial and semi-precocial chicks. Various transmitter- at- tachment methods have been investigated for birds, including subcutaneous implants, suture and prongs, sutures, harnessed backpacks, and adhesives (Samuel and Fuller 1994, Korsch- gen et al. 1996, Hubbard et al. 1998, Davis et al. 1999, Burkepile et al. 2002). We do not recommend implants or either suture tech- nique for endangered Least Tern chicks be- cause those methods are invasive and some have led to infections (Burkepile et al. 2002). Based on apparent efforts of Least Tern adults or chicks in our study to physically remove transmitters, suture methods could result in in- creased stress and physical trauma to chicks. Hubbard et al. (1998) recommended not using harnessed backpacks on chicks because re- duced blood circulation to the wings can lead to impaired wing development that potentially could prevent flight. Adhesive methods have the advantage of (1) short handling time, (2) imposing minimal physical impairment to an individual’s movement, (3) requiring no med- ical procedures, (4) being noninvasive, (5) minimizing the chance of infection, and (6) not causing growth impairment. Ideally, the impact of carrying transmitters should be assessed using a reference group within the same study area (White and Garrott 1990). However, chicks at SPNWR are diffi- cult to refind on the expansive salt flats. Dur- Whittier and Leslie • USE OF RADIO TRANSMITTERS ON TERN CHICKS 89 1.0 n • = 0.64 0.0 ^ ^ ^ ^ ^ , 2 4 6 8 10 12 14 16 Number of days monitored FIG. 1. Relationship between the number of days monitored and the number of reattachments necessary per day for 18 of 26 Least Tern chicks in northcentral Oklahoma, June-August 1999 (transmitters on the remaining 8 chicks were not reattached; 4 of these chicks disappeared after 1 day of monitoring). 45 n 40 35 - 30 - g> 25 QJ 20 - 15 - 10 • SPNWR O California r 1 • I? “I 1 1 1 1 — 6 8 10 12 14 Age of chicks (days) 16 18 MG. 2. Growth curves (mean weiglit * SE) of ratlio-lransmittered Interior Least Icrn cliicks at Salt Plains National Wildlife Refuge, Oklahoma, and non-transmittereil California Least Tern chieks (Massey 1974). ,\t both sites, chicks were captured and handled at least otice a ilay. 90 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 ing our study, we were unable to locate band- ed, untransmittered chicks or siblings of trans- mittered individuals. Because no detailed data were found in published literature for growth rates of Interior Least Terns, we used growth data for chicks without transmitters in Cali- fornia (Massey 1974). Although comparing weights of geographically disjunct popula- tions is not ideal, we found that growth rates did not differ statistically between study groups. Frequent disturbance (up to two times per day to examine chicks and transmitters) did not prompt adult Least Terns to abandon their offspring or leave them unattended after we departed the immediate vicinity. The Kap- lan-Meier estimate of survival for the trans- mittered chicks was 26% (Whittier 2001), which falls within the range of survival-to- fledging estimates (19-69%) for Least Tern chicks in northwestern Oklahoma (Schweitzer and Leslie 2000). The majority of avian telemetry studies are conducted on adult or fledged birds, probably because of limitations related to transmitter weight. For this reason, little is known about the impact of the adhesive attachment tech- nique on feather growth. Although several studies of precocial chicks have entailed using adhesives as an attachment method, or using adhesives in conjunction with another method, no mention was made of feather growth (Yal- den 1991, Burkepile et al. 2002). Our results indicate that surgical glue did not disrupt feather growth in Least Tern chicks; after the glue was removed using a mild solvent, feath- ers were not visibly damaged. Dermal irrita- tion was observed on only one chick, and that individual had worn its transmitter for 17 days. The low level of dermal irritation ob- served in this study was consistent with the findings of Sykes et al. (1990), who examined use of adhesives to attach transmitters to small passerines. Transmitter loss was greatest when chicks were ^4 days of age, but it also occurred in older age classes — albeit with decreasing fre- quency. Feather growth caused transmitters to lift from the skin and shift posteriorly down the chicks’ backs. Despite transmitters shift- ing away from the center of gravity, transmit- tered chicks were able to run normally. The tendency for feather growth to move the trans- mitter likely contributed to the poor retention of transmitters. Increased retention of trans- mitters appeared to coincide with the devel- opment of pinfeathers. Transmitters were loos- ened anteriorly, evidently because either par- ents or chicks tugged on the antennae. Survivorship and the factors that impact survival are difficult to determine for preco- cial and semi-precocial chicks because they are difficult to refind. Advancements in trans- mitter technology have enabled production of smaller transmitters with weights that are rea- sonable for Least Tern chicks to carry. Those advancements provide the opportunity to more accurately assess chick survivorship and ex- amine variables that impact survivorship for small semi-precocial chicks. Latex surgical adhesive appears to be a safe method of trans- mitter attachment for Least Tern chicks be- cause it did not irritate the skin, impair feather growth, or damage feathers; however, future research should investigate methods to im- prove retention of transmitters. Chick growth and movement were not impaired by the pres- ence of a transmitter. ACKNOWLEDGMENTS Project funding was provided by Salt Plains Nation- al Wildlife Refuge, U.S. Geological Survey, and Oklahoma Cooperative Fish and Wildlite Research Unit (Oklahoma Department of Wildlife Conservation, Oklahoma State University, U.S. Geological Survey Biological Resources Division, and Wildlife Manage- ment Institute cooperating). Special thanks go to R. Krey for his ongoing support of graduate student re- search. We thank R. A. Van Den Bussche, C. Caffrey, C. L. Goad, and three anonymous reviewers for critical comments on earlier versions of this manuscript. LITERATURE CITED Brubeck, M. V., B. C. Thompson, and R. D. Slack. 1981. The effects of trapping, banding, and pata- gial tagging on parental behavior of Least Terns in Texas. Colonial Waterbirds 4:54-60. Burkepile, N. A., J. W. Connelly, D. W. Stanley, AND K. P. Reese. 2002. Attachment of radiotrans- mitters to one-day-old Sage Grouse chicks. Wild- life Society Bulletin 30:93-96. Davis, J. B., D. L. Miller, R. M. Kaminski, M. P. Vrtiska, and D. M. Richardson. 1999. Evalua- tion of a radio transmitter for Wood Duck duck- lings. Journal of Field Ornithology 70:107-1 13. Dugger, K. M., M. R. Ryan, and R. B. Renken. 2000. Least Tern chick survival on the lower Mississippi River. Journal of Field Ornithology 71:330-338. Gaunt, A. S., L. W. Oring, K. P. Able, D. W. Ander- son, L. F. Baptista, j. C. Barlow, and J. C. Whittier and Leslie • USE OF RADIO TRANSMITTERS ON TERN CHICKS 91 Wingfield. 1997. Guidelines to the use of wild birds in research. (A. S. Gaunt and L. W. Orning, Eds.). Ornithological Council, Washington, D.C. Hill, L. A. and L. G. Talent. 1990. Effects of cap- ture, handling, banding, and radio-marking on breeding Least Terns and Snowy Plovers. Journal of Field Ornithology 61:310-319. Hubbard, M. W, L. C. Tsao, E. E. Klaas, M. Kaiser, AND D. H. Jackson. 1998. Evaluation of trans- mitter attachment techniques on growth of Wild Turkey poults. Journal of Wildlife Management 62:1547-1578. Johnson, G. D., J. L. Pebworth, and H. O. Krueger. 1991. Retention of transmitters attached to pas- serines using a glue-on technique. Journal of Field Ornithology 62:486-491. Kenward, R. E. 1987. Wildlife radio tagging. Aca- demic Press, San Diego, California. Kirsch, E. M. 1996. Habitat selection and productivity of Least Terns on the Lower Platte River, Nebras- ka. Wildlife Monographs, no. 132. Koenen, M. T, R. B. Utych, and D. M. Leslie, Jr. 1996. Methods used to improve Least Tern and Snowy Plover nesting success on alkaline flats. Journal of Field Ornithology 67:281-291. Korschgen, C. E., K. P. Kenow, W. L. Green, D. H. Johnson, M. D. Samuel, and L. Sileo. 1996. Technique for implanting radio transmitters sub- cutaneously in day-old ducklings. Journal of Field Ornithology 67:392-397. Massey, B. W. 1974. Breeding biology of the Califor- nia Least Tern. Proceedings of the Linnaean So- ciety of New York 72:1-24. Massey, B. W., K. Keane, and C. Boardman. 1988. Adverse effects of radio transmitters on the be- havior of nesting Least Terns. Condor 90:945- 947. Samuel, M. D. and M. R. Fuller. 1994. Wildlife te- lemetry. Pages 370-416 in Research and manage- ment techniques for wildlife and habitats, 5th ed. (T. A. Bookhout, Ed.). The Wildlife Society, Be- thesda, Maryland. SAS Institutf:, Inc. 1996. Statistical analysis software, ver. 6.12. SAS Institute, Inc., Cary, North Caro- lina. SCHWALBACH, M. J., K. E Higgins, J. Dinan, B. J. Dirks, and C. D. Kruse. 1993. Effects of water levels on Interior Least Tern and Piping Plover nesting along the Missouri River in North Dakota. Pages 75-81 in Proceedings of the Missouri River and its tributaries: Piping Plover and Least Tern symposium. (K. E Higgins and M. R. Brachier, Eds.). South Dakota State University, Brookings. Schweitzer, S. H. and D. M. Leslie, Jr. 2000. Stage- specific survival rates of the endangered Least Tern {Sterna antillariim) in northwestern Oklahoma. Proceedings of the Oklahoma Acade- my of Science 80:53-60. Sykes, P. W, Jr., J. W. Carpenter, S. Holzman, and P. H. Geissler. 1990. Evaluation of three minia- ture radio transmitter attachment methods for small passerines. Wildlife Society Bulletin 18:41- 48. Thompson, B. C., J. A. Jackson, J. Burger, L. A. Hill, E. M. Kirsch, and J. L. Atwood. 1997. Least Tern {Sterna antillarwn). The Birds of North America, no. 290. U.S. Fish and Wildliee Service. 1990. Recovery plan for the interior population of the Least Tern {Ster- na antillariim). U.S. Fish and Wildlife Service, Twin Cities, Minnesota. White, G. C. and R. A. Garrott. 1990. Analysis of wildlife radio-tracking data. Academic Press, San Diego, California. Whittier, J. B. 2001. Management implications of population genetics and demographics of Least Terns {Sterna antillariim). Ph.D. dissertation. Oklahoma State University, Stillwater. WiNTON, B. R. AND D. M. Leslie, Jr. 2003. Nest sites and conservation of endangered Interior Least Terns Sterna antillariim athalassos on an alkaline flat in the south-central Great Plains (USA). Acta Ornithologica 38:135-141. WOODREY, M. S. AND C. C. SzELL. 1998. Reproductive success of the interior population of Least Terns {Sterna antillariim) nesting on the Mississippi River from Memphis, Tennessee to Rosedale. Mississippi: years 1995-1997. Mississippi De- partment of Wildlife, Fisheries & Parks, Museum Technical Report, no. 57. Yalden, D. W. 1991. Radio-tracking of Golden Plo\ er Pliivialis apricaria chicks. Wader .Stutly Group Bulletin 63:41-44. Wilson Bulletin 1 17( 1 ):92-99, 2005 USING CANOPY AND UNDERSTORY MIST NETS AND POINT COUNTS TO STUDY BIRD ASSEMBLAGES IN CHACO EORESTS ENRIQUE J. DERLINDATE 2 AND SANDRA M. CAZIANE ABSTRACT. — We sampled birds with mist nets and point counts in old-growth and second-growth Chaco forest in Argentina to compare the contribution of each method to estimates of species abundance and diversity. We captured 53 species with mist nets (13 exclusively), and detected 75 species on point counts (43 exclusively). Species richness estimated by rarefaction curves did not differ between methods, except in old-growth under- story, where point counts detected fewer species than mist nets. Both methods showed similar patterns of bird diversity and distribution, although point counts revealed more differences between forest layers and forest types. Mist netting contributed to the detection of cryptic or secretive species, especially in the understory, but large- bodied (>200 g) species were detected by point counts alone. Multivariate analysis discerned guilds and species associated with different forest layers and types. Point counts seem to better reflect relative abundance, whereas mist nets may be more sensitive to bird activity (e.g., movements between resources). The simultaneous use of both techniques enhances the description of bird communities, and birds’ use of habitats. Received 19 June 2003, accepted 7 November 2004. Mist nets and point counts have been wide- ly used in the study of Neotropical birds (Whitman et al. 1997, Rappole et al. 1998), and a combination of the two techniques might be the most effective methodological approach for monitoring bird assemblages (Wallace et al. 1996, Gram and Faaborg 1997, Rappole et al. 1998, Poulin et al. 2000, Blake and Loiselle 2001, Wang and Finch 2002). Al- though point counts have been used exten- sively (Blake 1992, Thompson et al. 1999, Verner and Purcell 1999, Codesido and Bilen- ca 2000, Mills et al. 2000), they depend on the researcher’s training in identification of species (Whitman et al. 1997, Blake and Lo- iselle 2001). Mist nets are relatively easy to use and they simplify species identification (Herrera 1978, Ralph et al. 1996); however, mist-net capture data represent species activity rather than abundance (Remsen and Good 1996), and use of mist nets is typically con- fined to the understory (Karr 1976, 1977, 1981; Schewske and Brokaw 1981; Blake and Rouges 1997; Gram and Faaborg 1997; Res- trepo and Gomez 1998; Gardali et al. 2000), thus excluding most canopy birds (Karr 1976, Caziani 1996, Remsen and Good 1996, Rap- pole et al. 1998, Blake and Loiselle 2001, Wang and Finch 2002). Few investigators ' Facultad de Ciencias Naturales y Consejo de In- vestigaciones, Univ. Nacional de Salta — CONICET, Buenos Aires 177, 4400 Salta, Argentina. ^ Corresponding author; e-mail: dvazquez@unsa.edu. ar have used mist nets systematically in more than one forest layer (Lovejoy 1974, Karr 1976), and none have analyzed the contribu- tion of simultaneous mist netting and point counts in the study of bird assemblages in dif- ferent forest layers. In this study, we compare the results ob- tained from mist nets and point counts as part of a larger study to compare the vertical dis- tribution of birds and their resources between two different forest habitats in the semi-arid Chaco. The vertical distribution of birds has mainly been studied using different techniques in multi-layered tropical rainforests with high tree canopies (Anderson and Shugart 1974, Lovejoy 1974, Karr 1976, Loiselle 1987, Ter- borgh et al. 1990, Blake and Loiselle 2001, Winkler and Preleuthner 2001). The subtrop- ical, semi-arid Chaco forest, with its low tree canopy and relatively simple vertical struc- ture, provides an ideal system for testing the use of canopy and understory mist nets and point counts to study bird assemblages. Our objectives in this study were to (1) evaluate the use of canopy mist nets in a semi-arid for- est with a low tree canopy, (2) compare esti- mates of species richness and abundance based on point counts and mist nets, and (3) compare the ability of point counts and mist nets to detect differences in bird assemblages between canopy and understory, and between two forest types (old-growth forest and sec- ond-growth forest). 92 Derlindati and Caziani • MIST NETS AND POINT COUNTS IN CHACO FOREST 93 METHODS Study area. — Copo National Park (1 14,000 ha, 160 m elevation) is located in Santiago del Estero Province, Argentina (25° 55' S, 62° 05' W). The area is considered a key preserve for threatened Neotropical birds (Wege and Long 1995). Extensive stands of old-growth forest persist in the northern and eastern portions of the park; the southwestern sector was selec- tively logged in the 1950s (Fig. I). The cli- mate is seasonal, with 80% of annual rainfall occurring October-March. Summer tempera- tures in the region are extreme (mean maxi- mum = 47° C; l^rohaska 1959). The dominant vegetation is thorny, semi- deciduous forest dominated by quebracho Co- lorado santiaguefio (Schinopsis lorentzii), c)ue- bracho bianco {Aspidosperma quehracho- hlanco), and mistol {Zizyphus mistol), and is interrupted by belts of natural grasslands as- sociated with ancicFit river betls. I'he under- story is a dense, shrubby layer (4 m mean height), dominated by sacha poroto (Capparis retusa; Protomastro 1988, Talamo and Cazi- ani 2003). Above this layer, mistol forms a sparse layer with both quebracho species, the tops of which attain a mean height of 12 m (Lopez de Casenave et al. 1998). Sampling*. — We conducted bird surveys during six periods in Copo National Park (De- cember 1998, March 1999, August 1999, De- cember 1999, April 2000, and September 2000) in two forest types: old-growth and sec- ond-growth (i.e., 50 years after selective log- ging). In each forest type, we established eight mist-net stations, l(K) to 200 m apart, four in the understory (0-3 m above ground) and four in the canopy (5-8 m above the shrubby layer). At each station, we placed one mist net, 12.5 m long X 2.8 m high (36-mm mesh). We operated nets for 3 days in each tyjK' of forest tiuring each survey pcriotl (Ralph et al. 94 THE WILSON BULLETIN Vol. 117, No. 1, March 2005 1996), except for the second-growth forest in December 1998, when only 1 day of sampling occurred; thus, we mist-netted for 18 days in old-growth and 16 days in second-growth. We opened nets before sunrise and operated them for 3-6 hr/day when possible, but we often had to close nets early due to temperature and weather conditions. Canopy nets were in- stalled with a modification of the technique described by Humphrey et al. (1968), with trees supporting a system of pulleys and ropes. We added vertical aluminum poles for additional support. For each bird captured, we recorded species, forest type, layer, date, time, weight, standard morphological measure- ments, and sex. Each bird was banded with National Park Administration aluminum bands and released. Data were expressed as captures per 100 mist-net hr (MNH), includ- ing recaptures (Bibby et al. 1992). We established eight point-count stations, at least 400 m apart, in each of the two forest types. In each survey period, we twice visited all point-count stations to conduct 10-min un- limited-distance point counts on 2 consecutive days, reversing the order of visits to avoid time-of-day bias. Surveys began at sunrise and were completed within 3 hr (Bibby et al. 1992, Ralph et al. 1996, Gram and Faaborg 1997). During each point count, we recorded species and number of individuals detected by sight or sound, and the forest layer in which each individual was detected for the first time. Layers were defined as understory (0-4 m) and canopy (>4 m). Every individual seen or heard was recorded only once, so that obser- vations per layer were considered to be inde- pendent, and layers at a single station were treated as separate treatments in the analysis. Birds over-flying the canopy were not includ- ed. Results are expressed as number of detec- tions per 10 min (Bibby et al. 1992). One ob- server (EJD) conducted all point counts. Guilds were defined according to previous studies in the area (Caziani 1996, Lopez de Casenave et al. 1998) as follows; omnivores, carnivores, nectivores, terrestrial granivores, arboreal granivores, terrestrial insectivores, bark insectivores, foliage insectivores, short- flight insect hunters, long-flight insect hunters, frugivores, and undergrowth granivores. Statistical analyses. — We compared species richness using rarefaction curves, given that the number of individuals in a sample can in- fluence the number of recorded species (James and Rathbun 1981). Rarefaction estimates the number of species expected from different samples, based on multiple random sampling of increasing abundance. Curves were built with 1 ,000 iterations for each abundance level using Program EcoSim (Gotelli and Entsmin- ger 2002). The program calculates a 95% con- fidence interval for each mean species rich- ness value. Eor each survey method, we compared total records, total records by guild, and records of the most common species. We employed a factorial design with forest type as the first factor (two levels: old-growth forest and sec- ond-growth forest, a = 2) and layer as the second factor (two levels: understory and can- opy, b = 2). Replicates by treatment (forest X layer) were the four mist-net stations (r = 4) and the eight point-count stations (r = 8), re- spectively. Seasonality was not considered; however, the six survey periods were included in the analysis as repeated measures, using a split-plot ANOVA (Von Ende 1993). Assump- tions of ANOVA were satisfied by logarithmic transformation of the data. For the between- factor comparisons, error degrees of freedom were calculated as [a X b X (r - 1)]; due to the collapse of three nets in one survey period (two canopy nets and one understory net), 3 degrees of freedom were subtracted from the error degrees of freedom. Detrended correspondence analysis. — To describe the association of bird species and guilds with treatments (forest X layer), we ap- plied Detrended Correspondence Analysis (DCA) to the matrices of total captures by net stations and total detections by point-count stations using Program PC-ORD (Gauch 1982, McCune and Mefford 1997). DCA is an ordination technique that groups species and stations in a two-dimensional scatterplot, where species lying close together show sim- ilar use of forest layers and forest types, and forest layers and types lying close together have similar avian communities. RESULTS We recorded 91 species, including 13 re- corded only with mist nets and 43 only with point counts. An additional 17 species were observed either flying over the study area or Derlindati and Caziani • MIST NETS AND POINT COUNTS IN CHACO FOREST 95 TABLE 1. Mist-net hr (MNH), captures (C), captures per 100 MNH, species richness (S), and mean captures ± SE by forest type and by layer, Copo National Park, northwestern Argentina, 1998-2000. MNH is lower in second-growth forest because we lost one canopy mist net in three sample periods because of extreme weather, and we had only 1 day of sampling in December 1998. Layer Old-growth forest Second-growth forest MNH c C per 100 MNH s Mean ± SE MNH c C per 100 MNH s Mean ± SE Understory 360 134 37.2 40 49.6 ± 7.5 229 90 39.2 35 51.8 ± 8.8 Canopy 320 178 55.6 37 41.6 ± 6.5 202 105 52.0 37 41.1 ± 7.6 Total 680 312 45.8 45 45.6 ± 6.9 431 195 45.2 46 46.4 ± 8.1 outside of the sampling periods. The two methods combined detected 80% of the spe- cies reported for forest habitat in the area (Ca- ziani 1996). We captured 507 birds of 48 species in 1,111 MNH (34 days; Table 1). Recaptures represented 1.53% of total captures. We de- tected 907 individuals of 78 species in 32 point-count hr (Table 2). Considering both mist-net captures and point-count detections, 10 species were exclusive to old-growth for- est, 15 to second-growth forest, 28 to the can- opy, and 29 to the understory. Raptors (Ac- cipitridae and Falconidae), parrots and para- keets (Psittacidae), woodcreepers (Dendroco- laptidae), warblers (Parulidae), tanagers (Thraupidae), and caciques (Icteridae) domi- nated canopy records. Tinamous (Tinamidae), seriemas (Cariamidae), nightjars (Caprimul- gidae), antbirds (Formicariidae), and tapacu- los (Rhinocryptidae) were recorded only in the understory. Expected species richness (Fig. 2) was similar between census methods, forest layers, and forest types, as confidence intervals on rarefaction curves overlapped in all cases, with the exception of point counts in old-growth forest understory, which had significantly fewer species. Using mist nets, the species most often de- tected were Creamy-bellied Thrush {Turdus amaurochalifius). White-crested Elaenia {Elaenia albiceps), Small-billed Elaenia (E. parvirostris). Red-crested Einch (Conphos- pingus cucuUatus), and Red-eyed Vireo (Vireo olivaceus), representing 48% of total captures. Only White-crested Elaenias were captured more frequently in old-growth forest (F^ = 13.65, P = 0.005). Bark insectivores were captured more often in the understory than the canopy (Fj 9 = 5.27, P = 0.047), but no other guild showed a significant difference between layers. Using point counts, the species most often detected were Chaco Chachalaca {Ortcilis ccm- icollis). Masked Gnatcatcher (Polioptila dum- icola), Picazuro Pigeon {Coliimha picazuro). Stripe-backed Antbird (Myrmorchilus strigi- latLis), and Creamy-bellied Thrush, represent- ing 52% of total detections. The first three species were detected more often in second- growth forest (F| 28 = 4.47, P = 0.040; F, 28 - 3.76, P = 0.060; and F, 28 = 4.61. F < 0.001, respectively); Chaco Chachalaca was more abundant in the canopy (F, 28 = 10.03, P — 0.004), and Stripe-backed Antbird and Creamy-bellied Thrush were more abundant in the understory (F, 28 = 21.40. P < 0.001 and F| 28 = 7.7, P = 0.009). Total point-count detections per 10 min were significantly high- er in old-growth forest (F|2s = 6.85. P = TABLE 2. Point count [lours (PCH). total birds detected (D), detections per 10 min. species richness (,S). and mean detections ± .SI:, by I'orest type and layer, C'opo Ntilional I’ark. northwestern Argentina . 1W8-2000. Old-gmwih lores! Second gro\Mh loresi I) per 1) |vr Layer I>( H 1) 10 min S Mean ‘ SI IX II 1) 10 mm S Me.m SI Understory 8 222 4.6 29 29.7 " 3.3 8 175 3.b 38 24.1 ' 1.9 C'anopy 8 289 6.0 40 r \ 8 221 4.6 41 34.1 * 6.7 Ibtal 16 511 10.6 52 76.8 ‘ 4.4 1 b 3‘>b 8.2 61 73.5 * 7.1 96 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 LIG. 2. Species rarefaction curves show the ex- pected number of species related to the number of cap- tures in mist nets (top) and number of detections in point counts (bottom), by forest type and layer, Copo National Park, northwestern Argentina, 1998-2000. Dotted lines correspond to the 95% confidence interval for the expected number of species detected in old- growth forest understory. Confidence intervals on oth- er curves were omitted for clarity. (1) Second-growth forest understory, (2) second-growth forest canopy, (3) old-growth forest understory, and (4) old-growth forest canopy. 0.014) and in the canopy (F, 28 = 4.98, P = 0.034; Table 2). Short-flight insect hunters, omnivores, and terrestrial granivores were all more abundant in the understory than in the canopy (F,28 = 7.40, P = 0.011; = 42.37, P < 0.001; and, F, 2g = 32.8, P < 0.001, respectively). Bark insectivores and ar- boreal granivores were more abundant in the canopy (F, 2« = 55.07, P < 0.001; F, 28 = 22.55, P < 0.001). Terrestrial insectivores had higher abundances in second-growth forest (^1,28 ~ 7.4, P < 0.001), and undergrowth granivores were more abundant in old-growth forest (F, 28 = 18.8, P < 0.001). DCA analysis applied to the point-count matrix (Fig. 3A) clearly distinguished bird as- semblages between canopy and understory (Axis 1), and between old-growth and second- growth forest, especially for understory (Axis 2). Bark insectivores and arboreal granivores appeared to be associated with the canopy for both forest types. Terrestrial granivores char- acterized the understory. DCA analysis ap- plied to mist-net captures (Fig. 3B) also dis- tinguished bird assemblages between layers and forest types, though less clearly. Only two guilds (bark insectivores and short-flight in- sect hunters) showed clear patterns; both guilds were associated with the canopy. DISCUSSION In agreement with other studies, we detect- ed more species with point counts than with mist nets (Gram and Faaborg 1997; Whitman et al. 1997; Blake and Loiselle 2000, 2001; Wang and Finch 2002). The major advantage of mist nets is that less experience in species identification is required, and, in fact, census- ing with mist nets may aid the observer in gaining familiarity with different species (Ralph et al. 1995). In the understory, mist nets can be more effective than point counts m detecting smaller birds, or those with more cryptic plumage or secretive behavior (Mason 1996; Rappole et al. 1998; Blake and Loiselle 2000, 2001; Wang and Finch 2002). However, canopy mist nets require greater effort to in- stall (Humphrey et al. 1968, Meyers and Par- dieck 1993), and they are more affected by weather (e.g., wind entanglement in treetops). Canopy nets do overcome one of the principal deficiencies of mist nets: only sampling the lowest forest layer (Blake 1992, Remsen and Good 1996, Rappole et al. 1998). Some spe- cies, however, are not detectable with nets due to size or behavior (Blake and Loiselle 2001, Wang and Finch 2002). On the other hand, point counts are easier to conduct, and are more efficient in terms of data collected per unit of effort (Bibby et al. 1992). However, point-count detections may vary according to foliage density, visibility, and the transmission and perception of sounds during censuses (Schieck 1997). This may ac- count for the lower richness estimate obtained by point counts in the understory of old- growth forest (Fig. 2), the layer with highest foliage density (Lopez de Casenave et al. 1998; EJD and SMC unpubl. data). Further- more, point counts require training in species identification, particularly knowledge of vo- Derlindati and Caziani • MIST NETS AND POINT COUNTS IN CHACO FOREST 97 A Point counts: stations 100 - Axis 2 1 1 1 o<^ o ^ ^ ^ ♦♦ Oo OOo ^ .. • 0 - • Old-growth forest understory O Old-growth forest canopy ♦ Second-growth forest understory ^ Second-growth forest canopy 1 1 1 1 1 0 100 B Mist nets: stations Axis 2 o -400 - • Old-growth forest understory O Old-growth forest canopy ♦ Second-growth forest understory O Second-growth forest canopy ^ i i i i 1 i — -300 300 Point counts: species Short-flight insect hunters -RArboreal granivores ^Terrestrial granivores MYMO “ly^XIMA <;2> emau I^MA^AMAE - r\QcouE PIMI ARAC-^ LEAN CARU ^^CLP\ COMA A LEVE J^COPI ^ZEAU 1 1 0 1 1 1 1 100 Mist nets: . species ^susu o PAPO - COME 6> LE^ O ^DRBR (^Bark insectivores Short-flight insect hunters 1 1 1 -300 300 Axis 1 FIG. 3. Detrended Correspondence Analysis (DCA) using (A) point-count and (B) mist-net matrices, Copo National Park, northwestern Argentina, 1998-2000. For clarity, we show only species belonging to guilds that showed strong associations with forest type or layer. Axis 1 appears to be associated with layers and axis 2 with forest type. Species codes: AMAF (Amazona aestiva), ARAC {Aratin}>a acuticandata), CAFE {Campephilus leucopof’on), CARU {Casiornis rufa), CLPI (Coluniha picaznro), COMA (C. macidosa), COME {CoUiptcs melanolaimns), COPI {Columhina picid), DRBR {Drymornis hnd^esii), DRSC {Dryocopns schnlzi), EMAU {Empidonomiis anranlioalrocristaliis), LEAN (lA’pidocolaples angustirostris)^ LEVE (Leptotila verrcoNxi), MYMA (Myiodynastes nuiculalus), MYMO (Myiopsitta monachns), MYTY (Myiarchns tyrannidn.s), PAPO {Pa- chyraniphns polychopterus), PIMI U^icoides mixln.s), SUSU (Sniriri .sniriri), XIMA {Xiphocolapfes major), and /EAU (Zcfudda auricidata). cali/.ations (Bibby et aL 1992, Ralph ct al. 1996); consequently, cletectioti ability can vary signilicantly among observers (Rappole et al. 1998, Nichols et al. 2()()0). Similarly, species differ in characteristics that affect de- tection and identification (Nichols et al. 2()()(), Wang and Finch 2002), thereby increasing the variability td' results. Mist-net captures may reflect differences in activity, whereas point counts more likely re- flect variation in abundance (Remsen and Good 1996). In some cases, however, relative 98 THE WILSON BULLETIN • Vol. 117, No. I, March 2005 abundances obtained by the two methods are similar (Wang and Finch 2002). In Chaco for- est, we believe that mist-net captures reflected bird movements, whereas other activities (e.g., nesting, courtship, displays, and territorial singing) were more likely to be detected dur- ing point counts. Depending on the layer where activities occur, the probability of de- tection can vary greatly between methods (Blake and Loiselle 2000, 2001). For example, woodcreepers were detected more frequently in the canopy with point counts, but a larger number were captured with mist nets in the understory, where birds move from trunk to trunk. In contrast, most woodpeckers were only detected during point counts, as they tended to move between treetops above our canopy nets. These patterns are clear in the DCAs. The point-count DCA remained simi- lar, even when we repeated the analysis with the same number of replicates as that of mist nets, selected at random. The poor explana- tory power of the mist-net DCA was likely due to few or no captures of birds from some guilds (i.e., arboreal granivores, carnivores, long-flight insect-hunters). The utility of point counts and mist nets is influenced by vegetation structure (Blake and Loiselle 2000, 2001; Wang and Finch 2002): the relative contribution of each method may vary in different environments. In tall forests, canopy birds are poorly represented by both understory mist nets and point counts (Blake and Loiselle 2001). In Chaco forests, where canopies are lower, the point-count census technique was adequate and the contribution of canopy nets was less significant. Only un- derstory mist nets eaptured species not de- teeted on point counts. Nonetheless, the usual disadvantage of underestimating canopy birds during mist-netting efforts was at least par- tially avoided by using canopy nets (e.g., can- opy nets accounted for higher proportions of frugivores). Finally, comparisons of captures and counts among layers provided evidence of movement between resource patches. ACKNOWLEDGMENTS This study was supported by Project 997 (EJD), Project 752 (SMC), and a graduate fellowship (EJD), all from the Research Council of Salta National Uni- versity (CIUNSa). C. Trucco, A. Talamo, C. Braca- monte, P Cardozo, J. Chalub, and J. Gato proffered invaluable collaboration during fieldwork. M. Labrezi provided a vehicle for most of the field trips. We are very grateful to “Boni” Perez and family for their hos- pitality and assistance in the field. Thanks to A. Tal- amo for advice on the multivariate analyses. A. L. Su- reda and M. Cassels translated the Spanish version of the manuscript, and C. Trucco and D. Vazquez offered helpful critiques. We are very grateful to J. G. Blake, who gave us advice at an early stage of this research, and to J. Lopez de Casenave, J. H. Rappole, and K. Cockle for their insightful critiques of the English ver- sion of the manuscript. We also thank J. G. Blake, B. Poulin, and an anonymous reviewer, whose sugges- tions improved earlier versions of this manuscript. LITERATURE CITED Anderson, S. H. and H. H. Shugart, Jr. 1974. Hab- itat selection of breeding birds in an east Tennes- see deciduous forest. Ecology 55:828-837. Bibby, C. j., N. D. Burgess, and D. A. Hill. 1992. Bird census techniques. Academic Press, London, United Kingdom. Blake, J. G. 1992. Temporal variation in point counts of birds in a lowland wet forest in Costa Rica. Condor 94:265-275. Blake, J. G. and B. A. Loiselle. 2000. Diversity of birds along an elevational gradient in the Cordil- lera Central, Costa Rica. Auk 1 17:663-686. Blake, J. G. and B. A. Loiselle. 2001. Bird assem- blages in second-growth and old-growth forests, Costa Rica: perspectives from mist nets and point counts. Auk 118:304-326. Blake, J. G. and M. Rouges. 1997. Variation in cap- tures of understory birds in El Rey National Park, northwestern Argentina. Ornitologia Neotropical 8:185-193. Caziani, S. M. 1996. Interaccion plantas-aves disper- soras de semillas en un Bosque Chaqueno sem- iarido. Ph.D. dissertation, Universidad de Buenos Aires, Argentina. CoDESiDO, M. AND D. N. BiLENCA. 2000. Comparacion de los metodos de transecta de faja y de conteo de puntos de radio fijo en una comunidad de aves del bosque semiarido santiagueno. El Hornero 15: 85-91. Gardali, T, G. Ballard, N. Nur, and G. R. Geupel. 2000. Demography of a declining population of Warbling Vireos in coastal California. Condor 102:601-609. Gauch, H. G. 1982. Multivariate analysis in commu- nity ecology. Cambridge University Press, New York. Gotelli, N. j. and G. L. Entsminger. 2002. Ecosim: null models software for ecology, ver. 7. Acquired Intelligence, Inc. & Kesey-Bear, Burlington, Ver- mont. Gram, W. K. and J. Faaborg. 1997. The distribution of Neotropical migrant birds wintering in the El Cielo Biosphere Reserve, Tamaulipas, Mexico. Condor 99:658-670. Herrera, C. M. 1978. Ecological correlates of resi- dence and non-residence in a Mediterranean pas- Derlindati and Caziam • MIST NETS AND POINT COUNTS IN CHACO FOREST 99 serine bird community. Journal of Animal Ecolo- gy 47:871-890. Humphrey, P. S., D. Bridge, and T. E. Lovejoy. 1968. A technique for mist-netting in the forest canopy. Bird Banding 39:43-50. James, E C. and S. Rathbun. 1981. Rarefaction, rel- ative abundance, and diversity of avian commu- nities. Auk 98:785-800. Karr, J. R. 1976. Within- and between-habitat avian diversity in African and Neotropical lowland hab- itats. Ecological Monographs 46:457-481. Karr, J. R. 1977. Ecological correlates of rarity in a tropical forest bird community. Auk 94:240-247. Karr, J. R. 1981. Surveying birds with mist nets. Studies in Avian Biology 6:62-67. Loiselle, B. a. 1987. Migrant abundance in a Costa Rican lowland forest canopy. Journal of Tropical Ecology 3:163-168. Lopez de Casenave, J., J. P. Pelotto, S. M. Caziani, M. Mermoz, and j. Protomastro. 1998. Re- sponses of avian assemblages to a natural edge in a Chaco semiarid forest in Argentina. Auk 115: 425-435. Lovejoy, T. E. 1974. Bird diversity and abundance in Amazon forest communities. Living Bird 13:127- 191. Mason, D. 1996. Responses of Venezuelan understory birds to selective logging, enrichment strips, and vine cutting. Biotropica 28:296-309. McCune, B. and M. j. Mefeord. 1997. PC-ORD: mul- tivariate analysis of ecological data, ver. 3.0. MjM Software Design, Gleneden Beach, Oregon. Meyers, J. M. and K. L. Pardieck. 1993. Evaluation of three elevated mist-net systems for sampling birds. Journal of Eield Ornithology 64:270-277. Mills, T. R., M. A. Rumble, and L. D. Elake. 2000. Habitats of birds in ponderosa pine and aspen/ birch forest in the Black Hills, South Dakota. Journal of Field Ornithology 71:187-206. Nichols, J. D., J. E. Hines, J. R. Sauer, F. W. Fallon, J. E. Fallon, and P. J. Heglund. 2000. A double- ob.server approach for estimating detection prob- ability and abundance from point counts. Auk 1 17:393-408. Poulin, B., G. Lefevbre, and P Pilard. 2000. Quan- tifying the breeding assemblage of reedbed pas- serines with mist-net and point-count surveys. Journal of Eield Ornithology 71:443-454. Pkohaska, E 1959. El polo de calor de America del Sur. Instituto Nacional de Tecnologia Agropecu- aria, IDIA 141:27—30. Pkotoma.siro, j. j. 1988. Fenologfa y mecanismos de interaccion en el bosciue de quebracho Colorado, bianco, y mistol. Ph.D. dissertation, Universidad de Buenos Aires, Argentina. Ralph, C. J., G. R. Gi:ui>i:l, I^. I^yli:, I. I:. Martin, D. I- Di;santi;, and B. Mila. 1996. Manual de me- todos de campo para el monitoreo do aves terres- tres. General 'fechnical Report PSW-G'rR-159, IISDA forest Service, Pacilic Southwest Pescarch Station, Albany, California. RAt.BH, C. J., J. R. Saui K, and S. Dkoi:gi . 1995. Mon- itoring bird populations by point counts: staiulards and applications. General Technical Report PSW- GTR-149, USDA Forest Service, Pacific South- west Research Station, Albany, California. Rappole, j. H., K. Winker, and G. V. N. Powell. 1998. Migratory bird habitat use in southern Mex- ico: mist nets versus point counts. Journal of Field Ornithology 69:635-643. Remsen, j. V., Jr., and D. A. Good. 1996. Misuse of data from mist-net captures to assess relative abundance in bird populations. Auk 113:381-398. Restrepo, C. and N. Gomez. 1998. Responses of un- derstory birds to anthropogenic edges in a Neo- tropical montane forest. Ecological Applications 8:170-183. SCHEWSKE, D. W. AND N. Brokaw. 1981. Treefalls and the distribution of understory birds in a tropical forest. Ecology 62:938-945. SCHIECK, J. 1997. Biased detection of bird vocaliza- tions affects comparisons of bird abundance among forested habitats. Condor 99:179-190. Talamo, a. and S. M. Caziani. 2003. Variation in woody vegetation among sites with different dis- turbance histories in the Argentine Chaco. Forest Ecology and Management 184:79-92. Terborgh, j., S. K. Robinson, T. A. Parker, III, C. A. Munn, and N. Pierpont. 1990. Structure and organization of an Amazonian forest bird com- munity. Ecological Monographs 60:213-238. Thompson, I. D., H. A. Hogan, and W. A. Monte- VECCHi. 1999. Avian communities of mature bal- sam fir forests in Newfoundland: age-dependence and implications for timber harvesting. Condor 101:311-323. Verner, j. and K. L. Purcell. 1999. Fluctuating pop- ulations of House Wrens and Bewick’s Wrens in foothills of the western Sierra Nevada ot Califor- nia. Condor 101:219-229. Von Ende, C. N. 1993. Repeated-measures analysis: growth and other time-dependent measures. Pages 113-137 in Design and analysis of ecological ex- periments (S. M. Scheiner and J. Gurevitch, Eds.). Chapman and Hall, New York. Wallace, G. E., H. G. Alon.so, M. K. McNicholl, D. R. Batista, R. O. Prieto, A. L. Sosa, B. S. Oria, and E. a. H. Wallace. 1996. Winter sur- vey of forest-dwelling Neotropical migrant and resident birds in three regions ot Cuba. Condor 98:745-768. Wang, Y. and D. M. Finch. 2002. Consistency ot mist netting and point counts in assessing landbird spe- cies richness and relative abundance during mi- grations. Condor 104:59-72. Wi;gi;, D. C. and A. J. Long. 1995. Key areas tor threatened birds in the Neolropics. BirdLite C'on- servation Series, no. 5. BirdLife International. C ambridge. Unitetl Kingtlom. WiinMAN. A. A., .1. M. H \gan. 111. and N. V. L. Bko- KA\\ . 1997. A comparison ot bin.1 sur\oy tech- nitiues used in a subtropical forest. C’oiulor 99: 955 9G5. WINKII K, 11. AND M. Pkiiii IHNIK. 2001. Behavior and ecology of biixls in tropical rain finest eano- pies. I’lant Ideology 153:193 202. Short Communications Wilson Bulletin 1 17(1); 100-101, 2005 Eastern Bluebirci Provisions Nestlings with Flat-headed Snake Shelby C. Braman' ^ and Darrell W. Pogue' ABSTRACT. — There are few published reports of Eastern Bluebirds (Sialia sialis) taking vertebrate prey or provisioning their young with vertebrates. We report finding a dead flat-headed snake (Tantilla gracilis) in an Eastern Bluebird nest. Flat-headed snakes feed pri- marily on soft-bodied invertebrates; thus, it is unlikely that the snake was attempting to depredate the bluebird nestlings. Moreover, flat-headed snakes are fossorial and rarely occur in open habitats. Therefore, the snake was most likely captured by one of the adult bluebirds and brought to the nestlings as a food item. Received 7 November 2003, accepted 4 November 2004. With the exception of shrikes (Family Lan- iidae), most passerines generally feed insects and small fruits to their developing nestlings (Pinkowski 1978, Ehrlich et al. 1988, Gowaty and Plissner 1998). However, Eastern Blue- birds {Sialia sialis) occasionally have been re- ported to prey on vertebrates, such as shrews {Sorex spp.; Pinkowski 1974), snakes (uniden- tified species; Elanigan 1971), and skinks {Eu- meces spp.; Pitts 1978). In a box-nesting pop- ulation of Eastern Bluebirds in Oklahoma, Bay and Carter (1997) reported six different pairs of adults taking ground skinks {Scincella lateralis) as food items for nestlings over a period of several breeding seasons. Although provisioning bluebird nestlings with verte- brate food items has been observed, it is con- sidered a rare phenomenon in passerines (Ross 1989). During the 2003 breeding season, we mon- itored 20 nest boxes at Tyler State Park, in an upland, open shortleaf and loblolly pine {Fi- rms echinata, P. taeda, respectively) forest ap- proximately 22 km north of Tyler, Smith County, Texas. The nest boxes, which were attached to metal T-posts 1.5 m from the ground, were monitored weekly and nesting activity was recorded. ’ Dept, of Biology, Univ. of Texas at Tyler, 3900 University Blvd., Tyler, TX 75799, USA. ^ Corresponding author; e-mail: shelby braman @ hotmail.com On 6 May 2003, we found a small (8.3 cm in length), dead flat-headed snake {Tantilla gracilis) in an Eastern Bluebird nest. The snake was intact and slightly desiccated, but did not have any visible external injuries. The nest had been previously checked on 29 April and contained nestlings (12-13 days old) that were within 3 days of fledging. During visits to nest boxes at this site, we usually did not observe provisioning of young by adult birds nor did we observe Eastern Bluebirds taking prey resembling small snakes. However, we have removed Texas ratsnakes {Elaphe obsoleta) that had preyed on nestling Eastern Bluebirds in our nest box- es (SCB and DWP unpubl. data), but these are the only snakes we had previously recorded in nest boxes at this site. The flat-headed snake is a small, docile, burrowing snake that eats a variety of inver- tebrates, such as centipedes and soft-bodied insect larvae (Werler and Dixon 2000). Adult flat-headed snakes typically range in size from 17.8 to 20.3 cm, and usually are found be- neath rocks (Eord et al. 1991, Conant and Col- lins 1998, Werler and Dixon 2000). According to Werler and Dixon (2000), flat-headed snakes (over 500 specimens) were never caught out in the open during a long-term study of this species in Kansas. Ford et al. (1991) examined snake diversity in northeast- ern Texas and found a very low abundance of flat-headed snakes. They concluded that due to the burrowing nature of this species, it may be more abundant at a particular site than trap rates might indicate. At Tyler State Park, the abundance of flat-headed snakes is unknown. Due to the natural history (i.e., fossorial habits and invertebrate prey) and small size of this particular snake, it is unlikely that it was ca- pable of climbing the T-post and entering the nest box on its own. The primary foraging mode of Eastern Bluebirds is to scan the ground from a perch and then drop to the ground to subdue their 100 SHORT COMMUNICATIONS 101 prey (Pinkowski 1977). The adult Eastern Bluebird would have had no trouble subduing a prey item of this size and may have mistak- en the snake for a large insect larva. Addi- tionally, the nestlings would have had no dif- ficulty consuming food of this size. Therefore, it appears that one of the adult Eastern Blue- birds captured this small snake on the ground and then brought it to the nest as a food item for the nestlings. It is unclear why the snake was not eaten by the nestlings, although it may be because the snake was brought to the nest very near the time of fledging. ACKNOWLEGMENTS We would like to thank R. L. Gutberlet, Jr., for help with identification of the flat-headed snake. We are also grateful to W. A. Carter, J. D. Lang, and C. E. Braun for reviewing an earlier version of this manu- script and for providing many helpful suggestions. LITERATURE CITED Bay, M. D. and W. A. Carter. 1997. Use of ground skinks {Scincella lateralis) as food for nestling Eastern Bluebirds (Sialia sialis) in Oklahoma. Bulletin of the Texas Ornithological Society 30: 23-25. CONANT, R. AND J. T CoLLiNS. 1998. A field guide to Wilson Bulletin 1 1 7( 1 ): 1 0 1-103, 2005 Sapsuckers Usurp Christine A. Rothenbach' ABSTRACT — We document for the first time a Red-naped Sapsucker (Sphyrapicus nuchalis) usurping the nest of a Red-breasted Nuthatch {Sitta canadensis). A nuthatch nest in the incubation phase was usurped by a male Red-naped Sapsucker on 23 May 2003, and a sapsucker nest was initiated in the cavity on 1 June. Red-naped Sapsuckers are primary cavity excavators that normally nest in live and dead quaking aspens (Bopulus treniuloides) infected with heart rot fungus {f'onies spp.). Red-breasted Nuthatclies are weak ex- ' licosystem Science and Management I’rogram. College of Science and Management. Univ. of North- ern British C'olumbia. 3333 University Way. Briticc George, BC' V2N 4/9, ( anada. ‘Corresponding author; e-mail: carol henbach Qt’ hot mail .com reptiles and amphibians: eastern and central North America. Houghton Mifflin, Boston, Massachu- setts. Ehrlich, R R., D. S. Dobkin, and D. Wheye. 1988. The birder’s handbook: a field guide to the natural history of North American birds. Simon and Schuster, New York. Flanigan, A. B. 1971. Predation on snakes by Eastern Bluebird and Brown Thrasher. Wilson Bulletin 83: 441. Ford, N. B., V. A. Cobb, and J. Stout. 1991. Species diversity and seasonal abundance of snakes in a mixed pine-hardwood forest of eastern Texas. Southwestern Naturalist 36:171-177. Gowaty, P. a. and j. H. Plissner. 1998. Eastern Blue- bird {Sialia sialis). The Birds of North America, no. 381. Pinkowski, B. C. 1974. Predation on a shrew by an Eastern Bluebird. Wilson Bulletin 86:83. Pinkowski, B. C. 1977. Foraging behavior of the East- ern Bluebird. Wilson Bulletin 89:404-413. Pinkowski, B. C. 1978. Feeding of nestling and fledg- ling Eastern Bluebirds. Wilson Bulletin 90:84—98. Pitts, T. D. 1978. Foods of Eastern Bluebird nestlings in northwest Tennessee. Journal of the Tennessee Academy of Science 53:136-139. Ross, D. A. 1989. Amphibians and reptiles in the diets of North American raptors. Wisconsin Endan- gered Species Report, no. 59. Werler, j. E. and j. R. Dixon. 2000. Texas snakes; identification, distribution, and natural history. University of Texas Press, Austin. a Nuthatch Nest 2 and Christopher Opio' cavators that most commonly nest in broken-topped conifer snags. Nest usurpation was likely due to a shortage of suitable nest sites in our study plot. Re- ceived 26 April 2004, accepted 9 Deceinher 2004. dhe most common avian nest tisurpcrs in North America arc secondary cavity-nesling species, especially the LTiropean Starling {Sturnus \'iili>ari.s) and House Wren {Iro^lo- dyte.s (U'dou) (Short 1979. Lindell 199b. Do- herty and Grubb 2002). Although nest ustir- pation has also been doetimcnted anunig cav- ity-excavators, both types are thought to be a eonset|tienee of a shortage ol nest sites, com- 102 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 bined with niche convergence (Short 1979, Lindell 1996). We document for the first time a Red-naped Sapsucker {Sphyrapicus nuchal is) usurping the nest of a Red-breasted Nuthatch {Sitta canadensis). The usurpation occurred during a research project on nuthatch responses to re- storative treatments in ponderosa pine (Pinus ponderosa) forests in the Blue Mountains of northeastern Oregon. The study area was lo- cated in the Wallowa- Whitman National For- est north of Enterprise, Oregon (45° 37' N, 117° 15' W). The stand, located on a ridge top at an elevation of 1,170 m, was dominated by ponderosa pine interspersed with Douglas-fir {Pseudotsuga menziesii). The area had under- gone a prescribed understory burn in the fall of 2000, and the forest canopy was relatively open. On 27 April 2003, we discovered a Red- breasted Nuthatch nest in a broken-topped ponderosa pine snag. The snag was 6.5 m tall, had 75% of its bark remaining, and its diam- eter at breast height was 28.6 cm. All branches were present but partially broken off, and there were no outward signs of heart rot fun- gus {Pomes spp.). On the snag we observed exit holes of bark beetles (Dendroctonus spp.) but not wood-boring beetles (Cerambycids or Buprestids). The cavity was 6 m above ground and lacked the layer of pitch that is occasion- ally found around nuthatch nest cavities. Judg- ing by the dark color around the cavity en- trance and the lack of fresh wood chips at the base of the snag, the cavity was excavated at least 1 year prior to the 2003 nesting season. The snag was located within 10 m of the edge of a large (>50 ha) patch of forest and within 20-80 m of several other snags that appeared to have undergone a similar amount of decay. On 27 April, we watched nuthatch adults bring nesting material to the nest for 25 min. On 5 May, we believed that the nuthatches were not yet incubating because we frequently observed the female outside the cavity. During 30 min of observation on 1 1 May, the male brought food to the cavity entrance three times and fed the incubating female. After this visit, we checked the nest at least every 3 days. On 23 May, near the expected hatch date, we observed a male Red-naped Sapsucker en- larging the entrance to the nest. Within 20 min, the sapsucker had enlarged the cavity en- trance sufficiently to access the nesting ma- terial inside. The sapsucker pulled out nesting material and eggshells for the next 15 min, dropping material onto the ground at the base of the snag, or flying to the limb of a nearby ponderosa pine before dumping it. Nuthatches called from <100 m, but they never came to within 50 m of the nest during this period. By 28 May, both the female and male sap- suckers were entering the nest and excavating from within the cavity. On 20 June, we con- firmed the presence of sapsucker nestlings (by begging calls). The nest was still active on 28 June, but by 1 July, there was no activity. The nest failed approximately 13 days after the sapsucker eggs hatched. Red-naped Sapsuckers most often nest in live and dead quaking aspen (Populus trem- uloides; Martin and Eadie 1999) infected with heart rot fungus {Pomes igniarius\ Bent 1939, Crockett and Hadow 1975), or in western larch {Larix occidentalis; McClelland and McClelland 2000) and birch {Betula spp.; Kil- ham 1971, Tobalske 1992). Red-breasted Nut- hatches typically excavate their own cavities in broken-topped conifer snags in temperate coniferous and mixed coniferous forests (Stee- ger and Hitchcock 1998, Ghalambor and Mar- tin 1999). A shortage of potential nest sites within a given area, however, can cause the convergence of species on a particular nest niche (Lindell 1996). This convergence can lead to nest competition, including nest usur- pation (Lindell 1996). Emphasis should be placed upon documenting incidental occur- rences of nest usurpation in order to increase our understanding of this phenomenon. ACKNOWLEDGMENTS We thank the Wildlife Conservation Society for funding; K. L. Farris and S. Zack for equipment, ed- iting, and other support; T Brunk, E. M. Rehm, C. Talbert, and R. Wasson for field support; and A. Youngblood for additional funding and field logistics support. We would also like to thank B. R. McClelland and two anonymous reviewers for their time, insight, and thoughtful comments. LITERATURE CITED Bent, A. C. 1939. Red-naped Sapsucker. Pages 141- 145 in Life histories of North American wood- peckers. U.S. National Museum Bulletin, no. 174. Crockett, A. B. and H. H. Hadow. 1975. Nest site selection by Williamson’s and Red-naped sap- suckers. Condor 77:365-368. SHORT COMMUNICATIONS 103 Doherty, R F. and T C. Grubb, Jr. 2002. Nest usur- pation is an ‘edge effect’ for Carolina Chickadees Poecile carolinensis. Journal of Avian Biology 33:77-^2. Ghalambor, C. K. and T. E. Martin. 1999. Red- breasted Nuthatch (Sitta canadensis). The Birds of North America, no. 459. Kilham, L. 1971. Reproductive behavior of Yellow- bellied Sapsuckers. I. Preference for nesting in Fomes-'mfQciQd aspens and nest hole interrelations with flying squirrels, raccoons, and other animals. Wilson Bulletin 83:159-171. Lindell, C. 1996. Patterns of nest usurpation: when should species converge on nest niches? Condor 98:464-473. Martin, K. and J. M. Eadie. 1999. Nest webs: a com- munity-wide approach to the management and conservation of cavity-nesting birds. Eorest Ecol- ogy and Management 115:243-257. McClelland, B. R. and P. T. McClelland. 2000. Red-naped Sapsucker nest trees in northern Rocky Mountain old-growth forest. Wilson Bulletin 112: 44-50. Short, L. L. 1979. Burdens of the Picid hole-exca- vating habit. Wilson Bulletin 91:16-28. Steeger, C. and C. L. Hitchcock. 1998. Influence of forest structure and diseases on nest-site selection by Red-breasted Nuthatches. Journal of Wildlife Management 62:1349-1358. Tobalske, B. W. 1992. Evaluating habitat suitability using relative abundance and fledging success of Red-naped Sapsuckers. Condor 94:550-553. Wilson Bulletin 1 17( 1 ): 103-105, 2005 The Nest and Nestlings of the Wing-banded Antbird {Myrmornis torquata) from Southern Guyana Nathan H. Rice^’^'^ and Christopher M. Milensky^ ABSTRACT. — The Wing-banded Antbird {Myrmor- nis torquata) is a poorly known suboscine passerine found in lowland Amazonian forests. Here, we present new information about the nest and nestlings of this enigmatic species. Our findings differ from previous observations and notes on clutch size. Received 2 July 2004, accepted 9 December 2004. The Wing-banded Antbird {Myrmornis tor- cjLiatci) has long mystified avian systeniatists as to its taxonomic affinities. Prior to discov- ery of the first Wing-banded Antbird nest by Tostain and Dujardin (1988), some authors (Peters 1951, Meyer de Schauensee 1966) aligned this species with the ground antbirds (Formicariidae). The nest discovered by Tos- tain and Dujardin (1988) was placed off the ' Univ. of Kansas. Natural History Museum anti Dept. t)f Ficology & bivolutionary Biology, Lawrence, K.S 66045, USA. -Smithsonian Institution. Div. ot Birds, P.O. Box 37012, NHB L:607, MRC4 16, Washington, DC 20013- 7012, USA. ’ C'urrent address: Acatlemy ot Natural .Sciences, Or- nithology Dept.. 1900 Benjamin I ranklin I’kwy.. Phil- adelphia, PA 19103-1 195, USA. ' C’orresponding author: e-mail: rice(f»'acnatsci.org ground in the fork of a small tree, providing additional natural history evidence that the Wing-banded Antbird should be classified as a member of the typical antbird (Thamno- philidae) assemblage. The natural history and population centers for this species, however, remain poorly known (Zimmer and Isler 2003: 671). Zimmer and Isler (2003) also suggest that the Guianan region may be a productive region for the study of Wing-banded Antbirds. Here, we present additional information on the nest of the Wing-banded Antbird with the first description of nestlings and additional behav- ioral notes from Guyana. During an avifaunal and botanical survey of the Acari Mountains in extreme southern Guyana ( 1° 20' N, 58° 56' W, 250 m in ele- vation, 3 September 1998), we photographed the nest and collected the nestlings and adults of Wing-banded Antbirds. Birds and the nest were found in terra firmc forest approximately 5 km south of the Sipu Ri\er. fhe nest was found on the slope of a small hill about 0.5 km from a small stream in tall humid forest (30-50 111 in height) with a moderately dense undersiory. Adult birds were observed foraging on the 104 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 FIG. 1. Nest and nestlings of the Wing-banded Antbird, 3 September 1998, southern Guyana (photo by C. M. Milensky). ground and giving soft “chip” contact calls. As we approached the birds, we noticed they were foraging around a nest. The nest was lo- cated in the fork of a sapling that was 1 m tall and 1 cm in diameter (Fig. 1). Nest measure- ments were outside diameter (15-17 cm), in- side diameter (4-10 cm), inner cup depth (2- 3 cm), and outer cup height (4-5 cm). The nest was constructed of loosely woven twigs with a lining of rootlets. The two nestlings were featherless, but small feather sheaths were beginning to emerge (Fig. 1). Pinfeathers of most typical antbird nestlings begin to erupt 2—3 days after hatching, so we suspected that these birds had hatched recently (Zimmer and Isler 2003). Both adults were collected and made into study skins; specimens are stored at the Uni- versity of Kansas in Lawrence (male: KU 90355, 50 g, testes 6X3 mm; female: KU 89793, 45 g, ovary 8X4 mm, largest ova 2 mm, oviduct convoluted 2 mm). The nestlings were collected and preserved in formaldehyde (KU 89671, 89672). Both adults had insects in their stomachs. The nestlings weighed 9.6 and 9.8 g; the irides, tarsi, and maxilla were brown, the foot pads were gray, and the man- dible was orange with a brown tip. Tostain and Dujardin (1988) reported find- ing Wing-banded Antbird nests and families near the equator with only one egg or fledg- ling, respectively, and pointed out that this is unique among typical antbirds, which nor- mally lay two eggs per clutch. They suggest that this may have been due to a positive re- lationship between clutch size and latitude, with reduced clutches near the equator, similar to that reported for Black-spotted Bare-eyes (Phlegopsis nigromaculata; Willis 1979). Our observation contradicts this idea and suggests that factors other than latitude influence clutch size in Wing-banded Antbirds. Tostain and Dujardin (1988) also reported finding nests and fledglings from July-October, and our September record is congruent with this pu- tative breeding season. When foraging. Wing-banded Antbirds have been observed using their bills to probe SHORT COMMUNICATIONS 105 through leaf litter, and using jumping motions to move leaves (Tostain and Dujardin 1988, Zimmer and Isler 2003). The male and female we observed appeared to be scratching through the leaf litter with their feet, throwing leaves up to 20 cm in the air, similar to that reported in Zimmer and Isler (2003). The spe- cies’ foraging behavior has been described as “deliberate and inconspicuous’’ (Zimmer and Isler 2003), but our observation varies a bit from this account. Although the birds were deliberate in their movements, our attention was drawn to the birds because of the loud and conspicuous manner in which they scratched through the understory. Such de- tectability, however, may vary with local en- vironmental conditions (i.e., the relative dry- ness of the leaf litter). ACKNOWLEDGMENTS We would like to thank the Smithsonian Institution’s Biodiversity of the Guianas Program and Laboratory of Molecular Systematics, and the University of Kan- sas Bird Interest Group, for providing financial support for this expedition. The Guyanese Government kindly provided permits for our research in the Acari Moun- tains. M. Tamessar helped expedite the permit and ex- port process. K. J. Zimmer and K. Zyskowski provided helpful comments on an earlier version of this manu- script. This is manuscript number 90 in the Smithson- ian Institution Biological Diversity of the Guiana Shield Program publication series. LITERATURE CITED Meyer de Schauensee, R. 1966. The species of birds of South America and their distribution. Academy of Natural Sciences, Livingston Publishing Com- pany, Narberth, Pennsylvania. Peters, J. L. 1951. Check-list of birds of the world, vol. 7. Museum of Comparative Zoology, Cam- bridge, Massachusetts. Tostain, O. and J. Dujardin. 1988. Nesting of the Wing-banded Antbird and the Thrush-like Antpit- ta in French Guiana. Condor 90:236-239. Willis, E. O. 1979. Comportamento e ecologia da Mae- de-Taoca, Phlegopsis nigronuiculata (d’Orbigny & Lafresnaye) (Aves, Formicariidae). Revista Brasilei- ra de Biologia 39:117-159. Zimmer, K. J. and M. L. Isler. 2003. Wing-banded Antbird (Myrmornis torquata). Page 671 iti Hand- book of the birds of the world, vol. 8: broadbills to tapaculos (J. del Hoyo, A. Elliot, and D. A. Christie, Eds.). Lynx Edicions, Barcelona, Spain. Wilson Bulletin 1 1 7(1): 106— 1 1 1, 2005 Ornithological Literature Edited by Mary Gustafson THE METAZOAN PARASITE FAUNA OF GREBES (AVES: PODICIPEDIFOR- MES) AND ITS RELATIONSHIP TO THE BIRDS’ BIOLOGY. By Robert W. Storer. Miscellaneous Publications, no. 188, Museum of Zoology, University of Michigan. 2000: 90 pp. ISBN: 9991895418. $27.00 (paper).— THE METAZOAN PARASITE FAUNA OF LOONS (AVES: GAVIIFORMES), ITS RE- LATIONSHIP TO THE BIRDS’ EVOLU- TIONARY HISTORY AND BIOLOGY, AND A COMPARISON WITH THE PARA- SITE FAUNA OF GREBES. By Robert W. Storer. Miscellaneous Publications, no. 191, Museum of Zoology, University of Michigan. 2002. 44 pp. $13.20 (paper). — Are you tired of the narrow-standard articles that clog or- nithological journals? Are you eager for new ideas from a natural historian who takes a re- freshing and broader look at avian biology? If so, read Robert W. Storer’s masterly twin monographs on the parasites of loons and grebes, two often-associated groups of water- birds whose ancestry and relationship have long been controversial. To be sure, most ornithologists will skip over the “Results” of these papers, which in- clude (1) the dry documentation of the inter- nal (digenetic trematodes, tapeworms [ces- todes], spiny-headed worms [acanthocepha- lans], round worms [nematodes]) and external (leeches, mites, lice) parasites that have been reported living in or on each species of grebe and loon; (2) a list of known prey species and indications of their prominence in the diet (for food is the source of the infecting internal par- asite and the numerical abundance of an in- termediate host species determines the chanc- es of becoming infected); and (3) brief tuto- rials on the biology of parasites and examples of the life cycles of some important forms. These papers would be important enough (if unexciting) contributions if they consisted only of documentation, analysis, and review of the literature on parasites in these two groups. But they cover much more. Storer transcends the facts of who parasitizes whom and continues with broad-ranging reflections in which he distills a lifetime of thought about paleontology, anatomy, and natural history to consider how knowledge of parasites bears on understanding the evolution of loons and grebes. His “Discussion” centers on how the biology of the bird species relates to their par- asite faunas, and vice versa, and the routes taken to investigate this. For example — how does a bird’s morphology affect the parasites it acquires? Bill shape and size is related to differences in size and/or species of prey, which affects the relative number of different intermediate hosts taken. This is also related to maneuverability. Foot shape (including presence or absence of a muscle that flexes the second toe) is related to underwater ma- neuverability, allowing rapid pursuit of fish or constraining the bird to feeding from the bot- tom. The difference in prey results in different parasites. The grebes’ unique habit of feather eating helps them to cast pellets, which reduces a parasite’s chances of setting up house in the upper digestive tract. The feather mat may keep some parasites from reaching the lower tract. As lost feathers need to be replaced, it appears that the continual molt in some tracts is related to the challenge of being parasitized. Habitat has a major effect on parasites. Both loons and grebes have a totally aquatic life, but some move from fresh to salt water seasonally. Salt water may get rid of fresh wa- ter parasites but replace them with species from salt water prey. If the biology of the bird is important, what about the biology of the parasites? The num- bers and kinds of intermediate hosts play a role in determining the kinds of organisms that can be the definitive host. Unfortunately, we are woefully ignorant about the biology of parasites. Life cycles have been worked out for fewer than half the species of helminths reported from grebes. Of nematodes, 38 spe- cies are known to parasitize grebes; 9 of these species are considered to be grebe specialists. 106 ORNITHOLOGICAL LITERATURE 107 yet 3 are known only from the original de- scriptions. Despite sharing common habitats or local- ities for much of the year, loons and grebes harbor different parasite faunas, which reflect different histories. Storer reviews paleontolog- ical, geological, and biological evidence that bears on the history of the two groups and argues that it is time to speculate on origins, noting that “the best analyses of the evolution of any group of organisms are those based on the broadest range of supporting evidence.” This includes parasitology, which most avian taxonomists give short shrift. His general con- clusion is that loons developed from aquatic marine birds in the Northern Hemisphere and that grebes probably originated from marsh dwelling predecessors in South America or Antarctica (not Australia). The basis for his thinking (in Loon parasites, pp. 16-21) is re- quired reading for anyone considering the an- cestry of these groups — and even for those who may have pondered why grebes have lobed toes. His list of priorities for future work will keep students busy for decades. On a broader, but parallel topic, he pleads for mu- seums and universities to teach basic whole- animal biology, and bemoans students who “learn to make cladistic analysis before they know the basic biology of the organisms that they are analyzing.” Storer has played a major role as researcher and teacher in North American ornithology in the 20th century, and kicks off his 8th decade of refereed papers and the 21st century with a major accomplishment. These two works represent a synthesis and distillation of infor- mation from a lifetime of scholarship. They are memoirs in the true sense of the word, and they challenge us to peek behind a door hiding parasites — a door that most of us have left closed. We recommend these volumes not be- cause of the information about parasites but because they show what one needs to think about when studying birds. We congratulate the author and the Museum of Zoology at 'fhe University of Michigan for publishing ideas that would never appear in the journals and that will stimulate renewed thinking about the early evolution of these birds.— RICHARD C. BANKS and .I()SL:PH R. JLHL, .IR., National Museum of Natural History, Washington, D.C.; e-mail: banksr@ si.edu and grebe5k@cs.com THE BOWERBIRDS: Ptilonorhynchidae. By Clifford B. Frith and Dawn W. Frith, il- lustrations by Eustace Barnes. Oxford Uni- versity Press, New York. 2004: 508 pp., 8 col- or plates, 38 tables, 82 figures, 20 range maps. ISBN: 0198548443. $164.50 (cloth).— This 10th volume in Oxford University Press’ Bird Families of the World monograph series con- tinues the tradition of excellence established in previous volumes. It is written by two of the world’s leading bowerbird biologists. They co-authored 41 of the 1,048 references cited in the volume, and one or the other was first author on an additional 20. They undertook a world study tour of major institutional collec- tions to gather unpublished and widely scat- tered information about the biology of this fascinating family of birds. As a result of their labors, they have produced an exhaustive study that will likely be the standard reference on the Ptilonorhynchidae for decades. Bowerbirds have long been of interest to biologists. The family includes both monog- amous and polygynoLis species, some species of the latter showing pronounced plumage di- morphism, species of the former being largely monomorphic. They have proportionally larg- er brains than ecologically similar passerines, suggesting high intelligence. Males of some species build elaborate bowers, artistically decorated with colorful feathers, flowers, fruits, shells, bones, and a bewildering assort- ment of natural and man-made objects. Some manufacture paint and paint their bowers with plant-matter brushes. Like the birds-of-para- dise, elevation in the rugged mountains of New Guinea may be the most important sort- ing mechanism that has facilitated adaptixe ra- diation in the family. Whether your interests are in sexual selection, atlaptive radiation, for- aging ecology, or anything else, the bower- birds have something to olTcr. fhe book is di\ itled into two parts, the first consisting of seven thematic chapters, and the second consisting of family, genus, and spe- cies accounts. laxonomically. the authors treat the bowerbirds as a monophyletic family of 8 genera, 20 species, ami 23 additional subspe- 108 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 cies. All are confined to Australasia, with 12 species found in New Guinea and associated islands (10 endemic) and 10 found in Austra- lia (8 endemic). The 1st chapter is an intro- duction to the bowerbirds that highlights the long history of human interaction with them. Chapter 2 deals with systematics and bioge- ography, including the history of taxonomi- cally grouping the bowerbirds in the same family with the birds-of-paradise and the pre- sent view that the two groups belong in sep- arate families that are not as closely related as previously thought. Chapter 3 deals with for- aging and other behaviors and ecological cy- cles. Chapter 4 covers morphology, plumages, demography, bower sites, and the four types of bowers — “court,” “mat,” “avenue,” “maypole” — and their significance. The 5th chapter focuses on bower site acquisition — including courtship displays — and fidelity, and the 6th focuses on breeding biology and parental care. Chapter 7 is a treatment of the evolution of mating systems and the role of sexual selection. The first 7 chapters occupy 222 pages; some of the information in these chapters is redundant compared with infor- mation provided in the species accounts, but the redundancy was necessary for making comparisons and syntheses. Chapter 8, the second part of the book, consists of the family, genus, and species accounts, and occupies 214 pages. Each species account follows a format that usually includes the following sections: an introduction to the species (a thumb-nail sketch); description, including plumage and color; distribution; systematics, nomenclature, subspecies (if any), and measurements; habi- tats and habits; diet and foraging; vocaliza- tions and other sounds; mating system; bower sites and bowers; bower site attendance and activities; courtship behavior; breeding; sur- vival and longevity; annual cycle; status and conservation; knowledge gaps and research priorities; and aviculture. A range map for each species also includes the distributions of subspecies. For many species, spectrograms are included as well as photographs and line- drawings. The first color plate consists of six photographs of males at their bowers, and the second portrays six of females at their nests. Plates 3-8 illustrate the 20 species, including the male and female of sexually dimorphic species, subspecies where plumage differenc- es are pronounced, a few juveniles, and sev- eral intermediate plumages. The quality of the plates is uniformly excellent — beautiful paint- ings of beautiful birds. The book concludes with two appendices, the first a summary of plant species eaten by Australian bowerbirds, and the second a summary of the animal com- ponent of adult and nestling diets of 13 bow- erbird species, followed by a glossary, a bib- liography, and an index. A. J. Marshall, a great student of bower- birds, considered bowerbirds the most inter- esting of the 144 families of birds with respect to behavioral complexity. Many would agree with him, and this book brings together and organizes virtually all that is known about this interesting family of birds. It is well-written, well-organized, and beautifully illustrated. There is much that is not known about bow- erbirds, and, in the long run, the heuristic val- ue of this book may be crucial to increasing our knowledge about bowerbirds. I have ob- served 14 species of bowerbirds in the wild, and reading this book has enhanced my inter- est in that fascinating family of birds. It is an expensive book, but it is worth the price. I highly recommend it. — WILLIAM E. DAVIS, JR., Boston University, Boston, Massachu- setts; e-mail: wedavis@bu.edu BIOMETRICS OF BIRDS THROUGH- OUT THE GREATER CARIBBEAN BASIN. By Wayne J. Arendt, John Faaborg, George E. Wallace, and Orlando H. Garrido. Proceedings of the Western Foundation of Vertebrate Zo- ology, Volume 8, Number 1. 2004: 33 pp. plus a CD-ROM. ISSN: 05117550. $25.00 (pa- per).— The avifauna of the Caribbean Islands have prompted a large number of ground- breaking studies in such diverse areas as bio- geography (Ricklefs and Cox 1972), commu- nity structure (Case et al. 1983, Faaborg 1985), parasitology (Fallon et al. 2004), and the ecology of overwintering migrants (Faa- borg et al. 1984, Holmes et al. 1989, Marra et al. 1998). With the rise of DNA-based studies and molecular phylogenies, some people may harbor the notion that ornithological studies based in biometrics are a thing of the past. But with the present contribution of a massive data set on the biometrics of birds of the Caribbean ORNITHOLOGICAL LITERATURE 109 Basin from Wayne Arendt and co-authors, the Caribbean Islands continue to offer possibili- ties for new and revealing analyses of avian ecology and evolution. Based on the measurement of almost 30,000 individual live birds of 276 species captured with mist nets, this publication pre- sents morphological measurements for as many as nine characters, including body mass, and lengths of the wing chord, penultimate primary, tarsus, central rectrix, exposed cul- men, culmen from the nares, and culmen depth and width. In addition, age and sex of each individual were recorded when known. While many of the data are from Puerto Rico, a total of 30 islands are represented, with sig- nificant samples from Cuba and the Domini- can Republic, as well as many smaller islands traditionally less-studied by ornithologists. The printed portion of this short publication begins with a preface containing a history of this compilation of avian biometrics and a summary of the many sources of data gath- ered here. There follows a somewhat out-of- place section on the uses of morphological data, including an extensive listing of repre- sentative works in avian genetics and evolu- tion, energetics, age and sex determination, ecomorphology, conservation and manage- ment, biogeography, and population and com- munity ecology. While this section serves well as a ready source of references to bio- metric-based studies, it more rightly belongs in the introduction and/or discussion sections, where much of the same material is repeated. Following the preface, the authors present a short introduction, wherein the importance of morphological measures to various subdis- ciplines of ornithology is reiterated and other sources of mensural data are detailed. The fo- cus is appropriately placed on the outstanding need for body mass, and especially appendic- ular measurements, of Caribbean birds. Study areas are briefly described, and rncthods of obtaining measurements are detailed, though these are by now fairly standardized. Most im- portant is a section explaining how to read the “Morphometries Table” and the individual files for each species, all of which are pre- sented on the CD that accompanies this vol- ume. Analyses and results are limited to the descriptive statistics of mean, standard devi- ation, and range for body mass and longitu- dinal measurements. The discussion again re- iterates the potential value of biometric data and concludes with the authors’ statement that they hope this publication will “serve as a tool for future researchers to use in their stud- ies in the West Indies and throughout the Greater Caribbean Basin to better explain the morphological variation among the birds.” The literature cited section contains a useful bibliography of nearly 300 references, many of which are examples of how avian biomet- rics data have been used. The heart of this publication is undoubtedly found in the accompanying CD, which con- tains all of the raw data as well as summary statistics for 30,000 individuals. Species are presented in phylogenetic order, and then grouped by island, age, and sex, so that sub- sets of these data are easily extracted. Descrip- tive statistics and sample sizes are presented for the species as a whole, and for each island, with separate statistics by age and sex (when known). These statistics are found at the end of the species-specific tables, but are more easily accessible and summarized in the single “Morphometric Table” for all species. Spe- cies-specific data can be found in this table, or through a convenient index of species names. Although this index presents only Lat- in names, this should be a minor inconve- nience to only the occasional user. Negative criticisms of this work are few. A convenient summary of banding sites and vegetation associations is printed as a table, but I think these site descriptions could be sig- nificantly enhanced by adding latitude and longitude coordinates or other locational in- formation so that the reader may determine more precisely where sites are found. In ad- dition, descriptions of vegetation associations are very basic (i.e., wet, dry, mesic, dwarf), and would be more valuable if more detailed. 1 found few' problems with the text, although in two places the authors attempt incorrectly to identify species to the subspecific level. The Sharp-shinned Hawk is identified as /\r- cipitcr strialus Venator on all islands, which is the form found only on Puerto Rico; other forms are resident on Hispaniola (/\. .v. stria- tus) anti CTiba (/\. .s. frini>illoi(le.s). Similarly, the Palm Warbler (Deitdroica pahnannn) is misidcntifietl as the Yellow Palm Warbler on all islantls. fhe bellow Palm Warbler (/L p. 110 THE WILSON BULLETIN • Vol. 117, No. 1, March 2005 hypochrysea) occurs in the West Indies, but is far less abundant than the Western Palm War- bler (D. p. palmarum). Finally, while this publication may be crit- icized for its lack of in-depth analyses, that task would be monumental; the potential ap- plications and uses of the data as presented are enormous. Rather than jealously guarding the data, these authors and their collaborators are to be congratulated for sharing the raw data so that we all might join in the fun and benefit from its use. Publication of this data set is also likely to spur the emergence of ad- ditional data. As the authors point out, 30,000 birds is a large number, but once samples are divided by species, age, sex, and island, sam- ple sizes can diminish quite rapidly, especially for the least common species. Additional data may be required for meaningful analyses of variation in biometrics of many of these spe- cies, and many of the most interesting endem- ics are not represented at all. Nevertheless, alongside the Western Foun- dation of Vertebrate Zoology’s publication of a bibliography of ornithology in the West In- dies (Wiley 2000), this monumental work of biometric data represents a significant advance in Caribbean ornithology. Although not in- tended for popular consumption, the work should find a place in the collections and da- tabases of researchers interested in avian sys- tematics and evolution, morphology and eco- morphology, avian biogeography and ecology in general, and Caribbean ornithology in par- ticular.—STEVEN C. LATTA, PRBO Con- servation Science, Stinson Beach, California; e-mail; slatta@prbo.org LITERATURE CITED Case, T. J., J. Faaborg, and R. Sidell. 1983. The role of body size in the assembly of West Indian bird communities. Evolution 37:1062-1074. Faaborg, J. 1985. Ecological constraints on West In- dies bird distributions. Ornithological Mono- graphs 36:621-653. Faaborg, J., W. J. Arendt, and M. S. Kaiser. 1984. Rainfall correlates of bird population fluctuations in a Puerto Rican dry forest: a nine-year study. Wilson Bulletin 96:575-593. Fallon, S. M., R. E. Ricklees, S. C. Latta, and E. Bermingham. 2004. Temporal stability of insular avian malarial parasite communities. Proceedings of the Royal Society of London, Series B 271: 493-500. Holmes, R. T, T. W. Sherry, and L. Reitsma. 1989. Population structure, territoriality and overwinter survival of two migrant warbler species in Jamai- ca. Condor 91:545—561. Ricklees, R. E. and G. W. Cox. 1972. Taxon cycles in the West Indian avifauna. American Naturalist 106:195-219. Marra, P. P, K. a. Hobson, and R. T. Holmes. 1998. Linking winter and summer events in a migratory bird using stable carbon isotopes. Science 282: 1884-1886. Wiley, J. W. 2000. A bibliography of ornithology in the West Indies. Proceedings of the Western Foun- dation of Vertebrate Zoology, no 7. BIRDS OE ECUADOR. By Niels Krabbe and Jonas Nilsson. Bird Songs International BV, Netherlands. 2004. DVD-ROM for Win- dows 98, ME, 2000, XR— This DVD is a compendium of 6,015 individual recordings of 1,184 species, and 824 photographs of 469 species. Learning bird vocalizations greatly enhances the number of species that can be detected on almost any birding trip, but is es- pecially important in the tropics. It can be dif- ficult to find recordings that cover even the common species for most of the Southern Hemisphere, and comparing vocalizations can be a frustrating experience. This DVD brings vocalizations of nearly all of Ecuador’s birds together to aid in learning and comparing vo- calizations. This DVD uses modern technology to great advantage by placing the vocalizations of the vast majority of Ecuadorian birds on your computer and at your fingertips. The DVD is organized taxonomically by family. Clicking on a family brings up a species list with icons that indicate whether a photograph or sound track is available for a given species. Clicking on the species brings up a small image of the photograph (if available) and lists the sound recordings available. For some species, there is information on taxonomy or recent splits. Many recordings may be available for each species, and if appropriate, they are separated by subspecies. Information under the sound bar for each selection includes a rating of the quality of the recording, the type of vocali- zation (song, call, duet, etc.) and whether the vocalization was recorded under natural con- ditions or after playback. Yet another click on the twistee under the sound bar brings up complete information on the recording, in- ORNITHOLOGICAL LITERATURE 111 eluding the recordist, location, date, time of day, archive or reference information, and of- ten the identification of other species heard in the recording. The location where it was re- corded is a clickable link that takes you to two maps showing Ecuador and South America, with the recording location indicated by a dot on the maps. I had no trouble using the “Playlist” fea- ture to create playlists for various geographi- cal regions of Ecuador. Creating a playlist in- volves dragging and dropping recordings to the list. Playing the list requires one click. As the list is played, the species’ twistee opens, showing all recordings on the list for that spe- cies, and, as each recording is played, the in- formation on that eut is displayed. Once a playlist is ereated, the program will build a folder of the selections that may be copied to other media for use in whatever software the owner has on their computer. Again, this is straightforward, and creating the folder to use for burning a CD is easy. The recordings are variable in quality (good to excellent), and, as most are unfiltered, there is background noise of microphones, rain, and other (unidentified) animals. Some of the euts contain human speech or other sounds (a Spanish radio station, for example). To me, it is preferable to have these intrusions than to have them cut out of the recording (changing the time between vocalizations) or filtered out (altering the recording). The first time I came across a snippet of Dutch on a recording it made me feel as though I was in the field with Krabbe and Nilsson, and their excitement was palpable, adding to the experience of listening to the recording and not detracting from it. Not all recordings are identified with 100% certainty. When there is any doubt as to the species represented, there is a notation under the sound bar with a percent certainty rating Irom 50 to 99%. While it is always preferable to have recordings of known bird origin, some species do not vocalize where they can be seen. As long as the uncertainty is identified (as it is here), to me it is better to have a 99% certainty in identity than to have a blank in the species list or the variation in vocaliza- tions left unrepresented. The photographs are also variable in qual- ity. I have to admit, I would not buy the DVD for the photographs alone. They are a wel- come addition to the whole, and some are tru- ly fantastic, including an admittedly some- what fuzzy photograph of a recently described Jocotoco Antpitta (Grallana ridgelyi) in the wild. Many photos depict birds in hand, some head studies, and some of the entire bird. Us- ing the slide show feature, full-screen shots of the birds are shown on the computer screen and change at the selected time interval. The species, subspecies, scientific name, and pho- tographer are displayed in a narrow bar on the top, and four icons at the bottom allow you to browse forward or backward through the slideshow; they provide information on the date and place the photograph was taken and contact information for the photographer. The DVD may be installed in English or Spanish versions. There is a useful errata page on the Web, with a patch that allows users to “see” an otherwise unavailable species. The DVD was easy to load on both a desktop PC and a laptop, and its use and playlists were easily created using the Help feature the first time; those needing assistance will find con- tact information for Help in the “read me” documentation. This “read me” note also in- cludes important information on how the re- cordings were edited, and it includes the ac- knowledgments. This product includes 69 hours of vocalizations of the birds of Ecuador. It will be extremely useful to field biologists and birders who want to learn the vocaliza- tions of these species. This DVD is highly rec- ommended.—MARY GUSTALSON. Patux- ent Wildlife Research C’enter, Laurel. Mary- land; e-mail; mary_gustafson C^Tisgs. go\ ’ .5*'4v|^ v^'^'Fi**’”*' fl*' ■'^ AT ; 1, f.*/ |t i'/i ' hHI .‘t'i . ’• , » * k r • ;: \ I*. Ji • tl ^ f "i’” *f1.4‘i.' .■ - %i; . >”jir j., ' .V.- ■ v'r> if.* . •» . . • > . ‘:. . u...ii'^.'-i, ^|| , C '• ■ ‘ - f *■' 1 n t '>i?»/t: rgin* i ' ' t,*f.-. .if?-' ';:V-A?-*^^r' 4r/:W» ' [ftv-ai^piilnpen^ «ivi^ ^‘il i-'!- VJ . ' ■ .’*f-.VSS5R'JJ»nWi “'v- '• - K .' ».jVi-. •••«?. 5»7t'K‘ * ){#f®'-'’r «’*V idi^U ;»fi«i§idi|^. j ^It35?'i?^ «i;. J •it’H ini « - ‘ ■vAaAtidJ- ■: . .:■!'••> v.si**ifV.d i»i, -» /> : i Wt t-.r ■ ♦ ♦ ^ :^td% '• if, ./;..> ‘Cj^Xv,*'’*^"'* < V^ : ,8 Ji.!^ M~Ti v‘1-^'? *‘ ‘ ‘'.r .‘’fs f'diii.. i’.V^\.,'-f' M»»fr5r.-it.*v?'iU I^W'rtV '^j^^v>!»>-^'?\4./r. 'rnv^vV,'.’ f?.#' t. T.ifiap*^:Qu. hV '' ftib -.tt'*’ •■•, ' '^ '•• --t'' ;.-- :’fs f-jiu.. iM AfRorr^i.* i* -'v.MUjt •^ V ■c“^Tilf/nr*i.:ii 1 ,-, •» i; ir •?'**■ . '. ;. 3Xil ; V .'/ (!> ■*'! j'-.-rj^’ .4 h4 ^ ^ • ■ '• ■ ' ‘ •■■ . ,..< V ciift V; ‘ ej Mu‘iju.f.b , •■). ' '•■'■'^^g ••■" 7 • "' w'-'’, r-llv >v<«TBSt-«-.^'» v»(^^ ■w* '■- ■K*' f 1 This issue of The Wilson Bulletin was published on 19 April 2005. • « €' T M~. 112 THE WILSON BULLETIN Editor JAMES A. SEDGWICK U.S. Geological Survey Fort Collins Science Center 2150 Centre Ave., Bldg. C. Fort Collins, CO 80256-8118, USA E-mail: wilsonbulletin@usgs.gov Editorial Assistants M. BETH DILLON CYNTHIA P. MELCHER Editorial Board KATHY G. BEAL CLAIT E. BRAUN RICHARD N. CONNER KARL E. MILLER Review Editor MARY GUSTAFSON U.S. Geological Survey Patuxent Wildlife Research Center Laurel, MD 20708-4037, USA E-mail: WilsonBookReview @aol.com Index Editor KATHY G. BEAL GUIDELINES FOR AUTHORS Consult the detailed “Guidelines for Authors” found on the Wilson Ornithological Society Web site (http://www.ummz.lsa.umich.edu/birds/wilsonbull.html). NOTICE OF CHANGE OF ADDRESS If your address changes, notify the Society immediately. Send your complete new address to Ornitho- logical Societies of North America, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. The permanent mailing address of the Wilson Ornithological Society is: % The Museum of Zoology, The Univ. of Michigan, Ann Arbor, MI 48109. Persons having business with any of the officers may address them at their various addresses given on the inside of the front cover, and all matters pertaining to the Bulletin should be sent directly to the Editor. MEMBERSHIP INQUIRIES Membership inquiries should be sent to James L. Ingold, Dept, of Biological Sciences, Louisiana State Univ., Shreveport, LA 71115; e-mail: jingold@pilot.lsus.edu CONTENTS A PRACTICAL MODEL OF BICKNELL’S THRUSH DISTRIBUTION IN THE NORTHEASTERN UNITED STATES — u. — j Daniel Lambert, - ^ent P. McFarland, Christopher C. Rimmer, Steven D. Faccio, and Jonathan L. Atwood OFFSHORE MARINE OBSERVATION OF WILLOW PTARMIGAN, INCLUDING WATER LAND- INGS, KUSKOKWIM BAY, ALASKA Christian E. Zimmerman, .Nicola Hillgruber, Sean E. Burril, Michelle A. St. Peters, and Jennifer D. Wetzel MINIMUM POPULATION SIZE OF MOUNTAIN PLOVERS BREEDING IN WYOMING : Regan E. Plumb, Fritz L. Knopf, and Stanley H. Anderson NEST SURVIVAL RELATIVE TO PATCH SIZE IN A HIGHLY FRAGMENTED SHORTGRASS PRAIRIE LANDSCAPE Susan K. Shagen, Amy A. Yackel Adams, and Rod D. Adams COMPARISON OF DAILY AVIAN MORTALITY CHARACTERISTICS AT TWO TELEVISION TOWERS IN WESTERN NEW YORK, 1970-1999 Arthur R. Clark, Colleen E. Bell, and Sara R. Morris A NEW MODEL TO ESTIMATE DAILY ENERGY EXPENDITURE FOR WINTERING WATERFOWL - Richard A. McKinney and Scott R. McWilliams APPARENT PREDATION BY CATTLE AT GRASSLAND BIRD NESTS — — Jamie L. Nack and Christine A. Ribic INFLUENCE OF FORAGING AND ROOSTING BEHAVIOR ON HOME-RANGE SIZE AND MOVE- MENT PATTERNS OF SAVANNAH SPARROWS WINTERING IN SOUTH TEXAS Daniel L. Ginter and Martha J. Desmond BREEDING ECOLOGY OF THE PUAIOHI (MYADESTES PALMERI) Thomas J Snetsinger, Christina M. Herrmann, Dawn E. Holmes, Christopher D. Hayward, and Steven G. Fancy EFFICACY OF USING RADIO TRANSMITTERS TO MONITOR LEAST TERN CHICKS Joanna B. Whittier and David M. Leslie, Jr. USING CANOPY AND UNDERSTORY MIST NETS AND POINT COUNTS TO STUDY BIRD ASSEMBLAGES IN CHACO FORESTS Enrique J. Derlindati and Sandra M. Caziani SHORT COMMUNICATIONS EASTERN BLUEBIRD PROVISIONS NESTLINGS WITH FLAT-HEADED SNAKE Shelby C. Braman and Darrell W. Pogue SAPSUCKERS USURP A NUTHATCH NEST Christine A. Rothenbach and Christopher Opio THE NEST AND NESTLINGS OF THE WING-BANDED ANTBIRD {MYRMORNIS TORQUATA) FROM SOUTHERN GUYANA — Nathan H. Rice and Christopher M. Milensky ORNITHOLOGICAL LITERATURE Tfie Wilson Bulletin PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY VOL. 117, NO. 2 JUNE 2005 PAGES 113-210 (ISSN 0043-5643) MCZ LIBRARY JUN 2 9 ZOGb HARVARD UNIVERSITY THE WILSON ORNITHOLOGICAL SOCIETY FOUNDED DECEMBER 3, 1888 Named after ALEXANDER WILSON, the first American Ornithologist. President — Doris J. Watt, Dept, of Biology, Saint Mary’s College, Notre Dame, IN 46556, USA; e-mail; dwatt@saintmarys.edu First Vice-President — James D. Rising, Dept, of Zoology, Univ. of Toronto, Toronto, ON M5S 3G5, Canada; e-mail: rising@zoo.utoronto.ca Second Vice-President — E. Dale Kennedy, Biology Dept., Albion College, Albion, MI 49224, USA; e-mail: dkennedy@albion.edu Editor — James A. Sedgwick, US. Geological Survey, Fort Collins Science Center, 2150 Centre Ave., Bldg. C, Fort Collins, CO 80526, USA; e-mail: wilsonbulletin@usgs.gov Secretary — Sara R. Morris, Dept, of Biology, Canisius College, Buffalo, NY 14208, USA; e-mail: morriss@canisius.edu Treasurer— Melinda M. Clark, 2684 Highland Dr., South Bend, IN 46635, USA; e-mail: MClark@tcservices.biz Elected Council Members — Robert C. Beason, Mary Gustafson, and Timothy O’Connell (terms expire 2006); Mary Bomberger Brown, Robert L. Curry, and James R. Hill, III (terms expire 2007); Kathy G. Beal, Daniel Klem, Jr., and Douglas W. White (terms expire 2008). Membership dues per calendar year are: Active, $21.00; Student, $15.00; Family, $25.00; Sustaining, $30.00; Life memberships $500 (payable in four installments). The Wilson Bulletin is sent to all members not in arrears for dues. THE JOSSELYN VAN TYNE MEMORIAL LIBRARY The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed in the Univ. of Michigan Museum of Zoology, was established in concurrence with the Univ. of Michigan in 1930. Until 1947 the Library was maintained entirely by gifts and bequests of books, reprints, and ornithological mag- azines from members and friends of the Society. Two members have generously established a fund for the purchase of new books; members and friends are invited to maintain the fund by regular contribution. The fund will be administered by the Library Committee. Terry L. Root, Univ. of Michigan, is Chairman of the Committee. The Library currently receives over 200 periodicals as gifts and in exchange for The Wilson Bulletin. For information on the library and our holdings, see the Society’s web page at http://www.ummz.lsa.umich.edu/birds/wos.html. With the usual exception of rare books, any item in the Library may be borrowed by members of the Society and will be sent prepaid (by the Univ. of Michigan) to any address in the United States, its possessions, or Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers, as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to: Josselyn Van Tyne Memorial Library, Museum of Zoology, The Univ. of Michigan, 1 109 Geddes Ave., Ann Arbor, MI 48109-1079, USA. Contributions to the New Book Fund should be sent to the Treasurer. THE WILSON BULLETIN (ISSN 0043-5643) THE WILSON BULLETIN (ISSN 0043-5643) is published quarterly in March, June, September, and December by the Wilson Ornithological Society, 810 East 10th St., Lawrence, KS 66044-8897. The subscription price, both in the United States and elsewhere, is $40.00 per year. Periodicals postage paid at Lawrence, KS. POSTMASTER: Send address changes to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. All articles and communications for publications, books and publications for reviews should be addressed to the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology, Ann Arbor, Michigan 48109. Subscriptions, changes of address and claims for undelivered copies should be sent to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. Phone; (254) 399-9636; e-mail: business@osnabirds.org. Back issues or single copies are avail- able for $12.00 each. Most back issues of the Bulletin are available and may be ordered from OSNA. Special prices will be quoted for quantity orders. All issues of The Wilson Bulletin published before 2000 are accessible on a free Web site at the Univ. of New Mexico library (http://elibrary.unm.edu/sora/). The site is fully searchable, and full-text reproduc- tions of all papers (including illustrations) are available as either PDF or DjVu files. © Copyright 2005 by the Wilson Ornithological Society Printed by Allen Press, Inc., Lawrence, Kansas 66044, U.S.A. 0 This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). FRONTISPIECE. Iquitos Gnatcatcher (Polioptila clementsi sp. nov.), the fourth new bird species described from the Reserva Nacional Allpahuayo-Mishana near Iquitos, Peru since 1998; tree is Caraipa tereticaulis (Clusi- aceae). Original watercolor painting by Lawrence B. McQueen. THE WILSON BULLETIN A QUARTERLY JOURNAL OF ORNITHOLOGY Published by the Wilson Ornithological Society VOL. 117, NO. 2 June 2005 PAGES 113-210 Wilson Bulletin 1 17(2): 11 3- 127, 2005 A NEW SPECIES OF GNATCATCHER FROM WHITE-SAND FORESTS OF NORTHERN AMAZONIAN PERU WITH REVISION OF THE POLIOPTILA GUIANENSIS COMPLEX BRET M. WHITNEY' 3 AND JOSE ALVAREZ ALONSO^ ABSTRACT. — We describe a new species of gnatcatcher, Polioptila clementsi, from white-sand {varillal) forest at the Allpahuayo-Mishana National Reserve, about 25 km by road west of Iquitos, Peru. To date, the new species is known only from the reserve, and is rare even there. Comparisons of morphological and vocal characters confirm that it is a member of the Polioptila guianensis complex, which comprises at least three poorly known, allopatric taxa ranging from the Guianas and the Rio Negro region through much of Amazonia south of the Amazon River. Roughly equivalent levels of phenotypic differentiation are documented for all taxa east of the Andes, including the new species. In consideration of the fact that some other species complexes in the genus comprise sister taxa showing lower levels of phenotypic differentiation, both morphologically and vocally, we recommend that Polioptila guianensis, P. facilis, and P. paraensis henceforth be recognized as separate species. Received 4 June 2004, accepted 1 March 2005. RESUMEN. — Describimos una nueva especie de perlita, Polioptila clementsi, del bosque de arena blanca I {varillal) de la Reserva Nacional Allpahuayo-Mishana, a 25 km por carretera al oeste de Iquitos, Peru. Hasta la fecha, la nueva especie es conocida solamente de la reserva, y es rara incluso alli. Comparaciones de caracteres I morfologicos y vocales confirman que es un miembro del complejo Polioptila guianensis, que comprende al menos tres taxones alopatricos muy poco conocidos, que se extienden desde la region de las Guyanas y el Rio : Negro a traves de gran parte de la Amazonia al sur del Rio Amazonas. Son documentados niveles aproxima- damente equivalentes de diferenciacion fenotipica para todos los taxones al este de los Andes, incluyendo la I nueva especie. En consideracion al hecho de que algunos otros complejos de especies en el genero comprenden j taxones hermanos que muestran una diferenciacion fenotipica menos marcada, tanto morfoldgica como vocal, recomendamos que de aqui en adelante Polioptila guianensis, P. facilis, y P. paraensis sean reconocidas como especies separadas. The recent discovery of two species of birds new to science (Ancient Antwren, Herp- silochnnis gentryi and Allpahuayo Antbird, Pcrcnostola areiuiriim) and several others pre- viously unknown from Peru in the white-sand forests of northern Loreto has revealed the pre.sence of an avifauna with close Guianan ' Museum of Natural Science. 1 19 F-oster Hall. I.ou- isiana State Univ., Baton Rouge, I. A 7()S()3. USA. * Inst, de Investigaciones de la Amazonia F’eruana (IIAP), Av. Quinones Km. 2.5, Iquitos. Peru. ’Corresponding author; e-mail: ictinia@earthlink.net affinities extending westward from the Iquitos area into eastern Ecuador (Alvarez and Whit- ney 2003). In the early stages of recognizing this pattern, we focused fieldwork on searches for additional species we predicted to have a high likelihood of occurrence in the various white-sand forest types in this region. Among these was Polioptila i>iPuincnsis (Guianan Gnatcatcher), a poorly known canopy insec- tivore represented by about 30 specimens in the world. Its nearest documented point of oc- currence lay some 800 km tiistant along the upper kio Negro in Brazil near Sao Gabriel da C’achoeira (BMW pcrs. obs.). 114 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 On 9 September 1997, JAA found what ap- peared to be Polioptila guianensis in tall, white-sand forest in the proposed Allpahuayo- Mishana Reserve outside Iquitos on the road to Nauta. He noted, however, that the birds’ songs differed distinctly from BMW’s record- ings from Brazil. In subsequent years, we ob- tained three specimens and a good sample of recordings of the songs and calls of this gnat- catcher, which appears to have a highly re- stricted distribution, even within the reserve. After comparing our specimens and sound re- cordings with those of all Neotropical gnat- catcher species, especially P. guianensis from diverse points in its distribution, we are con- vinced that the Iquitos-area birds are most closely related to P. guianensis, and would best be described as a new species, which we propose to name: Polioptila clementsi sp. nov. Iquitos Gnatcatcher Perlita de Iquitos Holotype. — Museo de Historia Natural de la Universidad Nacional Mayor de San Marcos (MUSM), Lima, Peru, No. 21113; male (skull unossified) from the Zona Reservada Allpa- huayo-Mishana, 03°55'S, 73° 29' W, south bank of Rio Nanay, approximately 25 km wsw of Iquitos, Department of Loreto, Peru; 150 m elevation; 15 December 1998; collected by JAA. Voice specimen of an accompanying in- dividual is archived at the Macaulay Library of Natural Sounds (MLNS), Cornell Labora- tory of Ornithology, Ithaca, New York; LNS 120444. A sample of liver tissue was pre- served (Alvarez No. 1.12.98) and will be ac- cessioned at the Louisiana State University Museum of Natural Science (LSUMZ) once it is legally exported from Peru. Diagnosis of Polioptila clementsi sp. nov. — A typical member of Polioptila {sensu Ridg- way 1904:710-711), including a thin black bill and graduated tail, with narrow rectrices bearing conspicuous white on the outer three pairs but none on the three central pairs. The following pertains only to males, as we have no specimens of female P. clementsi. Readily distinguished from all congeners except P. guianensis, from which it differs by its sig- nificantly longer bill (mean 12.1 versus 11.4 mm; culmen from base at skull). On a taxon- by-taxon basis, differs from P. g. guianensis by uniformly gray throat and breast (instead of throat conspicuously paler than breast) and presence of black bases on outer and penul- timate pairs of rectrices, with third pair mostly black (instead of three outer pairs entirely, or almost entirely, white); from P. g. facilis by presence of a conspicuous, broken white eye- ring (lacking in P. g. facilis) and greater extent of white on outer rectrices (approximately basal 1/3- 1/2 black in P. g. facilis)’, from P. g. paraensis by generally darker and more bluish-gray plumage, and greater extent of white on outer rectrices (approximately basal 1/3- 1/2 black in P. g. paraensis). Readily dis- tinguished from P. schistaceigula, the pur- ported closest relative of P. guianensis (Zim- mer 1942), by much paler plumage overall and somewhat longer tail with extensive white (rectrices essentially all black in male P. schistaceigula). Males of all other species of Polioptila have discrete areas of black on the head (ranging from streaks to extensive caps) in definitive alternate plumage, among other differences. Diagnosis of voice. — Loudsong structurally similar to, but immediately distinguished from, all forms of P. guianensis by presence of sharp, “inverted chevron-shaped” intro- ductory notes (virtually always three of these) delivered slowly enough to be counted in the field, followed by a series of evenly spaced notes delivered at a faster pace than by any of the taxa of P. guianensis. The loudsong of P. schistaceigula is a variable set of notes lack- ing coherent, repetitive structure in series, and is thus very different; other species of Neo- tropical gnatcatchers are widely and variably divergent in both songs and calls. Distribution. — Known only from tall, Car- aipa-dominated varillal forest (see Habitat and behavior section below) at the type locality (the Reserva Nacional Allpahuayo-Mishana) just west of Iquitos, Department of Loreto, Peru. Description of holotype. — See color frontis- piece. Capitalized color designations (corre- sponding number in parentheses) from Smithe (1975). Rictal bristles present, inconspicuous. Upperparts from base of bill to uppertail co- verts, sides of head, and upperwing coverts essentially uniform and closest to Dark Neu- tral Gray (83), in some lights appearing slight- ly more bluish, toward Plumbeous (78). Head Whitney and Alvarez • NEW POLIOPTILA FROM AMAZONIAN PERU 115 lacking discrete areas of black or white except for a narrow, white eye-ring, slightly broken at front and back edges. Throat and breast, including some posterior extension to sides, slightly paler than upperparts (lightest at the lower breast/upper belly). Medium to Light Neutral Gray (84-85). Belly and undertail co- verts white. Primaries and secondaries closest to Blackish Neutral Gray (82), outer vanes of primaries hnely edged with same gray as up- perparts, inner vanes narrowly edged whitish. Alula and smaller, overlying feather blackish with thin whitish margin on outer vane; pri- mary coverts same blackish but lacking whit- ish margins. Underwing coverts white, the tiny coverts at base of outer primaries and at bend of wing with dark gray centers and whit- ish tips. Tail full (12 complete rectrices) and unabraded, distinctly graduated. Three inner pairs entirely blackish. Black/white pattern on No. 4 and No. 5 differs on left and right sides of the bird, the right side having somewhat more white, especially on the outer vanes. Rectrix No. 4 mostly blackish with white tip (about 5 mm on inner vanes, to about 10 mm on outer vanes); No. 5 mostly white with ap- proximately basal 1/4- 1/3 blackish, on the in- ner vane extending posteriorly from the rachis to the feather margin in a diagonal strip to invade the white region to within about 15 mm of the tip on the right feather and to with- in 12 mm of the tip on the left feather. Outer rectrices (pair No. 6) white with about basal 1/5 of outer vane blackish, basal 1/3 of inner vane blackish and showing same diagonal, posterior extension described for No. 5 only to a lesser degree. Rectrices show same pat- tern on ventral and dorsal surfaces except that No. 4 appears wholly blackish (like the two central pairs, no white tip visible) when viewed from above. Soft parts in life: iris brown, maxilla black with paler commisure, mandible grayish-horn, legs and feet bluish- gray, soles of feet whitish. MUSM 21 I 13 was selected for the holotype because it is in the best condition of the three available speci- mens, and has a complete and fully grown tail. Its cranium was clear and unossified; thus, it may be a juvenile. Measurentents of holotype. — Wing (chord) 45.4 mm, tail 45.8 mm, culmcn from base (at skull) 12.7 mm, bill width at anterior edge of nares 2.3 mm, tarsus 15.3 mm, mass 6.0 g. Specimens examined. — Only specimens that were measured are listed. Specimens of all other Polioptila species in South America were compared superficially. The sample be- low was restricted to P. guianensis and P. schistaceigula, the presumed closest relatives of P. clementsi. Some standard measurements of these specimens, with sample sizes, are pre- sented in Table 1. Polioptila clementsi sp. nov.: Peru: Loreto, Allpahuayo-Mishana area, three males (MUSM 21111, 21112, 21113). Polioptila guianensis guianensis (eight males, four females): French Guiana: Tama- noir, Mana River, two males (Carnegie Mu- seum of Natural History [CM] 61912, 61923, paratypes); Oyapock, Pied Saut, three males, one female (CM 64921, 65782, 65783; Amer- ican Museum of Natural History [AMNH] 233949, paratypes). Suriname: Maroni Dis- trict, Negerkreek, one female (AMNH 461499). Guyana: Potaro Landing, one female (AMNH 126034); Iwokrama Forest Reserve, one male, one female (Academy of Natural Sciences [ANSP] 188049, 188050). Brazil: Amazonas, north of Manaus, two males (Mu- seu Paraense Emilio Goeldi [MPEG] 53260, 53261). Polioptila guianensis facilis (five males, one female): Venezuela: Amazonas, Solano, one male (AMNH 433542, holotype); Mt. Duida, Rio Pescado, one male (AMNH 275037, paratype). Brazil: Amazonas, Mt. Cu- rycuryari, one female (AMNH 31 1254, para- type); Parque Nacional do Jaii, two males (MPEG 50678, 50679); Roraima, Colonia do Apiati, one male (Field Museum of Natural History [FMNH] 344215). Polioptila guianensis paracusis (two males, three females, one sex unknown): Brazil: Para, Muniefpio Capim, one male, one female (Mu- seu de Zoologia da Universidadc de Sao Paulo IMZUSPI 45687, 45693); Caxiricatuba, one male, one female (AMNH 287648, 287649): Amazonas, Borba, Rio Mapia Grande, one sex unknown (MPEXi 53263); Rondonia, Cach- ocira Nazarc, one female (E'MNH 344216). Polioptila schistaceigula (one male, three females): Colombia: Cauca, two females (AMNH 107540, 133935). Ecuador: Esmer- aldas. Cachabi, one male (AMNH 502979. ho- lotypc); Pichincha. one female (I.Sl’MZ 162122). 116 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 TABLE 1. Some standard measurements of Polioptila clementsi sp. nov., P. gidanensis (three subspecies), and P. schistaceigula from northern South America. Values are means (range, n). Taxon Bill width (min)“ Culmen (mm)^ Wing chord (mm)‘^ Tail (mm) Body mass (g) P. clementsi Male 2.4 (2.3-2.S, 3) 12.1 (11.7-12.7, 3) 44.3 (43.5-45.4, 3) 46.6 (45.8-47.6, 3) 5.6 (5. 1-6.0, 3) P. g. guianensis Male 2.3 (2.2-2.S, 8) 11.5 (10.9-12.0, 6) 46.6 (44.5-49.0, 8) 46.5 (44.1-48.9, 4) 6.2 (5.4-6.9, 3) Eemale 2.4 (2.3-2.4, 2) 11.4 (11.1-11.6, 3) 46.0 (45.5-46.6, 2) 43.9 (1) 6.0 (1) P. g. facilis Male 2.5 (2.3-2.T, 5) 1 1.4 (11.1-11.7, 5) 45.3 (44.8-45.7, 5) 46.3 (45.2-47.4, 5) 5.9 (5.5-6.5, 3) Eemale — 11.8 (1) 44.2 (1) 46.3 (1) — P. g. paraensis Male 2.5 (1) 12.0 (11.9-12.0, 2) 45.0 (44.5-45.5, 2) 50.3 (48.8-51.8, 2) — Eemale 2.5 (2.3-2.V, 2) 11.4 (10.8-11.9, 3) 45.5 (43.0-49.0, 3) 48.6 (47.2-50.1, 3) 5.8 (1) Sex un- 2.5 (1) 10.8 (1) 43.0 (1) 48.9 (1) 5.9 (1) known P. schistaceigula Male 2.5 (1) 13.7 (1) 46.9 (1) 42.4 (1) — Female 2.5 (2.4-2.5, 3) 12.3 (11.9-12.7, 3) 44.4 (43.7-45.6, 3) 41.6 (38.6-43.4, 3) 6.0 (1) ^ Measured at anterior edge of nares. ^ Measured from base at skull. Both wings usually measured; longer measurement included here. Tape recordings examined. — Sample sizes are number of individuals recorded; 1-4 vo- calizations of each type were measured for each individual (means and ranges for sam- ples are presented in Table 2). Polioptila cle- mentsi sp. nov.: Peru: Loreto, Allpahuayo- Mishana area, 10 loudsong (9 JAA, 1 BMW), 8 calls (7 JAA, 1 BMW). Polioptila guianen- sis guianensis: Brazil: Amazonas, north of Manaus, two loudsong, two calls (all L. Naka). Polioptila guianensis facilis: Brazil: Amazonas, near Sao Gabriel da Cachoeira, seven loudsong (4 BMW, 3 K. J. Zimmer), four calls (K. J. Zimmer). Polioptila guianen- sis paraensis: Brazil: Para, Caxiuana National Forest, six loudsong (5 BMW, 1 C. A. Mar- antz); Serra dos Carajas, two loudsong, one call (all BMW); Novo Progresso, one loud- song (J. F. Pacheco); Vila Braga, one loudsong (BMW); Jacareacanga, one loudsong (BMW); Amazonas, Rio Sucunduri, one loudsong (BMW); Mato Grosso, Comodoro, one loud- song, four calls (A. Whittaker). Two of the P. clementsi were collected subsequent to tape recording (the third specimen was in the com- pany of a bird that was tape recorded); none of the P. guianensis was collected. Biochemical specimens. — Tissues were saved in DMSO (dimethylsulfoxide) buffer solution (to be deposited at LSUMZ once it is TABLE 2. Some measurements of Polioptila clementsi and P. guianensis (three subspecies) loudsongs from northern South America. Values are means (range; no. of vocalizations, no. of individuals).^ Pace without Taxon Pace of first three notes first three notes APF*’ P. clementsi 0.14 (0.13-0.16; 33, 10) 0.07 (0.06-0.07; 33, 10) 1.98 (1.75-2.30; 33, 10) P. g. guianensis'^ 0.12 (0.12-0.13; 2, 2) 0.14 (0.13-0.15; 2, 2) 0.47 (0.31-0.63; 2, 2) P. g. facilis'^ 0.08 (0.07-0.10; 20, 6) 0.13 (0.12-0.14; 19, 6) 0.94 (0.52-2.33; 20, 6) P. g. paraensis^ 0.09 (0.07-0.10; 15, 6) 0.11 (0.09-0.12; 15, 6) 0.37 (0.21-0.61; 15, 6) “ Means and ranges reflect combined measures of the number of birds recorded. All measurements taken at peaks of notes. ^ Change in peak frequency from first to last note. Sample from near Manaus, Amazonas, Brazil. Sample includes both banks of upper Rio Negro, Amazonas, Brazil. ^ Sample from Caxiuana National Forest, Para, Brazil. Whitney and Alvarez • NEW POLIOPTILA FROM AMAZONIAN PERU 117 exported from Peru) for all three of the spec- imens of Polioptila clementsi. We know of four tissue samples of other members of the P. guianensis complex (see Specimens ex- amined listed above): ANSP 188050 is tissue number ANSP 8192; ANSP 188049 is tissue number ANSP 8307; and MPEG 53260 and 53261 are tissue numbers LSUMZ B-20230 and B-20266, respectively. Etymology. — We are pleased to name this new species in honor of James E Clements in recognition of his generous and forward- thinking contribution to preserving the All- pahuayo-Mishana National Reserve, and the habitat of Polioptila clementsi in particular. Jim’s influence on the world of birding, pri- marily through his carefully maintained world checklist of birds, has been enormous and has sparked the interest of many birders to travel to remote places in search of rarities like the Iquitos Gnatcatcher. The money generated by the activities of birders has ever-growing im- portance in supporting local economies, and it encourages government authorities to recog- nize the economic value of ecosystem pres- ervation. REMARKS Variation in the type series. — The type se- ries consists of the three male specimens listed above, all of which have essentially unossified skulls and are probably juveniles. One of them (MUSM 21111) was one of four individuals foraging together in a mixed-species flock and was thought to have been giving food-begging calls. Plumage of this specimen and MUSM 21112 closely match the description of the ho- lotype. The holotype and MUSM 21111 were collected in mid-December, and both showed contour molt but no molt in the flight feathers. MUSM 21112, taken in early April, also showed contour molt and had half-grown cen- tral rectrices with the right outer rcctrix barely emergent from its sheath. All specimens show the slight variation in pattern of black and white on the rcctrices described for the holo- type. Some variation in iris color can be surmised from the specimen labels. J'he holotype was “brown,” MUSM 21 I I I was recorded as “grayish-brown,” and MUSM 21 I 12 as “pale brown, almost cream.” Lacking specimens of adults, it is not possible to comment further on variability of this feature or other charac- teristics. Juvenile and other subadult plumages of other Polioptila species are, however, quite similar to adult plumages (these being basic plumages in the cases of species with different alternate plumage; Ridgway 1904, Atwood and Bontrager 2001). This accords well with our sightings from the field. Food-begging birds in the company of singing adults (i.e., the birds feeding them) show no noticeable plumage differences from adults. Further- more, adults appear to show no plumage var- iation through the year, never acquiring any conspicuous areas of black or white (e.g., mask, cap) on the head. Habitat and behavior. — Polioptila clement- si appears to be uncommon or rare (encoun- tered 0-3 times per week, n = —50 observa- tions) in the Allpahuayo-Mishana National Reserve, occurring only in white-sand forest having a variable canopy height of about 15- 30 m, and is most consistently present in what local botanists have defined as varillal alto humedo (tall, humid varillal forest). These physiognomically simple varillal forests were characterized by Whitney and Alvarez (1998) and described in detail by Garcia Villacorta et al. (2003). In varillales, canopy height and species composition and abundance of plants, even major groups of plants such as brome- liads and palms, varies over a small spatial scale in accordance with edaphic conditions and drainage properties (e.g., Poulsen and Tuomisto 1996, Garcia Villacorta et al. 2003). Similarly, presence of P. clementsi is highly patchy and it appears that considerable areas of seemingly suitable habitat contiguous with active territories are not occupied. Since its discovery, careful searches for P. clementsi have been conducted in all forest habitats in northern Loreto by using tape recording play- backs and by observing from the ground with binoculars and telescopes; this has enabled us to define its habitat more specifically than has been possible for most other small, forest- based passerines. We had expected to find P. clementsi along the middle and upper Rio Na- nay. At two places along the upper Nanay, however, we have found Polioptila plnmbea (JVopical Gnatcatcher) accompanying mixed- species flocks in the canopy of varillal habi- tats, occupying the potential ecological space of P. clementsi. Within Allpahuayo-Mishana, 118 THE WILSON BULLETIN Vol. 117, No. 2, June 2005 P. plumbed is restricted to seasonally flooded forest along the margins of the Rio Nanay. Tall trees of Caraipa tereticaiilis and C. iitilis (Clusiaceae) are among the dominant canopy trees in appropriate habitat, and pairs or small family groups of P. clementsi were often seen foraging in these trees (see frontis- piece). Palms (Arecaceae) also occur, includ- ing the widespread Euterpe caatinga and the less common Mauritia aculeata and M. car- ana. Arboreal epiphytes are rare. Understory plant composition is also variable, but is typ- ically dominated by some combination of the ferns Trichomanes martiusii and T. bicorne (Hymenophyllaceae), the herb Rapatea ulei (Rapateaceae), and various species of brome- liads, such as Guzmania lingulata and Neo- regelia sp. (Bromeliaceae). Polioptila clementsi foraged exclusively in the canopy and subcanopy (upper 1/4 of trees) with mixed-species flocks composed primarily of other insectivores and usually including some small frugivores and nectarivores. At- tack maneuvers ranged from gleans and short, stabbing reaches to acrobatic chases of fleeing prey as the birds moved lightly and inces- santly through the terminal portions of live, leafy branches. All leaf surfaces were checked rapidly. The tail was partially cocked, fre- quently flicked laterally, and briefly opened slightly to expose the white outer rectrices. (In all these aspects, the foraging behavior of P. clementsi appears to be typical for the genus.) These irregular movements may startle small, hidden arthropods into revealing their pres- ence and probably help family members main- tain visual contact. The wings were shallowly flicked outward (without opening) almost con- stantly. This tiny motion may effect a state of readiness for instantaneous pursuit of flushed prey items. Stomach contents of MUSM 21112 contained insect fragments and many small white eggs of an arthropod. One indi- vidual that had apparently just bathed was ob- served sunning itself and preening on a limb for more than 5 min. Vocalizations. — We have documented with tape recordings six types of vocalizations from Polioptila clementsi. The loudsong is a distinctly two-parted series of sharp, thin (un- modulated, no harmonics) notes. It begins with three evenly paced (slow enough to be counted in the field) open, “inverted chev- rons” peaking at approximately 8 kHz, and then breaks into a much faster, trilled series of evenly paced, nearly vertical notes at just over 6 kHz (Fig. 1 A). Loudsongs are usually slight- ly less than 2 sec in duration, but may exceed 2.5 sec after tape-recording playback; no other features have been observed to change follow- ing playback of birds’ own songs or songs of other individuals. We analyzed nine loudsong recordings of P. clementsi, most of which con- sisted of 3-20 or more songs. All songs began with the three introductory notes described above; there was no variation in this character. In fact, the loudsong of all individuals was remarkably consistent in all aspects. At least three clearly recorded songs of each individ- ual were extracted and measured using “Ca- nary” 1.2.4 of the Bioacoustics Program of the Cornell Laboratory of Ornithology (Itha- ca, New York). Spectrograms were produced using the default settings and 75% overlap. Although any number of other features could have been quantified, we selected three inde- pendent characters for critical measurement: pace (see below) of the first three notes, pace of the rest of the notes (all those after the first three), and change in peak frequency (APF) from the first to the last note. Measurements for the three songs from each individual were then averaged to obtain a value that reflected some attempt to control for intra-individual variation (Table 2). All measures were made at the scales shown in Figure 1 and at the peak frequency of notes, as this was the only un- ambiguous point (i.e., permitting easily repro- ducible results) on these highly vertically ori- ented spectrogram traces. The “inverted chev- rons” of the first three notes were measured this way, as well, to permit appropriate com- parison with the first three notes in the songs of some other taxa in the complex. Thus, pace more effectively quantified the time intervals between notes than the duration of the section measured, because, in the case of the first three notes especially, the measurement point hit not the left/right edges of the open chev- rons, but the highest point (peak) of the note. Pace of the first three notes in the loudsong was 0.14 sec (range = 0.13-0.16 sec). Pace of the remaining notes was 0.07 sec (range = 0.06-0.07 sec); APF was 1.98 kHz (range = 1.75-2.30 kHz). Both parts of the loudsong Whitney and Alvarez • NEW POLIOPTILA FROM AMAZONIAN PERU 119 1.5 \ V n 'i \ Time (sec) FIG. 1 . Sound spectrograms of vocalizations of Polioptila clementsi. Recordings are by JAA except as noted. The frequency scale is uniform for all spectrograms, but note that some do not show the area below 4.0 kHz. (A) Typical loudsong showing three distinct introductory notes; all recorded songs were closely similar to this (Table 2); (B) quiet, single-note call with a harmonic heard only a few times; (C) typical multi-note call with emphasis on the introductory note and pronounced harmonics; (D) flight calls, given in doublets (recorded by BMW); (E) irregular series of sharp calls sometimes given while foraging. were characterized by essentially uniform pace and lack of frequency shifts. The second most frequently recorded vo- calization of P. clementsi (n = 3 recordings) was a multi-note call lasting 0. 5-1.0 sec, sounding like a brief, quiet chatter, in which the first note is distinctly louder and longer, and all notes have harmonics (Fig. IB). We have not been able to determine its context. Other vocalizations (represented by only one or two recordings) are a quiet, single-note call having a closed “inverted chevron” shape at about 3 kHz that also has a harmonic (Fig. 1C); a sharp call given in flight that makes a straight, nearly vertical trace from about 5.5 to 9 kHz (Fig. ID); sharp (bent vertical trace) calls structurally similar to notes in the fast section of the loudsong but peaking at about 8 kHz and often given several times in irreg- ular succession while foraging (Fug. IF); and a food-begging call similar to the call shown in E but which features a structurally distinct introductory note ahead of a regularly paced series of sharp notes. One additional vocali- zation was heard once by BMW, but unfor- tunately it could not be recorded. A singing bird in the company of its mate responded to playback of its own song by flying out of a tree above the trail (about 12 m above ground) and then tightly circling the narrow canopy of the tree one complete turn (360°) while rap- idly pumping its tail up and down as it deliv- ered a distinctively cadenced sound — some- thing like chik-CHEE-dee, chik-CHEE-dee, chik-CHEE-dee, chik-CHEE-de. . . . Such flight displays accompanied by a vocalization quite different from the typical loudsong are occasionally given by many species of oscine passerines (BMW pers. obs.). fheir function remains obscure, but in this case the display and vocalization clearly resulted from agita- 120 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 tion at the presence of a perceived conspecific male intruder. Intrageneric relationships. — Morphological- ly. P. clementsi is rather weakly differentiated from P. guianensis, although it has a longer bill (two-tailed r-test, P = 0.008), and a diagnos- tically different tail pattern from the three named taxa in P. guianensis, among other more subtle characters revealed in taxon-by- taxon comparisons (see Diagnosis, above). The general structure and steady pace and fre- quency of its loudsong, and its multi-note call (Fig. IB), also place Polioptila clementsi firm- ly in the P. gnianensis group. The multi-note call with harmonics given by members of the P. gnianensis complex is unique in the genus (BMW pers. obs.). Thus, Polioptila clementsi is clearly an integral member of the wide- spread P. gnianensis complex (which would be called the P. schistaceignla complex if that species is considered an allospecies; see be- low). Considering the fact that another well- studied pair of sister taxa in the genus, P. me- lannra (Black-tailed Gnatcatcher) and P. cal- ifornica (California Gnatcatcher; Atwood 1988, Atwood and Bontrager 2001), are not as well-differentiated phenotypically in either morphologies or vocalizations as P. clementsi and P. gnianensis, we are satisfied that species status is appropriate for both P. clementsi and for other taxa currently recognized as subspe- cies, as discussed below. REVISION OF THE POLIOPTILA GUIANENSIS COMPLEX Morphology. — Zimmer (1942) considered Polioptila gnianensis closely related to, and possibly conspecific with, trans-Andean P. schistaceignla, and it is primarily for this rea- son that we have included mention of the lat- ter species in this paper. Neither Zimmer (1942) nor Mayr and Paynter ( 1964, following Zimmer) provided any justification for this opinion; the relationship was deemed “uncer- tain” by the American Ornithologists’ Union (1998:494). We do not consider P. schistacei- gnla an allospecies in the P. gnianensis com- plex. although we suspect that it is sister to the group. If it is a close relative, it is clear that P. schistaceignla has differentiated strongly, both morphologically and vocally, from the much more widely distributed cis- Andean radiation comprising the three named taxa in P. gnianensis, and now P. clementsi. Differentiation appears to be much less ad- vanced east of the Andes, where several al- lopatric forms share closely similar morphol- ogy (Table 1) and a loudsong template of a rapid series of nearly evenly spaced notes last- ing about 1.5-2 sec. The paucity of specimens (especially females) and recordings hamper study of the complex. Eurthermore, these small, lightly built birds are difficult to pre- pare as museum skins; on a few specimens it is not possible to be sure that certain features, particularly the presence and extent of white feathering around the eyes and lores, can be seen sufficiently well to allow meaningful comparisons. However, it seems reasonable at this point to offer a better estimation of tax- onomic limits than has been attempted to date. Stotz et al. (1997) provided an accurate over- view of some of the characters discussed be- low. Eigure 2 maps the distribution of the Po- lioptila gnianensis complex (nominate gni- anensis, P. g. facilis, and P. g. paraensis), P. clementsi, and P. schistaceignla and shows, we believe, virtually all records for all of the taxa (localities within about 50 km are mapped as a single point following Isler 1997). Tails. — The amount of white and black on the rectrices is slightly variable on all individ- ual birds (i.e., rectrix on one side of the bird shows slightly different extent of white than its counterpart on the other side) and among specimens within taxa; nonetheless, it pro- vides the most salient plumage feature for in- tertaxon comparisons (i.e., this fluctuating asymmetry is not of sufficient magnitude to confound taxon identifications). Nominate gnianensis invariably has the most white, with the outer two rectrices entirely white and rec- trix No. 4 entirely or almost entirely white. None of the 12 specimens examined (both sexes included), which spanned the entire known range of this taxon, has any white on the three inner pairs. Both P. g. facilis and P. g. paraensis have considerably more black on the outer three rectrices than nominate gni- anensis and are similar to each other. One of the facilis males from Jau shows two small blotches of white at the tip of No. 3 on the left feather only, and tiny grayish fringes are present at the tip of No. 3 in other facilis spec- imens. Topotypical specimens of paraensis {n Whitney and Alvarez • NEW POLIOPTILA FROM AMAZONIAN PERU 121 FIG. 2. Distribution of taxa in the Polioptila guianensis complex, and that of P. schistaceigiiki (stars). X marks the type locality of P. clementsr, dots are P. g. guianensis; squares are P. g. facilis; diamonds are P. g. paraensis. Type localities are enlarged symbols. S beside a symbol means we examined a specimen from that locality; R means we have a recording; U means there is a specimen reported in the literature that we have not examined; and V marks undocumented sight records. The single question mark (?) on the upper Rio Tapajos/ Teles Pires marks two or three sight records from opposite sides of the river in the Alta Floresta area, where heldwork has been extensive but where we still lack confirmation (no .specimen, recording, or photo) of occur- rence; we hesitate to map these particular records until documentation becomes available. The distance between P. clementsi and the nearest known population of P. guianensis, on the upper Rio Negro in Brazil, is approxi- mately 800 km. = 2) have a small white tip (~3 mm) on rec- trix No. 4 with no white on the three inner feathers; all other specimens (/? = 4) show a larger white tip (~6 mm) on No. 4, and a very small (~2 mm) white tip on No. 3. As noted by Zimmer (1042), /^ g. paracusis tends to have the longest tail of all (Table 1). Other plitmagc features. — The throat of all P. g. guianensis specimens is slightly to mark- edly more whitish than the breast, although females show less contrast and are more whit- ish overall (this seems to be true for all taxa). Males show a narrow but fairly conspicuous, often slightly broken, white eye-ring; females seem to have a more conspicuous eye-ring and narrow white superciliary, as well. Of the five males from French Guiana, one (CM 61912) has an obvious white supra-loral streak ex- tending to the nares, three shou some indi- cation of it (as does the single male from Guy- ana), and one (CM 61923) has none at all. Among all males of other taxa, none shows any sign of the supra-loral streak. Phe gray of the plumage of P. g. facilis is of about the same lone as that of nominate guianensis (Zimmer 1942 considered it a little paler), but the throat of males is nearly concok)r with the breast rather than distinctly more whitish, and 122 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 fcicilis has no, or only a hint, of white around the eye. Plumage of facili.s specimens from the entire range of points mapped in Fig. 2, encompassing both banks of the upper Rio Negro, shows no appreciable variation, but a larger sample is desirable. Polioptila g. par- aensis is the palest form overall. Like P. g. fcicilis, and unlike nominate giiicinensis, it shows little or no throat-breast contrast. A male and a female from near the type locality show almost no eye-ring; all others show a weak and broken white eye-ring intermediate in contrast relative to those of P. g. guianensis and P. g. facilis. Soft-part colors. — Iris color was recorded for eight specimens of P. guianensis. All but two of them were recorded as brown or gray- ish-brown. The adult (skull 100% ossified) fe- male from Rondonia had a “pale gray” iris. Two of the specimens of P. g. facilis are note- worthy. FMNH 344215 (male with 90% os- sified skull) from Roraima, a short distance west of the Rio Branco, had a “pale yellow orange” iris (label data; Stotz et al. 1997 cited it as “bright orange-yellow”); this was the only brightly colored iris of any specimen in the complex. MPEG 50678 (male with 100% ossified skull) from west of the middle Rio Negro in Jau National Park had a “brown” iris. Determination of whether these quite dif- ferent eye colors from localities on opposite banks of the Rio Negro have any geographic restriction awaits further collection of speci- mens and perhaps careful observations in the field. No differences in the coloration of bills, legs, or feet were noted among taxa, but data from collectors/preparators are generally lack- ing. Vocalizations. — Figure 3 shows loudsong spectrograms of the members of the Polioptila guianensis complex. Measurements of the characters described for vocalizations of Po- lioptila clementsi (above) are summarized by taxon in Table 2. We have illustrated ex- amples from fairly near type localities (mapped in Fig. 2) for P. g. facilis and P. g. paraensis, but unfortunately we have no re- cordings of P. g. guianensis from near the type locality in French Guiana. However, our examples from near Manaus, Amazonas, Bra- zil come from the same localities as speci- mens that are phenotypically almost identical to the several paratypes of nominate guianen- sis. The loudsong of Polioptila g. guianensis (Fig. 3A; n = 2) appears to be a simple, even- ly paced repetition of a thin, sharp “inverted chevron” note with greater intensity on the left side of the note. It is also quite level in frequency, with a APF of 0.47 kHz. The loud- song of P. g. facilis from the left (north) bank of the upper Rio Negro (Fig. 3B; /? = 4) has the highest introductory note of any of the taxa (~9 kHz); a slightly lower second note is often coupled with it, followed by the rest of the series at a steady, slower pace slightly above 8 kHz. Notes in the series are “inverted U” traces. The song of one individual was more evenly paced throughout (no coupling of the first two notes) with the series at about 7 kHz; APF north of the Rio Negro was 0.94 kHz including this individual. Directly across the upper Negro, the first note of the song peaks at about 7 kHz and APF is 0.64 kHz {n = 2); pace and note shape appear to be es- sentially the same as they are in songs of birds from the north bank of the river. The “invert- ed U” notes of facilis have highest amplitude at the peak, with nearly equal intensity on the arms; this, together with the rounded shape of the peak of notes in the series, gives the song a slightly softer quality than those of other taxa. Measures for the loudsong of P. g. paraen- sis (Table 2) were restricted to the sample from the Caxiuana National Forest west of Belem because this is fairly near the type lo- cality and we had several recordings from there. It is a simple, steadily paced repetition of a sharp, “inverted chevron” note having greatest intensity on the right side (Fig. 3C). Peak frequency range is nearly flat, with APF of only 0.37 kHz. Discussion. — All three named taxa in Po- lioptila guianensis differ diagnostically from P. clementsi and from each other in both plumage and voice. Published subspecies di- visions based entirely on morphological traits accord well with differences in vocalizations, and levels of phenotypic differentiation in the complex seem approximately equivalent. In spite of small sample sizes for most members of the group, we are confident that individual specimens and tape recordings of loudsongs can be assigned unequivocally to taxon as cur- Whitney and Alvarez • NEW POLIOPTILA FROM AMAZONIAN PERU 123 Time (sec) FIG. 3. Sound spectrograms of loudsongs of members of the Polioptila guianensis complex. The frequency scale is uniform for all spectrograms, but the area below 4.0 kHz is omitted. (A) P. g. guianensis from near Manaus, Amazonas, Brazil; intensity is greatest on the left side of the “inverted chevron” notes; recorded by L. Naka; (B) P. g. facilis from 17 km north Sao Gabriel da Cachoeira, left (north) bank of the upper Rio Negro, Amazonas, Brazil, ~300 km south of the type locality; the “inverted U” notes oi facilis are distinctive; recorded by K. J. Zimmer; (C) P. g. paraensis from the Caxiuana National Forest, —400 km west of the type locality; recorded by BMW (D) P. clenientsi from the type locality (same spectrogram as Fig. lA); recorded by JAA. rently defined. Vocalizations may represent a more reliable character set than morphology for distinguishing some forms. Atwood and Bontrager (2001 ) reached the same conclusion with regard to identification of Polioptila lue- Icmura and P. californica, two narrowly syn- topic sister-species (Zink and Blackwell 1998). As an oscine passerine assemblage, however, the question of whether vocaliza- tions can be expected to reflect evolutionary divergence, as they have proven to do quite accurately in the cases of some suboscine pas- serine groups (Arctander and Fjeldsa 1994, Cohn-Haft 2000), should be addressed. It has been shown for several species of os- cine passerines that some elements of songs are learned during some “critical period” (ap- parently often the nestling stage), which, sub- ject to a variety of circumstances, can lead to geographically restricted dialects. In a study of the Rufous-col hired Sparrow [Zonotrichia capcnsis) in northern Argentina, Lougheed et al. (1993) reported that mtDNA variation ob- served along a 50-km transect crossing three well-documented song dialects was overlain by, but unrelated to, these dialects. 7'hey went on to suggest that “cultural evolution result- ing in dialects does not affect dispersal or mating patterns, and, thus, does not promote genetic differentiation.” Looking at a greatly expanded area of coverage, however, they concluded that “hyperdiverse mtDNA and al- THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 124 lozyme characters together provide prelimi- nary evidence of large-scale patterns corre- sponding to subspecies divisions. ...” Thus, macrogeographic sampling of vocalizations of a widespread oscine passerine seems an ap- propriate starting point for evaluating the tax- onomic ranking of named taxa (i.e., morpho- logically distinct forms) as well as identifying unnamed populations. The meager sample of recordings of P. g. guianensis was limited to the Manaus area, so it was not possible to investigate whether any geographic structure in vocalizations might be present within its range. Our recordings of P. g. facilis, from opposite banks of the upper Rio Negro, show quite similar pace and note shapes, but somewhat different APT owing primarily to the higher, sharper introductory note given by birds on the left (north) bank. The upper Negro may separate different dia- lects or, more likely, we believe it represents a maintenance barrier for genetic divergence as it does for some Hemitriccus flycatchers (Cohn-Haft 2000) and other groups of birds. The only taxon for which we have samples from a wide area is P. g. paraensis, which shows little variation in the region between the Tapajos and Tocantins rivers. It is important to note that loudsongs of members of the P. guianensis complex from localities for which we have several record- ings (P. clementsi near Iquitos; P. g. paraensis at Caxiuana) show remarkable consistency in all characters measured, as well as important qualitative attributes, such as note shape and tonality. In fact, ranges of measures (Table 2) are quite similar to those reported for larger samples of some thamnophilid antbirds (Whit- ney and Alvarez 1998; Isler et al. 1999, 2002). We expect that other taxa in the complex will prove to show similar, low levels of variability in their vocalizations. In sum, the evidence points to a lack of any learning element in the development of songs and calls in the P. gui- anensis complex. Similarly, Atwood and Bon- trager (2001) concluded that learning is likely not a factor in vocal development in P. cali- f arnica. The potential to learn some elements of song does not exclude the possibility, or even probability, that vocal templates of oscines are a phenotypic expression of genetic determi- nation and are thus potentially informative in taxonomic and systematic study. Capacity for song learning and the actual extent of learning of vocalizations have not been studied for any forest-based Neotropical oscine passerine. Ex- tensive field work in most areas of the Ama- zon basin and other primarily forested habitats in South America indicates to us that, like members of the Polioptila guianensis com- plex, some oscine passerines as unrelated as Microcerculus wrens and Hylophilus greenlets have maintained a high degree of uniformity of vocalizations across broad geographic fronts, yet show marked geographic differen- tiation, in accordance with patterns observed for numerous suboscine species (BMW pers. obs.). Another widespread complex in the ge- nus Polioptila that shows significant geo- graphically structured variation in morpholo- gy, vocalizations, and habitat specificity is the P. plumbea group (BMW pers. obs.), but it has not yet been studied. Taxonomic conclusions. — Until we have sufficient data to offer a different, or more complete, picture of speciation in the Poliop- tila guianensis complex, and in consideration of the similar or lesser levels of phenotypic differentiation documented for some other sis- ter-species complexes in the genus, we pro- pose that Polioptila clementsi and the three subspecies of Polioptila guianensis henceforth be recognized at the species level (this com- plex probably sister to P. schistaceigula) with the following names: Polioptila guianensis, Guianan Gnatcatcher Polioptila facilis, Rio Negro Gnatcatcher Polioptila paraensis, Para Gnatcatcher Polioptila clementsi, Iquitos Gnatcatcher Both P. guianensis and P. facilis are known from the left (east) side of the Rio Negro, and the latter has been collected (one specimen) in Roraima a short distance west of the Rio Branco. We suspect that the Rio Branco sep- arates these two forms; this region, however, remains among the most undersampled areas of Amazonia. Similarly, the vast region be- tween the Manaus area and the three Guianas (Fig. 2) has seen almost no collecting; we ex- pect that all forested areas in that hiatus are occupied by P. guianensis. In this study, all specimens from south of the Amazon River are provisionally called P. g. paraensis. Al- though linked by pale coloration and long Whitney and Alvarez • NEW POLIOPTILA FROM AMAZONIAN PERU 125 tails, they are few {n = 6) and widely scat- tered (Fig. 2). For example, we have little in- formation from west of the Rio Tapajos and only two sight records from anywhere west of the Rio Madeira (one of these reported by Per- es and Whittaker 1991). We predict, however, that an undetected population inhabits most of the region west of the Madeira north of about T S, west to Peru; it should be sought espe- cially in forests growing on white sand and extensively weathered clays (both patchily distributed terra firme habitats). There are many additional gaps on the map, and clearly much more work will be required to gain an accurate understanding of how members of the P. guianensis complex are distributed. Collection of additional specimens and tape recordings from poorly known areas of the distribution of the Polioptila guianensis com- plex may soon confirm the existence of one or more additional, unnamed populations of these obscure. Neotropical forest gnatcatchers. As a final thought, in the only study to date that addresses the way in which molecular evolution informs species relationships within the genus Polioptila, Zink and Blackwell (1998) reported an mtDNA sequence diver- gence of about 4% between the sister-species P. nielanura and P. californica. We expect that the level of sequence divergence among members of the P. guianensis complex could vary considerably from this owing to a variety of factors such as much larger population siz- es of most taxa, evolution in far more stable environments and, probably, lower reproduc- tive rates and increased longevity. Thus, a lev- el of divergence deemed appropriate for rec- ognition of taxa at the species level in one region of the world may not necessarily find its equivalent for obviously related taxa that have evolved in radically different environ- ments. Molecular analysis of the widespread Polioptila guianensis group may have the po- tential to illuminate speciation patterns appli- cable to a variety of forest-based Amazonian birds. CONSERVATION The discovery of I lerpsiloclwius gentryi and other species (not only birds, but other vertebrates and plants) new to science or new to Peru, led the Instituto dc Invesligaciones de la Amazonia Peruana (MAP) to propose to the Instituto Nacional de Recursos Naturales (IN- RENA) the creation of a reserve to protect the rare white-sand habitats near Iquitos. On 16 January 2004, the status of Zona Reservada Allpahuayo-Mishana (established 4 March 1999) was elevated to the Reserva Nacional Allpahuayo-Mishana, encompassing 58,070 ha and protecting the greatest known concen- tration of white-sand habitats in the Peruvian Amazon. The entire known range of Poliop- tila clementsi is officially protected. However, its presence is confirmed from only about six localities in an area of no more than 2,000 ha because appropriate varillal forest is highly patchy in distribution. We estimate that a max- imum of 50 pairs survive in the reserve. Over the past 3 decades, a high percentage of the once-extensive varillal habitats in and surrounding the known distribution of Poliop- tila clementsi has been fragmented or de- stroyed as the Peruvian government encour- aged colonization of the area near Iquitos. Ag- ricultural initiatives have largely failed on these nutrient-deficient, quartzitic soils, yet persistent colonists have cleared the land, sell- ing the long, straight trunks of varillal trees for construction, firewood, and making char- coal, which, within a national reserve, is pro- hibited by Peruvian law (Fig. 4). Today, the only known population of Polioptila clementsi is fragmented into three parcels separated pri- marily by deforested terrain. Titled landhold- ers who live within the reserve area take a daily toll on the habitat; destruction is espe- cially accelerated near the paved highway linking Iquitos with the town of Nauta. In mid-2()04, the municipality of San Juan (on the west edge of Iquitos) rapidly opened a clandestine road, ostensibly to “promote tour- ism,” along the northern edge of the reserve in an area occupied by several pairs of P. cle- mentsi-, this is sure to result in significantly increased habitat destruction in this heretofore pristine area. Fragile and highly \ulnerable climax varillal forests may never properly re- generate from fragmentation because they grow on such nutrient-poor soils. In fact, the place in the reserve in which the specilic hab- itat of Polioptila clementsi receives the best protection is the property of the Instituto de Investigacidn e Extension Agraria near Km 25 (Id Dorado), where the species was discov- 126 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 EIG. 4. Destruction of the extensive varillal forest, prime habitat of Polioptila clementsi, at Nueva Esperanza in the Reserva Nacional Allpahuayo-Mishana near Iquitos, Loreto. Peru. The long, straight trunks of the dom- inant trees in this habitat, such as Caraipa tereticaiilis, are easily cut for construction, firewood, and making charcoal. These ancient and slow-growing forests occur on especially nutrient-poor, quartzitic soils, and may never be able to regenerate. Photo by JAA. September 1998. ered. Illegal extraction of timber continues even there. Considering its very small, habitat-special- ized world population, the great reduction of appropriate habitat in the recent past, and the continuing destruction of existing habitat, we recommend that Polioptila clementsi be clas- sified as Critically Endangered. We are opti- mistic about its preservation within the Re- serva Nacional Allpahuayo-Mishana, as much-needed funding is now being channeled directly to the preservation effort administered by IIAP in Iquitos. J. D. Alvan, an enthusi- astic and highly skilled young ornithologist, has been hired to carry out field research on Polioptila clementsi and to initiate local en- vironmental education programs in the Iquitos area. Park guards will receive dependable sal- aries; boats and motors will be provided to, and maintained for, cooperative communities along the Rio Nanay; fuel will be purchased; and goods will be distributed. These simple but critically important as- pects of the reserve’s preservation have been made possible by the generous monetary con- tribution of James F. Clements. The challenge will be to maintain funding levels far into the future. Threats to the habitat are increasing, just as every year brings more exciting dis- coveries of plants, insects, amphibians, and other organisms new to science from the white-sand forests of Allpahuayo-Mishana and the Rio Nanay. The attractive Spanish name “Perlita de Iquitos” (Little Pearl of Iquitos) has inspired Mayor Juan Carlos Del Aguila Cardenas and the Provincial Municipality of Maynas council to adopt the gnatcatcher as the official bird of the city. La Perlita de Iquitos will be used in educational and promotional programs as a symbol of the city’s commitment to the bird’s conservation and protection of its fragile hab- itat and the surrounding region. Whitney and Alvarez * NEW POLIOPTILA FROM AMAZONIAN PERU 127 ACKNOWLEDGMENTS JAA is grateful to Flora and Fauna International — 100% Fund (Cambridge, UK) and Bergstrom Awards of the Association of Field Ornithologists (Houston, USA), both of which supported field research in 1998 and 1999. Idea Wild (USA) generously donated mist nets. The Direccion General de Areas Naturales Pro- tegidas y Fauna Silvestre — INRENA provided neces- sary permits for study and specimen collection in the Zona Reservada Allpahuayo-Mishana. We appreciate the assistance of R. Panza, M. LeCroy, P. Sweet, C. Blake, D. Willard, S. J. Hackett, J. M. Bates, L. Joseph, N. Rice, J. V. Remsen, and S. Cardiff for loaning spec- imens. I. Franke was especially helpful with our work at MUSM. We are grateful to the recordists C. A. Mar- antz, L. Naka, J. F. Pacheco, A. Whittaker, and K. J. Zimmer for sending us copies of their recordings of P. guianensis, and to C. Bauer for help with copying some of BMW’s recordings. A. Whittaker also helped JAA collect one of the P. clementsi specimens. We thank J. C. Ruiz for identifying many plant specimens. M. L. Isler kindly prepared the map for Figure 2. J. V. Remsen made helpful editorial changes and provided a sounding board for some of the discussion on taxo- nomic revision. D. F. Stotz and two anonymous re- viewers provided insightful suggestions for improving the manuscript. BMW is grateful to Field Guides, Inc. of Austin, Texas, which partially supported fieldwork, and to the many tour co-leaders and participants who have helped him make tape recordings and other gnat- catcher observations in South America. We thank J. Icomena and E. Aquituari, dedicated and helpful park guards of the Allpahuayo-Mishana Reserve. Finally, we are grateful to L. McQueen for his excellent por- trayal of the Iquitos Gnatcatcher in habitat, which is the frontispiece for this issue. LITERATURE CITED Alvarez, J. A. and B. M. Whitney. 2003. Eight new bird species for Peru and other distributional re- cords from white-sand forests of the northern Pe- ruvian Amazon, with implications for biogeogra- phy of northern South America. Condor 105:552- 566. American Ornithologists’ Union. 1998. Check-list of North American birds, 7th ed. American Or- nithologists’ Union, Washington. D.C. Arctander, P. and j. Fjeldsa. 1994. Andean tapaculos of the genus Scytalopu.s (Aves, Rhinocryptidae): a study of speciation using DNA sequence data. Pages 205-225 in Conservation genetics (V. Foes- cheke, J. Tomiuk, and S. K. Jain, Fds.). Birkhiiii- ser Verlag, Basel, Switzerland. Atwood, J. L. 1988. Speciation and geographic vari- ation in Black-tailed Gnatcatchers. Ornithological Monographs 42:1 74. Arw(X)i), J. L. and I). R. Bos tRAOi.R. 2(K)1. ('alifornia Gnatcatcher {Polio/uila californica). I he Birds of North America, no. 574. Cohn-Hait, M. 2000. A case stutly in Amazonian bio- geography: vocal and DNA-sequence variation in Hemitriccus flycatchers. Ph.D. dissertation, Loui- siana State University, Baton Rouge. Garcia Villacorta, R., M. Ahuite Reategui, and M. Olortegui Zumaeta. 2003. Clasificacion de bosques sobre arena blanca de la Zona Reservada Allpahuayo-Mishana. Folia Amazonica 14:17-33. Isler, M. L. 1997. A sector-based ornithological geo- graphic information system for the Neotropics. Ornithological Monographs 48:345-354. Isler, M. L., J. Alvarez A., P. R. Isler, and B. M. Whitney. 2002. A new species of Percnostola antbird (Passeriformes: Thamnophilidae) from Amazonian Peru, and an analysis of species limits within Percnostola riififrons. Wilson Bulletin 1 13: 164-176. Isler, M. L., P. R. Isler, and B. M. Whitney. 1999. Species limits in antbirds (Passeriformes: Tham- nophilidae): the Myrmotherula surinamensis com- plex. Auk 116:83-96. Lougheed, S. L., P. Handford, and A. J. Baker. 1993. Mitochondrial DNA hyperdiversity and vocal di- alects in a subspecies transition of the Rufous- collared Sparrow. Condor 95:889-895. Mayr, E. and R. a. Paynter, Jr. (Eds.). 1964. Check- list of birds of the world, vol. 10. Museum of Comparative Zoology, Cambridge, Massachusetts. Peres, C. A. and A. Whittaker. 1991. Annotated checklist of the bird species of the upper Rio Uru- cu, Amazonas, Brazil. Bulletin of the Briti.sh Or- nithological Club 111:156-171. Poulsen, a. D. and H. Tuomisto. 1996. Small-scale to continental distribution patterns of Neotropical pteridophytes: the role of edaphic preferences. Pages 551-561 in Pteridology in perspective (J. M. Camus, M. Gibby, and R. J. Johns, Eds.). Roy- al Botanic Gardens, Kew, United Kingdom. Ridgway, R. 1904. The birds of North and Middle America, part 111. Bulletin of the U.S. National Museum, no. 50. Washington, D.C. S.MITHE, F. B. 1975. Naturalist’s color guide. American Museum of Natural History, New York. Stotz, D. F, S. M. Lanyon, T. S. Schulenberg, D. E. Willard, A. T. Peter.son, and J. W. Fitzpatrick. 1997. An avifauna! survey of two tropical forest localities on the middle Rio Jiparana, Rondonia, Brazil. Ornithological Monographs 48:763-78 1 . Whitney, B. M. and J. Alvarez A. 1998. A new Herpsilochmiis antwren (Aves: Thamnophilidae) from northern Amazonian Peru and adjacent Ec- uador: the role of edaphic heterogeneity of terra firme forest. Auk I 15:559-576. ZiMMi R, J. r. 1942. Studies of Peruvian birds, no. 42: the genus Polioptila. American Museum Novita- tes, no. I 168. Zink, K. M. and R. C. Bi ackwlll. 1998. Molecular systematics and biogcography of aridland gnat- catchers (genus Polioptila) and evidence support- ing species status of the C'alifornia Gnatcatcher {Polioptila californica). Molecular Phylogenetics and F\olution 9:26-32. Wilson Bulletin 1 1 7(2): 1 28-1 32, 2005 MOVEMENTS AND HOME RANGES OE MOUNTAIN PLOVERS RAISING BROODS IN THREE COLORADO LANDSCAPES VICTORIA J. DREITZ,'-''’ MICHAEL B. WUNDER,^ AND FRITZ L. KNOPF’ ABSTRACT. — We report movements and home-range sizes of adult Mountain Plovers (Charadrius montanus) with broods on rangeland, agricultural helds, and prairie dog habitats in eastern Colorado. Estimates of home range size (95% fixed kernel) were similar across the three habitats: rangeland (146.1 ha ± 101.5), agricultural helds (131.6 ha ± 74.4), and prairie dog towns (243.3 ha ± 366.3). Our minimum convex polygon estimates of home-range size were comparable to those on rangeland reported by Knopf and Rupert (1996). In addition, movements — dehned as the distance between consecutive locations of adults with broods — were equivalent across habitats. However, our hndings on prairie dog habitat suggest that home-range size for brood rearing may be related to whether the prairie dog habitat is in a complex of towns or in an isolated town. Received 14 November 2003, accepted 4 February 2005. The Mountain Plover {Charadrius montan- us) breeds primarily in the shortgrass prairies of Colorado, Wyoming, and Montana (Graul and Webster 1976) but breeds as far north as Canada and as far south as Mexico (e.g., Graul and Webster 1976, Day 1994, Knopf 1996, Shackford et al. 1999, Manning and White 2001). Colorado is considered the con- tinental stronghold for Mountain Plovers, with over 60% of the population believed to breed there (Kuenning and Kingery 1998). The hab- itat types used by breeding Mountain Plovers within shortgrass prairie may contain areas grazed by native herbivores, such as bison {Bison bison) and black-tailed prairie dogs {Cynomys ludovicianus), or domestic herbi- vores, including cattle and sheep. Mountain Plovers also nest in agricultural fields (Knopf 1996, Knopf and Rupert 1999, Shackford et al. 1999). Landscape-level habitat use by breeding Mountain Plovers may be influenced by the distribution of these habitat types. Landscape-level characteristics, such as the size, distribution, shape, and availability of different habitat types, are important to a spe- ' Colorado State Univ., Colorado Natural Heritage Program, 8002 Campus Delivery, Fort Collins, CO 80523, USA. 2 Colorado State Univ., Dept, of Fishery and Wild- life Biology, Fort Collins, CO 80523, USA. ^ U.S. Geological Survey, Fort Collins Science Cen- ter, 2150-C Centre Ave., Fort Collins, CO 80526, USA. Current address: Colorado Div. of Wildlife, 317 W. Prospect St., Fort Collins, CO 80526, USA. Corresponding author; e-mail: Victoria. Dreitz@state.co. us cies’ population dynamics and regulation (Kareiva 1990, McKelvey et al. 1992, Schmiegelow and Monkkonen 2002, Crozer and Niemi 2003). The distribution of individ- uals among habitats reflects an ability to dis- criminate between habitat types and assess habitat quality (Poysa et al. 2000), and differ- ences in habitat affinity may partially explain the wide range of avian responses to loss of native habitat (Sekercioglu et al. 2002). Land- scape configuration and proximity of resourc- es provided by different habitat types may be critical to the breeding success of Mountain Plovers. Suitable breeding habitats minimize the energetic costs of foraging and reduce ex- posure to predators (Poysa et al. 2000). Here, we report the relationship between movements and home-range sizes of Mountain Plovers during the brood-rearing period within three different habitat types. METHODS Information on brood-rearing activity of Mountain Plovers was collected in eastern Colorado from 2001 to 2003 during other on- going studies in three different habitat types: rangeland, black-tailed prairie dog towns, and agricultural fields. In high-elevation (2,600- 3,500 m) rangeland in Park County, Colorado, the habitat consisted primarily of slimstem muhly {Muhlenbergia filiculmis), and, to a lesser extent, blue grama {Bouteloua gracilis) grazed by domestic bison or cattle (Wunder et al. 2003). Our prairie dog study areas, located in Lincoln and Weld counties in eastern Col- orado (also characterized as rangeland) were dominated by blue grama and buffalograss 128 Dreitz et al. • MOVEMENT AND HOME RANGE OF MOUNTAIN PLOVERS 129 (Buchloe dactyloides). Only 1.94% of eastern I Colorado is occupied by prairie dogs (White I et al. 2005), and, in our study area, we knew I of only one prairie dog complex (>10,000 I ha) — a network of small (mean = 80 ha; range = 1-340 ha), active prairie dog towns within 800 m of each other. The agricultural field habitats were primarily composed of winter wheat strips interspersed with fallow fields in Weld County. The agricultural fields were >256 ha and located in areas with high con- centrations of other agricultural fields. We were unable to address among-year variation in movements or home-range size because each year we conducted our study on a dif- ferent habitat type: rangeland in 2001, agri- cultural fields in 2002, and prairie dog habitat in 2003. To investigate Mountain Plover movements and home-range size, we attached 2.2-g radio transmitters (Advanced Telemetry Systems, Isanti, Minnesota) to nesting adult plovers at, or just before, hatching of eggs. We used I walk-in box traps made of mesh wire to cap- j ture adult plovers at their nests. We placed ' radio transmitters on adults in each of the three habitats: 35 birds in rangeland (2001), 26 in agricultural fields (2002), and 15 in prai- rie dog habitat (2003). Body mass of adult Mountain Plovers ranges from 90 to 110 g (Knopf 1996); thus, transmitters were <2.4% of their body mass. A transmitter was affixed by applying a light coating of waterproof ep- oxy (Ace, Starbrite, or Devcon) to the trans- mitter and then sliding it under the upper back feathers. This attachment procedure allowed the transmitters to drop off when the birds lat- er molted those feathers. Battery life of the transmitters was expected to be 56 days. Using a hand-held Yagi antenna, each day we attempted to locate adults with broods to record the presence of (and count) chicks and record their location and habitat. Due to ad- verse weather conditions, however, data for I some locations were collected at 2-day inter- I vals. First, we located birds from greater dis- j tances (up to 800 m) to avoid forcing brood : movements caused by human disturbance. Af- ter recording observer coordinates and dis- tance and bearing to each adult with a brood, we approached (usually by walking) the birds I to conlirm their location via visual obser\a- tion. Adults with broods were located until their chicks fledged, 36 days post-hatch (Mill- er and Knopf 1993). Adults with broods that did not successfully fledge at least one chick were not included in our analysis. To calculate brood home-range sizes, we used the fixed-kernel method (Worton 1995, Seaman and Powell 1996) with a smoothing parameter chosen by least squares cross vali- dation. This nonparametric technique depicts irregular distributions more accurately and produces home-range estimates with less bias relative to other home-range estimators (Sea- men and Powell 1996). Home-range values were based on 50 and 95% contour intervals, hereafter referred to as “core area” and “home range,” respectively (Bogner and Bal- dassarre 2002, Vega Rivera et al. 2003). Movement was defined as the distance moved between two consecutive locations. We also calculated minimum convex polygon home ranges, the minimum amount of area used to raise broods, for comparison with an earlier study (Knopf and Rupert 1996). Means are presented ± SD. RESULTS AND DISCUSSION Home range. — We monitored 12 broods on rangeland in 2001, 13 broods on agricultural fields in 2002, and 10 broods on prairie dog habitat (2 broods on the prairie dog complex, 8 on prairie dog towns) in 2003. Analyses were based on a mean of 20.3 ± 3.8 locations per brood in rangeland (range = 18-28), 28.7 ± 5.2 locations per brood in agricultural fields (range = 23-34), and 26.3 ± 6.6 locations per brood in prairie dog habitat (range — 19-33). Home-range estimates for the three habitats were relatively comparable for rangeland (146.1 ha ± 101.5), agricultural fields (131.6 ha ± 74.4), and prairie dog towns (243.3 ha ± 366.3). Although mean point estimates of the core area on prairie dog towns were >2X those on rangeland and agricultural fields, confidence intervals between the three habitat types oxer- lapped ( fable I ). fhe larger point estimates in home range and core area on luairie dog hab- itat could be attributed to two birds, both of which raised their broods on the prairie dog complex. One had an estimatetl home range of 1,156.5 ha and a core area of 210.8 ha, and the other had a home range of 630.0 ha and a core area ot I 14.4 ha. Removing the data for TABLE 1. Mean home-range size (ha) and movements of Mountain Plover adults with broods on rangeland (« = 12 broods), agricultural fields {n = 13), and prairie dog habitats in = 10) in eastern Colorado from 2001 to 2003. Home-range size was based on 50% and 95% fixed kernel (FK) and minimum convex polygon (MCP) home-range estimates. No. locations 50% FK 95% FK MCP Movement (m) Habitat (year) Mean SD Mean SD (95% Cl) Mean SD (95% Cl) Mean SD (95% Cl) Mean SD (95% Cl) 130 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 c in m in (N O • m 00 q m in >n S q r- q ^ On d 00 m m m rn m q rl (N 00 r-H (N ^ , q F- ON d (N ON lorado Bird Atlas Partnership and C’olorado Division of Wildlife. Denver, C\)lorado. Manning, A. li. li. and C'. M. Whuf;. 2001. Breeding biology of Mountain P\o\cvs {C haradrius nionlan- us) in the Uinta Basin. Western North American Naturalist 61 :223-228. M( Ki I VI Y. K.. B. K. Noon, and R. I .ambi kson. 1992. ('onser\ ation planning for species occupying frag- mcntctl landscapes: the case ot the Northern Spot- 132 THE WILSON BULLETIN Vol. 117, No. 2, June 2005 ted Owl. Pages 338-357 in Biotic interactions and global change (J. Kingsolver, P. Kareiva, and R. Hyey, Eds.). Sinauer Associates, Sunderland, Massachusetts. Miller, B. J. and E L. Knopf. 1993. Growth and sur- vival of Mountain Plovers. Journal of Eield Or- nithology 64:500-506. National Drought Mitigation Center. 2004. The drought monitor. University of Nebraska, Lincoln. http://drought.unl.edu (accessed 29 November 2004). PoYSA, H., J. Elmberg, K. Sjoberg, and P. Nummi. 2000. Nesting Mallards {Anas platyrhynchos) forecast brooding-stage food limitation when se- lecting habitat: experimental evidence. Oecologia 122:582-586. SCHMIEGELOW, P. K. A. AND M. MONKKONEN. 2002. Habitat loss and fragmentation in dynamic land- scapes: avian perspectives from the boreal forest. Ecological Applications 12:375-389. Seaman, D. E. and R. A. Powell. 1996. An evaluation of the accuracy of kernel density estimators for home range analysis. Ecology 77:2075-2085. Sekercioglu, C. H., P R. Ehrlich, G. C. Daily, D. Aygen, D. Goehring, and R. E Sandi. 2002. Dis- appearance of insectivorous birds from tropical forest fragments. Proceedings of the National Academy of Sciences (USA) 99:263-267. Shackford, j. S., D. M. Le.slie, Jr., and W. D. Hard- en. 1999. Range-wide use of cultivated helds by Mountain Plovers during the breeding season. Journal of Eield Ornithology 70:1 14-120. Vega Rivera, J. H., W. J. McShea, and J. H. Rappole. 2003. Comparison of breeding and postbreeding movements and habitat requirements for the Scar- let Tanager {Piranga olivacea) in Virginia. Auk 120:632-644. White, G. C., J. R. Dennis, and E M. Pusateri. 2005. Area of black-tailed prairie dog colonies in eastern Colorado. Wildlife Society Bulletin In press. WoRTON, B. J. 1995. Using Monte Carlo simulation to evaluate kernel-based home range estimators. Journal of Wildlife Management 59:794-800. WuNDER, M. B., P. L. Knopf, and C. A. Pague. 2003. The high-elevation population of Mountain Plo- vers in Colorado. Condor 105:654-662. Wilson Bulletin 1 17(2);133-141, 2005 WINTER FORAGING OF FONG-TAIFED DUCKS (CLANGULA HYEMALIS) EXPFOITING DIFFERENT BENTHIC COMMUNITIES IN THE BALTIC SEA RAMUNAS ZYDELIS' 34 AND DAINORA RUSKYTU ABSTRACT. — We studied the feeding ecology of Long-tailed Ducks (Clangula hyemalis) in two different marine benthic habitats in the Baltic Sea to determine whether there were differences in diet choice, foraging selectivity, body condition, and bird abundance. Our results corroborate earlier suggestions that Long-tailed Ducks exhibit ecological plasticity in selecting winter habitat and food. The majority of Long-tailed Ducks occurred in hard-bottom habitats where they relied on the bivalve Mytilus edulis\ however, some of the population wintered in less productive, soft-bottom habitats where they employed a prey-selective foraging strategy, in which they fed on less abundant, but energy rich, crustaceans. Both strategies were apparently viable, as dissected birds in both habitats were in good body condition and had substantial fat reserves. Received 20 April 2004, accepted 11 February 2005. The Long-tailed Duck {Clangula hyemalis) is the most abundant sea duck wintering in the Baltic Sea, where estimated numbers exceed 4 million. Wintering Long-tailed Ducks inhab- i it a variety of coastal habitats and shallow off- , shore banks (Durinck et al. 1994). Diet com- ' position varies widely throughout their Hol- ^ arctic range (Madsen 1954, Peterson and El- larson 1977, Vermeer and Levings 1977, I Goudie and Ankney 1986, Stempniewicz 1995, Bustnes and Systad 2001, Jamieson et al. 2001). However, few attempts have been made to relate feeding habits of Long-tailed Ducks to attributes of their local environment (Nilsson 1972, Stott and Olson 1973, Kube 1996). Long-tailed Ducks are recognized as opportunistic feeders (Peterson and Ellarson 1977, Goudie and Ankney 1986, Bustnes and ^ Systad 2001), but ecological factors related to ! use of different habitats have received little study. We investigated food choice of Long- tailed Ducks wintering in two distinct marine habitats in nearshore waters of the Baltic Sea off the coast of Lithuania. Our objectives were to determine whether there were differences in diet choice of Long-tailed Ducks in the two winter habitats, and whether body condition of the ducks varied between the habitat types. ii ' Inst, of I-'cology of Vilnius liniv.. Akaclctuijos 2, j LT-08412 Vilnius. I.ithuania. I ^Klaipeda Univ., tl. Manto 84. i;i'-58()8 Klaipeda. ' Lithuania. i ^Current address: C'entre for Wildlife Iwology. ,Si- 1 mon tTaser Univ.. 8888 University Dr. Iturnaby. BC’ j V5A LSb. Canada. I ‘‘Corresponding author; e-mail: r/ydelis(o'sfu.ea METHODS Study area. — The Lithuanian coast can be characterized as an exposed, sandy coast, typ- ical of the southern and eastern Baltic Sea (Oleninas et al. 1996). The sea floor is dom- inated by sand, gravel, or boulders. Sandy- bottom substrates predominated in the south- ern half of our study area along the Curonian Spit coast. The northern half of the Lithuanian nearshore zone is characterized by a mosaic of sediments of sand, gravel, and boulders (Oleninas et al. 1996). The sublitoral slope is gentle, with the 10-m isobath extending 700- 2,000 m and the 20-m isobath extending 1,500-4,000 m from the shore. Water salinity along the Lithuanian coast is low, ranging from 6 to 8%o, which results in relatively poor faunal and floral diversity, as well as in low productivity. Two main types of macrofaunal communi- ties can be distinguished in the Lithuanian coastal zone: the Mytilus edulis community of sessile, epi faunal li Iter-feeders, and the Ma- coma haltica community of mobile, infaunal surface-deposit feeders (Olenin 1996, Oleni- nas et al. 1996). fhe M. edulis community dominates in the northern half of the Lithua- nian coastal zone, occurring on hard bottoms covered by stones and boulders at depths be- tween 5 and 30 m. 'fhis community has the highest biodiversity (up to 50 macro/ooben- thos species) and biomass (mean = 1.750 g/ m', maximum 2,500 g/nP wet weight). A/. edulis makes up 939? of the total biomass: lialanus improvisus (a barnacle) and all the 133 134 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 remaining species contribute ~7 and <1% of total wet weight, respectively. In some places, stony substrates at depths from 4 to 14 m are overgrown by the red algae, Furcellaria lum- hricalis, which serves as an important spawn- ing ground for Baltic herring (Clupea haren- gus membras; Olenin 1996, Oleninas et al. 1996). The M. baltica community is associated with soft bottoms, and extends along the coast of the Curonian Spit at depths from 5 to 30 m. This habitat can be characterized as a ho- mogenous, benthic biotope with up to 40 ma- crozoobenthos species dwelling in a sandy bottom. M. baltica and Mya arenaria are the dominant infaunal bivalves, composing 61 and 12% of the total biomass, respectively. Polychaetes {Nereis diversicolor, Pygospio elegans) and crustaceans (Saduria entomon and Corophium spp.) also are abundant. Mean zoobenthos biomass is —150 g/m^ wet weight, with a maximum of —300 g/m^ (Olenin 1996, Oleninas et al. 1996). Based on spatial distribution and domi- nance of benthic communities (Olenin 1996; S. Olenin unpubl. data), three zones have been distinguished along the Lithuanian coast: a hard-bottom benthic community zone, an in- termediate zone, and a soft-bottom commu- nity zone (Fig. 1). We present data on Long- tailed Duck foraging in hard-bottom and soft- bottom benthic community zones, but not the intermediate zone. Data collection and analysis. — Birds acci- dentally drowned in fishing nets were collect- ed for diet analysis during winters of 1997/ 1998 through 2000/2001. Nets were set at depths ranging from 1.5 to 20 m. In total, 326 Long-tailed Ducks were collected: 181 from habitats with hard-bottom and 145 from areas with soft-bottom substrates. Sex-age cohorts of collected birds in hard- and soft-bottom habitats, respectively, were as follows: im- mature males 13 and 14%; adult males 55 and 58%; immature females 16 and 8%; and adult females 16 and 20%. The majority of collected birds were frozen within hours of collection. Frozen birds were thawed in a laboratory, dissected, aged, and sexed using the methods of Jones et al. (1982). Body fat was assessed by examining the subcutaneous fat layer on the upper ab- domen, lower abdomen, and lower intestines. Ranked categories of fat indices ranging from 0 to 3 were used for each deposit (0 = no fat and 3 = abundant fat), with overall fat scores calculated as the sum of the three indices (Jones et al. 1982). If not examined immedi- ately, gizzards and esophagi were removed and deep-frozen or preserved in 4% formal- dehyde solution until contents could be ana- lyzed. Contents of gizzards and esophagi were treated separately, with material sorted, iden- tified to the lowest possible taxonomic level, measured, and weighed. Each prey species was weighed separately except for small crus- taceans, where gammarids were pooled with- out identifying specimens to species. Barna- cles and bryozoans (Electra crustulenta) at- tached to mollusk shells were not considered as separate prey items; only loose barnacles were included in the analyses. The digestion stage of gizzard contents was assessed ac- cording to the following scheme: (1) food items intact, visually unaffected by digestion; (2) food at initial stage of digestion, soft prey still easy identifiable, much identifiable tissue; (3) food items heavily affected by digestion with some remains of tissues; and (4) food items heavily affected by digestion, no iden- tifiable tissues remaining. Diet composition was assessed according to wet weight of prey, including mollusk shells, from esophagi and gizzards showing stages 1 and 2 of digestion. Prey items were weighed to 0.01 g after removing surplus water by placing food items on filter paper. Data were summarized as the mean percentage of wet weight of each prey taxa per individual (Kra- pu and Reinecke 1992). Frequency of occur- rence was calculated as the percentage of birds containing a certain food item. Inorganic materials (sand, pebbles, and amber) were ex- cluded from subsequent analyses of content. Preference of food objects in the two hab- itats was measured by Ivlev’s selectivity index (Manly et al. 1993), calculated using the for- mula: n + p/ where r, is the proportion of an item in the diet. Pi is the proportion of an item in the en- vironment, and E is the selectivity index. Pos- itive values indicate that the item is sought out Zydelis and Ruskyte • WINTER FORAGING OF FONG-TAILED DUCKS 135 FIG. 1. Study area along the Lithuanian coast of the Baltic Sea and the three different habitat /.ones where the feeding ecology of Long-tailed Ducks was studied; (I) hard-bottom habitat, (2) intermediate /.one, and (3) soft-bottom habitat. in the environment and negative values indi- eate that it is not. To determine /?,, we used available benthos composition and biomass data that were collected in multiple sampling stations along the Lithuanian coast during 19X0-1992. These dat a were summari/.ed as average values (Olenin 1996, Oleninas et al. 1996), and correspond closely to those of oth- er studies along the Lithuanian coast (Maksi- movas et al. 1996, Bubinas and Vaitonis 2003). Because bivalve communities are con- sidered to be relatively stable in the Baltic Sea (Kautsky 1982), we assumetl that food re- .sources utilized by Long-tailed Ducks during our study were well represented by previous studies (Olenin 1996, Oleninas et al. 1996). 136 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 We also assumed that the M. ediilis commu- nity offers a rich and predictable food re- source for Long-tailed Ducks, since the ma- jority of M. ediilis are of edible size, acces- sible to diving birds, and abundant (Daunys 1995). The M. bcdtica community was consid- ered a poorer food resource due to low' aver- age biomass and because potential food ob- jects are mostly buried in sand. We conducted surveys to assess the abun- dance and distribution of wintering Long- tailed Ducks during four consecutive winter- ing seasons from 1997/1998 through 2000/ 2001. Survey areas were 10-km sections of shoreline along both hard- and soft-bottom community zones, with a 17-km gap between them (Fig. 1). Bird survey areas corresponded with the locations where ducks were obtained for diet analysis. We conducted bird counts from shore one to two times per month from December until April. Adverse conditions, such as choppy seas and ice floes, occasion- ally prevented us from conducting surveys. We used a spotting telescope ( 20-45 X) and binoculars (10 X 50) to survey for birds on the water up to 2 km from shore. Bird abun- dance in the two habitats was summarized as mean number of ducks observed per linear km of shoreline surveyed. Statistical analyses were performed using Statistica 6.0 (StatSoft, Inc. 2001). We used nonparametric statistics to compare count and categorical data: a Kol- magorov-Smirnov test was applied to compare counts between two samples, Kruskal-Wallis ANOVA was used to compare multiple sam- ples, and Mann-Whitney (7-tests were used to compare data where sample sizes were low {n < 20; StatSoft, Inc. 2004). Standard devia- tions (SD) are given for means and statistical significance was set at P < 0.05. Considering the controversy surrounding the use of signif- icance testing in the biological sciences (Co- hen 1994, Johnson 1999), we also calculated effect sizes using the equation: Ml - M-, d = , Spooled where d is the difference between means Mj and Mt divided by the pooled standard devi- ation. cTpooied, which is defined as the square root of the mean of the two variances (Cohen 1988;. Operational definitions for effect sizes are small {d = 0.2), intermediate {d = 0.5), and large {d = 0.8; Cohen 1988). RESULTS Diet cofuposition. — A total of 119 Long- tailed Ducks that fed over hard-bottom, and 87 that fed over soft-bottom substrates con- tained undigested food in gizzards and esoph- agi. At least 17 and 18 different prey taxa were ingested in hard- and soft-bottom habi- tats, respectively (Table 1). The actual number of prey species ingested was higher, as gam- marids were pooled together without identifi- cation to species, and there were some speci- mens in other taxonomic groups not identified to species level. The few identified gammarids were Gammarus oceaniciis, G. salinus, and G. zaddachi. The mean number of prey species ingested per Long-tailed Duck was 2.2 ± 1.1 (n = 119) in areas with hard-bottom and 1.9 ± 1.2 (n = 87) in soft-bottom habitat (Kol- magorov-Smimov test: Z = 1.33, P = 0.058; d = 0.28). Over hard-bottom substrates, M. ediilis dominated in terms of wet weight and fre- quency of occurrence in the diet of Long- tailed Ducks (Table 1). The selectivity index for M. ediilis was close to zero {E = -0.05, s = 0,93, = 0.85), which indicates no active selection or avoidance. S. entomon was the dominant food type of birds that fed over soft-bottom substrates (Table 1). The se- lectivity index for this prey item was P = 0.73 (Pe.,o,non = 0.1, = 0.63), indicating that S. entomon was actively sought. Selectivity indices of bivalve clams in soft-bottom habitat were strongly negative for M. baltica {E = -0.79. = 0.61, = 0.07) and M. OVenOriCl (P 0.54, Parenana 0.12, farenaria = 0.04). Although M. ediilis was the main prey spe- cies taken from hard-bottom habitat through- out the winter, Baltic herring spawn became the dominant food item in April, when it com- posed 68% of dietary wet weight (Fig. 2A). Crustaceans were the dominant food in soft- bottom habitat and did not fluctuate signifi- cantly between months (Kruskal-Wallis AN- OVA; X" = 3.08, df = 4, P = 0.54; Fig. 2B; effect size d range: 0.05-0.50). We detected no significant sex- or age-related differences in diet composition in either habitat. Eat score. — Mean fat scores of Long-tailed Zydelis and Riisky'te • WINTER FORAGING OF LONG-TAILED DUCKS 137 TABLE 1 . Diet composition of Long-tailed Ducks in soft- and hard-bottom habitats in the Lithuanian Baltic Sea, 1997-2001, expressed as frequency of occurrence (FO) and mean percent of wet weight (WW). Dominant food items are in boldface. Soft-bottom Hard-bottom (« = 87 birds) (n = 119 birds) Mean % of Mean % of Prey FO (%) WW (SD) FO (%) WW (SD) Algae 4 (4.6) 0.3 (1.7) 15 (12.6) 1.3 (9.4) Ceramium rubrwn 2 (1.7) 0.0 (0.0) Furcellaria lumbricalis 1 (1.2) 0.1 (0.8) 13 (10.9) 1.1 (9.2) Unidentified algae 3 (3.5) 0.2 (1.5) 4 (3.4) 0.3 (1.8) Polychaetes 16 (18.4) 7.7 (24.4) 7 (5.9) 0.1 (0.3) Nereis diversicolor 13 (14.9) 6.5 (22.2) Unidentified polychaete 3 (3.5) 1.2 (10.7) 7 (5.9) 0.1 (0.3) Bivalves 32 (36.8) 14.5 (30.5) 113 (95.0) 86.8 (30.9) Cardiiim edide 3 (3.5) 0.8 (5.7) Macoma boltica 14 (16.1) 7.2 (23.0) 5 (4.2) 0.4 (3.0) My a arenaria 15 (17.2) 3.6 (14.0) 10 (8.4) 1.0 (8.6) M. arenaria siphons 1 (1.2) 0.8 (7.4) Mytilus edulis 4 (4.6) 2.3 (14.4) 110 (92.4) 84.6 (33.6) Gastropods 11 (9.3) 0.1 (1.0) Hydrobia sp. 8 (6.7) 0.0 (0.0) Theodoxus fluviatilis 2 (1.7) 0.1 (1.0) Unidentified gastropods 1 (0.8) 0.0 (0.1) Crustaceans 71 (81.6) 74.3 (39.7) 27 (22.7) 3.7 (14.7) Bcdanus improvisus 1 (1.2) 0.0 (0.0) 13 (10.9) 0.6 (2.2) Crangon crangon 5 (5.8) 2.3 (14.2) 1 (0.8) 0.7 (8.0) Gammarus spp. 4 (4.6) 0.0 (0.0) 11 (9.2) 0.6 (3.0) Idothea sp. 1 (0.8) 0.0 (0.0) My sis mixta 1 (0.8) 0.0 (0.0) Neomysis integer 10 (11.5) 9.1 (28.7) 2 (1.7) 1.3 (10.2) Saduria entomon 62 (71.3) 63.1 (44.9) 2 (1.7) 1.4 (1 1.1) Unidentified crustaceans 1 (1.2) 0.1 (0.6) 2 (1.7) 0.0 (0.1) Fish 7 (8.1) 3.3 (12.9) 2 (1.7) 0.8 (6.7) Ammodytes sp. 4 (4.6) 1.8 (9.6) Cliipea harengus eggs 10 (8.4) 7.2 (24.7) Gasteroste us acute a tus 1 (1.2) 0.1 (1.0) Osmerus eperlanus 1 (1.2) 0.5 (4.3) Platichthys jiesus 2 (2.3) 0.1 (0.7) Poniatoschistus sp. 1 (0.8) 0.2 (2.7) Sprattus sprattus 1 (1.2) 0.2 (1.8) Unidentified fish 2 (2.3) 0.7 (4.7) 1 (0.8) 0.6 (6.2) Ducks collected from areas with hard- and soft-bottom sediments were 6.9 ± 1.9 (/? = 124) and 7.4 ± 1.4 (// = 93) respectively {U- test = 5,061.0, Z = -1.54, r = 0.12; d = 0.33; Table 2). Over hard-bottom habitat, the mean fat score of adtilt males was signifi- cantly lower than that of immature males (U = 317.5, Z = 2.86, = 0.004) and immature females (U = 362, Z = -3.17, r = 0.002). Over soft-bottom habitat, adult males also had the lowest fat reserves, which differed signif- icantly from that of immature females {IJ — 81.5, Z = -2.79, r = 0.005); there were no significant differences observed among other sex-age groups. Effect sizes among sex and age cohorts (Table 3) indicated somewhat sim- ilar relationships to those obtained by Mann- Whilney (/-tests. No trend was obser\ed in fat-score values over (he course of the win- tering season, and overall high fat-score val- ues (>5) indicated that birds were in good body condition with considerable fat reserves. Ahundancc and distribution. — Abundance of Long-tailed Ducks per linear km of shore- line over hard-bottom habitat (331 ± 544, n - 26 surveys), was nearly 10 times higher Mean percent prey wet weight Mean percent prey wet weight 138 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 A □ Bivalves Q Crustaceans □ Fish eggs ■ Other 1 3 27 78 10 2 21 19 23 22 LIG. 2. Percent wet weight of prey taken by Long- tailed Ducks in the Lithuanian Baltic Sea, December- April, 1997-2001. Bivalves dominated the diet in hard-bottom habitat (A), with herring eggs being im- portant in April. Crustaceans dominated the diet of birds in soft-bottom habitat (B). Sample sizes appear above bars. than that over soft-bottom habitat (36 ± 23, n — 17 surveys; U = 60.5, Z = 3.99, P < 0.001; d = 0.77). DISCUSSION Our results provide insight into the feeding ecology of Long-tailed Ducks in two contrast- ing coastal habitats of the eastern Baltic Sea. Marked differences were observed in Long- tailed Duck foraging patterns in different hab- itats. Differences involved numbers of birds using those areas, diet composition, and the degree of selectivity when choosing food items. However, body condition of birds was similar between habitats. The majority of Long-tailed Ducks occurred over rich, hard- bottom communities, where densities were ap- proximately 10 times higher than in soft-bot- tom areas. TABLE 2. Eat scores of Long-tailed Ducks in hard- and soft-bottom habitats along the Baltic Sea coast of Lithuania, 1997-2001. Birds were in generally good body condition (i.e., fat scores >5). Habitat type/age class Mean SD Range n Hard-bottom Immature males 7.7 2.0 3-9 17 Adult males 6.3 1.9 2-9 68 Immature females 7.8 1.7 4-9 20 Adult females 7.1 1.6 4-9 19 All birds 6.9 1.9 2-9 124 Soft-bottom Immature males 7.6 1.4 4-9 14 Adult males 7.1 1.4 4-9 53 Immature females 8.5 0.8 7-9 8 Adult females 7.8 1.3 5-9 18 All birds 7.4 1.4 4-9 93 Prey-item selectivity was very low in hard- bottom habitat, where birds fed primarily on the most available prey item, M. ediilis. In April, ducks switched to feeding on fish eggs, when this temporary, but energy-rich, food source became available. Rich beds of M. ed- ulis and spring herring spawn offer predict- able food resources, so birds can ensure nec- essary energy intake with a given investment of effort. In contrast to hard-bottom habitat. Long-tailed Ducks exhibited a high degree of selectivity in soft-bottom habitat, where they foraged on the isopod, S. entomon, despite a benthic community dominated — in both bio- mass and abundance — by infaunal bivalves (Olenin 1996, Bubinas and Vaitonis 2003). In soft-bottom habitat, dominant bivalves were present at much lower densities, and some of them were unavailable because they burrow deeply into the sediment (Olenin 1996, Kube TABLE 3. Effect sizes contrasting fat indices among age and sex cohorts of Long-tailed Ducks col- lected along the Baltic Sea coast of Lithuania, 1997- 2001. Contrasts for hard-bottom sites are in the lower left portion of the table, with soft-bottom contrasts in upper right. See methods for interpretation of values. Immature males Adult males Immature females Adult females Immature males — 0.41 0.76 0.10 Adult males 0.70 — 1.29 0.53 Immature females 0.05 0.82 — 0.69 Adult females 0.33 0.44 0.43 — Zydelis and Ruskyte • WINTER FORAGING OF LONG-TAILED DUCKS 139 1996). Therefore, birds in soft-bottom habitat may not be able to rely on mollusks, and in- stead search for mobile, but more energy-rich, food items such as crustaceans. Although less available than sessile bivalves, species like S. entomon contain twice as much energy per unit wet weight as M. edulis (Rumohr et al. 1987); therefore, birds require less biomass to satisfy bioenergetic requirements. Dominant prey of Long-tailed Ducks varies in different parts of the wintering range: gas- tropods are the predominant food item along the coasts of New Hampshire (Stott and Olson 1973) and northern Norway (Bustnes and Sys- tad 2001); crustaceans are the most important prey for birds wintering at Lake Michigan (Peterson and Ellarson 1977), coastal British Columbia (Vermeer and Levings 1977), and Hudson Bay (Jamieson et al. 2001); and bi- valves dominate their diet in the Baltic Sea (Madsen 1954, Nilsson 1972, Stempniewicz 1995, Kube 1996). Many authors agree that Long-tailed Ducks are opportunistic feeders, foraging on the most abundant and available prey (Peterson and Ellarson 1977, Goudie and Ankney 1986, Bustnes and Systad 2001). However, Jamieson et al. (2001) reported se- lective foraging by Long-tailed Ducks in po- lynyas (areas of open water in sea ice) of Hud- son Bay, where birds fed almost exclusively on crustaceans, even though M. edulis were present. Jamieson et al. (2001) suggested that birds have to be selective by foraging on prey more proh table than M. edulis to meet ener- getic requirements in this harsh environment. Although bivalves generally dominate the diet of Long-tailed Ducks in the Baltic Sea, Stempniewicz (1995) found that males, which foraged at depths >20 m in the Gulf of I Gdansk, fed exclusively on S. entomon iso- pods and suggested that only larger males are ) able to dive and feed efficiently at greater i depths. I Assuming that animals attempt to maximize , their net rate of energy intake by balancing ' food-item profitability and time spent feeding, the findings of our study can be discus.scd within the context optimal foraging theory (Pyke et al. 1977). If we assume that the rate of avian energy intake corresponds to the total biomass of macrozoobenthos, then Long- tailed Ducks would be expected to feed only in hard-bottom habitats where prey are abun- dant and predictable. This theory is partly in agreement with our results, as we found a ma- jority of Long-tailed Ducks occurring in rich, hard-bottom habitats. However some birds still used poor, soft-bottom areas and alterna- tive explanations must be considered. Risk- sensitive foraging theory (Caraco 1980, 1981) may explain body condition of birds. This the- ory suggests that animals might make deci- sions to optimize a trade-off between food predictability in one habitat and greater max- imum potential return in another (Caraco 1980, 1981). Guillemette et al. (1992) found that Common Eiders (Somateria mollissima) in good physiological condition in the Gulf of St. Lawrence used predictable habitats, where they foraged on blue mussels {M. edulis). In- dividuals in poorer condition, however, used a risk-prone foraging strategy and searched for more nutritious spider crabs {Hyas ara- neus) in habitat where prey abundance was low. In our study area. Long-tailed Ducks used both productive hard-bottom habitat and areas with a relatively unproductive soft-bottom community. Risk-sensitive foraging theory (Caraco 1980, 1981) suggests that a nonselec- tive foraging strategy among birds might be expected in rich, benthic communities, where- as an active searching strategy for particular food items might be employed in less produc- tive habitats. Accordingly, Long-tailed Ducks foraging in rich, benthic communities should be in better physiological condition. Those in soft-bottom habitats should be in poorer or more variable condition. However, similar body conditions and variance estimates of Long-tailed Duck fat reserves in the two hab- itats indicate that Long-tailed Ducks — despite differences in productivity, foraging strategy, and food objects ingested — were able to attain similar (good) body condition. We speculate that the stable, and perhaps optimal, body re- serves observed in Long-tailed Ducks throughout the wintering season indicate that birds are not energy stressed. Lower fat re- serves in adult males may be due to higher energy expenditures during intensi\e court- ship activities (RZ pers. obs.) and/or better adaptability of rnalcs to the environment and a subsct|ucnt lower need to carry extra re- serves. fhe results of our study corroborate the 140 THE WILSON BULLETIN • Vol. 1 17, No. 2, June 2005 ecological plasticity of Long-tailed Ducks when selecting wintering habitats and choos- ing food items. We conclude that the majority of Long-tailed Ducks wintering in our study area actively select habitats and rely on the bivalve M. ediilis. However, some of the pop- ulation occurs in less productive habitats where they gain sufficient energy by foraging selectively on crustaceans. ACKNOWLEDGMENTS We are grateful to J. Zarankaite, A. Petraitis, and R. Skeiveris who helped collect birds; we thank several fishermen for their cooperation. Our special thanks to S. Olenin and D. Daunys for their help in understand- ing the structure of benthic communities. We appre- ciate helpful comments provided by J. Durinck, L. Nilsson, T D. Lox, R. Ydenberg, D. Esler, and S. Iver- son on different versions of the manuscript. We also thank three anonymous referees for their detailed com- ments and suggestions. LITERATURE CITED Bubinas, a. and G. Vaitonis. 2003. The analysis of the structure, productivity, and distribution of zoobenthocenoses in the Lithuanian economic zone of the Baltic Sea and the importance of some benthos species to fish diet. Acta Zoologica Li- tuanica 13: 1 14-124. Bustnes, j. O. and G. H. Systad. 2001. Comparative feeding ecology of Steller’s Eiders and Long- tailed Ducks in winter. Waterbirds 24:407-412. Caraco, T. 1980. On foraging time allocation in a sto- chastic environment. Ecology 61:119-128. Caraco, T. 1981. Risk-sensitivity and foraging groups. Ecology 62:527-531. Cohen, J. 1988. Statistical power analysis for the be- havioral sciences, 2nd ed. Lawrence Earlbaum Associates, Hillsdale, New Jersey. Cohen, J. 1994. The earth is round {p < .05). Amer- ican Psychologist 49:997-1003. Daunys, D. 1995. Structure and distribution of filtrat- ing benthos communities in Lithuanian nearshore zone. B.Sc. thesis, Klaipeda University, Klaipeda, Lithuania. [In Lithuanian with English summary] Durinck, J., H. Skov, L. P. Jensen, and S. Pihl. 1994. Important marine areas for wintering birds in the Baltic Sea. EU DG XI research contract no. 2242/ 90-09-01. Ornis Consult report, Copenhagen, Denmark. Goudie, R. I. AND C. D. Ankney. 1986. Body size, activity budgets, and diets of sea ducks wintering in Newfoundland. Ecology 67:1475-1482. Guillemette, M., R. C. Ydenberg, and J. H. Him- MELMAN. 1992. The role of energy intake rate in prey and habitat selection of Common Eiders So- materia mollissima in winter: a risk-sensitive in- terpretation. Journal of Animal Ecology 61:599- 610. Jamieson, S. E., G. J. Robertson, and H. G. Gilchr- ist. 2001. Autumn and winter diet of Long-tailec Duck in the Belcher Islands, Nunavut, Canada, Waterbirds 24:129-132. Johnson, D. H. 1999. The insignificance of statistical significance testing. Journal of Wildlife Manage- ment 63:763-772. Jones, P. H., B. P. Blake, T. Anker-Nilssen, and O. W. R0STAD. 1982. The examination of birds killed in oil spills and other incidents: a manual of sug- gested procedure. Unpublished Report, Nature Conservancy Council, Aberdeen, Scotland. Kautsky, N. 1982. Quantitative studies on gonad cy- cle fecundity reproductive output and recruitment in a Baltic Mytilus edulis population. Marine Bi- ology 68:143-160. Krapu, G. L. and K. j. Reinecke. 1992. Poraging ecol- ogy and nutrition. Pages 1-29 in Ecology and management of breeding waterfowl (B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Caldec, and G. E. Krapu, Eds.). University of Minnesota Press, Minneapolis. Kube, j. 1996. The ecology of macrozoobenthos and sea ducks in the Pomeranian Bay. Marine Science Reports, no. 18. Baltic Sea Research Institute, Warnemunde, Germany. Madsen, J. P. 1954. On the food habits of diving ducks in Denmark. Danish Revue of Game Biology 2: 157-266. Maksimovas, J., V. Labanauskas, and S. Oleninas. 1996. Reproduction of Baltic herring and studies of benthic biocenoses at Klaipeda — Palanga coast. Zuvininkyste Lietuvoje 2:143-153. [In Lithuanian with English summary] Manly, B. P. J., E. E. McDonald, and D. L. Thomas. 1993. Resource selection by animals: statistical design and analysis. Chapman and Hall, London, United Kingdom. Nilsson, L. 1972. Habitat selection, food choice, and feeding habits of diving ducks in coastal waters ot south Sweden during the non-breeding season. Ornis Scandinavica 3:55-78. Olenin, S. 1996. Comparative community study of the south-eastern Baltic coastal zone and the Curonian Lagoon bottom. Pages 153—161 in Proceedings of the 13th symposium of The Baltic Marine Biolo- gists (A. Andrushaitis, Ed.). Institute of Aquatic Ecology, University of Latvia, Riga, Latvia. Oleninas, S., D. Daunys, and V. Labanauskas. 1996. Classification principles of the Baltic Sea Lithua- nian coastal biotopes. Geografijos Metrastis 29: 218-231. [In Lithuanian with English summary] Peterson, S. and R. S. Ellarson. 1977. Pood habits of Oldsquaws wintering on Lake Michigan. Wil- son Bulletin 89:81-91. Pyke, G. H., H. R. Pulliam, and E. L. Charnov. 1977. Optimal foraging: a selective review of theory and tests. Quarterly Revue of Biology 52:137-154. Rumohr, H., T. Brey, and S. Ankar. 1987. A com- pilation of biometric conversion factors for ben- thic invertebrates of the Baltic Sea. The Baltic Marine Biologists Publication, no. 9. StatSoft, Inc. 2001. Statistica, ver. 6.0. StatSoft, Inc., Tulsa, Oklahoma. Zydelis and Ruskyte • WINTER FORAGING OF FONG-TAILED DUCKS 141 StatSoft, Inc. 2004. Electronic statistics textbook. StatSoft, Inc., Tulsa, Oklahoma, www. StatSoft, com/textbook/stathome.html (accessed 8 April 2005). Stempniewicz, L. 1995. Feeding ecology of the Long- tailed Duck Clangula hyernalis wintering in the Gulf of Gdansk (southern Baltic Sea). Ornis Sve- cica 5:133-142. Stott, R. S. and D. R Olson. 1973. Food-habitat re- lationships of sea ducks on the New Hampshire coastline. Ecology 54:996-1007. Vermeer, K. and C. D. Levings. 1977. Populations, biomass and food habitats of ducks on the Fraser Delta intertidal area, British Columbia. Wildfowl 28:49-60. Wilson Bulletin 1 1 7(2): 142-1 53, 2005 BREEDING BIOLOGY OE JABIRUS {JABIRU MYCTERIA) IN BELIZE ROSE ANN BARNHILL,!^ DORA WEYER,^ W. FORD YOUNG, ^ KIMBERLY G. SMITH, ^ AND DOUGLAS A. JAMES^ ABSTRACT. — We summarized published and unpublished information on the reproductive biology and ecol- ogy of Jabirus {Jahiru mycteria) in Belize. From 1968 to 1987, 91 individual nests were discovered in 16 of 19 breeding seasons; 69 nests were confirmed as active. Jabiru nests were 15-30 m above ground in Ceiba pentandra (five nests), Finns caribaea (five nests), Tabebuia ochracea (one nest), Acoelorrhaphe wrightii (one nest), and dead trees (three nests). Most nests (32 of 36) were located in northern and central Belize in isolated, tall, emergent trees (trees with crowns that stand above the surrounding canopy). Nest trees were usually sur- rounded by riparian forests or seasonally inundated pine-savanna wetlands situated in transitional zones where pine savannah meets coastal lowlands. Two nests were used for at least 10 years. The breeding season began with the transition from wet to dry season (November-December). Earliest eggs were observed on 12 December 1973 and latest eggs on 26 February 1987. Earliest nestlings were observed on 15 January 1970, and young were seen on nests as late as 28 May 1973. Young birds fledged 100 to 115 days after hatching but were still dependent on parents. From 1968 to 1987, a total of 44 eggs and 92 nestlings were counted. Mean clutch size was 3.14 ± 1.17 SE (range = 1-5 eggs, n = 14 nests). Flatching success for four nests during the 1972-1973 breeding season was 43.8%. For 14 years in which crude hatching success (nestlings per active nest) could be calculated, 71.6% (43 of 60) of all active nests had at least one nestling. The mean number of nestlings per nest was 2.13 ± 0.71 SE (range = 1-4 nestlings, n = 43 nests). Productivity (the number of nestlings per nest for all active nests) was 1.53. These results were similar to those of two other studies of Jabiru breeding biology conducted in Brazil and Venezuela. Jabiru populations in Belize appear to have increased since the species gained protected status in 1973. Received 23 July 2004, accepted 4 March 2005. Jabirus {Jabiru mycteria) breed locally from southern Mexico (Campeche, Tabasco) through the lowlands of Central America and east of the Andes to northern Argentina (Bent 1926, Blake 1977, Knoder et al. 1980, Han- cock et al. 1992, Antas and Nascimento 1997). They favor extensive inland and shal- low wetland habitats for feeding, but prefer nearby wooded areas for roosting and nesting (Hancock et al. 1992, Stotz et al. 1996, Antas and Nascimento 1997; DW pers. obs.). Jabirus are distributed widely but are not abundant anywhere in their breeding range. They are considered regionally threatened, although not endangered (Luthin 1984, 1987; Stotz et al. 1996). In southeastern Brazil, however, they have been extirpated from the basins of the Paraiba do Sul, Tiete, and Grande rivers, and there are only a few remnant populations re- stricted to the Sao Francisco River valley in ’ Dept, of Biological Sciences, Univ. of Arkansas, Fayetteville, AR 72701, USA. 2 371 County Rd. 244, Eureka Springs, AR 72632, USA. 3 Deceased 1999. ■^Corresponding author; e-mail: rbarnhi@uark.edu the state of Minas Gerais (Antas and Nasci- mento 1997:17). Comprehensive information on numbers and population trends of Jabirus are limited, especially in Central America. Luthin (1987), however, observed Jabirus throughout their breeding range and concluded that there are three distinct populations: Central American, northern South American, and south-central South American. He suggested that research on the ecology and status of Jabirus be undertaken for each distinct population to develop a global conservation strategy for the species. DW {in Scott and Carbonell 1986) reported on the sta- tus of wetlands and conservation of waterbirds in Belize, referencing known Jabiru nesting ar- eas. Recently, Frederick et al. (1997) docu- mented previously unrecorded populations of Jabirus breeding in coastal wetlands of Nica- ragua and Honduras, (Miskito Coast and La Mosquitia, respectively) during aerial strip- censuses of breeding waterbirds. Kahl (1971, 1973), Thomas (1981, 1985), and Poveda (2003) described behavior and comparative ethology of Jabirus in Argentina, Venezuela, and Costa Rica, respectively, and Antas and Nascimento (1997) studied the 142 Barnhill et al. • BREEDING BIOLOGY OE JABIRUS 143 TABLE 1. Observed egg-laying dates for the Jabiru, throughout its range. Country Egg-laying dates Source SE Mexico Dec-Jan, Mar Luthin 1984, Hancock et al. 1992 Belize Dec-Feb Hancock et al. 1992, this study Honduras Feb Frederick et al. 1997 Nicaragua Mar Frederick et al. 1997 Costa Rica Nov-Apr"* Villarreal-Orias 1988, Poveda 2003 Colombia (Rio San Jorge) Sep-Nov Kahl 1971, Hancock et al. 1992 Venezuela (Llanos) Aug-Nov Thomas 1985, Gonzalez 1996a Surinam Aug-Oct Spaans 1975, Hancock et al. 1992 Guyana Aug-Oct Hancock et al. 1992 E Brazil (Isla Mexiana) Jul-Aug Hancock et al. 1992, Antas and Nascimento 1997 SW Brazil (Mato Grosso) Sep-Nov Hancock et al. 1992, Antas and Nascimento 1997 Bolivia Oct-Feb"* Dott 1984 NE Argentina (Corrientes, Chaco) Aug-Oct Kahl 1971, Hancock et al. 1992 3 Breeding dates only; no egg-laying dates given. ecology of Jabirus on the Pantanal of Brazil. Breeding and egg-laying dates have been pub- I lished for some populations of Jabirus (Table 1). Breeding dates are variable across the i range and seem to be influenced largely by s! seasonal rainfall patterns. Two published re- j! ports provide quantitative data on Jabiru ! breeding biology: Gonzalez (1996a) and Anas j and Nascimento (1997) for Venezuela and I Brazil, respectively. ' In Belize, the Belize Audubon Society I (BAS) has published much anecdotal infor- |( mation on Jabiru nesting and sightings since , 1969, but no comprehensive report exists for I its breeding biology. From 1969 to 1987, DW and the late WFY collected information on nest locations and breeding activities of Jabi- 1 rus in Belize, where the species has been of- ^ hcially protected since 1973. Our objective was to synthesize published and unpublished I information from reliable sources and compile I representative data lor Jabirus in Belize. We then present an analysis of the breeding biol- ogy of Jabirus in Belize based on those sourc- I es. ^ MKTIIODS I Stiu/y area. — Most Jabiru nests for our , study were located in the northern and central ' sections of Belize ( 17 10'- 18' 10' N: 89' 15'— 88'" 12' W; Fig. 1). Mean monthly tempera- i tures range from 16 to 17°C' in the winter wet season and from 24 to 25° C' in the summer I dry season. On average, the northern coastal plains (Corozal District) receive about one- third the rainfall (1,347 mm) of the south (4,526 mm, Toledo District). Seasonal effects are greatest in the central and northern re- gions, where January through April or May are dry (<100 mm per month). In south-cen- tral regions, the dry season (February to April) is shorter. A minor, less rainy period usually occurs in August (Hartshorn et al. 1984, Central Statistical Office 2000). Data sources. — Data for this study were gathered from four main sources: the unpub- lished field notes of DW (1968-1987), per- sonal communications with DW from 2001 to 2003, 44 reports published in the Belize Au- dubon Society Bulletin from 1969 through 1987, and several letters written by WFY to Charles S. Luthin summarizing the results of nine census flights conducted between 1985 and 1986. C. S. Luthin worked for the Brehm Fund for International Bird Conservation and was chairman of the World Working Group on Storks, Ibises, and Spoonbills (WWG-SIS). We also included several recent 2003 personal observations from Belizean ornithologist, O. A. Figueroa. Jabiru survey llights can be di\ided into two time periods: 1968—1981 and 1983—1987 ( fable 2). Between 1968 and 1981, we con- firmed 30 llights (- 22.0 hr) by WFY (Young 1998). Mights were conducted in a single-en- gine aircraft aiul based out of Belize City Mu- nicipal Airport. I'hese were low-altitude llights, often below 800 m, when nest contents were being observed. Nest locations (Appen- dix, big. 1 ) arc approximate, bo locate nest 144 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 FIG. 1. Locations of 36 Jabiru nests in Belize, 1968—1987. Numbers on map refer to nesting sites listed in Appendix. Barnhill et al. • BREEDING BIOLOGY OE JABIRUS 145 TABLE 2. Known flight dates for Jabiru surveys, 1968 to 1987% Belize. Season Flight dates 1968-1969 Mar-no specific dates reported 1969-1970 15 Nov, Dec-no specific dates reported, 15 Mar 1970-1972 No flights confirmed 1972-1973 24 Jan, 26 Jan, 2 Feb, 27 Mar 1973-1974 23 Nov, 24 Nov, 27 Nov, 6 Jan, 17 May 1974-1975 12 Nov, 16 Nov, 23 Dec, 30 Mar, 30 Apr 1975-1976 2 Dec, 22 Dec, 26 Jan, 4 Mar 1976-1977 7 Dec, 22 Dec, 26 Jan, 4 Mar 1977-1978 No flights confirmed 1978-1979 Four flights-no specific dates reported 1979-1981 Various flights-no specific dates reported 1981-1983 No flights confirmed 1983-1984" 25 Feb, 29 Apr-two flights each day 1984-1985^ 30 Jan, 31 Mar, 16 Apr, 1 1 May, 9 Jun, 23 Jun 1985-1986^ 17 Mar-two flights 1986-1987^ 26 Feb, 3 Mar, 8 Mar, 1 3 Mar, 29 Mar ^ Total flight time —22.0 hr, 1968-1981. ^ Total flight time = 1 1 .6 hr. Total flight time = 8.95 hr. Total flight time = 6.0 hr. ^ No flight times reported. sites, we referred to the aerial-flight (Fig. 2) and nest-location maps developed by WFY and DW from the WWG-SIS flights (1983- 1986) and DW’s notes. WFY had become per- sonally interested in Jabirus and periodically took flights to confirm nest sightings reported by charter pilots and the public. He also owned a real estate business and often located nests when flying clients. Flights between 1969 and 1981 that were not real-estate relat- ed were highly targeted and covered central and northern Belize almost exclusively. After Jabirus gained protected status in 1973, public radio announcements were made to increase awareness and to encourage reports of nest sightings and Jabirus to the BAS. Flights that were conducted between 1968 and 1982 were systematic, in that they covered areas and hab- itats where previous sightings had been re- ported. From 1983 to 1987, 12 of 15 Mights (26.6 hr) were linanced by WWG-SIS and Mown by J. Fuller in a Cessna 172, V3-1IFJ. 'fhese Mights covered predetermined routes (big. 2), but also included some point-to-iioinl irapline Mights within the delineated area, f light dates lor annual nest surveys between 1968 and 1987 are given in fable 2. No regular Mights were documented in BAS reports Tor surveys before 1984. Most flights were between November and June. Nests were most detectable early in the season when at least one adult was incubating eggs or attending young birds. Observers who often participated in these early flights were BAS members DW, M. Meadows, and B. Miller; flights after 1984 also included J. Car- negie, J. Waight, and C. S. Luthin. Observers scanned from both sides of the aircraft. They looked for nests that were known to exist in previous years and for nests reported by char- ter pilots and the public. When a nest was detected, the pilot would circle around the nest at lower altitude, often at only 100 m, so that observers could see nest contents with binoculars. When an adult Jabiru was sitting on a nest, the aircraft would circle until the bird stood up and allowed a clear view of nest contents. Nest size was estimated by compar- ing it to the size of an adult Jabiru. Nest-size estimates were made from both aircral't and vantage points on the ground. Data were available I'or 16 breeding seasons: no data were available for 1970-1972, 1981-1982, or 1982-1983. Flying in Belizean airspace was severely restricted during the latter two breed- ing seasons due to a military conMict with Guatemala. Dald analysis. — fo calculate reproductive success, tlata were considerctl reliable if they 146 THE WILSON BULLETIN • Vol. 1 17, No. 2, June 2005 LIG. 2. Designated census routes for Jabiru nest survey flights in Belize, 1984—1987. Barnhill et al. • BREEDING BIOLOGY OF JABIRUS 147 could be cross-referenced with BAS reports, i DW’s field notes, or WFY’s letters. Where these data exist for breeding seasons 1968/ j 1969 to 1986/1987, we have calculated total number of nests, active nests, eggs, nestlings, and mean clutch size. We calculated mean number of nestlings per nest for those nests with nestlings. Productivity was calculated as total number of nestlings per active nest (in- cluding nests with and without nestlings). Nests were considered to be active if adults appeared to be incubating, or if eggs or nest- lings were observed in the nests. The number I of young that successfully fledged could not be determined because nests were not moni- tored to fledging stage. Data represent the number of nestlings present at the nest. For the 1972-1973 breeding season, we were able to calculate number of eggs that hatched (hatching success) for four nests. A crude measure of overall hatching success (1968-1987) was calculated by dividing num- ! ber of nests where nestlings were observed by number of known active nests. In some years, nest data are missing; in other years, the num- ber of nestlings observed contradicts the total j number of nestlings reported by BAS, which may refer to the estimated number of young that fledged. Nest sites that could not be con- I firmed as either active or inactive were not included in our analysis. RESULTS Nest ohserx’citions. — A total of 144 nest ob- ' servations were made in 16 breeding seasons: 121 (84%) from aircraft and 23 (16%) from ’ the ground. The number of observations from 1 the ground ranged from 1 to 7 per nest and I the number of observations by aircraft ranged from 1 to 16. The mean number of observa- I tions per active nest was 2.4. Breeding behavior. — Jabirus appeared to I become more numerous in Belize near the end i of the rainy season (mid-November), possibly ' having moved from the Campeche area of I Mexico (Young 1983, Miller 1991). Both i males and females appear to participate in nest building, incubation, and care of young (DW pers. obs., (). A. Figueroa pers. obs.). During both incubation and when nestlings were present, one adult often remained on the nest while the other foraged (DW pers. obs.). Defense of nests against predators or other bird species was not observed. However, breeding pairs appeared to remain in isolated breeding territories until nestlings fledged (DW pers. obs.). Jabirus may exhibit intra- and interspecific territoriality near the nest and at feeding areas (Hancock et al. 1992, Gon- zalez 1996b). When nestlings are about 4 weeks old, parents tend to leave them unat- tended for longer periods of time (O. A. Fi- gueroa pers. obs.). Breeding dates. — In Belize, the breeding season appears to coincide with the transition from wet to dry season (November-Decem- ber). Most breeding occurs from mid-Decem- ber to May. Recent observations indicate that a few nests are still active in early June (O. A. Figueroa pers. obs.). Most eggs are prob- ably laid from December to February. Eggs seen in nests in Eebruary may have been laid during late January. Adults were observed standing on, constructing, or rebuilding nests as early as 16 November 1974. Earliest eggs were observed on 12 December 1973 and lat- est eggs were observed on 26 February 1987. Earliest nestlings were observed on 15 Janu- ary 1970, and nestlings were observed as late as 28 May 1973. Young birds usually fledged 100-115 days after hatching (Miller 1991; DW pers. obs.), although some young fledge prior to 100 days post-hatching (O. A. Eigu- eroa pers. obs.). Prior to finally abandoning the nest, young forage with their parents and continue to use the nest to roost. Successful Jabiru pairs are therefore involved in repro- ductive tasks for approximately 6-7 months. Nest sites. — Erom 1968 to 1987, a total of 91 nests was discovered, of which 36 differ- ent nests were considered active in one or more years (Table 3, Appendix, Fig. 1 ). Each had at least one nesting attempt, yielding a total of 69 active nests over the course of 19 breeding seasons (Table 3). During (he 1972- 1973 breeding season, there were nine active nests and in 1986-1987 there were seven, but in most years there were live or fewer. All nests were in isolated, tall, emergent trees with one exception (1 lattieville-Boom No. I ); this nest w'as constructed in an imusually tall group of palmetto palms {Acoelorriiaphe wrightii: Appendix, lug. 1 ). Canopy height ranged from 10 to 30 m. We were able to itlentify the species of nest substrate for 12 of the 36 nests; Cedni pentandra (5), Idnus car- 148 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 TABLE 3. Reproductive success of Jabirus in Belize during 1968- 1987 breeding seasons. Season 1968-1969 1969-1970 1970-1971 1971-1972 1972-1973 1973-1974 1974-1975 1975-1976 Total nests'* 2 4 4 — 9 9 8 8 Active nests** 2 3 2 — 9 5 5 6 Nests with eggs 2 3 2 — 6 4 3 3 Mean clutch size — — — — 4.0 (4P 2.5 (2) 5.0 (1) 3.0 (1) Nests with young 2 3 2 — 7 2 3** 1 Mean no. young 2.0 (2/ 2.0 (3) 2.0 (2) — 2.1 (7) 1.5 (2) 2.0 or 2.0 (1) Total young 4 6 4 — 15 3 6 2 Hatching success (%) — — — — 43.8 — — — Crude hatching success 100 100 100 — 78 40 44g 16 ^ Total nests: active or inactive. Nests with eggs, nestlings, or incubating adults. These nests were not considered when calculating crude hatching success because no nestlings were ob.served in them. Number of nests where clutches were counted. ^Two of three nests were considered when calculating crude hatching success (the third nest was poached), f Number of nests where nestlings were counted. g Three nests were counted with nestlings, but one nest was destroyed before chicks fledged (that nest was not included in the calculation). ibaea (5), Tabebuia ochracea (1), and pal- metto palm (1). Three nests were found in un- identified dead trees. Nest trees were usually surrounded by riparian forests or seasonally inundated pine-savanna wetlands situated in transitional zones where pine savannah meets coastal lowlands; often nest trees were within seasonally flooded or permanent freshwater lagoons. The many coastal and inland lagoons in north-central and coastal areas of Belize provide nesting and foraging habitats; how- ever, no nests were observed in mangrove- dominated areas. All nests were >1 km from mixed colonies of other bird species or other Jabiru nests. Construction and structure of nests. — De- cember and January appear to be the months when most nests are refurbished or new ones are built. Nests were usually 15-30 m above ground and were well supported in tree crotches. Nests often appeared deeper than wide. Nests were up to 1 m wide and 1.8 m deep, but most nests were as wide as they were deep. Each nest consisted of various siz- es of sticks and other woody debris (although, to avoid disturbing the birds, no one climbed the nest trees to examine nest structures close- ly). Nests were continually refurbished throughout the breeding season and remained relatively flat on top (DW pers. obs.). Several nests appeared to be used for many years. The Mucklehany Lagoon nest was dis- covered in 1968 and was last reported active in 1979. Two hurricanes, Francelia in 1969 and Fifi in 1974, defoliated the nest tree. New nests were subsequently built in the same tree. The Bocotora Pine Ridge nest discovered in 1973 was last reported active in 1984 (Ap- pendix, Fig. 1). Clutch size. — Available data from 1968 to 1987 indicated a total of 44 eggs in 14 nests. Mean clutch size was 3.14 ± 1.17 SE (range = 1-5 eggs; /? = 14 nests). Most eggs were laid in January. Hatching and nesting success. — Hatching success could be calculated only for the 1972- 1973 breeding season. Four nests with eggs were visited again when young were present. Sixteen eggs produced 7 nestlings, resulting in a hatching success of 43.8%. For the 14 years that crude hatching success (nestlings per active nest) could be calculated, 71.7% (43 of 60) of all active nests had at least one nestling present. A total of 92 nestlings was counted in 60 active nests, or 1.53 nestlings per active nest. The mean number of nestlings per nest with nestlings was 2.13 ± 0.71 SE (range = 1-4 nestlings; n = 43 nests). Most young were observed in February and March. DISCUSSION Gonzalez ( 1 996a) reported that mean clutch size of Jabirus in Venezuela was 3.4 eggs, somewhat higher than the mean of 3.14 that we calculated in Belize. In a separate report (Young 1983), WFY and DW reported a mean clutch size of 4.1 eggs (range = 3-5 eggs; n = 19 nests) in Belize. In Brazil, Antas and Nascimento (1997) reported a clutch size of 3-4 eggs. Hatching success was calculated for Barnhill et al. • BREEDING BIOLOGY OE JABIRUS 149 TABLE 3. Extended. 1976-1977 1977-1978 1978-1979 1979-1980 1980-1981 1981-1982 1982-1983 1983-1984 1984-1985 1985-1986 1986-1987 Totals 6 1 6 3 2 — — 6 7 6 10 91 4 1 6‘= 3‘^ 2 — — 5 5 4 7 69 (60) 4 1 3 — 2 — — 4 — 1 1 39 2.0 (2) 3.0 (1) — — — — 3.0(1) — 3.0 (1) 2.0 (1) — 2 1 — 2 — — 5 5 3 6 44 (43) 2.5 (5) 2.0 (1) — — 2.0 (2) — — 3.0 (5) 2.6 (5) 1.3 (3) 1.5 (6) — 5 2 — — 4 — — 15 13 4 9 92 — — — — — — — — — 50 100 — — 100 — — 100 100 75 86 — only one breeding season in Belize (43.8%) and, over a 14-year period, crude hatching success was 71.7%. Although no fledgling data were collected in Belize, 47.0 and 47.6% of active nests produced at least one chick to fledgling age for two separate years in Vene- zuela (Gonzalez 1996a). Overall productivity per nest was higher in Belize (1.53) compared with 0.94 and 1.00 for the 2 years in Venezuela reported by Gonzalez (1996a); however, his productivity measure was based on young per active nest that fledged, so the figures are not directly com- parable. The mean number of nestlings per ac- tive nest was approximately the same in Be- lize (2.13) as it was during both years in Ven- ezuela (2.0 and 2.1). In Brazil, mean number of nestlings per nest varied from a peak of 1.05 in 1988 to a minimum of 0.16 in Novem- ber of 1992 (Antas and Nascimento 1997). In a separate report (Young 1983), WFY and DW found mean nestlings per active nest to be 2.18 (range = 1-4; n = 22 nests) in Belize. Based on documented reports, the main causes of the nest failures in Belize were hu- man disturbance and nest trees being cut down by poachers (6 nests). Other nest failures were due to nest trees falling (4 nests), agricultural clearing (4 nests), and fire (1 nest). No pre- dation was observed. Before Jabirus were of- ficially protected in 1973, they were called “market birds” and nestlings, in particular, were hunted and their meat sold in markets. Public reports of poaching increased after the inlUix of refugees from (iuatemala began in the early 1980s (1)W pers. comm.). As is the case in Vcne/ucla, the breeding season for .labirus in Bcli/c appears to coin- cide with the end of seasonal rainlall. In the llanos of Venezuela, fhomas (1985) rcportctl that breeding of Wood Storks (Mycteria amer- icana), Maguari Storks (Ciconia maguari), and Jabirus can be understood only within the context of variations in both timing and quan- tity of rainfall. The breeding season began just before the rains ended (September-October in Venezuela and November-December in Be- lize). Jabiru breeding dates in the Pantanal of Brazil varied, but were generally between ear- ly July and mid-August, with young leaving nests between October and early December. Water levels begin to fall in the Pantanal plain in May and June. Variations were noted even within one drainage basin, Taquari, where nests in the higher-elevation areas were active earlier than nests located in lower areas of the basin (Antas and Nascimento 1997). Nestling productivity in Brazil was likely related to flood levels, as the two fish species most often fed to nestlings were found in small bodies of water during low-water periods. Many popu- lations of storks, including Jabirus, respond to the seasonal rainfall (Campbell and Lack 1985). In Brazil, this seasonal variation is ex- pressed as volume of rain falling at river head- waters and that falling on the plains surround- ing the Pantanal. The distribution of rain dur- ing the season directly influences both the to- tal flooded area and the speed at which water levels rise and fall (Antas and Nascimento 1997:103). In north-central Belize, Crooked Tree Wild- lil'e .Sanctuary (C'fWS), a complex of per- manent and seasonal shallow, freshwater la- goons and marshes, is a critical area for mi- gratory and non-migratory water birds, in- cluding .labirus. .Some lagoons regularly dry up by the end of the dry season (March to May). Other lagoons are as deep as 3 m and retain water year around. Most observations 150 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 indicated that by mid-June very few adult or juvenile Jabirus remained in Belize. At this time, Jabiru populations are reported to in- crease in the Usumacinta drainage in Mexico, where they may possibly overwinter until the next breeding season (Luthin 1984, 1987; Miller 1991; Howell and Webb 1995; DW pers. comm.); no studies have confirmed whether birds from Belize winter there. It is uncertain, but Jabirus may become more dis- persed as rising water levels make major wet- lands less attractive for foraging but create new foraging opportunities in more isolated areas. Many species of storks exhibit regional movements. These are dispersal events, not true migration, and are probably related to both timing and quantity of rainfall (Campbell and Lack 1985, Thomas 1985). Jabirus begin appearing in Belize during November and De- cember, possibly arriving from the Campeche area of Mexico (Luthin 1984, 1987; Miller 1991; Howell and Webb 1995; Frederick et al. 1997). Birds move to locations where surface water conditions appear to favor optimum feeding. In Belize, during March and April when most young have fledged, water in la- goons and marshes becomes locally concen- trated. Availability of food may be the single, most important factor that regulates move- ments of most storks, including Jabirus. It may also influence breeding success. The low- est nestling productivity in Brazil was report- ed during years of lowest rain fall (Antas and Nascimento 1997). A second example is that seasonal rains dictate timing and nesting suc- cess of Wood Stork populations in Florida: up to one-half of the total Wood Stork population may not nest in years when water conditions do not provide adequate food (Campbell and Lack 1985). The numbers of adult Jabirus aggregating in lagoons at the termination of each breeding season were always much greater than the numbers known to be nesting (DW pers. obs.). In 1969 when DW first began keeping re- cords, she recorded a group of 14 Jabirus (composed mostly of adults) at Mexico La- goon on mud flats in mid-May. The numbers of Jabirus congregating at CTWS has in- creased: 14 in May 1970; 17 in June 1971 (Weyer 1971); 23 in June 1985 (Waight 1986); and 27 in March 1987 (Craig 1987). In recent years (Waight and Beveridge 1991) at CTWS and adjacent Western Lagoon, as many as 40 and 49 Jabirus were observed in May and June 1991, respectively. In late May 1993, 50 Jabirus were observed at Northern Lagoon within CTWS (Young 1998). These observa- tions indicate that there may be more Jabirus nesting in Belize than we report, because all nests are not equally observable (i.e., nests lo- cated inside the crowns of live trees or in low- er parts of dead trees surrounded by leafy trees). These “extra” birds may represent a non-breeding group, which may be character- istic of long-lived birds that do not become reproductively active before the age of 4 years. These Jabirus could constitute a signif- icant percentage of the population (O. A. Fi- gueroa pers. comm.). Most nest trees (32 of 36) were located in wetlands of northern and central Belize (Ap- pendix, Fig. 1). This includes those in marshes along the lower New River, Crooked Tree La- goon, Burrell Creek Lagoon, Mussel Creek, Big Falls Rice Ranch, Cox’s Lagoon, and Muckelhany Lagoon. At least three nest trees were located within 1-5 km of the interna- tional airport in Ladyville, and south of the Sibun River to Northern Lagoon and Southern (Manatee) Lagoon in the Peccary Hills. Other locations include Laguna Seca, Monkey River south to Punta Ycacos Lagoon, upper Mojo River, Aguacaliente Swamp, and Mafredi La- goon in Toledo District. DW (in Scott and Carbonell 1986) provided general site descrip- tions and status of these wetlands. In Belize, Jabirus built nests far from other wading-bird nests. They were never observed nesting in close proximity to Wood Storks and only once, in May 1978, was a colony of Boat-billed Herons (Cochlearius cochlearius) observed within a few hundred meters of a Jabiru nest at Blue Creek Village nest (Ap- pendix, Fig. 1). DW’s 1985 observations in the llanos of Venezuela (Masa Guaral) and Naumburg’s (in Kahl 1971) observations in Mato Grosso, Brazil, indicated that Jabirus nested within colonies of Wood Storks and other Ciconiiformes. Gonzalez (1996a) found three Jabiru nests in the center of mixed-spe- cies colonies in Venezuela. Luthin (1984) found one Jabiru nest in a mixed-species col- ony in Mexico. Some nests were built in tall red mangroves (Rhizophora mangle) in coastal Barnhill et al. • BREEDING BIOLOGY OE JABIRUS 151 areas of southern Mexico. In Brazil, both sex- es of Jabiru have been observed defending the nest and surrounding area from other Jabirus and Wood Storks (Antas and Nascimento 1997). Inter- and intraspecific kleptoparasitism I was a very common behavior during the late I dry season in the llanos of Venezuela (Gon- zalez 1996b), and Jabirus exhibited territori- : ality throughout the nesting season (Kahl 1 1973, Thomas 1985). In Belize, DW rarely observed behavior during the breeding season that she considered territorial defense of food resources. Beginning in April, small groups of mostly adult Jabirus congregated in freshwater marshes, ponds, and lagoons where food re- I sources may have become concentrated during the dry season (DW pers. obs.) These areas were termed “staging” areas by DW, as very few Jabirus were observed during the non- I breeding season in Belize. It is unknown — but I suggested — that Jabiru populations of Central America may move seasonally between Mex- ! ico, Belize, and Guatemala (Correa and Luthin ! 1988; DW pers. comm.). Other reports (Og- den et al. 1988, Villarreal 1996) suggest that seasonal influxes may occur in various regions of Central America. In Venezuela, Gonzalez (1996a) reported that nestlings remained on nests from 84 to 93 days, but that fledglings remained near the nest for several weeks afterward, in many cas- es returning to the nest at night. In Belize, young birds remain in the nest or near the nest for 100-115 days. Successful Jabiru pairs in all three countries (Belize, Brazil, and Vene- zuela) are involved in reproductive tasks for approximately 7 months and may have diffi- culty breeding in successive years; there is, however, some evidence that Jabiru pairs may remain mated in successive seasons (Kahl 1973, Thomas 1985, Gonzalez 1996a). Gon- zalez (1996a) indicates that less than half of all active pairs in one season are also active during the following season, and that only 25% of successful pairs are successful in a second consecutive season. Overall, Jabiru jx)pulations may have in- creased in Belize since gaining protective sta- tus in 1973. In the early 1970s, the Belize Au- dubon Society had estimated the population to 1 be 20-30 birds, but by 1993, the population ] was estimated to be 50-60 birds (Young 1998). By 2002, 102 Jabirus had been countctl in the major wetlands of Belize (O. A. Figu- eroa pers. comm.). ACKNOWLEDGMENTS Brehm Fund for International Bird Conservation and World Working Group on Storks, Ibises, and Spoon- bills (WWG-SIS) helped finance annual surveys of Jabiru from 1984 to 1986. O. A. Figueroa, University of Florida, reviewed the manuscript and supplied in- formation about current Jabiru populations in Belize. We also appreciate and acknowledge the generous re- views of this manuscript by Jose A. Gonzalez and two anonymous referees. We thank J. Waight, first presi- dent of the Belize Audubon Society, for his vision, encouragement, and ready support during the forma- tive years of the BAS. LITERATURE CITED Antas, R T. Z. and I. L. S. Nascimento. 1997. Tuiuiu: under the skies of the Pantanal; biology and con- servation of the Tuiuiu, Jabiru mycteria. Empresa das Artes, Sao Paulo, Brazil. Bent, A. C. 1926. Jabiru. Pages 66-72 in Life histories of North American marsh birds. U.S. National Museum Bulletin, no. 135. [reprinted 1963, Dover Publications, New York] Blake, E. R. 1977. Manual of Neotropical birds, vol. 1 . University of Chicago Press, Chicago, Illinois. Campbell, B. and E. Lack (Eds.). 1985. A dictionary of birds. Buteo Books, Vermillion, South Dakota. Central Statistical Office. 2000. Environmental statistics for Belize. Central Statistical Office, Ministry of Finance, Belmopan, Belize. Correa, J. and C. S. Luthin. 1988. Proposal for the conservation of Jabiru stork in southeast Mexico. Pages 607-615 in Memoria del simposio sobre la ecologia y conservacion del Delta de los Rios Usamacinta y Grijalva. Instituto Nacional de In- vestigacion sobre Recursos Bioticos, Division Re- gional, Tabasco, Mexico. Craig, M. 1987. A field trip to Crooked Tree. Belize Audubon Society Bulletin (April ):5-6. Doit, H. E. M. 1984. Range extensions, one new re- cord, and notes on winter breeding birds in Boliv- ia. Bulletin of the British Ornithologists' Club 104: 104- 109. Pki-:di-;rick, P. C., J. C. Sandovai., C. Luthin, and M. Spalding. 1997. The importance of the Caribbean coastal wetlands of Nicaragua and Honduras to C'entral American populations of waterbirds and .labiru Storks (Jabiru mycteria). Journal of Field Ornithology 68:287-295. Gon/ali,/, j. a. 1996a. Breeding bii)logy of the Jabiru in the southern llanos ot Vene/ucla. Wilson Bul- letin 108:524 534. CiON/Aii/. .1. A. 1006b. Kleptoparasitism in mixed- species loraging Hocks of w ailing birds iluring the late ilry season in the llanos of Vene/uela. C'olo- nial Waterbirds 10:226 231. IIWKK K.J. A...I. A. Kl SHI AN. AND M. P. KaHL. 1002. 152 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 Storks, ibises and spoonbills of the world. Aca- demic Press, London, United Kingdom. Hartshorn, G. S., L. Nicolait, L. Hartshorn, G. Bevier, R. Brightman, J. Cal, A. Cawich et al. 1984. Belize country environmental profile. Trejos Hermanos Sucesores S. A., San Jose, Costa Rica. Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford, United King- dom. Kahl, M. P. 1971. Observations on the Jabiru and Ma- guari storks in Argentina, 1969. Condor 73:220- 229. Kahl, M. P. 1973. Comparative ethology of the Ci- coniidae, part 6. The Blacknecked, Saddlebill, and Jabiru storks (Genera Xenorhynchus, Ephippio- rhynchus, and Jabiru). Condor 75:17-27. Knoder, C. E., P. D. Plaza, and A. Sprunt, IV. 1980. Status and distribution of the Jabiru Stork and oth- er water birds in western Mexico. Pages 58—127 in Proceedings of the National Audubon Society’s symposium on the birds of Mexico (P. P. Schaeffer and S. M. Ehlers, Eds.). National Audubon Soci- ety Western Education Center, Tiburnon, Califor- nia. Luthin, C. S. (Compiler). 1984. World working group on storks, ibises and spoonbills, report 2. Brehm Fund for International Bird Conservation, Vogel- park Walsrode, West Germany. Luthin, C. S. 1987. Status and conservation priorities for the world’s stork species. Colonial Waterbirds 10:181-202. Miller, C. M. 1991. Belize’s celebrity stork: two de- voted naturalists struggle to save the Jabiru. Bird- er’s World (June):36-39. Ogden, J. C., C. E. Knoder, and A. Sprunt, Jr. 1988. Colonial waterbird populations in the Usamacinta Delta, Mexico. Pages 565-605 in Memoria del simposio sobre la ecologia y conservacion del Delta de los Rios Usamacinta y Grijalva. Instituto Nacional de Investigacion sobre Recursos Bioti- cos. Division Regional, Tabasco, Mexico. PovEDA, M. G. 2003. El comportamiento de Jabiru mycteria durante la epoca reproductiva en hume- dales de la zona norte de Costa Rica. Boletm Ze- ledonia 7(1), Junio, San Jose Costa Rica. www.zeledonia.org/files/boletin.html (accessed 1 January 2004). Scott, D. A. and M. Carbonell (Compilers). 1986. A dictionary of Neotropical wetlands. Internation- al Union for Conservation of Nature and Natural Resources (lUCN) Cambridge, and International Waterfowl Research Bureau (IWRB) Slimbridge, United Kingdom. Spaans, a. L. 1975. The status of the Wood Stork, Jabiru, and Maguari Stork along the Surinam coast. South America. Ardea 63:116-130. Stotz, D. E, j. W. Fitzpatrick, T. A. Parker, III, and D. K. Moskovits. 1996. Neotropical birds: ecol- ogy and conservation. University of Chicago Press, Chicago, Illinois. Thomas, B. T. 1981. Jabiru nest, nest building and quintuplets. Condor 83:84-85. Thomas, B. T. 1985. Coexistence and behavior differ- ences among the three western hemisphere storks. Ornithological Monographs 36:921-931. Villarreal, J. 1996. Estado actual, ecologia trofica, y uso de habitat del Jabiru {Jabiru mycteria) en tres humedales de la cuenca baja del Tempisque, Costa Rica. M.Sc. thesis, Universidad Nacional, Here- dia, Costa Rica. Villarreal-Orias, j. 1998. A new nesting record for the Jabiru in Costa Rica. Colonial Waterbirds 21: 256-257. Waight, L. 1986. Report on field trips, Christmas Bird Counts and Jabiru sightings. Belize Audubon So- ciety Bulletin (January): 1-6. Waight, L. and J. Beveridge. 1991. A very good year for Jabiru. Belize Audubon Society Bulletin ( April-June): 13-16. Weyer, D. 1971. The Jabiru. Belize Audubon Society Bulletin (June):2. Young, W. F. 1983. Jabiru nesting in Belize. Belize Audubon Society Bulletin (May): 1-2. Young, W. F. 1998. The Jabiru Stork. Belize Audubon Society Bulletin (October-December):8, 11. Barnhill et al. • BREEDING BIOLOGY OE JABIRUS 153 APPENDIX. Jabiru nest numbers, names, and first breeding season discovered in bers refer to locations shown in Eigure 1 . Belize, 1968-1987. Num- Nest No. Nest name Season discovered 1 Mucklehany Lagoon 1968-1969 2 Northern Lagoon 1968-1969 3 Hattieville 1969-1970 4 Mason’s Earm/Cabbage Haul Swamp 1969-1970 5 Hattieville-Boom No. 1 1970-1971 6 Sibun River 1972-1973 7 Hill Bank at Dawson Creek 1972-1973 8 Perry Camp No. 1 1972-1973 9 Bocotora Pine Ridge 1972-1973 10 Orange Walk Town No. 1 1972-1973 1 1 Ship Yard Village 1972-1973 12 Laguna Seca 1972-1973 13 Guinea Grass 1973-1974 14 Perry Camp No. 2 1973-1974 15 Spanish Creek and Southern Lagoon 1973-1974 16 Hattieville Boom No. 2 1975-1976 17 Mexico Lagoon 1975-1976 18 Isabella Bank 1975-1976 19 Burrel Boom (Tenn Ag) 1975-1976 20 Dawson Creek 1986-1987 21 Blue Creek Village 1977-1978 22 Dandriga Nest 1978-1979 23 Back Landing 1978-1979 24 International Airport 1979-1980 25 Lemonal Nest 1979-1980 26 Orange Walk No. 2 1983-1984 27 Spanish Creek 1983-1984 28 Double Headed Cabbage 1983-1984 29 Mojo Swamp 1983-1984 30 Indian Church 1985-1986 31 San Antonio Village 1983-1984 32 Irish Creek 1986-1987 33 Black Creek House 1986-1987 34 Revenge Lagoon 1986-1987 35 Mullins River 1986-1987 36 Mango Larm-Monkey River 1986-1987 Wilson Bulletin I 1 7(2): 1 54-164, 2005 ABUNDANCE, HABITAT USE, AND MOVEMENTS OE BLUE- WINGED MACAWS {PRIMOLWS MARACANA) AND OTHER PARROTS IN AND AROUND AN ATLANTIC FOREST RESERVE BETH E. I. EVANS,'-2 JANE ASHLEY,' AND STUART J. MARSDEN' ABSTRACT. — The Blue-winged Macaw {Primolius maracana) has disappeared from most of southern Brazil, Argentina, and Paraguay; its remaining southern stronghold is the 2,179-ha Caetetus Reserve, Sao Paulo state, Brazil. We estimated the macaw’s population inside the reserve (88 individuals) and examined how it and other parrots use the extra-reserve landscape, which is dominated by coffee plantations and pasturelands. Flight activity of the macaw and Scaly-headed Parrot {Pionus maximiliani) declined with distance from Caetetus, although many macaws flew to the vicinity of the reserve to roost. Two other species, Canary-winged Parakeet (Brotogeris versicolurus) and White-eyed Parakeet {Aratinga leucophthalmus), used the landscape independent of the reserve itself. We recorded parrots in 90% of our 1-km^ study plots outside (<12 km) the reserve, but no species was recorded using pasture, coffee or rubber/orange plantations, or scrub habitats, which composed 80% of the landscape around the reserve. Only four habitat types were used by any species. Primary and secondary forests were the habitats most preferred; Eucalyptus plantation habitat was the only totally anthropogenic habitat used. Clearly, protection, and preferably augmentation, of forest cover around Caetetus may be crucial for the macaw’s survival at this important site. Received 2 March 2004, accepted 11 January 2005. Habitat fragmentation has affected a mul- titude of taxa worldwide (e.g., Saunders et al. 1991, Turner 1996) by disrupting forest dy- namics (Laurance et al. 1998) and adversely affecting floras and faunas (Alzen and Fein- singer 1994, Dale et al. 1994). Surprisingly, few studies have examined the effects of frag- mentation on large frugivorous birds such as parrots, hornbills, and toucans. These birds are among the most threatened in the world (BirdLife International 2000) and often dis- appear from small fragments (e.g., Willis 1979). On the other hand, many are also high- ly mobile, which may allow them to disperse to areas within fragmented landscapes (e.g., Rowley 1983, McNally and Horrocks 2000). The ability of a given species to use the mosaic of different habitats found outside of reserves (extra-reserve landscape) may affect its future survival, which makes this an im- portant topic for research. Agro-ecosystems cover the vast majority of land outside pro- tected areas (Western and Pearl 1989), which could have important influences on species ecology (Mesquita et al. 1999, Bentley et al. ' Applied Ecology Group, Dept, of Environmental and Geographical Sciences, Manchester Metropolitan Univ., Chester St., Manchester, Ml 5GD, United King- dom. 2 Corresponding author; e-mail: bethelen70@hotmail.com 2000) and survival (Laurance 1991, Gascon et al. 1999). A species’ ability to use the extra- reserve landscape may be especially important around protected areas or other habitat frag- ments, as dispersal into the extra-reserve land- scape might boost local populations (e.g., Ricketts et al. 2000). In the case of large avian frugivores, which tend to occur at low popu- lation densities (e.g., Marsden 1999), it is un- known whether protected areas can support viable populations of some taxa, especially in small reserves (e.g., Gurd et al. 2001). Ex- amination of landscapes adjacent to reserves or other “key patches” (Verboom et al. 2001), and improving extra-reserve habitat suitability for threatened taxa, may be a first step toward enhancing populations in and around protect- ed areas, or at least buffering within-reserve populations from negative outside influences (e.g., Gotmark et al. 2000). The problem of forest fragmentation is acute in Brazil’s Atlantic Forest, where re- maining forest cover is —7.5% of the original 1 million km^ (Morellato and Haddad 2000, Myers et al. 2000). Deforestation has been particularly intense in the interior of Sao Pau- lo state; aside from the relatively large Morro do Diabo State Park, the few small fragments of forest that remain are isolated by vast areas of sugar cane and other agricultural land (e.g., Cullen et al. 2001). One of these fragments is 154 Evans et al. • ECOLOGY OF BRAZILIAN PARROTS 155 the Caetetus Reserve (2,179 ha), situated near Gar^a. The reserve is surrounded by an extra- reserve landscape dominated by pasturelands and coffee plantations, but which also con- tains small areas of remnant and degraded for- est, along with plantations of Eucalyptus spp. and citrus fruits. The reserve holds Sao Pau- lo’s largest remaining population of the Blue- winged Macaw (Primolius maracana; former- ly placed within Ara or Propyrrhura but now assigned to Primolius, Tavares et al. 2004), a species classified as “Vulnerable” (BirdLife International 2000). This species (body length = 39 cm) has disappeared from many of the protected areas in the southern part of its I range (M. F. Nunes unpubl. data). Six other i parrot species survive in the area (body lengths from Juniper and Parr 1998): White- eyed Parakeet {Aratinga leucophthalmus), 32 cm; Maroon-bellied Parakeet {Pyrrhura fron- talis), 25-28 cm; Blue-winged Parrotlet {For- pus xanthopterygius), 12 cm; Canary-winged Parakeet {Brotogeris versicolurus), 25 cm; Scaly-headed Parrot (Pionus maximiliani), 27 cm; and Blue-fronted Parrot (Amazona aesti- va), 37 cm. Our objectives were to (1) estimate popu- lation sizes of Blue-winged Macaws and other parrot species within the reserve, (2) examine parrot use of the extra-reserve landscape, and (3) determine which features of the extra-re- serve landscape influence parrot use. We then used these results to make a preliminary as- sessment of the likely viability of parrot pop- ulations in the area and to suggest which fea- tures of the landscape should be preserved or [ enhanced to protect parrots. METHODS Study area. — The study was based in and around Caetetus Ecological ,Station, ,Sao Paulo state, Brazil (22° 24' S, 49° 42' W; Pig. 1 ). The reserve covers 2,179 ha and consists i mainly of mature, semi-deciduous forest (the , area has been protected from major logging ' for ~3() years) and some areas of more re- ' cently disturbed secondary forest. Addition- ally, there are much smaller areas dominated by stands of bamboo and pal mi to {Euterpe ed- idis), and some small artificial lakes (Fig. I ). Annual precipitation averages 1.260 mm ((Til- len et al. 2001). fhe stutly was conductetl to- ward the end of the dry, cool season (May to September) in the plateau region of Sao Paulo. The landscape surrounding Caetetus is domi- nated by pasturelands and coffee plantations (Table 1), although fragments of degraded and regenerating forest and riverine forest also oc- cur outside the reserve. Within-reserve study. — We censused parrots in July and August 2001. The identification of parrot species, by both sight and call, and es- timation of their distances from census points, was practiced for 10 days before starting the study. We established 90 parrot census points at 200-m intervals along nine transects. Cae- tetus has an existing network of narrow “re- search” trails covering much of the reserve and all points were placed along these trails (Fig. 1). We sampled each census point six times — three times between 07:30 and 10:00 (UTC- 03) and three times between 14:30 and 17:00 — giving a total of 540 samples. Point counts commenced immediately upon reach- ing the point and lasted 5 min; any parrots observed close to the census point as the ob- server approached the station were also re- corded. We recorded parrots within 50 m of the census point. For each parrot, we recorded the species, group size, whether it was flying or perched, the time it was seen or heard, and an estimate — or in some cases an actual mea- surement— of the distance from point to par- rot. Within a 40-m radius of each census point, we measured several habitat variables. We chose a 40-m rather than 50-m radius for ease of data collection and because only a small proportion of panot records were expected at distances of 40-50 m away from the observer. We recorded the number of dead standing trees and the circumference at breast height of the five largest trees. Trees on which the first major branch was at or above half the tree's height were categorized as “primary-forest" trees, as they had probably grown under a full canopy. JVees branching below half their height, those with scars from dropped branch- es, or those showing vertical growth of branches near their base, were categorized as “secondary-forest" trees, fhe distance of each point to the nearest forest edge and the nearest river or lake was determined from (ilobal Positioning System (GPS) coordinates aiul maps. 156 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 ■ Secondary forest ■ Primary wet forest Streams □ Bamboo and edge effects m Habitat census and point watch site LIG. 1 . Map of Caetetus Ecological Station, Sao Paulo state, Brazil, showing broad habitat types and census points within the reserve. Extra-reserve study. — Habitat use and movements of parrots outside the reserve were studied in seventy 1- X 1-km plots located within a 12-km radius of the center of the Caetetus Reserve, thus composing 16.3% of the extra-reserve landscape within the 12-km- radius circle (Fig. 2). Thirty-five study plots were chosen randomly, then each was paired with a second, adjacent plot. Each pair of plots thus composed a 1- X 2-km rectangle Evans et al. • ECOLOGY OF BRAZILIAN PARROTS 157 TABLE 1. Percentage cover and main vegetation types of habitats found in the extra-reserve landscape around Caetetus Ecological Station, Sao Paulo state, Brazil (2002). Habitat type Percentage cover Dominant vegetation/species Pasture 42.0 Various grass species ! Coffee plantation 33.0 Cojfea spp. Riverine forest 8.0 Calophyllum brasiliensis Primary forest 6.0 Peroba spp., Talauma ovata Secondary forest 4.5 Gallesia spp., Cecropia spp. ' Scrub 2.9 Ormosia arborea, Cecropia spp. Eucalyptus plantation 2.1 Eucalyptus spp. Rubber/orange plantation 1.1 Hevea brasiliensis. Citrus spp. with the long axis facing (i.e., <45° from) the nearest part of the reserve (Fig. 2). During July and August 2001, parrot move- I ments and habitat use in each plot were re- corded (one observer per plot) during one day I between 07:00 and 10:30 and again between I 15:00 and 17:30. Observer position within a plot was determined by the best view afforded of the plot (but all points were within 200 m of the plot’s perimeter); because the landscape around Caetetus is gently rolling, it was pos- sible to find points at which the view over each plot was practically complete. During each survey, we recorded the parrot species, group size, time of entry into the plot, flight direction, and type of habitat used. t lCi. 2. I hc landscape aromul C'actetus Ixological Station. Sao Paulo state, Brazil, riie circle represents the study area within 12 km of the center of the reserve. Also shown are I - X 1-km stiuly plots (hatched) and extra- reserve forest remnants (black). Areas in jzray are outside the stiuly area. 158 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 A vegetation survey was carried out in each square on the day of the parrot survey. Four 1,000-m transects were placed parallel to each other at 200, 400, 600, and 800 m across each plot, providing 4 km of transect per plot. One observer (BE) walked the transects, recording with a GPS the total length of each of 1 1 hab- itat types. Habitat types contributing >1% of total habitat measured are shown in Table 1; the other habitats were bamboo, marsh, and buildings. Natural forests were classified as primary forest if there was little evidence of disturbance and the canopy was closed (these areas were usually fenced off), or as second- ary forest if there was evidence of much heavier disturbance (logging, fire, and grazing by cattle) and/or the canopy was discontinu- ous. We calculated a habitat-richness variable for each plot by summing the number of hab- itat types. From digitized maps, we calculated three measures of connectivity between each plot and the Caetetus Reserve. Distance to the re- serve (DIST) was calculated as the distance from the plot to the nearest edge of the re- serve. Percentage of forested land between the plot and the reserve (FOREST) was calculated as the percentage of the DIST vector that tran- sected natural forest (primary, secondary, or riverine forests). Finally, an index of forest gap (GAP) between the plot and the reserve was calculated as the greatest distance be- tween adjacent areas of forest along the DIST vector, divided by DIST. To determine whether extra-reserve habitats were geographically clumped (which could in- fluence extra-reserve landscape use by par- rots) and whether we could treat paired plots as independent of one another, we tested for spatial autocorrelation in habitat measures be- tween paired plots. Specifically, we ascer- tained whether adjacent plots were more sim- ilar to each other than they were to randomly selected plots with respect to eight habitat/ landscape variables: percent primary forest, secondary forest, scrub, pasture, coffee, and Eucalyptus, as well as DIST and FOREST. First, we calculated — for each variable — the difference between paired plots by subtracting the smaller value from the greater value. Sec- ond, we calculated this difference between one of the two original plots (randomly se- lected) and one of the other 68 plots (random- ly selected). We then compared the paired anc random differences using Wilcoxon signec ranks tests {n - 70). Data analysis. — Three parrot species — Ma- roon-bellied Parakeet, Blue-winged Parrotlet, and Blue-fronted Parrot — composed only 1.2% of parrots recorded in the extra-reserve landscape and were excluded from data anal- ysis. This left four species for analysis: Blue- winged Macaw, Scaly-headed Parrot, White- eyed Parakeet, and Canary-winged Parakeet. All four species were found outside the re- serve, but only macaws and Scaly-headed Par- rots were recorded at census points inside the reserve. Habitat associations of parrots inside the re- serve were examined by testing for differenc- es between habitat/landscape variables at “positive” census stations (species present on any of the six surveys) and “negative” sta- tions (species absent). We used independent t- tests for habitat variables that were normally distributed, and Mann-Whitney //-tests for those with non-normal distributions. We used Program DISTANCE (Buckland et al. 2001) to calculate density estimates for the two species (Blue-winged Macaw and Scaly- headed Parrot) recorded in the reserve. Re- cords were entered in clusters, and density es- timates were based on mean group size unless size-bias regressions of group size against dis- tance were significant at P < 0.10, in which case group size was adjusted by DISTANCE. Records of parrots in flight were excluded from the analysis, as aerial records clearly vi- olate a key assumption of distance sampling (Marsden 1999). Data were converted to 4-5 bands for analysis. No right-hand truncation was used. Model selection and fit were as- sessed using the Akaike Information Criteria (AIC) minimization criterion and goodness- of-fit tests (Buckland et al. 2001). For both species, the pattern of detection best fit the uniform model with cosine adjustment. Den- sity estimates were used in conjunction with the area of the reserve to produce estimates of total within-reserve population size. To evaluate habitat use in the extra-reserve landscape, we analyzed records of birds in flight and records of birds that were perched. The flight direction of each bird in flight was classified as toward, away from, or parallel to the Caetetus Reserve. Chi-square tests were Evans et al. • ECOLOGY OF BRAZILIAN PARROTS 159 TABLE 2. Positive (species present) and negative (species absent) habitat associations (mean ± SE) of perched parrots in Caetetus Reserve, Sao Paulo state, Brazil (2002). Boldfaced values are significantly different after sequential Bonferroni adjustment (r-tests were used for normally distributed variables; otherwise Mann- Whitney f/-tests were used). Primolius maracana Piotms maximiliani Habitat parameter Present Absent Present Absent = 8 tv' = 82 = 26 = 64 Distance from edge (m) Distance from water (m) ! No. dead standing trees i No. primary forest trees Tree circumference (cm) I Circumference of largest tree (cm) I ^ Number of point count stations. ^ P = 0.039, Mann- Whitney (7-test = 185. P = 0.016, Mann-Whitney (/-test = 163.5. 769 ± 470 306 ± 186 1.6 ± 2.2 4.6 ± 0.7 116 ± 17 174 ± 42 909 ± 484 293 ± 209 3.1 ± 3.5 ± 1.4^^ 135 ± 46 214 ± 95 760 ± 398 252 ± 175 2.9 ± 2.2 3.7 ± 1.4 130 ± 43 194 ± 90 952 ± 504 311 ± 217 2.9 ± 1.9 3.6 ± 1.4 135 ± 45 217 ± 92 used to examine differences in flight direc- tions of each species during the mornings and afternoons. Diurnal patterns of flight activity and habitat use were assessed by plotting the mean numbers of each species flying or I perched per hr per km^ during each hour of ! the morning (07:00-10:00) and afternoon sur- I vey periods (15:30-17:30). j Spearman’s rank analyses were used to I identify correlations between pairs of species in terms of how they used the 70 plots. In all multiple comparisons, we used a sequential Bonferroni adjustment (Rice 1989) to deter- mine significance of individual correlations. Spearman’s rank analyses also were used to identify correlations between the amount of flight activity and extra-reserve habitat type, richness, and connectivity measures. In effect, we looked for correlations between the num- ber of flights made by parrot groups per hour I across plots and the habitat or connectivity characteristics of those plots (e.g., percentage cover of each habitat type, distance to re- serve). To calculate a habitat preference index for each parrot species, we compared the propor- tion of perched parrot records (whether singly I or in groups) in a given habitat type to the I total percentage of that habitat type. For ex- ! ample, if 10% of perched records of a species ! were recorded in a habitat that composed 10% ' of the total vegetatioti across all plots, then ' the index of usage would equal 1. Values >1 j indicated habitat selection, and < 1 indicated 1 habitat avoidance. Zero indicated habitats never u.sed. RESULTS Habitat use and abundance within the re- serve.— Although four parrot species were re- corded in or flying over the reserve, B. ver- sicolurus and F. xanthopterygius were only occasionally recorded. The two regularly re- corded species, P. maracana and P. maximi- liani, were neither positively nor negatively associated (x^ — 0.02, df = 1, P = 0.88) with one another. The presence of perched P. maracana at census points was negatively associated with the number of dead standing trees, and posi- tively associated with the number of primary forest trees (Table 2). P. maximiliani showed no significant relationships with any of the habitat variables. We recorded only 35 perched parrots during 540 point counts {n = 11 for P. maracana, and n = 24 for P. maximiliani). However, be- cause these data represent only those parrots detected within 50 m of census points, density estimates were still reasonably high. The den- sity estimate for P. maximiliani (8.8 + 2.0 per kiiE) was approximately twice that of P. mar- acana (4.1 + 1.6 per km’)- The population estimate for maracana was 88 + 34 indi- viduals (Table 3). The extra-reserve habitat and its use by parrots.— Pasturelands and coffee plantations were the predominant habitat types, compos- ing 75% of the extra-reserve landscape. Riv- erine and primary forests were the dcmi inant natural habitats, but represented only 14% of the area. Natural habitats made up 21.4% of the extra-reserve landscape ( fable 1 ). 160 THE WILSON BULLETIN • VoL 117, No. 2, June 2005 TABLE 3. Encounter rates (groups encountered/ 10 point counts), density estimates (individuals/km^), and population estimates for parrots in Caetetus Reserve, Sao Paulo state, Brazil (2002). Values are means ± SE (upper and lower 95% Cl). Primolius maracana Pionus maximiliani Number of groups (n) Number of point counts (K) Encounter rate Density estimate Population estimate 11 540 0.20 ± 0.08 4.1 ± 1.6 (1. 9-8.5) 88 ± 34 (42-185) 24 540 0.44 ±0.10 8.8 ± 2.0 (5.7-14) 193 ± 44 (123-301) P. maracana and B. versicolurus were the two most frequently recorded species (Table 4). Use of extra-reserve habitats by P. mara- cana was positively correlated with that of both P. maximiliani and B. versicolurus. Use of extra-reserve habitats by B. versicolurus was positively correlated with that of all other species. Of the eight habitat/landscape variables tested, only DIST showed significant autocor- relation between plots (Z = 5.02, P < 0.001); this is not surprising, as adjacent plots were nearly equidistant from the reserve. Neither FOREST (Z = 0.60, P = 0.55) nor any of the habitat variables were autocorrelated: primary forest (Z = 1.50, P = 0.13), secondary forest (Z = 0.72, P = 0.47), scrub (Z = 0.36, P = 0.72), Eucalyptus (Z = 0.75, P - 0.46), coffee (Z = 1.41, F = 0.16), or pasture (Z = 1.8, P = 0.072). Extra-reserve activity and movements. — Extra-reserve flight activity of P. maracana and P. maximiliani was greater in the morn- ings and evenings than during the middle of the day (Eig. 3A, B), whereas B. versicolurus exhibited greater flight activity in the early mornings (Fig. 3C). There were more records of perched P. maracana early in the mornings (Fig. 3D), whereas perched B. versicolurus were recorded more often in the afternoons (Eig. 3E). Direction of P. maracana flight (the num- ber of groups flying toward, away from, or parallel to the reserve) differed between the morning and afternoon (x^ = 29.2, df = 2, F < 0.001). More birds flew away from the re- serve in the morning, and more flew toward the reserve in the evenings than expected (numbers of parrots flying in other directions were similar in the mornings and evenings). There was no difference in the direction of morning and evening flights for P. maximili- ani (x" = 0.77, df = 2, P = 0.68) or for B. versicolurus (x^ = 3.76, df = 2, P = 0.15). Eactors influencing parrot movements. — Plight activity of P. maracana and P. maxi- miliani outside the reserve decreased with in- creasing DIST; however, none of the other connectivity variables were correlated with parrot movements (Table 5). Parrot groups of three species were recorded flying more fre- quently over plots containing relatively large percentages of natural habitats (primary, sec- ondary and riverine forest, and scrub). Plight TABLE 4. Parrot use of I- X 1-km plots outside the Caetetus Reserve {n = 70 plots in all cases), Sao Paulo state, Brazil (2002). Associations between species are based on Spearman’s rank correlation analyses of abun- dance of perched groups within plots. Spearman’s coefficients are given for significant (P < 0.05) correlations after a sequential Bonferroni adjustment. No. groups % 1- X 1-km plots pa pa F Primolius maracana 249 41 86 27 Pionus maximiliani 142 25 44 16 Aratinga leucophthalmus 9 15 7 4 Brotogeris versicolurus 234 60 67 21 Correlations Pionus Aratinga Brotogeris maximiliani leucophthalmus versicolurus + 0.40 NS^’ +0.50 NSt’ +0.35 + 0.45 3 F = flying record, P = perched record. NS = not significant. Evans et al. • ECOLOGY OF BRAZILIAN PARROTS 161 2.0 1.5 1.0 0.5 0.0 7.00 8.00 9.00 16.00 17.00 Flying A Primolius maracana 1.0 0.8 0.6 0.4 0.2 7.00 8.00 9.00 16.00 17.00 Perched D Primolius maracana B Pionus maximiliani 2.0. 1.5. 7.00 8.00 9.00 16.00 17.00 E Pionus maximiliani 1.0- 0.8- 0.6. 0.4. T 7.00 8.00 9.00 16.00 17.00 C Brotogeris versicolurus 7.00 8.00 9.00 16.00 17.00 F Brotogeris versicolurus 7.00 8.00 9.00 16.00 17.00 Time FIG. 3. Diurnal cxtra-re.scrvc (light activity and habitat use (perched) for three commonly recorded parrot species at Caetetus Reserve. Sao I’aulo state, Bra/il. Bars repre.sent the mean number of groups recorded pet- hour (mean ± SL) within hour-long time periods. frequency of A. leucophthahnus was positive- ly correlated with habitat richtiess within plots. Extra-reserve habitat use. Only four of the extra-reserve habitats were used by par- rots, and the two dominant habitats — pasture- lands and coffee plantation.s — were ne\ er used by any species ('Table b). The otily artificial habitat used was Euealyptus plantation (by two species). Primary forest was the habitat most preferred for E. maraeana and E. niax- imiliani. whereas secondary forest was pre- 162 THE WILSON BULLETIN • Vol. 1J7, No. 2, June 2005 TABLE 5. Spearman’s correlations {P < 0.05 after sequential Bonferroni adjustment; n = 70 plots in all cases) between frequency of flights by parrot groups over 1- X 1-km plots and characteristics of 1- X 1-km plots at Caetetus Reserve, Sao Paulo state, Brazil (2002). Habitat/landscape variable Primolius Pionus Aralingu Brotogeris maracuna ma.ximiliani leucophthulmus versicolurus Pasture Secondary forest Coffee Natural habitats Primary forest Riverine forest Scrub Habitat richness Connectivity variables Distance to reserve (DIST) Percentage forest between plot and reserve (FOREST) Largest gap in forest between plot and reserve (GAP) + 0.36 -0.31 +0.35 +0.27 + 0.27 + 0.38 -0.35 -0.58 ferred by A. leucophthalmus and B. versicol- urus. Riverine habitats were used by all spe- cies, but were not used disproportionately to their availability by any species. DISCUSSION Of seven parrot species recorded during our study, only two were regularly encountered in the reserve itself. B. versicolurus was record- ed flying over and using a variety of habitats in the extra-reserve landscape (particularly those around farms), reflecting its generalist lifestyle (Juniper and Parr 1998). Movements of A. leucophthalmus were actually more common well away from the reserve, indicat- ing some avoidance of habitats around the main forest block. Both of these species are thriving in Brazil’s anthropogenic habitats (Ju- niper and Parr 1998). The species we were most interested in, P. maracana, was frequently recorded both in- side and outside the reserve. We could find few specific habitat associations for the spe- cies within the reserve, although it did tend to occur in areas of primary forest with few dead trees. Our population estimate for the reserve was 88 birds; however, for two reasons we believe that there are additional populations that spend much or all of their time outside the reserve. First, the within-reserve density estimate was based on data collected during the day at times when some individuals had left the reserve to feed in the surrounding ag- ricultural landscape. Second, we believe that TABLE 6. Preference index for parrot use of extra-reserve habitats outside Caetetus Reserve, Sao Paulo state, Brazil (2002). Habitats are ranked according to their use by Primolius maracana. Indices are based on the number of birds recorded as perched in the different habitats. Habitat preference index Habitat Primolius maracana Pionus ma.ximiliani Aratinga leucophthalmus Brotogeris versicolurus Primary forest (6.0) 3.8 2.7 0.3 2.3 Eucalyptus (2.1) 2.9 1.0 0 0 Secondary forest (4.5) 2.0 0.7 2.2 12 Riverine (8.0) 0.6 0.3 0.6 0.1 Pasture (42.0) 0 0 0 0 Coffee (33.0) 0 0 0 0 Scrub (2.9) 0 0 0 0 Rubber/orange (1.1) 0 0 0 0 “ Percent of total extra-reserve habitat. Evans et al. • ECOLOGY OF BRAZILIAN PARROTS 163 I there is a population of P. maracana based ! well outside the reserve, as a flock of 56 in- I dividuals was recorded 9 km south of the re- i serve. These populations may be large enough I for the species to persist in the area, at least I in the short term. Despite being recorded commonly outside ; the reserve, all four common parrot species , were selective as to the extra-reserve habitats they used. The dominant habitats — pasture and coffee plantations — were never used by any species. This is not surprising, as the pas- j ture and coffee crops around Caetetus con- ! tained very few remnant or planted trees. Cof- fee fruits may be used by P. maracana at some times of year (e.g., Marsden et al. 2000), but certainly coffee plantations are not attrac- tive or a keystone habitat for any of the par- rots. All records of parrot habitat use were in just four habitats, with Eucalyptus plantations being the only artificial habitat used. In fact, parrots only selected three habitats more than expected on the basis of their availability in the landscape: secondary forest was selected by three species, primary forest remnants by : two species, and Eucalyptus plantations by I one species. Studies elsewhere have stressed the impor- I tance of dispersal ability and corridors for the i use of extra-reserve habitats by animals (e.g.. Fires et al. 2002). We calculated three habitat connectivity indices, but only one (DIST) was important in explaining patterns of parrot movements. It may be that the other measures did not reflect barriers to parrot movement, or at least did not add to the explanatory power of using simple distance from the reserve. P. I maracana — like most, but not all parrots (e.g., I Rowley 1983, Marsden et al. 2000) — are re- garded as good dispersers, and we suggest that availability of natural forest, rather than mo- i bility, constrains parrot distribution around Caetetus. Blue- winged Macaws were once tound in many states in Brazil, eastern Paraguay, and northeastern Argentina (Juniper and Parr 1998), but the species has become extirpated I over much of its range, and lurther extirpa- ' tions are predicted in forest tragmenls (Snyder et al. 2()()0). Although we do not know what limits the area's populations ol parrots, there is general concern about recruitment rates among cavity-nesting parrots (e.g., Mawson and Long 1994, Snyder et al. 2000), and nest- site availability within the reserve needs to be examined. At a landscape scale, the mainte- nance of forest remnants around the reserve is most important to the populations of P. mar- acana and other parrots. We suggest that while primary forest may be most preferred by P. maracana, other forest types, and even Eucalyptus, has some benefit to the parrot as- semblage. Legislation in Sao Paulo state dictates that 10% of land on private farms be maintained as forest. Our data indicate that for Caetetus, as suggested for other reserves in the Atlantic Forest (Marsden et al. 2000), reforestation in areas adjacent to nature reserves may be dis- proportionately valuable for enhancing parrot populations, and, presumably, other wildlife that inhabit reserves. The degree of defores- tation in the interior of Sao Paulo is so acute that there is a strong argument for focusing forest-restoration programs almost entirely on landscapes surrounding the region’s few re- serves. ACKNOWLEDGMENTS We thank M. Galetti and M. Flavia Nunes for help setting up the project and for advice in the field. We are grateful for the warm hospitality and logistical sup- port of the staff at Caetetus Ecological Station. S. Mor- gan and A. Spencer helped with data collection. SJM was funded with a grant from the North of England Zoological Society at Chester Zoo, and he thanks R. Wilkinson for help along the way. LITERATURE CITED Alzen, M. a. and R Feinsinger. 1994. Forest frag- mentation, pollination, and plant reproduction in a Chaco dry forest, Argentina. Ecology 75:330- 35 1 . Bentei:y, J. M., C. P. CArn:KAEE, and G. C. Smith. 2()()(). Effects of fragmentation of Araucarian vine forest on small mammal communities. Conserva- tion Biology 14; 1057-1087. BirdLiii- iNiiiKNArioNAi.. 2000. Threatened birds of the world. Birdlife International. Cambridge. United Kingdom and Lynx Fyiicions. Barcelona, Spain. Bi'cki.and. S. T.. I). R. Andi kson. K. P. Bi rnham. .1. L. Laaki:. I). L. BoRcm Rs. and L. Thomas. 2001. Introduction to distance sampling: estimating abundance of biological populatituis. Oxford Uni- versity Press. Oxforil. United Kingdom. ('t iii.N, I... Jr., f-7 R. Bodmi r. ANt) C'. Vai i adari.s- Padi . 2001. Ixological consequences of hunting in Atlantie Torest patches. Sao Paulo. Brazil. Oryx 35:137 144. 164 THE WILSON BULLETIN Vol. I / 7, No. 2, June 2005 Dale, V. H„ S. M. Pearson, H. L. Offerman, and R. V. O’Neil. 1994. Relating patterns of land use change to faunal biodiversity in the central Am- azon. Conservation Biology 8:1027-1036. Gascon, C., T. E. Lovejoy, R. O. Bierregaard, J. R. Malcom, P. C. Stouffer, H. L. Vasconcelos, W. E Laurance, B. Zimmerman, M. Tocher, and S. Borges. 1999. Matrix habitat and species richness in tropical forest remnants. Biological Conserva- tion 91:223-229. Gotmark, E, H. Soderlundh, and M. Thorell. 2000. Buffer zones for forest reserves: opinions of land owners and conservation value of their forest around nature reserves in southern Sweden. Bio- diversity and Conservation 9:1377-1390. Gurd, D. B., T. D. Nudds, and D. H. Rivard. 2001. Conservation of mammals in eastern North Amer- ican wildlife reserves: how small is too small? Conservation Biology 15:1355-1363. Juniper, T. and M. Parr. 1998. Parrots: a guide to parrots of the world. Pica Press, East Sussex, Unit- ed Kingdom. Laurance, W. E 1991. Ecological correlates of extinc- tion proneness in Australian tropical rainforest mammals. Conservation Biology 5:79-89. Laurance, W. E, L. V. Eerreira, J. M. Rankin-De Merona, and S. G. Laurance. 1998. Rain forest fragmentation and the dynamics of Amazonian tree communities. Ecology 79:2032-2040. Marsden, S. j. 1999. Estimation of parrot and hornbill densities using a point count distance sampling method. Ibis 141:377-390. Marsden, S. J., M. Whiffin, L. Sadgrove, and P. Gui- MARAES, Jr. 2000. Parrot populations and habitat use in and around two Brazilian Atlantic Eorest reserves. Biological Conservation 96:209-217. Mawson, P. R. and j. L. Long. 1994. Size and age parameters of nest trees used by four species of parrot and one species of cockatoo in south-west Australia. Emu 94:149-155. McNally, R. and G. Horrocks. 2000. Landscape- scale conservation of an endangered migrant: the Swift Parrot {Lathamus discolor) in its winter range. Biological Conservation 92:335-343. Mesquita, R. C. G., P. Delamonica, and W. E Laur- ance. 1999. Effect of surrounding vegetation on edge-related tree mortality in Amazonian forest fragments. Biological Conservation 91:129-134. Morellato, L. P. C. and C. E B. Haddad. 2000. In- troduction: the Brazilian Atlantic Eorest. Biotro- pica 32:786-792. Myers, N., R. A. Mittermeier, C. G. Mittermeier, G. A. B. DA Eonseca, and J. Kent. 2000. Biodi- versity hotspots for conservation priorities. Nature 403:853-858. PiRES, A. S., P. K. Lira, E A. S. Eernandez, G. M. ScHiTTiNi, AND L. C. Oliveira. 2002. Erequency of movements of small mammals among Atlantic Coastal Eorest fragments in Brazil. Biological Conservation 108:229-237. Rice, W. R. 1989. Analyzing tables of statistical tests. Evolution 43:223—225. Ricketts, T. H., G. C. Daily, P. R. Ehrlich, and J. P. Pay. 2000. Countryside biogeography of moths in a fragmented landscape: biodiversity in native and agricultural habitats. Conservation Biology 15: 378-388. Rowley, I. 1983. Mortality and dispersal of juvenile Galahs, Cacatua roseicapilla, in the western Aus- tralian wheatbelt. Australian Wildlife Research 10:329-342. Saunders, D. A., R. J. Hobbs, and C. R. Margules. 1991. Biological consequences of ecosystem frag- mentation: a review. Conservation Biology 5:18- 32. Snyder, N., P. McGowan, J. Gilardi, and A. Grajal (Eds.). 2000. Parrots: status and conservation ac- tion plan 2000-2004. lUCN, Gland, Switzerland and Cambridge, United Kingdom. Tavares, E. S., C. Yamashita, and C. Y. Miyake 2004. Phylogenetic relationships among some Neotropical parrot genera (Psittacidae) based on mitochondrial sequences. Auk 121:230-242. Turner, I. M. 1996. Species loss in fragments of trop- ical rain forest: a review of the evidence. Journal of Applied Ecology 33:200-209. Verboom, j., R. Poppen, P. Chardon, P. Opdam, and P. Luttikhuizen. 2001. Introducing the key patch approach for habitat networks with persistent pop- ulations: an example for marshland birds. Biolog- ical Conservation 100:89-101. Western, D. and I. M. C. Pearl. 1989. Conservation for the 21st century. University Press, New York and Oxford, United Kingdom. Willis, E. O. 1979. The composition of avian com- munities in remanescent woodlots in southern Brazil. Papeis Avulsos de Zoologia 33:1-25. Wilson Bulletin 1 17(2):165-171, 2005 REPRODUCTIVE SUCCESS OF PIPING PLOVERS AT BIG QUILL LAKE, SASKATCHEWAN WAYNE C. HARRIS, DAVID C. DUNCAN,^^.’ RENEE J. FRANKEN,^ DONALD T. McKINNON,2 5 AND HEATHER A. DUNDAS" ABSTRACT. — Big Quill Lake, Saskatchewan, is an important breeding area for Piping Plovers {Charadrius i melodus)-, the area hosts up to 8% of the continental breeding population, yet little is known about how the site i contributes to the overall survival of this species. We studied the reproductive success of Piping Plovers at Big ! Quill Lake from 1993 to 1995. We located 208 nests and captured and banded 456 young. Nest initiation occurred from mid-May to mid-July, and median nest-initiation dates were 14, 13, and 13 May in 1993, 1994, and 1995, respectively. Mean clutch size for presumed first nests was 3.92 eggs. Nesting success was consistently high ( from 1993 to 1995, with Mayfield estimates of nest success ranging from 75 to 88%; nests initiated later in the I season were less successful than earlier nests. The wide beach (200-1,000 m) at Big Quill Lake may have contributed to high nesting success by reducing efficiency of predators. Use of Big Quill Lake beaches by I humans and cattle was also minimal. Fledging success varied dramatically, with 0.02, 1.35, and 1.78 young ' fledged per breeding pair in 1993, 1994, and 1995, respectively. Low productivity of Piping Plovers in 1993 I was a result of low chick survival during a week of rain, cold temperatures, and high winds, rather than low j nesting success. Fledging success in 1994 and 1995 was higher than the 1.24 chicks per pair required for i population stability on alkaline lakes in the Northern Great Plains. This high productivity suggests that Big Quill I Lake is an important Piping Plover breeding site and measures should be taken to ensure its continued protection, i Received 21 April 2004, accepted 3 March 2005. ! Piping Plover {Charadrius melodus) num- j bers have deelined continentally in the last 50 I years, due in part to permanent destruction of breeding and wintering habitats, and reduced reproductive success (Sidle 1984, Haig 1992). This decline has resulted in the Piping Plover j being listed as an endangered species in Can- I ada (Haig 1985), endangered in the Great I Lakes region of the United States, and threat- j ened elsewhere in the United States (Sidle I 1984). Low reproductive success is consid- I ered a limiting factor to the recovery of Piping I Plovers in the Northern Great Plains (Haig j 1992, Ryan et al. 1993, Murphy et al. 1999); however, this aspect of demography has been documented at relatively few alkali lakes (Haig and Plissner 1992, Plissner and Haig ‘ Prairie Environmental Services, Box 414, Ray- more, SK SO A 3 JO, Canada. ^Saskatchewan Wetland Conservation Corp., 110- I 2151 Scarth St., Regina, SK S4P 3Z3, Canada. ’Current address: C'anadian Wildlife Service, Room I 200, 4999-98 Ave., Edmonton, AB fOB 2X3, C’anada. 14 Arnheim Rd., Whitehorse, Y'f YIA 3B4, C’an- , ada. ’Current address: Saskatchewan Pdivironment, 321 1 i Albert St., Regina, SK S4S 5W0, C'anada. ^ Deceased. I ’Corresponding author; e-mail: Dave. Duncan ^^ec.gc.ca 1997, Murphy et al. 1999). Monitoring repro- ductive success is considered a priority for the recovery of this species (U.S. Fish and Wild- life Service 1994). Factors thought to affect reproductive suc- cess of Piping Plovers include weather (e.g., Grover and Knopf 1982, Haig and Oring 1988, Sidle et al. 1992), fluctuating water lev- els (e.g., Mayer 1990, Sidle et al. 1992, Espie et al. 1998, Skeel and Duncan 1998), and egg and chick predation (e.g., Rimmer and De- blinger 1990, Mayer and Ryan 1991, Melvin et al. 1992, Mabee and Estelle 2000). The im- portance of these factors can vary annually and with the type of breeding site (Larson et al. 2002). Big Quill Lake, Saskatchewan, is a large alkaline wetland and is an important breeding site for Piping Plovers in North America. In 1996, the site had the largest breeding popu- lation (435 birds) of any site in North Amer- ica— 8% of the continental population and 26% of the Canadian prairie population (.Skeel et al. 1997). However, numbers lluctuate widely from year-to-year: the last three Inter- national CTmsuses at Big Quill Lake reported 151 adults in 1991 (llaig and Plissner 1992). 435 adults in 1996 (Plissner and Haig 1997). and 105 atlults in 2001 (l erland and Haig 2002); Harris and Lamont (1991) reported 43 165 166 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 birds in 1989, and Harris estimated over 440 birds in 1995 (W. C. Harris pers. comm, in Skeel et al. 1997). Even though Big Quill Lake can support a large breeding population of Piping Plovers, there is very little information on Piping Plo- ver reproductive success at this lake and the role it plays in the overall conservation of this species. The purpose of this paper is to ex- amine the reproductive success of Piping Plo- vers at Big Quill Lake by documenting nest- ing chronology, nesting success, and fledging success. Knowledge of Piping Plover repro- ductive success at such an important breeding area will increase our ability to conserve and manage this endangered species. METHODS Study area. — Big Quill Lake (51°53'N, 104° 15' W) is a large (30,700 ha), shallow, saline basin on the Central Saskatchewan Plains about 200 km east of Saskatoon. The shoreline is primarily alkaline mudflats, and is approximately 200 km long when the basin is full. The upper beaches are partially to fully vegetated with alkali grass (Distichlis stricta), western sea-blite (Siiaeda depressa), Nuttall’s salt-meadow grass (Puccinellia nuttalliana), northern reed grass {Calamagrostis inexpan - sa), and wild barley (Hordeum jubatum). In 1993 and 1994, the basin was approximately 60% flooded, and beach width was approxi- mately 1,000 m (Harris 1993, 1994). In 1995, the water level in Big Quill increased due to heavy snowfall the previous winter, resulting in a beach width of <200 m (Harris 1995). Nest surx’eys. — Our study area was located on the east side of Big Quill Lake and com- posed approximately one-third of the shore- line. During 1993-1995, we surveyed the study area at least twice weekly from 7 May to 30 August. We searched for territorial pairs of Piping Plovers (birds calling, exhibiting ag- gressive or defensive behavior, or performing courtship displays) by systematically walking or slowly traversing the shoreline with an all- terrain vehicle (ATV). We watched territorial birds from a distance of 50-100 m, which al- lowed birds to return to their nest. We plotted the location of all birds on a map of the study area. We marked nests with pin-flags placed at least 30 m away in the adjacent vegetation, and plotted nest locations on an aerial photo- graph of the shore. We determined nest oc- cupancy using a 15-60X telescope from a dis- tance of 50-100 m during repeat visits. We visited nests every 3 days during initiation and early incubation. Most nests were located dur- ing egg-laying; when full clutches were found, a single egg was floated to estimate incubation stage (Schwalbach 1988). We estimated hatch dates assuming a 6-day egg-laying period and a 28-day incubation period (Whyte 1985). We used this information to return to nests near hatching and band chicks before they moved away from their nest. Although young plovers generally left the nest scrape shortly after the last egg hatched, they were rarely far from the scrape during the first few days, and the broods remained close to their nest site until they were capable of flight. Chicks were banded with a standard federal aluminum leg band, and either one or two col- ored celluloid bands to allow for further rec- ognition without recapture. Color-banded broods were checked every 2 to 3 days to monitor survival and movements, and all nests and broods were followed until fledging or nest failure. Young that disappeared after they reached 21 days of age were considered to have fledged (Haig 1992). We defined fledg- ing rate as the number of young fledged per breeding pair. Murphy et al. (1999) suggest that fledging rate is the most important mea- sure of reproductive success for the Piping Plover, because it represents “a direct link to recruitment.” We defined the number of breeding pairs as the number of first nests. We distinguished first nests from late nests based on break points in nest-initiation dates, and assumed that late nests were renests. Between mid-July and mid-August, we made weekly visits to six staging areas located outside the study area to check for marked young that may have been alive but missed during sur- veys of the study area. Statistical analysis. — We used the Mayfield method to estimate nesting success (Mayfield 1961, 1975). Nests were considered successful if at least one chick hatched. Mayfield nest success was defined as (1 — daily mortality rate)'^, where daily mortality rate = number of nest losses/total exposure days, and N = nest- ing period. The average nesting period from nest initiation (first egg) to hatching (first hatch) was 33 days. We also estimated egg Harris et al. • PIPING PLOVER REPRODUCTIVE SUCCESS 167 TABLE 1. Nesting chronology, clutch size, and reproductive success of Piping Plovers at Big Quill Lake, Saskatchewan, 1993-1995. Productivity variable 1993 1994 Median nest-initiation date (range) Number of nests Number of first nests'* (and presumed renests) Number of eggs laid (mean ± SE) Number of chicks hatched (mean ± SE) Number of chicks fledged (mean ± SE) Daily survival rate of nests (DSR)** Mayfield nest success (95% Cl)** 14 May (10 May-1 1 July) 51 42 (9) 183 (3.59 ± 0.12) 144 (2.82 ± 0.24) 1 (0.02 ± 0.02) 0.991 0.752 (0.63-0.89) 13 May (10 May-21 June) 73 71 (2) 280 (3.84 ± 0.06) 231 (3.16 ± 0.18) 96 (1.32 ± 0.17) 0.994 0.822 (0.73-0.92) 1995 13 May (10 May-21 June) 84 83 (1) 333 (3.96 ± 0.00) 287 (3.42 ± 0.15) 148 (1.76 ± 0.16) 0.996 0.875 (0.80-0.95) ® First nests were distinguished from renests based on a break point in nest-initiation dates. Nests initiated after 27 June, 20 June, and 20 June for 1993, 1994, and 1995, respectively, were considered renests. ^ Daily Survival Rate (DSR) = (1 - number of losses/total exposure days). Mayfield nest success = DSR^^ (33 is the calculated average nesting period from nest initiation [first egg] to hatching); SE = {[DSR(1 - DSR)]/total exposure days)^; 95% Confidence Limits = [DSR ± 2(SE)]^^. ; success (proportion of eggs that hatched) and fledging success (mean number of fledglings per breeding pair). We used Cox regression survival analysis to examine the effect of year on survival of broods. The Cox proportional hazards model (Cox 1972) models the hazard rate or the rate of failure. The hazard rate is assumed to be a function of time, but this method does not at- tempt to characterize the function (Nur et al. 2004). The null hypothesis is that the ratio of hazard rates = 1 (i.e., no difference between groups). Survival analysis includes time-to- ! death and time-to-end-of-moniloring data for I broods that were still alive when monitoring i ceased. Survival analysis is useful when the I ultimate outcome may be uncertain (i.e., when I it is not possible to continue monitoring nests \ due either to weather or the culmination of the j nesting cycle). For our study, we were certain I how long broods survived, but only until I monitoring ceased. Data are considered to be I right-censored when the start time is known, ! but (brood) failure time is unknown. Our data were right-censored because there was incom- plete information on the outcome (i.e., we do not know when all individuals died). We de- fined survival time as time from hatch to the last day chicks were observed. Chicks were assumed to have died if they disappeared be- fore 21 days of age. As long as one chick in each brood survived to the end of monitoring, the brood was still considered to be alive. We compared brood survival for 1993 to 1995 and 1994 to 1995. We used the Kruskal-Wallis rank sum test to determine whether nest-initiation data var- ied among years, and we used linear regres- sion to determine whether clutch size de- creased with nest initiation. We used logistic regression to determine whether nest and fledging success — both measured as binary re- sponse variables (1 = success, 0 = failure) — were dependent on nest-initiation date (all nests combined). We used S-PLUS (Mathsolt, Inc. 1997) to conduct statistical analyses. Means are presented ± SE. RESULTS Nest chronolo^w — We found 208 nests and captured and banded 456 young on the east side of the lake (Table 1 ). We banded 140 of 148 hatched young in 1993, 129 of 232 in 1994, and 187 of 288 in 1995. ligg-laying commenced by the 2nd week in May and continued until the 2nd week in July. Over half of all nests were initiated in a 4-day period from 11 to 14 May. fhe median date of nest initiation was 14, 13, and 13 May in 1993, 1994, aiul 1995, respectively, and did 168 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 EIG. 1. Proportion of Piping Plover broods surviving (presumed) from hatching to fledging at Big Quill Lake, Saskatchewan, 1993—1995. Chicks that disappeared after 21 days were assumed to have fledged. not differ among years (Kruskal-Wallis = 0.52, df = 2, P = 0.77, n = 208). However, in 1993, 18% (n = 9) of nests were initiated after 26 June, whereas in 1994 and 1995, no nests were initiated after this date. We estimated 42, 71, and 83 breeding pairs in 1993, 1994, and 1995, respectively, based on the estimated number of first nests. In 1993, no nests were initiated between 2 and 26 June; thus, we assumed that the nine nests initiated after 26 June were renests. In 1994, no nests were initiated between 14 and 20 June and the two nests initiated after 20 June were considered renests. In 1995, no nests were initiated between 14 and 20 June and we assumed that the single nest initiated on 21 June was a renest. Clutch size. — Mean clutch size was 3.92 ± 0.02 eggs/clutch for presumed first nests and 2.25 ± 0.28 eggs/clutch for late nests (all years combined). Clutch size decreased with nest-initiation date (linear regression: (3 = -0.035, SE = 0.002, P, 207 = 461.27, P < 0.001). Late nests had a mean of 1.89 ± 0.2 (a7 = 9), 3 ± \ {n — 2), and 4 (;? = 1) eggs per nest in 1993, 1994, and 1995, respectively. Of 51 nests initiated in 1993, 2% {n = \) had five eggs, 75% {n = 38) had four eggs, 8% {n = 4) had three eggs, 12% (72 = 6) had two eggs, and 4% {n = 2) had one egg. In 1994, of 73 nests initiated, 88% {n = 64) had four eggs, 8% {n = 6) had three eggs, and 4% {n = 3) had two eggs. Of 84 nests initiated in 1995, 1% {n = 1) had five eggs, 94% {n = 79) had four eggs, and 5% (« = 4) had three eggs. Nesting success, fledging success, and brood survival. — Mayfield nest success was high in all years (75, 82, and 88% in 1993, 1994, and 1995, respectively). The probability of nesting success decreased with later nest- initiation dates (logistic regression: (3 = -0.040, SE = 0.012, t = -3.50, df = 1, P < 0.001). One percent {n = 1), 42% {n = 96), and 52% {n = 148) of chicks fledged in 1993, 1994, and 1995, respectively. In 1993, 0.02 young fledged per breeding pair, whereas in 1994 and 1995 fledgling success was 1.35 and 1.78 per pair. Nests with later hatch dates had lower fledging success (logistic regression: (3 = -0.047, SE = 0.017, t = -2.85, df = 1, P = 0.001). Brood survival was lower in 1993 than in 1995 (Z = 3.45, P < 0.001), but was not significantly different between 1994 and 1995 (Z = 1.73, P - 0.084; Fig. 1). DISCUSSION Median nest-initiation dates in this study were similar to those found at Big Quill Lake in 1980 and 1981 (13 May and 9 May; Whyte 1985), and at Lake Diefenbaker, Saskatche- wan (e.g., 12 May in 1992 and 9 May 1993; Espie et al. 1998). However, the 1993 nesting attempts at Big Quill Lake were the latest re- ported in over 10 years of monitoring, and no young fledged from those nests (Harris 1993). Harris et at. • PIPING PLOVER REPRODUCTIVE SUCCESS 169 Harris (1993) attributed the late nesting to large losses of nests and broods in early spring during a period of inclement weather. Piping Plovers can renest once or twice in a season if the eggs are destroyed, and there are records of them producing two broods in a year (Bot- titta et al. 1997); however, usually they raise only one brood per year (Haig 1992). A seasonal decline in clutch size and repro- ductive success has been well documented for birds in general (e.g.. Lack 1968, Klomp 1970, Perrins 1970, Daan et al. 1989), and Piping Plovers in particular (Knetter et al. 2002). We found a similar pattern of larger clutch sizes and greater hatching success in early nests. We also found that clutch sizes of Piping Plovers at Big Quill Lake were similar to those reported from other studies (Haig ' 1992). The smaller average clutch sizes in ; 1993 were likely the result of a large renesting ! effort. Declines in reproductive success over ; a season are thought to be related to physio- j logical or energy demands related to timing of •breeding (Lepage et al. 1999), or to lower i quality or fitness of later breeders (Verhulst et lal. 1995). i Mayheld nest success was consistently high from 1 993 to 1 995 and was greater than nest ( success estimates from other sites (e.g., Mayer land Ryan 1991, Patterson et al. 1991, Loe- 1 gering and Fraser 1995, Mabee and Estelle J 2000, Lauro and Tanacredi 2002). Several fac- tors may explain the high nest success at Big Quill Lake from 1993 to 1995. First, predation pressure at Big Quill Lake may be lower than ^ at other lakes in the region due to the rela- 1 tively wide shoreline, which lowers the prob- ability of predators detecting nests (Prindiville Gaines and Ryan 1988, Fspie et al. 1996). Even though we observed a dramatic change in the average distance from nesting sites to water from 1994 to 1995, productivity changed little between these years, suggesting that beach width in 1995 (200 m) was still above the minimum threshold required for good nesting success. In fact, productivity was slightly higher in 1995, when the beach was narrower, suggesting that even when water i levels are high al this lake, the distance from ij water to nesting sites, and/or from permanent I vegetation to nest sites, may still be sullicient j to allow for high nest and fledging success. In ! addition to the wide beach, there are few trees. shrubs, or other perch sites in proximity to the nesting areas around Big Quill Lake, which may have reduced perching opportunities for avian predators. Disturbance by humans and cattle was low at Big Quill Lake, but is known to reduce productivity in some areas (e.g.. Burger 1994). Mayfield nest success estimates from our study, and from more recent studies at Big Quill Lake (2002-2004; C. Gratto-Tre- vor unpubl. data), also were greater than those recorded at Big Quill Lake in the early 1980s (16% and 29%, Whyte 1985); the reason for this difference is unknown. Although Piping Plover nest success was high from 1993 to 1995, fledging success var- ied among years, which is typical of this spe- cies (Haig and Oring 1987, Maxson and Haws 2000, Knetter et al. 2002). At alkaline lakes in the Great Plains, Piping Plover reproductive success averages 0.89 fledglings per pair with- out predator exclusion, and 1.28-1.78 fledg- lings per pair with predator exclusion (Larson et al. 2002). Larson et al. (2002) determined that a mean reproductive success of 1.24 fledglings per pair would be required at al- kaline lakes to stabilize a declining population of Piping Plovers. This target was exceeded in 1994 and 1995 at Big Quill Lake, and it was greater than Whyte’s (1985) 0.76 fledg- lings per pair at Big Quill Lake a decade ear- lier (although the low reproductive success re- ported by Whyte [1985] was due, in large part, to a lower rate of nesting success as op- posed to fledging success). The high repro- ductive success at Big Quill Lake during 1994 and 1995 suggests that — at least in some years — this area may serve as a source for Piping Plovers in the Northern Great Plains. Low fledging success in 1993 may be due, in part, to a period of prolonged heavy rain- fall, combined with cold temperatures and high winds (Harris 1993). Prior to 27 .lime, 55% of young were still alive, after which there was a long period of inclement weather. Once conditions had impixwed sufficiently to allow monitoring to resume on 7 .Inly, all young and eggs had disappeared from the stuily area anil a renesting effort was uiuler way. fhe only chick that was known to have fledged in 1993 was later found at a staging area. It is lu-obable. however, that other young fledged during this period of no monitoring, and were not accounted for at staging areas 170 THE WILSON BULLETIN • Vol. 1/7, No. 2, June 2005 later in the season. Seventeen broods were 13-15 days old before monitoring temporarily ceased and some of these chicks may have fledged before monitoring resumed 9 days lat- er. We feel that the low number of birds fledg- ing in 1993 is likely an underestimate, al- though similarly low numbers of young Pip- ing Plovers observed at the Big Quill Lake staging areas corroborates low fledging suc- cess in 1993. Survival analysis also suggests that brood survival was lower in 1993 than 1995, but was not different between 1994 and 1995, corroborating the low fledging success in 1993. Our study suggests that Big Quill Lake may serve as a population source for Piping Plo- vers in the Great Plains. The low productivity of Piping Plovers at Big Quill Lake in some years may be a result of low chick survival rather than low nesting success. Because of the numbers of nesting pairs and recent high productivity, the importance of Big Quill Lake as a breeding area for Piping Plovers is evi- dent. Measures should continue to ensure its protection and integrity. ACKNOWLEDGMENTS We dedicate this paper to the memory of W. C. Har- ris, who was the primary investigator on this project along with help from field assistants A. Harris, V. Har- ris, S. Lamont, T Lazorko, and S. McAdam. This re- search was funded by the Prairie Shores Program of the North American Waterfowl Management Plan as part of a study to assess habitat enhancement for Pip- ing Plovers. The Canadian Wildlife Service funded the updated analyses presented here. Helpful comments were provided by S. Davis, J. P. Goossen, C. Gratto- Trevor, V. Harris, S. Lamont, S. J. Maxson, and two anonymous reviewers. LITERATURE CITED Bottitta, G. E., a. M. Cole, and B. Lapin. 1997. Piping Plovers produce two broods. Wilson Bul- letin 109:337-339. Burger, J. 1994. The effect of human disturbance on foraging behavior and habitat use in Piping Plover {Charadrius melodus). Estuaries 17:695-701. Cox, D. R. 1972. Regression models and life tables. Journal of the Royal Statistical Society, Series B 34:187-220. Da AN, S., C. Dijkstra, R. H. Drent, and T. Meijer. 1989. Food supply and the annual timing of avian reproduction. Pages 392-407 in Acta XIX Con- gressus Internationalis Ornithologici (H. Ouellet, Ed.). Ottawa, Ontario, 1986. National Museum of Natural Sciences, Ottawa, Canada. Espie, R. H. M., R. M. Brigham, and P. C. James. 1996. Habitat .selection and clutch fate of Piping Plovers {Charadrius melodus) breeding at Lake Diefenbaker, Saskatchewan. Canadian Journal of Zoology 74:1069-1075. Espie, R. H. M., P. C. James, and R. M. Brigham. 1998. The effects of flooding on Piping Plover Charadrius melodus reproductive success at Lake Diefenbaker, Saskatchewan, Canada. Biological Conservation 86:215-222. Ferland, C. L. and S. M. Haig. 2002. 2001 Interna- tional Piping Plover census. U.S. Geological Sur- vey, Forest and Rangeland Ecosystem Science Center, Corvallis, Oregon. Grover, P. B. and F. L. Knopf. 1982. Habitat require- ments and breeding success of Charadriiform birds nesting at Salt Plains National Wildlife Ref- uge, Oklahoma. Journal of Field Ornithology 53: 139-148. Haig, S. M. 1985. The status of the Piping Plover in Canada. Report to the Committee on the Status of Endangered Wildlife in Canada. Ottawa, Ontario. Haig, S. M. 1992. Piping Plover {Charadrius melo- dus). The Birds of North America, no. 2. Haig, S. M. and L. W. Oring. 1987. Population studies of Piping Plovers at Lake of the Woods, Minne- sota, 1982-1987. Loon 59:113-117. Haig, S. M. and L. W. Oring. 1988. Mate, site, and territory fidelity in Piping Plovers. Auk 105:268- 277. Haig, S. M. and J. H. Plissner. 1992. 1991 Interna- tional Piping Plover census. Report to U.S. Fish and Wildlife Service Region 3, Division of En- dangered Species, Ft. Snelling, Minnesota. Harris, W. C. 1993. Piping Plover population evalu- ation at Big Quill Lake habitat enhancement study area — 1993. Saskatchewan Wetland Conservation Corporation, Regina, Saskatchewan, Canada. Harris, W. C. 1994. Piping Plover population evalu- ation at Big Quill Lake habitat enhancement study area — 1994. Saskatchewan Wetland Conservation Corporation, Regina, Saskatchewan, Canada. Harris, W. C. 1995. Piping Plover population evalu- ation at Big Quill Lake habitat enhancement study area — 1995. Saskatchewan Wetland Conservation Corporation, Regina, Saskatchewan, Canada. Harris, W. C. and S. M. Lamont. 1991. Saskatchewan Piping Plover population assessment — 1990: Big Quill Lake, Chaplin Lake, Lake Diefenbaker, Red- berry Lake and the South Saskatchewan River (Gardiner Dam to Saskatoon). Saskatchewan En- vironmental Society, Saskatoon, Canada. Klomp, H. 1970. The determination of clutch size in birds: a review. Ardea 58:1-124. Knetter, j. M., R. S. Lutz, J. R. Cary, and R. K. Murphy. 2002. A multi-scale investigation of Pip- ing Plover productivity on Great Plains alkali lakes, 1994-2000. Wildlife Society Bulletin 30: 683-694. Lack, D. L. 1968. Ecological adaptations for breeding Harris et al. • PIPING PLOVER REPRODUCTIVE SUCCESS 171 in birds. Methuen Publishing, London, United Kingdom. Larson, M. A., M. R. Ryan, and R. K. Murphy. 2002. Population viability of Piping Plovers: effects of predator exclusion. Journal of Wildlife Manage- ment 66:361-371. Lauro, B. and J. Tanacredi. 2002. An estimation of predatory pressures on Piping Plovers nesting at Breezy Point, New York. Waterbirds 25:401-409. Lepage, D., A. Desrochers, and G. Gauthier. 1999. Seasonal decline of growth and fledging success in Snow Geese Anser caerulescens: an effect of date or parental quality? Journal of Avian Biology 30:72-78. Loegering, j. P. and J. D. Eraser. 1995. Eactors af- fecting Piping Plover chick survival in different brood-rearing habitats. Journal of Wildlife Man- agement 59:646-655. Mabee, T. j. and V. B. Estelle. 2000. Assessing the effectiveness of predator exclosures for plovers. Wilson Bulletin 112:14-20. Mathsoft, Inc. 1997. S-PLUS 4 guide to statistics. Mathsoft, Inc. Seattle, Washington. Maxson, S. j. and K. V. Haws. 2000. Population stud- ies of Piping Plovers at Lake of the Woods, Min- nesota: 19 year history of a declining population. Waterbirds 23:475-481. Mayer, P. M. 1990. Conservation biology of Piping Plovers in the Northern Great Plains. M.Sc. thesis. University of Missouri, Columbia. Mayer, P. M. and M. R. Ryan. 1991. Survival rates of artificial Piping Plover nests in American Av- ocet colonies. Condor 93:753-755. Mayfield, H. E 1961. Nest success calculated from exposure. Wilson Bulletin 73:255—261. Mayfield, H. E 1975. Suggestions for calculating nest success. Wilson Bulletin 87:456-466. Melvin, S. M., L. H. MacIvor, and C. R. Griffin. 1992. Predator exclosures: a technique to reduce predation at Piping Plover nests. Wildlife Society Bulletin 20:143-148. Murphy, R. K., B. G. Root, P M. Mayer, J. P. Goo.s- SEN, and K. a. Smiih. 1999. A draft protocol for assessing Piping Plover reproductive success on Great Plains alkali lakes. Pages 90-107 in Pro- ceedings, Piping Plovers and Least Terns of the Great Plains and nearby (K. E Higgins, M. R. Brashier, and C. D. Kruse, Eds.). South Dakota State University, Brookings. Nur, N., a. L. 1Ioemi;s, and G. R. Geupf;e. 2004. Use of survival time analysis to analyze nesting suc- cess in birds: an example using Loggerhead Shrikes. Condor 106:457 — 171. Patterson, M. E., J. D. Eraser, and J. W. Roggen- BUCK. 1991. Eactors affecting Piping Plover pro- ductivity on Assateague Island. Journal of Wild- life Management 55:525-531. Perrins, C. M. 1970. Timing of birds’ breeding sea- sons. Ibis 112:242-255. Plissner, j. H. and S. M. Haig. 1997. 1996 Interna- tional Piping Plover census. U.S. Geological Sur- vey, Eorest and Rangeland Ecosystem Science Center, Corvallis, Oregon. Prindiville Gaines, E. and M. Ryan. 1988. Piping Plover habitat use and reproductive success in North Dakota. Journal of Wildlife Management 52:266-273. Rimmer, D. W. and R. D. Deblinger. 1990. Use of predator exclosures to protect Piping Plover nests. Journal of Eield Ornithology 61:217-223. Ryan, M. R., B. G. Root, and P. M. Mayer. 1993. Status of Piping Plovers in the Great Plains of North America: a demographic simulation model. Conservation Biology 7:581-585. SCHWALBACH, M. J. 1988. Conservation of Least Terns and Piping Plovers along the Missouri River and its major western tributaries in South Dakota. M.Sc. thesis. South Dakota State University, Brookings. Sidle, J. G. 1984. Piping Plover proposed as an en- dangered and threatened species. Federal Register 49:44712-44715. Sidle, J. G., D. E. Carlson, E. M. Kirsch, and J. J. Dinan. 1992. Flooding: mortality and habitat re- newal for Least Terns and Piping Plovers. Colo- nial Waterbirds 15:132-136. Skeel, M. a. and D. C. Duncan. 1998. Population size and productivity of Piping Plovers at Lake Diefenbaker in relation to water level. Blue Jay 56:137-146. Skeel, M. A., D. C. Duncan, and E. R. Wiltse. 1997. Saskatchewan results of the 1996 International Piping Plover census. Blue Jay 55:157-168. U.S. Fish and Wildlife Service. 1994. Draft revised recovery plan for Piping Plovers, Cliaracirins niel- oc/us, breeding on the Great Lakes and Northern Great Plains of the United States. Twin Cities, Minnesota. Vf:rhue.st, S. J., J. H. van Baeen. and .1. M. Tinbfir- gf:n. 1995. Seasonal decline in reproductive suc- cess of the Great fit: variation in time or quality? Ecology 76:2392-2403. Whyif;, a. .1. 1985. Breeding ecology of the Piping Plover (Cluirculrins nwlodns) in central Saskatch- ewan. M..Sc. thesis. University of Saskatchewan. .Saskatoon. C’anada. Wilson Bulletin 1 17(2):172— 176, 2005 BREEDING ECOLOGY OF WHITE-WINGED DOVES IN A RECENTLY COLONIZED URBAN ENVIRONMENT MICHAEL F. SMALL,” CYNTHIA L. SCHAEFER,' JOHN T. BACCUS,' AND JAY A. ROBERSON^ ABSTRACT. — Using field-implanted subcutaneous radio transmitters, we monitored the breeding biology of White- winged Doves {Zenaida asiatica) in a recently colonized urban area (Waco, Texas). We implanted trans- mitters in June 2002 {n = 39; 16 males, 23 females) and February and March 2003 {n = 40; 17 males, 17 females, 6 unknown sex), and tracked radio-tagged doves every 3rd day until transmitters no longer functioned (90-120 days). We tracked 26 doves to 36 nests in nine tree species. The maximum number of nesting attempts was four. Nest success of first and second nesting attempts was 62 and 24%, respectively, and overall nest success for both years combined was 52%. Mean nest height — as a proportion of tree height ranged from 0.31 to 0.75. Urban White-winged Doves had an extended breeding season; nesting attempts occurred both before and after the traditional dove breeding period in native brush habitats of the lower Rio Grande Valley of Texas. Field-implantation of subcutaneous radio transmitters was a viable technique tor monitoring nesting activities of White-winged Doves. Received 20 August 2004, accepted 13 March 2005. Over the last 40 years, the distribution of White-winged Doves {Zenaida asiatica) has undergone substantial change (Schwertner et al. 2002). Until the mid-1970s, the breeding range in Texas was limited mainly to four counties (Cameron, Starr, Hidalgo, and Wil- lacy) in the lower Rio Grande Valley (LRGV) at the extreme southern tip of the state (Cot- tam and Trefethen 1968, George et al. 1994). Since then. White-winged Doves have been expanding their range northward; the species has been recorded in Canada (Rogers 1998), with breeding documented as far north as Kansas (Moore 2001). The majority of breed- ing individuals in the United States, both cur- rently and historically, resides in Texas (George et al. 1994). White-winged Dove populations have in- creased substantially over the past 20 years, but only 16% of the Texas population now occurs in the LRGV (G. L. Waggerman pers. comm.). Large breeding populations of White- winged Doves have become established in central Texas, with numerous smaller, satellite populations occurring throughout the state. Concurrent with the northward range expan- sion, White-winged Dove populations are now concentrated in urban areas (West et al. 1993). ' Dept, of Biology, Texas State Univ., San Marcos, TX 78666, USA. ^ Texas Parks and Wildlife Dept., 4200 Smith School Rd., Austin, TX 78744, USA. 3 Corresponding author; e-mail; doveman@centurytel.net This represents a dramatic shift in habitat use away from thorn scrub and riparian wood- lands of the Tamualipan biotic province (Blair 1950) that characterizes the LRGV (West et al. 1993, Schwertner et al. 2002). Loss of native habitat and extensive agri- cultural and industrial development in the LRGV have influenced the distribution of White-winged Doves in Texas (Hayslette et al. 1996). From 1900 to 1950, about 95% of the historic, native breeding habitat was converted for human uses, resulting in significant loss of old-growth woodlands and water diversions from the Rio Grande and Arroyo Colorado (Kiel and Harris 1956, Cottam and Trefethen 1968). In addition, severe freezes occurring in 1951, 1962, 1983, and 1989 decimated citrus groves that White-winged Doves had used in- creasingly as nesting sites, most likely in re- sponse to loss of native habitat (Cottam and Trefethen 1968, George et al. 1994). A substantial proportion of White-winged Doves concentrating in urban areas north of the LRGV are non-migratory (George 1991, West et al. 1993, Hayslette and Hayslette 1999). Anecdotal evidence suggests that an extended breeding season by non-migratory doves could lead to increased recruitment, with individuals producing clutches before and after the traditional nesting period (Hays- lette and Hayslette 1999). The objective of our study was to document habitat use and productivity of White-winged Doves breeding in a recently colonized urban 172 Small et al. • URBAN WHITE- WINGED DOVES 173 il j environment. To track doves, we used subcu- j taneously implanted radio transmitters. This is the first radiotelemetry-based study of White- I winged Dove breeding ecology in a metro- politan area. METHODS We conducted our study in Waco, Texas I (McLennan County), because of its northern location and relatively recent colonization by White-winged Doves; dove densities are high t and the human population (202,983; U.S. ! Census Bureau 2000) provides potential sources of food, water, and habitat. White- winged Doves were first recorded in Waco on the Audubon Christmas Bird Count in 1990, I and they were first observed breeding there in I 1993. In 1999, 2001, 2002, and 2003, Texas ! Parks and Wildlife Department personnel con- ducted call-count surveys of White-winged 1, Doves in Waco, subsequently deriving a pop- !| ulation estimate of approximately 70,000 |l doves. ' Our study area boundary was the city limits ) of Waco. White-winged Doves preferentially congregated in older (>30 years) neighbor- 1, hoods with relatively high densities of mature i' ornamental trees. The dominant tree species, which accounted for the majority of the can- opy, were oaks (Quercus spp.) and pecan (Carya illinoinensis). We also observed that, with the exception of fall feeding flights to areas outside of Waco, doves obtained food and water locally, primarily from anthropo- genic sources. We trapped White-winged Doves using standard walk-in wire funnel traps (Reeves et ' al. 1968) baited with a 2:1 mixture of chicken I scratch and black-oil sunllower seeds (Purina I Corp., St. Louis, Missouri). In June 2002, we 1 surgically implanted subcutaneous transmit- i ters in 39 White-winged Doves (16 males, 23 I females), and, in February and March 2003, I we implanted transmitters in another 40 doves ^ (17 males, 17 females, 6 unknown sex). We I monitored doves from 10 July to 4 September I in 2002 and from 31 March to 18 June in 2003. Gender was determined using an ififant nasal speculimi to examine the cloaca and identify conical papillae in males or an ovi- duct opening in females (Miller and Wagner 1955, Swanson and Rappole 1992). We per- formed transmitter implants in the held using a portable anesthesia machine and mobile sur- gical lab (Small et al. 2004). Implanted indi- viduals were released after they had complete- ly regained a coherent state with no signs of impairment. Transmitters (Advanced Teleme- try Systems, Isanti, Minnesota) weighed 3.7 g (approximately 2.0% of body weight) and were 25 X 14 X 7 mm with an external, 16- cm-long whip antenna. All research was con- ducted in accordance with the Texas State University Institutional Animal Care and Use Committee, approval number 5QEKCT02. Using a vehicle-mounted, omni-directional antenna and a handheld, four-element, direc- tional yagi antenna (White and Garrott 1990), we tracked radio-tagged doves for the dura- tion of transmitter function (50-80 days). We documented nesting (time, date, location, and status) and habitat (tree species, nest height, and tree height) parameters. We monitored ac- tive nests every 3rd day using binoculars, and, when feasible, an extendable fiberglass pole with a mirror (Parker 1972). We calculated nest success rates using Mayfield methods (Mayfield 1961, 1975). For reasons discussed in Johnson (1979), we did not use the May- field-40% method (Miller and Johnson 1978) or the maximum-likelihood method. The Mayfield-40% method might have proven more appropriate if the mean nest-visitation rate was >15 days; the maximum-likelihood method is subject to bias unless sample sizes are large (Miller and Johnson 1978). We cal- culated standard errors and 95% confidence intervals for nesting success following John- son (1979). Both male and female White-winged Doves participate in nest building, incubation, and brooding; nests are constantly attended by at least one adult (Schwertner et al. 2002). Be- cause of constant nest attendance, we assumed equal probability of egg and nestling survival. Because White-winged Doves in urban areas do not reuse nests (White-winged Doves pro- duce multiple clutches; Gray 2002, Schaefer 2004), there was no bias due to age hetero- geneity of nests. We were unable to establish hatching dates because most nests were too high. We considered a nest acti\e if it was at- tended by an atlult. and we considered it suc- cessful if at least one young Hedged from the nest, rime to Hedging was based on a 14-day 174 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 TABLE 1. Mayfield nest success (standard error) and 95% confidence intervals, by nest attempt and year, Waco, Texas, 2002-2003. Nest attempt/year No. exposure days No. nests No. ne.sts failed Nest success (SE) 95% Cl 1 St/2002 245 13 3 0.708 (0.007) 0.701-0.715 1 st/2003 217 12 5 0.521 (0.010) 0.510-0.531 All/2002 264 14 4 0.652 (0.008) 0.644-0.660 All/2003 296 20 9 0.421 (0.010) 0.411-0.431 1 st/2002, 2003 462 25 8 0.613 (0.006) 0.607-0.619 2nd/2002, 2003 70 6 3 0.293 (0.024) 0.269-0.318 All/2002, 2003 560 34 13 0.518 (0.006) 0.517-0.524 incubation period and a 14-day brooding pe- riod (Cottam and Trefethen 1968, Schwertner et al. 2002). Nest success was calculated as (1 - [number of nests failed/number of nest ex- posure days])2^ The exponent of 28 represents combined egg and nestling exposure periods of 14 days each (Schwertner et al. 2002). Standard errors were calculated as the square root of l/( [number of nest exposure days]V [number of nest exposure days — number of failed nests] [number of failed nests]). We tested for differences in nest success be- tween years for first nesting attempts and for all attempts combined, and we tested for dif- ferences between first and second nesting at- tempts for both years combined. Nest success was considered significantly different if there was no overlap in 95% confidence intervals (Sokal and Rohlf 1995). Nest success for third and fourth nesting attempts was not calculated separately because of small sample size (n = 2). One first nest attempt in 2002 was exclud- ed from analysis because young fledged on the day we located the nest. RESULTS From 10 July to 4 September 2002, we tracked 14 of the 39 radio-tagged White- winged Doves (8 males, 6 females) to 15 nests. From 31 March to 18 June 2003, we tracked 12 of the 40 radio-tagged doves (7 males, 3 females, 2 unknown sex) to 20 nests, including 1 pair in which both individuals were radio-tagged. In 2002, seven males and six females nested once and one male nested twice. In 2003, five males and two females nested once, two males and one bird of un- known gender nested twice, one bird of un- known gender nested three times, and one fe- male nested four times. We located the 35 nests in nine tree species, primarily in pecan (48.5%) and sugarberry {Celtis laevigata-, 17%). The remaining 34.5% occurred in live oak (Quercus virginiana), ce- dar elm (Ulmus crassifolia), chinaberry (Me- lia azedarach), crapemyrtle (Lagerstroemia indica), pomegranate (Punica granatum), Tex- as oak (Q. buckleyi), and glossy privet (Li- gustrum lucidum). Mean nest height, as a pro- portion of tree height, was 0.55 in pecan, 0.41 in sugarberry, and 0.45 in the other seven tree species. Nest success was 0.652 in 2002, 0.421 in 2003, and 0.518 for both years combined (Ta- ble 1). Nest success for first nesting attempts and for all nesting attempts combined was sig- nificantly lower in 2003 than in 2002. Nest success for second nesting attempts was sig- nificantly lower than for first nesting attempts (both years combined). Nest success for all nests for both years was 0.518 (SE = 0.006; Table 1). DISCUSSION White-winged Doves in Waco, Texas, have an extended breeding season. Historically, May to mid-August has been the period of greatest White-winged Dove breeding activi- ty, particularly in the LRGV (Cottam and Tre- fethen 1968, George et al. 1994, Schwertner et al. 2002). However, in five newly colonized urban populations in Texas, hatching-year White-winged Doves have been observed ev- ery month of the year (MFS pers. obs.). Twenty-three percent of radio-marked White-winged Doves attempted more than one nesting, compared with 39% reported for Kingsville, Texas (Gray 2002). In 2003, one of our radio-marked females nested four times, the first and fourth attempts having Small et al. • URBAN WHITE- WINGED DOVES 175 been successful (Schaefer et al. 2004). Cottam and Trefethen (1968) also report multiple nest- ings during the breeding season; others list the i' mean as two broods per season (Schwertner ' et al. 2002). Overall nest success was 51.8% compared with 58% (Hayslette and Hayslette 1999) and * 53% (Gray 2002) in Kingsville, Texas, and 39 I to 73% for San Antonio, Texas (West et al. 1993). Earlier monitoring of nests in 2003, prior to the historic peak-breeding time of July (Cottam and Trefethen 1968, Schwertner et al. 2002), may have been the reason for the sig- nificant difference in nesting success between I years in Waco. When we first began monitor- i ing in 2003, nest trees had not reached max- I imum foliage development, which resulted in 1 less protective cover and possibly in increased |j nest failure from exposure to adverse weather 1 and potential predators. The majority of nests were located in de- ciduous trees. Nest-tree species were similar ‘i in growth form to woodland riparian species I native to areas traditionally used by nesting White-winged Doves in the LRGV (Cottam I and Trefethen 1968, Schwertner et al. 2002) ' and Kingsville, Texas (Gray 2002). In urban areas, shade trees such as pecan, live oak, and hackberry are important species for nesting for White-winged Doves (Nilsson 1943, Cot- tam and Trefethen 1968, West et al. 1993). Although they now nest outside the LRGV — possibly due, in part, to habitat loss (Purdy and Tomlinson 1991) — White-winged Doves seem to select nest trees with growth forms and habits similar to those of the LRGV (Hayslette et al. 1996). The nest heights that I we observed — the middle one-third of the |i tree — were consistent with those recorded in I other studies (Small et al. 1989, Gray 2002). ' Trees less than 3-m high were rarely used for nesting. Conclusions. — Fragmentation of habitat in I the LRGV, primarily due to converting native ' habitat for agriculture (Purdy and fomlinson I 1991, Brush and Cantu 1998), has resulted in I the loss of more than 95% of traditional White-winged Dove breeding habitat in fexas. In addition, changes in water-management practices, increased urbani/ation, and indus- trialization have degraded breeding habitat for White-winged Doves (CTirtis and Rijiley 1975). The distribution of White-winged Doves in Texas has undergone substantial change over the past 50 years, with the most dramatic changes beginning about 1970 (Schwertner et al. 2002). The primary change in White- winged Dove ecology has been the establish- ment of numerous new populations resulting from a northward range expansion and con- current colonizing of urban areas by breeding populations (Small et al. 1989, West et al. 1993) . To our knowledge, an increase in breeding range combined with such a dynamic change in fundamental, ontogenetically based behavior are unprecedented in bird species na- tive to the New World. The only other anal- ogous scenario has been the range expansion of the Eurasian Collared-Dove (Streptopelia decaocto); in about 1900, the species began a similar expansion of its breeding range north- ward across Europe from its core population in northern India. Breeding populations now are established as far north as Scandinavia (Hollom et al. 1988, Jonsson 1992, Ehrlich et al. 1994). The change in the distribution of White- winged Doves has revealed large gaps in our understanding of its natural history and ecol- ogy, particularly in recently established pop- ulations. Year-round residency, nesting in ur- ban environments, and breeding in every month of the year (Hayslette and Hayslette 1999) are drastic departures from dove behav- ior exhibited prior to 1950, when the species was primarily restricted to the LRGV ot Texas (Cottam and Trefethen 1968, George et al. 1994) . ACKNOWLEDGMENTS This study was conducted under Texas state permit SPR-0496-773 and U.S. Fish and Wildlife Service per- mit PRT-S()0477. ft was funded by fees paid tt) the Texas Parks and Wildlife Department by hunters pur- chasing White-winged Dove hunting stamps. We would like to thank V. R. Simpson and three anony- mous reviewers for valuable comments made on ear- lier drafts of the manuscript. litf:rature crn:D Bi AIK, W. F. 1950. I'he biotic provinces of Texas. Tex- as .lournal of .Science 2:93 1 17. Bki sii. T. AM) A. C’ANir. 199S. C'hanges in the breed- ing biixl community of subtropical evergreen for- est in the lower Rio Graiule Valley of Textis. 1970s 1990s. Texas .lournal of .Science 50:123 132. 176 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 CoTTAM, C. AND J. B. Trefethen. 1968. White-wings: the life history, status, and management of the White-winged Dove. D. Van Nostrand Company, Princeton, New Jersey. Curtis, R. L. and T. H. Ripley. 1975. Water manage- ment practices and their effects on nongame bird habitat values in a deciduous forest community. Pages 210-222 in Proceedings of the symposium on management of forest and range habitats for nongame birds. May 6-9, Tucson, Arizona (D. R. Smith, Tech. Coord.). General Technical Report WO-1, USDA Lorest Service, Washington, D.C. Ehrlich, P. R., D. S. Dobkin, D. Wheye, and S. L. Pimm. 1994. The birdwatcher’s handbook: a guide to the natural history of the birds of Britain and Europe. Oxford University Press, Oxford, United Kingdom. George, R. R. 1991. The adaptable whitewing. Texas Parks and Wildlife 49:10-15. George, R. R., E. Tomlinson, R. W. Engel- Wilson, G. L. Waggerman, and A. G. Spratt. 1994. White-winged Dove. Pages 29-50 in Migratory, shore and upland game bird management in North America (T C. Tacha and C. E. Braun, Eds.). Al- len Press, Lawrence, Kansas. Gray, M. G. 2002. Breeding biology of subcutaneous transmitter implanted White-winged Dove {Zen- aida asiatica) in Kingsville, Texas. M.Sc. thesis. Southwest Texas State University, San Marcos. Hayslette, S. E. and B. A. Hayslette. 1999. Late and early season reproduction of urban White- winged Doves in southern Texas. Texas Journal of Science 51:173-180. Hayslette, S. E., T. C. Tacha, and G. L. Wagger- man. 1996. Changes in White- winged Dove re- production in southern Texas, 1954-1993. Journal of Wildlife Management 60:298-301. Hollom, P. a. D., R. E Porter, S. Christensen, and I. Willis. 1988. Birds of the Middle East and North Africa: a companion guide. Harrell Books, London, United Kingdom. Johnson, D. H. 1979. Estimating nest success: the Mayfield method and an alternative. Auk 96:651- 661. JONSSON, L. 1992. Birds of Europe with North Africa and the Middle East. Princeton University Press, Princeton, New Jersey. Kiel, W. H. and J. T. Harris. 1956. Status of the White-winged Dove in Texas. Transactions of the North American Wildlife and Natural Resources Conference 21:376-389. Mayfield, H. E 1961. Nesting success calculated from exposure. Wilson Bulletin 73:255-261. Mayheld, H. E 1975. Suggestions for calculating nest success. Wilson Bulletin 87:456-466. Miller, H. W. and D. H. Johnson. 1978. Interpreting the results of nesting studies. Journal of Wildlife Management 42:471-476. Miller, W. J. and E H. Wagner. 1955. Sexing mature Columbiformes by cloacal characters. Auk 72: 279-285. Moore, L. 2001. Spring season roundup: March 1, 2001 through May 31, 2001. The Horned Lark 28(3):12. Nilsson, N. N. 1943. Survey, status and management of the White-winged Dove and effect of grackle control on their production. Einal progress report, September 1942-October 1943. Eederal Aid Pro- ject 1-R, Unit D, Section 2. Texas Game, Pish, and Oyster Commission, Austin, Texas. Parker, J. W. 1972. A mirror and pole device for ex- amining high nests. Bird-banding 43:216-218. Purdy, P. C. and R. E. Tomlinson. 1991. The eastern White-winged Dove: factors influencing use and continuity of the resource. Pages 255-265 in Neo- tropical wildlife use and conservation (J. G. Rob- inson and K. H. Redford, Eds.). University of Chi- cago Press, Chicago, Illinois. Reeves, H. M., A. D. Geis, and P. C. Kniffin. 1968. Mourning Dove capture and banding. U.S. Pish and Wildlife Service, Special Scientific Report, no. 117. Washington, D.C. Rogers, J. 1998. White-winged Dove at Slave Lake, Alberta. Alberta Naturalist 28:17-18. Schaefer, C. L. 2004. White-winged Dove move- ments and reproduction in a recently colonized ur- ban environment. M.Sc. thesis, Texas State Uni- versity, San Marcos. Schaefer, C. L., M. P. Small, J. T. Baccus, and G. L. Waggerman. 2004. Pirst definitive record of more than two nesting attempts by wild White- winged Doves in a single breeding season. Texas Journal of Science 56:179-182. ScHWERTNER, T. W, H. A. Mathewson, J. A. Rober- son, M. Small, and G. L. Waggerman. 2002. White-winged Dove (Zenaida asiatica). The Birds of North America, no. 710. Small, M. E, J. T. Baccus, and G. L. Waggerman. 2004. Mobile anesthesia unit for implanting radio transmitters in birds in the field. Southwestern Naturalist 49:279-282. Small, M. E, R. A. Hilsenbeck, and J. P. Scudday. 1989. Resource utilization and nesting ecology of the White-winged Dove {Zenaida asiatica) in cen- tral Trans-Pecos, Texas. Texas Journal of Agricul- ture and Natural Resources 3:37-38. SoKAL, R. R. AND P. J. Rohlf. 1995. Biometry, 3rd ed. W. H. Preeman, New York. Swanson, D. A. and J. H. Rappole. 1992. Determin- ing sex of adult White-winged Doves based on cloacal characteristics. North American Bird Bander 17:137-139. U.S. Census Bureau. 2000. Census 2000. U.S. De- partment of Commerce, Washington, D.C. West, L. M., L. M. Smith, R. S. Lutz, and R. R. George. 1993. Ecology of urban White- winged Doves. Transactions of the North American Wild- life and Natural Resource Conference 58:70-77. White, G. C. and R. A. Garrott. 1990. Analysis of wildlife radio-tracking data. Academic Press, San Diego, California. Wilson Bulletin 1 17(2): 177— 184, 2005 SPOTLIGHT SURVEYS FOR GRASSLAND OWLS ON SAN CLEMENTE ISLAND, CALIFORNIA ANNE M. CONDON,' ERIC L. KERSHNER,' ^ BRIAN L. SULLIVAN,' ^ DOUGLASS M. COOPER,' AND DAVID K. GARCELON^ ABSTRACT. — According to Breeding Bird Survey data, grassland birds are among the most imperiled species in North America. Within this group, grassland owls show steep population declines across the United States. Despite these declines, questions still remain regarding the seasonal and geographic distribution of grassland owls. On San Clemente Island (SCI), California, grassland owls are known to occur, but nothing is known about their distribution or abundance. To increase our understanding of owl populations on SCI, we used night-time spotlighting to survey for grassland owls from October 2001 to October 2002. We recorded 733 detections of three species of owls: Barn Owl {Tyto alba). Burrowing Owl {Athene cunicularia), and Short-eared Owl {Asio flammeus). Barn (8.3 ± 0.8 owls/hr) and Burrowing owls (2.2 ± 0.7 owls/hr) were the most frequently detected species, whereas Short-eared Owls were rarely detected (0.2 ± 0.1 owls/hr). We detected owls during all night- time hours surveyed and detected Barn Owls in every month of the study. We detected Burrowing Owls only from October to March and Short-eared Owls from December to April, suggesting that they are winter visitors. Despite the bias of increased detectability using roadside surveys, spotlighting from a vehicle enabled us to efficiently cover a large proportion of the island (compared to walking surveys) and survey multiple grassland species using one survey technique. Received 8 August 2003, accepted 22 February 2005. Grassland birds are among the most imper- iled wildlife in North America (Peterjohn and Sauer 1999, Sauer et al. 2004), and, within ; this group, owls are considered species of conservation concern in most North American : regions (Wellicome and Haug 1995, Herkert et al. 1996, Sheffield 1997, U.S. Fish and Wildlife Service 2002). Biologists visiting and I working on San Clemente Island (SCI), Cali- ' fornia, have observed Barn (Tyto alba). Bur- rowing (Athene cunicularia), and Short-eared (Asio flammeus) owls at various times of the year and have documented breeding by Barn ' Owls (BLS and ELK unpubl. data). However, I little else is known about the owl populations ' on SCI. ' Grasslands compose 30% (—4,300 ha) of I SCI’s vegetation community; thus, there is I ample habitat for grassland owls. The pres- ! ence of large, open grasslands on SCI has re- I suited from the island’s history of ranching I and the introduction of feral grazers and ex- I otic grasses in the mid-lSOOs (Andrew 1998). ' fhese introductions dramatically altered the I I ' Inst, for Wildlife .Studies, 2515 C'amino del Rio South, Ste. 334, San Diego, ('A n2l()8, USA. ’ Inst, for Wildlife Studies. B.O. Box 1 104. Areata, C'A 95518. USA. ' Chirrent atklress: ('ornell Lab of Ornithology, 159 .Sapsucker Wt)ods Rd., Ithaca, NY 14850. U.SA. ■* Corresponding tuithor; e-mail: kershnerC^' iws.org landscape by changing the shrub component of the native coastal chaparral habitats to open grasslands (Coblentz 1980; BLS and ELK un- publ. data). In 1993, however, feral grazers were removed from SCI; as a result, succes- sional change has been allowed to take place and the grasslands are reverting to more nat- ural, shrubby communities. Due to successional change, the conserva- tion status of the island’s owls, and our lack of knowledge about grassland owls on SCI, we examined the presence/absence, relative abundance, and distribution of grassland owls on SCI. We hope to provide a better under- standing of how grassland owls use SCI and determine how the successional transition of grassland habitats may effect these owl pop- ulations in the future. METHODS Study area.—SCl (32° 50' N, 118° 30' W) is located approximately 109 km northwest of San Diego, California, and is the southern- most California Channel Island, fhe 14,603- ha island is 34 km long and 2. 4-6. 4 km wide. A relatively level, open plateau runs the length of the island, with elevations ranging from sea level to 599 m. Deep canyons of varying lengths incise the jilatcau from the east and west sides, 'fcmpcraturcs range from 6 to 37° C' and mean annual precipitation is 17.8 cm (C’alifornia State Northridge, Depart- 177 178 THE WILSON BULLETIN • Vol. 1 17, No. 2, June 2005 ment of Geography unpubl. data, 1998-2002). Fog is common, especially in the summer. Prevailing winds are from the west, and windy days are frequent throughout the year (typi- cally Beaufort scores of 2-3). SCI is admin- istered by the U.S. Navy and is used for active military training as part of the Southern Cal- ifornia Offshore Range; however, the U.S. Navy has an environmental program to protect natural and cultural resources (U.S. Depart- ment of the Navy 2001). Suitable owl habitat (i.e., grasslands and maritime desert scrub) is found predominantly on, and surrounding, the island’s large central plateau. Grasslands comprise native and non- native species (Avena spp., Bromus spp., Nas- sella pulchra) and scattered shrubs such as coyote brush (Baccharis pilularis)\ however, after the removal of feral grazers in 1993, shrub cover has increased (J. Dunn pers. comm.). Maritime desert scrub is dominated by boxthorn (Lycium calif ornicum), snake cactus {Bergerocactus emoryi), cholla {Opun- tia prolifera), prickly pear cactus (Opuntia lit- toralis), California sagebrush {Artemisia cal- ifornica), and morning glory (Calystegia rna- crostegia). See Raven (1963) and Kellogg and Kellogg (1994) for a more detailed description of SCI’s vegetation. Survey technique. — Because of the inacces- sible nature (i.e., steep, rocky canyons) of po- tential nesting habitat for some owl species and the limited availability of personnel to search the vast grassland expanses, we sur- veyed for owls along established island roads. We established eight 10-km transects (Fig. 1). We selected transect starting points randomly while ensuring that no two transects over- lapped. Although SCI roads were not estab- lished randomly and roadside surveys are as- sociated with certain biases (Bart et al. 1995, Keller and Scallan 1999), the layout of the island road system offered access to most of the open grassland and maritime desert scrub habitat; the view from the roads was typically unobstructed on either side. Our survey tran- sects sampled approximately 55% (77.5 km) of the available roads on SCI, and provided a representative sample of owl habitat across the island (i.e., they traversed —34% of the grassland on the island). We surveyed each transect once per month over a 13-month period (October 2001 to Oc- tober 2002) for a total of 104 surveys (13 all- island surveys). We tried to survey as many of the eight transects in one night as possible, and each month we randomized the order in which we surveyed the eight transects. We conducted surveys by driving transects in a truck at night and using spotlights to locate owls (hereafter spotlighting). The driver and passenger, equipped with 750,000-candle power spotlights, scanned both sides of the road, making full sweeps of the plateau and road ahead while driving 16-32 km/hr (de- pending on road conditions). We used binoc- ulars (7 X 42 and 8 X 42) to identify species and plotted the locations of flying or perched birds on a topographic map. We recorded the time of detection, species, and behavior at de- tection (e.g., perched, hunting, flushed) for each individual located. Some transects (e.g., R3, R4, and R5) in- cluded multiple dead-end spur roads; in these situations we backtracked over the same road in order to resume the survey, only recording observations while traveling in the initial di- rection along the spur. From March to October 2002, one transect (R2) was shortened to 6 km due to a change in the accessibility to that part of SCI. We surveyed the shortened route for those 8 months, and adjusted the total distance surveyed to 76 km, rather than 80 km. Under optimal weather conditions (e.g., clear skies, no fog), the maximum distance at which we could reliably detect owls was ap- proximately 250 m (determined using a Barn Owl replica, spotlight, and digital rangefin- der). We did not conduct surveys in fog or rain, or when wind exceeded a score of 6 on the Beaufort scale (—40-50 km/hr). Temper- atures between 12 and 14° C, cloud cover be- tween 0 and 25%, and wind speed of 2 or 3 on the Beaufort scale (—8-19 km/hr) were typical survey conditions. Because SCI is an active training facility for the U.S. Navy, designing a straightforward survey design was challenging. We had to ad- just our methodology to account for geograph- ic and temporal (both seasonal and hourly) ac- cess restrictions, usually on short-notice. On some nights we were denied access to certain areas of the island. When we were unable to survey all transects in one night, we finished the surveys on the next available date when access was granted. These restrictions created Condon et al. • SPOTLIGHTING OWLS ON SAN CLEMENTE ISLAND 179 uneven survey coverage; no surveys were conducted during some time-blocks (i.e., 10, I I, and 12 hr past sunset) and, during others, we were given regular access. I'liese access constraints prevented us from standardi/ing how transects were surveyed over various time-blocks, which coidd iiinuence survey re- sults if there are time-dependent associatiofis in owl acti\ ity. However, because we hatl little control over when each transect could be sur- veyed, these constraints simply aided the ran- domi/ation of our design. Data analy.si.s. — I'o determine |')at terns of temporal and seasonal activity, ue ( I ) summed the amount of time surveyed in each hour alter sunset for each month ot the study, (2) totaled the number of owl detections u ith- in each 1-hr time block, and (3) calculated the 180 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 12 10 - 8 - 0.9 1/5 c s ® 4 - 2 - 4.4 14.6 14.6 20.8 10.5 1.0 0.3 0.3 □ Barn Owl □ Burrowing Owl ■ Short-eared Owl 0.5 6 7 8 Hour after sunset 10 11 12 13 FIG. 2. Barn Burrowing, and Short-eared owl detections/hr during I -hr blocks after sunset for spotlighting surveys on San Clemente Island. California, 2001 and 2002. Survey effort (total hr surveyed) shown above bars number of owl detections/hr of effort sur- veyed for each time block. The number of de- tections/hr represents relative abundance rath- er than the number of individuals, as any one owl might have been observed on more than one occasion on a given night, despite our ef- forts to reduce double counting. Means are presented ± SE. RESULTS We completed 68 survey hr on 104 tran- sects (i.e., 8 transects surveyed 13 times). The mean number of transects surveyed per night was 2.9 ± 0.25 (range - 1-8). Most of our survey efforts were between 2 and 6 hr after sunset in = 64.9 hr, 96%). Each transect re- quired 30-70 min (mean completion time = 39.2 min) to survey, depending on road con- ditions and the number of owls observed. Presence/absence. — During 13 surveys, we recorded 733 owl detections of three species: Barn {n = 561), Burrowing (/? = 161), and Short-eared {n = 11) owls. We detected Barn Owls on 89 of 104 (85.6%) transects. Burrow- ing Owls on 47 (45.2%), and Short-eared Owls on 9 (8.6%). We did not detect any owls on 8 of 104 (7.7%) transects. Relative abundance. — We recorded a mean of 8.3 ± 0.8 Barn Owl detections/hr (range = 3.3-10.7) over the course of the study. We consistently detected Barn Owls 1-8 hr after sunset, despite varying levels of effort (Fig. 2), and detected the fewest Bam Owls/hr 9 and 13 hr after sunset. Almost half (46%, 259 of 561), of all Barn Owl observations were on transects R4 and R5. For all months, we de- tected 2.2 ± 0.7 (range = 0—4.0) Burrowing Owls/hr; excluding months when Burrowing Owls were presumably absent from the island, we detected 4.0 ± 0.6 per hr. Burrowing Owl activity was limited to 1—6 hr after sunset or early morning hours (i.e., 13 hr after sunset; Fig. 2). We observed 68% of the Burrowing Owls on transect Rl, R2, and R3. We detected 0.2 ±0.1 (range = 0-2.2) Short-eared Owls/ hr for all months, and 0.4 ± 0.3 per hr ex- cluding months when this species was pre- sumably absent from the island. We detected Short-eared Owls between 1 and 6 hr after sunset and on all transects except R7. We observed Bam Owls every month of the year, which supports previous breeding re- cords. We observed the greatest number of Barn Owls/hr in June and the fewest in Oc- tober 2002 (Fig. 3). Burrowing Owls were ob- served only from October 2001 to March 2002 and in October 2002; during those times, they were detected on 84% (47/56) of the Condon et al. • SPOTLIGHTING OWLS ON SAN CLEMENTE ISLAND 181 Survey month FIG. 3. Barn, Burrowing, and Short-eared owl detections/hr by month for spotlighting surveys on San Clemente Island, California, October 2001 -October 2002. Survey effort (total hr surveyed) for each month shown above bars. transects. Their absence between April and September indicates that they are primarily winter visitors. We observed Short-eared Owls on five occasions between 12 December 2001 and 7 April 2002. Owl behavior. — Forty-seven percent of the Barn Owls were first detected in flight {n — 262), and 53% were perched {n = 299). Barn Owls perched primarily on utility wires (n = 157, 53% of perched observations), but also were seen on power poles, fences, junk piles, buildings, rocks, signs, shrubs, the ground, and the road (n = 89). Burrowing Owls were detected both in flight (32% of detections, n = 51) and when perched (68%, n = 110). Burrowing Owls were most commonly found on dirt/gravel roads (n = 66), but they also perched on utility wires, junk piles, rocks, and I the ground (n = 18). We observed 73% (// = 8) of Short-eared Owls in flight, compared with 27% (n = 3) that were perched. I DISCUSSION We detected all three species of grassland owl on SCI, and our data suggest that SCI is an important wintering ground for each spe- cies. We found Barn Owls year-round sug- gesting resident status, whereas Burrowing and Short-eared owls appear to be winter res- idents only. Burrowing Owls were the second most common species detected October through March; we recorded no detections during the breeding season. Burrowing Owls from northern breeding grounds migrate south in September and October and north in March and April (Haug et al. 1993), consistent with when we observed them on SCI. Occurrence of Short-eared Owls is irregular; they arrive in large numbers and winter on SCI only dur- ing certain years (BLS and ELK unpubl. data). The importance of SCI for wintering owls brings up an important question: how will the natural succession of grassland habitat (in the absence of feral grazers) impact Barn, Bur- rowing, and Short-eared owls on SCI? As the grasslands become shrubbier, reverting to a more natural “pre-grazing” condition, we an- ticipate some impacts on wintering owl pop- ulations, as all three species prefer large, open grassland habitats with little shrub or tree cov- er (Marti 1992, Haug et al. 1993, Holt and Leasure 1993). Burrowing Owls use short- structured vegetation, including uncultivated fields, for foraging (Haug and Oliphant 1990) — presumably due to increased visibility of prey in those types (Konrad and Gilmer 19S4). Reforestation (i.e., succession in this 182 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 case) generally constitutes habitat loss for Short-eared Owls (Holt and Leasure 1993). Owl behavior.— AW three species are thought to be primarily crepuscular foragers, especially in winter (Marti 1992, Haug et al. 1993, Holt and Leasure 1993). However, we found that all three species were active during the first 8 hr after sunset. Barn Owls appear to be active during all hours of the night. It is more difficult to assess Burrowing Owl activ- ity because, during the months when this spe- cies was detected, we surveyed only 8 of the 13 1-hr blocks after sunset. It appears that Burrowing Owls are equally active in early morning (13 hr after sunset) and early evening hours (Fig. 2). We detected Short-eared Owls primarily in the first hour after sunset. On SCI, Barn Owls regularly use power lines for perching, and they may be drawn to roadsides where other man-made structures serve as perches. Bam Owls are well adapted to using urban landscapes and have a habit of hunting near roads, especially in winter (Kon- ig et al. 1999). Over half of all Bam Owls detected were perched, and of these, 53% were on utility wires. The transects with the most Bam Owl observations were situated along the main road, and utility poles are sit- uated along its entire length. We detected the majority of Burrowing Owls on dirt/gravel roads, where they might be attracted to the bare ground in an otherwise dense, grassy habitat. Burrowing owls are known to forage in uncultivated fields (Haug et al. 1993) and along the edges of roads (Ger- vais et al. 2003). Sixty-eight percent of all Burrowing Owls detected were perched on the ground, 60% of which were on dirt/gravel roads. Burrowing Owls appear to forage along or perch on dirt/gravel roads more than paved roads. We detected them most often on three transects, approximately 66% of which were dirt/gravel roads (n = 17 km). Unlike larger grassland owls. Burrowing Owls forage pri- marily on the ground and are not as visible in flight (Haug et al. 1993). Use of spotlighting as a sun'ey technique for grassland owls. — Spotlighting is a widely used technique for surveying multiple wildlife taxa at night (e.g., mammals [Focardi et al. 2001], spiders [Martin and Major 2001], and reptiles and amphibians [Corben and Fellers 2001]). Spotlighting has been used to locate roosting birds in forest habitats (Lindenmayer 1 et al. 1996), as well as roosting seabirds and I waterfowl (Snow et al. 1990, King et al. 1994, ^ Whitworth et al. 1997). Debus (1995), how- ever, found that spotlighting without audio cues while driving between survey points was ineffective for detecting forest owls. We believe that spotlighting is an appropri- ate method for surveying grassland owls be- cause these species use mostly open habitats and are visible at night while foraging (i.e., low quartering flight over vegetation or scan- ning for prey while perched). Furthermore, most grassland owls are light colored on their ventral side, improving detection when illu- minated (Marti 1992, Holt and Leasure 1993, Marks et al. 1994). Grassland owls are typi- cally less vocal than forest owls, especially outside of the breeding season, making tradi- tional call-playback techniques less effective in winter (Heintzelman 1965, Haug et al. 1993, Holt and Leasure 1993, Marks et al. 1994, Toms et al. 2001, Conway and Simon 2003). Using high-powered spotlights, we were able to efficiently survey a large proportion of SCFs grassland habitat for foraging owls. The alternative to roadside spotlighting — hiking across rugged terrain at night — would have taken substantially longer. A study comparing three survey techniques for Burrowing Owls indicated that line-transect surveys are the least effective means of surveying in the breeding season (Conway and Simon 2003). Thus, spotlighting for owls during roadside surveys might give us the best chance to cover a large area with the least number of observers while collecting valuable data. We believe spotlighting may be useful for determining the status of owls where they are potentially at risk, or where data are lacking, especially during the non-breeding season when these species might not be as responsive to tape playback methods (Haug et al. 1993). Spotlighting might be a useful tool in esti- mating presence/absence in any open area, during any time of year. It might be especially useful to conduct statewide surveys, especial- ly in the Midwestern and western United States, where long stretches of road cut through open habitat suitable for these spe- cies. This technique may also be used to quickly locate regularly used areas or ascer- Condon et al. • SPOTLIGHTING OWLS ON SAN CLEMENTE ISLAND 183 . tain periods of activity for more intensive I monitoring or research efforts. Potential drawbacks to spotlighting surveys I are (1) road noise, (2) the possibility of mis- taking spotlighting for illegal poaching, and (3) being limited to habitat adjacent to roads, which may not accurately represent overall habitat and may inflate or decrease detection depending on species (Bart et al. 1995, Keller and Scallan 1999). In our study, we found in- creased detectability (possibly due to in- creased abundance) near roads for Barn and Burrowing owls, which may be influenced by the increased number of perches and the fact that most roads were dirt. Thus, the potential biases, as well as safety issues, associated with roadside surveys should be thoroughly evaluated prior to using this technique in other situations. ACKNOWLEDGMENTS This study was funded by the Commander in Chief, Pacific Fleet, through Commander, Navy Region ' Southwest Environmental Department, under contract number N687 1 1-99-C-6665 to the Institute for Wild- life Studies, with Naval Facilities Engineering Com- mand Southwest Division. We thank the U.S. Navy ! Region Southwest, Natural Resources Office, and Southwest Division, Naval Facilities Engineering Command— San Diego, California for logistical and technical support. We thank J. W. Walk, B. Millsap, : and D. Rosenberg for reviewing early drafts of this manuscript. LITERATURE CITED Andrhw, V. R. 1998. Historical/geographical study of San Clemente Isle. M.A. thesis, California State University, Long Beach. Bart, J.. M. Hof-scuen, and B. G. Piterjofin. 1995. Reliability of the Breeding Bird Survey: effects of I restricting surveys to roads. Auk 1 12:758-761. CoBi.FiNT/, B. E. 1980. Effects of goats on Santa Cat- alina ecosystem. Pages 167—170 in Fhe California j Channel Islands: proceedings of a multidisciplin- ary symposium (D. M. I^)wer, lul.). Santa Barbara Museum of Natural History. Santa Barbara, C'ali- tornia. . Conway, C. .1. and J. C. Simon. 200.^. C’omparison of I detection probability associated with Burrowing I Owl survey methotls. .lournal ot Wildlife Man- agement 67:501-51 1. ' C’oRFUiN, C. AND G. M. I f i.i I RS. 2001. A technique for detecting eyeshine of amphibians aiul reptiles, i Herpetological Review 32:89 91. , DiiiU'S, S. J. S. 1995. Surveys of large forest owls in j northern New South Wales: methodology, ealling I behaviour and owl responses. C'orella 19:.f8 50. Focardi, S., a. M. De Marinis, M. Rizzotto, and A. Pucci. 2001. Comparative evaluation of thermal infrared imaging and spotlighting to survey wild- life. Wildlife Society Bulletin 29:133-139. Gervais, j. a., D. K. Rosenberg, and R. G. Anthony. 2003. Space use and pesticide exposure risk of male Burrowing Owls in an agricultural land- scape. Journal of Wildlife Management 67:155- 164. Haug, E. a., B. a. Millsap, and M. S. Martell. 1993. Burrowing Owl {Athene cunicularia). The Birds of North America, no. 61. Haug, E. A. and L. W. Oliphant. 1990. Movements, activity patterns, and habitat use of Burrowing Owls in Saskatchewan. Journal of Wildlife Man- agement 54:27-35. Heintzelman, D. S. 1965. Distribution and population density of Barn Owls in Lehigh and Northampton counties, Pennsylvania. Cassinia 49:2-19. Herkert, j. R., D. W. Sample, and R. E. Warner. 1996. Management of Midwestern grassland land- scapes for the conservation of migratory birds. Pages 89-116 in Management of Midwestern landscapes for the conservation of Neotropical birds (E R. Thompson, III, Ed.). General Techni- cal Report NC-187, USDA Forest Service, North Central Forest Experiment Station, Detroit, Mich- igan. Holt, D. W. and S. M. Leasure. 1993. Short-eared Owl (Asio fiammeus). The Birds of North Amer- ica, no. 62. Keller, C. M. E. and J. T. Scallan. 1999. Potential roadside biases due to habitat changes along Breeding Bird Survey routes. Condor 101:50-57. Kellogg, E. M. and J. L. Kellogg. 1994. San Cle- mente Island vegetation condition and trend and the elements of ecological restoration. Prepared for Southwest Division Naval Facilities Engineer- ing Command, San Diego, California. Tierra Data Systems, Reedley, California. King, D. T, K. J. Andrews, J. O. King, R. D. Flynt, J. F. Glahn, and j. L. Cu.mmings. 1994. A night- lighting technique for capturing Cormorants. Jour- nal of Field Ornithology 65:254-257. Konig, C., F Weik, and J. H. Bi^cking. 1999. Owls. Yale University Press, New Haven, Connecticut. Konrad, P. M. and D. S. Gilmer. 1984. Observations on the nesting ecology of Burrow ing Owls in cen- tral North Dakota. Prairie Naturalist 16:129-130. Lindi;nmayi;r, D. B., M. P. Pof>f;, R. B. Ct nningham, C'. !•: Donnf LI Y, AND H. A. Nix. 1996. Roosting of the Sulphur-crested Cockatoo (Cacatua yider- ita). \i\nu 96:209-212. Marks, .1. S.. I). L. Faans, and D. W. Holt. 1994. Long-cared Owl {A.\io oin.\). The Birds of North America, no. 133. M\rii, C. I). 1992. Barn Owl { t\io (dha). The Birds of North America, no. I. M \RiiN. T .1. AND R. F'. M ajor. 2001. C'hanges in wolf spider (.Araneae) assemblages across wootlland- [■>asture bouiularies in tlie central wheat-belt of 184 THE WILSON BULLETIN Vol. 117, No. 2, June 2005 New South Wales, Australia. Austral Ecology 26: 264-274. Peterjohn, B. G. and J. R. Sauer. 1999. Population status of North American grassland birds from the North American Breeding Bird Survey, 1966- 1999. Studies in Avian Biology 19:27-44. Raven, P. H. 1963. A flora of San Clemente Island, California. Aliso 5:289-347. Sauer, J. R., J. E. Hines, and J. Fallon. 2004. The North American Breeding Bird Survey, results and analysis 1996-2004, ver. 2004.1. Patuxent Wildlife Research Center, Laurel, Maryland. Sheffield, S. R. 1997. Current status, distribution, and conservation of the Burrowing Owl {Speotyto cunicularia) in Midwestern and western North America. Pages 399-407 in Biology and conser- vation of owls of the northern hemisphere; second international symposium, February 5-9, 1997 (J. R. Duncan, D. H. Johnson, and T. H. Nicholls, Eds.). Winnipeg, Manitoba, Canada. General Technical Report NC-190, USD A Forest Service, North Central Forest Experiment Station, St. Paul, Minnesota. Snow, W. D., H. L. Mendall, and W. B. Krohn. 1990. Capturing Common Eiders by night-lighting in coastal Maine. Journal of Field Ornithology 61: 67-72. Toms, M. P, H. Q. P. Crick, and C. R. Shawyer. 2001. The status of breeding Barn Owls (Tyto alba) in the United Kingdom 1995-97. Bird Study 48:23-37. U.S. Department of the Navy, Southwest Division. 2001. San Clemente integrated natural resources management plan draft final. Prepared by Tierra Data Systems, Escondido, California. U.S. Fish and Wildlife Service. 2002. Birds of con- servation concern 2002. Division of Migratory Bird Management, Arlington, Virginia, http:// migratorybirds.fws.gOv/REPORTS/ BCC2002.PDF. Wellicome, T. I. AND E. A. Haug. 1995. Second up- date of status report on Burrowing Owl in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, Ontario, Canada. Whitworth, D. L., J. Y. Takekawa, H. R. Carter, AND W. R. McIver. 1997. A night-lighting tech- nique for at-sea capture of Xantus’ Murrelets. Co- lonial Waterbirds 20:525-531. Wilson Bulletin 1 17(2):185— 188, 2005 FERRUGINOUS PYGMY-OWLS: A NEW HOST EOR PROTOCALLIPHORA SIALIA AND HESPEROCIMEX SONORENSIS IN ARIZONA GLENN A. PROUDFOOX'J JESSICA L. USENER,^ AND PETE D. TEEL^ ABSTRACT. — While banding Cactus Ferruginous Pygmy-Owls (Glaucidium brasilianum cactorum) in Ari- zona, we removed three Protocalliphora sialia (Diptera: Calliphoridae) from the wing margin of one nestling. Subsequent inspection of nest material revealed an additional 119 Hesperocimex sonorensis (Hemiptera: Cimic- idae), another hematophagous parasite. All nestlings {n = 3) fledged successfully, but on day 8 postfledging, two fledglings were found dead and one was missing. Although unsubstantiated, the subclinical effect (e.g., anemia) of these hematophagous parasites may have contributed to the fledglings’ demise. This is the first published record of P. sialia parasitizing Ferruginous Pygmy-Owls and the first documented infestation of H. sonorensis for nesting Ferruginous Pygmy-Owls. Received 2 August 2004, accepted 23 February 2005. Cactus Ferruginous Pygmy-Owls {Glauci- dium brasilianum cactorum, hereafter pygmy- owl) are secondary obligate cavity nesters that require mature trees, including large columnar ; cacti, for nesting (Proudfoot and Johnson i 2000). In March 1997, the U.S. Fish and i Wildlife Service listed the pygmy-owl as en- dangered in Arizona (U.S. Fish and Wildlife ! Service 1997). In 1999, only 41 adult pygmy- owls were known to exist in Arizona. In 2000 ! and 2001, population sizes in Arizona were 34 and 36 adults, respectively (U.S. Fish and ' Wildlife Service 2003). On 2 June 2002, during a cooperative study ] of nesting ecology and phylogeography of I pygmy-owls in Arizona, we removed three dipteran larvae from the right wing of one pygmy-owl nestling. Larvae were incidentally discovered and then removed during routine banding of nestlings. The larvae, later identi- fied by T. L. Whitworth as P. sialia (Diptera: ' Calliphoridae), were on the wing margin be- tween secondary remiges number 5 and 6, 6 and 7, and 10 and 1 I. We preserved larvae in 95% ethanol and vouchered samples as study specimens at the Texas Cooperative Wildlife Collection at Texas A&M University in Col- lege Station. Subsequent examination of the infested nestling's siblings revealed no addi- I I ' Dept, of Wikllifc ami bislicrics Sciences. Texas A&M Univ., 2258 TAMU. College Station. TX 77843. USA. ‘ Dept, of Fjitomology, Texas A&M llniv., 2475 TAMU, College Station. TX 77843, USA. ’ Ctirrespomling author; e-mail; gproiKlfootC«hamu.edu tional ectoparasites. To the best of our knowl- edge, this is the first record of P. sialia par- asitizing pygmy-owls. The nest cavity was 3.5 m above ground level in a saguaro cactus {Carnegiea gigantea) in the Altar Valley southwest of Tucson, Ar- izona. The entrance diameter (7.5 X 9.0 cm) was large enough to remove nestlings and nest material by hand. After the nestlings fledged, we removed and examined nest material for additional P. sialia; none were found. How- ever, we did collect 119 Hesperocimex sono- rensis (Hemiptera: Cimicidae), another he- matophagous parasite. To the best of our knowledge, this is the first published record of H. sonorensis infesting a pygmy-owl nest cav- ity. Due to funding and time limitations, nest material was not examined from any other pygmy-owl nest cavities. The Calliphoridae mostly comprise ne- crophagous fly species that, in the larval stage, consume carrion or decaying flesh in wounds, and are generally known as blow flies (Mullen and Durden 2002). Larval Protocalliphora, however, are hematophagous parasites that commonly feed on nestlings of nidicolous birds (Hill and Work 1947, Bohm 1978, Bo- land et al. 1989, Merino and Botti 1998). Few studies have shown a direct link between Pro- toccdliphora infestations and nestling mortal- ity or reductions in nest productivity (Ciold and Dahlsten 1983, Roby et al. 1992). How- ever, recent stutlies have found evidence of indirect links between hematophagous para- sites and nestling-to-fledgling survival. I'or example, in House Wrens ( / roglodytes aedon) 186 THE WILSON BULLETIN • Vol. ! 17, No. 2, June 2005 a >25% loss in hemoglobin levels was attri- buted to blood feeding by P. parorum and Denncmyssus hinidinis (a mite; Acari; Mesos- tigmata: Dermanyssidae). A hemoglobin de- ficiency of this magnitude may significantly reduce the transport of oxygen to tissues. If fledglings retain low hemoglobin and oxygen levels, their anemic state may have a negative effect on the birds’ survivorship by reducing the ability to sustain flight and escape preda- tors (O’Brien et al. 2001). In Blue Tits {Pams caeruleus), there was a strong negative cor- relation between the heritability of chick body size and Protocalliphora infestation, as young of infested nests produced offspring with a shorter than average tarsus (Charmantier et al. 2004). The Cimicidae includes about thirty species of blood-feeding ectoparasites world wide. In birds, infestation of Oeciacus vicarius was at- tributed to the abandonment of nest houses used by adult Purple Martins (Progne subis), and to the death of 10 nestlings that fledged prematurely (Loye and Ragan 1991). In Ne- braska, high infestation of O. vicarius was credited with reduced body condition and sea- sonal decline in reproductive success of Cliff Swallows {Petrochelidon pyrrhonota\ Brown and Brown 1986, 1999). Continued study showed that parasitized nestlings had in- creased asymmetry in wing and tail feathers, possibly due to nutritional stress resulting from blood loss. Feather asymmetry may im- pair flight performance and reduce foraging efficiency, a possible fitness cost to Cliff Swallows (Brown and Brown 2002). In New Mexico, infestation of Haematosiphon ino- dorus was credited with the abandonment of one Prairie Falcon {Falco mexicanus) nest (three eggs), and with the death of seven Prai- rie Falcon (broods of three and four) and two Red-tailed Hawk {Buteo jamaicensis) nest- lings (Platt 1975). We know of no studies citing Protocalli- phora or Cimicidae infestation as the cause of a significant reduction in overall numbers of any avian species; thus, it is likely that a co- existence has developed between parasite and host (Gold and Dahlsten 1983). However, we would not rule out the possibility that heavy hematophagous parasite infestations may be detrimental to populations of species with low numbers that are under extreme environmental stress. The three nestlings banded on 2 June 2002 were monitored to fledging (15 June) and for 8 days postfledging. Eight days postfledging, the nestling from which we removed the P. sialia was found dead at the base of a saguaro cactus. The carcass was intact with no sign of depredation or scavengery. That same day, an- other fledgling was found dead. The carcass was found in a saguaro cavity, and plucked feathers were visible at the entrance. AGF (Arizona Game and Fish Department) re- searchers could not determine whether the nestling was depredated or if it had died and then was scavenged. A concentrated effort (~1 hr) by six researchers failed to locate the remaining fledgling. AGF researchers returned to the nest area on three occasions and could not locate the third fledgling (D. J. Abbate pers. comm.). Because pygmy-owl fledglings do not disperse from their natal area until —56 days postfledging (Proudfoot and Johnson 2000; GAP pers. obs.), AGF researchers as- sumed the remaining fledgling was also dead. Although pygmy-owls commonly reuse nest cavities (Weidensaul 1989), this nest cavity was not active during the next season (2003; D. J. Abbate pers. comm.). Notably, Cliff Swallows avoid nesting in areas with previ- ously high infestation levels of O. vicarius (Brown and Brown 1992). There is no direct evidence that parasitic blood loss had an effect on the survival of these pygmy-owls. It is possible that drought conditions in the Tucson Basin during 2002 (http://www.wrh.noaa.gov/twc/climate/ seazDM.php) were a contributing factor. However, after reviewing recent research on Protocalliphora and Cimicidae, we would not rule out parasitic blood loss as a factor con- tributing to the mortality of these fledglings. Using hand removal of nest material, we col- lected 119 H. sonorensis (~40/nestling). Av- erage infestation of O. vicarius in Barn Swal- low and Cliff Swallow nests was 19 and 32/ nestling, respectively (Orr and McCallister 1985). Brown and Brown (1992) reported av- erages of 199 and 565 O. vicarius/nest site. Assuming we collected 100% of the ectopar- asites from the nest cavity, the parasite load ('--40/nestling) we report exceeded levels re- ported by Orr and McCallister (1985), but it Proudfoot et al. • PROTOCALLIPHORA AND HESPEROCIMEX IN PYGMY-OWLS 187 j was considerably less than the deleterious in- 1 festation levels reported by Brown and Brown (1986, 1992, 2001, 2003). Cimicidae, how- ever, are considered nocturnal and are known to crawl into cracks and crevices during day- light (Usinger 1966). Thus, extracting nest material by hand during daylight most likely provided a conservative representation of H. sonorensis infestation. Hand removal of nest i material also may have resulted in failure to extract mobile P. sialia larvae or puparia that were located in cavity crevices. In addition, as poikilothermic organisms, the growth rate of Protocalliphora is essentially a function of tem- perature (growth rate increases linearly with temperature; Adams and Hall 2003). Thus, with an average daily high temperature of >30° C during May and June in Tucson, Arizona (http://wc.pima.edu/Bfiero/tucsonecology/ ! climate/stats.htm), we suspect that the life cycle of P. sialia in the Altar Valley of the Sonoran i Desert is at or near the 1 8-day minimum for the I species (Sabrosky et al. 1989). Because its life ; cycle in Arizona may be considerably shorter than the average time nestling pygmy-owls 1 spend in the nest cavity (28 days; Proudfoot and ^ Johnson 2000), it is possible that multiple P. sialia parasitized pygmy-owl nestlings, com- ' pleted their life cycle, and left the cavity as 1 adults before we extracted nest material. Re- ' grettably, we did not search nest material for pupal cases. The effect of hematophagous parasites on ' pygmy-owl productivity and nestling survival is not known and additional study is needed i to assess the potential impact of these para- sites on the endangered pygmy-owls of Ari- I zona. The intent of this paper was to increase j awareness of the parasitic association of l\ I sialia and //. sonorensis and pygmy-owls, and I to raise the possibility of postfleding mortality I attributable to these parasites. ! ACKN()WLi:iXiMi:N I S j We tliank D. .1. Abbale, ti. Dubrovsky, M. t' Ingral- cli, S. .1. I.ant/, S. t! I.owery, W. S. Kicliarclsoii, aiui k. L. Wilcox tor assistance in the (ielcl; T. L. Whitwortli for providing a positive iilentification ol P. sialia'. k. M. Mohr and three anonymous reviewers lor [irovirling comments on an earlier dratt ol this manuscript, tniml- ing was provitled by Arizona Game ami l ish Depart ment, Pima C’ounty Ailministrations Olfice. ami L.S. t ish ami Wikllile Service; logistical support was pro- vided by the Entomology Department at Texas A&M University. LITERATURE CITED Adams, J. O. and M. J. R. Hall. 2003. Methods used for the killing and preservation of blowfly larvae, and their effect on post-mortem larval length. Fo- rensic Science International 138:50-61. Rohm, R. T. 1978. Protocalliphora infestation in Great Horned Owls. Wilson Bulletin 90:291 . Boland, S. R, J. A. Halstead, and B. E. Valentine. 1989. Willow Flycatcher nestling parasitized by larval fly, Protocalliphora cuprina. Wilson Bul- letin 101:127. Brown, C. R. and M. B. Brown. 1986. Ectoparasitism as a cost of coloniality in Cliff Swallows {Hirundo pyrrhonota). Ecology 67:1206-1218. Brown, C. R. and M. B. Brown. 1992. Ectoparasitism as a cause of natal dispersal in Cliff Swallows. Ecology 73:1718-1723. Brown, C. R. and M. B. Brown. 1999. Fitness com- ponents associated with laying date in the Cliff Swallow. Condor 101:230-245. Brown, C. R. and M. B. Brown. 2001. Egg hatch- ability increases with colony size in Cliff Swal- lows. Journal of Field Ornithology 72:1 13-123. Brown, C. R. and M. B. Brown. 2002. Ectoparasites cause increased bilateral asymmetry of naturally selected traits in a colonial bird. Journal of Evo- lutionary Biology 15:1067-1075. Brown, C. R. and M. B. Brown. 2003. Testis size increases with colony size in Cliff Swallows. Be- havioral Ecology 14:569-575. Charmantier, a., L. E. B. Kruuk, and M. Lam- BRECHTS. 2004. Parasitism reduces the potential for evolution in a wild bird population. Evolution 58:203-206. Gold, C. S. and D. L. Dahl.sten. 1983. Effects of parasitic flies {Protocalliphora spp.) on nestlings of Mountain and Chestnut-Backed chickadees. Wilson Bulletin 95:560-572. Hill, H. M. and T. H. Work. 1947. Protocalliphora larvae infesting nestling birds of prey. Condor 49: 74-75. Loyi;, j. and T. W. Riioan. 1991. The cliff swallow bug Occiacus vicarias (llemiptera: Cimicidae) in Horida: ectoparasite implications for hole-nesting birds. Medical Veterinary Entomology 5:5 I 1-513. Ml rino, S. and .1. Porn. 1998. Growth, nutrition ami blow lly parasitism in nestling Pieti I'lycatchers. (’anadian Journal ol Zoology 76:936-941. Mill I I N, G. k. AND I.. A. Dlrdi.n. 2002. Medical and veterinary entomology. Academic I’ress. San Di- ego, ('alirornia. O'Bkiin, 17 L., B. L. Mokkison, and L. S. .Ioiinson. 2001. Assessing the ellect o( hematophagous ec- toparasites on the health ol nestling birds: hae- matocrit vs. haemoglobin le\els in Mouse Wrens parasiti/eil by blow lly larvae. Journal ol Avian Biology 32:73 76. ()KR. r. \Ni) G. \1( (' \i I isii R. 1985. American swal- 188 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 low bug, Oeciacus vicarius Horvath (Hemitera: Cimicidae), in Hirundo rustica and Petrochelidon pyrrhonota nests in west central Colorado. Great Basin Naturalist 47:345-346. Platt, S. W. 1975. The Mexican chicken bug as a source of raptor mortality. Wilson Bulletin 87:557. Proudfoot, G. a. and R. R. Johnson. 2000. Lerru- ginous Pygmy-Owl (Glaucidium brasilianum). The Birds of North America, no. 498. Roby, D. D., K. L. Brink, and K. Wittmann. 1992. Effects of bird blowfly parasitism on Eastern Bluebird and Tree Swallow nestlings. Wilson Bul- letin 104:630-643. Sabrosky, C. W., G. E Bennett, and T. L. Whit- worth. 1989. Bird blow flies (Protocalliphora) in North America (Diptera: Calliphoridae), with notes on the Palearctic species. Smithsonian In- stitution Press, Washington, D.C. UsiNGER, R. L. 1966. Monograph of Cimicidae (He- miptera-Heteroptera). Entomology Society of America, College Park, Maryland. U.S. Fish and Wildliee Service. 1997. Endangered and threatened wildlife and plants; Determination of endangered status for the Cactus Ferruginous Pygmy-Owl in Arizona. Federal Register 62: 10730-10747. U.S. Fish and Wildliee Service. 2003. Cactus Fer- ruginous Pygmy-Owl {Glaucidium brasilianum cactorum) draft Recovery Plan. U.S. Fish and Wildlife Service, Albuquerque, New Mexico. Weidensaul, S. 1989. North American birds of prey. Gallery Books, New York. Wilson Bulletin 1 17(2): 189-193, 2005 EXTREMELY LOW NESTING SUCCESS AND CHARACTERISTICS OF LIFE HISTORY TRAITS IN AN INSULAR POPULATION OF PARUS VARIUS NAMIYEI NORIYUKI YAMAGUCHF 3 AND HIROYOSHI HIGUCHP ABSTRACT. — Differing intensities of predation pressure can affect the evolution of life history traits in island and mainland populations. We found extremely low nesting success in an insular subspecies of the Varied Tit {Pams varius namiyei\ Kozushima Island), and we compared certain life history traits among three subspecies of P. varius experiencing different predation pressures. The nesting success of P. v. namiyei was extremely low as a result of significant nest predation and nest abandonment; 83% of active nests failed due to snake predation. The proportion of depredated nests was significantly greater on Kozushima Island than on Miyakejima Island {P. V. owstoni) or on the mainland {P. v. varius). Of the three subspecies, P. v. namiyei had the longest incubation period, shortest nestling period, an intermediate clutch size, and a small brood size. There were no differences in the date of egg laying among the three populations. The short nestling period for P. v. namiyei may be an adaptive response, as the predation risk during the nestling period on Kozushima was extremely high. Received 3 August 2004, accepted 16 March 2005. \ Nest predation is a major cause of nestling ; mortality in avian species (Ricklefs 1969, I Skutch 1985, Martin 1988, Rotenberry and ' Wiens 1989, Weatherhead and Blouin-Demers I 2004). The intensity of predation pressure can 1 affect the evolution of life history traits (Cody 1971, Clark and Wilson 1981, Slagsvold 1982, Nilsson 1984, Stutchbury and Morton 2001), and high nest predation generally re- sults in selection for individuals that can re- duce their investment in each breeding at- tempt (Slagsvold 1982, Lundberg 1985). This is particularly true of small birds, which are usually unable to protect their nests against predators. Some researchers have investigated I this theory by comparing island and mainland I populations, because predation pressure on is- I lands often differs from that of mainland pop- 1 ulations (Higuchi 1976, Loiselle and Hoppes 1983, George 1987, Sieving 1992). Higuchi I (1976) reported that some life history traits of one insular subspecies of the Varied Tit (/%/- I rii.s variii.s owstoni) differed from tho.se of the I mainland subspecies (F. varius) and that I predation pressure differed between the two populations. I ' Lab. of Animal Hcology, Dept, of Lite .Sciences, Laculty of .Science, Rikkyo Univ., Nishi-ikebiikuro 3- 34-1, Tokyo 171-8501, .lapan. ^ Lab. of Biodiversity .Science, .School of Agricul- ture and Lite Science, Ihiiv. of Tokyo, Yayoi 1-1-1, Tokyo 1 13-8657, .lapan. 'Corresponding author; e-mail: noriyuki@ric.rikkyo.ne.jp We report extremely low nesting success in one insular subspecies {P. v. namiyei) of the Varied Tit and compare certain life history traits with those of two populations studied by Higuchi (1976), each of which is subjected to different predation pressure. We also discuss whether the differences in predation pressure could be responsible for the variation in life history traits among three different subspecies of Varied Tits. METHODS P. varius occurs on the Japanese mainland and islands, the southern Korean Peninsula, and Taiwan. The species is divided into eight subspecies across its range (Ornithological Society of Japan 2000). P. v. varius occurs on the mainland of Japan and the southern Ko- rean Peninsula, P. v. namiyei is found on three northern islands (Niijima, Toshima, and Ko- zushima; Fig. 1) of the Izu Archipelago, and P. V’. owstoni occurs on three southern islands (Miyake, Mikura, and Hachijo). Study site.— The study site was Kozushima Island,' Tokyo, Japan (18.87 knP; 34° 12' N, 139° 08' H; population ~2,100). The island is part of ITiji-Hakone-Izu National Park, but has a residential area that occupies about 10% of the islafid. J'he domifiant vegetation is broad- leaved evergrecfi forest, mostly Castanopsis cuspidate, Machilus thunhergii, and second- growth Alnus sieholdiana. Patches of cedar {Cryptotneria japonica) plantations are inter- spersed throughout the island. The climate is 189 190 THE WILSON BULLETIN • Vol. 1 17, No. 2, June 2005 LIG. 1. Map of the Izu Archipelago and adjacent mainland of Japan, showing locations of the study sites described in both this paper and in a prior study (Higuchi 1976). The gray and hatched areas on Kozushima Island indicate the residential area and the approximate locations where nest boxes were placed, respectively. temperate, with a mean annual rainfall of 2,535 mm and a mean annual temperature of 17.4° C. Mean temperature and rainfall on Mi- yake] ima Island and the adjacent mainland are 16.5° C, 1,832 mm and 17.5° C, 2,907 mm, respectively (Japan Meteorological Agency, www.jma.go.jp/JMA_HP/jma/indexe.html). Field observations. — We erected 137 nest boxes in 2003 and 136 boxes in 2004 (122 X 122 X 180; cavity entrance = 34 mm). Boxes were attached at a height of 2.5 m to 4— 6-m tall broad-leaved evergreen trees and 6-10-m tall planted Japanese cedars throughout the is- land, with the exception of the residential area and extremely steep areas. The distance be- tween boxes was approximately 50 m. We checked each box every 3 days and recorded status, laying date, clutch size, hatching date, number of unhatched eggs, brood size, and fledging date. Our estimates of fledging date thus had a maximum possible error of 3 days; hatching date was adjusted according to de- Yamaguchi and Higuchi • LOW NESTING SUCCESS OE PARUS VARIUS NAMIYEI 191 velopment of nestlings. We categorized pre- dation as follows: if neither the box nor the nesting material had been damaged or dis- { turbed, we concluded that the predator was a 1 snake; if the entrance hole was enlarged and j encircled with peck marks, we concluded that i the predator was a bird (probably the Jungle Crow, Corvus macrorhynchos). Small, mam- malian nest predators, such as martens, wea- sels, and squirrels, do not inhabit the island. Successful nests were defined as those from which at least one young fledged. In total, 99 of 273 boxes were used (at least one egg was laid). We attached a baffle under 48 of the 99 boxes to prevent predation by snakes; the data obtained from these boxes were excluded from calculations of predation frequency (i.e., 51 nests were used in the analyses). Statistical analyses. — We calculated daily nest survival rates using the maximum like- lihood method (Johnson 1979). Daily nest sur- , vival rates for the egg and nestling stages were analyzed separately. The egg period was ! defined as the time between the date the first ! egg was laid until at least one egg hatched; we defined the nestling period as the time be- tween hatching of the first egg and fledging (Cresswell 1997). To compare daily survival rates, we used Z-tests according to the meth- ods outlined by Johnson (1979). Using multiple, two-tailed r-tests, we com- pared predation rates and life history traits of P. V. namiyei on Kozushima Island to those reported for P. v. owstoni and P. varius by Higuchi (1976) on Miyakejima Island and the mainland, respectively. We assumed that var- iables of life history traits followed / distri- i butions, and used two-tailed Welch’s utests ' when comparing life history traits among the I three populations. We did not use ANOVA because we wanted to compare life history - traits only between the Kozushima population I and the other populations, and, moreover, be- I cause the variance values for all lour life his- tory traits greatly differed among populations I (clutch size: X‘ = 12.05, df = 2, P = ().()()2; I brood size: X' = 23.78, df = 2, P < O.OOl; incubation period: X“ = ' 16.61, df — 2, P < O.OOl; ncstlijig period: x’ = 15.82, df = 2, P < 0.001 ). Probability values were atljustcd us- ing sequential Bonferroni methods (Ury 1976, Sokal and Rohlf 1995). fhe familywise error rate was calculated as ot = 1 (1 — 0.05)'-‘^, where k is the number of tests. Adjusted P- values were calculated as P^dj — (0.05/a) X P. To compare the proportion of depredated nests, we used Fisher’s exact test. We ana- lyzed data using the software package R 1.8.1 (http : //cran .r-project.org/). RESULTS P. V. namiyei used 99 of 273 nest boxes (72/ 137 in 2003 and 27/136 in 2004); 51 of the 99 nests were used in the analyses (see Meth- ods). Nest success (7.84%) of P. v. namiyei was extremely low on Kozushima Island due to nest predation and nest abandonment. Four nests were successful, 18 (35.29%) were abandoned, 19 (37.25%) were depredated, 5 (9.8%) failed because of human disturbance, and 1 (2.0%) failed due to deterioration. Four nests (7.84%) failed due to unknown causes (perhaps disease or starvation). Excluding in- active nests (abandoned, disturbed, and un- known), 82.6% (19 of 23) of active nests were depredated, all by snakes. We determined the predator species by direct observation in nine cases; all were Japanese rat snakes (Elaphe climacophora). Predation on a given nest was always complete (100%). Daily survival prob- abilities during the egg and nestling stages were 0.991 ± 0.002 SE and 0.891 ± 0.034 SE, respectively. The daily survival probabil- ity during the nestling stage was significantly lower than that during the egg stage (Z = 2.91, P = 0.002). The probability that a nest would survive through the egg and nestling stages was 0.835 (= 0.991 and 0.148 ( = 0.891'^'’^), respectively (Table 1). We compared the predation pressure on Ko- zushima Island (P. V. namiyei) with that on the mainland (P. v. varius) and on Miyakejima Island (P. V. o\vstoni\ Table 1). The proportion of depredated nests was higher on Kozushima (0.37) than on Miyakejima (O.OO) or on the mainland (0.30; Fisher's exact test: Kozu ver- sus Miyake, P < O.OOl; Ko/u versus main- land, P O.OOl). We also compared several life history traits of /f w namiyei. P. r. varius. and P. V. owstoni ( fable 1 ). P. namiyei ex- hibited the longest incubation pcriotl {namiyei versus varius. P • 0.001 ; namiyei versus mr.v- toni. P O.OOl). the shortest nestling period {namiyei versus varius. P = 0.008; namiyei versus owstoni. P < 0.001), an intermediate clutch si/c {namiyei versus varius. P < O.OOl; 192 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 TABLE 1. Predation pressure (percent depredated nests) and life history traits of P. v. namiyei on Kozushima Island, P. V. varius on the mainland, and P. v. owstoni on Miyakejima Island, Japan. Data for the mainland and Miyakejima are from Higuchi (1976). Standard errors of the brood size for the mainland and Miyakejima are original data by HH. Mean values ± standard errors are shown. Eigures in parentheses are sample sizes. Traits Kozushima Miyakejima Mainland Predation pressure (%) Incubation period (days) Nestling period (days) Clutch size Brood size 37.25 (51) 15.56 ± 0.22 (34) 16.57 ± 0.40 (14) 5.42 ± 0.13 (76) 4.33 ± 0.19 (51) 0.00 (46) 14.06 ± 0.03 (42) 18.76 ± 0.20 (39) 3.92 ± 0.10 (52) 3.78 ± 0.31 (46) 30.28 (109) 13.95 ± 0.09 (87) 18.23 ± 0.27 (71) 6.23 ± 0.08 (101) 6.05 ±0.13 (76) ntimiyei versus owstoni, P < 0.001), and a small brood size (namiyei versus varius, P < 0.001; namiyei versus owstoni, P = 0.14). DISCUSSION The nesting success of P. v. namiyei on Ko- zushima was extremely low as a result of high levels of nest predation and nest abandon- ment; 83% of active nests were depredated. In all cases, the predators were snakes, probably Japanese rat snakes. We frequently found these snakes when checking nest boxes, and although no abundance data are available, we consider them to be abundant on Kozushima. The proportion of abandoned nests was also large (0.35). Significant predation pressure may result in a relatively low threshold of tol- erance before a female P. v. namiyei will abandon her nest. Nest abandonment and re- nesting induced by nest predation are likely subjected to strong selective pressure; thus, any decision rule may be adaptive (Bauchau and Seinen 1997). We believe that our regular nest checks did not induce abandonment. Nest abandonment rates due to human disturbance (12%) in our study were not as high as those reported in other studies of P. variiis (15%; Yamaguchi and Kawano 2001, Yamaguchi et al. 2003). Predation rates differed between Kozushi- ma, Miyakejima, and the mainland, although the sites are relatively similar in terms of veg- etation and climate. The differences in pre- dation rates are probably a function of the dif- ferences in snake abundance. Snakes are ab- sent from Miyakejima Island, and no nest pre- dation was observed by Higuchi (1976). Japanese rat snakes are native to both Ko- zushima Island and the mainland. The three subspecies of P. varius differed in terms of their life history traits. The nest- ling period of P. v. namiyei was the shortest among the three populations. This result sup- ports the notion that high predation levels may exert strong selection pressure on length of nestling period (Skutch 1949, Cody 1966, Lack 1968, Ansersson et al. 1980, Milonoff 1989, but see Barash 1975). This may be an adaptive response, as the predation risk during the nestling stage on Kozushima Island was extremely high. The shorter nestling period in P. V. namiyei may be due, in part, to a rela- tively small brood size (Slagsvold 1984, Bosque and Bosque 1995) or more rapid growth during the nestling phase. Of the three subspecies, P. v’. namiyei had the longest incubation period, and its clutch size was intermediate. These life history traits would seem to be maladaptive under the in- fluence of high predation pressure, as birds can reduce their investment in any one breed- ing attempt by reducing clutch size (Perrins 1977, Ricklefs 1969, Slagsvold 1982, Lund- berg 1985). However, prolonged incubation periods and undiminished clutch sizes may be related to low hatchability in P. namiyei (K. Fujita unpubl. data), which could be attribut- able to low nest attentiveness at crucial peri- ods during the embryo development period. Differences in life history traits among pop- ulations evolve in response to a number of ecological and environmental factors (e.g., longevity, mating system, food abundance, climate, and predation pressure). Of these fac- tors, predation pressure may be one of the most important factors producing the ob- served differences in life history traits in the subspecies of the Varied Tit. ACKNOWLEDGMENTS We thank G. Morimoto for his assistance in the field. We also thank the staff of the Takou Bay camping site Yamaguchi and Higuchi • LOW NESTING SUCCESS OE PARUS VARIUS NAMIYEI 193 and N. Hamakawa for assistance in the field. K. Eujita provided information on the hatchability of P. varius. M. Hasegawa advised us- on the abundance of snakes on the Izu Islands. W. Cresswell and two anonymous referees provided helpful comments on the manuscript. K. Ueda made useful comments on an earlier version of the manuscript. This study was supported by a JSPS Research Fellowship for Young Scientists and the Pro Natura Fund. LITERATURE CITED Ansersson, M., G. Wiklund, and H. Rundgren. 1980. Parental defence of offspring: a model and an example. Animal Behaviour 26:1207-1212. Barash, D. P. 1975. Evolutionary aspects of parental behavior: distraction behavior of the Alpine Ac- centor. Wilson Bulletin 87:367-373. Bauchau, V. AND I. Seinen. 1997. Clutch desertion and re-nesting in Pied Flycatchers: an experiment with progressive clutch removal. Animal Behaviour 54: 153-161. Bosque, C. and M. T. Bosque. 1995. Nest predation as a selective factor in the evolution of develop- ment rates in altricial birds. American Naturalist 145:234-260. Clark, A. B. and D. S. Wilson. 1981. Avian breeding adaptations: hatching asynchrony, brood reduc- tion, and nest failure. Quarterly Review of Biol- ogy 56:253-277. Cody, M. L. 1966. A general theory of clutch size. Evolution 20:174-184. Cody. M. L. 1971. Ecological aspects of reproduction. Pages 462-512 in Avian biology (D. S. Earner and J. R. King, Eds.). Academic Press, New York. Cresswell. W. 1997. Nest predation: the relative ef- fects of nest characteristics, clutch size and paren- tal behaviour. Animal Behaviour 53:93-103. George, T. L. 1987. Greater land bird densities on is- land vs. mainland: relation to nest predation level. Ecology 68:1393-1400. Higuchi. H. 1976. Comparative study on the breeding of mainland and island subspecies of the Varied Tit, Ihirits varius. Tori 25:1 1—20. .loHNSON, D. H. 1979. Estimating nest success: the Mayfield method and an alternative. Auk 96:651- 661. Lack, I). 1968. Ecological adaptations for breeding in birds. Methuen, London, United Kingdom. Loisi;lli., B. A. and W. G. Hoi’RI.s. 1983. Nest pre- dation in insular and mainland lowland rainforest in Panama. C'ondor 85:93 95. Li NDMLRG, .S. 1985. 'fhe importance of egg hatchabil- ity and nest predation in clutch size evolution in altrieial birds. Oikos 45:1 10 117. Marun. T. E. 1988. Habitat and area effects on forest bird assemblages: is nest predation an influence? Ecology 69:74-74. Milonoff, M. 1989. Can nest predation limit clutch size in precocial birds? Oikos 55:424-427. Nilsson, S. G. 1984. The evolution of nest-site selec- tion among hole-nesting birds: the importance of nest predation and competition. Ornis Seandinav- ica 15:167-175. Ornithological Society of Japan. 2000. Check-list of Japanese birds, 6th ed. Ornithological Society of Japan, Obihiro, Japan. Perrins, C. M. 1977. The role of predation in the evo- lution of clutch size. Pages 181-191 in Evolution- ary ecology (B. Stonehous and C. M. Perrins, Eds.). MacMillan, London, United Kingdom. Ricklefs, R. E. 1969. An analysis of nesting mortality in birds. Smithsonian Contributions to Zoology, no. 9. Rotenberry, J. T. and J. A. Wiens. 1989. Reproduc- tive biology of shrubsteppe passerine birds: geo- graphical and temporal variation in clutch size, brood size, and fledging success. Condor 91 : 1-14. Sieving, K. E. 1992. Nest predation and differential insular extinction among selected forest birds of central Panama. Ecology 73:2310-2328. Skutch, a. F. 1949. Do tropical birds rear as many young as they can nourish? Ibis 91:430-455. Skutch, A. F. 1985. Clutch size, nesting success, and predation on nests of Neotropical birds, reviewed. Ornithological Monographs 36:575-594. Slagsvold, T. 1982. Clutch size variation in passerine birds: the nest predation hypothesis. Oecologia 54: 159-169. Slagsvold, T. 1984. Clutch size variation of birds in relation to nest predation: on the cost of repro- duction. Journal of Animal Ecology 53:945-953. SoKAL, R. R. AND E J. Rohlf. 1995. Biometry. Free- man, New York. Stutchbury, B. j. M. and E. S. Morton. 2001. Be- havioral ecology of tropical birds. Academic Press, New York. Ury, H. K. 1976. A comparison of four procedures for multiple comparisons among means (pairwise contrasts) for arbitrary sample sizes, lechnome- trics 18:98-97. Wi:ai hi:rhi;ad, I’. .1. and G. Blouin-Di:me:rs. 2004. Understanding avian nest predation: why orni- thologists should study snakes, .lournal of Asian Bit)logy 35:185-190. Yamaguchi, N. and K. K. Kawano. 2001. Effect of body size on the resource holding [lotential i>f male Varied Jits /\irns varius. .lapanese .lournal of Ornithology 50:(t5 70. YamaCiIK HI, N., K. K. Kaw ano, K. I'gi t hi, \nd I. Yahara. 2003. l acultative sex ratio atljusiment in response to male tarsus length in the Varieil fit Pants varius. Ibis 146:108-113. Short Communications Wilson Bulletin 1 1 7(2); 1 94— 196, 2005 First Record of Bronzed Cowbird Parasitism on the Great-tailed Crackle Brian D. Peer,* -'*'* Stephen I. Rothstein,’ and James W. Rivers* ABSTRACT. — We report the first record of Bronzed Cowbird (Molothnis aeneiis) parasitism on the Great- tailed Crackle (Quiscaliis mexicamis), which repre- sents the 96th known host for this cowbird species. The record is based on a parasitized clutch, collected from Sinaloa, Mexico, in the collection at the Western Foundation of Vertebrate Zoology. The clutch con- tained four grackle eggs and one Bronzed Cowbird egg. This record is unusual because the Great-tailed Grackle is extremely intolerant of foreign eggs, eject- ing them from their nests almost immediately. As the Bronzed Cowbird expands its range and is studied in greater depth, more hosts will undoubtedly be record- ed. Received 22 July 2004, accepted 19 March 2005. The five species of brood parasitic cowbirds {Molothnis spp.) differ greatly in the numbers of hosts they use. Brown-headed (M. ater) and Shiny (M. bonariensis) cowbirds are known to have parasitized more than 200 hosts, while the Giant {M. oryzivorus) and Screaming (M. riifoa.xi Haris) cowbirds parasitize 10 host spe- cies or less (Ortega 1998). The Bronzed Cow- bird (M. cieneiis) uses an intermediate number of hosts, with a total of 95 known host species (Lowther 1995, Sealy et al. 1997, Lowther 2004). Lanyon (1992) and Rothstein et al. (2002) have discussed alternative evolution- ary scenarios for the evolution of host use and the relationship between the number of hosts used by each cowbird species and its branch- ing order in the phylogeny of cowbirds. Ad- ditional data on host use are needed to resolve these issues, especially for the Neotropical cowbird species, in part because the number of recorded hosts is influenced by various bi- ases, such as research effort, range, and even ' Dept, of Ecology, Evolution, and Marine Biology, Univ. of California, Santa Barbara, CA 93106, USA. - Genetics Program, National Museum of Natural History, Smithsonian Institution, 3001 Connecticut Ave., Washington, DC 20008, USA. Current address: Dept, of Biology, Simpson Col- lege, 701 N. C St., Indianola, lA 50125, USA. ■* Corresponding author; e-mail: brian.peer@simpson.edu body size of a particular cowbird species (Rothstein et al. 2002). The Bronzed Cowbird is one of the least studied cowbird species (but see Carter 1986, Peer and Sealy 1999b, Chace 2004) and new data on its host use are especially valuable and could lead to tests of the hypothesis that Bronzed Cowbirds are more specialized in ar- eas where they are sympatric with Brown- headed Cowbirds (Peer and Sealy 1999b). Here, we report the first record of Bronzed Cowbird parasitism on the Great-tailed Grack- le {Quiscaliis mexicamis), representing the 96th recorded host of this cowbird species. The Great-tailed Grackle, like other grackle species, is rarely parasitized by cowbirds (Rothstein 1975, Peer and Bollinger 1997, Peer et al. 2001, Peer and Sealy 2004b), and our record represents the first recorded obser- vation of cowbird parasitism on the Great- tailed Grackle, despite the fact that it is sym- patric with four parasitic cowbird species. There is also no evidence of conspecific brood parasitism in Great-tailed Crackles (Johnson and Peer 2001). On 16 April 2003, we discovered the par- asitized clutch in the collection of the Western Foundation of Vertebrate Zoology in Cama- rillo, California. The clutch, which had been collected on 16 May 1882 by A. Forrer in Presidio, Sinaloa, Mexico, contained four Great-tailed Grackle eggs and one Bronzed Cowbird egg. The clutch was set mark 169,12, and catalog number 167555-1+4. The de- scription stated that incubation was “fresh” and identity “sure.” The number of known hosts for the Bronzed Cowbird has increased 500% since Friedmann’s (1929) seminal study of the cow- birds. Our discovery of the Great-tailed Grackle as a host will likely be followed by additional host records as research is con- ducted in the little-studied southern portion of this cowbird’s range. In addition, the grackle is expanding its range in response to habitat 194 SHORT COMMUNICATIONS 195 modification; thus, the species is encountering new hosts (Sealy et al. 1997). Nonetheless, the Bronzed Cowbird appears to be more restrict- ed with respect to its host species than the Brown-headed Cowbird. Brown-headed Cow- birds parasitize more than two times as many hosts as Bronzed Cowbirds in areas where the species occur in equal numbers (Peer and Sea- ly 1999b). Bronzed Cowbirds were once thought to parasitize mostly orioles {Icterus spp.; Fried- mann 1963), but this view has changed as more hosts have been discovered. Only 10 of the 96 Bronzed Cowbird hosts are Icterus spe- cies, and (including our discovery) only 15% of recorded hosts are members of Icteridae. Host use appears to be influenced by com- munity composition. For example. Peer and Sealy (1999b) found that the most commonly parasitized host in southern Texas was the Northern Cardinal {Cardinalis cardinalis), which was much more abundant there than : orioles. ' This is the first recorded observation of par- I asitism on Great-tailed Crackles — probably i due to the species’ anti-parasite behaviors. I The Great-tailed Crackle is 1 of only 30 spe- ; cies in North America known to regularly ' eject cowbird eggs (Peer and Sealy 2004a) I and they are extremely intolerant of foreign eggs. Not only do they reject 100% of exper- : imental Bronzed and Brown-headed cowbird eggs (typically within hours), they also reject conspecific eggs that closely resemble their own (Peer and Sealy 2()0(), Peer and Sealy 2()04b). Thus, cowbird parasitism may go 1 largely undetected because the cowbird eggs ! are ejected before researchers ever see them. I However, Peer and Sealy (1999b, 2()04b) monitored 798 nests daily, beginning just be- fore sunrise when Bronzed Cowbirds lay their eggs (Peer and Sealy 1999a), and found no I evidence of parasitism, suggesting that cow- birds avoid parasitizing grackles because their ^ eggs would be ejected. j The lack of parasitism is not due to the ;• grackle’s larger size. Similar to Shiny and Gi- ant cowbirds. Bronzed Cowbirds parasitize ■ hosts larger than themselves more ofteti tlum do Brown-headed Cowbirds. Despite havifig only 57% of the mass of Great-tailed Crackle hatchlings, cross-fostered Bronzed Cowbirds can Hedge from Great-tailed Crackle nests, in- dicating that the grackle is a suitable host spe- cies (Peer and Sealy 2004b). This observation supports Peer and Sealy ’s (2004b) hypothesis that Bronzed Cowbird par- asitism may have exerted selection pressure on the egg-ejection behavior demonstrated by Great-tailed Grackles. On the other hand, it may be more likely that this ejection behavior evolved in response to parasitism by the Giant Cowbird, the eggs of which closely resemble grackle eggs, and which also specializes on parasitizing large, colonial members of the Ic- teridae (Peer and Sealy 2004b). ACKNOWLEDGMENTS We would like to thank R. Corado and L. Hall for allowing us to examine the Western Foundation of Vertebrate Zoology collection. This research was sup- ported by NSF grant 0078139. LITERATURE CITED Carter, M. D. 1986. The parasitic behavior of the Bronzed Cowbird in south Texas. Condor 88:1 1- 25. Chace, J. F. 2004. Habitat selection by sympatric brood parasites in southeastern Arizona: the influ- ence of landscape, vegetation, and species rich- ness. Southwestern Naturalist 49:24-32. Friedmann, H. 1929. The cowbirds: a study in the bi- ology of social parasitism. C. C. Thomas, Spring- field, Illinois. Friedmann, H. 1963. Host relations of the parasitic cowbirds. U.S National Museum Bulletin, no. 233. Washington, D.C. Johnson, K. and B. D. Peer. 2001. Great-tailed Grack- le {Qiiisccilus mexicanus). The Birds of North America, no. 576. Lanyon, S. M. 1992. Interspecific brood parasitism in blackbirds (Icterinae): a phylogenetic perspective. Science 255:77-79. Lowther, P. E. 1995. Bronzed Cowbird (Molothrus aencHs). The Birds of Ntirth America, no. 144. Lowther, P. H. 2004. Lists of victims and hosts of the parasitic cowbirds (Molothrus). http://fml. fieldmuseum.org/aa/Files/lov\ther/CB List. pdf (ac- cessed 4 February 2005). ()Kn;oA. C’. P. 1998. Cowbirds and other brot>d para- sites. University of Arizona Press, Tucson. Pi i K. B. I). and Li. K. Boi 1 iNCii R. 1997. lixplanations tor the infrec|uent cowbird parasitism on C'ommon Grackles. C'ondor 99:151-161. Pi i K, B. [).. 11. .1. Homan, and S. G. Seai v. 2001. Inlretiuent cowbird parasitism on C’ommon Grack- les revisitetl: new records from the Northern Great Plains. Wilson Bulletin 113:90-93. Pi F K. B. I). and .S. G. .Si am . 1999a. Laying time of the Bronzed C'owbird. Wilson Bulletin 111:137 139. 196 THE WILSON BULLETIN • Vol. 1 17, No. 2, June 2005 Peer, B. D. and S. G. Sealy. 1999b. Parasitism and egg puncture behavior by Bronzed and Brown- headed cowbirds in sympatry. Studies in Avian Biology 18:235-240. Peer, B. D. and S. G. Sealy. 2000. Conspecific brood parasitism and egg rejection in Great-tailed Grack- les. Journal of Avian Biology 31:271-277. Peer, B. D. and S. G. Sealy. 2004a. Correlates of egg rejection in hosts of the Brown-headed Cowbird. Condor 106:580-599. Peer, B. D. and S. G. Sealy. 2004b. Pate of grackle {Quiscalus spp.) defenses in the absence of brood parasitism: implications for long-term parasite- host coevolution. Auk 121:1172-1186. Rothstein, S. I. 1975. An experimental and teleonom- ic investigation of avian brood parasitism. Condor 77:250-271. Rothstein, S. I., M. A. Patten, and R. C. Pleischer. 2002. Phylogeny, specialization, and brood-para- site coevolution: some possible pitfalls of parsi- mony. Behavioral Ecology 13:1-10. Sealy, S. G., J. E. Sanchez, R. G. Campos, and M. Marin. 1997. Bronzed Cowbird hosts: new re- cords, trends in host use, and cost of parasitism. Ornitologia Neotropical 8:175-184. Wilson Bulletin 1 17(2):196-198, 2005 A Cause of Mortality for Aerial Insect! vores? Muir D. Eaton'’2 and Daniel L. Hernandez*^ ABSTRACT. — A male Eastern Phoebe (Sayornis phoebe) was found dead on 15 April 2004, hanging from a piece of monofilament fishing line over the Kinnikinic River near River Falls, Wisconsin (Pierce County). The individual was hooked through the tongue by a fly-fishing lure. Although fishing tackle has been reported as a cause of mortality for several aquatic bird species, further research is needed to de- termine whether abandoned trout-fishing lures repre- sent a significant threat to aerial insectivores. Received 13 September 2004, accepted 28 February 2005. The Eastern Phoebe {Sayornis phoebe) is a suboscine flycateher (Tyrannidae) that breeds throughout the eastern United States and southern Canada. It is one of the earliest mi- grants to return in the spring (Weeks 1994). Eastern Phoebes are primarily aerial insecti- vores, but they also glean insects from a va- riety of substrates (Via 1979). They feed pri- marily in edge habitats (Weeks 1994), includ- ing along stream banks where they fly out over the water to capture prey. Flying insects compose the majority of the Eastern Phoebe’s diet (Weeks 1994). During hatches of insects ' Dept, of Ecology, Evolution, and Behavior, Univ. of Minnesota, 100 Ecology Bldg., 1987 Upper Buford Cr., St. Paul, MN 55108, USA. 2 Current address: Museum of Natural History, Univ. of Kansas, Dyche Hall, 1345 Jayhawk Blvd., Lawrence, KS 66045-7561, USA. ^ Corresponding author; e-mail: hernOl 1 1 @umn.edu from streams, individuals often forage low over the water by hawking (MDE pers. obs.). Eastern Phoebes also have been observed catching fish, sometimes hovering over the water for several seconds before taking the prey (Binford 1957). On 15 April 2004, a male Eastern Phoebe (sex was subsequently determined by inspec- tion of gonads) was found dead, hanging ap- proximately 0.5 m below a tree branch that was 2 m above a small river (Fig. 1). We found the bird —0.8 km downstream from the River Falls dam on the Kinnikinic River near River Falls, Wisconsin (Pierce County). Clos- er inspection revealed that the Eastern Phoebe was hanging from the end of a piece of mono- filament fishing line. We recovered the bird on 16 April and deposited it at the Bell Museum of Natural History at the University of Min- nesota (catalogue #MDE-065). The phoebe was hooked through the tongue by a fishing lure used for fly-fishing. Presum- ably the line was broken off once it and the lure became entangled in the tree. The lure was a bead-head pheasant-tail nymph, which generically mimics the larval stage of mayfly species (Ephemeroptera). These larvae are aquatic, thus, this lure does not mimic the nor- mal aerial insects that typically compose the Eastern Phoebe’s diet. We hypothesize that the lure was bouncing around at the end of the SHORT COMMUNICATIONS 197 FIG 1. Eastern Phoebe (Sayornis phoehe), attached to monofilament fishing line and lure, hanging from a tree branch over the Kinnikinic River, River Falls, Wisconsin, 15 April 2004. line on a windy day and appeared to the phoe- be as a Hying insect. The bird then caught the lure in its bill, and the hook pierced the j tongue. An alternative hypothesis is that this ! individual was trying to collect the Fishing line to use as nesting material, but happened to ! grab onto the lure and got hooked, liastern Phoebes have been previously reported tan- gled in fishing line and twine that were being ’ ii.sed as nesting material (Clapp 1993, F'riesen ' 2002). Use of man-made materials in passer- ine nests is a widespread phenomenon, as many species will use whatever materials are readily available (Baicich and Harrison 1997). Paper, string, and plastics are commonly re- ported as nesting materials used by species living in, or near, urban areas (e.g., Lowther and Cink 1992, Cabe 1993, Rising and Flood 1998). This is the first time that this source of avi- an mortality has been reported. We could find no estimates in the literature of the number of fly-fishing lures per km of stream; thus, we have no way to estimate the rate of mortality by these lures on birds, but typical trout-fish- ing outings often result in the loss of several lures due to entanglement with streamside trees and shrubs (MI)I: and DLH pers. obs.). Additional research is needed to determine whether F^astern Phoebes and other aerial in- secti\()res commonly mistake Hy-fishifig lures for food, and how fret|uently such lures are found along trout streams. Research on acpiatic birds has shown that 198 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 fishing tackle (i.e., fishing hooks, lures, line, and lead weights) can be a significant source of mortality in some species. In particular, the consumption of lead weights and lead portions of fishing tackle accounted for 10-50% of adult mortality in two different studies of Common Loons {Gavia immer; Scheuhammer and Norris 1996, Sidor et al. 2003), and in- gestion of lead weights was the single largest cause of death in several populations of Mute Swans (Cygnus olor) in Great Britain (Kirby et al. 1994). In addition, high rates of inges- tion of non-lead portions of fishing tackle have been reported in Brown Pelicans {Pele- canus occidentalis', Franson et al. 2003). Fran- son et al. (2003) concluded that portions of fishing tackle exclusive of lead weights con- tributed to mortality, not only in Brown Peli- cans, but also in Common Loons, Black- crowned Night-Herons {Nycticorax nycticor- a.x). Bald Eagles {Haliaeetus leucocephalus), and Double-crested Cormorants (Phalacro- corax auritus). Apart from the species men- tioned above, documented cases of non-lead fishing tackle as a source of avian mortality are extremely few. ACKNOWLEDGMENTS We thank R. M. Zink and two anonymous referees for helpful comments on this manuscript. LITERATURE CITED Baicich, R J. and C. J. O. Harrison. 1997. A guide to the nest, eggs, and nestlings of North American Birds, 2nd ed. Academic Press, San Diego, Cali- fornia. Binford, L. C. 1957. Eastern Phoebes fishing. Auk 74; 264-265. Cabe, P. R. 1993. European Starling (Sturnus vulgar- is). The Birds of North America, no. 48. Clapp, R. B. 1993. Nestling Eastern Phoebes entan- gled in fishing line. Raven 64:21-22. Eranson, j. C., S. P. Hansen, T. E. Creekmore, C. J. Brand, D. C. Evers, A. E. Duerr, and S. De- Stefano. 2003. Lead fishing weights and other fishing tackle in selected waterbirds. Waterbirds 26:345-352. Friesen, V. C. 2002. Eastern Phoebe hanging by a thread. Blue Jay 60:224. Kirby, J., S. Delany, and J. Quinn. 1994. Mute swans in Great Britain: a review, current status and long- term trends. Hydrobiologia 279/280:467-482. Lowther, P. E. and C. L. Cink. 1992. House Sparrow {Passer domesticus). The Birds of North America, no. 12. Rising, J. D. and N. J. Flood. 1998. Baltimore Oriole {Icterus galbula). The Birds of North America, no. 384. Scheuhammer, A. M. and S. L. Norris. 1996. The ecotoxicology of lead shot and lead fishing weights. Ecotoxicology 5:279-295. Sidor, I. E, M. A. Pokras, A. R. Major, R. H. Pop- PENGA, K. M. Taylor, and R. M. Miconi. 2003. Mortality of Common Loons in New England, 1987 to 2000. Journal of Wildlife Diseases 39; 306-315. Via, j. W. 1979. Foraging tactics of flycatchers in southwestern Virginia. Pages 191-202 in The role of insectivorous birds in forest ecosystems (J. G. Dickson, R. N. Conner, R. R. Fleet, J. C. Kroll, and J. A. Jackson, Eds.). Academic Press, New York. Weeks, H. R, Jr. 1994. Eastern Phoebe {Sayornis phoebe). The Birds of North America, no. 94. SHORT COMMUNICATIONS 199 Wilson Bulletin 1 17(2); 199-200, 2005 First Record of Swainson’s Warbler Parasitism by Protocalliphora Blow Fly Larvae Mia R. Revels and Terry L. Whitworth^ ABSTRACT. — We report the first record of blow flies {Protocalliphora) parasitizing Swainson’s War- blers {Limnothlypis swainsonii). Eight of 12 (67%) nests collected in southeastern Oklahoma during four breeding seasons (2001-2004) were parasitized by P. deceptor larvae. Because Swainson’s Warbler is con- sidered a species of high conservation priority in the southeastern United States, and because Protocallipho- ra can have negative impacts on their hosts, factors influencing blow fly parasitism of this species warrant further investigation. Received 27 February 2004, ac- cepted 16 March 2005. Swainson’s Warbler {Limnothlypis swain- sonii) is one of North America’s most secre- tive avian species, and little is known about many aspects of its biology, including para- sites and disease (Brown and Dickson 1994). Here, we present the first information regard- ing parasitism by Protocalliphora blow flies in this species. Larvae of Protocalliphora (Diptera: Calliphoridae) are obligate hema- tophagous parasites that reside in the nests of birds with nidicolous young. To feed, larvae of most species attach intermittently to the nestlings. Effects of this parasite on their avi- an hosts range from little or none (e.g.. Miller and Fair 1997) to reduced hematocrit and he- moglobin levels (Whitworth and Bennett 1992), slowed growth and development (e.g., Johnson et al. 1991, Hurtrez-Bousses et al. 1997), reduced activity (Bergtold 1927), re- duced adult survival (Wesolowski 2001), and death (Halstead 198S). Swainson’s Warblers are monomorphic. Neotropical migrants that breed in bottomland hardwood forests in the southeastern United States. During our study, nests were located in dark, densely vegetated areas near water in greenbriar {Smila.x spp.), giant cane (Arnndi- ' Biology Dept., Northeastern .State Univ.. 611 N. Clranci, Tahlequah. OK 74464, USA. ’25.^.^ Inter Ave.. Puyallup, \V’A 9S.^72. U.SA. 'Corresponding author; e-mail; revels(«disuok.etlu naria gigantea), Japanese honeysuckle (Lon- icera japonica), and other substrates. Swain- son’s Warblers are single brooded and lay a clutch of 2-5 eggs (mean = 3.3); only the female broods and clutches hatch in 13-15 days (Brown and Dickson 1994). The average nestling period for Swainson’s Warblers in our study was 10 days. We conducted our study at Little River National Wildlife Refuge (LRNWR) in McCurtain County, Oklahoma (33° 56' N, 94° 42' W). LRNWR is located in the flood- plain of the Little River (elevation 102 m) and is composed primarily of bottomland hard- wood forest interspersed with sloughs and drainages. We located Swainson’s Warblers nests by systematically searching appropriate habitat (Meanley 1971) in and near identified male territories. Nests were monitored from 30 April to 24 July 2001-2004, following pro- tocols outlined in Martin and Geupel (1993). At the end of each breeding season, we col- lected nests and examined them for Protocal- liphora pupae and adults, which were then identified to the species level. Only nests that had contained nestlings at least 6 days old were examined; Protocalliphora larvae do not pupate until they reach the third instar and pu- pae will not form when nestlings are younger than 6 days. Of nests (/? = 12) that contained nestlings >6 days old, 33% (1/3) were para- sitized in 2001, 50% (1/2) in 2002, 80% (4/5) in 2003, and 100% (2/2) in 2004. Hatch date, number of nestlings and pupae, and nest fate are shown in fable 1. Two additional nests located in 2002 and 2003 after the nesting at- tempts had been completed also were parasit- ized, but arc not included because age and fate of nestlings was not known, fhe first was lo- cated 4 June 2002 and contained 10 pupae, and the other was located 23 June 2003 and contained 3 pupae. All 14 nests were parasit- izetl by P. dcccptor, a generalist species that infests the nests of many species in the eastern United States. 200 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 TABLE I . The number of parasitic Protocalliphora larvae found in Swainson’s Warblers nests does not ap- pear to be related to number of nestlings or presence of Brown-headed Cowbird nestlings. A greater proportion of unparasitized nests with known fates (3/3) were suc- cessful (fledged young) than parasitized nests (6/8). Nests in which young hatched later in the breeding sea- son (after 28 May, n = 6) had a greater prevalence of parasitism (83%) than those hatching earlier (50%, n = 6). Only nests that contained nestlings ^6 days old were considered {Protocalliphora pupae do not form when nestlings are younger than 6 days). Nests were collected at the Little River National Wildlife Refuge, McCurtain County, Oklahoma, 2001-2004. Hatch date No. nestlings Nestling age (days)^^ No. pupae Nest fate 17 May 2001 1 10 — Fledged 18 May 2001 4 9 — Fledged 17 May 2001 3^’ 6-8 15 Depredated 14 May 2002 L >8 — Unknown 22 June 2002 1 10 9 Fledged 26 May 2003 2 10 4 Fledged 29 May 2003 3 10 27 Fledged 5 June 2003 3 9-10 — Fledged 2 July 2003 2 9-10 1 Fledged 17 July 2003 3 8-10 9 Fledged 16 May 2004 4 7 17 Depredated 2 June 2004 3 9 38 Fledged ^ Age of nestlings when nest either failed or nestlings fledged. Nest contained one Brown-headed Cowbird nestling. Swainson’s Warbler is ranked high on lists of avian species of special concern (Louisiana Nature Conservancy 1992, Hunter et al. 1993, Smith et al. 1993, Thompson et al. 1993). In- formation about factors influencing reproduc- tive success of Swainson’s Warblers, such as Protocalliphora parasitism, is important for de- veloping appropriate conservation strategies. ACKNOWLEDGMENTS We thank M. L. Adams and R. A. Perry for field assistance, and J. E Gray, B. R. Elack, and B. A. Erench for laboratory assistance. B. A. Heck, the George Miksch Sutton Avian Research Center, and Little River National Wildlife Refuge provided logis- tical support. The U.S. Fish and Wildlife Service and Northeastern State University provided funding for this project. The authors thank L. S. Johnson and two anonymous reviewers for comments on drafts of this manuscript. LITERATURE CITED Bergtold, W. H. 1927. A House Finch infested by fly larvae. Auk 44:106-107. Brown, R. E. and J. G. Dickson. 1994. Swainson’s Warbler (Limnothlypis swainsonii). The Birds of North America, no. 126. Halstead, J. A. 1988. American Dipper nestlings par- asitized by blowfly larvae and the northern fowl mite. Wilson Bulletin 100:507-508. Hunter. W. C., D. N. Pashley, and R. E. F. Escano. 1993. Neotropical migrant landbird species and their habitats of special concern within the south- east region. Pages 159-171 in Status and man- agement of Neotropical migratory birds (D. M. Finch and P. W. Stangel, Eds.). General Technical Report RM-229, USDA Forest Service, Fort Col- lins, Colorado. Hurtrez-Bousses, S., P. Perret, F. Renaud, and J. Blondel. 1997. High blowfly parasitic loads af- fect breeding success in a Mediterranean popula- tion of Blue Tits. Oecologia 112:514-517. Johnson, L. S., M. D. Eastman, and L. H. Kermott. 1991. Effect of ectoparasitism by larvae of the blow fly Protocalliphora parorum (Diptera: Cal- liphoridae) on nestling House Wrens, Troglodytes aedon. Canadian Journal of Zoology 69:1441- 1446. Louisiana Nature Conservancy. 1992. Partners in Flight West Gulf Coastal Plain and Mississippi River Alluvial Plain physiographic areas meeting newsletter, 16 March 1992. Vicksburg, Mississip- pi, newsletter. Baton Rouge, Louisiana. Martin, T. E. and G. R. Geupel. 1993. Nest-monitor- ing plots: methods for locating nests and moni- toring success. Journal of Field Ornithology 64: 507-519. Meanley, B. 1971. Natural history of the Swainson’s Warbler. North American Fauna, no. 69. Miller, C. K. and J. M. Fair. 1997. Effects of blow fly {Protocalliphora spatulata: Diptera: Calliphor- idae) parasitism on the growth of nestling Savan- nah Sparrows in Alaska. Canadian Journal of Zo- ology 75:641-644. Smith, C. R., D. M. Pence, and R. J. O’Connor. 1993. Status of Neotropical migratory birds in the Northeast: a preliminary assessment. Pages 172- 188 in Status and management of Neotropical mi- gratory birds (D. M. Finch and P. W. Stangel, Eds.). General Technical Report RM-229, USDA Forest Service, Fort Collins, Colorado. Thompson, F. R., Ill, S. J. Lewis, J. Green, and D. Ewert. 1993. Status of Neotropical migrant land- birds in the Midwest: identifying species of man- agement concern. Pages 145—158 in Status and management of Neotropical migratory birds (D. M. Finch and P. W. Stangel, Eds.). General Tech- nical Report RM-229, USDA Forest Service, Fort Collins, Colorado. Wesolowski, T. 2001. Host-parasite interactions in natural holes: Marsh Tits {Pams palustris) and blow flies {Protocalliphora falcozi). Journal of Zoology (London) 255:495-503. Whitworth, T. L. and G. F. Bennett. 1992. Patho- genicity of larval Protocalliphora (Diptera: Cal- liphoridae) parasitizing nestling birds. Canadian Journal of Zoology 70:2184-2191. SHORT COMMUNICATIONS 201 j Wilson Bulletin 1 1 7(2):201— 204, 2005 i, First Record of Eurasian Jackdaw {Corvus monedula) Parasitism by the I Great Spotted Cuckoo (Clamator glandarius) in Israel ^ Motti Charter,'’^ Amos Bouskila,^ Shaul Aviel,^ and Yossi Leshem* ABSTRACT — Little is known about the biology of j the Great Spotted Cuckoo {Clamator glandarius) in 1 Israel. After erecting nest boxes intended for cavity- , nesting raptors, however, we had opportunities to ob- I serve Great Spotted Cuckoos parasitizing Eurasian I Jackdaws (Corvus monedula) that also nested in some ; of the boxes. During the 2003 breeding season, we j monitored seven jackdaw nests, six of which were par- I asitized by cuckoos. In five of the jackdaw nests, one I to four cuckoo eggs hatched, and one to three nestlings survived to fledge (four nests). This is the first docu- mentation of Great Spotted Cuckoos parasitizing jack- I daws in Israel. Received 4 June 2004, accepted 18 'I February 2005. ,.| i The Great Spotted Cuckoo {Clamator glan- clariiis) is an obligate brood parasite. In Eu- 1 rope, the cuckoo’s main host is the Common I Magpie {Pica pica), and the Carrion Crow I (Corx’Lis corone) serves as a secondary host (Cramp 1985a). Cuckoos will parasitize other : corvids, both in Europe (Cramp 1985a, Soler 1 1990) and in Africa (Jensen and Jensen 1969, Cramp 1985a), but their breeding success is generally greater when parasitizing magpies (Soler 1990). Parasitism of Eurasian Jackdaws {Corvus monedula) by Great Spotted Cuckoos I has been observed in Spain, but at low fre- : quencies (Soler 1990, 2002). In Israel, the Great vSpotted Cuckoo is a summer resident, arriving from mid-Decem- I her to late March, and then leaving in June I after the nesting season (Shirihai 1996). In Is- I racl. Great Spotted Cuckoos mainly parasitize I Carrion Crows (Yom-Jdv 1975); to a lesser ! extent (isolated observations) they also para- ' Dept, of /oology, fcl Aviv Uiiiv., fel Aviv, 6997K. Israel. Dept, of Life Seienees, Men-Gurion Univ. of (he Negev. Beer-Sheva, H4I05, Israel. ' Kibbutz .Sde Lliyahu, Ml* Beit Shean Valley, I OH 10. Israel. ‘ C’orrespoiuling author; e-mail; eharterm(fi^ post. tail. ae.il sitize Eurasian Jays (Garrulus glandarius', Shirihai 1996), Fan-tailed Ravens {Corvus rhipidurus', Shirihai 1996), and House Crows {Corvus splendens; Yosef 1997, 2002). Here, we report six instances of Great Spotted Cuck- oos parasitizing jackdaw nests. We monitored hatching and fledging success of cuckoos in jackdaw nests to better understand the suit- ability of this species as a host for Great Spot- ted Cuckoos. METHODS The study site — an organic crop field and a date plantation (combined size = 32 ha) at Kibbutz Sde Eliyahu, Israel (32° 30' N, 35° 30' E) — was situated in the Jordan Rift Valley, 7 km from the city of Beit Shean and about 200 m below sea level. During the 2003 nest- ing season, we monitored five jackdaw pairs that nested in small nest boxes (50 cm wide X 30 cm long X 30 cm high; entrance 22 cm high X 15 cm wide) and two pairs that nested in large nest boxes (50 X 75 X 50 cm; en- trance 25 X 15 cm). The small nest boxes, intended for Eurasian Kestrels {Falco tinnun- culus), were erected in 1998 and attached to date palms {Phoenix dactyl ifera) at a height of 6 m above the ground; the large nest boxes, intended for Barn Owls {Tyto alha), were erected in 1993 in crop fields at a height of 3 m above the ground. Beginning the first week in March 2003, all nests were checked weekly using a hydraulic lift supplied by Kibbutz Sde Eliyahu. Because the jackdaw' clutches were unusually large (mean clutch size in Israel is 4-5 eggs; Paz 1987), we suspected that inter- or intraspecilic parasitism had taken place; but due to the similarity between jackdaw atul cuckoo eggs, we were unable to identify par- asites until 10 days after hatching (when feathers started showing). Although shape and color of the tw'o species* eggs differ some- what, we were unaware of those differences until we had conlirmed that some of the nest- 202 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 TABLE 1. Hatching and fledging success of six Eurasian Jackdaw nests parasitized by Great Spotted Cuck- oos in Kibbutz Sde Eliyahu, Israel, during the 2003 breeding season. Number of eggs Number of nestlings^* Number of young fledged Box no. Cuckoo Jackdaw Both Cuckoo Jackdaw Both Cuckoo Jackdaw Both 1 2 5 7 1 2 3 1 0 1 2 — — 5 1 1 2 1 0 1 4b — — 9 4 4 8 — — — 5" — — 9 2 3 5 2 — 2 8 37^ n — — 9 4 0 4 3 0 3 39 12 10 22 7 0 7 Mean — — 7.8 2.4 2.0 4.4 1.8 0 1.8 SD — — 1.8 1.5 1.6 2.3 1.0 0 1.0 ^ Brood size is a minimum estimate due to eggs/nestlings disappearing from some nests before identification. ^ Nest box was accidentally knocked down by date plantation workers on 22 April. Four live cuckoos, three starved dead jackdaws, and one starving jackdaw were in the box. All were approximately 5 days old. One healthy and one starving jackdaw nestling were removed for another study. ‘^Clutch and brood size unknown: one cuckoo and one jackdaw egg were found in this abandoned jackdaw nest (discovered on 9 May). Fate of nest unknown. lings were cuckoos; thus, the exact number of parasite and host eggs was unknown except in box number 1. In addition, the exact time and order of parasitism (before, after, or during jackdaw laying) was unknown. We identihed starving nestlings as those that were substan- tially smaller and weaker (i.e., could not hold head up) than other nestlings, and starving or starved (dead) nestlings as those that had empty crops. Because corvids are known to remove dead nestlings from nests (Yom-Tov 1975), and because our nest checks took place only weekly, the fate (starved, diseased, de- predated, etc.) of nestlings that disappeared between visits was unknown. RESULTS Jackdaws started building their nests during the first 2 weeks in March, and began egg laying about 4 weeks later; both species com- pleted egg laying between 3 and 21 April. Cuckoo eggs were sub-elliptical with blunt ends, light bluish-green, and heavily marked with light brown spots. The eggs were similar in color and shape to the middle Great Spotted Cuckoo egg depicted in Cramp (1985a:plate 95). Jackdaw eggs were more elliptical, blu- ish-green, and lightly to thickly marked with dark brown spots; they were similar in color to both the left and middle jackdaw eggs de- picted in Cramp (1985b:plate 76), but their shape more closely matched that of the left egg. Cuckoos parasitized six of seven jackdaw nests (85.7%); a mean of 1.8 cuckoos fledged per parasitized nest (n = 4; Table 1). The one unparasitized jackdaw nest had a clutch of five eggs, all of which hatched, and three of which fledged. Eggs were found missing between nest checks in nest boxes 2 and 8. In box 8, there had been nine eggs, but there were just four cuckoo nestlings on the next nest check (8 days later). In box 2, three jackdaw eggs were missing after a cuckoo and a jackdaw had hatched. We were unable to determine the fate of the missing eggs or nestlings. DISCUSSION The parasitism rate and reproductive suc- cess of cuckoos we report suggests that jack- daws are suitable hosts for Great Spotted Cuckoos. Moreover, the impact of parasitism on reproductive success of jackdaws appears to be severe. The nesting success of parasit- ized jackdaw pairs (no jackdaws fledged at four nests) was less than that of the unpara- sitized pair (three jackdaws fledged). How- ever, in Spain only 6 of 290 jackdaw nests were parasitized (2.1%; Soler 1990) and only 1 of 9 parasitized nests fledged cuckoos (11.1%; Soler 2002). Habitat characteristics may be responsible for differences in the jackdaw-cuckoo rela- tionship in Israel versus Spain. The high rate of parasitism we observed could have been due to a lack of alternative hosts or a cuckoo SHORT COMMUNICATIONS 203 ; preference for jackdaw hosts. Carrion Crows I nest on the kibbutz about 1 km away from our : study site (they do not nest in the date plan- I tation or crop fields themselves) and have ! been parasitized for the past 10 years (SA I pers. obs.), but they start nesting earlier than i jackdaws (late February to early March; Paz 1987). In addition, many pairs of Eurasian Jays (>20 pairs) nested in the date plantation, but we have never recorded cuckoos parasit- izing the jays. In Israel, jackdaw populations declined drastically in the 1950s due to poisoning; in 1987 they were still considered rare, nesting in just a few isolated colonies (Paz 1987). In the early 1990s, jackdaw populations started to increase, and in 1999 they began nesting in our study area (SA pers. obs.). Recent sym- patry may explain the cuckoo’s success in Is- rael, as magpies living in recent sympatry I with Great Spotted Cuckoos reject fewer eggs ; than those living in ancient sympatry (Soler I 1990, Soler and Mpller 1990, Soler et al. ! 1999). There were differences in nest sites and nest type used by jackdaws in Spain versus those in Israel. In Spain, jackdaws nested in colo- nies (2-10 individuals; Soler and Soler 1996) on clay cliffs in which there were many crev- ices and holes. In Israel, jackdaws nested in nest boxes located on date palms {n = 5) and in crop fields {n = 2). Soler and Soler (1996) II found that nests with larger entrances are dep- redated more frequently (by Common Ravens, CorvLis corax) and that Great Spotted Cuck- I oos prefer hosts that nest in trees (Soler 1990). In Israel, the large entrances of our nest boxes I and the location of jackdaw nest boxes in trees may have made it diflicult for the jackdaws to I defend their nests. Great Spotted Cuckoo nestlings are known Ii to OLitcompete host young for food, causing I the latter to starve to death (Cramp 1985a, So- I ler 1990, Soler and Soler 1991). In Israel, at four of five nests with data on brood size, 1 jackdaw nestlings were found both starved ' and starving due to such competition. None of the cuckoo young starved. However, our find- ings contrast with those of Soler (2002), who found that, for the most part. Great Spotted Cuckoo nestlings, and not jackdaws, are the ones that starved in jackdaw nests. Brood parasites may prefer certain hosts over others. One would expect hosts that suc- cessfully raise parasitic young to be preferred over hosts that do not. In our study area, both the high rate of cuckoo parasitism of jackdaws and the cuckoo’s high level of breeding suc- cess indicate that, under certain environmental conditions, jackdaws can be successful foster parents for Great Spotted Cuckoos. ACKNOWLEDGMENTS We are especially grateful to Kibbutz Sde Eliyahu (particularly S. Charter) for lodging and assistance dur- ing all stages of the research. We are grateful to M. Soler, Y. Yom-Tov, A. Lotem, and three anonymous referees for comments on the manuscript. We thank N. Paz for editing the text. Gabriel Sherover Foundation, Israel, provided financial support for the research and an M.Sc. grant was awarded to MC by Tel Aviv Uni- versity, Israel. LITERATURE CITED Cramp, S. 1985a. The birds of the western Palearctic, vol. IV. Oxford University Press, Oxford, New York. Cramp, S. 1985b. The birds of the western Palearctic, vol. VIII. Oxford University Press, Oxford, New York. Jensen, R. A. and M. K. Jensen. 1969. On the breed- ing biology of southern African Cuckoos. Ostrich 40:163-181. Paz, U. 1987. The birds of Israel. Stephen Greene Press, Lexington, Massachusetts. Shirihai, H. 1996. The birds of Israel. Academic Press, London, United Kingdom. Soler, M. 1990. Relationships between the Great Spotted Cuckoo Clamator glandarius and its corvid hosts in a recently colonized area. Ornis Scandinavica 21:212-223. Soler, M. 2002. Breeding strategy and begging inten- sity: influences on food delivery by parents and host selection by parasitic cuckoos. Pages 413- 428 in The evolution of begging: competition, co- operation, and communication (J. Wright and M. L. Leonard, Eds.). Kluwer Academic Publishers, Dordrecht, The Netherlands. Soler, J. J., A. P. MARiiNt:/, M. Soler, and A. P. Moli.i-r. 1999. Genetic and get^graphic variation in rejection behavior of luiropean Magpie popu- lations: an experimental test of rejecter-gene How. Pivolution 53:947 956. S()i.t;R, M. and a. P. Moi I I r. 1990. Duration and co- evolution between the Cireat Spotted C’uckoo and its magpie host. Nature 343:748 750. Soi.i.R, M. and j. j. Soi i.r. 1991. Growth and devel- opment of Great Spotteil ('uckoos and their mag- pie host, ('oiulor 93:49 54. Soi I R. M. and .1. J. Soi t r. 199b. Idfects of experi- mental foot! provisioning on reproduction in the 204 THE WILSON BULLETIN • Vol. 117, No. 2, June 2005 Jackdaw Corvus monedula, a semi-colonial spe- cies. Ibis 138:377-383. Yom-Tov, Y. 1975. Recognition of eggs and young by the Hooded Crow {Corvus corone). Behavior 59: 247-25 1 . Yosef, R. 1997. First record of Great Spotted Cuckoo (Clamator glandarius) parasitizing Indian House Crow {Corvus splendens). Israel Journal of Zool- ogy 43:397-399. Yosef, R. 2002. Second breeding record of Great Spot- ted Cuckoo Clamator glandarius in Eilat. Sand- grouse 24:142-144. Wilson Bulletin 1 1 7(2):204-205, 2005 House Wren Preys on Introduced Gecko in Costa Rica Marco D. Barquero'’^ and Branko Hilje' ABSTRACT— On 25 May 2002, we observed a House Wren {Troglodytes aedon) eating a juvenile house gecko {Hemidactylus frenatus) in Golfito, Costa Rica. Just a few studies report insect-eating birds tak- ing vertebrate prey, and we found no prior publications for this species. The recently introduced house gecko may be a new potential food resource for other native species in Costa Rica and elsewhere. Received 16 Au- gust 2004, accepted 17 March 2005. Members of the Troglodytidae are known for their almost completely insectivorous hab- its. Twenty-two species of this family have been reported for Costa Rica (Barrantes et al. 2002) and they are described as incessant searchers of insects, larvae, spiders, and other invertebrates. They seek their food in forests, thickets, open groves, grasslands, and marsh- es. In Costa Rica, the House Wren {Troglo- dytes aedon) is commonly found around hu- man habitations and in man-made habitats. It is a conspicuous resident species occurring from lowlands to 2,750 m, and is rarely found in extensively forested areas or dry lowlands (Stiles and Skutch 1989). On 25 May 2002, in Golfito, Puntarenas Province, Costa Rica (08° 39' N, 83° 09' W), we observed a House Wren holding a juvenile house gecko {Hemidactylus frenatus) in its bill. At the onset of our observation (11:06 CST), the bird held the gecko by the neck and was perched in the upper part of a bush (Ro- saceae), 1.5 m above the ground in a garden ' Escuela de Biologia, Univ. de Costa Rica, 2060, San Pedro, Montes de Oca, Costa Rica. 2 Corresponding author; e-mail: marco@ biologia. ucr.ac.cr on the campus of the Universidad de Costa Rica. The gecko was a characteristic uniform grayish-brown on the dorsum, and we esti- mate its size was approximately 3 cm (snout- vent length). While perched in the bush, the House Wren pounded the prey repeatedly against a branch, giving it strong shakes. Five min later, the bird flew to its nest in a nearby building with the gecko. The nest was placed about 2 m high on a beam of the open ceiling in one of the buildings’ porches; the nest con- tained three nestlings approximately 9 to 12 days old. Finally, the House Wren fed the gecko to one of its chicks. We examined the nest but did not find a discarded gecko, sug- gesting that a chick ate the prey and swal- lowed it completely. Cases of vertebrate predation by birds con- sidered to be insectivorous are scarce. For ex- ample, vertebrate predation has been observed in only 4 of 50 species of wood warblers (Pa- rulidae; Brown and Dickson 1994, Eaton 1995, Robinson 1995). Whereas there are lim- ited reports of atypical vertebrate prey having been taken by tanagers (Aborn and Froehlich 1995, Perez-Rivera 1997), woodcreepers, and leaftossers (Poulin et al. 2001), there are no such reports for wrens in Costa Rica (Stiles and Skutch 1989) or elsewhere (Guinan and Sealy 1987, Van Horne and Bader 1990, John- son 1998). Our observation is the first report of vertebrate predation by a House Wren. The house gecko, native to southern India, Sri Lanka, and Southeast Asia, is an invasive species that has widely extended its geograph- ic range, and is now established in Australia, China, East Africa, and North and Central SHORT COMMUNICATIONS 205 America (Meshaka et al. 1994, Schmidt et al. 1996). The house gecko likely invaded Costa Rica post- 1990 via shipping-port activity , along the Pacific coast. Despite its recent ar- rival, this small lizard has rapidly colonized and reached great abundance in lowland re- gions of Costa Rica (Savage 2002). The widespread distribution and abundance of house geckos in and near houses and build- I ings potentially makes this lizard an accessi- ble prey species for a diverse group of verte- brates. However, there are few studies that have investigated the relationship of this i gecko with other native species, and how they I might take advantage of this potential re- ' source (Petren and Case 1996). There are no : reports of house geckos as a food resource for ; any other native Costa Rican avian, mamma- ! lian, or reptilian species. Nevertheless, H. frenatus has an important effect on food webs 1 by depleting insect prey for other native geck- I os (Petren and Case 1996). Our observation suggests that more detailed studies of the re- ' lationship between this gecko and native spe- 1 cies are needed. ACKNOWLEDGMENTS We acknowledge C. E. Sanchez, G. Barrantes, R E. Allen, J. M. Robertson, B. Poulin, and two anonymous referees for their valuable comments to improve this manuscript. We are also grateful to J. Sanchez and B. ' Young for their help finding literature and for their ' excellent suggestions. LITERATURE CITED I Aborn, D. a. and D. Froehi.ich. 1995. An observa- ' tion of a Summer Tanager attempting to eat an ' Anolis lizard. Journal of Field Ornithology 66: 501-502. i, Barranths, G., j. Chavf:s-Cami>os, and J. E. Sanchez. 2002. Updated list of the birds of Costa Rica: with notes on conservation status. Asocia- cion Ornitologica de Costa Rica, San Jose, Costa Rica. Brown, R. E. and J. G. Dickson. 1994. Swainson’s Warbler {Limnothlypis swainsonii). The Birds of North America, no. 126. Eaton, S. W. 1995. Northern Waterthrush {Seiurus noveboracensis). The Birds of North America, no. 182. Guinan, D. M. and S. G. Sealy. 1987. Diet of House Wrens {Troglodytes aedon) and the abundance of the invertebrate prey in the dune-ridge forest. Del- ta Marsh, Manitoba. Canadian Journal of Zoology 65:1587-1596. Johnson, L. S. 1998. House Wren {Troglodytes ae- don). The Birds of North America, no. 380. Meshaka, W. E., Jr., B. P. Butterheld, and B. Hauge. 1994. Hemidactylus frenatus established on the Lower Florida Keys. Herpetological Re- view 25:127-128. Perez-Rivera, R. a. 1997. The importance of verte- brates in the diet of tanagers. Journal of Field Or- nithology 68:178-182. Petren, K. and T. J. Case. 1996. An experimental demonstration of exploitation competition in an ongoing invasion. Ecology 77:118-132. Poulin, B., G. Lefebvre, R. Ibanez, C. Jaramillo, C. Hernandez, and A. S. Rand. 2001. Avian pre- dation upon lizards and frogs in a Neotropical un- derstorey. Journal of Tropical Ecology 17:21-40. Robinson, W. D. 1995. Louisiana Waterthrush {Seiurus motacilla). The Birds of North America, no. 151. Savage, J. M. 2002. The amphibians and reptiles of Costa Rica: a herpetofauna between two conti- nents, between two seas. University of Chicago Press, Chicago, Illinois. Schmidt, W., E Mendoza, and M. E. Martinez. 1996. Range extensions for Hemidactylus frenatus in Mexico. Herpetological Review 27:40. Stiles, E G. and A. E Skutch. 1989. A guide to the birds of Costa Rica. Cornell University Press, Ith- aca, New York. Van Horne, B. and A. Bader. 1990. Diet of nestling Winter Wrens in relationship to food availability. Condor 92:413-420. Wilson Bulletin I I 7(2):2()6-209, 2005 Ornithological Literature Edited by Mary Gustafson SAN DIEGO COUNTY BIRD ATLAS. By Philip Unitt. Proceedings of the San Diego Natural History Museum No. 39, Ibis Pub- lishing, Temecula, California. 2005: 645 + vi pp., 468 color photos, several hundred maps and figures, 9 tables, 3 appendices. ISBN: 0934797218, $80.00 (cloth).— Let this review begin with the only flaw I could find while devouring a publication that may well be the most important book about California birds since Grinnell and Miller’s 1944 standard- bearer, The Distribution of the Birds of Cali- fornia (Pacific Coast Avifauna No. 27). The flaw is, simply, that its title '"San Diego Coun- ty Bird Atlas' ' understates the vast contribu- tions of this effort by Unitt, several other con- tributing writers, and over 400 volunteers. The title might suggest that this is merely another in a worthy line of the Golden State’s county- level breeding bird atlases that includes W. D. Shuford’s The Marin County Breeding Bird Atlas: A Distributional History of Coastal California Birds (California Avifauna Series 1, Bushtit Books, Bolinas, California, 1993) and D. Roberson and C. Tenney’s Atlas of the Breeding Birds of Monterey County, Califor- nia (Monterey Peninsula Audubon Society, Carmel, California, 1993). However, in addi- tion to being a thorough breeding bird atlas, San Diego County Bird Atlas also reports the results of a detailed winter atlas scheme and, furthermore, is an expanded reworking of the author’s earlier publication. The Birds of San Diego County (San Diego Society of Natural History, Memoir 13, 1984). The Atlas thus treats all species, including transients and va- grants. It is also the most detailed and critical treatment of subspecies of southern Califor- nia’s birds in decades. The parochial title is an understatement, as well; although San Di- ego County may be geographically tucked into the far southwest corner of the United States, it boasts a bird list — 493 species plus 87 additional subspecies — that is exceeded by no other county (or any region of comparable area) in the nation. This lofty total is a func- tion of habitat and topographic diversity and a legacy of active ornithological field work and birding activity. San Diego County lies at the heart of the southern half of the California Floristic Province and has become a key area for bird conservation issues since — as the au- thor points out on the very first page — its hu- man population (approaching 3 million) con- tinues to increase at third-world rates while consuming resources at first-world rates. San Diego County stretches from the Pa- cific Coast eastward over coastal hills and the Peninsular Range (to 1,990 m elevation), then down into the Colorado Desert. Its diminish- ing coastal sage scrub was the subject of the landmark work of Soule et al. (Reconstructed dynamics of rapid extinctions of chaparral-re- quiring birds in urban habitat islands. Conser- vation Biology 2:75-92, 1988) on habitat fragmentation, and its chaparral and oak-co- nifer woodlands are subjected to great pertur- bations (some 1,715 km^ of these habitats burned in 2002 and 2003, shortly after the completion of atlas field work). The county is home to a massive Marine Corps base (Camp Pendleton), Anza-Borrego Desert State Park (2,427 km^), and considerable National Forest and state park land in the mountains; there is a huge Navy presence in San Diego Bay, as well. Rapidly expanding suburban develop- ment continues in concert with important, al- beit imperfect, habitat conservation planning. San Diego County is thus a robust microcosm of California and the entire nation. This attractive and richly illustrated book begins with a detailed methodology chapter explaining the field work conducted from March 1997 to February 2002. The atlas grid is based on township/range/section boundar- ies, with the 479 cells averaging about 23 km^; this is a bit at odds with other California atlas efforts, but such grid differences are triv- ial for biogeographical analysis. After a five page summary of important results and a re- view of the species account format, the Atlas provides a concise summary of avian habitats, conservation issues, and impacts of wildfire. The species accounts form the bulk of the text. 206 ORNITHOLOGICAL LITERATURE 207 with account lengths varying from a couple of paragraphs for vagrants to two to three pages for most breeding species. Maps illustrate geographical distribution of the breeding range, with abundance and certainty of breed- ing confirmation coded by differing intensities of green and hatching in each atlas cell. For wintering species, or species whose breeding and wintering status differ greatly, an addi- tional map shows winter distribution (based on field work from December through Feb- ruary) with three shades of blue indicating abundance, based on individuals encountered per hour. Additional cells in which only mi- grants were recorded are shaded in gray; for some breeding species, former (pre-1997) breeding cells are colored red. Breeding spe- cies merit an additional graphic that portrays nesting phenology. Exotic species (including a growing resi- dent population of Black-throated Magpie- Jays, Calocitta colliei) and hypothetical spe- cies are treated briefly in a section subsequent to the main species accounts. There follows appendices listing all avian taxa recorded in San Diego County (most are documented by specimens in the San Diego Natural History Museum) and the scientific names of plants mentioned in the text. A third appendix pro- vides locality data (and sometimes date) for the hundreds of color photographs; roughly half of the photos were taken in San Diego County. Among the many strengths of the species accounts are the thoughtful Conservation sec- tions provided for most species; population and range changes are discussed here in detail. Declines are many, but a surprising suite of species has adapted to urban and suburban habitats and expanded accordingly; these in- clude the Red-shouldered {Buleo luieatus) and Cooper’s hawks {Accipiter coopcrii), Nuttall’s Woodpecker U^icoides niittallii). Pacific-slope Flycatcher {EtupUlonax (lifficilis). Western Bluebird (Sicilia mexicana), and Dark-eyed Junco (Jimco hycniaUs). Also excellent are the critical analyses of subspecies occurring in the county; Unitt excels at a sensible and modern application of the subspecies concept, reject- ing ill-supported taxa but championing “good" subspecies as illuminating ecological adaptations, endemism, and seasonal popula- tion movements. As if the sheer amount of useful informa- tion in this book weren’t enough, the author’s prose is highly readable and at times strays refreshingly from stiff, scientific style. His nearly 20 years at the editorial helm of the journal. Western Birds, have clearly served him (and us) well. Praise for the author, how- ever, should not minimize the labor, guidance, and technical expertise of many others in- volved in the Atlas. Production values are high throughout, and any errors are surely minimal. This attractive production, however, does carry a rather stiff price, and one can’t help but think that a version without color on virtually every page might have come in at half the price and encouraged wider distribu- tion. The bottom line, though, is that I rec- ommend saving your personal and institution- al pennies for this book — it’s worth it. All birders and field ornithologists within hun- dreds of miles of San Diego County should have a copy. Those who are more geograph- ically estranged from San Diego will still find great value in this work as a model atlas and regional treatment of status, ecology, and geo- graphic variation. — KIMBALL L. GARRETT, Natural History Museum of Los Angeles County, Los Angeles, California; e-mail: kgarrett @ nhm.org CURASSOWS AND RELATED BIRDS. By Jean Delacour and Dean Amadon, with an updated chapter by Josep del Hoyo and Anna Motis. Illustrated by Albert E. Gilbert. Lynx Edicions, Barcelona, Spain. 2004: 476 pp., 52 black-and-white maps and figures, 56 color plates, 6 dichotomous keys. ISBN: 8487334644. $75.00 (cloth). — This book is a revision of one published approximately 30 years ago, also by Jean Delacour and Dean Amadou, fhe original was an elegant book about a cryptic and little known group of trop- ical birds — the Cracids. Delacour and Ama- don published in that book every bit of infor- mation they came across, from notes scribbled by zoo curators to recortls of habitat, voice, ami other important asjK'cts of natural history scrawled during brief research trips to the na- tive haunts of ('racids. When they wrote the book, they probably had no idea that they 208 THE WILSON BULLETIN • Vol. 1 17, No. 2, June 2005 were building the foundation for what would expand into a passion for an avian group on which Neotropical ornithologists would sub- sequently focus a large body of autecological research. Today, the lUCN/Birdlife Cracid Specialist Group (CSG) boasts a list of some 500 correspondents, many of which are “cra- cidologists” actively working in the field; for this band of dedicated scientists, the original book by Delacour and Amadon served as a bible, of sorts. The revised Curassows and Related Birds is divided into three major parts. The first (pages 18-206) comprises the original book with black-and-white figures that appeared therein. The second part (pages 207-320) con- tains color plates from the Cracid section in Handbook of the Birds of the World, vol. 2: New World vultures to guineafowl; plates from the original book; and some updates (in- cluding 15 plates of downy young). The final part (pages 321-476) is the updated chapter by del Hoyo and Motis. Over the past decade, the CSG has published a plethora of books (approximately 1,000 pages in more than 100 chapters of four separate books in three lan- guages), as well as a trilingual, biannual bul- letin (20 volumes containing approximately 50 articles to date); the updated chapter is pri- marily an exhaustive compilation of those works. One problem with this book is that some of the information already published by the CSG was incorrectly summarized in the chapter by del Hoyo and Motis. For example, in a dis- cussion of the Chaco Chachalaca {Ortalis can- icollis) on page 339, del Hoyo and Motis state that, “. . . only one sighting involved a group of nine birds (Brooks 1997b).” When one checks the cited reference however, flocks of nine were actually observed more than once. Another criticism of this book is that it is not bilingual. Only one species of Cracid (the Plain Chachalaca, Ortalis vetula) occurs in the United States (in the southern-most three counties of Texas), whereas the other 49 spe- cies occur entirely in Latin America. As such, the primary audience of this book will be La- tinos, whose first language may not be En- glish. The hefty price of $75.00 will also make this book prohibitive in the libraries where it is needed most. However, many of the cracidologists using this book will already have web access to CSG’s trilingual publica- tions and will be able to read there the ma- terial summarized in the del Hoyo and Motis chapter.— DANIEL M. BROOKS, Houston Museum of Natural Science, Houston, Texas; e-mail: dbrooks@hmns.org BIRDS OF THE BAJA CALIFORNIA PENINSULA: STATUS, DISTRIBUTION, AND TAXONOMY. By Richard A. Erickson and Steve N. G. Howell (Eds.). American Birding Association Monographs in Eield Or- nithology No. 3, Colorado Springs, Colorado. 2001: 261 pp. ISBN: 1878788396. $39.95 (paper). — This volume is a collection of eight papers and five appendices on the status and distribution of the birds of Baja California. In the preface, the editors lament the end of an era of “frontier” birding in Baja California — brought on by the publication of this volume. While discoveries of new species are certain to decline with time, I suspect that interest in birding and ornithology in Baja California will be enhanced by the information contained in this book. Perhaps the “frontier” era that Erickson and Howell lament the end of is the unbirded, wide open spaces and the chance for making new discoveries. Several of the papers included in this book discuss breeding birds of Baja California. The first is a summary of breeding records for the nine eco-regions of the peninsula, with en- demic species and subspecies highlighted. It is depressing to see the number of extinct en- demic taxa listed, although most are limited to Guadeloupe Island, which has been heavily impacted by introduced mammals. Each eco- region is briefly described and dominant hab- itat types are noted. Typical breeding species are listed for each eco-region, with notes on endemic taxa and selected subspecies. Einally, a table lists taxa (including selected subspe- cies groups) and their breeding status for each eco-region. Short papers on breeding records for selected areas include reports on breeding birds of the Cerro Prieto geothermal ponds in the Mexicali Valley and the Vizcaino Desert; these records are incorporated in the Regional compilation but more detailed information on breeding status is provided in these short pa- pers. ORNITHOLOGICAL LITERATURE 209 Information on year-round status of select- ed Regions is also provided; most noteworthy is an annotated checklist for the Colorado De- sert. Two papers discuss important observa- tions and discoveries of birds in Baja Califor- nia Sur and a summary of noteworthy records from 1967 to 1971. A third documents more recent, noteworthy records and includes brief descriptions for some of the observations, al- lowing interested readers access to the origi- nal field notes. The emphasis in this paper is on migration, and counts are given for various excursions the authors have made to Baja Cal- ifornia during migration periods. A final an- notated checklist of the birds of Baja is an appropriate conclusion to the papers. Color figures are collected in one section, and include a remarkable set of photographs of rare birds, field sketches, photographs of selected habitats and eco-regions, and maps. The photographs are variable in quality, as one might expect of documentations of rare birds, but they represent a wonderful compi- lation of the rare and noteworthy birds of Baja California. Five Appendices are included as well. These consist of a database of selected obser- vations, a list of notable specimens, a log of sight records archived at the San Diego Mu- seum of Natural History, records of native species offered for sale or held in captivity (potential escapees), and a summary of spe- cies of potential conservation concern. This monograph represents a wealth of in- formation on the birds of Baja California. Al- though records of breeding or occurrence that are not accepted by the authors are not readily found in text, the book stands as a testament to the value of gathering information from a wide variety of sources and compiling it into a useful summary. This book is recommended to anyone with an interest in the status and distribution of birds. — MARY GUSTAFSON, USGS Patuxent Wildlife Research Center, Laurel, Maryland; e-mail: mary_gustafson@ usgs.gov ™s.ssueof™.W,... — waspu.Us.edo„2Uune2 210 THE WILSON BULLETIN Editor JAMES A. SEDGWICK U.S. Geological Survey Fort Collins Science Center 2150 Centre Ave., Bldg. C. Fort Collins, CO 80256-8118, USA E-mail: wilsonbulletin@usgs.gov Review Editor MARY GUSTAFSON U.S. Geological Survey Patuxent Wildlife Research Center Laurel, MD 20708-4037, USA E-mail: WilsonBookReview @aol.com Index Editor KATHY G. BEAL Editorial Board KATHY G. BEAL CLAIT E. BRAUN RICHARD N. CONNER KARL E. MILLER Editorial Assistants M. BETH DILLON ALISON R. GOFFREDI CYNTHIA P. MELCHER GUIDELINES FOR AUTHORS Consult the detailed “Guidelines for Authors” found on the Wilson Ornithological Society Web site (http://www.ummz.lsa.umich.edu/birds/wilsonbull.html). NOTICE OF CHANGE OF ADDRESS If your address changes, notify the Society immediately. Send your complete new address to Ornitho- logical Societies of North America, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. The permanent mailing address of the Wilson Ornithological Society is: % The Museum of Zoology, The Univ. of Michigan, Ann Arbor, MI 48109. Persons having business with any of the officers may address them at their various addresses given on the inside of the front cover, and all matters pertaining to the Bulletin should be sent directly to the Editor. Membership inquiries should be sent to James L. Ingold, Dept, of Biological Sciences, Louisiana State 'niv., Shreveport, LA 71115; e-mail: jingold@pilot.lsus.edu MEMBERSHIP INQUIRIES CONTENTS A NEW SPECIES OF GNATCATCHER FROM WHITE-SAND FORESTS OF NORTHERN AMAZON- IAN PERU WITH REVISION OF THE POLIOPTILA GUIANENSIS COMPLEX — — .Bret M. Whitney and Jose Alvarez Alonso MOVEMENTS AND HOME RANGES OF MOUNTAIN PLOVERS RAISING BROODS IN THREE COLORADO LANDSCAPES Victoria J. Dreitz, Michael B. Wander, and Fritz L. Knopf WINTER FORAGING OF LONG-TAILED DUCKS (CLANGULA HYEMALIS) EXPLOITING DIFFER- ENT BENTHIC COMMUNITIES IN THE BALTIC SEA - - Ramunas Zydelis and Dainora Ruskyte BREEDING BIOLOGY OF JABIRUS {JABIRU MYCTERIA) IN BELIZE Rose Ann Barnhill, Dora Weyer, W Ford Young, Kimberly G. Smith, and Douglas A. James ABUNDANCE, HABITAT USE, AND MOVEMENTS OF BLUE- WINGED MACAWS {PRIMOLIUS MARACANA) AND OTHER PARROTS IN AND AROUND AN ATLANTIC FOREST RESERVE — Beth E. /. Evans, Jane Ashley, and Stuart J. Marsden REPRODUCTIVE SUCCESS OF PIPING PLOVERS AT BIG QUILL LAKE, SASKATCHEWAN Wayne C. Harris, David C. Duncan, Renee J. Franken, Donald T McKinnon, and Heather A. Dundas BREEDING ECOLOGY OF WHITE-WINGED DOVES IN A RECENTLY COLONIZED URBAN ENVIRONMENT Michael F Small, Cynthia L. Schaefer, John T Baccus, and Jay A. Roberson SPOTLIGHT SURVEYS FOR GRASSLAND OWLS ON SAN CLEMENTE ISLAND, CALIFORNIA Anne M. Condon, Eric L. Kershner, Brian L. Sullivan, Douglass M. Cooper, and David K. Garcelon FERRUGINOUS PYGMY-OWLS: A NEW HOST FOR PROTOCALLIPHORA SIALIA AND HESPER- OCIMEX SONORENSIS IN ARIZONA Glenn A. Proudfoot, Jessica L. Usener, and Pete D. Teel EXTREMELY LOW NESTING SUCCESS AND CHARACTERISTICS OF LIFE HISTORY TRAITS IN AN INSULAR POPULATION OF PARUS VARIUS NAMIYEI - ..Noriyuki Yamaguchi and Hiroyoshi Higuchi SHORT COMMUNICATIONS FIRST RECORD OF BRONZED COWBIRD PARASITISM ON THE GREAT-TAILED GRACKLE — Brian D. Peer, Stephen I. Rothstein, and James W. Rivers A CAUSE OF MORTALITY FOR AERIAL INSECTIVORES? Muir D. Eaton and Daniel L. Hernandez FIRST RECORD OF SWAINSON’S WARBLER PARASITISM BY PROTOCALLIPHORA BLOW FLY LARVAE Mia R. Revels and Terry L. Whitworth FIRST RECORD OF EURASIAN JACKDAW (CORPUS MONEDULA) PARASITISM BY THE GREAT SPOTTED CUCKOO (CLAMATOR GLANDARIUS) IN ISRAEL Motti Charter, Amos Bouskila, Shaul Aviel, and Yossi Leshem HOUSE WREN PREYS ON INTRODUCED GECKO IN COSTA RICA — Marco D. Barquero and Branko Hilje ORNITHOLOGICAL LITERATURE TIieWIsonBulletin PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY VOL. 117, NO. 3 SEPTEMBER 2005 PAGES 211-326 (ISSN 0043-5643) MCZ .IBRARY SEP 2 6 2005 THE WILSON ORNITHOLOGICAL SOCIETY FOUNDED DECEMBER 3, 1888 Named after ALEXANDER WILSON, the first American Ornithologist. President — Doris J. Watt, Dept, of Biology, Saint Mary’s College, Notre Dame, IN 46556, USA; e-mail: dwatt@saintmarys.edu First Vice-President — James D. Rising, Dept, of Zoology, Univ. of Toronto, Toronto, ON M5S 3G5, Canada; e-mail: rising@zoo.utoronto.ca Second Vice-President — E. Dale Kennedy, Biology Dept., Albion College, Albion, MI 49224, USA; e-mail: dkennedy@albion.edu Editor — James A. Sedgwick, US. Geological Survey, Fort Collins Science Center, 2150 Centre Ave., Bldg. C, Fort Collins, CO 80526, USA; e-mail: wilsonbulletin@usgs.gov Secretary — Sara R. Morris, Dept, of Biology, Canisius College, Buffalo, NY 14208, USA; e-mail: morriss@canisius.edu Treasurer — Melinda M. Clark, 52684 Highland Dr., South Bend, IN 46635, USA; e-mail: MClark@tcservices.biz Elected Council Members — Robert C. Beason, Mary Gustafson, and Timothy O’Connell (terms expire 2006); Mary Bomberger Brown, Robert L. Curry, and James R. Hill, III (terms expire 2007); Kathy G. Beal, Daniel Klem, Jr., and Douglas W. White (terms expire 2008). Membership dues per calendar year are: Active, $21.00; Student, $15.00; Family, $25.00; Sustaining, $30.00; Life memberships $500 (payable in four installments). The Wilson Bulletin is sent to all members not in arrears for dues. THE JOSSELYN VAN TYNE MEMORIAL LIBRARY The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed in the Univ. of Michigan Museum of Zoology, was established in concurrence with the Univ. of Michigan in 1930. Until 1947 the Library was maintained entirely by gifts and bequests of books, reprints, and ornithological mag- azines from members and friends of the Society. Two members have generously established a fund for the purchase of new books; members and friends are invited to maintain the fund by regular contribution. The fund will be administered by the Library Committee. Terry L. Root, Univ. of Michigan, is Chairman of the Committee. The Library currently receives over 200 periodicals as gifts and in exchange for The Wilson Bulletin. For information on the library and our holdings, see the Society’s web page at http://www.ummz.lsa.umich.edu/birds/wos.html. With the usual exception of rare books, any item in the Library may be borrowed by members of the Society and will be sent prepaid (by the Univ. of Michigan) to any address in the United States, its possessions, or Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers, as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to: Josselyn Van Tyne Memorial Library, Museum of Zoology, The Univ. of Michigan, 1109 Geddes Ave., Ann Arbor, MI 48109-1079, USA. Contributions to the New Book Fund should be sent to the Treasurer. THE WILSON BULLETIN (ISSN 0043-5643) THE WILSON BULLETIN (ISSN 0043-5643) is published quarterly in March, June, September, and December by the Wilson Ornithological Society, 810 East 10th St., Lawrence, KS 66044-8897. The subscription price, both in the United States and elsewhere, is $40.00 per year. Periodicals postage paid at Lawrence, KS. POSTMASTER; Send address changes to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. All articles and communications for publications, books and publications for reviews should be addressed to the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology, Ann Arbor, Michigan 48109. Subscriptions, changes of address and claims for undelivered copies should be sent to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. Phone: (254) 399-9636; e-mail: business@osnabirds.org. Back issues or single copies are avail- able for $12.00 each. Most back issues of the Bulletin are available and may be ordered from OSNA. Special prices will be quoted for quantity orders. All issues of The Wilson Bulletin published before 2000 are accessible on a free Web site at the Univ. of New Mexico library (http://elibrary.unm.edu/sora/). The site is fully searchable, and full-text reproduc- tions of all papers (including illustrations) are available as either PDF or DjVu files. © Copyright 2005 by the Wilson Ornithological Society Printed by Allen Press, Inc., Lawrence, Kansas 66044, U.S.A. 0 This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). FRONTISPIECE. Henslow’s Sparrow {Ammodramus henslowii) in longleaf pine savanna in winter. Bechtoldt and Stouffer found an overall pattern of decreasing abundance with increasing time since burn treatment, seed abundance was the best predictor of Henslow’s Sparrow relative abundance. Original painting (acrylic and gouache) by Barry Kent MacKay. THE WILSON BULLETIN A QUARTERLY JOURNAL OF ORNITHOLOGY Published by the Wilson Ornithological Society VOL. 117, NO. 3 September 2005 PAGES 211-326 Wilson Bulletin 1 17(3):21 1-225, 2005 HOME-RANGE SIZE, RESPONSE TO FIRE, AND HABITAT PREFERENCES OF WINTERING HENSLOW’S SPARROWS CATHERINE L. BECHTOLDT'-2 AND PHILIP C. STOUFFER'-^'* ABSTRACT. — Henslow’s Sparrow {Ammodramus henslowii) is a declining, disturbance-dependent grassland bird that winters in the longleaf pine (Pinus palustris) ecosystem of the southeastern United States. During two winters (2001, 2002), we estimated the relative abundances, movement patterns, and habitat associations of Henslow’s Sparrows wintering in habitat patches differing in time since last burn (burn treatment). We conducted our study in southeastern Louisiana in Andropogon spp. -dominated longleaf pine savanna habitat. Henslow’s Sparrows were most abundant in savannas burned the previous growing season, with a mean relative abundance of 2.6 individuals/ha. The most dramatic decline occurred between burn year 0 and year 1 (first and second winters after burning), when mean relative abundance dropped to 1.0 individual/ha. Home-range size of radio- tagged birds was not correlated with burn treatment. All radio-tagged individuals maintained stable home ranges, with a mean size of 0.30 ha. Vegetation characteristics differed significantly among burn treatments. Sites burned the previous growing season had low vegetation density near the ground, vegetation taller than 1 .0 m, and high seed abundance. These variables were all highly correlated with Henslow’s Sparrow relative abundance, but seed density best predicted Henslow’s Sparrow numbers. We recommend a biennial, rotational burn regime to maintain habitat characteristics correlated with Henslow’s Sparrow abundance. Received 8 November 2004, accepted II June 2005. The Henslow’s Sparrow {Ammodramus henslowii) is one of the fastest-declining dis- turbance-dependent bird species in North America. Breeding populations, which range from southern Canada through the Northeast and Midwest of the United States, have been decreasing at a rate of 8.6% per year since 1966 (Sauer et al. 2004), likely due to habitat lo.ss (Askins 1993, Pruitt 1996, Herkert 1997, Cully and Michaels 2000). Breeding habitat requirements are generally well understood. ' Dept, of Biological .Sciences, Southeastern Loui- siana Univ., Hammond, LA 70402, USA. ’Current address: Inst. Nacional de Besquisas da Amazonia, Colei^oes Zooldgicas, Curadoria de Aves, C.P. 478, Av. Andre Araujo 2936, Bctiopolis, 69060- (K)l, Manaus, Amazonas, Brasil. ^ Current address: .School of Renewable Natural Re- sources, Louisiana .State Univ. and I.ouisiana .State Univ. AgCenter. Baton Rouge. LA 70803-6202. USA. ■* Corresponding author; e-mail: pstouffer^''lsu.cdu Henslow’s Sparrows respond favorably to burning, haying, mowing, and hardwood re- duction, achieving highest breeding densities 2—4 years after disturbance, when herbaceous vegetation is dense and woody vegetation is sparse (Zimmerman 1988; Herkert 1991, 1994, 1998; Swengel 1996; Herkert and Glass 1999; Cully and Michaels 2()()0). Secretive winter behavior prevents an ac- curate regional estimation of winter popula- tion status, but there is some information on habitat use patterns. Henslow's .Sparrows win- ter along the southeastern Gulf Coastal Plain, a region historically dominated by the fire- maintained longleaf pine (Pinus pa/ustris) ecosystem. .Studies in Mississippi (Chandler and Woodrey 1995), western Louisiana (Car- rie et al. 2002), and along the Florida-AIa- bama bottler (Plentovich et al. 1999. Tucker and Robinsofi 2003) have revealed greater winter abundance of Henslow's .Sparrows in 212 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 recently burned or disturbed sites; further- more, there is evidence that Henslow’s Spar- rows exhibit site fidelity over the winter, al- though no between-year recaptures have been documented (Plentovich et al. 1998). Home- range size during winter has not been esti- mated. Two studies have included banding wintering Henslow’s Sparrows, but neither study has attempted to systematically estimate abundance using capture data (Chandler and Woodrey 1995, Plentovich et al. 1998). Wintering Henslow’s Sparrows have been associated with a variety of habitat character- istics, partially because each study conducted so far has considered a different community within the longleaf pine ecosystem. Habitat associations have been studied in lowland pitcher plant bogs, clearcut pine plantations, and upland savannas managed for timber pro- duction (Plentovich et al. 1998, 1999; Carrie et al. 2002; Tucker and Robinson 2003). Henslow’s Sparrow presence and abundance have been correlated with the density of Pan- icum verrucosum and Sarracenia spp. (Plen- tovich et al. 1999), low litter depth and a high percent cover of herbaceous vegetation (Car- rie et al. 2002), and high seed abundance and forb density (Tucker and Robinson 2003). No study has included dominant grass species composition among the vegetation measure- ments. Also, no study has emphasized winter habitat use of Henslow’s Sparrows on upland longleaf pine savannas managed to restore the floristics of the savannas that historically dominated the southeastern Gulf Coastal Plain. The longleaf pine ecosystem, including up- land savanna communities, once dominated 25-36 million ha of the southeastern United States (Platt et al. 1988, Frost 1993, Stout and Marion 1993, Ware et al. 1993). Historically, fires occurred approximately every 1-3 years, usually during the summer (Frost et al. 1986, Stout and Marion 1993, Frost 1998). Longleaf pine savanna has a bi-layered habitat struc- ture. Sparse stands of fire-tolerant longleaf pines form the overstory and a diverse her- baceous community occupies the understory. Without frequent fires, this ecosystem devel- ops into a beech-magnolia-sweet gum forest (Ware et al. 1993). In the Southeast, more than 98% of the original longleaf pine ecosystem has been lost (Frost 1993, Ware et al. 1993, Noss et al. 1995). In Louisiana, 95-99% of this habitat has been destroyed (Noss et al. 1995). The remaining habitat consists of remnants scat- tered across the landscape, and it is estimated that less than 0.7% (280,000 ha) of that is in good, fire-managed condition (Frost 1993). Considering the population declines and habitat loss experienced by Henslow’s Spar- rows, effective habitat management is vital. To assess the effects of prescribed burning on wintering Henlsow’s Sparrows in southeastern Louisiana, we intensively monitored savanna remnants managed under differing fire-return intervals. We used capture data to estimate relative abundance and radio-transmitters to provide the first estimates of home-range size for wintering Henslow’s Sparrows; we report the first between-year recaptures of wintering individuals. We also conducted comprehen- sive measurements of habitat characteristics, including vegetation structure, species com- position of grasses, and seed abundance. Fi- nally, we discuss our results and make man- agement recommendations based on our re- sults and those of previous studies. METHODS Study sites. — We chose eight study sites (see Table 1 for site names) located in St. Tammany and Tangipahoa parishes of south- eastern Louisiana. This region lies on the boundary of the Coastal Plain Rolling Hills and Coastal Flatlands, historically dominated by longleaf p'mQ/Andropogon spp. savanna (Frost 1993, Peet and Allard 1993). Study sites were dominated by native vegetation and were located within larger management areas composed of savanna and mixed woodlands. Site selection was based on amount of contig- uous savanna (>15 ha) and relative cover of woody vegetation. We required study sites with <30% shrub cover so as not to impede mist-net sampling (see below). At the time of the study, all sites had been fire-managed for at least 4 years, under the responsibility of The Nature Conservancy of Louisiana, the Louisiana Department of Wild- life and Fisheries, or the Girl Scouts of Amer- ica. Study sites (areas sampled) were 2.25-7.5 ha; most were >6.25 ha (Table 1). Total sa- vanna area surrounding each site differed. Study sites within the same burn regime were Bechtoldt and Stauffer • WINTER ECOLOGY OE HENSLOW’S SPARROWS 213 TABLE E Burn treatments and recent fire history of eight study sites in longleaf pine savanna sampled during winters 2001 and 2002, in Tangipahoa and St. Tammany parishes, southeastern Louisiana. Site name Management area (size in ha) Years since burn 2001 Years since burn 2002 Burn season and year Area sampled 2001 (ha) Area sampled 2002 (ha) RAM Lake Ramsay Wildlife Man- agement Area (489.7) Not sampled 0 Summer 200 U — 5.18 GSC Camp Whispering Pines (19.0) Not sampled 0 May 2001 2.25 BUI Abita Creek Elatwoods Pre- serve (321.3) 0 1 May 2000 4.76 6.13 BU3 Abita Creek Elatwoods Pre- serve (321.3) 0 1 May 2000 7.03 6.69 LRS Lake Ramsay Wildlife Man- agement Area (489.7) 1 2 May 1999 6.25 6.25 LRN Lake Ramsay Wildlife Man- agement Area (489.7) 1 2 May 1999 6.25 6.25 TNC Lake Ramsay Wildlife Man- agement Area (489.7) 2 3 July 1998 7.50 6.25 WMA Lake Ramsay Wildlife Man- agement Area (489.7) 2 3 August 1998 6.25 6.25 ® Exact date unavailable from management area records. separated by >0.63 km. In 2001, we moni- tored six sites, comprising two replicates each of three burn regimes (burn treatments): 0, 1, and 2 years since last burn. Year-0 sites were burned the growing season prior to sampling; for example, a site burned in May 2000 was sampled in January 2001. In 2002, we fol- lowed these six sites as they transitioned into the next burn treatment level and added two replicates in the year-0 burn treatment (Table 1). Relative abundance sampling. — Relative abundance estimates of Henslow’s Sparrows were based on systematic mist-net sampling of each study site. Sampling took place during two consecutive winter seasons: January ' through February 2001 (winter 2001) and late I November 2001 through February 2002 (win- ter 2002). During winter 2001, we sampled each site twice, once in January and once in j February. During winter 2002, each site was I sampled four times: we repeated the January , and February (2001) sampling protocol at ‘ each study site, and we took two more sam- ^ pies of a 2.25-ha subset within each site. Sub- sets were chosen consistently across all study sites to measure 150 m on a side, starting at the most accessible corner of the 6.25-ha plot. We deviated from this protocol at three sites in 2002 because of limited volunteers, inclem- ent weather, and unscheduled burn events. At site GSC, we conducted three 2.25-ha sam- ples. We sampled site TNG three times — two 6.25-ha samples and one 2.25-ha sample. WMA was sampled twice — one 2.25-ha sam- ple and one 5.0-ha sample. Overall, we com- pleted 40 sampling events on our eight study sites over the two study seasons. For mist-net sampling, we used a team of 4-10 people, spaced 3 m apart, moving sys- tematically across the study site (M. S. Wood- rey pers. comm.). The team maintained their spacing throughout the sampling event to en- sure even coverage of the site. Each time an Ammodramus sparrow flushed, the team marked the spot where they were walking, marked the area where the sparrow emerged from the herbaceous layer (“llush-from” lo- cation), and quickly set up a 6.0 X 2.5-m mist net near where the sparrow landed (capture location). The team then attempted to flush the sparrow into the net. All captured individuals were banded with a federal band (size OA). A subset of Henlsow's Sparrows was fitted with radio-transmitters (see Henslow's Sparrow movement patterns below). Birds with radio- transmitters were released at their “flush- from” location and birds without radio-trans- milters were released at their capture location. Relative abundance analysis. — Based on their similar behavior as they flushed from the grass, we also pursued Le Conte's Sparrows 214 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 (Ammodramus leconteii), which often could be distinguished from Henslow’s Sparrows only after being flushed into the net. During some sampling events, we detected one or more Ammodramus sparrows that we were un- able to capture or otherwise identify to species level. To estimate the relative abundance of each species across our study sites, we as- sumed that the relative proportion of identified Ammodramus sparrows reflected the real rel- ative abundance of each species. For each sampling event, we assigned unidentified Am- modramus individuals to either Henslow’s or Le Conte’s based on the abundance of iden- tified Ammodramus sparrows during that sam- pling event. In 2001, we had to adjust 75% of the samples; in 2002, when Le Conte’s Spar- row abundance was much lower, this adjust- ment was seldom needed (28% of samples ad- justed). We estimated relative abundance (Hens- low’s Sparrows/ha) by dividing the number of birds detected during a sampling event by the area sampled during that event. We used a nested analysis of variance (ANOVA) model to evaluate differences in relative abundance across burn treatments and study sites. Time since burn (burn treatment) was the main ef- fect, site was nested within burn treatment, and sampling event was the sampling unit. Since previous studies have revealed that more recently burned sites should have a greater abundance of Henslow’s Sparrows, we used an a priori contrast to compare Hens- low’s Sparrow abundance in burn treatment year 0 with all other burn treatments. We also evaluated whether sampling-team size was re- lated to abundance estimates by regressing rank transformed Henslow’s Sparrow abun- dance for the 40 sampling events on sampling- team size. Henslow’s Sparrow movement patterns. — A subset of birds {n = 27) captured during sam- pling events of winters 2001 and 2002 were fitted with radio-transmitters to determine movement patterns. We followed two or three individuals on each replicate of burn treat- ments 0 and 1 in 2001 and on burn treatments 0, 1, and 2 in 2002 {n = 5 sites). Transmitters (model BD-2A; Holohil Systems, Carp, On- tario, Canada) weighing 0.70 g (5.38% of mean body weight) were attached with elastic leg-loop harnesses (Rappole and Tipton 1991). Projected battery life was 21 days. In- dividuals were located daily by triangulation using a three-element yagi antenna and a Wildlife Materials TRX-64S (Murphysboro, Illinois) receiver. A single observer conducted all triangulations used in analyses. Locations consisted of 2-3 bearings to minimize time between triangulations (mean = 2.4 bearings). Mean time between triangulations was 5.9 min (SE = 0.53). Individuals were rarely seen, and triangulations were made from at least 12 m (mean = 41.4 m, SE = 2.98) away to min- imize observer effects on the behavior of ra- dio-tagged birds. Telemetry data analysis. — Home-range es- timates were based on 9 to 26 locations per individual (mean = 15.9, SE = 0.96). We used the program Location of a Signal (Eco- logical Software Solutions 2000) to compute locations from compass bearing data. Loca- tions were entered into ArcView (ESRI, Inc. 1999) as Cartesian coordinates and we used the Animal Movement extension (Hooge and Eichenlaub 1997) to determine home-range size. We used a bootstrap {n = 100, interval = 1, with replacement) of the minimum con- vex polygon estimate of 1 1 locations {n = \6 individuals) to determine mean home-range size. The bootstrap of nine locations (/i = 18 individuals) was used to analyze home-range size differences across burn treatments, study sites, and study years using ANOVA. Home- range size estimates were natural-log trans- formed to meet assumptions of normality and homogeneity of variances. We examined the bootstrapped minimum convex polygon home-range estimates avail- able for each individual to decide how many locations to include in the analyses described above. After nine locations (the minimum for any individual), the empirical mean home- range size reached 74% (SE = 0.03) of the bootstrapped estimate. With 1 1 locations, the empirical mean reached 83% (SE = 0.03) of the bootstrapped estimate. Based on these re- sults, our mean estimate of home-range size probably represents at least 83% of the actual home range for all of our individuals, with more accurate estimates for most individuals. Home-range size for wintering Henslow’s Sparrows stabilized at an average of 21 loca- tions during a study at the Mississippi Sand- hill Crane National Wildlife Refuge (Thatcher Bechtoldt and Stauffer • WINTER ECOLOGY OE HENSLOW’S SPARROWS 215 TABLE 2. Dominant grass species encountered on longleaf pine savanna study sites in southeastern Loui- siana during winters 2001 and 2002, grouped by morphotypes used in analyses. Dominant grass morphotypes Species included Andropogon sp\>JSchizachyriiim scoparium Panicum virgatum/P. rigidulurn Dichanthelium scabriusculum, Schizachyrium tenerum Muhlenbergia expansa Muhlenbergia expansa (without mature inflorescences) Ctenium aromaticum Aristida spp. Dichanthelium spp. Andropogon mohrii, A. virginicus, A. gerardii, Schiza- chyrium scoparium Panicum virgatum, P. rigidulurn Dichanthelium scabriusculum, Schizachyrium tenerum Muhlenbergia expansa (with mature inflorescences) Muhlenbergia expansa (without mature inflorescences) Ctenium aromaticum Aristida purpiirascens, A. dichotoma, A. afftnis, A. palustris Dichanthelium longiligulatum, D. acuminatum, D. dicho- tomum 2003), suggesting that our estimates were probably close to stabilizing for most birds. We used regression analysis to look for re- lationships between the relative abundance and mean home-range size of Henslow’s Spar- rows at each site (bootstrap of nine locations, n = 2\ individuals). Mean relative abundance at each study site was determined by summing the number of Henslow’s Sparrows/ha detect- ed during each sampling event and dividing that number by the total number of sampling events at that site. Characterizing vegetation. — During the two winter study seasons, we randomly chose ten 10-m-radius plots within each study site and sampled vegetation structure, dominant grass species composition, and seed abundance. The aggregate of plots covered 5% of the area at each study site. Only hve vegetation plots were sampled at one study site (GSC), which was only 2.25 ha in area. The same observer conducted all vegetation sampling, always during February to early March, before the onset of spring growth. We measured vegetation structure as vege- tation height, type of tallest vegetation, and density (using a 2,0-m pole marked in lO-cm increments). We measured 21 points in each vegetation plot: the center point and 5 mea- surements (every 2 m) in each of the four car- dinal directions (M. S. Woodrey pers. comm.). Vegetation height was measured as the tallest vegetation to fall within a 30-cm radius of the vegetation pole. We classified type of tallest vegetation as herbaceous or woody. Vegeta- tion density was measured at 9 of the 2 1 points within each vegetation plot. We count- ed the number of vegetative contacts with the pole within each 10-cm increment to estimate density. Number of contacts ranged from 0 to 10; contact counts >10 were placed in the “ten” category. Percent cover of woody veg- etation was measured by visually estimating (to the nearest 5%) shrub cover and by count- ing the number of trees >7.5 cm dbh within the plot. In each plot, we visually estimated percent cover of dominant grass species to the nearest 5%. All herbaceous cover visible from above was included, so totals could be greater than 100% if a sparse layer of grasses or shrubs revealed an understory. In our estimates of percent cover, we grouped some species to- gether if they had similar growth habits (Table 2). We separated one species, Muhlenbergia expansa, into plants with and without mature inflorescences. The mature inflorescences of Muhlenbergia expansa did not persist past the first winter, allowing us to readily distinguish plants that had flowered the previous growing season from those that had not. We estimated relative seed abundance by counting the number of stalks with mature in- florescences within one randomly placed 1.0- nP frame in each vegetation plot. Stalks were identified to genus or to species level when possible. We removed the grasses Dichan- theliuni spp. and Schizachyrium tenerum from the seed abundance analysis because of' the difficulty in distinguishing senescent stalks from sectl-producing stalks of the season. We excluded one site (LRS 2001) in seed abun- 216 THE WILSON BULLETIN • Vol. 1 17, No. 3, September 2005 dance analyses because stalks with mature in- florescences were not identified to species during data collection. Vegetation analysis. — Due to an unsched- uled burn of one site, we collected vegetation data at only one site in the 3-year treatment. Therefore, we included only sites in the 0-, 1-, and 2-year treatments in the vegetation anal- ysis, yielding four replicates of these three treatments over the study period. We used two principal components analyses (PCA) with varimax rotation to describe veg- etation structure and species composition of grasses across burn treatments and study sites. The PCA describing vegetation structure in- cluded vegetation height, vegetation density at heights from 0 to 0.3 m, percent shrub cover, number of woody contacts, and number of trees. We included vegetation density only from 0 to 0.3 m because a preliminary AN- OVA showed that vegetation density at heights above 0.3 m did not differ among burn treatments. The PCA describing species com- position included the percent cover values for the nine dominant grass species. Variables that loaded across more than one axis, or that did not load on any axis, were removed from the PCAs and treated separately. PCA scores for structure and species com- position were rank-transformed to meet as- sumptions for parametric tests, and a nested ANOVA model was used to test for differ- ences in vegetation characteristics among burn treatments and among sites within burn treat- ments. Burn treatment was the main effect, sites were nested within burn treatment, and vegetation plot was the sampling unit. When tests were significant, we used Bonferroni multiple comparisons to compare variation among individual treatments (Sokal and Rohlf 1995). Percent cover values of dominant grass species that did not load in the principle com- ponents analysis were rank-transformed and included in the backwards-stepwise multiple linear regression analysis described below. We used SYSTAT (SPSS, Inc. 2000) for all anal- yses. Data points were considered outliers and removed from analysis if Student /-values were >3.0. Seed abundance estimates were square-root transformed to meet assumptions of normality and homoscedasticity. We used a nested AN- OVA model to examine differences in seed abundance across burn treatments and sites within treatments. We used a Bonferroni mul- tiple comparison to examine relative differ- ences among burn treatments. We used backwards-stepwise multiple lin- ear regression analysis to examine the rela- tionship of vegetation characteristics to Hens- low’s Sparrow abundance. Variables were eliminated from analysis if they did not ex- plain a significant amount of variation in Henslow’s Sparrow abundance {P > 0.05) or if they were highly collinear (tolerance > 0.10). RESULTS Abundance in relation to burn treatment. — We detected 226 Ammodramus sparrows on the study sites over both years: 100 in 2001 and 126 in 2002. Identified birds included 135 Henslow’s Sparrows, 23 LeConte’s Sparrows, and 1 Grasshopper Sparrow {Ammodramus savannarum) during 40 sampling events. Of these, 88 Henslow’s Sparrows were banded. Henslow’s Sparrow abundance averaged 1.17 ± 0.32 individuals/ha, but was highly variable among study sites, ranging from 0 to 4.50 in- dividuals/ha. Henslow’s Sparrow relative abundance was highest in the most recently burned sites (AN- OVA, F3 JO = 3.61, P = 0.053; a priori con- trast 0 [mean = 2.61 ± 0.40] versus all other burn treatments [mean = 0.75 ± 0.14], Fj jq = 10.49, P = 0.009; Fig. 1). Henslow’s Spar- row abundance did not vary significantly be- tween study years (winter 2001: mean = 0.84 ± 0.21; winter 2002: mean = 1.45 ± 0.26; ANOVA, Fj 38 = 2.05, P = 0.16), but did vary across study sites within burn treatments 0 and 2 (ANOVA, burn treatment 0: F37 = 19.74, P = 0.001; burn treatment 1: F38 = 1.39, P = 0.32; burn treatment 2: F38 = 15.22, P = 0.001; burn treatment 3: F13 = 1.80, P = 0.27). Mean sampling-team size was 6.6 ± 0.23 people. Sampling-team size was evenly distributed across burn treatments and showed no relationship to the number of Henslow’s Sparrows detected/ha (Fj 33 = 0.64, P = 0.43, F2 = 0.02). Home-range size and site fidelity. — We banded 32 Henslow’s Sparrows in 2001. Among the 58 individuals captured in 2002, 2 were recaptures from 2001. Both recaptures were found within the management area of Bechtoldt and Stauffer • WINTER ECOLOGY OE HENSLOW’S SPARROWS 217 EIG. 1. In southeastern Louisiana during winters 2001 and 2002, Henslow’s Sparrow abundance was greatest in longleaf pine savanna study sites the first winter after a burn, as revealed by a nested ANOVA and an a priori contrast of burn treatment 0 (i.e., 0 years since last burn) versus all other burn treatments (filled bars, significant difference indicated by asterisk). Mean abundance of Henslow’s Sparrows varied within some burn treatments, but the overall pattern of decreasing abundance with increasing time since burn is apparent (unfilled bars). Asterisks over unfilled bars indicate significant differences within burn treatments, as revealed by one- way ANOVAs. original capture; one was found on a different study site 1.6 km away (LRS burn treatment 1 to RAM burn treatment 0), and the other was found on the same study site (LRS burn treatment 1 to LRS burn treatment 2). We re- eaptured eight individuals within study years. Reeaptures occurred in all burn treatments ex- cept year 3 and were always on the site of initial capture. The mean time between first and last capture was 42 days. Maximum time between captures was 70 days. We radio-tagged 27 individuals at five study sites during winters 2001 and 2002. Of these, 21 individuals wore their radios long enough to allow estimation of home-range size (/? = 9 locations). Three individuals at LRN in 2001 were not included in calculations of mean home-range size or in analyses. Home- range sizes at LRN in 2001 ranged from 0.92 to 3.31 ha (/? = 3 individuals using 1 1 loca- tions). These individuals were the only indi- viduals monitored by a second observer and were outliers in all analyses. Including these outliers disproportionately inlluenced the mean home-range size estimate, but did not change the results of nonparametric tests of the analyses described below. Home-range size varied from 0.09 to 1.50 ha {n = 16 individuals using 1 1 locations). All radio-tagged individuals maintained stable home ranges over the sampling period. Mean home-range size for Henslow’s Sparrows win- tering on our study sites was 0.30 ha (SE 0.09, n - \6 individuals using 11 locations). Home-range size did not vary across study years (F, = 0.30, P = 0.59) or sites (F4 ,, = 0.97, P = 0.46; Fig. 2). There was no differ- ence in home-range size across burn treat- ments (F215 = 0.52, P = 0.61). Home-range size was not related to relative abundance de- termined from mist netting (F, = 2.13, P = 0.20, F2 = 0.26). Vegetation strnetnre. — The PC A of vege- tation structure revealed two factors that ex- plained 68.8% of the variation in the data. Mean density between 0 and 0.3 m and mean height were inversely related on principal components axis 1 (iit:iciHT/i)HNsn \ ) and ex- plained 43.0% of the variation. Number of trees, percent shrub cover, and number of wootly contacts loaded positively on principle components axis 2 (W()ot)V) and explained 25.8% of the variation in the data. Hhi(',ht/ I)f:nsht varied significantly among burn treat- 218 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 0.7 n LU CO +1 03 e 0.5 - CD N CO 0 1 2 Years since burn FIG. 2. Mean home-range size for Hensiow’s Sparrows (n = 18 individuals, 9 locations) wintering in longleaf pine savannas of southeastern Louisiana during winters 2001 (filled bars) and 2002 (unfilled bars). Home-range size was not stable at nine loca- tions, but our data showed that estimates at nine lo- cations probably represented at least 74% of the actual home range for all individuals. Mean home-range size did not differ between study years, study sites, or burn treatments, as revealed by one-way ANOVAs. ments (^2,9 = 24.32, P < 0.001; Fig. 3 A). Year-0 sites had the lowest vegetation density close to the ground and the greatest vegetation height (Bonferroni, 0 versus 1, F = 0.007; 0 versus 2, P < 0.001; Table 3). Density in- creased and height decreased as time since burn increased. Individual study sites within burn treatment also differed from one another along the Height/Density axis = 5.27, P < 0.001). The amount of woody vegetation did not differ among burn treatments (F2 9 = 0.91, P = 0.44; Table 3), although sites within burn treatment had significantly different amounts of woody vegetation (F998 = 3.98, P < 0.001; Fig. 3A). Grass species composition. — Among the nine dominant grass morphotypes (Table 2), seven loaded onto two orthogonal factors, ex- plaining 53.1% of the variation in the data set. Principal components axis one (Species Di- versity) showed high positive loadings for Dichanthelium scabriusculum, Panicum vir- gatum/P. rigidulum, and Andropogon spp./ Schizachyrium scoparium. Muhlenbergia ex- pansa without mature inflorescences and Schi- zachyrium tenerum had high negative loadings HEIGHT/DENSITY 6 ^ ^ ^ r -3-2-1 01 2 3 SPECIES DIVERSITY FIG. 3. Scatter plots of PCA scores for vegetation structure (A) and percent cover of dominant grass spe- cies (B) during winters 2001 and 2002 in southeastern Louisiana pine savannas. Each symbol represents a vegetation plot. Plots are grouped by burn treatment (0, 1, and 2 years since last burn), with ellipses delin- eating one standard deviation from the burn-treatment means. Circles represent plots in the year-0 burn treat- ment, triangles represent year 1 , and asterisks represent year 2. (A) Burn treatments differ in height and den- sity, but not in amount of woody vegetation. On the Height/Density axis, year-0 sites had the tallest veg- etation and the lowest vegetation density near the ground. On the Woody axis, burn treatments did not differ in amount of woody vegetation. (B) Species di- versity was slightly higher in the year- 1 burn treatment than in the year-2 treatment. Sites in the year-0 burn treatment had significantly greater densities of Muh- lenbergia expansa with mature inflorescences and Ctenium aromaticum than sites in the year-2 treatment. Bechtoldt and Stoujfer • WINTER ECOLOGY OF HENSLOW’S SPARROWS 219 TABLE 3. Mean vegetation measurements for southeastern Louisiana pine savannas in three burn treatment classes. Sites were either 0, 1, or 2 years since last burn, as sampled during the winters of 2001 and 2002. We used these variables, except seed abundance, which was considered separately, to create principal components factors representing vegetation structure and dominant grass species composition. Nested ANOVA revealed differences in vegetation structure, dominant grass species composition, and seed abundance among burn treat- ments. Variable Year 0 Year 1 Year 2 Mean SE Mean SE Mean SE Vegetation structure Height (m) Density 0-0.1 m (no. of contacts) Density 0. 1-0.2 m (no. of contacts) Density 0.2-0. 3 m (no. of contacts) Number of trees >7.5 cm dbh Percent shrub cover Number of woody hits Percent cover of dominant grass species Andropogon spp. /Schizachyrium scoparium Panicum virgatum/P. rigidulum Dichanthelium scabriusculum Schizachyrium tenerum Muhlenbergia expansa Muhlenbergia expansa (without mature inflorescences) Cteniiim aromaticum Aristida spp. Dichanthelium spp. Seed density Number of stalks/m^ with mature inflorescences 1.28 0.02 1.21 0.03 0.98 0.02 3.31 0.24 6.55 0.31 8.08 0.28 2.38 0.18 5.18 0.32 6.50 0.28 1.37 0.15 2.95 0.23 3.88 0.18 1.93 0.41 2.00 0.53 2.39 0.58 23.50 2.91 26.02 2.73 31.35 3.30 2.13 0.43 1.57 0.41 1.73 0.28 21.33 2.47 16.50 2.07 18.00 2.39 5.17 1.72 8.75 1.46 2.13 0.91 5.67 1.72 16.13 2.81 6.13 1.92 2.17 1.12 11.25 3.53 15.88 3.31 11.67 2.83 0.13 0.13 0.88 0.87 0.67 0.67 5.75 1.39 26.88 3.20 8.67 3.06 0.00 0.00 0.00 0.00 3.17 1.00 6.88 1.35 1 1.13 2.61 2.50 1.45 20.88 4.24 26.63 4.16 83.61 7.91 52.24 7.59 23.45 4.57 on this axis. High positive loadings indicate high species diversity and high negative load- ings indicate low species diversity. Vegetation plots that load positively on this axis have a high proportion of a number of dominant spe- cies, while plots loading negatively are cov- ered by just one or two dominant species. Principal components axis two (Muhlenber- cia/Ctenium) was characterized by high load- ings Muhlenbergia expansa with mature in- florescences and Ctenium aromaticum and ex- plained 25.3% of the variation in the data. Ar- istida spp. and Dichanthelium spp. without mature inflorescences did not load onto either factor and are included separately in the mul- tiple regression analysis de.scribed below. Burn treatments were marginally distinct from one another along the Sphc'IHS Divhksity axis (F2.9 = 3.20, P = 0.10; Fig. 3B). Year-2 sites loaded negatively on this axis and tended to be less diverse than sites in burn treatments 0 and 1. Year-2 sites were tlominated by Muhlenbergia expansa with no mature inflo- re.scences and/or Schizachyrium tenerum ( fa- ble 3). Year-1 sites had positive loadings on this axis. These sites had high percent covers of Dichanthelium scabriusculum, Panicum virgatum/P. rigidulum, and Andropogon spp./ Schizachyrium scoparium and tended to have the highest diversity of grasses (Table 3). Year-0 sites were better described by principle components axis two {MunLENBERGiA/CrENtUM, see below). wSites within burn treatment levels differed significantly from one another along the Spkcies Diversity axis = 6.78, P < 0.001). The MuueenbergiaI Ctenium principal com- ponents axis separated year-0 sites from year- 2 sites (/'2.g = 5.70, P = 0.025; Bonferroni, P = 0.025; Fig. 3B). Year-0 sites loaded high and positive on this axis and had a greater abundance of Muhlenbergia expansa with ma- ture inflorescences and Ctenium aromaticum than year-2 sites (Table 3). Sites within burn treatment differed from one another in abun- tlance of Muhlenbergia with mature inflores- cences and Cteniutn (/-;,, ,7 = 5.75, /' < 0.001 ). Seed abundame. — fhe number of stalks 220 THE WILSON BULLETIN • Vol. J 17, No. 3, September 2005 Mean number of mature inflorescences/m^ EIG. 4. Mean number of mature inflorescences/m^ is the best predictor of Henslow’s Sparrow abundance in southeastern Louisiana pine savannas during winters 2001 and 2002, as revealed by a backwards-stepping multiple linear regression relating habitat characteris- tics to Henslow’s Sparrow abundance. with mature inflorescences differed among burn treatments (F28 = 13.91, P = 0.002; Ta- ble 3). Seeds were more abundant at year-0 and year-1 sites than at year-2 sites (Bonfer- roni, 0 versus 1: P = 0.17; 0 versus 2: P = 0.002; 1 versus 2: P = 0.061; Table 3). Seed abundance also varied among study sites with- in burn treatment = 2.15, P = 0.039), but it did not vary across study years (Fj ,05 = 0.82, P = 0.37). We removed three outliers with higher than expected seed abundances for their study site (Studentized residual >7.0). Relationship of Henslow’s Sparrow abun- dance to vegetation characteristics. — We used vegetation structure and species composition PCA scores, ranked percent cover values for Aristida spp. and Dichanthelium spp., and val- ues for seed abundance in a backwards-step- wise multiple regression analysis to examine the relationship between Henslow’s Sparrow abundance and vegetation characteristics. Mean seed abundance was the best predictor of Henslow’s Sparrow relative abundance (Fj g = 27.74, P = 0.001, F2 = 0.78; Fig. 4). Height/Density scores were significantly cor- related with mean seed abundance values (r = 0.93, P = 0.003). Height/Density scores were also highly, but not significantly, corre- lated with Henslow’s Sparrow abundance (r = 0.78, P == 0.20). Muhlenbergia/Ctenium, Spe- cies Diversity, and Woody scores did not ex- plain a significant amount of the variation in Henslow’s Sparrow abundance, nor did the percent cover of two grass species that did not load onto the PCA, Aristida spp. and Dichan- thelium spp. DISCUSSION The clear message from this and other stud- ies is that Henslow’s Sparrows use winter hab- itat with a recent history of disturbance. At our study sites, we saw the highest numbers of Henslow’s Sparrows in longleaf pine sa- vanna that was burned the previous growing season. Relative abundance of Henslow’s Sparrows decreased with increasing time since burn. We found significant differences in rel- ative abundance among individual study sites of the same burn age, but most sites changed predictably between years. Across sites, mean abundance decreased by over 90% between sites burned the previous growing season and those not burned for 3 years. Radio-tagged in- dividuals maintained small, stable home rang- es over the study period, but home-range size was not related to abundance or burn treat- ment. We also found evidence of between- year site fidelity. As in our study, studies of Henslow’s Spar- rows inhabiting lowland pitcher plant bogs and upland savanna managed for timber pro- duction revealed an inverse relationship be- tween abundance and time since burn (Carrie et al. 2002, Tucker and Robinson 2003). Me- chanical disturbance may have the same effect as burning, at least on some clearcut pine plantations (Plentovich et al. 1999). It is un- known to what extent Henslow’s Sparrows use other grasslands that experience periodic burning or mowing, such as power line right- of-ways and agricultural grasslands. Prelimi- nary investigations have found Henslow’s Sparrows wintering along power line right-of- ways (Burhans 2002; CLB unpubl. data). The restricted movement patterns of wintering Henslow’s Sparrows may allow them to ex- ploit these long, thin strips of habitat. Winter use of agricultural lands needs to be investi- gated, but land-use practices, such as midwin- ter haying, may have a negative effect on win- ter populations. We used a novel mist-net sampling tech- Bechtoldt and Stoiijfer • WINTER ECOLOGY OF HENSLOW’S SPARROWS 221 nique that proved to be an effective means of capturing, banding, and estimating the abun- dance of Henslow’s Sparrows. We evaluated the technique by observing the behavior of 10 radio-tagged individuals during sampling events. All radio-tagged birds flew above and landed back into the herbaceous layer when approached by the sampling team, suggesting that individuals exhibit a predictable response when approached. There was no relationship between team size and relative abundance of Henslow’s Sparrows, suggesting that varia- tions in team size did not affect abundance estimates. Within seasons, we expected to re- capture more than 8 of the 88 individuals banded; this low recapture rate suggests that individuals may learn net avoidance in sub- sequent sampling periods. We do not know whether differences in detectability among treatments may have influenced our results, but this could be examined with additional re- capture data. Our recapture and telemetry data confirm that Henslow’s Sparrows exhibit within-sea- son site fidelity (see also Plentovich et al. 1998). All within-year recaptures occurred within the 6.25-ha site of original capture, and recapture data showed that Henslow’s Spar- rows could use the same habitat patch for up to 70 days. Two individuals were recaptured between study years. Both recaptures occurred within the management area of original cap- ture, including one within the same study site, which could suggest some local between-year site fidelity for wintering Henslow’s Sparrows. The individual that returned to the same study site returned as the site transitioned to a year- 2 burn treatment. This site (LRS) had a higher relative abundance of Henslow’s Sparrows than any other site in the year-2 burn treat- ment, suggesting that this site was somehow more suitable for wintering Henslow’s Spar- rows, independent of burn treatment, fhe oth- er returning individual exhibited a habitat use pattern predicted by oiir sampling results, moving Irom a site in burn treatment 1 (LRS), to a site 1.16 km away, burned the previous growing season (RAM). Plentovich et al. (1998) tound that Henslow's Sparrows exhib- ited site fidelity over one season and specu- lated that the absence of between-year recap- tures indicated that preferred winter site con- ditions were too ephemeral — compared to an individual’s life span — to encourage between- year site fidelity. While this seems likely, our two between-year recaptures indicated that some, possibly regional, form of between-year site fidelity may exist and that, depending on local conditions, habitat patches may remain suitable in consecutive seasons. Still, radio- tracking data and within-year recaptures sug- gest that arriving individuals must be able to select a habitat patch that will be suitable for the entire season. Examining settlement pat- terns and age-structure of wintering Hens- low’s Sparrows across a range of habitat patches may reveal more about how this pro- cess occurs. Radio-tagged Henslow’s Sparrows main- tained stable home ranges over the winter. Ra- dio-tagged individuals were consistently lo- cated in the same area of a study site over the sampling period. Our estimates of home-range size must be considered minimum estimates, as home-range size did not stabilize for any radio-tagged individual over the sampling pe- riod. Even so, our home-range size estimate (0.30 ha) roughly agrees with a simultaneous study of wintering Henslow’s Sparrows at the Mississippi Sandhill Crane Refuge. In Missis- sippi, the mean home-range size (minimum convex polygon, 95% kernel) was 0.45 ha {n = 42 individuals with at least 21 locations; Thatcher 2003). Home-range size did not differ among burn treatments or across study years. Eurthermore, home-range size did not show any relationship to relative abundance, a suiprising observa- tion, considering that home-range/abundance relationships are widely documented in the lit- erature (Wiens 1973, Smith and Shugart 1987, Wunderle 1995, Haggerty 1998, Brown et al. 2()()0). Perhaps Henslow’s Sparrows have par- tially overlapping, non-defended home ranges during winter, since abundance relationships usually occur when species maintain exclusive territories. Other investigators of wintering Ammodmmus sparrows have observed a dis- tinctive pattern of use of space ifi these spe- cies (Gry/bowski 1983, Gordon 2()()0). Small, weak-flying species with cryptic coloraticui are often .solitary and evenly distributed across their habitat during winter (Pulliam afid Mills 1977, Gry/bowski 1983). Gry/bowski (1983) suggested that this behavior may iillovv soli- tary species to exjfioit areas with less abun- 222 THE WILSON BULLETIN • Vol. 1 17, No. 3, September 2005 dant seed resources. These species’ predator avoidance and resource acquisition strategies differ from those of gregarious, flocking spe- cies, which exhibit large-scale movements to exploit patches of resource-rich habitat (Grzy- bowski 1983, Gordon 2000). It has been suggested that wintering Hens- low’s Sparrows may not require the large ar- eas of grassland habitat essential to breeding populations (Herkert 1991, Burhans 2002). In lowland pitcher plant bogs. Tucker and Rob- inson (2003) found Henslow’s Sparrows win- tering in habitat patches as small as 0.06 ha. We did not test for the effects of area, but the differences in mean size of study sites among studies of wintering Henslow’s Sparrows may be revealing. Our study sites were consider- ably larger than the majority of sites in pre- vious studies (mean = 5.9 ha versus 0. 2-1.0 ha) and all of our study sites were located within a larger matrix of savanna that had been burned within the last several years. Whereas Tucker and Robinson (2003) found that abundance of wintering Henslow’s Spar- rows increased with area, density was not re- lated to bog area. This result could indicate that Henslow’s Sparrows will use suitable habitat patches of any size, or it could reflect the fact that the majority of patches examined were very small (only 2 of 47 sites were >1.0 ha). Further investigations of settlement pat- terns and individual home-range overlap could shed more light on winter area requirements. As in previous studies, we found that hab- itat characteristics varied across burn treat- ments and certain characteristics were corre- lated with relative abundance of Henslow’s Sparrows. Vegetation structure, dominant grass species composition, and seed abun- dance varied across burn treatments. Sites burned the previous growing season had lower vegetation density within 0.3 m of the ground and greater vegetation height than sites burned 1 or 2 years prior to the previous growing sea- son. Sites burned the previous growing season also had higher percent cover of Muhlenber- gia expansa and Ctenium aromaticum and higher seed abundance than sites burned 2 years prior to the previous growing season. Sites burned 1 year before sampling had the highest species diversity of dominant grasses. We were surprised that the amount of woody vegetation did not vary across burn treat- ments, but this could be a reflection of our site-selection criterion of minimal shrub cover. Seed abundance stood out as the best pre- dictor of Henslow’s Sparrow relative abun- dance. A high percent frequency of seeds was also one of the most important predictors of Henslow’s Sparrow occupancy of pitcher plant bogs along the Alabama/Florida border (Tucker and Robinson 2003). Similarly, on clearcut pine plantations in Alabama, one of the best predictors was the presence of Pani- cum verrucosum (Plentovich et al. 1999), a prolific seed producer that is common after soil disturbance. Like oihQY Ammodramus spe- cies, Henslow’s Sparrows probably rely most- ly on seeds for their winter diet (Grzybowski 1983; M. S. Woodrey unpubl. data), although which seed species play the most important role in winter diet is unknown. Preliminary data indicate that Muhlenbergia expansa, Di- chanthelium spp., Rhynchospora spp., and Eu- patohum spp. may be important elements in the winter diet of Henslow’s Sparrows (J. K. DiMiceli pers. comm.). Future studies should avoid overlooking inconspicuous species that could be important seed resources. For ex- ample, Rhynchospora spp. are a suite of spe- cies with diverse growth habits; some Rhyn- chospora produce tiny seeds and grow only a few centimeters tall. We observed these spe- cies forming a layer under taller grasses on some of our study sites, but did not include them in our measurements of species com- position or seed abundance. These prelimi- nary observations stress the importance of considering seed abundance and species com- position at a fine scale. After seed abundance, vegetation structure was the next most important predictor of Henslow’s Sparrow abundance. Sites with vegetation heights > 1 .0 m and low vegetation density <0.3 m consistently had the greatest numbers of wintering Henslow’s Sparrows. Carrie et al. (2002) also found that herbaceous cover and low vegetation density near the ground were important factors in discriminat- ing between occupied and unoccupied sites. Tall vegetation may impede detection by pred- ators, whereas low vegetation density near the ground may facilitate foraging movements for this weak-flying species. Our habitat association results are support- ed by previous studies, although direct com- Bechtoldt and Stauffer • WINTER ECOLOGY OE HENSLOW’S SPARROWS 223 parisons can be problematic. In two of the three previous studies, the second most im- portant predictor of Henslow’s Sparrow pres- ence was high vegetation density at or below 1.0 m (Plentovich et al. 1999, Tucker and Robinson 2003); in our study, Henslow’s Sparrow abundance was correlated with what is seemingly the exact opposite, low vegeta- tion density near the ground. This apparent contradiction could have two sources. First, the relative difference in vegetation structure among our study sites is probably lower than in previous studies. We studied eight sites, lo- cated within continuous savanna habitat and dominated by native herbaceous species; the majority of our study sites were occupied by Henslow’s Sparrows. Other studies examined a greater number of study sites representing a broader range of habitat structures and birds were absent from many of these sites. Second, the manner in which some studies quantified vegetation structure makes it difficult to sep- arate vegetation density from vegetation height. In those studies, vegetation density was measured as the number of 10-cm incre- ments where a certain type of vegetation was present (Plentovich et al. 1999, Tucker and Robinson 2003). Using this measure, sites with high vegetation density will also have taller vegetation, while not necessarily having high vegetation density near the ground. For example, on clearcut pine plantations (Plen- tovich et al. 1999) and lowland pitcher plant bogs (Tucker and Robinson 2003), Henslow’s Sparrow presence/abundance was correlated with high densities of herbaceous cover. These results may correspond to our conclusion that abundance is greater on sites with taller veg- etation, rather than contradict our vegetation density findings. Looking beyond these study- site and data-col lection differences, studies of wintering Henslow’s Sparrows seem to agree that tall vegetation, low vegetation density near the ground, and high seed abundance are positively correlated with presence or abun- dance of Henslow’s Sparrows (Plentovich el al. 1999, Carrie et al. 2002, fucker and Rob- inson 2003). Management implications. — fhe absence of a natural disturbance regime on the south- eastern Gulf Coastal Plain makes active man- agement essential to wintering populations of Henslow’s Sparrows. Habitat patches burned the previous growing season, with vegetation >1.0-m tall, low vegetation density near the ground, and high seed abundance had the greatest relative abundance of Henslow’s Sparrows across our study sites. Many her- baceous savanna species require a fire to flow- er, and species that follow fire often decrease in abundance as litter accumulates (Lemon 1949, Walker 1993). However, some herba- ceous species are good competitors in the presence of litter, only reaching significant densities a few seasons after a burn, and fire interval may be important in maintaining seed bank diversity (Lemon 1949, Hodgkins 1958). Litter accumulation is also important in gen- erating the high temperatures needed by some species to flower (Komarek 1965); burning too frequently can lead to a thin herbaceous layer, made up of a few fire-following species. Our relative abundance estimates demonstrate that a 10-ha area of savanna burned the pre- vious growing season will support about 25 sparrows. After 1 year, the number will drop to around 10 individuals. Two years after a fire, the habitat will support approximately 1 individual/10 ha. If remnants of longleaf pine savanna and other similar grassland habitats are to support significant numbers of winter- ing Henslow’s Sparrows, we recommend a bi- ennial, rotating burn schedule. Future studies examining landscape-scale fire regimes, win- ter settlement patterns, predation risk, and diet are essential and will lead to a further refine- ment of these management recommendations. ACKNOWLEDGMENTS Thanks to N. Mclnnis and L. M. Smith for permis- sion to work on The Nature Conservaney land, fund- ing, and access to their volunteer network. We appre- eiate the support and aceess to study sites provided tt) us hy M. Olinde. I). G. Krement/., B. S. Thateher, and M. S. Woodrey provided radio-transmitters and were instrumental in developing field methods. A. O. Cheek. G. Ferra/., I*. A. Keddy, and two anonymous reviewers added useful eomments on the text and G. B. Shaffer provided adviee oti data analysis. Graduate students of the Southeastern Louisiana University Department of Biologieal Seienees were essential metnbers of the vol- unteer data eolleetion team, espeeially L. M. Duda. .1. /.oiler, .1. A. Long. C. A. Bassett, and I). K. Brown. We would like to thank all the volunteers who helpetl band sparrows, ineluding L. Bailey. W. C’lifton. S. Bo- ehe. S. /iadeh. and K. Maekman and the students from Madison Central Nigh Sehool in Madis()ii. Mississippi. 224 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 LITERATURE CITED Askins, R. a. 1993. Population trends in grassland, shrubland, and forest birds in eastern North Amer- ica. Current Ornithology 11:1-34. Brown, D. R., P. C. Stouffer, and C. M. Strong. 2000. Movement and territoriality of wintering Hermit Thrushes in southeastern Louisiana. Wil- son Bulletin 112:347-353. Burhans, D. E. 2002. Conservation assessment — Henslow’s Sparrow Ammodramus henslowii. Gen- eral Technical Report NC-226, USDA Forest Ser- vice, North Central Research Station, St. Paul, Minnesota. Carrie, N. R., R. O. Wagner, K. R. Moore, J. C. Sparks, E. L. Keith, and C. A. Melder. 2002. Winter abundance of and habitat use by Henslow’s Sparrows in Louisiana. Wilson Bulletin 114:221- 226. Chandler, C. R. and M. S. Woodrey. 1995. Status of Henslow’s Sparrows during winter in coastal Mississippi. Mississippi Kite 25:20-24. Cully, J. F. and H. L. Michaels. 2000. Henslow’s Sparrow habitat associations on Kansas tallgrass prairie. Wilson Bulletin 112:115-123. Ecological Software Solutions. 2000. Location of a Signal (LOAS), ver. 2.04. Ecological Software Solutions, Sacramento, California. ESRI, Inc. 1999. ArcView GIS, ver. 3.2. Environmen- tal Systems Research Institute, Inc., Redlands, California. Frost, C. C. 1993. Four centuries of changing land- scape patterns in the longleaf pine ecosystem. Pages 17-43 in The longleaf pine ecosystem: ecology, restoration and management (S. M. Her- mann, Ed.). Tall Timbers Fire Ecology Conference Proceedings, no. 18. Tall Timbers Research Sta- tion, Tallahassee, Florida. Frost, C. C. 1998. Presettlement fire frequency re- gimes of the United States: a first approximation. Pages 70-81 in Fire in ecosystem management: shifting the paradigm from suppression to pre- scription (T. L. Pruden and L. A. Brennan, Eds.). Tall Timbers Fire Ecology Conference Proceed- ings, no. 20. Tall Timbers Research Station, Tal- lahassee, Florida. Frost, C. C., J. Walker, and R. K. Peet. 1986. Fire- dependent savannas and prairies of the Southeast: original extent, preservation status and manage- ment problems. Pages 348-357 in Wilderness and natural areas in the eastern United States: a man- agement challenge (D. L. Kulhavy and R. N. Con- nor, Eds.). Center for Allied Studies, School of Forestry, Stephen F. Austin State University, Nac- ogdoches, Texas. Gordon, C. E. 2000. Movement patterns of wintering grassland sparrows in Arizona. Auk 1 17:748-759. Grzybowski, j. a. 1983. Patterns of space use in grassland bird communities during winter. Wilson Bulletin 95:591-602. Haggerty, T. M. 1998. Vegetation structure of Bach- man’s Sparrow breeding habitat and its relation- ship to home-range. Journal of Field Ornithology 69:45-50. Herkert, j. R. 1991. An ecological study of the breed- ing birds of grassland habitats within Illinois. Ph.D. dissertation. University of Illinois, Urbana- Champaign. Herkert, J. R. 1994. Status and habitat selection of the Henslow’s Sparrow in Illinois. Wilson Bulletin 106:35-45. Herkert, J. R. 1997. Population trends of the Hens- low’s Sparrow in relation to the Conservation Re- serve Program in Illinois, 1975-1995. Journal of Field Ornithology 68:235-244. Herkert, J. R. 1998. Effects of management practices on grassland birds: Henslow’s Sparrow, ver. 17FEB2000. Northern Prairie Wildlife Research Center, Jamestown, North Dakota, www. npwrc. usgs.gov/resource/literatr/grasbird/hesp/hesp.htm (accessed 5 November 2002). Herkert, J. R. and W. D. Glass. 1999. Henslow’s Sparrow response to prescribed fire in an Illinois prairie fragment. Studies in Avian Biology 19: 160-164. Hodgkins, E. J. 1958. Effects of fire on undergrowth vegetation in upland southern pine forests. Ecol- ogy 39:36-46. Hooge, P. N. and B. Eichenlaub. 1997. Animal move- ment extension to Arc view, ver. 1.1. Alaska Sci- ence Center — Biological Science Office, U.S. Geological Survey, Anchorage, Alaska. Komarek, E. V. 1965. Fire ecology: grasslands and man. Pages 169-220 in Tall Timbers Fire Ecology Conference Proceedings, no. 4. Tall Timbers Re- search Station, Tallahassee, Florida. Lemon, P. C. 1949. Successional responses of herbs in the longleaf-slash pine forest after fire. Ecology 30:135-145. Noss, R. E, E. T. LaRoe, and J. M. Scott. 1995. En- dangered ecosystems of the United States: a pre- liminary assessment of loss and degradation. Re- port 0611-R-01. U.S. Department of the Interior, National Biological Service, Washington, D.C. Peet, R. K. and D. J. Allard. 1993. Longleaf pine vegetation of the southern Atlantic and eastern Gulf coast regions: a preliminary classification. Pages 45-81 in The longleaf pine ecosystem: ecology, restoration and management (S. M. Her- mann, Ed.). Tall Timbers Fire Ecology Conference Proceedings, no. 18. Tall Timbers Research Sta- tion, Tallahassee, Florida. Platt, W. J., G. W. Evans, and S. L. Rathburn. 1988. The population dynamics of a long-lived conifer {Pinus palustris). American Naturalist 131:491- 519. Plentovich, S. M., N. R. Holler, and G. E. Hill. 1998. Site fidelity of wintering Henslow’s Spar- rows. Journal of Field Ornithology 69:486-490. Plentovich, S. M., N. R. Holler, and G. E. Hill. 1999. Habitat requirements of Henslow’s Spar- Bechtoldt and Stoujfer • WINTER ECOLOGY OE HENSLOW’S SPARROWS 225 rows wintering in silvicultural lands of the Gulf Coastal Plain. Auk 116:109-115. Pruitt, L. 1996. Henslow’s Sparrow status assessment. U.S. Pish and Wildlife Service, Bloomington, In- diana. Pulliam, H. R. and G. S. Mills. 1977. The use of space by wintering sparrows. Ecology 58:1393- 1399. Rappole, J. H. and a. R. Tipton. 1991. New harness design for attachment of radio transmitters to small passerines. Journal of Pield Ornithology 62: 335-337. Sauer, J. R., J. E. Hines, and J. Fallon. 2004. The North American Breeding Bird Survey, results and analysis 1966-2002, ver. 2003.1. USGS Pa- tuxent Wildlife Research Center, Laurel, Mary- land. www.mbr-pwrc.usgs.gov/bbs/bbs.html (ac- cessed 14 October 2004). Smith, T. M. and H. H. Shugart. 1987. Territory size variation in the Ovenbird: the role of habitat struc- ture. Ecology 68:695-704. SoKAL, R. R. AND F. J. Rohlf. 1995. Biometry. W. H. Freeman and Company, New York. SPSS, Inc. 2000. SYSTAT, ver. 10. SPSS, Inc., Chi- cago, Illinois. Stout, I. J. and W. R. Marion. 1993. Pine flatwoods and xeric pine forests of the southern (lower) Coastal Plain. Pages 373-446 in Biodiversity of the southeastern United States: lowland terrestrial communities (W. H. Martin, S. G. Boyce, and A. C. Echternacht, Eds.). John Wiley and Sons, New York. SwENGEL, S. R. 1996. Management responses of three species of declining sparrows in tallgrass prairie. Bird Conservation International 6:241-253. Thatcher, B. S. 2003. Impacts of prescribed burns on Henslow’s Sparrow winter home-range and sur- vival in coastal pine savanna habitats. M.Sc. the- sis, University of Arkansas, Fayetteville. Tucker, J. W. and W. D. Robinson. 2003. Influence of season and frequency of fire on Henslow’s Sparrows (Ammodramus henslowii) wintering on Gulf Coast pitcher plant bogs. Auk 120:96-106. Walker, J. 1993. Rare vascular plant taxa associated with the longleaf pine ecosystems: patterns in tax- onomy and ecology. Pages 105-1 15 in The long- leaf pine ecosystem: ecology, restoration and management (S. M. Hermann, Ed.). Tall Timbers Fire Ecology Conference Proceedings, no. 18. Tall Timbers Research Station, Tallahassee, Florida. Ware, S., C. Frost, and P. D. Doerr. 1993. Southern mixed hardwood forest: the former longleaf pine forest. Pages 447-493 in Biodiversity of the southeastern United States: lowland terrestrial communities (W. H. Martin, S. G. Boyce, and A. C. Echternacht, Eds.). John Wiley and Sons, New York. Wiens, J. A. 1973. Interterritorial habitat variation in Grasshopper and Savannah sparrows. Ecology 54: 877-884. WuNDERLE, J. M., Jr. 1995. Population characteristics of Black-throated Blue Warblers wintering in three sites on Puerto Rico. Auk 112:931-946. Zimmerman, J. L. 1988. Breeding season habitat se- lection by the Henslow’s Sparrow {Ammodramus henslowii) in Kansas. Wilson Bulletin 100:17-24. Wilson Bulletin 1 17(3):226— 236, 2005 SPACING AND PHYSICAL HABITAT SELECTION PATTERNS OE PEREGRINE EALCONS IN CENTRAL WEST GREENLAND CATHERINE S. WIGHTMAN' AND MARK R. FULLERS ABSTRACT. — We examined nest-site spacing and selection of nesting cliffs by Peregrine Falcons (Falco peregrinus) in central West Greenland. Our sample included 67 nesting cliffs that were occupied at least once between 1972 and 1999 and 38 cliffs with no known history of Peregrine Falcon occupancy. We measured 29 eyrie, cliff, and topographical features at each occupied nesting cliff and unused cliff in 1998-1999 and used them to model the probability of peregrines occupying a cliff for a breeding attempt. Nearest-neighbor distance was significantly greater than both nearest-cliff distance and nearest-occupied distance (the distance between an occupied cliff and one occupied at least once, 1972-1999). Thus, spacing among occupied cliffs was probably the most important factor limiting nesting-cliff availability, and, ultimately, peregrine nesting densities. Although some unused cliffs were unavailable in a given year because of peregrine spacing behavior, physical character- istics apparently made some cliffs unsuitable, regardless of availability. We confirmed the importance of several features common to descriptions of peregrine nesting habitat and found that peregrines occupied tall nesting cliffs with open views. They chose nesting cliffs with eyrie ledges that provided a moderate degree of overhang protection and that were inaccessible to ground predators. Overall, we concluded that certain features of a cliff were important in determining its suitability as a nest site, but within a given breeding season there also must be sufficient spacing between neighboring falcon pairs. Our habitat model and information on spacing require- ments may be applicable to other areas of Greenland and the Arctic, and can be used to test the generalities about features of Peregrine Falcon nesting cliffs throughout the species’ widespread distribution. Received 31 March 2004, accepted 18 March 2005. Habitat selection is the process by which an animal chooses suitable habitats (Manly et al. 1993, Litvaitis et al. 1994), and can be mea- sured when an animal uses a resource dispro- portionately to its availability (Johnson 1980). Features of the habitat that are important for occupancy can function as meaningful indi- cators of habitat selection, even when the amount of available habitat is unknown (Man- ly et al. 1993). Historically, many researchers have studied Peregrine Falcons {Falco pere- grinus-, hereafter peregrine) in conjunction with the decline of populations caused by DDT in the mid- 1900s (Cade et al. 1988), and there have been many descriptions of pere- grine nesting habitat (e.g.. White and Cade 1971, Court et al. 1987, Emison et al. 1997). However, there have been only two studies in ' Raptor Research Center and Dept, of Biology, 1910 University Dr., Boise State Univ., Boise, ID 83725, USA. 2 USGS Forest and Rangeland Ecosystem Science Center, Snake River Field Station and Raptor Research Center, Boise State Univ., 970 Lusk St., Boise, ID 83706, USA. ^ Current address; Arizona Game and Fish Dept., Research Branch, 2221 W. Greenway Rd., Phoenix, AZ 85023, USA. "^Corresponding author; e-mail: cwightman@azgfd. gov which there were quantitative tests of habitat features that influence habitat selection, and both studies occurred in temperate regions (Grebence and White 1989, Gainzarain et al. 2000). There are no such quantitative data for arctic environments, and there is little infor- mation on habitat characteristics that appear to be universal across the species’ extensive distribution. Although Peregrine Falcons are described as intolerant of nesting pairs nearby (Cade 1960, Ratcliffe 1993), there have been no tests to evaluate the importance of spacing between suitable nesting cliffs or nearest neighbors. Gainzarain et al. (2000) calculated an average distance between nesting cliffs oc- cupied by Peregrine Falcons, but this permit- ted only a general prediction of habitat use and was not a reflection of actual spacing. Availability of a nesting cliff may depend on the distribution of occupied nesting cliffs, which may vary among years (Ratcliffe 1993). The two most important factors limiting raptor densities are the availability of physical nesting habitat or food, whichever is in shorter supply (Hickey 1942, Newton 1979). Newton (1998) suggested that nest-site availability can be limiting for species with specialized nest- ing-cliff requirements. Because peregrines 226 Wightman and Fuller • PEREGRINE HABITAT SELECTION IN GREENLAND 227 prey opportunistically on many different bird species, the population trend of any one spe- cies usually does not affect peregrine breeding densities (Hickey 1942). In central West Greenland, most of the falcon’s diet comprises four passerine species (Rosenfield et al. 1995); within 400 m of peregrine eyries, densities of these species are reduced, but they are abun- dant 400 to 3,000 m from the eyrie and at random locations on the study area tundra (Meese and Fuller 1989). Although peregrines may hunt regularly within 1,500 m of nesting cliffs (Tucker et al. 2000), some may travel 20-43 km on hunting flights (Enderson and Craig 1997). Newton (1998) suggested that food availability near nests is not important to species that forage elsewhere. Thus, nesting- cliff availability may be a more important lim- iting factor than local prey availability. Be- cause of our limited knowledge of peregrine breeding biology in the Arctic and the impor- tance of nesting-cliff availability, we investi- gated habitat selection and spacing as poten- tial factors limiting peregrine nesting densi- ties. The migratory arctic Peregrine Falcon (Tundra Peregrine Falcon, F. p. tundrius) breeds in regions of Canada, Alaska, and the ice-free portion of Greenland (Cade et al. 1988, White et al. 2002). Since 1972, partic- ipants in the Greenland Peregrine Falcon Sur- vey (GPFS) have routinely surveyed for breeding arctic peregrines in central West Greenland (Mattox and Seegar 1988). On the initial search, GPFS surveyors found only nine pairs of peregrines occupying cliffs. By 1999, there were 133 known peregrine nesting clilfs in the study area (W. G. Mattox unpubl. data). The 28 years of data collected on this population made it ideal for studying relation- ships between nesting-cliff occupancy, spac- ing, and physical habitat characteristics. Our objectives were (1) to determine whether availability of nesting cliffs was limited, (2) to evaluate whether unused cliffs were un- suitable or unavailable for occupancy because ol peregrine spacing recjuiremeiits, and (3) to determine which habitat characteristics may be important for peregrine nesting-cliff selec- tion. Mi:rn()i)s Study area. — We coiuluctetl our study in the Kangerlussuaci region of central West Green- land, which encompasses one of the widest portions of ice-free land on the island. The study area, delineated by W. G. Mattox and colleagues in 1972, is approximately 2,500 km^ in area and lies between 66° 45' N and 67° 15' N (Mattox and Seegar 1988). Spndre Strpmfjord — the longest fjord in West Green- land— divides the area, which extends approx- imately 100 km from the inland ice cap almost to the western coast. Elevations range from sea level to 1,120 m, and summer tempera- tures usually range between 0 and 15° C. Eo- cated in a belt of short, arctic vegetation, the landscape is dominated by willow scrub (Salix glauca), dwarf birch (Betula nana), lichens, mosses, sedges, and grasses (Bocher et al. 1968) interspersed with many ponds and lakes. Definitions. — We defined an eyrie as the place on a ledge where a falcon lays her eggs (Ratcliffe 1993). We used the term nesting cliff to define a topographic feature containing one or more eyries or potential eyries, but oc- cupied by only one pair of peregrines in a giv- en year. Alternative nesting cliffs may occur within the range of one mated pair of birds. Rock faces and knolls were typically discrete topographic features in our study area and there was little continuous cliff habitat; thus, nesting cliffs were discrete features and did not overlap. Availahility is the presence and accessibility of the habitat, or habitat feature, and is generally subject to the biological and social constraints of that species, which in- cludes intra- and interspecific competition (Johnson 1980). Gyrfalcons {F. rusticolus) and Common Ravens {Corvus corax: hereafter ravens) were the only other common cliff- nesting species and only potential nest-site competitors. Gyrfalcons and ravens occupied nesting cliffs prior to the arrival of peregrines in the spring (W. G. Mattox pers. comm.), possibly influencing peregrine selection of nesting cliffs. Occupancy of nesting cliffs by Gyrfalcons varied widely among years and nesting cliffs (W. G. Mattox unpubl. data). In any year, Gyrtalcons and ravens combined oc- cupied up to H7r of peregrine nesting cliffs and peregrines nested on up to 339f of nesting cliffs already occupied by either of these two species (W. (i. Mattox unpubl. data), 'fhere- fore, the potential lor interspecilic competition lor nesting cliffs was relatively low, and we 228 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 assumed that all nesting cliffs were available to peregrines at some time between 1972 and 1999. We classified a nesting cliff as occupied if we or other GPFS members observed a pair of peregrines at the nesting cliff during the breeding season (June-August) in any year from 1972 to 1999. The majority of these oc- cupancies represented egg-laying attempts, but in a few cases adult pairs occupied nesting cliffs for several seasons without producing eggs (W. G. Mattox unpubl. data). We defined an unused cliff as any cliff where there was no known history or evidence of occupancy from 1972 to 1999. We considered only un- used cliffs that had at least 14 m of vertical rock face because the shortest occupied cliff in the study area was 14 m in height. Our sample consisted of 105 cliffs; 67 were oc- cupied and 38 were unused. Habitat measures. — In the summers of 1998 and 1999, we measured nesting-cliff characteristics. Due to logistical constraints, we could not completely randomize our sam- ple of nesting cliffs, but we measured all oc- cupied and unused nesting cliffs encountered along or near portions of six survey routes established by the GPFS. Our sample of 105 cliffs constitutes approximately 50% of known cliffs in the study area, and the pro- portion of occupied to unused cliffs was likely representative of the total study area. Thus, despite a non-random sample, our estimate of nesting-cliff selection is meaningful, even when the standard error of features may not reflect the true variation in the total population of cliffs (Manly et al. 1993). For a complete description of GPFS survey methods, see Burnham and Mattox (1984). We measured three features of nesting-cliff distribution by plotting all cliffs on a topo- graphic map and measuring the linear distance between cliffs. The nearest cliff was the cliff closest to the sample cliff {n = 67 occupied, A7 = 38 unused), whether or not peregrines had ever occupied it. The nearest occupied cliff was the nearest nesting cliff occupied by per- egrines at any time between 1972 and 1999. We measured the distance to the nearest cliff and the nearest occupied cliff from occupied and unused cliffs. We defined the third spatial measure, distance to nearest neighbor, as the distance to the nearest nesting cliff occupied by peregrines in the same breeding season as the sampled nesting cliff. Because unused cliffs cannot have neighbors, we recorded this measure for occupied sites only. If the nearest- neighbor distance for a given nesting cliff var- ied among years, then we used the shortest distance recorded between 1972 and 1999. We measured physical features of nesting cliffs at the three spatial levels: eyrie ledge, cliff, and surrounding topography. We mea- sured 26 characteristics in addition to the three spacing features (Appendix) based on results from previous studies. A team of at least two persons hiked to cliffs and climbed to eyries and unused ledges to measure and record data. At occupied nesting cliffs, we measured the eyrie ledge used most recently. At unused nesting cliffs, we selected one ledge as a pu- tative eyrie to measure. All measured ledges at unused nesting cliffs were flat (—0° slope) and at least large enough to accommodate a scrape for eggs. Although our selection of un- used ledges was subjective, we attempted to select the ledge that provided the best com- bination of protection from predators and hu- mans (Mearns and Newton 1988) and micro- climatic benefits (Falk et al. 1986). Analyses. — Because data deviated from nor- mality, we used a nonparametric Wilcoxon matched-pairs signed rank test to compare among measures of spatial distribution for each occupied nesting cliff (Zar 1996). Com- parisons between nearest-neighbor and near- est-cliff distances, and between nearest-neigh- bor and nearest-occupied cliff distances were not independent of one another, so we used a Bonferroni adjusted alpha of 0.025 to control for inflated type I errors. To test for nonrandom orientation, we con- ducted Rayleigh’s test of circular uniformity on aspect data for occupied and unused nest- ing cliffs (Zar 1996). Parametric tests for cir- cular data assume the data are from a von Mises distribution, which is the circular equiv- alent to a normal distribution. As our data did not always meet the assumption for a para- metric test, we used a nonparametric proce- dure for unimodal data that compared the mean direction of occupied and unused nest- ing cliffs against a chi-square distribution (Fisher 1993:116, Method P). This nonpara- metric procedure allowed us to evaluate whether or not cliff and eyrie ledge aspect Wightman and Fuller • PEREGRINE HABITAT SELECTION IN GREENLAND 229 were important in peregrine nesting-cliff se- lection. We used logistic regression to predict the probability of occupancy according to habitat features. Three habitat features — nearest- neighbor distance and cliff and ledge aspect — were not included in our logistic regression analysis because we could not calculate a val- ue for unused cliffs (nearest neighbor) or the data were circular (aspect data) and could not be used appropriately in a linear analysis. Col- linearity of predictor variables in linear or lo- gistic regression can cause unexpected regres- sion coefficients or large standard errors; thus, it was necessary to delete one or more inter- correlated variables before conducting our analysis (Hosmer and Lemeshow 1989, Zar 1996). We retained only one of a pair of cor- related variables (r > 0.60) that were easier to measure or that have been shown to be im- portant features of peregrine nesting-cliff hab- itat elsewhere. We also eliminated one vari- able (slope) that we were unable to measure at all nesting cliffs. We eliminated 8 of 26 variables (eyrie height, cliff height at eyrie, elevation of cliff above the drainage, nearest cliff, elevation of cliff, length of ledge, over- hang categories, and slope), retaining 18 for analysis. With the 1 8 retained variables, we used the best subsets variable-selection technique to determine which variables to include in a lo- gistic regression analysis and chose the com- bination of habitat variables that produced the best C(p) Mallow statistic (Hosmer and Lemeshow 1989). This technique provided all possible pairings among habitat variables and identified which combinations of variables provided the best fit to the data. We tested for the importance of interactions between certain habitat features in this variable selection step. Then, we used the combination of habitat var- iables identified as providing the best fit to the data in a logistic regression to predict the probability of occupancy (Hosmer and Lemeshow 1989, Allison 1999). We modeled the probability ol each cliff being assigned to an occupied nesting cliff ( 1 ) as opposed to an unused cliff (0) based on habitat features. We evaluated the fit and the predictive power of the logistic regression model using the Hos- mer-Lemeshow goodness-of-fit test (G) and the max-rescaled r-square value, respectively. We used SAS software (SAS Institute, Inc. 1990) to conduct analyses and assigned a sig- nificance level of alpha equal to 0.05. RESULTS The nearest-neighbor distance of 67 occu- pied sites was significantly greater than its paired, nearest-cliff distance (Too5(2>,67 = 333, n = 67, P < 0.001). Nearest-neighbor distance was also significantly greater than its paired, nearest-occupied cliff distance (T^ 05(2) 6? 52, n = 67, P < 0.001). We measured circular, linear, and categori- cal (Tables 1 and 2) habitat features at nesting cliffs that were occupied {n = 67) and unused {n = 38). Cliff aspect at occupied and unused nesting cliffs (Zoo5,6? = 26.25, P < 0.001; ^0.05,38 = 12.67, P < 0.001, respectively) and on eyrie ledges or unused ledges (Z00559 = 18.66, P < 0.001; Zqo5,34 = 10.24, P < 0.001, respectively) was significantly oriented to the south. Mean orientation did not differ between occupied and unused cliffs (x^ = 0.07, n = 105, P = 0.79) or between used or unused ledges (x^ = 0.28, n = 93, P = 0.60). The best subset variable-reduction tech- nique identified five variables important in modeling nesting-cliff occupancy by pere- grines (Table 3) and the slope of the logistic regression line was significantly different from zero (G5 = 38.52, n = 76, P < 0.001). Our logistic regression model was effective for describing occupied sites (C« = 5.91, P = 0.66) and had moderate predictive power (re- scaled = 0.54). The adjusted odds ratio for each variable in the model indicates the effect of each variable on the probability of occu- pancy at a cliff. An odds ratio of 0.967 for vertical angle of exposure indicated that there is a 3.3% increase in odds of occupancy with every 1 -degree decrease in exposure. Odds of occupancy increased by 89.3% if ledges were inaccessible to predators and by 96.7% if the ledge substrate was sand or dirt, rather than a slick nest. E'or every 1 m increase in cliff height and 1 m decrease in elevation of hill across valley, odds of occupancy increased by anti 0.7%, respectively. DISCTJSSION Spacing among occupied nesting cliffs was an important component of cliff occupancy in oiir slutly. Our results suggest that some near- 230 THE WILSON BULLETIN • Vol. 1 17, No. 3, September 2005 TABLE 1. Physical characteristics of 67 occupied and 38 unused cliffs measured to evaluate Peregrine Falcon nesting-cliff selection in central West Greenland. Measurements were made in 1998-1999; cliffs were categorized as occupied or unused based on their occupancy history from 1972 to 1999.“ Occupied Unused Phy.sical feature.s Mear 1 ± SE Range Mean 1 ± SE Range Eyrie characteristics Length of eyrie ledge (cm) 57 686.2 -1- 152 50-6,089 28 234.7 31.0 52-600 Depth of eyrie ledge (cm) 57 164.7 -f- 32.7 17-1,500 28 105.4 ± 1 1.3 21-274 Eyrie aspect (°) 67 188.7 -1- 0.9 15-345 34 195.1 -E 81.5 65-292 Horizontal angle of expo- sure (°) 49 144.4 -1- 4.8 54-205 30 144.9 8.4 65-236 Vertical angle of exposure o 48 65.2 2.8 25-1 10 29 84.0 -E 6.4 20-150 Cliff characteristics Elevation of cliff (m) 67 288.0 + 14.1 100-550 38 265.1 -E 20.1 75-550 Cliff height (m) 67 98.8 -h 8.0 14-365 38 61.0 -E 5.3 14-147 Height of hill below cliff (m) 67 39.8 H- 4.1 0-138 38 53.3 -E 7.7 0-198 Slope (m) 57 1.70 -H 0.11 0.71-5.08 32 1.34 -E 0.16 0.09-5.19 Cliff aspect (°) 67 187.7 -h 0.8 21-360 38 190.5 -E 1.3 20-330 Height of eyrie ledge (m) 65 51.1 -1- 5.4 5-224 35 24.8 3.2 7-78 Cliff height at eyrie ledge 65 94.3 -h 8.2 14-365 35 52.2 -E 5.7 14-154 (m) Topographical characteristics Distance to permanent wa- ter (m) 67 452.7 55.4 0-2,750 38 561.3 + 81.9 0-2,500 Elevation gain within 3-km radius (m) 67 205.2 H- 11.3 50-475 38 179.6 -E 14.4 25-500 Elevation of cliff above drainage (m) 67 161.4 -h 10.8 26-450 38 130.9 + 11.5 25-300 Distance to drainage (m) 67 577.9 ± 72.4 0-2,250 38 643.8 -E 84.1 0-2,000 Elevation of hill across val- ley (m) 67 348.6 -h 14.0 125-600 38 399.4 -E 26.9 125-750 Distance to hill across val- ley (km) 67 2.19 -H 0.14 0.3-5.0 38 2.6 -E 0.2 0.5-6.5 Distance to nearest cliff (km) 67 2.16 -h 0.14 0.2-5.0 38 1.4 -E 0.1 0.2-3.3 Distance to nearest occu- pied cliff (km) 67 2.69 -H 0.13 0.3-5. 1 38 2.1 -E 0.2 0.2-5.0 Distance to nearest neigh- bor (km) 67 3.27 -E 0.18 1.3-11.2 N/A See Appendix for definition of habitat features. At a few nesting cliffs and unused cliffs, we were unable to access or could not identify the eyrie or unused ledge. Thus, our sample size for eyrie characteristics or location varies from 67 occupied nesting cliffs and 38 unused cliffs. We also could not calculate slope of cliff if we could not measure accurately the distance from the observer to the top of the cliff. est nesting cliffs, occupied at least once and, thus, suitable, are not available in some years due to their proximity to a site already occu- pied by peregrines. Therefore, availability of a particular nest site may vary among years depending on the current distribution of oc- cupied nesting cliffs. Dispersion among ani- mal-use areas can result from a variety of causes, including competition for food or nest- ing resources (Fretwell and Lucas 1969, New- ton 1998). Intraspecific aggression of pere- grines has been noted at nest sites (Ratcliffe 1993, White et al. 2002), and spacing require- ments may be a mechanism for reducing the costs associated with agonistic behavior. Unused nesting cliffs also may not be avail- able in every year because of peregrine spac- ing requirements. However, we can assume that unused cliffs were available for occupan- cy at some time between 1972 and 1999 be- Wightman and Fuller • PEREGRINE HABITAT SELECTION IN GREENLAND 231 TABLE 2. Categorical habitat features measured at 67 occupied nesting cliffs and 38 cliffs unused by Peregrine Ealcons to evaluate habitat selection in central West Greenland. Measurements were made in 1998- 1999; cliffs were categorized as occupied or unused based on their occupancy history from 1972 to 1999.^ Physical features Occupied*’ % Unused*’ % Ledge characteristics Overhang protection on ledge None 6 11% 15 47% Slight 10 18% 6 19% Partial 29 54% 5 16% Complete 9 17% 6 19% Accessible to predation Yes 16 28% 15 47% No 42 72% 17 53% Substrate at or near scrape Sand or dirt 44 81% 1 1 38% Moss 0 0% 3 10% Vegetation 6 11% 9 31% Gravel 1 2% 2 7% Stick nest 2 4% 4 14% Bare rock 1 2% 0 0% Vegetation on ledge Yes 42 74% 22 65% No 15 26% 12 35% Cliff characteristics Vegetation at base of cliff Willow-steppe mix 21 33% 18 47% Heath-willow mix 18 28% 14 37% Heath-steppe mix 8 13% 3 8% Herbslope 5 8% 0 0% Water 4 6% 1 3% Willow copse 8 13% 2 5% Boulders at base of cliff Yes 57 89% 25 66% No 7 1 1% 13 34% Position of ledge on cliff Lower 15 24% 9 20% Middle 30 48% 31 69% Upper 18 29% 5 1 1% Human disturbance Minimal 57 85% 33 87% Moderate 9 13% 5 13% Severe 1 1% 0 0% “ See Appendix for definition of terms. At a tew nesting cliffs and unused cliffs, we were unable to access or could not identify the eyrie or unused ledge. Thus, our sample si/e for eyrie characteristics or placement varies from 67 (Kcupied nesting cliffs and .18 unused cliffs. cause no nesting cliff was occupied in each of the last 28 years (peregrines occupied nesting clitts 20-96% of years checked after the nest- ing clitt was located), and breeding pairs moved up to 3.5 km among years to alterna- tive nesting clitts (W. CL Mattox unpubl. data). Spacing ot clifts was also not important in our logistic regression model predicting nesting-cliff occupancy, riuis. some unused nesting cliffs are probably unsuitable regard- less of their availability becau.se they do not contain features imiiortant for peregrine nest- ing. The eyrie ledge features that we identitied 232 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 TABLE 3. Peregrine Falcons in central West Greenland selected tall nesting cliffs with prominent views and eyrie ledges that provided protection from weather and predators. Our logistic regression model predicts the probability of a cliff being occupied by peregrines using habitat features measured at 48 occupied nesting cliffs (1) and 28 unused cliffs (0). Negative coefficients (P) indicate a negative association between that variable and cliff occupancy. Habitat variables included in our model were selected using the best subset variable-selection technique. Measurements were made in 1998-1999; cliffs were categorized as occupied or unused based on their occupancy history from 1972 to 1999.^ Variable^ P SE Wald df pc exp(p)d 95% Wald CL Intercept 5.715 1.808 9.99 1 0.002 _ Vertical angle of exposure -0.034 0.015 5.37 1 0.020 0.967 0.939 0.995 Accessibility of ledge -2.239 0.765 8.56 1 0.003 0.107 0.024 0.478 Stick nest on ledge -3.413 1.231 7.68 1 0.006 0.033 0.003 0.368 Cliff height 0.017 0.007 5.56 1 0.020 1.017 1.003 1.032 Elevation of hill across valley -0.008 0.003 8.13 1 0.004 0.992 0.987 0.998 We were unable to measure all eyrie and ledge characteristics at all cliffs because of accessibility problems. Our sample for the logistic regression model is lower than our complete sample of 67 occupied nesting cliffs and 38 unused cliffs because it includes only those cliffs where all five habitat variables were measured. See Appendix for definition of terms. P-values based on Wald statistic. Odds ratios indicate the change in odds of occupancy for each unit change of the variable. For example, the odds ratio for elevation of hill across the valley is 0.992. This means that for each 1 m decrease in elevation the odds of occupancy increase by 0.8%. Accessibility of ledge and stick nest on ledge are binary variables; thus, the odds ratios reflect 89.3% and 96.7% increases in odds of occupancy, respectively, if the ledges are not accessible (by foxes or humans) or there is not a stick nest on the ledge. as being important in nesting-cliff occupancy suggest that peregrines choose nesting sites with ledges that provide microclimatic bene- fits and protection from predators. Eyrie ledg- es that afford protection from weather are as- sociated with occupancy by peregrines throughout North America (Cade 1960, Falk et al. 1986, Court et al. 1988). Bradley et al. (1997) found that mean clutch size of pere- grines in subarctic Canada decreased with greater precipitation and that nestling mortal- ity increased with annual precipitation during storms. This suggests that microclimate of the eyrie, influenced by vertical protection of the overhang above the ledge, may be an impor- tant feature in nesting-cliff occupancy by per- egrines. Approximately one-third of peregrine ey- ries in Great Britain were on raven stick nests (Ratcliffe 1993) and, in Alaska, 20% nested on Rough-legged Hawk (Buteo lagopus) stick nests (Cade 1960). Thus, stick nests can pro- vide a suitable substrate for peregrine eyries. Ravens in our study area began nesting in ear- ly May and tended to build their stick nests under rock overhangs that completely shaded the ledge (CSW pers. obs.). The negative as- sociation we found between nesting-cliff oc- cupancy and stick nests may represent selec- tion for moderate, rather than complete, over- hang protection on the ledge. Moderate over- hang protection would provide some protection from weather, but also allow pere- grines to receive warmth from the arctic sun. Most cliffs were oriented to the south and therefore were positioned to take advantage of solar insolation. Our results support those of Burnham and Mattox (1984), who suggested that peregrines in central West Greenland choose eyrie ledges that balance solar exploi- tation and protection from weather. Peregrine nesting cliffs in several regions of the world are associated with tall, dominant cliffs that provide a commanding outlook (Hickey 1942, Grebence and White 1989, Gainzarain et al. 2000). Jenkins and Hockey (2001) proposed a latitudinal gradient in cliff height, suggesting that peregrines occupied low cliffs in arctic regions (mean cliff height <10 m at 65° latitude). Our data, however, indicate that peregrines will choose tall cliffs with commanding views, if available, in arctic areas, as well. Tall cliffs and open views ap- parently benefit peregrines by providing better perches for hunting or defense from intruders (Meams and Newton 1988, Ratcliffe 1993, Jenkins 2000). Jenkins (2000) documented greater hunting success from perches at nest- ing cliffs than from aerial hunts, and he found a positive relationship between hunting suc- cess and tall cliffs. However, in our study area the primary prey of peregrines were ground Wightman and Fuller • PEREGRINE HABITAT SELECTION IN GREENLAND 233 nesting and foraging passerines (Rosenfield et al. 1995), which suggests that the contour- hugging, surprise attack behavior described by White and Nelson (1991) may be a more ef- fective strategy for capturing prey than aerial attacks from cliffs. Thus, the benefits of de- fense from conspecifics and predators (e.g., arctic fox, Alopex lagopus), rather than en- hanced foraging opportunities provided by tall nesting cliffs with commanding views, are probably more influential in nesting-cliff se- lection. We conclude that competition plays an important role in nesting-cliff suitability, as well as availability. We identified features that were limited in availability but important for nesting-cliff se- lection by peregrines. However, certain fea- tures important in habitat selection may be abundant in our study area and, therefore, our methods may not have allowed us to identify these features. For instance. Cade (1960), Ellis (1982), and Court et al. (1988) found that per- egrine nesting cliffs often were close to water. Surface water provides a place for peregrines to bathe and good habitat for some of their prey (Cade 1960). However, we found no as- sociation between occupied nesting cliffs and distance to water. There is an abundance of small lakes and streams in our study area, so water is generally found close to all cliffs (mean = 492.0 m ± 46.2 SE, range = 0- 2,750 m). Of the many habitat features we measured, we found five that characterized occupancy by peregrines. Nesting cliffs may be suitable to peregrines by meeting just a few critical spa- tial and habitat requirements. This adaptability in nest-site selection may contribute to the worldwide distribution of peregrines. Spacing, and thus availability, of suitable breeding sites is probably the most important proximate fac- tor limiting the nesting densities of peregrines in our study area. Characteristics of the nest- ing cliff are important for determining the suitability of a nesting cliff if there is suffi- cient space between neighbors to accommo- date a breeding attempt in a given year. Our results suggest that peregrines select tall nest- ing cliffs with commanding views and pro- tected ledges for nest-defense and microcli- matic benefits, 'fhe similarities of nestiFig-cliff features at occupied peregrine nesting cliffs among geographic regions suggest that our predictive model of nesting-cliff occupancy — using physical characteristics and peregrine spacing requirements — could be applicable to other areas of Greenland and the Arctic. ACKNOWLEDGMENTS We are indebted to G. E. Doney for his exceptional assistance with fieldwork and logistics. We thank W G. Mattox for sharing his extensive data and intimate knowledge of the study area, and for providing guid- ance for this research. The Raptor Research Center and the Department of Biology at Boise State University, the Conservation Research Foundation, and the De- partment of Defense provided funding for this project. W S. Seegar was instrumental in arranging support and conducting fieldwork for the Greenland Peregrine Falcon Survey. The Peregrine Fund, Inc., the Conser- vation Research Foundation, and T Maechtle provided logistical support and permits. J. Belthoff, J. Munger, and L. Bond provided statistical advice. R. Rosenfield, T. Booms, and other Greenland Peregrine Falcon Sur- vey members assisted with data collection. T. J. Cade, C. M. White, and one anonymous reviewer provided valuable comments that improved this manuscript. LITERATURE CITED Allison, P. D. 1999. Logistic regression using the SAS system: theory and application. SAS Institute, Inc., Cary, North Carolina. Bocher, T. W, K. Holmen, and K. Jakobsen. 1968. The flora of Greenland. P. Haase & Son, Copen- hagen, Denmark. Bradley, M., R. Johnstone, G. Court, and T. Dun- can. 1997. Influence of weather on breeding suc- cess of peregrines in the Arctic. Auk 114:786- 691. Burnham, W. A. and W. G. Mattox. 1984. Biology of the peregrine and Gyrfalcon in Greenland. Meddelelser om Grpnland, Bioscience 14:1-28. Cade, T. J. I960. Ecology of the peregrine and Gyr- falcon populations in Alaska. University of Cali- fornia Publications in Zoology 63:151-290. Cade, T. J., J. E. Ender.son, C. G. Thelander, ani:) C. M. White. 1988. Peregrine Falcon populations: their management and recovery. The Peregrine Fund, Boi.se, Idaho. CouRi, G. S., D. M. Bradi.ey. C. C. Gates, and D. A. Boao. 1988. Turnover and recruitment in a tun- dra population of peregrines Falco peregrinus. Ibis 131:487-496. Court, G. S., C. C. Gates, and D. A. Boao. 1987. Natural history of the Peregrine Falcon in the Keewatin District of the Northwest Territories. Arctic 41:17-30. F.li.is. D. II. 1982. file IVregrine falcon in Arizona: habitat utilization and management recommenda- tions. Institute for Raptor Stuilies Research Re- ports, no. 1. Oraele. Arizona. Faiison. W. B.. C'. M. Whui . V. G. Huki.f y. anf) D. 234 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 J. Brimm. 1997. Factors influencing the breeding distribution of the Peregrine Falcon in Victoria, Australia. Wildlife Research 24:433-444. Enderson, J. E. and G. R. Craig. 1997. Wide ranging by nesting Peregrine Falcons {Falco peregrinus) determined by radiotelemetry. Journal of Raptor Research 31:333-338. Falk, K., S. M0ller, and W. A. Burnham. 1986. The Peregrine Falcon Falco peregrinus in South Greenland: nesting requirements, phenology and prey selection. Dansk Ornitologisk Forenings Tidsskrifter 80:113-120. Fisher, N. I. 1993. Statistical analysis of circular data. Cambridge University Press, Cambridge, United Kingdom. Fretwell, S. D. and H. L. Lucas. 1969. On territorial behavior and other factors influencing habitat dis- tribution in birds. Acta Biotheoretica 19:16-36. Gainzarain, j. a., a. Arambarri, and A. R. Rodri- quez. 2000. Breeding density, habitat selection and reproductive rates of the Peregrine Falcon {Falco peregrinus) in Alava (northern Spain). Bird Study 47:225-231. Grebence, B. L. and C. M. White. 1989. Physio- graphic characteristics of Peregrine Falcon nesting habitat along the Colorado River system in Utah. Great Basin Naturalist 49:408-418. Hickey, J. J. 1942. Eastern population of the Duck Hawk. Auk 59:176-204. Hosmer, D. W. and S. Lemeshow. 1989. Applied lo- gistic regression. John Wiley and Sons, New York. Jenkins, A. R. 2000. Hunting mode and success of African peregrines Falco peregrinus minor: does nesting habitat quality affect foraging efficiency? Ibis 142:235-246. Jenkins, A. R. and P. A. R. Hockey. 2001. Prey avail- ability influences habitat tolerance: an explanation for the rarity of Peregrine Falcons in the tropics. Fcography 24:359-367. Johnson, D. H. 1980. The comparison of usage and availability measurements for evaluating resource preference. Ecology 61:65-71. Litvaitis, j. a., K. Titus, and E. M. Anderson. 1994. Measuring vertebrate use of terrestrial habitats and foods. Pages 254-274 in Research and manage- ment techniques for wildlife and habitats (T. A. Bookhout, Ed.). The Wildlife Society, Bethesda, Maryland. Manly, B. F. J., L. L. McDonald, and D. L. Thomas. 1993. Resource selection by animals: statistical design and analysis for field studies. Chapman & Hall, London, United Kingdom. Mattox, W. G. and W. S. Seegar. 1988. The Green- land Peregrine Falcon Survey, 1972-1985, with emphasis on recent population status. Pages 27- 36 in Peregrine Falcon populations: their manage- ment and recovery (T. J. Cade, J. F. Enderson, C. G. Thelander, and C. M. White, Eds.). The Pere- grine Fund, Boise, Idaho. Mearns, R. and I. Newton. 1988. Factors affecting breeding success of peregrines in south Scotland. Journal of Animal Ecology 57:903-913. Meese, R. j. and M. R. Fuller. 1989. Distribution and behavior of passerines around Peregrine Falcon Falco peregrinus eyries in western Greenland. Ibis 131:27-32. Newton, I. 1979. Population ecology of raptors. T. & A.D. Poyser, London, United Kingdom. Newton, I. 1998. Population limitation in birds. Aca- demic Press Limited, London, United Kingdom. Ratcliffe, D. a. 1993. The Peregrine Falcon, 2nd ed. Buteo Books, Vermillion, South Dakota. Rosenfield, R. N., j. W. Schneider, J. M. Papp, and W. S. Seegar. 1995. Prey of Peregrine Falcons breeding in West Greenland. Condor 97:763-770. SAS Institute, Inc. 1990. SAS/STAT users guide, ver. 6.0, 4th ed. SAS Institute, Inc., Cary, North Car- olina. Tucker, V. A., A. F. Tucker, K. Akers, and J. F. Enderson. 2000. Curved flight paths and side- ways vision in Peregrine Falcons (Falco peregri- nus). Journal of Experimental Biology 203:3755- 3763. White, C. M. and T. J. Cade. 1971. Cliff-nesting rap- tors and ravens along the Colville River in arctic Alaska. Living Bird 10:107-150. White, C. M., N. J. Clum, T. J. Cade, and W. G. Hunt. 2002. Peregrine Falcon (Falco peregrinus). The Birds of North America, no. 660. White, C. M. and R. W. Nelson. 1991. Hunting range and strategies in a tundra breeding peregrine and Gyrfalcon observed from a helicopter. Journal of Raptor Research 25:49-62. Zar, j. H. 1996. Biostatistical analysis, 3rd ed. Pren- tice-Hall, Englewood Cliffs, New Jersey. Wightman and Fuller • PEREGRINE HABITAT SELECTION IN GREENLAND 235 APPENDIX. Description of physical characteristics measured at 67 occupied nesting cliffs and 38 cliffs unused by Peregrine Ealcons in central West Greenland. Measurements were made in 1998-1999; cliffs were categorized as occupied or unused based on their occupancy history from 1972 to 1999. Feature Description Method Cliff features'* Elevation (m) Cliff height (m) Slope (m) Height of hill below cliff (m) Aspect of cliff (°) Vegetation Boulders Height of ledge (m) Height of cliff at ledge (m) Position of ledge on cliff Human disturbance Ledge features*^ Ledge length (cm) Ledge depth (cm) Aspect of ledge (°) Horizontal angle of expo- sure (°) Vertical angle of exposure o Accessible by fox or human Substrate material on ledge Vegetation on ledge Overhang protection on ledge Topographical features Total elevation gain (rn) Elevation above drainage (m) Elevation of hill across val- ley (m) Distance to permanent water (m) Distance to drainage (m) Distance to hills across val- ley (km) Nearest cliff (km) Meters above sea level at top of cliff Cliff height from base of cliff to highest point, not including any ledges or tiers Slope of cliff calculated as rise/run Measured from base of hill to bottom of cliff formation Aspect perpendicular to rock face Predominant vegetation types below cliff face Presence of boulders at base of cliff Height from base of cliff to ledge Cliff height intersecting ledge Upper, center, lower and right, middle, left Minimal; >5 km from human settlement or roads Moderate: 1—5 km from human settlements or roads Severe: <1 km from human settlements or roads Topographic map Rangefinder and clinometer’’ Rangefinder and clinometeD Rangefinder and clinometer’’ Compass Direct observation Direct observation Rangefinder and clinometer’’ Rangefinder and clinometer’’ Direct observation Topographic map Length of ledge at longest point Depth of ledge at widest point Aspect of ledge perpendicular to back wall Degree of opening to right and to left of ledge Back wall of ledge to front lip of roof at ledge Yes or no Bare rock, gravel, sand/dirt, vegetation, or stick nest Yes or no None: 0% of ledge shaded midday Slight: 1-25% of ledge shaded midday Partial: 50—75% of ledge shaded midday Complete: ledge completely shaded midday Elevation of cliff minus lowest elevation within a 3-km radius circle around nest- ing cliff Elevation of cliff minus elevation of drain- age Elevation of hills across valley from cliff Distance from clitf to permanent water Distance from sample clitf to closest drain- tige Distance from clitf to hills across valley Distance from sample clitf to nearest clift regardless of occupancy status Measuring tape Measuring tape Compass Compass Clinometer Direct observation Direct ob.servation Direct observation Direct observation Topographic map bpographic map bpographie map opographic map opographic map b|‘)ographic ma|i opographic map 236 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 APPENDIX. Continued. Feature Description Method Nearest occupieti cliff (km) Distance from sample cliff to nearest cliff occupied by peregrines at least once be- tween 1972 and 1999 Historical data and topo- graphic map Nearest neighbor (km) Distance Ifom sample cliff to nearest cliff occupied in same year Historical data and topo- graphic map “Continuous vertical rock >14 m tall surrounding the eyrie or putative eyrie. All cliffs were level with or higher than the observation point. Height was measured by calculating the height to the top and bottom of the cliff from the observation point (e.g., distance to top X sin [angle to top]) and then subtracting the bottom height from the top height. For a few tall cliffs, we were unable to measure the distance to the top of the cliff. To measure height at these cliffs, we used the equation: height = a X b, where a = the angle to bottom of cliff X angle to top of cliff, and b = distance to bottom of cliff X secant from observation point to bottom of cliff. Slope could not be calculated at those cliffs where we could not measure the distance to the top of the cliff because the horizontal distance of the cliff (run) was unknown at these sites. Place on ledge where eggs laid. On unused ledges, measures were taken from the best potential eyrie ledge (i.e., 0° slope). Wilson Bulletin 1 17(3):237-244, 2005 SURVIVAL AND CAUSES OF MORTALITY IN WINTERING SHARP-SHINNED HAWKS AND COOPER’S HAWKS TIMOTHY C. ROTH, II,^ ^ STEVEN L. LIMA,* AND WILLIAM E. VETTERS 2 ABSTRACT. Sharp-shinned Hawks {Accipiter striatus) and Cooper’s Hawks (A. cooperii) are important predators of birds in North America, but little is known about their natural history during the winter. Even basic survival information is not well documented in these species and is generally unknown during the winter. Therefore, we examined survivorship and causes of mortality among wintering Cooper’s and Sharp-shinned hawks. We radio-tracked 27 Cooper’s and 40 Sharp-shinned hawks during 5 winters from 1999 to 2004. Neither species nor sex was a significant co variate of survivorship, but the probability of adult survival (75.4%) over 1 10 days was significantly higher than that of juveniles (9.4%). Our estimate of adult survivorship is comparable with those published for other accipiters, but our estimate for juveniles is lower. Age differences in survivorship may be attributed to risk taking or inexperience in juveniles and/or difficulties in dealing with transmitter attachments. Two types of mortality (predation and collisions) were observed in the study. Whereas predation by owls was a major source of mortality in rural habitat, no predation was observed in the urban habitat. Our results suggest that predation by owls may have important implications for the behavioral interactions between accipiters and their prey. Received 20 October 2004, accepted 31 May 2005. Although Sharp-shinned Hawks {Accipiter striatus) and Cooper’s Hawks (A. cooperii) are the main predators of small birds winter- ing in North America, very little is known about their natural history during the winter. Even basic information, such as diet, hunting patterns, general movements, and home-range size, is lacking (Rosenfield and Bielefeldt 1993, Bildstein and Meyer 2000). This lack of information is particularly problematic given that these hawks play a critical role in an im- portant conceptual paradigm in behavioral ecology; the small-bird-in-winter. Under this paradigm, small birds face trade-offs between the risks of starvation and predation from ac- cipiter hawks. This conceptual paradigm has had great impact on our present understanding of many aspects of behavioral ecology, such as sociality (Pulliam and Caraco 1984, Boin- ski and Garber 2000), foraging behavior (Lima 1985, Stephens and Krebs 1986), and predator-prey theory (Mangel and Clark 1988, Houston and McNamara 1999). Like other aspects of their natural history, the demography of Sharp-shinned and Coo- per’s hawks is poorly understood (Rosenfield ' Dept, of Ecology and Orgauismal Biology, Indiana State Univ., I'erre Haute. IN 47S09, USA. ^Current addre.s.s: Thunderbird Wildlife (’onsulting. Inc.. 1901 Energy Ct.. Ste. 115, C’lillette, WY 827 1 H USA. and Bielefeldt 1993, Bildstein and Meyer 2000). Basic survivorship estimates and the relative importance of causes of mortality are unknown during winter and rarely document- ed during the rest of the year. Much of what we know about accipiter survival is based on banding data (see Reran 1981). For Cooper’s Hawks, survivorship estimates from band re- coveries are 19-28% for first-year birds and 63-79% for older birds (Henny and Wight 1972, Boal 1997). Some recent telemetry in- formation from breeding studies of Cooper’s Hawks in urban sites resulted in survivorship estimates of 49% for nestlings (Boal and Man- nan 1999) and 67% from post-fledgling to midwinter (Mannan et al. 2004), but no other estimates of survivorship have been published for adults. Similarly, limited band recoveries published by Palmer (1988) resulted in sur- vivorship estimates of 20-25% for Sharp- shinned Hawks. To our knowledge, there are no other published data on the survivorship of these two species. Although relatively little information exists on Cooper's Hawks and Sharp-shinned Hawks, perhaps the best available insights into their survival rates come from studies of other accipiters. In North America, Northern (loshawk {A. i^euti/is) survivorship is estimat- ed at 33% for first-year birds. 68% for sub- adults, and 81% for adults (Sejuires and Reyn- olds 1997). Dewey and Kennedy (2001) esti- ’ Corre.sponding indstate.edu author; e-mail: IsrothC^fisugw. mated a greater average first-year survivorship 237 238 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 (control group only, 73%), similar to that es- timated for sub-adults by Squires and Reyn- olds (1997). Another source of information on accipiter survivorship comes from European studies of the goshawk and the Eurasian Spar- rowhawk {A. nisus). Tornberg and Colpaert (2001) estimated goshawk survivorship at 43% for first-year birds, and about 84% in older birds. Kenward et al. (1999) estimated similar rates of survival at approximately 50% for first-year males, 70% for first-year fe- males, and about 80% for both sexes in older birds. While juvenile survivorship is consid- erably lower in sparrowhawks (30% for males, 50% for females) than in goshawks, adult survival rates are comparable at nearly 70% for both sexes of both species (Newton 1975; Newton et al. 1983, 1999). Based on the information available for other accipiters, the general pattern seems to be that juvenile survival is approximately half that of adults. Little consideration has been given to the causes of mortality in post-fledgling Sharp- shinned and Cooper’s hawks. Based on the scant information that exists, human-induced mortality seems to be due mainly to collisions with windows or automobiles (Keran 1981, Klem 1990, Klem et al. 2004) and electrocu- tion (Lehman 2001). Similarly, Boal (1997) attributed 68% of adult Cooper’s Hawk mor- tality to collisions with automobiles or win- dows, and 3% to electrocution. As urban pop- ulations of accipiters (especially Cooper’s Hawk) increase, such “accidental” mortality may become increasingly common (see Boal and Mannan 1999). Mortality due to gunshot and poison (important causes of mortality in the past) have greatly diminished since imple- mentation of federal protection and the elim- ination of DDT/DDE in North America (Ker- an 1981), although Boal (1997) reports recent mortality rates from gunshot (13%) and poi- son (6%) for Cooper’s Hawks. Natural pre- dation by owls and other raptors on accipiters has been documented (Klem et al. 1985, George 1989), but the demographic impor- tance of such predation is unknown. Disease may also be an important mortality factor, par- ticularly during the breeding season (Ward and Kennedy 1996, Boal et al. 1998). The objective of our research was to obtain a better understanding of accipiter natural his- tory and behavior, with the long-term goal of obtaining insight into predator-prey interac- tions in wintering birds. We studied the be- havior and general natural history of Cooper’s and Sharp-shinned hawks over several winter periods. Here, we present data on one aspect of accipiter natural history: winter survival and causes of mortality. As little is known about North American accipiters, predictions are difficult; however, our expectation was that Sharp-shinned Hawks were more likely targets of predation due to their smaller size, which may result in lower survival relative to that of Cooper’s Hawks. Based on studies of other accipiters, we also expected juvenile mortality of Cooper’s and Sharp-shinned hawks to be greater than that of adults. METHODS Study site. — Our study site was centered in Vigo County in west-central Indiana and the adjacent counties in Indiana and eastern Illi- nois. The site included both urban and rural areas. Our urban area was centered at Terre Haute, Indiana (pop. 60,000; 39° 27.1' N, 87° 18.5' W) and covered approximately 40 km^. There, we focused on Cooper’s Hawks, mainly during the winter seasons of 1999- 2001 (see also Roth and Lima 2003); one Coo- per’s Hawk was also tracked into the urban site during the winter of 2003—2004. Approximate- ly 30% of this area consisted of high-density residential and commercial properties (>14 buildings/block), whereas the remaining 70% encompassed lower-density residential areas (<14 buildings/block; Topologically Integrat- ed Geographic Encoding and Referencing [TI- GER] data, U.S. Census Bureau, Geography Division 2000, http://www.census.gov/geo/ www/tiger/). Although we attempted to study Sharp-shinned Hawks in this urban setting, none could be trapped and few were observed. Our rural area included all areas adjacent to, and mainly west of, the Wabash River, which is to the immediate southwest of our urban area. Here, we focused mainly on Sharp-shinned Hawks during the winter sea- sons of 2000-2004, but also tracked several Cooper’s Hawks. Northern Goshawks were not included in this study, as they are very rare in west-central Indiana; only one was ob- served during the 5 -year study, and only one has been recorded during the 45 years of the local Christmas Bird Count (R E. Scott pers. Roth et al. • SURVIVAL OF WINTERING ACCIPITERS 239 comm.). The rural study area covered approx- imately 1,000 km^ and included small clusters of houses, agricultural land, and fragmented forest. The landscape was composed of ap- proximately 3.7% residential, 48% agricultur- al field (bare in winter), 17.9% grass/fallow field, 24.9% upland forest, 3.7% bottomland forest, 0.4% wetland, and 1.4% water (lakes, ponds, river). Capture and tracking. — Using constantly monitored bal-chatri traps (Berger and Muell- er 1959) and bow nets, we conducted trapping from late November through late January dur- ing each winter. Traps were baited with Eu- ropean Starlings (Sturnus vulgaris) and House Sparrows {Passer domesticus). We positioned traps in open areas, along potential travel paths, and at potential roost locations used by accipiters. For example, in the city, we com- monly trapped in parking lots, cemeteries, and recreational parks, and, in the rural area, we trapped in bare fields, along roadsides and power lines, and at a few long-established bird feeders. We recaptured only one individual during the study, whereupon we removed the transmitter and harness and examined the hawk for signs of transmitter-related stress. Once captured, our accipiters assiduously avoided traps on future encounters (TCR and SLL pers. obs.). We used radio-telemetry to track hawks. Hawks were fitted with 2.4- to 1 1 .0-g posi- tion-sensitive transmitters (models BD-2P, PD-2P, and RI-2CP; Holohil Systems, Carp, Ontario, Canada; Sharp-shinned Hawks: male, 2.4 g; female, 3. 5-4. 5 g; Cooper’s Hawks: male, 4.2— 5.8 g; female, 6.9—1 1.0 g) using the pelvic harness technique of Rappole and Tip- ton (1994; see also Roth and Lima 2003). In all cases, transmitter mass was <3% (mean = 2.09% ± 0.09 SE) of the hawk’s total body mass. Transmitters had a life expectancy of approximately 3 months (2.4-g model) to over 6 months (I 1 .0-g model). A position-sensitive switch on the transmitters provided informa- tion on hawk posture (horizontal or vertical) and was instrumental in determining mortali- ty. A stationary signal indicating that the transmitter was horizontal — with no fluctua- tion— was usually a good indication of mor- tality, which prompted attempts to conduct vi- sual verification. Tracking was usually conducted from the day of capture until the hawk was found dead or had abandoned the study site, or until the transmitter failed. All hawks were tracked >2 hr (frequently up to 10 hr) daily from vehieles using yagi and whip antennae. In addition, ac- tivity was monitored at roosts 0.5 to 1 hr be- fore sunrise and 0.5 to 1 hr after sunset. The primary purpose of this intensive tracking was to collect detailed behavioral data, such as diet, movement, and activity. Due to this in- tensive tracking, we are certain of the day dur- ing which a hawk died or left the study site. If a hawk’s signal was lost, we verified its departure with systematic scanning of the en- tire study site for >7 days. We distinguished hawk departure from transmitter failure in two ways: (1) transmitters that were about to fail typically produced signature shifts in signal (C. J. Amlaner pers. comm.), and (2) trans- mitters lost due to harness failure were re- trieved. The hawks did not demonstrate any evidence of disturbance by our presence in ve- hicles, so we assumed that our tracking did not provoke any movement from the site. Sources of mortality were predation and ac- cidents (collisions with windows and vehi- cles). Although we did not observe predation events, we used the condition of the kill to determine the probable cause of predator-in- duced mortality. Plucked remains in a neat pile suggested predation by an accipiter, most likely Cooper’s Hawk (TCR and SLL pers. obs.), whereas remains that were mostly in- tact, but decapitated or cleanly cut in half (Houston et al. 1998, Mazur and James 2()()0) with large, triangular incisions, and/or those with crimped antenna, suggested owl preda- tion. In most cases, we were able to recover the carcass within 12 hr of death (i.e., early the next morning when the hawk did not leave roost). We usually recovered the posterior por- tion of the carcass, as the transmitters were never removed from the body. All retrieved carcasses of hawks that had died during the night showed signs of predation; none had conical teeth marks or masticated bones. J'his is strong evidence that hawks were not scav- enged by mammals during the night, but were killed on or near their roost by owls. For deaths from collision, we used the lo- cation and condition of the carcass to identify the object with which the hawk collided. Re- mains found along a roadside with signs of 240 THE WILSON BULLETIN • VoL 117, No. 3, September 2005 blunt trauma, but with no sign of predation, were considered vehicular-collision mortali- ties, whereas those found near a house and with no sign of predation, but with apparent trauma to the head, were considered window- collision mortalities. Although we observed some hawks collide with windows, none of the observed cases resulted in mortality. If we could not recover the remains within 1 day, we used the location of the kill to determine the probable cause of mortality (predation ver- sus collision near house). If the location pro- vided no clear indication of the cause of mor- tality, the cause was considered unknown. Survivorship analysis. — We estimated sur- vivorship using the Kaplan-Meier procedure (Kaplan and Meier 1958) with a Cox propor- tional hazard regression model (Cox 1972) to determine the effects of sex, age, and species on survival using Systat (SPSS, Inc. 1998). The Cox model produces a standard survivor function and permits the analysis of covariates with proportional shifts of the hazard function. We used sex and species as covariates of sur- vival and stratified by age to distinguish dif- ferences between juveniles (hawks in their first year) and adults (hawks after their first year). A log-rank Mantel test was used to re- veal differences between the age strata (SPSS, Inc. 1998). All data points were right censored when hawks left the study site as itinerants (birds lacking stable home ranges and possi- bly still migrating) or migrants (birds that moved north in March or April), or were lost for other reasons (e.g., transmitter failure). We do not include hawks depredated within 7 days of transmitter attachment (four cases), as these deaths were possibly related to capture, the transmitter, or the transmitter attachment and are possibly the result of preoccupation with the transmitter and the resulting lack of vigilance. In all hawks, transmitter “groom- ing” was minimal by the 2nd or 3rd full day of transmitter attachment; thus, the 7-day pe- riod was thought to be long enough to remove the effects of newly attached transmitters from the analysis. RESULTS We captured and tracked 40 Sharp-shinned Hawks (40 rural, 0 urban) and 27 Cooper’s Hawks (14 rural, 13 urban) during the 5-win- ter study. The sex ratio of captured hawks was not significantly different from 1:1 for either species (Sharp-shinned Hawks: males = 18, females = 22, — 0.40, df = 1, P = 0.53; Cooper’s Hawks: males = 13, females = 14, = 0.04, df = \, P — 0.85), although the sex ratio of Cooper’s Hawks differed between urban and rural habitats (urban: males = 2, females = 11; rural: males = 11, females = 3; Fisher exact test, P = 0.001). The age ratio was biased toward immatures in both species and was not significantly different between species (Sharp-shinned Hawks: adult = 14, immature = 26; Cooper’s Hawks: adult =11, immature = 16; x^ ^ 0.23, df = 1, P = 0.63; Table 1). Neither species nor sex were significant co- variates of survivorship (log-likelihood x^ es- timate = 1.98, df = 2, P = 0.37; sex: t < 0.001, P > 0.99; species: t = 1.36, P = 0.17). Adult survival was significantly higher than juvenile survival (Mantel method, x^ = 4.42, df = 1, P = 0.036). The probability of sur- vival over the 110-day study period was 9.4% for juveniles and 75.4% for adults (Fig. 1). Mortality events occurred throughout the study up to 101 days after transmitter attach- ment; however, after the first 7 days, there was no evidence of increasing risk of mortality with time (Fig. 1). Although not significant, winter survival tended to be greater for Coo- per’s Hawks than for Sharp-shinned Hawks. Seven of 13 (53.8%) Cooper’s Hawks with known fates survived the winter (i.e., itiner- ants and hawks with unknown fates removed from analysis), while only 8 of 23 (34.8%) Sharp-shinned Hawks survived (Table 1). Many hawks appeared to be itinerant, as in- dicated by their lack of a stable home range (TCR and SLL unpubl. data) and eventual abandonment of the study site. Of the 27 Coo- per’s and 40 Sharp-shinned hawks captured, 5 (18.5%) and 11 (27.5%), respectively, left the study site (itinerants. Table 1). There was no significant effect of age on the tendency to be itinerant (x^ = 0.39, df = 1, P = 0.53); on the three occasions when itinerant hawks left as they were being tracked, all moved south of the study site at least 20-30 km before we lost their signal. As we tracked hawks through the end of winter, we recorded the proportion of individ- uals (of those with functioning transmitters) that remained on the study site during the Roth et al. • SURVIVAL OF WINTERING ACCIPITERS 241 TABLE 1. Eates of wintering Cooper’s and Sharp-shinned hawks captured in 2004. west-central Indiana, , 1999- Cooper’s Hawk Sharp-shinned Hawk Adult Immature Total Adult Immature Total Total no. of hawks captured 11 16 27 14 26 40 Fate determined (54% of captured hawks) Died Collision 0 3 3 1 2 3 Predation 0 3 3 3 9 12 Survived Migrated 1 1 2 4 4 8 Resident 2 3 5 — — Total determined fates 3 10 13 8 15 23 % mortality of hawks with determined fate 0.0 60.0 46.2 50.0 73.3 65.2 Fate undetermined (46% of captured hawks) Itinerant 4 1 5 3 8 11 Unknown 4 5 9 3 3 6 Total undetermined fates 8 6 14 6 11 17 breeding season (Table 1). Sharp-shinned Hawks do not routinely breed in western In- diana, and all surviving Sharp-shinned Hawks (8/8) migrated north in late March or early April. Approximately 70% (5/7) of Cooper’s Hawks were residents, while the remaining birds (2/7) were migrants. Of the migrant Cooper’s Hawks, one died after a collision with a window about 75 km north of the study site. Predation was a major source of mortality. Of all hawks (excluding itinerants and hawks 0 20 40 60 80 100 120 Days FIG. 1. Survivorship of wintering accipitcrs (Sharp-shinned and Cooper’s hawks combined), by age class, in west-central Indiana, 1999 2004. Juvenile survival rate (solid line) is significantly lower than that for adults (daslied line; !* = 0.036) based on the C'ox proportional hazard model. See text for details. with unknown fates), 23.1% (3/13) of Coo- per’s Hawks and 52.2% (12/23) of Sharp- shinned Hawks were killed by a predator (Ta- ble 1). Of all causes of mortality, predation accounted for 50% (3/6) among Cooper’s Hawks (two by owl and one by an unknown predator) and 80% (12/15) among Sharp- shinned Hawks (six by owl, one by Cooper’s Hawk, and hve by unknown predators). This species-specihc difference in predator-induced mortality was not signihcant (Fisher exact test, P = 0.29). Additionally, four hawks (three Sharp-shinned, one Cooper’s) were dep- redated within 7 days of transmitter attach- ment (as noted above, these individuals were not included in the survivorship analysis). All predation on Cooper’s Hawks occurred in the rural site; only accidental death was observed in the urban site. Collisions with windows and automobiles were the main sources of accidental mortality. In the urban area, we documented two fatal collisions, one each with a window and an automobile. We also ob.scrved several non-Ie- thal collisions with windows. In two cases, it seemed that hawks were attempting to attack a competitor (their refleetion) and, as a result, hit the window first with their talons, fhe im- pact of such collisions did not seem to cause problems for the hawks during the course of the study. An additional urban hawk flew into 242 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 an open garage, apparently suffered head in- juries, and died 1 day later. In the rural area, we recorded two fatal collisions with win- dows— one with an automobile and one with a boulder, possibly during an attack. The latter event may have been an indirect effect of the recently attached transmitter (collision oc- curred 3 days after attachment). DISCUSSION The winter survivorship of Cooper’s and Sharp-shinned hawks was approximately 9% for immatures and 75% for adults. Adult sur- vival was significantly greater than that of im- mature hawks, but there was no significant ef- fect of species or sex in the model. Mortality was caused predominantly by owl predation in the rural habitat and by accidents in the urban habitat. The survival rates of adult Sharp-shinned and Cooper’s hawks in our study fall within the range of those published elsewhere. Adult survivorship seems to be about 60—80% for most accipiters (Henny and Wight 1972, Boal 1997, Squires and Reynolds 1997, Tornberg and Colpaert 2001), and this is consistent with our results for the adults of both species. In addition, differences between juvenile and adult mortality have been observed in other accipiter populations such as Cooper’s Hawks (Henny and Wight 1972, Boal 1997), North- ern Goshawks (Kenward et al. 1999), and Sparrowhawks (Newton 1975; Newton et al. 1983, 1999). Although we also found age-re- lated differences in accipiter mortality, juve- nile survivorship (9.4%) in our study was lower than that typically reported for juvenile hawks elsewhere (20-50%; Henny and Wight 1972, Newton et al. 1983, Boal 1997, Ken- ward et al. 1999). The high predation rates on juvenile hawks in our study might reflect a high site-specific abundance of owls, although we have no data on owl densities in our study area. Transmitter attachment also may have contributed to the low survival of juvenile hawks. We removed from our analyses four immature hawks that were depredated within the first 7 days of tracking, the period when we observed the greatest amount of excessive (>2 hr/day) transmitter grooming. Beyond this period, the survivorship functions of both adults and ju- veniles were generally linear. Given the po- tential difficulties experienced by juveniles in hunting and avoiding predators, the added mass, handling, and possible distraction by the transmitter attachment may have negatively influenced juvenile hawks. We note, however, that adult survival was not unusually low and no mortality was observed due to starvation. In addition, Reynolds et al. (2004) found no effect of backpack transmitters on goshawks, supporting the notion that our transmitters did not have a detrimental effect on survival. Whereas we used a synsacral mount rather than a backpack, the effects on flight dynam- ics are likely similar. Although we cannot sep- arate predation on food-stressed or weakened hawks from predation on healthy hawks, we noted no emaciated birds among our recov- eries. Furthermore, close inspection of all re- captured (one) or recovered (eight) hawks re- vealed no apparent long-term influence of transmitters or harnesses on the health of hawks, with the exception of one ectoparasite infestation localized under the transmitter (this bird was killed in an accidental collision). Overall, we suspect that juvenile survivorship in our study site was genuinely quite low. Nearly 25% of our captured hawks were ap- parently itinerant. These hawks failed to main- tain stable home ranges and typically disap- peared within 14 days of capture. On three occasions, we managed to track itinerant hawks as they moved southward, and typically lost their signals 20-30 km south of the study site. This suggests that itinerant hawks were still moving southward, even as late as Janu- ary. Furthermore, the Wabash River runs north-south through the study site and mi- grating hawks use geographical features such as rivers during migration (Zalles and Bild- stein 2000); therefore, the presence of the riv- er may have contributed to the proportion of migrating itinerants in our study site. Our results indicate interesting differences in survivorship and causes of mortality be- tween urban and rural habitats, but the lack of Sharp-shinned Hawks in urban habitats and relatively small numbers of rural Cooper’s Hawks limited our ability to draw firm con- clusions. Predation was common in the rural area, but was not observed in the urban area, which was consistent with Boal’s (1997) ob- servations. In our study, the lack of predation in the urban area may have been due to a lack Roth et al • SURVIVAL OF WINTERING ACCIPITERS 243 of owls and the numerical dominance of the larger female Cooper’s Hawks (but see Man- nan et al. 2004). In the absence of owls, large female hawks do not face the same mortality risks as their rural counterparts. In fact, our urban Cooper’s Hawks were much more likely to hunt roosting prey at night by using the illumination of urban lighting and the moon, than were rural hawks (TCR and SLL pers. obs.). Rural hawks, particularly Sharp-shinned Hawks, may have avoided hunting in dim light due to the increased risk of predation from owls. Furthermore, the incidence of deadly collisions with windows and cars (one each) is surprisingly low in the urban habitat, given the concentration Df such hazards in ur- ban areas. Overall, our urban area is probably not a sink habitat for wintering Cooper’s Hawks; however, some urban studies have re- vealed extremely high rates of mortality among urban Cooper’s Hawks (particularly nestlings) during the breeding season (Boal 1997, Boal and Mannan 1999), suggesting that urban areas may sometimes represent re- productive sinks. One might expect Sharp-shinned Hawks to occur frequently in the city given the large potential prey base (i.e.. House Sparrows; Roth and Lima 2003) and a probable owl-free environment (TCR and SLL pers. obs.). How- ever, we observed very few urban Sharp- shinned Hawks. One possible explanation is that Sharp-shinned Hawks preferred the more dense vegetation typically found in our rural area. However, our rural Sharp-shinned Hawks frequently hunted in open areas such as near feeders and hedge rows where prey were abundant. Thus, we suggest that Sharp- shinned Hawks avoided the urban habitat for other reasons: predation and possibly compe- tition. The abundance of large female Coo- per’s Hawks in our urban habitat made it dan- gerous for all 100- to 400-g birds (Roth and Lima 2003), including Sharp-shinned Hawks (we had one apparent case of a Cooper’s Hawk depredating a Sharp-shinned Hawk in our rural study area). Thus, the smaller Sharp- shinned Hawk may have avoided the urban habitat due to a greater perceived risk of pre- dation. In addition, urban Sharp-shinned Hawks may experience aggressive competi- tion from Cooper's Hawks. vSharp-shinned Hawks frequently take larger prey, such as starlings and Mourning Doves {Zenaida ma- croura\ TCR and SLL unpubl. data), the main prey of urban Cooper’s Hawks in our study area (Roth and Lima 2003). Finally, our results suggest that future stud- ies on the behavior of small wintering birds should consider the implications of intraguild predation in raptors. Owls are apparently a significant threat to rural hawks, especially Sharp-shinned Hawks, during the crepuscular periods. Thus, we would expect that rural hawks might reduce their activity during these periods unless food stressed. In fact, we ob- served a tendency for Sharp-shinned Hawks to leave roosts late (after sunrise) and return well before sunset (TCR and SLL unpubl. data; see also Sunde et al. 2003). Small birds may take advantage of periods when Sharp- shinned Hawks are not active by feeding early and late in the day, and feed less during the midday when both Sharp-shinned and Coo- per’s hawks are active. In addition. Cooper’s Hawks are a potential threat to Sharp-shinned Hawks during most of the day. Sharp-shinned Hawks may reduce their activity in areas where Cooper’s Hawks are abundant (e.g., ur- ban habitat), thereby reducing the risk of pre- dation experienced by smaller birds, such as sparrows (Roth and Lima 2003). ACKNOWLEDGMENTS We thank W. E. Eranklin, III, and our many field technicians for their assistance with hawk tracking. We also thank local businesses, landowners (especially M. Evrard, J. Irwin, C. Martin, and C. Miller), and the Terre Haute Parks Department for their cooperation. T. D. Steury provided insight into statistical analyses. C. E. Boal, J. Castrale, P. E. Scott, and two anonymous reviewers provided helpful comments on drafts of this manuscript. This research was supported, in part, by the National Science Foundation (Grant IBN- 0130758), the Indiana Academy of Sciences, and the Indiana State University Department of Ecology and Organismal Biology and School of Graduate Studies. LITERATURE CITED Bi:k(;i:k, D. D. and H. C'. Mim i i i k. 1059. 'fhe bal- chatri: a trap for the birds of prey. Bird-Bandiiiii 30: 1 8-26. Bn Dsrt IN, K. I., and K. Mi a i k. 2000. Sharp-shinned Hawk {/\ccif)iicr Mriam.s). fhe Birds of North America, no. 482. Boai , ('. W. 1997. An urban environment as an eeo- logieal trap tor ('ooper's Hawks. Ph.D. tlisserla- tion. University of Arizona, rueson. Boai . (’. W. and K. W. M \nnan. 1999. C'omparative 244 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 breeding ecology of Cooper’s Hawks in urban and exurban areas of southeastern Arizona. Journal of Wildlife Management 63:77-84. Boal, C. W., R. W. Mannan, and K. S. Hudelson. 1998. Trichomoniasis in Cooper’s Hawks from Arizona. Journal of Wildlife Diseases 34:590- 593. Boinski, S. and R a. Garber. 2000. On the move: how and why animals travel in groups. University of Chicago Press, Chicago, Illinois. Cox, D. R. 1972. Regression models and life-tables. Journal of the Royal Statistical Society, Series B 34:187-220. Dewey, S. R. and P. L. Kennedy. 2001. Effects of supplemental food on parental-care strategies and juvenile survival of Northern Goshawks. Auk 118:352-365. George, J. R. 1989. Bald Eagle kills Sharp-Shinned Hawk. Journal of Raptor Research 23:55-56. Henny, C. J. and H. M. Wight. 1972. Population ecol- ogy and environmental pollution: Red-tailed and Cooper’s hawk. Pages 229-250 in Population ecology of migratory birds: a symposium. Wild- life Research Report, no. 2. U.S. Fish and Wildlife Service, Washington, D.C. Houston, A. and J. McNamara. 1999. Models of adaptive behavior. Cambridge University Press, Cambridge, United Kingdom. Houston, C. S., D. G. Smith, and C. Rohner. 1998. Great Horned Owl {Bubo virginianus). The Birds of North America, no. 372. Kaplan, E. L. and P. Meier. 1958. Nonparametric es- timation from incomplete observations. Journal of American Statistical Association 53:457-481. Kenward, R. E., V. Marcstrom, and M. Karlbom. 1999. Demographic estimates from radio-tagging: models of age-specific survival and breeding in the Goshawk. Journal of Animal Ecology 68: 1020-1033. Keran, D. 1981. The incidence of man-caused and natural mortalities to raptors. Raptor Research 15: 108-112. Klem, D., Jr. 1990. Collisions between birds and win- dows: mortality and prevention. Journal of Field Ornithology 61:120-128. Klem, D., Jr., B. S. Hillegass, and D. A. Peters. 1985. Raptors killing raptors. Wilson Bulletin 97: 230-231. Klem, D., Jr., D. C. Keck, K. L. Marty, A. J. Miller Ball, E. E. Niciu, and C. T. Platt. 2004. Effects of window angling, feeder placement, and scav- engers on avian mortality at plate glass. Wilson Bulletin 116:69-73. Lehman, R. N. 2001. Raptor electrocution on power lines: current issues and outlook. Wildlife Society Bulletin 29:804-813. Lima, S. L. 1985. Maximizing feeding efficiency and minimizing time exposed to predators: a trade-off in the Black-capped Chickadee. Oecologia 66:60- 67. Mangel, M. and C. W. Clark. 1988. Dynamic mod- eling in behavioral ecology. Princeton University Press, Princeton, New Jersey. Mannan, R. W., W. A. Estes, and W. J. Matter. 2004. Movements and survival of fledgling Coo- per’s Hawks in an urban environment. Journal of Raptor Research 38:26-34. Mazur, K. M. and P. C. James. 2000. Barred Owl {Strix varia). The Birds of North America, no. 508. Newton, I. 1975. Movements and mortality of British Sparrowhawks. Bird Study 22:35-43. Newton, L, M. Marquiss, and P. Rothery. 1983. Age structure and survival in a Sparrowhawk popula- tion. Journal of Animal Ecology 52:591-602. Newton, I., I. Wyllie, and L. Dale. 1999. Trends in number and mortality patterns of Sparrowhawks (Accipiter nisus) and Kestrels (Falco tinnunculus) in Britain, as revealed by carcass analyses. Journal of Zoology 248:139-147. Palmer, R. S. 1988. Handbook of North American birds, vol. 4. Yale University Press, New Haven, Connecticut. Pulliam, H. R. and T. Caraco. 1984. Living in groups: is there an optimal group size? Pages 127-147 in Behavioral ecology: an evolutionary approach, 2nd. ed. (J. R. Krebs and N. B. Davies, Eds.). Blackwell Press, Oxford, United Kingdom. Rappole, j. H. and a. R. Tipton. 1994. New harness design for attachment of radio transmitters to small passerines. Journal of Field Ornithology 62: 335-337. Reynolds, R. T, G. C. White, S. M. Joy, and R. W. Mannan. 2004. Effects of radiotransmitters on Northern Goshawks: do tailmounts lower survival of breeding males? Journal of Wildlife Manage- ment 68:25-32. Rosenfield, R. N. and J. Bielefeldt. 1993. Cooper’s Hawk {Accipiter cooperii). The Birds of North America, no. 75. Roth, T. C., II, and S. L. Lima. 2003. Hunting behav- ior and diet of Cooper’s Hawks: an urban view of the small-bird-in- winter paradigm. Condor 105: 474-483. SPSS Institute, Inc. 1998. SYSTAT for Windows, ver. 10.0. SPSS Institute, Inc., Chicago, Illinois. Squires, J. R. and R. T. Reynolds. 1997. Northern Goshawk {Accipiter gentilis). The Birds of North America, no. 298. Stephens, D. W. and J. R. Krebs. 1986. Foraging the- ory. Princeton University Press, Princeton, New Jersey. SuNDE, P, M. S. Bolstad, and K. B. Desfor. 2003. Diurnal exposure as a risk sensitive behavior in Tawny Owl {Strix aluco). Journal of Avian Biol- ogy 34:409-418. Tornberg, R. and a. Colpaert. 2001. Survival, rang- ing, habitat choice, and diet of the Northern Gos- hawk Accipiter gentilis during winter in northern Finland. Ibis 143:41-50. Ward, J. M. and P. L. Kennedy. 1996. Effects of sup- plemental food on size and survival of juvenile Northern Goshawks. Auk 113:200-208. Zalles, j. I. AND K. L. Bildstein (Eds.). 2000. Raptor watch: a global directory of raptor migration sites. BirdLife Conservation Series, no. 9. BirdLife In- ternational, Cambridge, United Kingdom. Wilson Bulletin 1 17(3):245-257, 2005 HABITAT USE BY RIPARIAN AND UPLAND BIRDS IN OLD- GROWTH COASTAL BRITISH COLUMBIA RAINFOREST SUSAN M. SHIRLEY^ ABSTRACT. — The value of riparian habitats to birds differs among ecosystems. I tested whether riparian habitat near large streams and rivers in the Pacific Northwest supported a higher abundance and diversity of birds than adjacent upland forest. From 1996 to 1998, I surveyed breeding birds at four 9-ha sites in coastal western hemlock forest on western Vancouver Island, British Columbia. Five species of forest generalists dom- inated both riparian and upland bird communities: Winter Wren {Troglodytes troglodytes). Chestnut-backed Chickadee (Poecile rufescens), American Robin (Turdus migratorius), Swainson’s Thrush (Catharus ustulatus), and Pacific-slope Flycatcher (Empidonax difficilis). Species richness and total abundance were similar over the riparian-to-upland gradient, whereas abundances of riparian specialists and aerial foragers declined with distance from the river. To explore whether vegetation composition and structure explained bird distribution patterns, I sampled three locations along both riparian and upland transects at each site. Riparian areas had higher densities of deciduous trees; conifer and snag densities were higher in upland areas. Salmonberry (Rubus spectahilis) cover was marginally higher in riparian areas and blueberry {Vaccinium spp.) cover was higher in upland areas. There was little effect of distance from the river on most bird species, but there were stronger associations of birds with specific vegetation attributes. Tree and snag densities explained the most variation in abundance of aerial foragers, and eight of nine individual species, whereas distance from the river and shrub cover were important predictors of Hammond’s Flycatcher {Empidonax hammondii) abundance. Apart from riparian spe- cialists and a few species with strong vegetation associations, bird assemblages in riparian and upland habitats of this moist forest type were dominated by similar sets of generalist species. Received 1 December 2003, accepted 26 April 2005. Riparian habitats are influenced by both stream channel processes and the adjacent up- land vegetation (Brinson et al. 1981, Naiman et al. 1993). Topography, plant communities, hydrologic regimes, and soil type typically distinguish riparian areas from upland areas. Riparian habitats are heavily influenced by seasonal changes in water flow, and alluvial soils in riparian habitats tend to be wetter than soils in uplands. Riparian plant communities have diverse vegetation structures, high edge: area ratios, and are dominated by woody veg- etation. These features are common to all ri- , parian habitats, but vary greatly depending on geographical location. Riparian ecosystems ' often support high bird diversity and abun- dance (Thomas et al. 1979, Knopf et al. 1988, Anthony et al. 1996) because of their complex vegetation structure (LaRue et al. 1995, Wicbe and Martin 1998), high plant diversity (Bull 1978, Raedeke 1988), and proximity to water. There is a strong bird diversity gradient from riparian to upland habitats in southwest- ern and agricultural regions of the U.S. (e.g., vStauHer and Best 1980, S/aro 1980, Knopf ' Dept, of Zoology, Univ. of British C'oliimbi:>. 6270 University Blvd., Vancouver, BC' V6I. IVS. ('anatla; e-mail: Shirley /oology. ubc.ca 1985, reviewed in Knopf and Samson 1994), where bird diversity is higher in riparian and lower in upland areas. In contrast, studies of mature, undisturbed stands in forests with greater annual precipitation (McGarigal and McComb 1992, Murray and Stauffer 1995, Wiebe and Martin 1998) have shown equal or lower diversity in riparian habitats compared with upslope habitats; these studies (Mc- Garigal and McComb 1992, Murray and Stauffer 1995, Wiebe and Martin 1998), how- ever, focused on riparian areas associated with small (<5 m wide) mountain streams. Some riparian areas show greater diversity near larg- er streams and rivers (Knopf and Samson 1994, Lock and Naiman 1998), anti the avian use of riparian habitat relative to uplaiul hab- itat along larger streams aiul rivers in the Pa- cific Northwest has not been well examinctl. I studietl avian habitat use along larger streams and rivers within continuous undis- turbed forest of the I^icilic Northwest. My first objective was to test the hypothesis that bird species diversity and abundanee is higher in old-growth riparian habitat associ- ated with large streams and ri\ers than in ad- jacent old-growth upland habitat. In the lii- cifie Northwest, riparian /ones tend to be 245 246 THE WILSON BULLETIN • Vol. 1 17, No. 3, September 2005 dominated by deciduous trees, whereas up- lands are dominated by conifers (McGarigal and McComb 1992, Pearson and Manuwal 2001). Disproportionate use of riparian habi- tats by birds should be reflected in a decline in species richness and abundance with in- creasing distance from the river, but associa- tion with riparian habitat may vary among species and guilds. Riparian specialists that rely on the stream or river as a food source and nest near streams should decline in abun- dance with increasing distance from the river. Riparian forest edges along streams support a higher invertebrate biomass (Murakami and Nakano 2002), due to higher densities of aquatic insects (Murakami and Nakano 2002), and possibly greater primary productivity (Ranney et al. 1981). Aerial foragers such as flycatchers may respond to emergent aquatic insects near streams and rivers (Gray 1993) and should occur at highest densities near the water’s edge. Conversely, conifer specialists may increase with distance from the river due to increasing conifer densities (McGarigal and McComb 1992, Pearson and Manuwal 2001). Second, I explored how variation in vege- tation composition and structure from riparian to upland habitat explains distribution patterns of several species. Studies conducted in other temperate coniferous forests have revealed differences in vegetation structure and com- position between riparian and upland (Mc- Garigal and McComb 1992, Pearson and Ma- nuwal 2001). If the structural and species at- tributes of riparian vegetation communities are the primary predictors of bird diversity and abundance, then use of riparian habitats should be related to the prevalence of these structures relative to upland areas. Alterna- tively, bird diversity and abundance should not differ between riparian and upland habi- tats that are similar in vegetation structure and composition. METHODS Study area. — The study was conducted in three valleys on the west coast of Vancouver Island, British Columbia, between Ucluelet in the north and Bamfield in the south (48° 5' N, 125° 5' W). Four sites of continuous old- growth forest were selected along the Nah- mint {n = 2; 2 km apart), Taylor {n = 1), and Klanawa rivers {n = 1). The sites were em- bedded within a mosaic of forest patches of different ages across a landscape in which the amount of primary forest varied from 50 to 70%. I classified rivers to stream order at a 1 : 50,000-map scale based on branching follow- ing Kuehne (1962). The Nahmint and Taylor rivers (fourth order) and the Klanawa River (fifth order) ranged in width from 15 to 57 m. Study sites were located in the Western Van- couver Island ecoregion, within the moist-to- very-wet maritime biogeoclimatic subzones of coastal western hemlock (Klinka et al. 1991, Nuszdorfer and Boettger 1994). The forest is dominated by amabilis fir {Abies amabilis), western hemlock (Tsuga heterophylla), and western red cedar {Thuja plicata). Red alder {Alnus rubra) and bigleaf maple {Acer macro- phyllum) occur at their greatest densities ad- jacent to the rivers, but were also scattered throughout the forest in moister areas. The un- derstory is dense, highly stratified, and con- tains shrubs such as salmonberry {Rubus spec- tabilis), red huckleberry {Vaccinium parvifo- lium), salal {Gaultheria shallon), and devil’s club {Oplopanax horridus), with Alaskan {Vaccinium alaskense) and oval-leaf blueberry {V. ovalifolium) predominating in the upland areas. The climate is cool and wet in winter and warm and dry in late summer (July-Sep- tember). Annual precipitation in the area av- erages 3,100 mm, and daily temperatures av- erage 3.2° C in January and 15.6° C in July (Environment Canada Climate Data Services). Vegetation sampling. — I sampled vegeta- tion during 1995 within 20-m-radius circular plots (0.13 ha) using a procedure modified from James and Shugart (1970). I accounted for the large size of trees locally by increasing the plot radius (Mueller-Dombois and Ellen- berg 1974, Bryant et al. 1993). To improve the accuracy of visual estimation over a large area, each plot was divided into four quadrats. I sampled vegetation in each of the four quad- rats and then calculated means of the four quadrats for each variable. Plots were placed at three stations 150 m apart along two 500- m transects: one in riparian and one in upland habitat. Transects were oriented parallel to the river, 20 m (riparian) and 1 60 m (upland) from the river, for a total of six plots per site. Be- cause previous studies indicate that both flo- ristics and structural attributes play roles in avian habitat selection (MacArthur and Mac- Shirley • HABITAT USE BY RIPARIAN AND UPLAND BIRDS 247 Arthur 1961, Holmes and Robinson 1981, Robinson and Holmes 1984), I focused on 10 variables representing broad measures of veg- etation characteristics: density of deciduous and coniferous trees, snag density, volume of coarse woody debris (CWD), species richness, total percent cover of all shrubs and forbs, and percent cover of the two dominant shrubs (salmonberry and blueberry). Density (num- ber/ha) was recorded for coniferous trees, de- ciduous trees, and snags within the entire 20- m-radius plot. Trees <3 m in height and ferns were treated as shrubs. Richness and percent cover of shrubs was sampled in a 10-m-radius subplot nested within 20-m circular plots. Richness and percent cover of forbs was sam- pled using four l-m^ quadrats placed at the center of shrub plots. CWD, defined as fallen logs >10 cm in diameter, was sampled at the point of intersection along the circumference of 20-m plots; I recorded diameter and length to calculate volume (m^/ha) of CWD (Van Wagner 1968, Thomas et al. 1979). Bird sampling. — Details of bird sampling can be found in Shirley (2002). Briefly, birds were censused using a full-plot, area-search method (Slater 1994). A 9-ha grid was estab- lished at each site by running a 450-m line parallel and adjacent to the river’s edge and nine perpendicular lines extending 200 m from the river. Grid lines were set 50 m apart and flagged at 25-m intervals. Censusing was conducted at each site by at least two observ- ers who walked the grid lines from 05:00 to 10:00 (PST) on days without rain or high winds. We censused birds at each site four times each breeding season from 1 May to 15 July so that each site was censused once ap- proximately every 2 weeks. Birds of prey and I flyovers were not included in the censuses. I varied the order in which sites were sampled, and three to four observers rotated among j sites and grid lines. To avoid double-counting, I vocal and visual observations were recorded I on site maps that were later evaluated to cal- I dilate number and relative abundance of bird species with respect to distance from the river. The numbers of observations over the four censuses in each year were averaged to pro- vide a mean number of species and individu- als per species for each site. 1 categorized ob- servations into four distance categories from the river’s edge (0-50, 51-100, 101-150, and 151-200 m) and calculated relative abundance for each distance category as the abundance averaged over 3 years and four sites. I analyzed bird abundances by selected guilds and by individual species. I focused the guild analysis on two guilds that I predicted would show a gradient in abundance from ri- parian to upland: riparian specialists and aerial foragers. I assigned species to guilds after Hatler et al. (1978), Ehrlich et al. (1988), and Campbell et al. (1990, 1997) (Appendix). For individual species, I restricted my analysis to those with >5 observations in each year (nine species). When estimating species richness by site, I minimized the impacts of transient spe- cies by excluding species that were likely mi- grants and species observed in only one cen- sus session during each year (Willson and Comet 1996). Habitat associations. — I used Akaike’s In- formation Criterion corrected for small sam- ples (AICJ to select suitable models of asso- ciation between vegetation variables and avian abundance (Burnham and Anderson 2002). I used multiple regression and estimated the re- siduals to model species richness and abun- dance of avian guilds and individual species as a function of vegetation variables. Models were based on a priori hypotheses of those vegetation variables that may be associated with a guild’s or species’ abundance. For each model, I computed AIC^ and AAIC,.. Model likelihoods were standardized to sum to 1 and expressed as Akaike weights (cd). The Akaike weight can be considered as the weight of ev- idence supporting a given model as the best model; the higher the Akaike weight, the stronger the model. To identify plausible mod- els for each species or guild, 1 ranked the Akaike weights of models in a given set to produce evidence ratios (i.e., the weight of the best model divided by that of a given model; Burnham and Anderson 2002). Evidence ra- tios express the likelihood of the selected model relative to other models. Data analysis. — Vegetation attribute and avian abundance data were tested for normal- ity using the Shapiro-Wilks statistic (Shapiro and Wilk 1965) before conducting paired t- tests and ANOVAs. Homogeneity of varianc- es for one-way ANOVA and repeated-mea- sures ANOVA were tested using the Levene and Bartlett-Box /• tests, respectively (Norusis 248 THE WILSON BULLETIN • Vol. 1 17, No. 3, September 2005 1994). Species abundance data that violated these assumptions were either log (y + 1) or rank transformed (Conover and Iman 1982). The a level of significance was set at 0.10 to minimize the high biodiversity cost of making a type II error in resource management deci- sions (Toft and Shea 1983, Dayton 1998). I also define a level of “marginal significance” as 0.15 > P > 0.10. All data were analyzed using SPSS for Windows 6.1.4 (Norusis 1994). To compare riparian and upland means for each of the 10 vegetation variables, I used paired Mests because riparian and upland hab- itats were paired by site for each of the four sites. Rather than correcting for multiple tests using the standard Bonferroni method, which has several disadvantages when gauging the effects of variables in ecological research (Nakagawa 2004), I present effect sizes as rec- ommended by Hurlbert (1994). I evaluated the biological significance of the results using es- tablished criteria (Cohen 1988) where a small effect size = 0.2, medium = 0.5, and large 0.8. To compare abundances (all species com- bined, two guilds, and nine individual species) by distance category from the river and among years, I used a two-way, repeated-mea- sures ANOVA, with year and distance from river’s edge as fixed effects. Because the same sites were censused over 3 years, I treated year as a repeated variable in a model that specified polynomial contrasts to detect linear or quadratic trends over time (Gurevitch and Chester 1986, von Ende 1993). Because there were no significant year effects, data were pooled across years for all comparisons except for American Robin (Turdus migratorius), which showed a significant distance-by-year interaction. I then tested for differences in pooled abundance (one-way ANOVA; all spe- cies combined, two guilds, and eight species) across four 50-m intervals from the river’s edge — with distance from edge as a fixed fac- tor {n = 48). For American Robin, I per- formed the above analysis for each year sep- arately; however, results are presented for all years together (Fig 1). Effect sizes for the one- way ANOVAs were calculated using the Eta squared method (Levine and Hullett 2002). Because there was a significant year effect for species richness, I did not pool data across years. I compared species richness across the four 50-m intervals from the river’s edge and over time using two-way, repeated-measures ANOVA with year and distance from edge as fixed factors {n = 16). RESULTS Vegetation. — Four of 10 measures of veg- etation structure and composition — density of coniferous and deciduous trees, shrub-species richness, and blueberry cover — differed be- tween riparian and upland habitats (Table 1). Effect sizes were medium for coniferous tree density and large for deciduous tree density, reflecting substantial biological differences. Riparian habitats had nearly five times the density of deciduous trees compared with up- land areas, while upland areas had greater co- nifer density and percent blueberry cover. Snag density and salmonberry cover were greater in upland and riparian areas, respec- tively; effect sizes were large, but these dif- ferences were only marginally significant due to a small sample size. CWD and forb cover were not statistically different between habi- tats, but effect sizes were medium and could indicate biological significance. Avian abundance and diversity. — During 1996-1998, I recorded 645 observations of 36 species. For all sites combined, there were >20 observations for 9 species, accounting for 80% of all observations. The five most abundant species were Winter Wren {Troglo- dytes troglodytes). Chestnut-backed Chicka- dee (Poecile rufescens), American Robin, Swainson’s Thrush {Catharus ustulatus), and Pacific-slope Flycatcher {Empidonax dijficil- is). For all years and in each distance interval, assemblages were dominated by these five species, which composed 53—58% of total ob- servations— with only minor variations in their abundance rankings. Except for one for- est interior species (Pacific-slope Flycatcher), these species are forest generalists. Winter Wren and Chestnut-backed Chickadee were the dominant species in upland sections and were replaced, in part, by American Robin and Swainson’s Thrush near the river. Ripar- ian specialists generally occurred close to the river and at low abundances, with the excep- tion of Hammond’s Flycatcher {Empidonax hammondii). Because the dominant species were forest Relative abundance Shirley • HABITAT USE BY RIPARIAN AND UPLAND BIRDS 249 All species combined Winter Wren Chestnut-backed Chickadee American Robin Swainson's Thrush Pacific-slope Flycatcher Golden-crowned Kinglet Varied Thrush 3.5 3.0 2.5 2.0 1.5- 1.0 0.5- 0.0. Hammond's Flycatcher 3.5 3.0 2.5 2.0 1.5- 1.0- 0.5- 00 Hairy Woodpecker 0-50 51-100 101-150 151-200 Distance from river (m) 0-50 jn. 51-100 n [i. 101-150 151-200 FIG. 1. Relative abundance (mean number of ob.servationsAsite/year) and .standard deviations (error bars) at 5()-m intervals from the river’s edge for (A) all species combined. (B) riparian specialists, (C) aerial foragers, (D) Winter Wren, (E) Che.stnut-backed Chickadee, (F) American Robin, (G) Swainson's Thrush, (II) I’acitic- slope Flycatcher, (I) Golden-crowned Kinglet, (I) Varied Thrush. (K) Hammond’s Flycatcher, and (L) Hairy Woodpecker, 1996-1998, western Vancouver Island, British Columbia. Canada (;/ 48). 250 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 TABLE 1. Vegetation characteristics of riparian and upland habitats, western Vancouver Island, British Columbia, 1995. Of 10 variables, four (deciduous and coniferous tree densities, shrub species richness, and percent cover of blueberry species) differed {P < 0.10) between riparian and upland habitats (n = 12 for all tests). Variable Riparian mean (SD) Upland mean (SD) Paired Mest p Effect size® Coniferous trees (no./ha) 247 (166) 356 (140) -1.83 0.095*’ -0.45 Deciduous trees (no./ha) 288 (102) 59 (37) 4.06 0.002*’ 0.79 Snags (no./ha) 72 (41) 134 (96) -1.77 0.1 0‘’ -0.88 Shrub cover (%) 27 (6) 25 (6) 0.80 0.44 0.06 Shrub richness (no. of species) 6 (2) 5 (2) 2.45 0.092*’ 0.17 Salmonberry cover (%) 8 (7) 3 (3) 1.65 0.13-’ 0.56 Blueberry cover (%) 2 (3) 5 (5) -2.37 0.098*’ -1.53 Forb cover (%) 44 (24) 57 (17) -0.80 0.48 -0.38 Forb richness (no. of species) 11 (3) 9 (4) 1.51 0.23 0.06 CWD (m3/ha) 2,512 (208) 3,549 (1,512) -0.94 0.37 -0.41 ^Effect size, measured as (W] - m2)lm\, where W] = mean in riparian habitat and m2 = mean in upland habitat (after Hurlbert 1994). ^ Bold-faced values denote significance at P < 0.10. ‘^Marginally significant (0.15 > P > 0.10). generalists, total abundance did not differ with distance from the river (F344 = 1.26, P = 0.30; Fig. lA). As expected, abundances of riparian specialists and aerial foragers de- clined with distance from the river (Fig. IB, C; riparian specialists: F344 = 7.98, P < 0.001; aerial foragers: F344 = 5.23, P = 0.027). Of the nine species for which I had sufficient data for analysis, only two varied significantly in abundance across the distance intervals: Swainson’s Thrush (F344 = 2.85, P = 0.10; Fig. IG) and Hammond’s Flycatcher (F344 = 11.74, P = 0.001; Fig. IK) were more common near rivers (all other species: P ^ 0.31, effect sizes < 0.07). Species richness did not differ with distance from the river (F3 ,2 = 0.15, P = 0.93) and there was no significant interaction between distance and year (Fe,24 - 0.61, P - 0.62). Species richness, however, differed among years (F224 = 6.28, P — 0.028); 14% more species were detected in 1997 than in 1996 and 1998 (Fig. 2). Habitat associations. — For most bird spe- cies, associations with specific vegetation at- tributes were stronger than with distance from the river. The best model for aerial forager abundance was one showing a negative rela- tionship with conifer density (Table 2). This model was strongly supported (co, = 0.850), 0-50 51-100 101-150 151-200 Distance from river (m) FIG. 2. Means and standard deviations (error bars) of avian species richness at 50-m intervals from the river’s edge, 1996-1998, western Vancouver Island, British Columbia, Canada. Shirley • HABITAT USE BY RIPARIAN AND UPLAND BIRDS 251 TABLE 2. Habitat model selection using Akaike’s Information Criterion for abundance of avian guilds and species in undisturbed forest sites, western Vancouver Island, British Columbia, 1996-1998. Selected models with the highest likelihood are shown. Secondary models are included if they were nearly equal to the first model. Guild or species Model^ AICc‘’ AAICe'= Kd CO^ Aerial foragers CT -5.089 0.000 3 0.850 Riparian specialists DI 27.940 0.000 3 0.244 SA 28.221 0.281 3 0.212 SH 28.444 0.504 3 0.190 SR 28.911 0.971 3 0.150 American Robin CT 27.795 0.000 3 0.405 Chestnut-backed Chickadee CT 25.831 0.000 3 0.387 SN 25.885 0.054 3 0.376 Golden-crowned Kinglet CT 16.730 0.000 3 0.334 Hammond’s Flycatcher DI 20.110 0.000 3 0.396 SH 20.165 0.554 3 0.385 Hairy Woodpecker CT 6.963 0.000 3 0.533 Pacific-slope Flycatcher CT 22.379 0.000 3 0.545 Swainson’s Thrush VA 21.764 0.000 3 0.266 DT 21.932 0.168 3 0.244 CT 22.065 0.301 3 0.229 Varied Thrush SN 9.212 0.000 3 0.457 Winter Wren CT 28.025 0.000 3 0.311 ^ CT - density of coniferous trees, DI = distance from river, DT = density of deciduous trees, SA = percent salmonberry cover, SH = percent shrub cover, SN = snag density, SR = shrub species richness, VA = percent blueberry spp. cover. ^ Akaike’s Information Criterion corrected for small sample sizes. AAICf = difference between best model and model with minimum AIC,.. ^ Number of parameters. ® 0), = Akaike weight. being 14 times more likely than the second- best model in the set. Abundance of riparian specialists was predicted equally by four sin- gle-variable models showing positive relation- ships with salmonberry, percent shrub cover, and shrub species richness, as well as a neg- ative relationship with distance from the river. Support for all four models, however, was weak (all four oj, < 0.250) and the best model was only 2.5 times more likely than the next- best model in the set. The abundances of four species (American Robin, Hairy Woodpecker \Picoides villosus]. Pacific-slope Flycatcher, and Winter Wren) were best predicted by single-variable models showing negative relationships with conifer density (Table 2). Models for Hairy Wood- pecker and Pacific-slope Flycatcher had mod- erate support (to, = 0.533 and oj, = 0.545), being 3-4 times more likely than the second- best models in the sets. The models for Amer- ican Robin and Winter Wren had weaker sup- port (to, = 0.405 and to, = 0.31 1) anti were only twice as likely as the sect)ntl nuKlcl in the .set. Chestnut-backed Chickatlee abun- dance was best predicted by two single-vari- able models showing negative relationships with conifer (o\ = 0.387) and snag densities (to, = 0.376); both models had almost equal support and were 3 times more likely than the third model in the set. Golden-crowned King- let (Regulus satrapa) abundance was best pre- dicted by a model showing a positive rela- tionship with conifer density; however, this model was relatively weak (to, = 0.334) and only 1.3 times more likely than the second model in the set. Hammond’s Flycatcher abundance was best predicted by two single- variable models representing a negative rela- tionship with distance from the river (to, = 0.396) and a positive relationship with percent shrub cover (to, = 0.385). Both models had almost equal support and were 5 times as like- ly as the third mt)tlel in the set. Swainson's Thrush abundance was best predicted by three single-variable mtHlels showing negative re- latit)nships with percent blueberry cover (to, = 0.266) and density of ct)niferous trees (to, = 0.244) anti a pt)sitive relatit)uship with density t)f tlecitlut)us trees (to, = 0.229). The models 252 THE WILSON BULLETIN • Vol. 1 17, No. 3, September 2005 had almost equal support, although support for any one was quite weak. The best model for Varied Thrush {Ixoreus naevius) abundance showed a positive relationship with snag den- sity (o), = 0.457). This model had moderate support, being 4 times as likely as the second model in the set. DISCUSSION Species diversity and abundance along the riparian gradient. — Contrary to my original predictions, species abundance and diversity of birds were similar along a distance gradient away from the river. Although species rich- ness varied among years, total abundance re- mained similar during the study. Other studies in coniferous forests of the Pacific Northwest have also found that riparian areas do not sup- port higher numbers of bird species or indi- viduals (McGarigal and McComb 1992, Mur- ray and Stauffer 1995, Pearson and Manuwal 2001). In contrast, studies in more arid or ag- ricultural environments (Carothers et al. 1974, Stevens et al. 1977, Wauer 1977, Stauffer and Best 1980) found large differences in diversity and abundance between riparian and upland habitats. McGarigal and McComb (1992) pro- posed three hypotheses to account for the re- gional difference in these patterns: (1) high stream density and availability of water in up- land areas in the Pacific Northwest, (2) a less pronounced microclimatic gradient (moderat- ed by maritime influences) in northwestern forests, and (3) a more subtle transriparian gradient in vegetation structure. Higher rain- fall and less variation in annual temperatures on western Vancouver Island compared with Washington and Oregon may produce an even less pronounced transriparian gradient. In this study, riparian habitats had greater densities of deciduous trees, and the understo- ry was dominated by salmonberry. In contrast, upland areas had higher densities of conifer- ous trees, and blueberry species dominated the shrub understory; uplands also tended to have greater snag densities. While low statistical power may have limited my ability to detect statistically significant differences in some at- tributes, my results are consistent with those of other studies that evaluated vegetation structure across the transriparian gradient of forests in the Pacific Northwest (McGarigal and McComb 1992, Pearson and Manuwal 2001). McGarigal and McComb (1992) attri- buted lower bird species richness in riparian as opposed to upland areas to the scarcity of conifers found along streams; however, in my study, conifers were not as scarce along ri- parian areas, perhaps accounting for the sim- ilarity in species richness between the two habitats. The lack of a strong gradient in veg- etation structure from riparian to upland is also reflected in the distribution of the most common bird species. Abundances of eight of the most common bird species, as well as abundance of the aerial foraging guild, were associated most closely with densities of cer- tain canopy and understory species rather than distance from the river. Complex topography, combined with consistently moist conditions, provides suitable habitat for most species across the riparian-upland gradient that I stud- ied, and it probably accounts for the lack of strong riparian effects at the community level. The large fourth- or fifth-order streams and rivers in my study area contrast with the smaller, second-order streams that were the fo- cus of some previous studies in northern for- ests (McGarigal and McComb 1992, Wiebe and Martin 1998). In those studies, riparian forests supported equal or fewer species and individuals compared with surrounding up- lands (McGarigal and McComb 1992, Wiebe and Martin 1998). Studies of larger-order streams, however, have indicated that they support denser, more complex riparian vege- tation communities and greater avian density, species richness, and abundance (Knopf 1985, Lock and Naiman 1998). Lock and Naiman (1998) found greater species richness and abundance along larger rivers where the ri- parian habitat contained a higher ratio of de- ciduous to coniferous vegetation; in my study, however, avian species richness and abun- dance were similar across the riparian to up- land gradient, even along larger streams. Most species used both riparian and upland habitats, whereas only a few species specialized in ei- ther habitat. In northwestern forests, these specialists represented a small fraction of the overall community. Habitat selection. — Of the 36 species re- corded, five occurred only near the river. Four of these riparian specialists — Common Mer- ganser {Mergus merganser), American Dipper (Cinclus mexicanus). Belted Kingfisher {Cer- Shirley • HABITAT USE BY RIPARIAN AND UPLAND BIRDS 253 yle alcyon), and Spotted Sandpiper (Actitis macularius) — depend on stream invertebrates and/or fish as food resources and they nest in adjacent riparian vegetation or riverbanks (Enns et al. 1993, Campbell et al. 1997). The remaining species, Willow Flycatcher (Empi- donax traillii), rarely occurs in mature forest except in riparian areas. In the coastal western hemlock zone. Willow Flycatchers more com- monly occur in marshes and early succession- al clearcuts (5-10 years of age) associated with young red alder and willow trees (Enns et al. 1993, Campbell et al. 1997). Five species occurred only at single sites in upland sections of forest: Fox Sparrow {Pas- serella iliaca), Hutton’s Vireo (Vireo huttoni), Olive-sided Flycatcher (Contopus cooperi). Spotted Towhee (Pipilo maculatus), and Yel- low Warbler {Dendroica petechia). All of these species are rare in mature forests and may select large patches of open, deciduous vegetation in forest interiors. As predicted, I found that aerial foragers declined in abundance with increasing dis- tance from the river. Aerial foragers include Hammond’s Flycatcher, a species that occu- pies a wide variety of habitats (Willson and Comet 1996). Throughout much of the Pacific Northwest, the species is an upslope specialist that is associated strongly with conifers at sites characterized by relatively open canopies (Sakai and Noon 1991, McGarigal and Mc- Comb 1992); however, farther north in Alaska it favors deciduous stands (Willson and Comet 1996), and in the forests of Vancouver Island (Waterhouse and Harestad 1999, Shirley 2002) and southeastern British Columbia (Kinley and Newhouse 1997), this species is largely restricted to mixed riparian forests that include large deciduous trees and conifers. Whereas Hammond’s Flycatcher may use ri- parian habitat, it is sympatric with the Pacific- slope Flycatcher in old-growth forest (Camp- bell et al. 1997) and its distribution may re- flect some habitat partitioning between the two species. In southern Colorado, where Hammond’s and Cordilleran {Empidonax oc- cidentalis) flycatchers co-occur, Hammond’s Flycatcher densities were approximately one- half those of the Cordilleran Flycatcher (Bea- ver and Baldwin 1975). In these areas of over- lap, Hammond’s Flycatcher inhabited aspen habitat, while the Cordilleran f lycatcher used aspen-conifer habitat. Behavioral observations by Sakai and Noon (1991) suggested that some competition likely occurs between the Hammond’s and Pacific-slope flycatchers, but it does not result in competitive exclusion of one species by the other. Pacific-slope Fly- catcher abundance differed little along the gradient of distance away from the river, a re- flection of its association with large conifer trees in both riparian and upland habitats. In- terestingly, studies farther south in the Pacific Northwest (McGarigal and McComb 1992, Pearson and Manuwal 2001) reported that Pa- cific-slope Flycatchers are associated with ri- parian habitats, whereas Hammond Flycatch- ers are associated with upland habitats. The reason for this difference is unclear, but may relate to differences in species composition and size distribution of trees in the two forest habitats. For example, in the previous studies, large-diameter conifers required by Ham- mond’s Flycatchers (Sakai and Noon 1991), such as Douglas-fir (Pseudotsuga menziesii), occur in greater numbers in upland forests. Several of the dominant species in my study, including Chestnut-backed Chickadee and Golden-crowned Kinglet, showed associ- ations with conifer or snag density. An excep- tion was the Swainson’s Thrush, which, al- though a forest generalist, was more abundant in riparian habitat. This species is widespread on the west coast (Campbell et al. 1997) and often forages in salmonberry and devil’s club in riparian habitats. The positive association with deciduous trees suggests that these struc- tures or some other closely associated vege- tation may be an important influence on hab- itat selection for this species. Furthermore, virtually all Swainson’s Thrush nests encoun- tered incidentally during surveys (// = 8) were found in salmonberry (SMS pers. obs.), sug- gesting a strong association with this shrub for nesting habitat and/or food. Management implications. — Patterns of avi- an diversity and abundance in riparian com- munities often have been explained by dra- matic gradients in microclimate and vegeta- tion structure or composition (Carothers ct al. 1974, Stevens et al. 1977, Dickson 1978, Sza- ro 1980). Where these gradients arc subtle, as in forests ol the Pacific Northwest, the pat- terns disappear (Wiebe and Martin 1998, Pear- son and Manuwal 2001) or they may re- 254 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 verse — upland areas supporting greater diver- sity and abundance than riparian areas (McGarigal and McComb 1992). Northwest forests generally lack a strong microclimatic gradient from riparian to upland (Brosofske et al. 1997), and ephemeral streams or ponds oc- cur in virtually every upland area. These fac- tors create a fine-scale habitat mosaic in which patches dominated by conifers are inter- spersed with deciduous trees and shrubs that provide habitat for species more typical of de- ciduous-tree-dominated riparian areas. Recent discussions of land management practices to preserve native biodiversity of forest species include using a landscape-level approach that protects both riparian and up- land habitats to ensure connectivity across the landscape (McGarigal and McComb 1992, Wiebe and Martin 1998). Maintaining connec- tivity may prevent isolation of remnant forest patches (Fahrig and Merriam 1985, Saunders and de Rebeira 1991, Gonzalez 2000); how- ever, the lack of upland specialists in my study argues against placing too much emphasis on upland areas per se. Unmanaged riparian areas not only provide habitat for those few species that associate with specific features at the riv- er’s edge, they also contain habitat elements such as large conifers and snags important to many common forest species. My study was limited in several ways that should be considered in the development of land use plans. First, although the contrast be- tween riparian and upland habitats is known to be subtle in the moist forests of the Pacific Northwest (McGarigal and McComb 1992, Pearson and Manuwal 2001), differences in structure and composition of vegetation in my study may have been obscured by the small sample size and resulting lack of statistical power. Statistically, several of the vegetation characteristics that I measured were margin- ally or non-significant, but their medium to large effect sizes indicate possible biological significance. Second, comparisons in this study were limited to measures of avian abun- dance. Future work should focus on measures of relative fitness or productivity in the two habitats. Third, my study was conducted dur- ing the breeding season; work is also needed to assess avian distributions during other sea- sons, as the relative value of riparian and up- land habitats may differ between periods of migration and other seasons (Harris 1984, Wiebe and Martin 1998). For example, ripar- ian habitats may provide critical habitat for Neotropical migrants as they travel between their wintering and breeding grounds (Stevens et al. 1977, Finch 1991), and riparian habitat may be important for the survival and popu- lation stability of migratory species during the breeding season. The diversity and density of some migrants may be greater in riparian cor- ridors because they are easy to follow and/or provide diverse foraging habitats (Wiens 1989, Wiebe and Martin 1998). ACKNOWLEDGMENTS I thank K. G. Beal, D. J. Huggard, L. G. Barrett- Lennard, and two anonymous reviewers for comments on earlier drafts of this manuscript, and K. T. Port, S. Frioud, S. L. Hicks, D. Lewis, R. Maraj, G. Matscha, F. Pouw, and S. Weber for their hard work in the field. I also thank G. Matscha and C. M. Ferguson for their help in processing the vegetation data. I am grateful to W. French and the engineering group at Weyerhaeuser Canada for their cooperation in locating field sites. Fi- nancial support was provided by the Habitat Conser- vation Trust Fund, Forest Renewal British Columbia, a University of British Columbia graduate fellowship to SMS, and a Natural Sciences and Engineering Re- search Council operating grant to J. N. M. Smith. LITERATURE CITED Anthony, R. G., G. A. Green, E. D. Forsman, and S. K. Nelson. 1996. Avian abundance in riparian zones of three forest types in the Cascade Moun- tains, Oregon. Wilson Bulletin 108:280-291. Beaver, D. L. and R H. Baldwin. 1975. Ecological overlap and the problem of competition and sym- patry in the Western and Hammond’s flycatchers. Condor 77:1-13. Brinson, M. M., B. L. Swift, R. C. Plantico, and J. S. Barclay. 1981. Riparian ecosystems: their ecology and status. U.S. Department of the Inte- rior, Fish and Wildlife Service, Kearneysville, West Virginia. Brosofske, K. D., J. Chen, R. J. Naiman, and J. F. Franklin. 1997. Harvesting effects on microcli- matic gradients from small streams to uplands in western Washington. Ecological Applications 7: 1188-1200. Bryant, A. A., J. P. Savard, and R. T. McLaughlin. 1993. Avian communities in old-growth and man- aged forests of western Vancouver Island, British Columbia. Technical Report Series, no. 167. Ca- nadian Wildlife Service, Nanaimo, British Colum- bia, Canada. Bull, E. V. 1978. Specialized habitat requirements of birds: snag management, old growth, and riparian habitat. Pages 74-82 in Proceedings of the work- shop on nongame bird habitat management in the Shirley • HABITAT USE BY RIPARIAN AND UPLAND BIRDS 255 coniferous forests of the western United States (R. M. DeGraaf, Tech. Coord.). General Technical Re- port PNW-64, USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, Oregon. Burnham, K. P. and D. R. Anderson. 2002. Model selection and multimodel inference, 2nd ed. Springer- Verlag, New York. Campbell, R. W. 1990. The birds of British Columbia. Royal British Columbia Museum, Victoria, and Canadian Wildlife Service, Ottawa, Ontario, Can- ada. Campbell, R. W., N. K. Da we, I. McTaggart-Cowan, J. M. Cooper, G. W. Kaiser, M. C. E. McNall, AND G. E. J. Smith. 1997. The birds of British Columbia, vol. 3: flycatchers through vireos. Uni- versity of British Columbia Press, Vancouver, Canada. Carothers, S. W., R. R. Johnson, and S. W. Aitchi- SON. 1974. Population structure and social orga- nization of southwestern riparian birds. American Zoologist 14:97-108. Cohen, J. 1988. Statistical power analysis for the be- havioral sciences, 2nd ed. Erlbaum, Hillsdale, New Jersey. Conover, W. J. and R. L. Iman. 1982. Analysis of covariance using the rank transformation. Bio- metrics 38:715-724. Dayton, P. K. 1998. Reversal of the burden of proof in fisheries management. Science 279:821-822. Dickson, J. G. 1978. Forest bird communities of the bottomland hardwoods. Pages 66-73 in Proceed- ings of the workshop: management of southern forests for nongame birds (R. M. DeGraaf, Ed.). General Technical Report SE-14, USDA Forest Service, Southeastern Forest Experiment Station, Atlanta, Georgia. Ehrlich, P. R„ D. S. Dobkin, and D. Wheye. 1988. The birder’s handbook: a field guide to the natural history of North American birds. Simon and Schuster, New York. Enns, K. a., E. B. Peterson, and D. S. McLennan. 1993. Impacts of hardwood management on Brit- ish Columbia wildlife: problem analysis. Forestry Canada Pacific Forestry Centre, Victoria, British Columbia, Canada. Fahrig, L. and G. Merriam. 1985. Habitat patch con- nectivity and population survival. Ecology 66: 1762-1768. Finch, D. M. 1991. Population ecology, habitat re- quirements, and conservation of Neotropical mi- gratory birds. General Technical Report RM-205, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Col- orado. Gonzalez, A. 2()()(). Community relaxation in frag- mented landscapes: the relation between species richness, area and age. Ecology Letters 3:441- 448. Gray, L. J. 1993. Response of insectivorous birds to emerging aquatic insects in riparian habitats of a tallgrass prairie stream. American Midland Natu- ralist 129:288-3(M). Gurevitch, j. and S. T. Chester. 1986. Analysis of repeated measures experiments. Ecology 67:251- 255. Harris, L. D. 1984. The fragmented forest. University of Chicago Press, Chicago, Illinois. Hatler, D. E, R. W. Campbell, and A. Dorst. 1978. Birds of Pacific Rim National Park. British Co- lumbia Provincial Museum, Victoria, Canada. Holmes, R. T. and S. K. Robinson. 1981. Tree species preferences of foraging insectivorous birds in a northern hardwoods forest. Oecologia 48:31-35. Hurlbert, S. H. 1994. Old shibboleths and new syn- theses. Trends in Ecology and Evolution 9:495- 496. James, F. C. and H. H. Shugart. 1970. A quantitative method of habitat description. Audubon Field Notes 24:727-736. Kinley, T. and N. j. Newhouse. 1997. Relationship of riparian reserve zone width to bird density and diversity in southeastern British Columbia. North- west Science 71:75-86. Klinka, K., j. Pojar, and D. V. Meidinger. 1991. Re- vision of biogeoclimatic units of coastal British Columbia. Northwest Science 65:32-47. Knopf, F. L. 1985. Significance of riparian vegetation to breeding birds across an altitudinal dine. Pages 105-111 in Riparian ecosystems and their man- agement: reconciling conflicting uses (R. R. John- son, C. D. Ziebell, D. R. Patton, P. F. Folliott, and R. H. Hamre, Eds.). General Technical Report RM-120, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Col- lins, Colorado. Knopf, F. L., R. R. Johnson, T. Rich, F. B. Samson, AND R. C. SzARO. 1988. Conservation of riparian ecosystems in the United States. Wilson Bulletin 100:272-284. Knopf, F. L. and F. B. Samson. 1994. Scale perspec- tives on avian diversity in western riparian eco- systems. Conservation Biology 8:669-676. Kuehne, R. a. 1962. A classification of streams, illus- trated by fish distribution in an eastern Kentucky creek. Ecology 43:608-614. LaRue, P, L. Belanger, and J. Huot. 1995. Riparian edge effects on boreal balsam fir bird communi- ties. Canadian Journal of Forest Research 25:555- 566. Levine, T. R. and C. R. Hullett. 2002. Eta squared, partial eta .squared, and misreporting of effect size in communication re.search. Human Communica- tion Re.search 28:612-625. L(X’K, P. a. and R. j. Naiman. 1998. Effects of stream size on bird community structure in coastal tem- perate forests of the Pacific Northwest. USA. Jour- nal of Biogeography 25:773-782. MacAkihur, R. H. and j. W. Mac'Akthur. 1961. On bird species diversity. Ficology 42:594-598. McGakigal. K. and W. C. Mc Comb. 1992. Streamside versus upslope breeding bird communities in the central Oregon Coast Range. Journal of Wildlife Management 56:10 23. Mui:lli:k-D()MM()IS. D. and H. Iu lenberg. 1974. Aims 256 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 and methods of vegetation ecology. Wiley, New York. Murakami, M. and S. Nakano. 2002. Indirect effect of aquatic insect emergence on a terrestrial insect population through predation by birds. Ecology Letters 5:333-337. Murray, N. L. and D. E Stauffer. 1995. Nongame bird use of habitat in central Appalachian riparian forests. Journal of Wildlife Management 59:78— 88. Naiman, R. J., H. Decamps, and M. Pollock. 1993. The role of riparian corridors in maintaining re- gional biodiversity. Ecological Applications 3: 209-212. Nakagawa, S. 2004. A farewell to Bonferroni: the problems of low statistical power and publication bias. Behavioral Ecology 15:1044-1045. Norusis, M. J. 1994. SPSS advanced statistics 6.1. SPSS, Inc., Chicago, Illinois. Nuszdoreer, E and R. Boettger. 1994. Biogeocli- matic units of the Vancouver Eorest Region: southern Vancouver Island and Sunshine Coast. Province of British Columbia, Ministry of Eorests, Vancouver, Canada. Pearson, S. and D. A. Manuwal. 2001. Breeding bird response to riparian buffer width in managed Pa- cific Northwest Douglas-fir forests. Ecological Applications 11:840-853. Raedeke, K. j. 1988. Streamside management: riparian wildlife and forestry interactions. Institute of For- est Resources, University of Washington, Seattle. Ranney, j. W, M. C. Bruner, and J. B. Levenson. 1981. The importance of edge in the structure and dynamics of forest islands. Pages 67-96 in Forest island dynamics in man-dominated landscapes (R. L. Burgess and D. M. Sharpe, Eds.). Springer- Ver- lag. New York. Robinson, S. K. and R. T. Holmes. 1984. Effects of plant species and foliage structure on the foraging behavior of forest birds. Auk 101:672-684. Sakai, H. F. and B. R. Noon. 1991. Nest-site charac- teristics of Hammond’s and Pacific-slope flycatch- ers in northwestern California. Condor 93:563- 574. Saunders, D. A. and C. P. de Rebeira. 1991. Values of corridors to avian populations in a fragmented landscape. Pages 221-240 in The role of corridors (D. A. Saunders and R. J. Hobbs, Eds.). Surrey Beatty & Sons, Chipping Norton, New South Wales, Australia. Shapiro, S. S. and M. B. Wilk. 1965. An analysis of variance test for normality (complete samples). Biometrika 52:591-611. Shirley, S. 2002. Forest fragmentation and regrowth: use of riparian and upland forest by birds in man- aged and unmanaged mature coastal British Co- lumbia rainforest. Ph.D. dissertation. University of British Columbia, Vancouver, Canada. Slater, P. J. 1994. Factors affecting the efficiency of the area search method of censusing birds in open forests and woodlands. Emu 94:9-16. Staufeer, D. E and L. B. Best. 1980. Habitat selec- tion by birds of riparian communities: evaluating effects of habitat alterations. Journal of Wildlife Management 44:1-15. Stevens, L. E., B. T. Brown, J. M. Simpson, and R. R. Johnson. 1977. The importance of riparian habitat to migrating birds. Pages 156-164 in Im- portance, preservation and management of ripari- an habitat: a symposium (R. R. Johnson and D. A. Jones, Eds.). General Technical Report RM- 43, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Col- orado. SzARO, R. C. 1980. Factors influencing bird popula- tions in southwestern riparian forests. Pages 403- 418 in Workshop proceedings: management of western forests and grasslands for nongame birds (R. M. DeGraff and N. G. Tilghman, Eds.). Gen- eral Technical Report INT-86, USDA Forest Ser- vice, Intermountain Forest and Range Experiment Station, Ogden, Utah. Thomas, J. W., C. Maser, and J. E. Rodiek. 1979. Riparian zones. Pages 40—47 in Wildlife habitats in managed forests: the Blue Mountains of Oregon and Washington (J. W. Thomas, Ed.). USDA Ag- riculture Handbook, no. 553. U.S. Government Printing Office, Washington, D.C. Toft, C. A. and P. J. Shea. 1983. Detecting commu- nity-wide patterns: estimating power strengthens statistical inference. American Naturalist 122: 618-625. Van Wagner, C. E. 1968. The line intersect method in forest fuel sampling. Forest Science 14:20-26. VON Ende, C. N. 1993. Repeated-measures analysis: growth and other time-dependent measures. Pages 113-137 in Design and analysis of ecological ex- periments (S. M. Scheiner and J. Gurevitch, Eds.). Chapman and Hall, New York. Waterhouse, F. L. and A. S. Harestad. 1999. The value of riparian forest buffers as habitat for birds in the coastal western hemlock zone, British Co- lumbia: a pilot study. Research Section, Vancou- ver Forest Region, British Columbia Ministry of Forests, Nanaimo, Canada. Wauer, R. R. 1977. Significance of Rio Grande ripar- ian systems upon the avifauna. Pages 165—174 in Importance, preservation and management of ri- parian habitat: a symposium (R. R. Johnson and D. A. Jones, Eds.). General Technical Report RM- 43, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Col- orado. WiEBE, K. AND K. Martin. 1998. Seasonal use by birds of stream-side riparian habitat in coniferous forest of northcentral British Columbia. Ecography 21: 124-134. Wiens, J. A. 1989. The ecology of bird communities. Cambridge University Press, Cambridge, United Kingdom. Willson, M. F. and T. A. Comet. 1996. Bird com- munities of northern forests: patterns of diversity and abundance. Condor 98:337—349. Shirley • HABITAT USE BY RIPARIAN AND UPLAND BIRDS 257 APPENDIX. Guild classification of avian species (after Hatler et al. 1978; Ehrlich et al. 1988; Campbell et al. 1990, 1997). Guild/Species Aerial foragers Hammond’s Flycatcher (Empidonax hammondii) Olive-sided Flycatcher {Contopus cooperi) Pacific-slope Flycatcher {Empidonax difficilis) Willow Flycatcher {Empidonax traillii) Riparian specialists American Dipper {Cinclus mexicanus) Belted Kingfisher {Ceryle alcyon) Common Loon {Gavia immer) Common Merganser {Mergus merganser) Hammond’s Flycatcher {Empidonax hammondii) Spotted Sandpiper {Actitis macularius) Warbling Vireo {Vireo gilvus) Yellow Warbler {Dendroica petechia) Wilson Bulletin 1 17(3):258— 269, 2005 DENSITY AND DIVERSITY OE OVERWINTERING BIRDS IN MANAGED FIELD BORDERS IN MISSISSIPPI MARK D. SMITH,i 2 pHILIP J. BARBOUR, ^ L. WES BURGER, JR.,i AND STEPHEN J. DINSMOREi ABSTRACT. — Grassland bird populations are sharply declining in North America. Changes in agricultural practices during the past 50 years have been suggested as one of the major causes of this decline. Field-border conservation practices encouraged by the U.S. Department of Agriculture’s National Conservation Buffer Initia- tive meet many of the needs of sustainable agriculture and offer excellent opportunities to enhance local grassland bird populations within intensive agricultural production systems. Despite the abundant information on avian use of, and reproductive success in, strip habitats during the breeding season, few studies have examined the potential value of field borders for wintering birds. We planted 89.0 km of field borders (6.1 m wide) along agricultural field edges on one-half of each of three row crop and forage production farms in northeastern Mississippi. We sampled bird communities along these field edges during February-March 2002 and 2003 using line-transect distance sampling and strip transects to estimate density and community structure, respectively. We used Program DISTANCE to estimate densities of Song (Melospiza melodia). Savannah (Passerculus sand- wichensis), and other sparrows along bordered and non-bordered transects while controlling for adjacent plant community. Greater densities of several sparrow species were observed along most bordered transects. However, effects of field borders differed by species and adjacent plant community types. Diversity, species richness, and relative conservation value (a weighted index derived by multiplying species-specific abundances by their re- spective Partners in Flight conservation priority scores) were similar between bordered and non-bordered edges. Field borders are practical conservation tools that can be used to accrue multiple environmental benefits and enhance wintering farmland bird populations. Provision of wintering habitat at southern latitudes may influence population trajectories of short-distance migrants of regional conservation concern. Received 4 October 2004, accepted 13 June 2005. Grassland birds are one of the most sharply declining groups of birds in North America (Knopf 1994, Herkert 1995, Peterjohn and Sauer 1999). Grassland birds experienced a 1.1% per year decline from 1966 to 2002 in the U.S. and a 2.3% per year decline in the southeastern (U.S. Fish and Wildlife Service Region 4) U.S. (Sauer et al. 2003). Many grassland species are now associated closely with agricultural production systems because most (>80%) of the native grasslands in North America have been converted to other uses (Samson and Knopf 1994, Noss et al. 1995, Hunter et al. 2001), principally agricul- tural production. Although agriculture facili- tated range expansions for several grassland species through clearing of forested land (As- kins 1999, Arcese et al. 2002), several correl- ative studies now suggest agricultural inten- sification as a leading cause of decline for most grassland birds (Vickery et al. 1999, Blackwell and Dolbeer 2001, Murphy 2003). * Dept, of Wildlife and Fisheries, Box 9690, Missis- sippi State Univ., Mississippi State, MS 39762, USA. ^ Corresponding author; e-mail: msmith@cfr. msstate.edu Numerous changes in production agricul- ture have occurred within the past 50 years, hastening the decline of grassland birds. Most notable has been the shift from diversified, small-scale farms to large-scale, highly spe- cialized, chemical- and capital-intensive monoculture farming systems. This shift has resulted in the loss of field edge, fencerow, and other non-crop herbaceous communities (Rodenhouse et al. 1993, Warner 1994, Ko- ford and Best 1996). Recent changes in Con- servation Reserve Program (CRP) enrollment options (continuous sign-up) now permit par- tial field enrollments, thus encouraging con- servation-oriented production practices (e.g., conservation buffers) without removing an en- tire field from production. Conservation buffer practices, available in several Farm Bill con- servation programs, offer valuable opportuni- ties to create habitat for grassland birds within intensively farmed landscapes. Grassed water- ways, contour grass strips, filter strips, ripar- ian buffers, crosswind trap strips, windbreaks, and shelterbelts are conservation buffer prac- tices used to reduce soil erosion (Dillaha et al. 1989), diminish herbicide and nutrient runoff 258 Smith et al. • OVERWINTERING BIRDS AND FIELD BORDERS 259 into wetlands (Daniels and Williams 1996, Webster and Shaw 1996), and provide wildlife habitat (Bryan and Best 1991, Puckett et al. 1995, Marcus et al. 2000). Within intensively farmed landscapes, con- servation buffers are increasingly the only available semi-permanent grasslands for nest- ing birds (Warner 1994, Koford and Best 1996). Field borders, defined as intentionally managed herbaceous plant communities along crop field edges to provide environmental and wildlife habitat benefits, are another type of conservation buffer practice. However, unlike conservation buffer practices specifically de- signed to filter sediments, field borders may be more broadly applied than simply along downslope edges of fields. Field borders may be established where other conservation buff- er practices do not meet eligibility criteria, are not cost effective or practical, or are not de- sired by the producer. Although herbaceous strip habitats may have limited value as nesting cover because reproductive success is low (Basore et al. 1986, Bryan and Best 1994, Camp and Best 1994), field borders may provide important wintering habitat for numerous short-distance migrants that winter in the southern U.S. Sev- eral studies have documented grassland bird use and reproductive success within other ag- ricultural edge habitats (Best 1983, Johnson and Beck 1988, Best et al. 1990, Sparks et al. 1996); however, no studies have addressed ex- plicitly the importance of field borders. Fur- thermore, most studies of grassland birds have been conducted during the breeding season (Rodenhouse et al. 1993, Herkert et al. 1996, Ryan et al. 1998, Peterjohn 2003). Only Mar- cus et al. (2000), in North Carolina, addressed the benefits of field borders to wintering birds. Ryan et al. (1998) noted the lack of data de- tailing winter bird use of CRP fields, and win- tering habitat requirements and ecology of most grassland birds are poorly known (Vick- ery et al. 1999). Herkert et al. (1996) and Pe- terjohn (2003) contend that the paucity of in- formation on wintering grassland birds limits our ability to develop effective conservation strategies for them. Our objectives were to estimate the effects of field borders on grassland bird density and diversity during the winter in northeastern Mississippi. We also characterized avian com- munity structure in bordered and non-bor- dered fields, relative to adjacent plant com- munities. METHODS Study area. — Our study was conducted on three privately owned farms in Clay and Lowndes counties (88° 32' W, 33° 34' N), lo- cated within the Black Prairie physiographic region of northeastern Mississippi. All farms in the region have a history of agricultural use, most having actively produced crops for >50 years. Primary agricultural production in- cluded soybeans {Glycine max), com {Zea mays), forage, and livestock. Most row-crop fields on all three study farms were tilled in late fall in preparation for spring planting. The farms were selected based on similarities in cropping practices, landscape composition (approximately 60-80% row crop), soil asso- ciations, and landowner cooperation. Grasslands on each farm consisted predom- inantly of perennial, exotic, cool-season for- age grasses (tall fescue, Festuca arundinacea) and warm-season exotics (Bermudagrass, Cy- nodon dactylom, and Bahia grass, Paspalum notatum; Smith 2004). Small remnant and re- introduced stands of native grasses (big blue- stem, Andropogon gerardii; little bluestem, Schizachyrium scoparium\ and broomsedge, A. virginicus) were scattered throughout each farm. Fencerows, drainage ditches, and con- tour filter strips were dominated by tall fescue and Johnson grass {Sorghum halepense). Pe- riodically disturbed areas contained early ser- ai-stage grasses and forbs (paspalum, Paspa- lum spp.; paniegrass, Panicum spp.; giant rag- weed, Ambrosia trifida\ annual marshelder/ sumpweed, Iva annua', Johnson grass; and goldenrod, Solidago spp.). Wooded areas were predominantly oak {Querciis spp.), green ash {Fraxinus pennsylvanica), maple {Acer spp.), hickory {Cary a spp.), sugarberry {Celt is lae- vigata), and eastern redeedar {Juniperus vir- giniamr. Smith 2004). During early spring 2000, we established experimental field borders (6.1 m wide) along row-crop field margins (fencerows, drainage ditches, access roads, and contour filter strips) on one-half of each farm. Mean field size was 26.9 ha (// = 37, range = 2.9-146.9) and mean percentage of the field area given over to field borders was 6.0% (range = 0.5-15.3). 260 THE WILSON BULLETIN • Vol 117, No. 3, September 2005 Overall, field borders (54.3 ha) composed 0.8- I. 3% of the land area of bordered sections of each farm. In return, producers were paid an initial $247. 10/ha sign-up bonus with a $ 123.55/ha/year rental rate for land dedicated to field borders. Producers were required not to mow, treat with herbicide, or disk field bor- ders during the duration of the study. Initially, field borders were seeded with a Kobe lespe- deza {Lespedeza striata) and partridge pea (Chamaecrista fasciculata) mix at rates of II. 2 and 3.4 kg/ha, respectively. Severe drought during the 2000 growing season re- sulted in poor plant growth; therefore, field borders were re-seeded in early 2001. Despite these two attempts to establish field borders, most re-seeded naturally from seed present within the seed bank. During the 2001 grow- ing season, the most common species occur- ring in field borders were morning-glory {Ip- omoea spp.), crabgrass {Digitaria ciliaris), Johnson grass, hemp sesbania (Sesbania ex- altata), yellow nutsedge {Cyperus esculentus), and ragweed {Ambrosia spp.; PJB unpubl. data). Data collection. — We used line-transect dis- tance sampling and strip-transect sampling to estimate density (birds/ha) and diversity, re- spectively, of wintering grassland birds. Geo- referenced aerial photos and Geographic In- formation System (GIS) land cover maps were used to delineate field edges. Field edges were divided into 200-m-long sampling units (tran- sects), with the beginning point of each tran- sect situated so that the vegetation type on the non-agricultural side of the transect was ho- mogenous for the length of the transect. The centerline of each transect was situated along the interface of the original (before field bor- ders implemented) row-crop field and adjacent plant community interface. Transects located adjacent to roadways or those that contained field borders that were disturbed inadvertently (e.g., disked, mowed, sprayed) by producers were not included within this sampling frame. Our sampling frame consisted of 1 10 bordered and 82 non-bordered transects. We then clas- sified each transect based upon combinations of (1) bordered (T) and non-bordered (C) practices on the agricultural side, and by (2) vegetation type (woody [W], herbaceous [G]) and (3) width (strip [S], <30 m of continuous vegetation type; block [B], >30 m of contin- uous vegetation type) on the non-agricultural side. This classification scheme produced eight treatment combinations: TGB, CGB, TGS, CGS, TWB, CWB, TWS, CWS. During winter 2002, we conducted a pilot study to estimate encounter rates along poten- tial transects within each treatment combina- tion. We concluded that >10 200-m transects/ treatment combination would provide suffi- cient numbers of encounters to estimate de- tection functions for several common species and most guilds. Because the amount and structure of grassland and woodland habitats differed dramatically among farms, we were not able to sample all eight treatment combi- nations within any one farm. Therefore, we randomly selected 10-11 transects for each treatment combination from the population of transects available across all three farms ex- cept for the CGB treatment combination. Only seven transects were available for the CGB treatment combination and all were used. We sampled the same transects in both years of study (2002, 2003), with the exception of two TWB transects with field borders that were accidentally disked by the producer after year 1. These two transects were replaced by two other randomly selected TWB transects on the same farm. The field border treatment was assigned randomly to one-half of each of the three farms. Field borders were not assigned ran- domly to individual transects, but rather bor- dered transects were selected randomly from the population of all bordered transects across all farms. Thus, our study was observational with replication. Additionally, distance sam- pling assumes implicitly that transects are placed randomly relative to the distribution of objects (birds) within a study area for justifi- able extrapolation of sample statistics to the population (Buckland et al. 2001). Our objec- tives were not to estimate study area density, but rather densities of birds inhabiting or us- ing designated portions (field borders and ad- jacent communities) of a study area. We marked transects with flagging at the beginning, end, and at 20-m intervals along each transect to allow observers to monitor their rate of speed and location during the sur- veys. Sampling was conducted by two observ- ers each year. Within each sampling interval, we randomly assigned transects to an observ- Smith et al. • OVERWINTERING BIRDS AND EIELD BORDERS 261 er; within each farm, however, we sampled transects in a systematic order to reduce travel time between transects. Each observer sam- pled 3-8 transects/morning/farm. Transect or- der within each farm was alternated among repetitions (i.e., transects were sampled in re- verse order during the second repetition). Moreover, following completion of the first repetition, observers switched transect sched- ules. We sampled all transects three times in 2002 and twice in 2003 during February- March, with approximately 3-4 weeks be- tween visits to the same transect (Freemark and Rogers 1995). We walked at approximately 20 m/min along each transect and made intermittent stops to record the number of individuals and species seen or heard on each side of the tran- sect line. Transects were sampled between 07:00 and 10:00 (CST) with wind speeds <16 km/hr. We assigned observations into one of four perpendicular distance bands (0.0-9. 9, 10.0-19.9, 20.0-29.9, and >30.0 m) on each side of the transect line. The first distance band in bordered transects contained the field border, whereas the first distance band for non-bordered transects was the first 9.9 m of crop field. To reduce observer bias, additional observers {n = 2) were trained by PJB and SJD prior to sampling (Kepler and Scott 1981, Smith 1984). Each observer was trained in sampling protocol, bird identification (by sight and sound), and distance estimation (Scott et al. 1981). Furthermore, we assumed that ob- servers were able to detect all birds on the transect line, detect birds at their initial loca- tion, and assign observations to correct dis- tance categories (Buckland et al. 2001). PJB collected data during both years of the study, whereas each of the additional observers col- lected data for only 1 year. Density estimation. — Because avian detec- tion probabilities (Bibby and Buckland 1987, Buckland et al. 2001) and assemblages (Best 1983, Shalaway 1985, Best et al. 1990, Sparks et al. 1996) diifer with plant community struc- ture and composition, we decided a priori to develop independent detection functions for the agricultural and non-agricultiiral sides of transects. On the agricultural side, we tlevel- oped detection functions for bordered ( f) and non-bordered (C) transects. We also stratilied the non-agricultural side ot transects based on vegetation type (W, G) and width (S, B). Thus, we developed six detection functions (T, C, GS, GB, WS, WB) for each species or guild. We tested pooling robustness (Burnham et al. 1980, Buckland et al. 2001) of the six func- tions by comparing Akaike’s Information Cri- terion (AIC; Akaike 1974) values between distance data fitted to pooled (e.g., using all observations on the non-agricultural side of wooded transects) and unpooled functions (e.g., wood strip and wood block observations on the non-agricultural side of wooded tran- sects). When comparing functions from the same set of data, a greater AIC value of a pooled model — relative to the sum of AIC values of the unpooled models — indicates that individual models fit the data better than a pooled model (Buckland et al. 2001). Testing of model robustness was conducted only be- tween models on the agriculture sides of tran- sects (T, C) and between models within veg- etation types on the non-agricultural sides of each transect (i.e., wood block and wood strip within woods). We assumed that detection functions did not differ between or within years; thus, we pooled observations across years and repetitions. Although some species occasionally occurred in loose aggregations, we treated all individuals as unique, indepen- dent observations. We used Program DISTANCE (Thomas et al. 1998) to model detection functions for spe- cies and guilds for which we recorded >60 observations within each of the six habitat types (Buckland et al. 2001). Only Song {Mel- ospiza melodia) and Savannah (Passercnlus sandwichensis) sparrows were detected often enough within these six habitat types to de- velop species-specific detection functions. We also developed detection functions for an “other sparrows” group (hereafter other spar- row) by pooling observations of Swamp Spar- row (Melospiza geor^iana\ n = 364), North- ern Cardinal (Cardina/is cardinalis: n = 306), White-throated Sparrow {Zonotrichia alhicol- Us\ n = 147), unidentilied sparrow (// = 106), F.astcrn Ibwhcc {Pipilo erythrophthalnnis', n = 104), Field Sparrow (Spizella pusilla: n = 27), Vesper Sjiarrow (Pooeretes ^ramineus\ n ^ 16), fox Sjxirrow (Passerella iJiaca\ n = 14), While-crowned Sparrow {Zonotrichia lencophrys: n = 12), C’hippifig .Sparrow {S/)i- zx’lla passerina: n = b), and Lark Sparrow 262 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 {Chondestes grammacus; n = 2). Because these species have somewhat similar foraging strategies during winter (i.e., granivorous ground-feeding birds that forage close to cov- er; Bent 1968), we assumed that detection probabilities were similar among species and could be modeled with a common detection function. Prior to analyses, we visually inspected the data by plotting observations by distance band for each detection function. The half-normal base function, with cosine or hermite poly- nomial adjustment terms, and the hazard-rate base function, with either cosine or polyno- mial adjustment terms, were selected as likely base-function, adjustment-term combinations that would best model the data. Base functions and series expansion terms, increasing in com- plexity (number of estimatable parameters), were sequentially evaluated by comparing AIC values among competing models (Bum- ham and Anderson 1998, Anderson et al. 2000). When a more complex model failed to adequately fit the data relative to the number of parameters within the model (greater AIC), the previous model was selected as the best approximating model. Right tmncation was set to 65 m, equal to the midpoint between the beginning of the last distance band (>30 m) and 100 m. We estimated bird density independently for the agricultural and non-agricultural sides of the transect. We used the T and C detection probabilities (value of probability density function f(x) evaluated at 0) to compute den- sities for the agricultural side of all bordered and non-bordered transects, respectively. These two density estimates (bordered and non-bordered on the agricultural side) repre- sented the effect of field borders without ac- counting for birds inhabiting the adjacent plant community. On the non-agricultural side, we used the GB, GS, WB, and WS de- tection probabilities to estimate densities us- ing only respective transects that had either a field border or no field border on the agricul- tural side. We then combined these class-spe- cific density estimates to estimate the joint density for a field edge with a given combi- nation of adjacent plant community and bor- der type. For example, we combined the den- sity estimates for the herbaceous block (GB), non-agricultural side of bordered transects with the density estimate of bordered transects (T) on the agricultural side to produce the density estimate for the TGB treatment com- bination. We believe this approach best ac- commodates instances where detection func- tions differ between sides of the same transect line. All reported densities and variances were generated using 1,000 bootstrap samples (with replacement) incorporating detection proba- bilities and numbers of observations/transect/ treatment combination (Buckland et al. 2001). We used a Z-test to evaluate border effects between like pairs (e.g., CGB versus TGB) (Buckland et al. 2001). All results were con- sidered significant at a = 0.05. Community structure. — To characterize community structure and relative conservation value of bordered and non-bordered field edg- es, we calculated species richness, the Shan- non-Weaver diversity index (Shannon and Weaver 1949), and total avian conservation value (TACV; Nuttle et al. 2003) using only observations within the first distance interval on each side of the transect centerline. TACV is a weighted index of community conserva- tion value calculated by multiplying species- specific abundances by their respective Part- ners in Flight (PIF) conservation priority scores (Carter et al. 2000). Species-specific scores were summed across all species within a given transect to produce a transect TACV score. PIF priority scores reflect different de- grees of need for conservation attention based on breeding and wintering distributions, rela- tive abundance, potential threats to breeding and wintering habitats, population trend, and a physiographically specific value of area im- portance (Carter et al. 2000). We used PIF pri- ority scores for species that winter in the East Gulf Coastal Plain physiographic region. “Fly-overs” were not included. We used t- tests to determine differences in mean species richness. Shannon Diversity, and TACV be- tween bordered and non-bordered transects by adjacent plant community. Where unequal variances occurred, we used Satterthwaite’s adjusted degrees of freedom (Milliken and Johnson 1992). All results were considered significant at a = 0.05. RESULTS We recorded 71 species and 17,562 individ- ual birds while sampling 155.2 km of tran- Smith et al. • OVERWINTERING BIRDS AND FIELD BORDERS 263 TABLE 1. Sampling effort and model selection of detection functions of wintering Song, Savannah, and other sparrows along bordered and non-bordered agricultural field edges in Clay and Lowndes counties, Mis- sissippi, 2002-2003. Species/Class Lb n‘^ Model selected f(o) m^ AIC Song Sparrow Border 317 40,000 44 HN^ + cosine 0.2353 1 15.52 Non-border 76 37,600 38 HN -1- cosine 0.0940 1 95.63 Pooled Ag.f 393 77,600 82 HR + cosine 0.1353 2 163.86 Grass block 187 17,000 17 HRs + cosine 0.0890 2 236.66 Grass strip 240 20,600 22 HR + polynomial 0.6189 3 178.82 Pooled grass*^ 427 37,600 39 HN + cosine 0.1332 3 421.99 Wood block 250 20,000 22 HN + cosine 0.1316 1 165.40 Wood strip 137 20,000 21 HR + cosine 0.2025 2 100.31 Pooled wood*^ 387 40,000 43 HR + cosine 0.1453 2 269.64 Savannah Sparrow Border 151 40,000 44 HN + cosine 0.1435 1 80.91 Non-border 210 37,600 38 HR + polynomial 0.0350 2 528.49 Pooled Ag.*^ 361 77,600 82 HR + polynomial 0.1045 3 744.35 Grass block 82 17,000 17 HR + cosine 0.1396 2 67.37 Grass strip 463 20,600 22 HN + cosine 0.1331 1 298.10 Pooled grass*^ 545 37,600 39 HN + cosine 0.1300 1 369.13 Wood block 5 20,000 22 HN -1- cosine 0.0813 1 9.50 Wood strip 98 20,000 21 HN + cosine 0.1632 1 35.43 Pooled wood*^ 103 40,000 43 HN + cosine 0.1513 1 47.79 Other sparrows Border 186 40,000 44 HR -1- cosine 0.8448 2 73.49 Non-border 49 37,600 38 HR + cosine 0.0251 2 139.89 Pooled Ag.*^ 235 77,600 82 HR + cosine 0.6150 3 323.82 Grass block 145 17,000 17 HR + cosine 0.3594 2 282.15 Grass strip 215 20,600 22 HR -H cosine 0.6039 3 346.38 Pooled grass*^ 360 37,600 39 HR + cosine 0.5463 3 629.09 Wood block 276 20,000 22 HN + cosine 0.0885 3 537.16 Wood strip 287 20,000 21 HR + cosine 0.6893 3 380.04 Pooled wood*^ 563 40,000 43 HN + cosine 0.0981 3 937.29 ® Number of observations. ^ Sampling effort (total length of tran.sects in meters). Number of transects. Number of parameters in detection function. ® Half-normal ba.se function. f Pooled detection functions were not used to compute density. * Hazard-rate ba.se function. sects during 2002-2003. The five most abun- dant species were Red-winged Blackbird {Agelaius phoeniceus\ 44.7%), American Pipit (Anthus ruhescens; I 1 .2%), Song Sparrow (6.9%), Savannah Sparrow (5.7%), and Amer- ican Robin (Turclus mi^ratorius\ 4.9%). De- tection functions for Song, Savannah, and oth- er sparrows were not robust to pooling across adjacent plant communities (Table 1); there- fore, we used detection functions specific to the adjacent plant community to compute den- sity estimates for each species. Density. — Song Sparrow densities (birds/ ha) differed between bordered and non-bor- dered field edges adjacent to grass block (bor- der = 30.86, SE = 4.19; non-border = 8.29, SE = 2.58; Z = 4.59, F < ().()() 1) and wooded strip {F < ().()() 1) plant communities (Table 2). However, no difference in wSong Sparrow den- sity was observed between bordered and non- bordered transects adjacent to herbaceous strips (/^ = 0.24) and wooded blocks {F = 0.35; Table 2). Savannah Sparrow densities did not differ between bordered and non-bor- dered transects adjacent to herbaceous blocks (border = 14.95, SE = 6.14; non-border = 4.74, SE = 1.45; Z = 1.62, F = 0.053). her- baceous strips {F = 0.13), wooded blocks {F 264 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 TABLE 2. Mean wintering densities (birds/ha) of Song, Savannah, and other sparrows along bordered and non-bordered agricultural field edges by adjacent plant community in Clay and Lowndes counties Mississinoi 2002-2003. ’ ’ Species/ Bordered^ Non-bordered community^ Mean SE Mean SE RES‘= Z-test P-value Song Sparrow Grass block 30.86 4.19 8.29 2.58 272.25 4.59 <0.001 Grass strip 95.87 30.00 70.03 20.90 36.90 0.71 0.24 Wood block 25.34 3.68 28.20 6.38 -10.14 -0.39 0.35 Wood strip 38.17 4.92 10.24 2.18 272.75 5.20 <0.001 Savannah Sparrow Grass block 14.95 6.14 4.74 1.45 215.40 1.62 0.053 Grass strip 18.05 9.93 47.51 24.27 -62.01 -1.12 0.13 Wood block 5.40 2.44 2.35 1.23 129.78 1.12 0.13 Wood strip 21.47 15.08 2.28 1.24 841.67 1.27 0.10 Other sparrows Grass block 78.20 12.99 19.36 7.96 303.93 3.86 <0.001 Grass strip 138.98 18.05 30.01 7.39 363.11 5.59 <0.001 Wood block 51.44 11.81 12.55 2.70 309.88 3.21 <0.001 Wood strip 128.94 16.98 107.69 26.80 19.73 0.67 0.25 ^ Adjacent plant community on the non-agriculture side of the transect. ^ Mean is the sum of densities of agricultural and non-agricultural sides of transects. Relative effect size: ([border - non-border]/non-border) X 100. - 0.13), and wooded strips {P = 0.10; Table 2). Other sparrow densities differed with re- spect to bordered and non-bordered transects along herbaceous block (border = 78.20, SE = 12.99; non-border = 19.36, SE = 7.96; Z = 3.86, P < 0.001), herbaceous strip {P < 0.001), and wooded block (P < 0.001) com- munities (Table 2). However, densities did not differ along wooded strips (P = 0.25; Table 2). Most Field Sparrow (92.6%) and Swamp Sparrow (91.8%) observations occurred along bordered transects. We recorded similar num- bers of Northern Cardinal (border =145; non- border = 161), Eastern Towhee (border = 44; non-border = 60), Chipping Sparrow (border = 3; non-border = 3), White-throated Spar- row (border = 62; non-border = 85), Vesper Sparrow (border = 7; non-border = 9), and unidentified sparrows (border =103; non-bor- der = 56) along bordered and non-bordered transects; however, few Fox Sparrows (border — 1; non-border =13) and no White-crowned or Lark sparrows were recorded along bor- dered transects. Community structure. — We recorded 59 species (6,108 individuals) within one dis- tance band on each side of transects. The most abundant species were Song Sparrow (22.7%), American Robin (7.5%), Savannah Sparrow (6.9%), Swamp Sparrow (6.8%), and Northern Cardinal (6.8%). Species richness, diversity, and TACV did not differ between bordered and non-bordered transects, regardless of the adjacent plant community type (Table 3). DISCUSSION Brennan (1991), Rodenhouse et al. (1993), and Warner (1994) suggested that the elimi- nation of grassy edge communities around ag- ricultural field edges and fencerow habitats contributed to the decline of Northern Bob- white {Colinus virginianus) and many other grassland species inhabiting farmlands. Most sparrows are ground foragers (Wheelwright and Rising 1993, Arcese et al. 2002) and their use of strip-cover habitats often depends upon vegetation structure (Bryan and Best 1991, Rodenhouse et al. 1993, Camp and Best 1994). We observed greater densities of sev- eral sparrow species where field borders were established. However, this effect varied by species and type of adjacent plant community. Song Sparrow and other sparrow densities were greatest where field borders were estab- lished along existing grasslands. The habitat Smith et al. • OVERWINTERING BIRDS AND FIELD BORDERS 265 TABLE 3. Species richness. Shannon- Weaver diversity index, and total avian conservation value using observations within one distance-band on each side of transects along bordered and non-bordered agricultural field edges by adjacent plant community type in Clay and Lowndes counties, Mississippi, 2002-2003. Measure/ Bordered Non-bordered Adjacent plant community^ Mean SE Mean SE RES*’ r-test F-value Species richness Grass block 6.60 0.22 5.29 0.78 24.76 1.62 0.15 Grass strip 6.54 0.79 8.00 0.96 -18.25 -1.17 0.26 Wood block 7.00 1.16 9.30 1.42 -24.73 -1.27 0.22 Wood strip 10.18 1.16 11.50 1.12 - 1 1 .48 -0.82 0.43 Shannon- Weaver Grass block 1.37 0.08 1.28 0.14 7.03 0.58 0.57 Grass strip 1.21 0.09 1.42 0.15 -14.79 -1.20 0.24 Wood block 1.29 0.17 1.35 0.15 -4.44 -0.24 0.81 Wood strip 1.60 0.19 1.92 0.20 -16.67 -1.19 0.25 Total avian conservation value Grass block 970.60 145.05 566.00 157.00 71.48 1.86 0.08 Grass strip 1,199.55 272.22 1,403.00 409.61 -14.50 -0.41 0.68 Wood block 677.67 191.01 996.70 273.72 -29.00 -0.98 0.34 Wood strip 2,421.18 1,392.05 694.30 96.97 248.72 1.24 0.24 “ Adjacent plant community on the non-agricultural side of the transect. ^ Relative effect size; ([border — non borderj/non-border) X 100. value of herbaceous field borders adjacent to grasslands may seem paradoxical, but most grasslands on our study farms were monotypic stands of cool-season, exotic forage grasses that provided little vertical structure and little seed-production. Only Song Sparrow densities were greater along wooded strip habitats with a field border. Once crops were harvested, field border habitats provided the structural vegetation characteristics commensurate with the foraging ecology of most sparrows. Field borders were recently established (<3 years old) and consisted primarily of seed-produc- ing grasses and forbs coupled with a relatively open understory that facilitated ground-based foraging. Additionally, field borders provided escape cover in close proximity to other for- aging sites, mainly row-crop fields containing waste grain. Therefore, we speculate that field borders may enhance the value of existing grasslands and cropland by producing addi- tional foraging habitat and escape cover in close proximity to waste-grain food sources. The net effect of field borders may be to in- crease usable space and carrying capacity for sparrows in agricultural landscapes. Given that most sparrow species observed in our study had somewhat similar foraging strategies, we had expected field borders to elicit similar responses across most sparrow species. With the exception of Song, Field, and Swamp sparrows. Savannah Sparrows and five of the other sparrow species were equally abundant along bordered and non-bordered transects, regardless of adjacent plant com- munity. Whereas our estimates for other spar- rows were markedly different between bor- dered and non-bordered transects across all of the adjacent plant communities (except for wooded strips), this effect was heavily weight- ed by observations of Swamp Sparrows. Swamp Sparrows were most strongly associ- ated with bordered transects and composed a large proportion (31.5%) of other sparrow ob- servations. Thus, our observed border effects for other sparrows were attributable mainly to greater densities of Swamp Sparrows along bordered transects. Collectively, across most adjacent plant communities, we observed greater densities of Song, Field, and wSwamp sparrows along bordered transects. Responses of other sparrow species were cither equivocal or negative. Overall, field borders apparently elicited greater use from oFily a few .selected species in our study, fhe effect of field bor- ders on other species or communities in other physiographic regions remains unknown. Conservation itnplicafions. — field borders 266 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 may provide important habitat in southern ag- ricultural systems where many eastern grass- land species of short-distance migrants over- winter. Murphy (2003) reported strong asso- ciations between changes in farmland struc- ture and population trends of short-distance migrant grassland birds and suggested that this association existed because short-distance migrants were affected by changes in agricul- tural landscapes during both the breeding and wintering seasons. The value of strip habitats has been a source of debate regarding their ability to serve as population sources during the breeding season; however, their roles dur- ing the wintering period are unknown. The availability of food resources during winter has been shown to enhance survival and body condition of birds (Porter et al. 1980, Brit- tingham and Temple 1988, Desrochers et al. 1988, Egan and Brittingham 1994). Although the survivorship of birds wintering in strip habitats is not known, we contend that the an- nual grasses characteristic of these idle com- munities might provide important thermal and energetic resources (Klute et al. 1997, Best et al. 1998). Weed seeds are the primary energy source for most wintering sparrows (Wheelwright and Rising 1993, Mowbray 1997, Arcese et al. 2002). We recommend that field borders be maintained in early serai stages through peri- odic disturbance (e.g., fire or disking) to pro- vide greater quantities of, and accessibility to, seeds of annual plants during the winter (Bur- ger et al. 1990, Millenbah et al. 1996, Best et al. 1998, Greenfield et al. 2002). Serai species, such as giant ragweed, provide comparatively high levels of metabolizable energy relative to other non-agriculture plant seeds (Robel et al. 1979). Additionally, field borders may provide safe access to other highly metabolizable food sources, such as waste grain. Collectively, we suggest that field borders provide important winter habitat for many grassland birds due to their greater abundance of food (weed seed) and more complex vegetation structure for roosting, loafing, thermal, and escape cover than that found in adjacent row crops and grasslands. Identifying resource management systems that support both birds and farm operators is important for maintaining a diverse farmland avifauna (Rodenhouse et al. 1993, Musters et al. 2001, Murphy 2003). Environmental ben- efits (e.g., decreased runoff of herbicides and nutrients, reduced soil erosion and sedimen- tation) of field-border conservation practices are well documented; the wildlife habitat val- ue of field borders, especially during winter, is not as well understood. Our results suggest that field borders support greater densities of certain sparrow species along agricultural field edges during the winter, but they may not nec- essarily support greater species richness and diversity. These results, combined with our current understanding of environmental and economic benefits of field borders, suggest that field-border conservation practices are compatible with the needs of farm operators while diversifying farmland vegetation struc- ture to enhance local avifauna. The U.S. Department of Agriculture’s Na- tional Conservation Buffer Initiative practices, such as field borders, offer potential opportu- nities for enhancing wintering habitat for nu- merous grassland birds on southeastern farm- lands. Widespread implementation of field- border conservation practices is currently fea- sible (through Farm Bill programs) and likely to occur given the growing public concern re- garding sustainable agriculture. However, as noted by Peterjohn (2003), simple, all-encom- passing solutions will not reverse significant declines of farmland birds; field-border con- servation practices may only benefit some species in some physiographic regions. We agree with Herkert et al. (1996) and Peterjohn (2003) in their assertion that the greatest gap in our knowledge of farmland bird ecology is winter ecology. We recommend that a greater emphasis be placed on research addressing overwinter benefits of farmland conservation practices to wildlife. ACKNOWLEDGMENTS This study was funded by the MSU-NASA Remote Sensing Technologies Center; the USDA-NRCS Wild- life Habitat Management and Watershed Science Insti- tutes; Mississippi Department of Wildlife, Fisheries, and Parks; Southern Region SARE program; Quail Unlimited; Monsanto; and the Forest and Wildlife Re- search Center, Mississippi State University. We thank D. M. DeBruyne and S. L. Leavelle for assistance in data collection. We also thank three anonymous re- viewers for their constructive comments. This manu- script is publication number WF213 of the Forest and Wildlife Research Center, Mississippi State University. Smith et al. • OVERWINTERING BIRDS AND FIELD BORDERS 267 LITERATURE CITED Akaike, H. 1974. A new look at the statistical model identification. IEEE Transactions on Automatic Control 19:716-723. Anderson, D. R., K. R Burnham, and W. L. Thomp- son. 2000. Null hypothesis testing; problems, prevalence, and an alternative. Journal of Wildlife Management 64:912-923. Arcese, R, M. K. Sogge, A. B. Marr, and M. A. Ratten. 2002. Song Sparrow (Melospiza melo- dia). The Birds of North America, no. 704. Askins, R. a. 1999. History of grassland birds in east- ern North America. Studies in Avian Biology 19: 60-71. Basore, N. S., L. B. Best, and J. B. Wooley, Jr. 1986. Bird nesting in Iowa no-tillage and tilled cropland. Journal of Wildlife Management 50:19- 28. Bent, A. C. 1968. Life histories of North American cardinals, grosbeaks, buntings, towhees, finches, sparrows, and allies. U.S. National Museum Bul- letin, no. 237. [reprinted 1968, Dover Rublica- tions. New York] Best, L. B. 1983. Bird use of fencerows: implications of contemporary fencerow management practices. Wildlife Society Bulletin 11:343-347. Best, L. B., H. Campa, III, K. E. Kemp, R. J. Robel, M. R. Ryan, J. A. Savidge, H. R. Weeks, Jr., and S. R. WiNTERSTEiN. 1998. Avian abundance in CRR and crop fields during winter in the Midwest. American Midland Naturalist 139:311-324. Best, L. B., R. C. Whitmore, and G. M. Booth. 1990. Use of cornfields by birds during the breeding sea- son: the importance of edge habitat. American Midland Naturalist 123:84-99. Bibby, C. j. and S. T. Buckland. 1987. Bias of bird census results due to detectability varying with habitat. Acta Ecologica 8:103-1 12. Blackwell, B. F. and R. A. Dolbeer. 2001. Decline of the Red-winged Blackbird population in Ohio correlated to changes in agriculture (1965-1996). Journal of Wildlife Management 65:661-667. Brennan, L. A. 1991. How can we reverse the North- ern Bobwhite population decline? Wildlife Soci- ety Bulletin 19:544-555. Brittingham, M. C. and S. A. Temple. 1988. Impacts of supplemental feeding on survival rates of Black-capped Chickadees. Ecology 69:581-589. Bryan, G. G. and L. B. Be.st. 1991. Bird abundance and species richness in grassed waterways in Iowa rowcrop fields. American Midland Naturalist 126: 90-102. Bryan, G. G. and L. B. Be.st. 1994. Avian nest den- sity and success in grassed waterways in Iowa rowcrop fields. Wildlife Society Bulletin 22:583- 592. Buckland, S. T, D. R. Ander.son, K. R. Burnham. J. L. I.aake, D. L. Bokchers, and L. Thomas. 2001. Introduction to distance sampling. Oxford Uni- versity Rress, New York. Burger, L. W, Jr., E. W. Kurzejeski, T. V. Dailey, AND M. R. Ryan. 1990. Structural characteristics of vegetation in CRR fields in northern Missouri and their suitability as bobwhite habitat. Transac- tions of the North American Wildlife and Natural Resources Conference 55:74-83. Burnham, K. R. and D. R. Anderson. 1998. Model selection and inference: a practical information- theoretic approach. Springer- Verlag, New York. Burnham, K. R, D. R. Anderson, and J. L. Laake. 1980. Estimation of density from line transect sampling of biological populations. Wildlife Monographs, no. 72. Camp, M. and L. B. Best. 1994. Nest density and nesting success of birds in roadsides adjacent to rowcrop fields. American Midland Naturalist 131: 347-358. Carter, M. E, W. C. Hunter, D. N. Rashley, and K. V. Rosenberg. 2000. Setting conservation priori- ties for landbirds in the United States: the Rartners In Flight approach. Auk 117:541-548. Daniels, R. B. and J. W. Williams. 1996. Sediment and chemical load reduction by grass and riparian filters. Journal of Soil Science 60:246-251. Desrochers, a., S. j. Hannon, and K. E. Nordin. 1988. Winter survival and territory acquisition in a northern population of Black-capped Chicka- dees. Auk 105:727-736. Dillaha, T. a., R. B. Reneau, S. Mostaghini, and D. Lee. 1989. Vegetative filter strips for agricultural non-point source pollution control. Transactions of the American Society of Agricultural Engineers 32:513-519. Egan, E. S. and M. C. Brittingham. 1994. Winter survival rates of a southern population of Black- capped Chickadees. Wilson Bulletin 106:514- 521. Freemark, K. and C. Rogers. 1995. Modification of point counts for surveying cropland birds. Rages 69-74 in Monitoring bird populations by point counts (C. J. Ralph, J. R. Sauer, and S. Droege, Eds.). General Technical Report RSW-149, USDA Forest Service, Racific Southwest Research Station, Albany, California. Greenfield, K. C., L. W. Burger, Jr., M. J. Cham- berlain, AND E. W. Kurzejeski. 2002. Vegetation management practices on Conservation Reserve Rrogram fields to improve Northern Bobwhite habitat quality. Wildlife Society Bulletin 30:527- 538. Herkert, j. R. 1995. An analysis of Midwestern breeding bird population trends: 1966-1993. American Midland Naturalist 134:41-50. Herkert, J. R.. D. W. Sami’le, and R. li. Warner. 1996. Management of Midwestern grassland land- .scapes tor the conservation of migratory birds. Rages 89-1 lb in Management of Midwestern landscapes for the conservation of Neotropical mi- gratory birds (E R. Thompson. Ill, Ed.). General Technical Report NC 187. USDA horest Service. 268 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 North Central Forest Experiment Station, St. Paul, Minnesota. Hunter, W. C., D. A. Buehler, R. A. Canterbury, J. L. Confer, and P. B. Hamel. 2001. Conservation of disturbance-dependent birds in eastern North America. Wildlife Society Bulletin 29:440-455. Johnson, R. J. and M. M. Beck. 1988. Influences of shelterbelts on wildlife management and biology. Agriculture, Ecosystems, and Environment 22: 301-335. Kepler, C. B. and J. M. Scott. 1981. Reducing bird count variability by training observers. Studies in Avian Biology 6:366-371. Klute, D. S., R. j. Robel, and K. E. Kemp. 1997. Seed availability in grazed pastures and Conservation Reserve Program fields during winter in Kansas. Journal of Field Ornithology 68:253-258. Knopf, F. L. 1 994. Avian assemblages on altered grass- lands. Studies in Avian Biology 15:247-257. Koford, R. R. and L. B. Best. 1996. Management of agricultural landscapes for the conservation of Neotropical migratory birds. Pages 68-88 in Man- agement of Midwestern landscapes for the con- servation of Neotropical migratory birds (F. R. Thompson, III, Ed.). General Technical Report NC-187, USDA Forest Service, North Central Forest Experiment Station, St. Paul, Minnesota. Marcus, J. E, W. E. Palmer, and P. T. Bromley. 2000. The effects of farm field borders on overwintering sparrow densities. Wilson Bulletin 112:517—523. Millenbah, K. E, S. R. Winterstein, H. Campa, III, L. T. Furrow, and R. B. Minnis. 1996. Effects of Conservation Reserve Program field age on avian relative abundance, diversity, and productivity. Wilson Bulletin 108:760-770. Milliken, G. a. and D. E. Johnson. 1992. Analysis of messy data. Chapman and Hall, New York. Mowbray, T. B. 1997. Swamp Sparrow {Melospiza georgiana). The Birds of North America, no. 279. Murphy, M. T. 2003. Avian population trends within the evolving agricultural landscape of eastern and central United States. Auk 120:20-34. Musters, C. J. M., M. Kruk, H. J. De Graaf, and W. J. Ter Keurs. 2001. Breeding birds as a farm product. Conservation Biology 15:363-369. Noss, R. E, E. T. LaRoe, and J. M. Scott. 1995. En- dangered ecosystems of the United States: a pre- liminary assessment of loss and degradation. Bi- ological Report, no. 28. U.S. National Biological Service, Washington, D.C. Nuttle, T, a. Leidolf, and L. W. Burger, Jr. 2003. Assessing conservation value of bird communities with Partners in Flight-based ranks. Auk 120:541- 549. Peterjohn, B. G. 2003. Agricultural landscapes: can they support healthy bird populations as well as farm products? Auk 120:14-19. Peterjohn, B. G. and J. R. Sauer. 1999. Population status of North American grassland birds from the North American Breeding Bird Survey, 1966- 1996. Studies in Avian Biology 19:27-44. Porter, W. E, R. D. Tangen, G. C. Nelson, and D. A. Hamilton. 1980. Effects of corn food plots on Wild Turkeys in the Upper Mississippi Valley. Journal of Wildlife Management 44:456-462. Puckett, K. M., W. E. Palmer, P. T. Bromley, J. R. Anderson, Jr., and L. T. Sharpe. 1995. Bobwhite nesting ecology and modern agriculture: a man- agement experiment. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 49:505-516. Robel, R. J., A. R. Bisset, and T. M. Clement, Jr. 1979. Metabolizable energy of important foods of bobwhite in Kansas. Journal of Wildlife Manage- ment 43:982-986. Rodenhouse, N. L., L. B. Best, R. J. O’Connor, and E. K. Bollinger. 1993. Effects of temperate ag- riculture on Neotropical migrant landbirds. Pages 280-295 in Status and management of Neotropi- cal migratory landbirds (D. M. Finch and P. W. Stangel, Eds.). General Technical Report RM- 229, USDA Forest Service, Rocky Mountain For- est and Range Experiment Station, Fort Collins, Colorado. Ryan, M. R., L. W. Burger, and E. W. Kurzejeski. 1998. The impact of CRP on avian wildlife: a re- view. Journal of Production Agriculture 1 1:61-66. Samson, E B. and F. L. Knopf. 1994. Prairie conser- vation in North America. Bioscience 44:418-421. Sauer, J. R., J. E. Hines, and J. Fallon. 2003. The North American Breeding Bird Survey, results and analysis 1966-2002, ver. 2003.1. USGS Pa- tuxent Wildlife Research Center, Laurel, Mary- land. www.mbr-pwrc.usgs.gov/bbs/bbs.html (ac- cessed 20 June 2004). Scott, J. M., F. L. Ramsey, and C. B. Kepler. 1981. Distance estimation as a variable in estimating bird numbers. Studies in Avian Biology 6:334- 340. Shalaway, S. D. 1985. Fencerow management for nesting birds in Michigan. Wildlife Society Bul- letin 13:302-306. Shannon, C. E. and W. Weaver. 1949. The mathe- matical theory of communication. University of Illinois Press, Urbana. Smith, M. D. 2004. Wildlife habitat benefits of field border management practices in Mississippi. Ph.D. dissertation, Mississippi State University, Mississippi State. Smith, P. G. R. 1984. Observer and annual variation in winter bird population studies. Wilson Bulletin 96:561-574. Sparks, T. H., T. Parish, and S. A. Hinsley. 1996. Breeding birds in field boundaries in an agricul- tural landscape. Agriculture, Ecosystems, and En- vironment 60:1-8. Thomas, L., J. L. Laake, J. F. Derry, S. T. Buckland, D. L. Borchers, D. R. Anderson, K. P. Burnham ET al.1998. Distance, ver. 3.5, release 6. Research Unit for Wildlife Population Assessment, Univer- sity of St. Andrews, United Kingdom. Vickery, P. D., P. L. Tubaro, J. M. Cardosa da Silva, Smith et al. • OVERWINTERING BIRDS AND FIELD BORDERS 269 B. G. Peterjohn, J. R. Herkert, and R. B. Cav- alcanti. 1999. Conservation of grassland birds in the Western Hemisphere. Studies in Avian Biol- ogy 19:2-26. Warner, R. E. 1994. Agricultural land use and grass- land habitat in Illinois: future shock for midwest- ern birds? Conservation Biology 8:147-156. Webster, E. P. and D. R. Shaw. 1996. Impact of veg- etative filter strips on herbicide loss in runoff from soybean {Glycine max). Weed Science 44:662- 671. Wheelwright, N. T. and J. D. Rising. 1993. Savannah Sparrow (Passerculus sandwichensis). The Birds of North America, no. 45. Wilson Bulletin 1 17(3);270-279, 2005 COMPOSITION, ABUNDANCE, AND TIMING OF POST-BREEDING MIGRANT LANDBIRDS AT YAKUTAT, ALASKA BRAD A. ANDRES.' w BRIAN T. BROWNE,' ^ AND DIANA L. BRANN>'‘ ABSTRACT. The eastern Gulf of Alaska coastline is suspected of providing an important pathway for birds migrating to and from Alaska. Because no intensive study of landbird migration has been conducted m this region we used mist nets to study the post-breeding migration of landbirds along the coast from 1994 through 1999. Over six post-breeding periods, we netted for a total of 316 days (23,538 net-hr) and captured 13 490 individuals of 46 species (57.3 birds/100 net-hr). Six species constituted >65% of all captures (ordered by abundance)- Orange-crowned Warbler (Vermivora celata). Hermit Thrush {Catharus guttatus), Lincoln s Spa^ow (Melospiza lincolnii). Ruby-crowned Kinglet (Regulus calendula). Fox Sparrow {Passerella ihaca) and Yellow Warbler (Dendroica petechia). Most birds captured (71%) were Nearctic-Neotropical migrants, and percentages of hatching-year (HY) birds varied from 51 to 90% among common species. Daily capture rates of all species were highest between mid- August and mid- September. Migration of HY individuals preceded that of after- hatching-year (AHY) birds in 70% of the Nearctic-Neotropical species. Masses of HY Nearctic-Neotropical migrants were significantly less than those of AHY individuals. High capture rates and consistent annual use indicate that the eastern Gulf of Alaska coast is an important pathway for many small landbird particularly Nearctic-Neotropical species, departing breeding grounds m southern Alaska. Received 5 April 2004, accepted 23 May 2005. Birds are subjected to many physical and behavioral challenges when they migrate. Be- cause of the costs associated with undertaking these twice-annual movements, how birds re- spond to migration challenges has a profound effect on their population dynamics. Despite the critical role migration plays in their annual life cycles, knowledge about the migration bi- ology and ecology of many birds, particularly of small landbirds, remains only rudimentary throughout North America (Moore et al. 1995, Hutto 1998, Moore 2000). Information on small landbird migration in northern North America is particularly depauperate; relatively few studies of the migration of small landbirds have been conducted anywhere in Alaska (but see Bailey 1974, Manuwal and Manuwal 1979, Gibson 1981, Cooper and Ritchie 1995, Benson and Winker 2001). Isleib and Kessel (1973) suggested that the > U.S. Fish and Wildlife Service, Nongame Migra- tory Bird Management, 1011 East Tudor Rd., Anchor- age, AK 99503, USA. 2 Current address: U.S. Fish and Wildlife Service, Division of Migratory Bird Management, RO. Box 25486, DFC-Parfet, Denver, CO 80225, USA. 3 Current address: 152 Kenyon Ave., Warwick, RI 02886, USA. ^Current address: P.O. Box 20046, Juneau, AK 99801, USA. 3 Corresponding author; e-mail: Brad_Andres@fws. gov eastern Gulf of Alaska coastline is an impor- tant pathway for landbirds migrating to and from Alaska. Although some waterfowl spe- cies initiate spring over-water crossings of the Gulf of Alaska from the coast of the western United States and Canada, radar observations confirm that most birds migrate within a 20- km band offshore of British Columbia and southeastern Alaska (Myres 1972). The close proximity of tall (>3,000 m) mountains to the coast probably restricts inland passage of mi- grants; however, major river systems that bi- sect coastal mountains likely funnel some coastal migrants into and out of breeding grounds in interior Alaska, Yukon, and British Columbia (Isleib and Kessel 1973, Patten 1982). Although the migration of shorebirds, waterfowl, and raptors in the region has been somewhat studied (e.g., Patten 1982, Swem 1983, Andres and Browne 1998), virtually no information exists that describes migration patterns of small landbirds. Therefore, we un- dertook a study to determine the species and age composition, abundance, and timing of post-breeding, small landbirds that migrate along the eastern Gulf of Alaska coastline. METHODS The Yakutat Foreland (Foreland) is located along the Pacific coast of Alaska and extends 140 km southwesterly from the town of Yak- utat (59°30'N, 139° 50' W) to Cape Fair- 270 Andres et al. • POST-BREEDING ALASKA LANDBIRD MIGRATION 271 TABLE 1 . Effort and captures during mist netting of post-breeding landbird migrants at Yakutat, Alaska, 1994-1999. Year Number of nets Days Total net-hr Birds captured Capture rate*’ 1994 10 87 3,217 2,217 68.9 1995 11 78 3,306 1,359 41.1 1996 13 80 3,593 1,962 54.6 1997 13 85 4,215 2,122 50.3 1998 15 88 4,565 3,225 70.6 1999 15 83 4,642 2,605 56.1 All years 83 23,538 13,490 57.3 ^Percentage of possible days (1994 = 54 days, 1995-1999 = 65 days) nets were operated. *’ Birds/ 100 net-hr. weather (58° 48' N, 138° 00' W). This glacial plain varies in width from 30 to 70 km and is bounded on the east by the St. Elias Moun- tains and Brabazon Range and on the west by the Gulf of Alaska. The Foreland is charac- terized by sandy beaches, extensive sand dunes, tidal mudflats, deciduous shrublands, spruce forests, and muskegs and is transected by a series of relatively short, mostly clear- running rivers (Patten 1982). Most of the area is administered by the U.S. Forest Service as part of the Tongass National Forest. We established a banding station 1 .6 km west of the Yakutat airport (59° 30' N, 139° 40' W). The site was primarily open (65%) and veg- etated by bryophytes, grasses, sedges, forbs, and sweetgale (Myrica gale)\ patches of wil- lows {Salix spp.) and solitary Sitka spruces (Picea sitchensis) were interspersed through- out. A dense perimeter of Sitka spruce, alder (Alnus spp.), willow, and ferns bounded two sides of the study area. Post-breeding landbirds were captured in mist nets. Initially, 10 nets (12 X 2.6 m, 30- mm mesh) were erected and placed at ~50-m intervals; additional nets were added in sub- sequent years (Table 1). Most nets were placed in scattered shrub patches, and a few were set in the dense perimeter of spruce and alders. Overall, our mist nets sampled a total area of about 7.5 ha. From 1 August to 4 Oc- tober (except for 1994 when we ended netting on 23 September), nets were opened daily at sunrise (with a minimum starting time of 04:30 AST) and operated for an average of 6 (1995-1999) or 7 hr (1994). Nets were oper- ated in intermittent and light rain, but not in heavy rain or when wind was >26 km/hr. Net- ting ended by 14:00 and was not initiated on days when weather delayed opening the nets until after 11:00. Two to four trained observ- ers checked nets at 30-min intervals. Captured birds were removed and transported to a cen- tral processing station where standard mor- phological data, as described by Ralph et al. (1993), were collected. Age was determined primarily by degree of skull ossification and secondarily by diagnostic plumage character- istics; all species could be reliably aged if skull pneumaticization was incomplete (Pyle et al. 1987, Pyle 1997). To facilitate rapid pro- cessing on high capture days, we sometimes only recorded age and sex. We used available morphological descriptions (metrics and plumage) to determine whether migrants orig- inated from coastal or interior Alaska popu- lations (Gabrielson and Lincoln 1959, Pyle et al. 1987, Gibson and Kessel 1997, Pyle 1997). Overall mist- net mortality was <0.3%; most deaths were attributable to inclement weather or predation by mink (Mustela vison), ermine (Mustela erminea), or red squirrels (Tamias- ciurus hudsonicus). Our analysis was restricted to landbird spe- cies within the Apodiformes, Piciformes, and Passeriformes. Nomenclature follows the American Ornithologists’ Union (1998) check-list and subsequent supplements. Total numbers, capture rates (birds/ 100 net-hr), and proportions of all captures were calculated for each species across all years. The coefficient of variation (CV = 100 X SD/mean) of annual capture rates (1995-1999, when capture peri- ods were similar) was used to assess between- year variation. We included handled birds that escaped before banding in calculating overall capture rates but excluded captured individu- als that were previously banded. To assess oc- currence of species not sampled by mist nets, we kept a daily record of all species observed while mist netting. Lastly, we categorized spe- cies, according to migration distance, as Ne- arctic-Neotropical migrants, Nearctic-Nearctic migrants, or residents. We calculated the proportion of hatching- year (HY) individuals captured for species where >30 individuals were aged. We deter- mined species-specific median passage dates for all HY, after-hatching-ycar (AHY), and to- tal individuals, and the ranges of dates that 272 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 included 90% of captures of all ages. Due to the large numbers of individuals that occurred on the same dates, we used a chi-square sta- tistic, corrected for continuity, to test for age- related differences in passage timing by com- paring the number of individuals in each age- class that fell above and below the median passage date for each species. We used a t- test, with Satterthwaite’s approximation of de- grees of freedom (Snedecor and Cochran 1980:97), to compare median passage dates of Nearctic-Neotropical species and Nearctic- Nearctic species and to compare mean mass between HY and AHY birds. Lastly, we used weighted least-squares regression to evaluate the relationship between mass ratios (HY: AHY; response variable) and migration-dis- tance categories (Nearctic-Neotropical > Ne- arctic-Nearctic > resident). RESULTS From 1994 through 1999, we captured 13,490 individuals of 46 landbird species (57.3 birds/100 net-hr). An additional 11 spe- cies were observed but not captured. Annual capture rates varied between 41.1 and 70.6 birds/100 net-hr (Table 1). Kinglets, Hermit Thrushes, wood-warblers, and sparrows were most frequently captured, whereas corvids, woodpeckers, American Robins, Varied Thrushes, and finches were observed more of- ten than captured (Table 2, Appendix). Six species individually represented >5% of all birds captured and together constituted 65% of the all captures (Table 2). Several species (Steller’s Jays, Common Ravens, Chestnut- backed Chickadees, Golden-crowned King- lets, American Robins, and Varied Thrushes) were recorded on a high pereentage of days, but they may have represented repeated ob- servations of locally breeding individuals or residents rather than new observations of pas- sage migrants (Table 2). For 40% of the spe- cies encountered, either we captured <10 in- dividuals or they were observed on <10% of the mist-netting days (Appendix). Twenty-seven species that were observed or captured, and 71% of all captures, were Ne- arctie-Neotropical migrants {n = 23 species). Another 17 speeies were Nearctic-Nearctic migrants (18% of all captures, = 13 spe- cies), and 13 species (11% of all captures, n = 11 species) were resident. Coefficients of variation (CV) of annual eapture rates for reg- ularly occurring species were generally <50% (Table 2). Red-breasted Nuthatches were cap- tured only in 1994 but were observed in mod- erate numbers other years. Sixty-two percent of all fringillids were captured in a single year (1998), and these species — known to be irrup- tive — had some of the highest CVs for inter- annual capture rates (Table 2). Where readily discernible, morphometric measurements and plumage characteristics in- dicated that migrants captured at Yakutat orig- inated from coastal Alaskan populations (Her- mit Thrush, Orange-erowned Warbler, Fox Sparrow, and Song Sparrow). Four recaptures linked Yakutat to other locations along the Pa- cific coast: (1) a Yellow-rumped Warbler re- eaptured at Redding, California; (2) a Song Sparrow re-sighted at Juneau, Alaska; (3) a Fox Sparrow recaptured at Long Beach, Washington; and (4) a Golden-crowned Spar- row banded at Niles, California and recap- tured at Yakutat. Additionally, the only Sharp- shinned Hawk (Accipiter striatus) we banded in 6 years was recaptured outside of Vancou- ver, British Columbia, and a Yellow Warbler banded on the Alaska Peninsula was recov- ered 4 days later on a fishing boat 17 km off Yakutat’s coast. Hatching-year birds dominated captures of most species (Table 2), and proportionally fewer young warblers (65%) were captured than were young sparrows (81%; ^ 228, df = 1, P < 0.001). No consistent patterns of HY captures were evident among species of different migration-distance categories; high (>90%) percentages of young were captured in some species of residents, Nearctic-Nearc- tic migrants, and Nearctic-Neotropical mi- grants. Of the 15 rarest Nearctic-Neotropical and Nearctic-Nearctic migrants, the combined percentage of HY birds (91.2%, n = 9\ in- dividuals) exceeded that of any individual, common species. The high percentage of adult White-winged Crossbills captured in Septem- ber 1998 was attributable to their concurrent nesting activity at the site. Daily capture rates of many small landbird migrants were highest between mid-August and mid-September. However, specific timing differed among species (Table 3). Median pas- sage date of Nearctic-Neotropical migrant species was 12—13 days earlier than it was for Andres et al. • POST-BREEDING ALASKA LANDBIRD MIGRATION 273 TABLE 2. Abundance of post-breeding, small landbirds commonly caught in mist nets or observed at Yakutat, Alaska, 1994-1999. Coefficient of variation (CV) calculated as SD X 100/mean for species with >10 total captures. Species ordered by migration-distance category. Birds/100 net-hr*’ Hatching-year*’ Species Total captures^* % days observed® All years % of total CV (%) % rf Nearctic-Neotropical migrants Alder Flycatcher (Empidonax alnorum) 50 6 0.21 0.4 81 76 42 Ruby-crowned Kinglet {Regains calendula) 1,069 80 4.20 7.5 42 83 823 Hermit Thrush (Catharus guttatus) 2,016 69 8.37 15.0 28 85 1,679 American Robin {Tardus migratorius) 12 63 0.05 0.1 134 d d Orange-crowned Warbler {Vermivora celata) 2,128 67 9.17 16.4 13 61 1,815 Yellow Warbler {Dendroica petechia) 803 29 3.26 5.8 51 66 651 Yellow-rumped Warbler {Dendroica coronata) 456 42 1.95 3.5 79 86 388 Townsend’s Warbler {Dendroica townsendi) 16 2 0.06 0.1 53 — — Wilson’s Warbler {Wilsonia pusilla) 559 31 2.26 4.0 70 77 449 Savannah Sparrow {Passerculus sandwichensis) 529 37 2.25 4.0 38 67 448 Lincoln’s Sparrow {Melospiza lincolnii) 1,871 67 7.48 13.4 36 89 1,453 White-crowned Sparrow {Zonotrichia leacophrys) 86 10 0.37 0.7 54 96 75 Nearctic-Nearctic migrants Northern Flicker {Colaptes auratus) 13 Red-breasted Nuthatch^ {Sitta canadensis) 81 43 0.33 0.6 245 72 65 Brown Creeper {Certhia americana) 26 9 0.07 0.1 59 — — Winter Wren {Troglodytes troglodytes) 97 23 0.35 0.6 27 62 84 Varied Thrush {Ixoreus naevius) 106 79 0.40 0.7 40 80 81 American Tree Sparrow {Spizella arborea) 25 1 0.12 0.2 103 — — Fox Sparrow {Passerella iliaca) 898 40 4.05 7.3 75 79 806 Song Sparrow {Melospiza melodia) 40 4 0.14 0.3 46 75 28 Golden-crowned Sparrow {Zonotrichia atricapilla) 552 18 2.55 4.6 49 74 503 Dark-eyed Junco {Junco hyemalis) 548 52 1.60 2.9 33 89 314 Common Redpoll {Carduelis flammea) 444 44 2.18 3.9 82 88 394 Residents Downy Woodpecker {Picoides pubescens) 7 45 0.03 0.1 na — Hairy Woodpecker {Picoides villosus) 1 10 <0.01 <0.1 na — — Steller’s Jay {Cyanocitta stelleri) 7 85 0.01 <0.1 na — — Black-billed Magpie {Pica hudsonia) 0 25 0.00 0.0 na — — Common Raven {Corvus corax) 0 86 0.00 0.0 na — — Black-capped Chickadee {Poecile atricapillus) 14 6 0.06 0.1 76 — — Chestnut-backed Chickadee {Poecile rufescens) 218 81 0.85 1.5 56 90 162 Golden-crowned Kinglet {Re galas satrapa) 366 75 1.25 2.2 37 91 245 Red Crossbill {Loxia carvirostra) 4 30 0.01 <0.1 na — — White-winged Crossbill {Loxia leucoptera) 142 23 0.66 1.2 224 2 133 Pine Siskin {Carduelis pinas) 275 37 1.28 2.2 199 47 144 “ 1994-1999 captures or observations. *’ 1995-1999 captures. ' Sample size ba.sed on all aged captures. ** Not calculated for captures <.10. Individuals only captured in 1994. Nearctic-Nearctic migrant species (combined age classes: t = 2.28, df = 16, /" = 0.037). Ninety percent of the Alder Mycatchers, Wil- son’s Warblers, and Lincoln’s Sparrows had passed through Yakutat by 7 vSeptember. Ex- cept for Lincoln’s Sparrow, median passage dates for all other sparrows were later than they were for wood-warblers ( I’able 3). Male Slate-colored Juncos {Jiinco. h. hyemalis) mi- grated significantly later than male Oregon Juncos (7. //. orc^atuts\ only males could be readily identified to subspecies; X“ = 8.31, df = 1 , /^ = 0.004). Except for Winter Wrens, 90% of all individuals of all other Nearctic- Neotropical and Nearctic-Nearctic species had passed through Yakutat by 1 October. 274 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 .B S) > OOOOOOOc0>nr<2 oooooppp'^_'^_ OOOOOCDOOOO V V V V ooONCNON'nt^'Oinoo^ r-H0^r^r<50^f<^^~_p*^p o\— nooON^ ^ -H 04 — < 00^'O^t^CO04'O00 ^ ^ m ^ ^ ^ a a a H 3 C § b 3 ?p B o O 00 VO 04 O VO O d d d O P' ^ 00 o — ; lO p d d d >05 in (N 04 00 Tt 05 04 04 CO 4) >4 CO O CO ° o O o ^ CO 04 ^ DO DC jl _ < < CO < in c4 >n ov Oh CO CO CO 4) 4J 4) 4) CO CO CO CO VO 04 VO ^ 04 4) 4J 'P H- S =c .3 3 C c/5 u 2 O CO O 55 O U T3 4) DC 3 ■ 3 u o ^ £ a: o Andres et al. • POST-BREEDING ALASKA LANDBIRD MIGRATION 275 TABLE 4. Mass of after-hatching-year (AHY) and hatching-year (HY) birds captured during post-breeding migration at Yakutat, Alaska, 1994-1999. Only species that had >10 known-age individuals within each age class are included. Species arranged by migration-distance category. Mean (g) ± SE (n) Species AHY HY f-value P-value HY:AHY mass Nearctic-Neotropical migrants Ruby-crowned Kinglet 6.63 -+- 0.04 (114) 6.38 -F 0.02 (540) 6.460 <0.001 0.962 Hermit Thrush 24.84 -+- 0.13 (197) 24.45 -F 0.05 (1,225) 2.786 0.006 0.984 Orange-crowned Warbler 9.51 -h 0.03 (484) 9.40 -F 0.03 (636) 2.595 0.010 0.998 Yellow Warbler 10.33 -F 0.06 (178) 9.90 -F 0.05 (291) 5.285 <0.001 0.958 Yellow-rumped Warbler 13.11 -F 0.14 (58) 12.78 -F 0.06 (225) 2.152 0.035 0.975 Wilson’s Warbler 7.61 -F 0.05 (103) 7.48 -F 0.03 (245) 2.177 0.031 0.983 Savannah Sparrow 19.65 -F 0.24 (102) 18.97 -F 0.17 (206) 2.268 0.024 0.965 Lincoln’s Sparrow 16.21 -F 0.12 (160) 15.77 -F 0.04 (999) 3.414 0.001 0.973 Nearctic-Nearctic migrants Red-breasted Nuthatch 10.96 ± 0.11 (17) 10.97 + 0.14 (34) -0.049 0.96 1.001 Varied Thrush 83.52 -+- 1.76 (13) 82.75 -+- 0.61 (59) 0.418 0.68 0.991 Fox Sparrow 36.98 -+■ 0.36 (75) 36.44 -+- 0.18 (347) 1.343 0.18 0.985 Golden-crowned Sparrow 31.20 0.57 (32) 31.15 -H 0.25 (213) 0.075 0.94 0.998 Common Redpoll 12.11 -+- 0.34 (10) 12.16 -+- 0.09 (89) -0.151 0.88 1.004 Residents Chestnut-backed Chickadee 9.99 -F 0.16 (15) 10.14 -F 0.07 (88) -0.840 0.41 1.015 Golden-crowned Kinglet 6.07 -F 0.08 (31) 6.29 -F 0.03 (126) -2.496 0.017 1.036 Pine Siskin 13.04 -F 0.12 (45) 12.80 -F 0.18 (26) 1.081 0.29 0.982 In 70% of Nearctic-Neotropical migrant species, HY birds migrated significantly (P < 0.05) earlier than adults (Table 3). Age did not influence migration timing among Lincoln’s or White-crowned sparrows, but HY Alder Flycatchers migrated significantly later than adults (Table 3). Among Nearctic-Nearctic migrants, adult Fox (P = 0.010) and Golden- crowned (P < 0.001) sparrows migrated later than HY individuals. Timing was similar among age classes for the remaining species (Table 3). Masses of HY birds were lower (all P < 0.035) than those of AHY birds in all Nearc- tic-Neotropical migrants (Table 4). The pro- portional mass of HY individuals, relative to AHY individuals, decreased with increasing migration distance (i.e., migration category. Table 4; weighted least squares: f’2 13 “ 8.71, P = 0.004, = 0.57). HY individuals of spe- cies that migrate to the Neotropics weighed proportionally less than Nearctic migrants, which weighed proportionally less than resi- dents. DISCUSSION Mist-net capture rates at our Yakutat band- ing station were among the highest recorded at post-breeding banding stations in Alaska (see reports at www.absc.usgs.gov/research/ bpif/meetings.html), and Nearctic-Neotropical migrants constituted a majority of the cap- tures. Corresponding to the conclusions of Wang and Finch (2002), our mist-net samples were most effective for small landbirds but under-represented larger species (those >50 g). Relatively high capture rates at Yakutat, coupled with the small area we sampled (7.5 ha), support Isleib and Kessel’s (1973) asser- tion that a substantial number of small land- birds undertake a post-breeding migration along the eastern Gulf of Alaska coastline. Additional support is provided by the rela- tively low inter-annual variation in capture rates of many common species, particularly of Nearctic-Neotropical migrants. Our casual ob- servations suggest that post-breeding landbird migration is widespread across the Foreland's continuous mosaic of shrublands and shrubby meadows. vSpecies composition of post-breeding birds captured in mist nets and observed during mist netting was very similar to the breeding avifauna of Yakutat (Shortt 1939, Patten 1982, Andres and Browne 2005) and other coastal 276 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 regions of south-central Alaska (Gabrielson and Lincoln 1959, Isleib and Kessel 1973). Additionally, only coastal forms of Hermit Thrush, Orange-crowned Warbler, and Fox Sparrow were captured at Yakutat. The Gulf of Alaska coastline does not appear to be a major migration route for several common western Alaska species (Alder Flycatcher, Gray-cheeked Thrush, Blackpoll Warbler, and Northern Waterthrush). These species were much more abundant at Fairbanks than at Yakutat during post-breeding migration (Ben- son and Winker 2001). Alder Flycatchers, however, may have initiated migration prior to our netting effort. The Foreland periodically provides breeding, stopover, and winter habi- tat for irruptive species. Annual synchrony in capture rates of White-winged Crossbills, Common Redpolls, and Pine Siskins at Yak- utat matched synchronous irruption patterns documented in western North America (Ko- enig 2001). Off-site recoveries and recaptures, albeit few, suggest that migrants likely continue southward along the Pacific coast of North America. Although waterbirds are known to migrate in spring across the Gulf of Alaska (Myres 1972), the extent to which small land- birds make the same crossing remains un- known; however, the recovery of an HY Yel- low Warbler on a fishing boat 17 km off the Yakutat area coastline provides some evidence that small landbirds might be undertaking at least short-distance, over-water crossings. The banding site of that Yellow Warbler was ac- tually to the southwest of Yakutat, suggesting that some migrants may originate from areas to the west and southwest of Yakutat. Large numbers of Wilson’s Warblers banded on the Alaska Peninsula did not appear at Yakutat (see reports at www.absc.usgs.gov/ research/ bpif/meetings.html). Additionally, many post- breeding passerine migrants have been en- countered 80 km offshore on Middleton Island (59° 43' N, 146° 30' W; see fall reports in the serial. North American Birds). In general, age ratios of migrant passerines vary markedly among sites and species (Ralph 1981, Woodrey and Chandler 1997, Woodrey 2000). Our study is one of the first to show consistently greater percentages of young sparrows relative to that of wood-warblers. Greater percentages of HY birds have been captured at Pacific and Atlantic coast sites rel- ative to corresponding inland sites (Murray 1966, Stewart et al. 1974, Mewaldt and Kaiser 1988, Morris et al. 1996, Humple and Geupel 2002). Ralph (1981) suggested that the high proportions of young birds on the coast delin- eated the periphery of a species’ migratory pathway. That HY individuals were predomi- nant (>90%) among captures of the rarest, and hence the most peripheral, species at our coastal Yakutat site supports Ralph’s (1981) explanation. For the more common Yakutat species, age ratios are more comparable with those found at inland sites, suggesting that the eastern Gulf of Alaska coastline is a major route for many of the migrant species that we captured. Woodrey and Moore (1997) thought that more balanced age ratios observed along the northern Gulf of Mexico coast were a re- sult of the flight barrier imposed by the open waters of the gulf. Tall mountains along the Gulf of Alaska coastline may impede a gen- eral eastward, inland flow of migrants. How- ever, large birds, such as Sandhill Cranes (Grus canadensis), are known to use coastal river valleys to access interior migration path- ways (Isleib and Kessel 1973, Patten 1982). The magnitude of small landbird migration through these river corridors, however, is un- known. The greatest number of small landbird mi- grants pass through Yakutat between mid- Au- gust and mid-September. West of Yakutat at Cold Bay, migration also peaked in late Au- gust (Bailey 1974). Our daily mist-netting ef- forts ensured that we did not miss weather- related passages of large numbers of migrants in any given year. Weather, however, assuredly has some influence on the annual variability in capture rates (see DeSante 1983). At Cold Bay, migrants increased with the passage of fronts (Bailey 1974), a pattern we observed casually at Yakutat. Rotenberry and Chandler (1999) suggested that southerly breeding wood-warblers initi- ated migration earlier than their counterparts to the north. At Yakutat, male Slate-colored Juncos, which do not breed at Yakutat, arrived much later than Oregon Junco males, which do breed there. Otherwise, the geographic similarity of the breeding avifauna of south- central Alaska and our inability to determine exact breeding origins of post-breeding mi- Andres et al. • POST-BREEDING ALASKA LANDBIRD MIGRATION 277 grants captured at Yakutat mask any timing patterns influenced by geographic origins of post-breeding migrants. The earlier passage of Yakutat’s Nearctic- Neotropical migrants corresponds with the shorter breeding-range occupancy of high-lat- itude passerine migrants captured at Fair- banks, Alaska (Benson and Winker 2001). However, some species differed markedly in their migration timing between these two sites; HY Alder Flycatchers, Yellow Warblers, Savannah Sparrows, and White-crowned Sparrows passed through 10-16 days earlier at Fairbanks than they did at Yakutat, whereas HY Ruby-crowned Kinglets and Wilson’s Warblers passed through 10-14 days later in Fairbanks. Some Alder Flycatchers and Wil- son’s Warblers may have passed through Yak- utat before netting was initiated on 1 August. Hatching-year Orange-crowned Warblers, Yel- low-rumped Warblers, Fox Sparrows, and Lincoln’s Sparrows were similar in their mi- gration timing at the two sites; timing patterns of AHY birds were similar to those of HY individuals at both sites. Differences in age-related patterns of pas- serine migration generally arise from differ- ences in timing and location (Woodrey 2000). The high percentage (70%) of Nearctic-Neo- tropical species among which HY birds pre- ceded AHY individuals in migration corre- sponded to the age-related migration patterns observed at Fairbanks; there, in 64% of Ne- arctic-Neotropical species, HY birds preceded AHY birds (Benson and Winker 2001). There was complete consistency in the age-related passage of 10 migrant species shared between Yakutat and Fairbanks. Because we operated mist nets on a daily schedule, as did the Fair- banks station, age-related differences in mi- gration timing were not due to temporal dif- ferences in sampling effort (Kelly and Finch 2000). Few other sites south of Alaska have shown such consistent age-related patterns in migration timing of short- and long-distance migrants. Mixing of geographically distinct populations at more southern sites may blur age-dependent migration patterns. Hatching-year individuals may initiate southward movements sooner than adults be- cause they are less efficient in procuring food resources needed to complete migration. In- efficiency is due to inexperience, social and physiological constraints, or some combina- tion of these factors (reviewed by Woodrey 2000). Alternatively, adult birds may delay migration until the completion of prebasic molt (reviewed by Gauthreaux 1982). That masses of many HY Yakutat migrants were less than those of AHY birds suggests that young birds are less efficient at performing their first migration. Mass differences between HY and AHY individuals are generally great- est in long-distance migrants at Yakutat, and at other migration sites (reviewed in Woodrey 2000); masses of resident HY and AHY birds at Yakutat were more equitable. Lower mass, and assumed low fat loads, would cause HY individuals to make shorter flights and hence prolong migration time. Accordingly, age-re- lated differences in migration timing should dissipate as migrants approach their wintering areas and should be greatest nearer their breeding areas. Clearly, the eastern Gulf of Alaska coast- line provides an important pathway for small landbirds undertaking their post-breeding mi- gration southward from Alaska. Because land- bird stopover habitats are a fairly continuous element in the landscape matrix of south-cen- tral Alaska, we suspect that migratory popu- lations are probably not limited by the amount or configuration of stopover habitat. Mainte- nance of high quality stopover habitats along the entire migration pathway, however, is needed to ensure successful migration of small landbirds, particularly for those com- pleting their first southward migration. ACKNOWLEDGMENTS This project required the collaboration of numerous individuals and agencies; we thank each for the assis- tance provided. Banders T W. Trapp, R. .1. Capitan, M. St. Germain, J. M. Stotts, E. Wells, and .1. A. .lohnson each worked diligently. Staff of the Tongass National Forest, Yakutat Ranger i;)istrict. provided comfortable housing and logistical support; particularly helpful were D. Walter (deceased), V. Harke, and B. Eucey. K. Ko/ie and .1. Rogers assisted with transportation. R. R. Leedy and K. D. Wohl asssisted with field opera- tions, and the U.S. lush and Wildlife Service provided funding for this project. Several people helped at the banding statioti; their assistance was invaluable, espe- cially on high capture days. A special thanks to H. I.ucey, r. I. each, D. I.. Mruden, W. Bryden, (^. .Smith, M. .Schroeder, and (\ Rohl. Helpful comments on man- uscript drafts were provided by I). I). Gibson, C. M. Handel, and two anonymous reviewers. 278 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 LITERATURE CITED American Ornithologists’ Union. 1998. Check-list of North American birds, 7th ed. American Or- nithologists’ Union, Washington, D.C. Andres, B. A. and B. T. Browne. 1998. Spring mi- gration of shorebirds on the Yakutat Forelands, Alaska. Wilson Bulletin 110:326-331. Andres, B. A. and B. T. Browne. 2005. The birds of Yakutat, Alaska. USD A Forest Service technical report, Juneau, Alaska. In press. Bailey, E. P. 1974. Passerine diversity, relative abun- dance, and migration at Cold Bay, Alaska. Bird- Banding 45:145-151. Benson, A. M. and K. Winker. 2001. Timing of breeding range occupancy among high-latitude passerine migrants. Auk 118:513-519. Cooper, B. A. and R. J. Richie. 1995. The altitude of bird migration in east-central Alaska: a radar and visual study. Journal of Field Ornithology 66: 590-608. DeSante, D. F. 1983. Annual variability in the abun- dance of migrant landbirds on southeast Farallon Island, California. Auk 100:826-852. Gabrielson, I. N. AND F. C. Lincoln. 1959. Birds of Alaska. Wildlife Management Institute, Washing- ton, D.C. Gauthreaux, S. a., Jr. 1982. The ecology and evo- lution of avian migration systems. Avian Biology 6:93-168. Gibson, D. D. 1981. Migrant birds at Shemya Island, Aleutian Islands, Alaska. Condor 83:65-77. Gibson, D. D. and B. Kessel. 1997. Inventory of the species and subspecies of Alaska birds. Western Birds 28:45-95. Humple, D. L. and G. R. Geupel. 2002. Autumn pop- ulations of birds in riparian habitat of California’s Central Valley. Western Birds 33:34-50. Hutto, R. L. 1998. On the importance of stopover sites to migrating birds. Auk 115:823-825. ISLEIB, M. F. AND B. Kessel. 1973. Birds of the North Gulf Coast-Prince William Sound region, Alaska. Biological Papers of the University of Alaska, no. 14, Fairbanks. Kelly, J. F. and D. M. Finch. 2000. Effects of sam- pling design on age ratios of migrants captured at stopover sites. Condor 102:699—702. Koenig, W. D. 2001. Synchrony and periodicity of eruptions by boreal birds. Condor 103:725—735. Manuwal, D. a. and N. j. Manuwal. 1979. Habitat utilization and migration of land birds on the Bar- ren Islands, Alaska. Western Birds 10:201-213. Mewaldt, L. R. and S. Kaiser. 1988. Passerine mi- gration along the inner coast range of central Cal- ifornia. Western Birds 19:1-23. Moore, F. R. (Ed.). 2000. Stopover ecology of Nearc- tic-Neotropical landbird migrants: habitat relations and conservation implications. Studies in Avian Biology, no. 20. Moore, F. R., S. A. Gauthreaux, Jr., P. Kerlinger, AND T. R. Simons. 1995. Habitat requirements dur- ing migration: important link in conservation. Pages 121-144 in Ecology and management of Neotropical migrant birds (T. F. Martin and D. M. Finch, Eds.). Oxford University Press, New York. Morris, S. R., D. W. Holmes, and M. E. Richmond. 1996. A ten-year study of the stopover patterns of migratory passerines during fall migration on Ap- pledore Island, Maine. Condor 98:395—409. Murray, B. G., Jr. 1966. Migration of age and sex classes of passerines on the Atlantic coast in au- tumn. Auk 83:352-360. Myres, M. T. 1972. Radar observations of three prob- able transoceanic migratory movements across the Gulf of Alaska in spring 1965. Syesis 5:107-116. Patten, S. M. 1982. Seasonal use of coastal habitat from Yakutat Bay to Cape Fairweather by migra- tory seabirds, shorebirds and waterfowl. Pages 296-603 in Environmental assessment of the Alaskan continental shelf, final reports of princi- pal investigators, vol. 16. Bureau of Land Man- agement/National Oceanic and Atmospheric Ad- ministration, Anchorage, Alaska. Pyle, P. 1997. Identification guide to North American birds, part I. Slate Creek Press, Bolinas, Califor- nia. Pyle, P, S. N. G. Howell, R. P. Yunick, and D. F. Desante. 1987. Identification guide to North American passerines. Slate Creek Press, Bolinas, California. Ralph, C. J. 1981. Age ratios and their possible use in determining autumn routes of passerine mi- grants. Wilson Bulletin 93:164—188. Ralph, J. C., G. R. Geupel, P. Pyle, T. E. Martin, AND D. F. DeSante. 1993. Handbook of field methods for monitoring landbirds. General Tech- nical Report PSW-GTR-144, USD A Forest Ser- vice, Pacific Southwest Research Station, Albany, California. Rotenberry, j. T. and C. R. Chandler. 1999. Dynam- ics of warbler assemblages during migration. Auk 116:769-780. Shortt, T. M. 1939. The summer birds of Yakutat Bay, Alaska. Contributions of the Royal Ontario Mu- seum of Zoology, no. 17. Snedecor, G. W. and W. G. Cochran. 1980. Statistical methods, 7th ed. Iowa State University Press, Ames. Stewart, R. M., L. R. Mew alt, and S. Kaiser. 1974. Age ratios of coastal and inland fall migrant pas- serines in central California. Bird-Banding 45:46- 57. SWEM, T. 1983. Sitkagi Beach raptor migration study, spring 1982. Pages 13-26 in Proceedings of Hawk Migration Conference IV (M. Harwood, Ed.). Hawk Migration Association of North America, Kempton, Pennsylvania. Wang, Y. and D. M. Finch. 2002. Consistency of mist netting and point counts in assessing landbird spe- Andres et al. • POST-BREEDING ALASKA LANDBIRD MIGRATION 279 cies richness and relative abundance during mi- gration. Condor 104:59-72. WooDREY, M. S. 2000. Age-dependent aspects of stop- over biology of passerine migrants. Studies in Avian Biology 20:43-52. WooDREY, M. S. AND C. R. CHANDLER. 1997. Age- related timing of migration: geographic and inter- specific patterns. Wilson Bulletin 109:52-67. WooDREY, M. S. AND E R. MooRE. 1997. Age-related differences in the stopover of fall landbird mi- grants on the coast of Alabama. Auk 114:695- 707. APPENDIX. Post-breeding migrants rarely captured arranged by migration-distance category. or observed at Yakutat, Alaska, 1994-1999. Species Species Number captured % days observed Nearctic-Neotropical migrants Rufous Hummingbird (Selasphorus rufus) 8 1 Olive-sided Flycatcher (Contopus cooperi) 0 1 Yellow-bellied Flycatcher (Empidonax flaviventris) 1 0 Warbling Vireo (Vireo gilvus) 6 1 Bank Swallow (Riparia riparia) 0 1 Barn Swallow (Hirundo rustica) 0 4 Gray-cheeked Thrush (Catharus minimus) 1 <1 Swainson’s Thrush {Catharus ustulatus) 2 <1 American Pipit (Anthus rubescens) 0 4 Tennessee Warbler (Vermivora peregrina) 1 0 Blackpoll Warbler (Dendroica striata) 2 <1 Northern Waterthrush (Seiurus noveboracensis) 7 <1 Common Yellowthroat {Geothlypis trie has) 7 1 Chipping Sparrow {Spizella passerina) 1 0 Brewer’s Sparrow {Spizella breweri) 2 0 Nearctic-Nearctic migrants Red-breasted Sapsucker {Sphyrapicus ruber) 0 2 Northern Shrike {Lanius excubitor) 0 1 White-throated Sparrow {Zonotrichia albicollis) 1 0 Lapland Longspur {Calcarius lapponicus) 2 4 Rusty Blackbird {Euphagus carolinus) 1 9 Brown-headed Cowbird {Molothrus ater) 0 <1 Residents Northwestern Crow {Corvus caurinus) 0 1 Pine Grosbeak {Pinicola enucleator) 2 0 Wilson Bulletin 1 1 7(3):280-290, 2005 VARIATION IN INCUBATION PATTERNS OF RED- WINGED BLACKBIRDS NESTING AT LAGOONS AND PONDS IN EASTERN ONTARIO J. RYAN ZIMMERLINGi 23 AND C. DAVISON ANKNEY> ABSTRACT. — We studied incubation patterns and hatchability of Red-winged Blackbirds (Agelaius phoeni- ceus) nesting in two different wetland habitats — beaver ponds and sewage lagoons — in eastern Ontario during 1999-2001. We presumed that, if incubating Red-winged Blackbirds could acquire food more readily at sewage lagoons than at beaver ponds, they should respond by taking fewer and shorter foraging bouts, which would result in longer bouts of attentiveness, shorter incubation periods, and higher hatchability of eggs. Although differences were small, female foraging bouts were shorter and bouts of attentiveness were longer at sewage lagoons than they were at beaver ponds. Incubation constancies were subsequently greater, and, ultimately, incubation periods at sewage lagoons were shorter. Shorter incubation periods at sewage lagoons, however, did not result in increased hatchability. Our results suggest that, in habitats where incubating Red-winged Blackbirds can acquire food more readily, incubation periods may become shorter and incubation constancies may become higher. Received 7 September 2004, accepted 28 April 2005. Many species of temperate- zone passerines modify incubation patterns in response to var- iation in nutrient availability (Hebert 2002, Ei- kenaar et al. 2003), frequency of mate feeding (Nilsson and Smith 1988, Pearse et al. 2004, Radford 2004), body mass (Williams 1991), temperature (Conway and Martin 2000a, Reid et al. 2002), and nest predation (Martin and Ghalambor 1999, Conway and Martin 2000b, Ghalambor and Martin 2002). Eggs of most passerines must be maintained at a tempera- ture of 34-39° C for optimal embryonic de- velopment (Drent 1975, Webb 1987, Williams 1996). Ambient temperatures, however, rarely remain within this range, and deviations in egg temperatures can affect incubation period and egg hatchability (Strausberger 1998); therefore, incubation by parents is required to prevent embryos from chilling or overheating. When ambient temperatures are low, incu- bation can be energetically demanding for parents, requiring an increase in metabolic rate to a level approaching that experienced during chick-rearing (Williams 1996, Thom- son et al. 1998, Visser and Lessells 2001). Hence, energetic demands during incubation may have fitness consequences: adult body condition may deteriorate, or adults may be ' Dept, of Biology, Univ. of Western Ontario, Lon- don, ON N6A 5B7, Canada. ^Current address: Bird Studies Canada, 115 Front St., Port Rowan, ON NOE IMO, Canada. ^ Corresponding author; e-mail: rzimmerling@ bsc-eoc.org unable to provide conditions conducive to em- bryonic development. Fitness consequences will be especially severe where only the fe- male incubates (gyneparental systems) and where bouts of attentiveness are interspersed with foraging bouts (Williams 1996). In gyneparental systems, daytime incuba- tion is usually intermittent because females must balance the time spent foraging against the thermal needs of the developing embryos and the energetic demands of rewarming the clutch after a foraging bout. Most reviews of avian incubation suggest that the duration of attentiveness bouts (interval during which the female incubates between two foraging bouts) is dictated by the female’s energy needs (Ken- deigh 1952, Haftorn 1978, Weathers and Sul- livan 1989, but see Conway and Martin 2000b). If the energy needs of the female are an important factor affecting incubation pat- terns, then nest attentiveness should increase in relation to the rate at which food can be acquired (i.e., food acquisition) during forag- ing bouts, the incubation period should be shorter, and hatching success should increase (Martin 1987). Thus, species that use more en- ergetically expensive foraging strategies or forage in habitats where food items are less available may have to spend more time for- aging or engage in more frequent foraging bouts to meet nutritional requirements. Although there have been few studies of variation in passerine incubation patterns, pre- sumably because these data are time-consum- 280 Zimmerling and Ankney • INCUBATION PATTERNS OF RED- WINGED BLACKBIRDS 28 1 ing and laborious to collect, results from sev- eral of these studies (e.g., Nilsson and Smith 1988, Moreno 1989, Sanz 1996, Pearse et al. 2004) suggest an important relationship be- tween nutrient availability and incubation pat- terns. For example, studies on Northern Wheatears (Oenanthe oenanthe; Moreno 1989), Blue Tits (Parus caeruleus; Nilsson and Smith 1988), and Pied Flycatchers (Fi- cedula hypoleuca; Sanz 1996) have revealed that females receiving supplemental food dur- ing incubation had significantly shorter incu- bation periods and/or their clutches experi- enced greater hatchability (but see Pearse et al. 2004). Moreover, there should be a pre- mium on short incubation periods, which re- duce the time that eggs are vulnerable to pred- ators (Clark and Wilson 1981, Conway and Martin 2000a, Martin 2002). As far as we know, there have been no stud- ies that have evaluated variation in incubation patterns related to foraging habits or food ac- quisition between habitats. Using a compara- tive approach, Reid et al. (1999) suggested that the duration of foraging bouts among Eu- ropean Starlings (Sturnus vulgaris) was more than four times longer (20 min versus 4.5 min) on Waddensea Island (from Drent et al. 1985) than on Fair Isle, where incubating adults could feed in close proximity to their nest cav- ities, reducing the time and energy needed to travel to foraging areas. In addition, Reid et al. (1999) suggested that, because the ground on Fair Isle remained permanently damp, it was unlikely that the starling’s invertebrate prey would be difficult to obtain during any period of the day. However, because Wadden- sea Island and Fair Isle differ substantially in latitude, climate, and habitat, comparison of incubation patterns between these islands was not feasible (Reid et al. 1999). We examined habitat-related variation on gyneparental incubation patterns, incubation periods, and hatchability of eggs by studying Red-winged Blackbirds {Agclaius phoenicciis) nesting at numerous sewage lagoons aiul bea- ver ponds in eastern Ontario. Extensive data have suggested that food availability is greater at sewage lagoons than in other habitats dur- ing the breeding season of many bird species (e.g., Swanson 1977, Piest and Sowls 1985, Hussell and Quinney 1987, Porter 1993, Zim- merling 2002). For example, during laying, in- cubation, and the nestling period of Tree Swallows (Tachycineta bicolor), insect bio- mass was 7-12 times greater at lagoons than in other habitats in southwestern Ontario, in- cluding a natural cattail marsh (Hussell and Quinney 1987). During the brood-rearing pe- riod in eastern Ontario, female Red-winged Blackbirds at sewage lagoons captured a mean of nine insects per foraging bout, whereas fe- males at beaver ponds captured one to two insects per foraging bout (Zimmerling 2002). Therefore, we predicted that females nesting at sewage lagoons would take fewer and shorter foraging bouts than females nesting at beaver ponds. Consequently, we also predict- ed that incubation periods would be shorter and egg hatchability greater at sewage la- goons. METHODS Study area. — From 1999 to 2001, we stud- ied Red-winged Blackbirds nesting at wet- lands in eastern Ontario between Cobden (45° 40' N, 77° 10' W) and Vankleek Hill (45° 35' N, 74° 40' W; see Zimmerling 2002). Wet- lands in the study area included 19 small (0.3- 3 ha) beaver ponds (hereafter, ponds) and 10 municipal sewage lagoon complexes (second- ary wastewater treatment facilities; hereafter, lagoons). On average, lagoon complexes were composed of three individual lagoons or “cells” (range = 1-7), but not all cells sup- ported nesting Red-winged Blackbirds. We sampled 10, 14, and 19 ponds in 1999, 2000, and 2001, respectively. Cattails (Typha spp.) dominated the emergent vegetation at both ponds and lagoons, but, relative to ponds, la- goons had only a thin strip of cattails around their perimeters. Most lagoon complexes were bordered by agricultural crops and old-fields, but mixed deciduous forests partially bordered several lagoons. Ponds were bordered mainly by old-fields and mixed deciduous forests. Time of ice breakup during early spring was similar on lagoons and ponds, with the exception of one aerated lagoon cell that be- came ice-free earlier. During the study period, water levels in pemds did not fluctuate >1 m, either seasonally or annually. In contrast, av- erage water depth within and anuing sewage lagoon complexes varied seasonally between 2 and 5 fii, but large fluctuations in water depth usually occurred outside of the Red- 282 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 winged Blackbird’s breeding season. In 2000, water levels at 7 of 10 lagoon sites were low- ered in mid-May; thus, only the remaining three lagoons were sampled. Despite obvious physical differences be- tween lagoons and ponds, Zimmerling (2002) showed that populations of female Red- winged Blackbirds in the eastern Ontario study area were demographically (juvenile: adult) similar and that morphological charac- teristics (i.e., culmen, wing chord, tarsus length, and body mass) of females also did not differ between habitats. In addition, although lagoons and ponds differed marginally in shape and size, the maximum number of ac- tive nests/ 1,000 m^ of wetland (based on mea- surements of wetland perimeters) were similar between habitats (Zimmerling 2002). In con- trast, the maximum number of active nests/ 1,000 m^ of emergent vegetation {Typha spp.) within wetlands was four times higher at la- goons than at ponds (8.4 versus 2.1) because suitable nesting habitat (i.e., emergent vege- tation) was restricted. Field methods. — Nests were discovered during twice-weekly searches of emergent vegetation. Nests were marked with flagging tape and monitored daily. Using remote tem- perature sensors (Hobo Temp XT, Onset Com- puter Co., Pocasset, Massachusetts), we as- sessed incubation patterns of female Red- winged Blackbirds at 406 nests (1999, 2000, and 2001, n = 59/45 [lagoon/pond], 38/69, and 115/80, respectively). After the second egg of a clutch was laid, but before the third egg was laid, a thermistor attached to a Hobo Temp data logger was slowly worked into the nest from underneath until it was <5 mm above the nest lining. The thermistor was set <5 mm above the nest lining to prevent con- tact with the incubating female’s brood patch. Thermistors set higher than this level were usually discovered and physically removed by the female, and, on six occasions, the nest was abandoned. To minimize detection by incu- bating females and predators, data loggers were wrapped in plastic and concealed in veg- etation 2 to 6 m from the nest. Data loggers continuously recorded temper- ature variations at 2.5-min intervals for up to 13 consecutive days, which spanned the entire incubation period (a 2.5-min sampling inter- val was the shortest possible interval that PIG. I. (A) Temperature recorded at a single Red- winged Blackbird nest at a lagoon in Perth, Ontario over a 24-hr period, 2-3 June 2001. The overnight incubation session lasted from 19:53 to 06:53 EST. (B) An expanded 90-min section of this trace shows high nest temperature when the parent is incubating and sharply falling temperature during daytime foraging bouts when the nest is left unattended. Arrivals and departures of the incubating adult result in sudden, ob- vious changes in nest temperature. could be maintained for 1 3 days without over- loading the logger’s memory capacity). After hatching was complete (i.e., when 2 days had elapsed since the last egg hatched), data log- gers and thermistors were removed from nests. Incubation patterns were extracted after downloading data from loggers using Boxcar Pro 4.0 software (Onset Computer Co., Po- casset, Massachusetts). Because thermistors did not contact the female’s brood patch, but instead, recorded air temperature at the bottom of the nest bowl, recorded temperatures were lower than the 34-39° C temperatures re- quired for optimal embryo development (Fig. 1). Nonetheless, periods when a female was incubating versus absent from the nest showed Zimmerling and Ankney • INCUBATION PATTERNS OF RED- WINGED BLACKBIRDS 283 as clear peaks and troughs on the temperature traces, allowing times of arrival and departure to be estimated. We acknowledge that data re- garding time periods are estimates due to fac- tors such as lags in temperature changes and data loggers recording temperature every 2.5 min rather than continuously; however, com- bining a large number of readings {n = 6,300- 7,400) over the course of the incubation pe- riod, and considering that these factors should have affected birds similarly in pond and la- goon habitats, their effects should have been minimal. To verify that arrival and departure times were accurately discerned from temper- ature traces, we positioned video cameras (Sony 8 mm Handycams) 10 m from a subset of nests {n = 6) and video-recorded female incubation patterns for 1 hr (6 hr total). Com- parisons of video recordings and temperature ! traces (n = 144 data points) indicated that de- parture and arrival times at the nest were ac- curately identified from the temperature trac- j es. On the basis of these observations, we in- [ terpreted any drop in temperature of more than 4° C that occurred within a 5-min period as a departure from the nest (i.e., the start of a foraging bout). Any similar rise in temper- ature signified an arrival at the nest (initiating a bout of attentiveness). Hence, during the daytime (06:00-20:00 EST), duration of for- aging bout was calculated as the number of minutes between two successive bouts of at- tentiveness. Duration of attentiveness bout was calculated as the number of minutes be- tween two successive foraging bouts. Because 1 duration of attentiveness and foraging bouts may be influenced by number of foraging bouts, we calculated the number of foraging bouts/hr as the number of foraging bouts/total I hr of daylight. We also calculated incubation constancy (percentage of daytime spent incu- bating) as total duration of attentiveness bout I /(total duration of attentiveness bout + total ! duration of foraging bout) to evaluate whether , differences, if any, in duration of attentiveness I or foraging bouts and/or number of foraging bouts/hr influenced incubation constancy. Be- cause variation in the duration of overnight incubation could indicate differential use of endogenous reserves, we calculated overnight incubation as the number of minutes between returning to the nest for the last time in the evening and leaving the nest the first lime in the morning. Females never left the nest dur- ing the night. Temperature traces for nests with data log- gers confirmed that onset of incubation in Red-winged Blackbirds occurs with the laying of the penultimate egg (e.g., Yasukawa and Searcy 1995). For nests without data loggers, incubation onset was assumed to have oc- curred once the penultimate egg was laid, but was also confirmed by temperature of the clutch. Nine days after incubation onset, nests with and without data loggers were checked daily to determine hatch date. Because Red- winged Blackbird clutches sometimes hatch asynchronously (Yasukawa and Searcy 1995), nests were visited at least once daily during hatching to record the sequence of hatching and to determine length of the incubation pe- riod (calculated as the time between laying of the penultimate egg and when the majority of eggs had hatched). However, in 1999, some nests were monitored only every other day, in which case nestling age (± 6 hr) was esti- mated based on nestling size and wetness of their natal down (Zimmerling 2002). After hatching was complete, hatchability (i.e., number of eggs hatched/total number of eggs laid) was recorded. Between 3 and 18 June 2001, we quantified foraging behavior for a subset of incubating females = 7 and = 5) at two sew- age lagoons (one bordered by agricultural fields and one partially bordered by uplands) and three beaver ponds. Most birds in the study area were not color-banded, but we identified individual females by following them away from their nests when observing them during foraging bouts. Foraging obser- vations were conducted between ()7:()() and 12:00 and began when the female left the nest and ended when the female returned to the nest (one data point per individual). For each female, we recorded the habitat(s) in which she foraged (i.e., emergent vegetation, shore- line, or forest-edge) and mean distance of for- aging habitat(s) from the nest. Statistical analyses. — We obtained relative- ly few temperature traces that covered the en- tire incubation period of a nest = 19, '^porui ~ Statistical analysis, we includ- ed all temperature traces with a minimum of 8 days of continuous recording during incu- balion = 43, = 39) to increase 284 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 total sample size - 62, - 54). Incomplete temperature traces were usually the result of nest predation or the female re- moving the thermistor during incubation; these were excluded from the analysis. We calculated mean incubation constancy (%), mean number of foraging bouts/hr, mean bout duration of attentiveness (min) and foraging (min), and mean overnight incubation (min) for all temperature traces with >8 days of continuous recording. For analysis of incuba- tion period and hatchability, we combined da- tasets from nests with and without data log- gers (rii^goon ^ 138, ^ 107); To analyze hatchability, all eggs lost at active nests by causes other than hatching failure (i.e., pre- dation, drowning, nest collapse, or clutch de- sertion) were excluded. We used an information-theoretic approach for model selection (Burnham and Anderson 1998). We considered several a priori candi- date models for each response variable that included main effects and a subset of inter- actions that were of interest. Model selection was done using Akaike’s Information Criteri- on (AIC) with corrections for small sample size (AICc) using PROC MIXED (SAS Insti- tute, Inc. 2001) with the IC option for model estimation. Models were ranked using AAIC^ (Burnham and Anderson 1998) and were cal- culated as AAIC, = AIC,i - AIC,^i„ where AAIC^i was the model from a candidate set. Akaike weights (w,) were calculated to assess the relative likelihood of each model being the best model. Because we were interested in the effects of habitat-related differences in incubation pat- terns of female Red-winged Blackbirds, all candidate models included effects of habitat (lagoon versus pond) as an explanatory vari- able. Because incubation patterns in some spe- cies may vary temporally (e.g., Conway and Martin 2000b), year (coded 1, 2, 3 for 1999, 2000, and 2001, respectively) and nest-initia- tion date (date first egg was laid; May 1 = 1) were also used to generate a set of candidate models. Model selection was done separately for incubation period, incubation constancy, duration of foraging bout, foraging bouts/hr, duration of attentiveness bout, duration of overnight incubation, and hatchability, respec- tively. The set of candidate models was the same for each dependent variable and includ- ed effect of habitat (HAB), nest-initiation date (ID), year (YR), and all two-way interactions involving habitat. A null model (intercept only) was also included as a candidate model. Only candidate models with AAIC^ <2.0 are presented. When no candidate models had AAIC^ <2.0, second-best models are present- ed. RESULTS Incubation period. — The best model ex- plained 14% of variation in incubation period and included habitat (HAB), year (YR), and habitat-by-year interaction (HAB X YR) as predictors (Table 1). Likelihood of model fit for {HAB, YR, HAB X YR} was >9X that of the second-best model ({HAB, YR, ID, HAB X YR), AAIQ = 4.4). Incubation pe- riod was longer at ponds than at lagoons, but this difference varied with year. In 1999, in- cubation period was 0.8 days longer at ponds than at lagoons, but was only 0.2 days longer in each of the following 2 years. Incubation constancy. — The model {HAB} was superior to other models considered, and explained 9% of variation in incubation con- stancy (Table 1). Likelihood of model fit for {HAB} was >5X that of the second-best model ({HAB, YR, HAB X YR}, A AIC, = 3.5). Incubation constancy was 4% lower at ponds than at lagoons (69% versus 73%) and this difference did not vary with nest-initiation date or year. Duration of foraging bout. — The best mod- el explained 12% of variation in duration of foraging bout and included habitat (HAB), ini- tiation date (ID), and habitat-by-initiation date (HAB X ID) interaction as predictors (Table 1). Likelihood of model fit for {HAB, ID, HAB X ID} was >4X that of the second-best model ({HAB, ID}, AAIC, = 3.2). Duration of foraging bout averaged longer at ponds (8.9 min) than at lagoons (8.1 min) and the differ- ence increased with nest-initiation date. Foraging bouts/hr. — We found consider- able model-selection uncertainty for foraging bouts/hr and no predictors appeared particu- larly important (Table 1). Moreover, the null model, which contained no predictors, had the lowest AIC, score of any models. Even the most complex model {HAB, ID, YR, HAB X ID, HAB X YR} explained only 3% of vari- ation in foraging bouts/hr. Zimmerling and Ankney • INCUBATION PATTERNS OF RED- WINGED BLACKBIRDS 285 TABLE 1. Model selection for variation in incubation period^ (days), incubation constancy (%), duration of foraging bout (min), foraging bouts/hr, duration of attentiveness bout (min), duration of overnight incubation (min), and hatchability=‘‘’ of female Red-winged Blackbirds nesting at lagoons (n = 62) and at ponds {n = 54) in eastern Ontario, in relation to habitat (HAB, pond versus lagoon), nest-initiation date (ID, May 1 = 1), and year (YR, 1999-2001). Shown for each model are numbers of parameters (K), AIC difference with correction for small sample sizes (AAIC^), model weight (w,), proportion of variance explained {R^), and Least Square Means ± SE. Response variable Model K AAICc W/ Ponds Lagoons Incubation period HAB, YR, HAB X YR 7 0.0 0.896 0.14 12.4 -1- 0.1 12.0 ± 0.1 1999 12.7 -t- 0.1 11.9 ± 0.1 2000 12.6 0.1 12.4 ± 0.1 2001 12.1 + 0.1 11.9 ± 0.1 HAB, YR, ID, HAB X YR 8 4.4 0.099 0.15 12.4 0.1 12.0 ± 0.1 Incubation con- stancy HAB 3 0.0 0.851 0.09 69.3 -+- 0.1 73.4 ± 0.1 HAB, YR, HAB X YR 7 3.5 0.147 0.09 69.3 0.1 73.1 ± 0.1 Duration of forag- ing bout HAB, ID, HAB X ID 5 0.0 0.801 0.12 8.9 -+- 0.2 8.1 ± 0.2 HAB, ID 4 3.2 0.171 0.06 8.6 -+- 0.2 8.0 ± 0.2 Foraging bouts/hr NULL 2 0.0 0.689 0.00 HAB 3 1.8 0.280 0.01 2.2 -+- 0.1 2.1 ± 0.1 Duration of atten- tiveness bout HAB, ID 4 0.0 0.638 0.06 30.6 1.6 32.2 ± 1.5 HAB, ID, HAB X ID 5 1.4 0.316 0.06 30.6 -+- 1.5 32.1 ± 1.5 Duration of over- night incuba- tion NULL 2 0.0 0.883 0.00 HAB 3 3.2 0.059 0.01 537.5 11.5 545.1 ± 12.8 Hatchability NULL 2 0.0 0.916 0.00 HAB 3 4.8 0.083 0.01 87.8 -H 0.1 85.6 ± 0.1 “ Number of nests in model = 361 (161 pond, 200 lagoon). ^ Total number of eggs = 1,353 (581 pond, 772 lagoon). Duration of attentiveness bout. — The model (HAB, ID} was superior to other models con- sidered and explained 6% of variation in du- ration of attentiveness bout (Table 1). Likeli- hood of model fit for (HAB, ID} was 2X that of the second-best model ({HAB, ID, HAB X ID}, AAIC^ = 1.4), which also contained nest- I initiation date as a predictor. Duration of at- I tentiveness bout was 1.6 min shorter at ponds ! than at lagoons. Regardless of habitat, the du- : ration of attentiveness bout increased by 0.3 I min for each later day of nest initiation. Duration of overnight incubation. — There - was considerable model-.selection uncertainty I for duration of overnight incubation and no predictors appeared particularly important (Table 1). Moreover, the null model, which ^ contained no predictors, had the lowest A IQ ■ score of any models considered. Even the most complex model (HAB, ID, YR, HAB X ID, HAB X YR} explained only 2% of vari- ation in duration of overnight incubation. Hatchability. — Model selection for varia- tion in egg hatchability was equivocal and no predictors in the set of candidate models ap- peared important (Table 1). Moreover, the null model, which contained no predictors, had the lowest AIQ score of any models considered. Furthermore, among the set of candidate mod- els, the most complex model {HAB, ID, YR, HAB X ID, HAB X YR} explained only 3% of the variation in hatchability. Foraging behavior. — Incubating females nesting at ponds foraged >2X farther away from their nests than did females nesting at lagoons (94 ± 38 m versus 46 ± 23 m). At ponds, all five females foraged within forest edges, although one female was observed cap- turing a flying insect (Odonata) over emergent vegetation. At lagoons, incubating females al- ways foraged within the emergent vegetation, but on three occasions, they also foraged along lagoon shorelines. 286 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 DISCUSSION Many studies have demonstrated that insect abundance is greater (or insects are more eas- ily acquired) at sewage lagoons than in other habitats (e.g., Swanson 1977, Piest and Sowls 1985, Porter 1993, Zimmerling 2002). Quin- ney (1983) showed that insect biomass at a sewage lagoon in southwestern Ontario was approximately 10 times greater than that at a nearby field habitat during the period when most Tree Swallows were incubating eggs. Many of these same studies also have revealed that the type of insects available to birds at sewage lagoons is different from that avail- able in other habitats (e.g., Swanson 1977, Quinney 1983, Zimmerling 2002). During brood-rearing, Zimmerling (2002) found that female Red- winged Blackbirds at sewage la- goons in eastern Ontario usually foraged close to their nests and captured numerous flying insects (Family Chironomidae), whereas fe- males at beaver ponds generally foraged much farther from their nests, often in adjacent up- lands, and usually returned to the nest with one and sometimes two large insects, often from the Family Noctuidae (Zimmerling 2002). Thus, presuming that insect availability and/or the type of insects available at lagoons and ponds were different, we could examine the response of Red-winged Blackbird incu- bation patterns, incubation period, and hatch- ability of eggs to habitat-related differences in foraging behavior. Incubation periods of Red- winged Black- birds at lagoons were shorter than those at ponds. Other investigators (see references in Martin 1987, Williams 1996, Hebert 2002) have suggested that shorter incubation periods are a consequence of increased attentiveness during incubation. At lagoons, incubation constancy was 4% higher than it was at ponds, but because substantial variation in Red- winged Blackbird incubation constancy (range = 65-72%) has been reported elsewhere (e.g., Holcomb 1974), these results should be inter- preted cautiously. Nonetheless, our results suggest that lower nest attentiveness at ponds compared with that at lagoons could be ex- plained by habitat-related differences in for- aging behavior, resulting in longer duration of foraging bouts and shorter duration of atten- tiveness bouts without changing the frequency of foraging bouts. For example, although our behavioral observations were limited, female blackbirds incubating at ponds — unlike fe- males at lagoons — did not forage within the emergent vegetation in close proximity to the nest; rather, they foraged much farther from the nest along forest-edges of woodlots bor- dering the ponds. Our behavioral observations of female foraging habits at ponds were sim- ilar to those found in other studies: marsh- nesting female Red-winged Blackbirds spend much of their time foraging in uplands that border their nesting habitat (e.g., Orians 1980, 1985; Whittingham and Robertson 1994; Turner and McCarty 1998) because of limited food availability within the marsh. It seems unlikely that food availability was limited within sewage lagoons in our study area be- cause, even at the lagoon bordered by upland habitat, females were observed foraging only in the emergent vegetation and/or along the shoreline. Although it was not possible to taxonomi- cally categorize insects taken by foraging fe- males during incubation, other studies in east- ern Ontario have revealed that, during the brood-rearing period, females that foraged in upland habitats consistently delivered lepidop- teran larvae to their broods (Bendell and Weatherhead 1982, Zimmerling 2002). Less than 65 km from our study area, Bendell and Weatherhead (1982) showed that female Red- winged Blackbirds fed lepidopteran larvae of the family Noctuidae (55% by volume) to their nestlings, of which larvae of a single species, Amphipoea velata (Walker), made up 31% of the total volume. In contrast, female passerines nesting at sewage lagoons feed nestlings chironomid adults (Quinney 1983, Zimmerling 2002), the most abundant insect at lagoons (Swanson 1977, Hussell and Quin- ney 1987). It is possible that female Red- winged Blackbirds incubating at ponds were searching for lepidopteran larvae in the upland habitats during foraging bouts, and, because many lepidopterans are cryptically colored, additional search time may have been required for females to find these insects. Therefore, female Red-winged Blackbirds foraging in up- land habitats in eastern Ontario may have in- curred costs associated with increased travel time and energy expenditure for food gather- ing, which may have resulted in longer for- Zimmerling and Ankney • INCUBATION PATTERNS OF RED- WINGED BLACKBIRDS 287 aging bouts, shorter bouts of attentiveness, and, ultimately, longer incubation periods. We found annual variation in incubation patterns and incubation period, which may have been attributable to annual environmen- tal variability. We are aware of only two stud- ies of passerines that assessed annual variation in food supply and incubation patterns (Drent et al. 1985, Moreno 1989). Moreno (1989) found that, during the coldest year of his study, incubation length was negatively cor- related with the amount of supplemented food he provided to incubating female Northern Wheatears. Similarly, Drent et al. (1985) found that when European Starlings’ (Sturnus vulgaris) principle prey, crane fly larvae {Ti- pula paludosa), were scarce, incubating fe- males responded by decreasing incubation constancy and increasing the length of forag- ing bouts. Relatively warm spring tempera- tures in 1999 in eastern Ontario may, in part, explain the nearly 1-day difference in incu- bation period between lagoons and ponds in 1999 compared with 2000 and 2001. Mean monthly temperature for May 1999 was 16.5° C, which was 3° and 2° C warmer than in 2000 and 2001, respectively. It is unlikely that an- nual variation in incubation period and differ- ences observed between lagoons and ponds were the direct result of ambient temperature because both habitat types were sampled throughout eastern Ontario. Instead, differenc- es in incubation period may have been due to habitat-related differences in type and/or abundance of insects available to incubating females. For example, the largest emergence of chironomids at two lagoon sites in eastern Ontario occurred 6 and 4 days earlier in 1999 than in 2000 and 2001 , respectively (JRZ pers. obs.). Regardless, we did not assess dietary habits of incubating females (neither were they assessed in other studies of Red-winged Blackbirds); thus, we cannot preclude the pos- sibility that other factors were responsible for annual variation in incubation period within and between habitats. The importance of habitat and food avail- ability in affecting seasonal variation in pas- serine incubation patterns is equivocal be- cause nest attentiveness is positively correlat- ed with ambient temperature in north-temper- ate environments (Zerba and Morton 1983, Conway and Martin 2()()()a). Conway and Martin (2000a) proposed that the metabolic energy required by small birds during incu- bation decreases with increased ambient tem- perature and should allow individuals to in- crease length of attentiveness bouts because they are metabolizing energy reserves more slowly. In our study, duration of attentiveness bout increased with nest-initiation date, which was a proxy for increasing ambient tempera- tures during spring and summer. Food avail- ability also may have increased (whether di- rectly or indirectly) with ambient temperature during May, when the majority of females were incubating (also see Quinney 1983). Thus, increased rates of food acquisition (in response to increased food availability) may explain the decline in duration of foraging bout with nest-initiation date in both habitats. Not surprisingly, because of inherent difficul- ties in separating the effects of ambient tem- perature and food availability, few passerine studies, including ours, have unambiguously demonstrated a relationship between seasonal changes in incubation patterns and food avail- ability. It is possible that incubation patterns of fe- male Red- winged Blackbirds did not differ between wetland habitats due to differential female foraging habits, but, rather, to differ- ences in female age, female body size, nest predation, or the use of endogenous reserves. However, Red-winged Blackbird populations at lagoons and ponds in our study area were similar with respect to female age structure, body mass, and structural size (Zimmerling 2002). Moreover, Wheelwright and Beagley (2005) suggested that incubation behavior in Savannah Sparrows {Passerculus samiwich- ensis) is largely innate and unaffected by prior reproductive experience or other age-related variables. Other studies have suggested that predation risk can be an important factor in- lluencing incubation behavior in some passer- ines (e.g., Ghalambor and Martin 2002, Mar- tin 2002). However, in eastern Ontario, the proportion of Red-winged Blackbird nests depredated during incubation at beaver ponds, sewage lagoons, and roadside ditches (which resemble lagoons in vegetation structure) was similar, despite differences in primary preda- tors (i.e., avian versus mammalian) in each habitat (JRZ unpiibl. data). Although little is known about use of endogenous reserves by 288 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 incubating passerines, most studies indicate that passerines use exogenous nutrients for in- cubation (see Williams 1996, Conway and Martin 2000b). Some studies have shown mass loss by incubating females, but that may have been due to post-laying atrophy of re- productive organs rather than to loss of so- matic tissue (Ricklefs and Hussell 1984). Moreover, overnight incubation represents a prolonged period of fasting coinciding with minimum daily ambient temperatures; there- fore, if endogenous reserves were used more heavily by Red-winged Blackbirds at lagoons than at ponds, then duration of overnight in- cubation should have been longer at lagoons, but it was not. To better assess whether en- dogenous reserves were used differentially during incubation by female Red-winged Blackbirds nesting at lagoons, researchers should compare levels of endogenous reserves between onset and termination of overnight incubation. In some species, shorter incubation periods and bouts of attentiveness can improve hatch- ing success, which is influenced by tempera- ture of eggs during incubation (Lyon and Montgomerie 1985, Nilsson and Smith 1988, Strausberger 1998; but see Eikenaar et al. 2003). We did not, however, detect a differ- ence in hatchability of Red- winged Blackbird eggs between lagoons and ponds (85.6% ver- sus 87.8%). Unlike some passerines that nest in the high arctic and take long foraging bouts (i.e., 20 min; Lyon and Montgomerie 1985, 1987), female Red-winged Blackbirds nesting at both lagoons and ponds generally took short foraging bouts (i.e., <10 min; also see Holcomb 1974), perhaps explaining the simi- larity in egg hatchability between habitat types. In other studies of Red- winged Black- birds, egg hatchability ranged from 87.9% (Williams 1940) to 97.0% (Young 1963). It is possible that when egg size measurements were taken (for another study), some of the eggs in this study were damaged (dimpled or hairline cracked) by calipers, thus accounting for the relatively low hatchability of Red- winged Blackbird eggs in both habitats. Comparisons of Red-winged Blackbirds nesting in two different habitats — sewage la- goons and beaver ponds — in eastern Ontario suggested that differences in incubation peri- ods, incubation constancy, and bout duration of attentiveness and foraging may have been responses to differential foraging habits, pos- sibly as a result of differences in food acqui- sition during incubation. Differences in for- aging habits, however, did not affect hatch- ability. Until further research and experimen- tal work is extended to many other species, it will be difficult to judge the importance of variation in foraging habits and/or food ac- quisition in influencing incubation patterns and hatchability in passerines. ACKNOWLEDGMENTS We would like to thank R. C. Bailey and J. S. Millar for providing helpful comments on earlier versions of this manuscript. Three anonymous reviewers provided invaluable suggestions that improved this manuscript. Financial support was provided by the University of Western Ontario and by a Natural Sciences and Engi- neering Research Council Postgraduate Scholarship to JRZ and an operating grant to CDA. We are grateful for the field assistance provided by S. W. Meyer, G. E. Craigie, D. C. McIntosh, K. Ash, C. A. Debruyne, B. Frei, T Talvila, and J. M. Zimmerling. LITERATURE CITED Bendell, B. E. and P. j. Weatherhead. 1982. Prey characteristics of upland-breeding Red-winged Blackbirds {Agelaius phoeniceus). Canadian Field-Naturalist 96:265-271. Burnham, K. P. and D. R. Anderson. 1998. Model selection and inference: a practical information- theoretic approach. Springer- Verlag, New York. Clark, A. B. and D. S. Wilson. 1981. Avian breeding adaptations: hatching asynchrony, brood reduction and nest failure. Quarterly Reviews of Biology 56: 254-277. Conway, C. J. and T. E. Martin. 2000a. Effects of ambient temperature on avian incubation behavior. Behavioral Ecology 11:178-188. Conway, C. J. and T. E. Martin. 2000b. Evolution of passerine incubation behavior: influence of food, temperature, and nest predation. Evolution 54: 670-685. Drent, R. H. 1975. Incubation. Pages 333-420 in Avi- an biology (D. S. Earner and J. R. King, Eds.). Academic Press, New York. Drent, R. H., J. Tinbergen, and H. Biebach. 1985. Incubation in the starling {Sturnus vulgaris): res- olution of the conflict between egg care and for- aging. Netherlands Journal of Zoology 35:103- 123. Eikenaar, C., M. L. Berg, and J. Komdeur. 2003. Experimental evidence for the influence of food availability on incubation attendance and hatching asynchrony in the Australian Reed Warbler Ac- rocephalus australis. Journal of Avian Biology 34:419-427. Zimmerling and Ankney • INCUBATION PATTERNS OF RED-WINGED BLACKBIRDS 289 Ghalambor, C. K. and T. E. Martin. 2002. Compar- ative manipulation of predation risk in incubating birds reveals variability in the plasticity of re- sponses. Behavioral Ecology 13:101-108. Haftorn, S. 1978. Egg-laying and regulation of egg temperature during incubation in the Goldcrest (Regulus regulus). Ornis Scandinavia 9:2-21. Hebert, P. N. 2002. Ecological factors affecting initi- ation of incubation behaviour. Pages 271-279 in Avian incubation: behaviour, environment and evolution (D. C. Deeming, Ed.). Oxford Univer- sity Press, London, United Kingdom. Holcomb, L. C. 1974. Incubation constancy in the Red-winged Blackbird. Wilson Bulletin 86:450- 460. Hussell, D. J. T. and T. E. Quinney. 1987. Food abun- dance and clutch size of Tree Swallows {Tachy- cineta bicolor). Ibis 129:243-258. Kendeigh, S. C. 1952. Parental care and its evolution in birds. Illinois Biological Monographs, no. 22. University of Illinois Press, Urbana. Lyon, B. E. and R. D. Montgomerie. 1985. Incuba- tion feeding in Snow Buntings: female manipu- lation or indirect male parental care? Behavioral Ecology and Sociobiology 17:279-284. Lyon, B. E. and R. D. Montgomerie. 1987. Ecolog- ical correlates of incubation feeding: a compara- tive study of high arctic finches. Ecology 68:713- 722. Martin, T. E. 1987. Food as a limit on breeding birds: a life-history perspective. Annual Reviews of Ecology and Systematics 18:453-487. Martin, T. E. 2002. A new view of avian life-history evolution tested on an incubation paradox. Pro- ceedings of the Royal Society of London, Series B 269:309-316. Martin, T. E. and C. K. Ghalambor. 1999. Males feeding females during incubation. I. Required by microclimate or constrained by nest predation? American Naturalist 153:131-139. Moreno, J. 1989. Energetic constraints on uniparental incubation in the Wheatear (Oenanthe oenanthe L.). Ardea 77:107-1 15. Nilsson, J. and H. G. Smith. 1988. Incubation feeding as a male tactic for early hatching. Animal Be- haviour 36:641-647. Orians, G. H. 1980. Some adaptations of marsh-nest- ing blackbirds. Princeton University F’ress, Prince- ton, New Jersey. Orians, G. H. 1985. Blackbirds of the Americas. Uni- versity of Washington F^ress, Seattle. Pearse, a. T, j. F^ Cavut, and J. F{ Cully, Jr. 2004. Effect of food supplementation on female nest at- tentiveness and incubation mate feeding in two sympatric wren species. Wilson Bulletin 1 16:23- 30. PiEST, L. A. and I.. K. vSowLS. 1985. Breeding duck use of a sewage marsh in Arizona. Journal of Wildlife Management 49:580-585. F’orter, M. S. 1993. The potential for conqx'tition be- tween Black Ducks and Mallards in Ontario. M.Sc. thesis. University of Guelph, Guelph, Can- ada. Quinney, T. E. 1983. Food abundance and Tree Swal- low breeding. Ph.D dissertation. University of Western Ontario, London, Canada. Radford, A. N. 2004. Incubation feeding by helpers influences female nest attendance in the Green Woodhoopoe (Phoeniculus purpureas). Behavior- al Ecology and Sociobiology 55:583-588. Reid, J. M., P. Monaghan, and G. D. Ruxton. 1999. The effect of clutch cooling on starling, Sturnus vulgaris, incubation strategy. Animal Behaviour 58:1161-1167. Reid, J. M., G. D. Ruxton, P. Monaghan, and G. M. Hilton. 2002. Energetic consequences of clutch temperature and clutch size for a uniparental in- termittent incubator: the starling. Auk 1 19:54-61. Ricklefs, R. E. and D. J. T. Hussell. 1984. Changes in adult mass associated with the nesting cycle in the European Starling. Ornis Scandinavia 15:155- 161. Sanz, J. J. 1996. Effect of food availability on incu- bation period in the Pied Flycatcher (Ficedula hy- poleuca). Auk 113:249-253. SAS Institute, Inc. 2001. SAS user’s guide, ver. 8.01. SAS Institute, Inc., Cary, North Carolina. Strausberger, B. M. 1998. Temperature, egg mass, and incubation time: a comparison of Brown- headed Cowbirds and Red-winged Blackbirds. Auk 115:843-850. Swanson, G. A. 1977. Diel food selection by Anatinae on a waste-stabilization system. Journal of Wild- life Management 41:226-231. Thomson, D. L., P. Monaghan, and R. W. Furness. 1998. The demands of avian incubation and avian clutch size. Biological Reviews 73:293-304. Turner, A. M. and J. P. McCarty. 1998. Resource availability, breeding site selection, and reproduc- tive success of Red-winged Blackbirds. Oecologia 1 13:140-146. VISSER, M. E. AND C. M. Lessells. 2001. The costs of egg production and incubation in Great Tits {Par- us major). Proceedings of the Royal Society of London, Series B 268:1271-1277. Weathers, W. W. and K. A. Sullivan. 1989. Ne.st attentiveness and egg temperature in the Yellow- eyed Junco. Condor 91:628-633. Webb, F^. R. 1987. Thermal tolerance of avian embry- os: a review. Condor 89:874-898. Wheelwright, N. T. and J. C. Beagley. 2005. FYofi- cient incubation by inexperienced Savannah Spar- rows (Passerculus sandwichensis). Ibis 147:67- 76. Whutingham, L. A. and R. J. Rober.son. 1994. F^'ood availability, parental care and male mating success in Red-winged Blackbirds {Agelaius phoeniccus). Journal of Animal Fxology 63:139 150. Wii LIAMS, J. B. 1991. On the importance of energy consiileration to small birds with gyneparcntal in- termittent incubation. Acta ('ongressus Interna- tionalis Ornithologici 20:19f>4 1975. 290 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 Williams, J. B. 1996. Energetics of avian incubation. Pages 375-415 in Avian energetics and nutritional ecology (C. Carey, Ed.). Chapman and Hall, Lon- don, United Kingdom. Williams, J. E 1940. The sex ratio of nestling Eastern Red-wings. Wilson Bulletin 52:267—277. Yasukawa, K. and W. a. Searcy. 1995. Red-winged Blackbird (Agelaius phoeniceus). The Birds of North America, no. 184. Young, H. 1963. Age-specific mortality in the eggs and nestlings of blackbirds. Auk 80:145—155. Zerba, E. and M. L. Morton. 1983. Dynamics of in- cubation in Mountain White-crowned Sparrows. Condor 85:1-1 1. ZIMMERLING, J. R. 2002. Comparative reproductive performance of Red-winged Blackbirds nesting on sewage lagoons and on natural wetlands in eastern Ontario. Ph.D. dissertation. University of Western Ontario, London, Canada. Wilson Bulletin 1 17(3):291-295, 2005 SEASONAL VARIATION IN ACTIVITY PATTERNS OE JUVENILE LILAC-CROWNED PARROTS IN TROPICAL DRY EOREST ALEJANDRO SALINAS-MELGOZAi ^ ^ AND KATHERINE RENTON^ ABSTRACT. — We used radio-telemetry techniques to determine hourly activity patterns of 29 juvenile Lilac- crowned Parrots (Amazona finschi) during 1996-2000 in tropical dry forest of Jalisco, Mexico. Parrots had two peak activity periods — early morning and late afternoon — for both overall activity and local movement. Indi- viduals were generally inactive and did not change location for 5-6 hr during the middle of the day. Parrots were more active in the dry season than in the rainy season, although movements resulting in a change of location did not vary between seasons. Seasonal variations in activity of Lilac-crowned Parrots may be related to variations in food availability or temperature. Activity patterns of parrots need to be considered when eval- uating habitat use or survey data. Received 1 October 2004, accepted 26 April 2005. When evaluating habitat use, the time of day and the activity being performed by an animal need to be considered, because animals select particular habitats for specific types of activity (Palomares and Delibes 1992). Often, however, studies of habitat use do not take into account activity or inactivity of the indi- vidual (Palomares and Delibes 1992). Daily activity patterns of psittacines have been estimated indirectly from survey data on the frequency of flock encounters, with greater flock activity occurring in the early morning and late afternoon (Snyder et al. 1987, Gilardi and Munn 1998, Wirminghaus et al. 2001), although smaller parrot species may be active throughout the day (Pizo et al. 1997, Gilardi and Munn 1998). Survey data offer an ap- proximation of activity patterns for a species at the population level, but may be limited by the varying detectability of individuals at cer- tain times of the day, or biased toward above- ’ canopy flight characteristics of large flocks. Direct techniques, such as radio-telemetry, of- \ fer the opportunity to follow an individual and track its behavior throughout the day, but these techniques have been used infrequently for parrots (Lindsey et al. 1991). The Lilac-crowned Parrot (Amazontt fin- .schi) is a threatened species (Diario Oficial dc ' F'linclacion Hcologica de Ciiixmala A.C., A.P. 161. San Patricio Mclac|iic, .lalisco, C.l’. 4S9S0, Mexico. ^ ^ H^stacion de Biologfa Chamela, Institiito de Biolo- , gfa, Universidad Nacional Aiitonoma de Mexico, A.P. 21, San Patricio, .lali.sco, C.P. 4K9S0, Mexico. I ’ C'urrent address: Dept, of Biology, New Mexico 1 State Univ.. I, as Cruces. NM 8S(X).3, USA. j ■‘Corresponding author; e-mail: aaleJandrosCo'' yahoo.com. mx la Federacion 2002) endemic to the Pacific slope of Mexico (Forshaw 1989). Observa- tions of nesting Lilac-crowned Parrots dem- onstrate that breeding pairs make only two foraging visits to the nest per day: in the early morning and late afternoon (Renton and Sa- linas-Melgoza 1999). The Red-crowned Parrot {Amazona viridigenalis) in northeastern Mex- ico also makes only two foraging trips to the nest per day (Enkerlin-Hoeflich and Hogan 1997). It is unknown, however, whether these visits reflect general activity periods for par- rots, or are specific to nesting pairs. We used radio-telemetry techniques to determine hour- ly activity patterns of individual Lilac- crowned Parrots in tropical dry forest during both the dry and the rainy seasons. METHODS We conducted our study from 1 996 to 2000 in the tropical dry forest of the 13,142-ha Re- serva de la Biosfera de Chamela-Cuixmala (19°22'N, 104° 56' W to 19°35'N, 105° 03' W), Jalisco, on the Pacific coast of Mexico. The topography of the reserve is hilly, and is dominated by tropical dry deciduous forest with semi-deciduous forest in the larger drain- ages and more humid valleys (Lott 1993). Mean annual precipitation at the study site is 748 mm, with 85% of rainfall occurring from June to October; there is a prolonged drought from mid-L'ebruary to late May (Bullock 1986). During 1 996-2()0(), mean monthly temperatures were 23.6 ± 0.27° C (SE) in the dry season (January-May), and 26.9 ± 0.33° C in the rainy .season (.luly-November). Wc fitted radio-transmitters (model SI-2C; llolohil .Systems, Carp, Ontario, Canada) onto 291 292 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 Lilac-crowned Parrot chicks 10 days before fledging, permitting individuals to become ac- customed to transmitter collars. Each radio- transmitter was encased in a brass cylinder with a 1 13-kg-test whip antenna, and crimped, copper tube attachments for the collar (Mey- ers 1996). Radio-collars weighed 11 g, cor- responding to 3% of body weight (Ken ward 1987, Renton 2002). Transmitter pulse rate was set at 0.6 p/sec, with a battery life of 12 months. We used TRX-IOOOS receivers (Wild- life Materials, Inc., Carbondale, Illinois), and located radio-collared parrots by triangulation of simultaneous readings from two of three, fixed telemetry stations (Nam and Boutin 1991). Each telemetry station was fitted with two 1 1 -element, H-type antennas and a null- peak system (AVM, Inc., Isanti, Minnesota), providing a signal detection range of 10—15 km, with an error estimate of 1.4 degrees. Over the 5 years of study, we obtained ac- tivity data on 29 juvenile parrots {n = 7, 4, 3, 12, and 3 parrots in 1996, 1997, 1998, 1999, and 2000, respectively). Activity readings of parrots were not determined until 1-2 months after fledging — once juveniles began moving with adult flocks and their behavior reflected that of adult birds (Salinas-Melgoza 2003). Telemetry sessions were conducted during both the rainy (July-November) and dry (Jan- uary-May) seasons. Few telemetry sessions were conducted in December, and few suc- cessful telemetry sessions could be conducted in June due to seasonal migration of parrots out of the study site (Renton and Salinas-Mel- goza 2002). Activity patterns were determined by conducting 13-hr telemetry sessions from the fixed stations, by recording the activity of individuals per hour after sunrise (approxi- mately 06:30-19:30 [CST] in the dry season and 07:30-20:30 in the rainy season). Con- secutive readings were taken in each hourly period to determine whether individuals changed location within the hour. Loss of sig- nal with transmitter age and dispersal move- ments of parrots frequently made detection of individuals difficult; thus, not all telemetry sessions produced activity readings. Transmitters did not have an activity sen- sor; therefore, the activity status of each in- dividual was determined by maintaining the antenna in the peak signal direction and reg- istering the level of signal intensity. An indi- vidual was recorded as active when we reg- istered fluctuations in signal intensity of >0.05 dc milliamperes variation, caused by the individual changing position. We defined two activity categories: (1) rest: individuals with constant, unvarying signal intensity and no change in location or direction angle; and (2) active: individuals with a fluctuating signal intensity, or which changed location or signal direction. We recorded the number of individ- uals at rest or active during each hourly pe- riod, with the sum of the two categories being the total number of individuals recorded for that hour. To evaluate local movements in- volving flight, a subset of those individuals from the active category that registered a change in location or signal direction, was also defined as moving. Activity patterns were determined as the proportion of individuals per hour registered as active, as well as the subset of individuals in the active category that changed location and may be considered moving. We used the Kolmogorov-Smimov test of normality with Lilliefors significance correc- tion (Zar 1 999) to determine whether the data deviated significantly from the normal distri- bution required for parametric analysis. The proportions of individuals registered as active per hour in the dry and rainy seasons were arcsine transformed (Zar 1999) and presented a normal distribution {K-S2e ~ 0.13, P = 0.20). We used a paired r-test to compare ac- tivity by hour after sunrise between the dry and rainy seasons. Arcsine-transformed pro- portions for the subset of individuals that changed locations were not normally distrib- uted; therefore, the nonparametric Wilcoxon paired-sample test was used to compare movement between seasons, by hour after sunrise. Data are presented as means ± SE; significance level was set at P < 0.05. RESULTS Parrot activity was recorded for 845 hr of telemetry sessions, with 573 hr during the rainy season (July-November) and 272 hr in the dry season (January— May). Not all indi- viduals could be recorded in all telemetry ses- sions, but we obtained 2,292 activity readings of individual juvenile parrots. Fewer telemetry sessions and activity readings were obtained during the dry season (505 readings) than in Salinas-Melgoza and Renton • SEASONAL VARIATION IN PARROT ACTIVITY 293 Hours after sunrise FIG 1 . Percent of individual Lilac-crowned Parrots active (dashed line) and changing location (continuous line) per hour after sunrise in (A) the dry season and (B) the rainy season in the Reserva de la Biosfera de Chamela-Cuixmala, Jalisco, Mexico, 1996-2000. the rainy season (1,787 readings), due to sig- nal loss as transmitters aged and the broad dis- persal of parrots during the dry season (Sali- nas-Melgoza 2003), which made detection difficult. Individuals were followed for 271 ± 27.6 days (range = 55-552, n = 29) until the battery died or the signal was lost. Most ac- tivity readings were of first-year juvenile par- rots; only six individuals were followed >1 year, providing 117 readings that correspond to subadults 13-18 months of age. Activity patterns of Lilac-crowned Parrots showed two peaks — both for overall activity and when changing location (Fig. 1). Peak ac- tivity of individuals occurred in the first 3-4 hr after sunrise and last 4 hr before sunset (Fig. 1), corresponding to the approximate time periods of 06:30-1 0:30 and 15:30-19:30 in the dry season, and 07:30-10:30 and 16:30- 20:30 in the rainy season. Local movements of individuals changing location occurred in the first 3 hr after sunrise and last 2 hr before sunset (Fig. 1), approximately 06:30 to 09:30 and 17:30 to 19:30 in the dry season, and 07:30 to 10:30 and 18:30 to 20:30 in the rainy season. During a large part of the day (1 1:00- 16:00), parrots demonstrated low levels of ac- tivity and did not change location (Fig. 1). Peak periods in the early morning and late af- ternoon for active and moving individuals were similar in both the dry and rainy seasons. However, the percent of individuals active in the dry season (all-day mean = 62.7% ± 9.57) was greater than in the rainy season (all- day mean = 54.2% ± 9.28), with significant variation between seasons in the proportion of individuals active per hour of the day (paired t\2 = 2.7, P < 0.019; Fig. 1). By comparison, the percent of individuals that changed loca- tion per hour of the day did not vary signifi- cantly between seasons (all-day mean for dry season = 23.5% ± 7.33, rainy season = 18.9% ± 6.12; Zi3 = 1.13, P = 0.26). DISCUSSION Individual Lilac-crowned Parrots had two periods of peak activity — during the first 4 hr of the morning and the last 3 hr of the after- noon— when parrots are most likely to be for- aging (Snyder et al. 1987). Peak movements of individuals in the early morning and late afternoon corresponded with the behavior of parrot flocks traveling between communal roost sites and foraging areas (Renton and Sa- linas-Melgoza 2002). Peak periods of activity and movements of individuals in the early morning and late afternoon make these the times of day when parrots are most likely to be detected during surveys, and correspond with the activity patterns estimated from sur- vey data (Snyder et al. 1987, Gilardi and Munn 1998). Moreover, the same activity pe- riods were observed for nesting parrots (En- kerlin-Hoellich and Hogan 1997, Renton and Salinas-Melgoza 1999) and may reflect a gen- eral activity pattern irrespective of the age group or reproductive status of individuals. Because Lilac-crowned Parrots are inactive for 5-6 hr of the day, periods of rest or activ- ity by parrots need to be considered when us- ing radio-telemetry data to evaluate habitat use. Habitat selected for resting likely differs from that for foraging because cover and se- curity are more ifiiportant when resting. 294 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 whereas food availability is more important when foraging (Palomares and Delibes 1992). Failure to take activity into account creates bias in estimates of habitat use, particularly for animals that spend part of the day inactive, because foraging habitat will be underesti- mated (Palomares and Delibes 1992). The low activity exhibited by Lilac- crowned Parrots during part of the day may be related to diet, suggesting that parrots are able to meet their nutritional requirements by foraging during a few hours in the morning and afternoon. The Lilac-crowned Parrot is predominantly granivorous and exploits local- ly abundant seed resources (Renton 2001). Seeds are high in proteins and minerals (Gi- lardi 1996) and require longer digestion peri- ods, with consequently greater time between feeding sessions (Karasov 1990, Levey and Martinez del Rio 2001). Frugivorous birds, by comparison, have rapid transit times of fruit in the gut, with a consequent increase in con- sumption rate (Levey and Karasov 1989, Mar- tinez del Rio and Restrepo 1993). Hence, gra- nivorous Lilac-crowned Parrots may be able to meet their energetic needs in a few feeding bouts throughout the day. The seasonal variation in activity levels of Lilac-crowned Parrots may be related to sea- sonal changes in food resource availability (Renton 2001). Decreased food availability in the dry season (Renton 2001) may require parrots to increase time spent foraging to ob- tain sufficient food resources. Anecdotal ob- servations of parrots in the Australian wheat- belt suggest that parrots increase time spent foraging when food availability is low (Row- ley 1990, Rowley and Chapman 1991). Av- erage monthly temperatures also are greater in the rainy season than in the dry season and may influence parrots to seek cover or con- serve energy by decreasing activity during the warmer months. However, we obtained fewer activity records of Lilac-crowned Parrots dur- ing the dry season than in the rainy season, because the broad dispersal of parrots during the dry season (Salinas-Melgoza 2003) made individuals more difficult to detect. By com- parison, the pattern of changing locations did not vary between seasons, because these movements tend to reflect local flights be- tween roosting and foraging sites — a consis- tent element of Lilac-crowned Parrot behavior. ACKNOWLEDGMENTS The study would not have been possible without the logistical and financial support of the Eundacion Ecol- ogica de Cuixmala in Mexico, and the Denver Zoo- logical Foundation. We thank the Secretaria del Medio Ambiente y Recursos Naturales who granted permits for the research. ASM was supported by grants from the Eundacion Ecologica de Cuixmala and the Consejo Nacional de Ciencia y Tecnologia. D. E. Biggins and B. J. Miller designed and error-estimated the fixed te- lemetry stations. We are grateful to B. J. Miller, R. Nunez, D. Valenzuela, and S. Vasquez for assistance with telemetry sessions. Climate data were provided by the Estacion de Biologia Chamela of the Instituto de Biologia, Universidad Nacional Autonoma de Mex- ico (UNAM). The Instituto de Biologia, UNAM, and the Eundacion Ecologica de Cuixmala provided facil- ities for the preparation of this manuscript. We are grateful to J. W. Wiley and two anonymous reviewers for their constructive comments on the manuscript. LITERATURE CITED Bullock, S. H. 1986. Climate of Chamela, Jalisco and trends in the south coastal region of Mexico. Ar- chives for Meteorology, Geophysics, and Biocli- matology, Series B 36:297—316. Diario Oficial de la Federacion. 2002. Norma Ofi- cial Mexicana NOM— 059— ECOL— 2001. Protec- cion ambiental-especies nativas de Mexico de flo- ra y fauna silvestres-categorias de riesgo y espe- cificaciones para su inclusion, exclusion o cam- bio-lista de especies en riesgo. D.O.E, 6 March 2002. Mexico D.E, Mexico. Enkerlin-Hoeflich, E. C. and K. M. Hogan. 1997. Red-crowned Parrot {Amazona viridigenalis). The Birds of North America, no. 292. Forshaw, j. M. 1989. Parrots of the world, 3rd ed. Lansdowne Editions, Melbourne, Australia. Gilardi, j. D. 1996. Ecology of parrots in the Peruvian Amazon: habitat use, nutrition and geophagy. Ph.D. dissertation. University of California, Davis. Gilardi, J. D. and C. A. Munn. 1998. Patterns of ac- tivity, flocking, and habitat use in parrots of the Peruvian Amazon. Condor 100:641-653. Karasov, W. H. 1990. Digestion in birds: chemical and physiological determinants and ecological im- plications. Studies in Avian Biology 13:391—415. Kenward, R. 1987. Wildlife radio tracking, equip- ment, field techniques and data analysis. Academ- ic Press, London, United Kingdom. Levey, D. J. and W. H. Karasov. 1989. Digestive re- sponses of temperate birds switched to fruit or in- sect diets. Auk 106:675—686. Levey, D. J. and C. Martinez del Rio. 2001. It takes guts (and more) to eat fruit: lessons from avian nutritional ecology. Auk 118:819—830. Lindsey, G. D., W. J. Arendt, J. Kalina, and G. W. Pendleton. 1991. Home range and movements of juvenile Puerto Rican Panots. Journal of Wildlife Management 55:318-322. Salinas-Melgoza and Renton • SEASONAL VARIATION IN PARROT ACTIVITY 295 Lott, E. J. 1993. Annotated checklist of the vascular flora of the Chamela Bay region, Jalisco, Mexico. Occasional Papers of the California Academy of Science, no. 148. Martinez del Rio, C. and C. Restrepo. 1993. Eco- logical and behavioral consequences of digestion in frugivorous animals. Vegetatio 107/108:205- 216. Meyers, J. M. 1996. Evaluation of 3 radio transmitters and collar designs for Amazona. Wildlife Society Bulletin 24:15-21. Nam, V. O. and S. Boutin. 1991. What is wrong with error polygons? Journal of Wildlife Management 55:172-176. Palomares, F. and M. Delibes. 1992. Data analysis design and potential bias in radiotracking studies of animal habitat use. Acta Oecologia 13:221- 226. Pizo, M. A., I. SiMAO, AND M. Galetti. 1997. Daily variations in activity and flock size of two para- keets from southeast Brazil. Wilson Bulletin 109: 343-348. Renton, K. 2001. Lilac-crowned Parrot diet and food resource availability: resource tracking by a parrot seed predator. Condor 103:62-69. Renton, K. 2002. Influence of environmental variabil- ity on the growth of Lilac-crowned Parrot nest- lings. Ibis 144:331-339. Renton, K. and A. Salinas-Melgoza. 1999. Nesting behavior of the Lilac-crowned Parrot. Wilson Bul- letin 111:488-493. Renton, K. and A. Salinas-Melgoza. 2002. Amazona finschi (Sclater 1864) Loro corona lila. Pages 341-342 in Historia natural de Chamela (E A. No- guera, J. H. Vega Rivera, A. Garcia Aldrete, and M. Quezada Avendano, Eds.). Institute de Biolo- gfa, Universidad Nacional Autonoma de Mexico, Mexico. Rowley, I. 1990. Behavioural ecology of the Galah Eolophus roseicapillus in the wheatbelt of West- ern Australia. Surrey Beatty & Sons, Chipping Norton, New South Wales, Australia. Rowley, I. and G. Chapman. 1991. The breeding bi- ology, food, social organization, demography and conservation of the Major Mitchell or Pink Cock- atoo, Cacatua leadbeateri, on the margin of the Western Australian wheatbelt. Australian Journal of Zoology 39:211-261. Salinas-Melgoza, A. 2003. Dinamica espacio-tem- poral de individuos juveniles del loro corona lila {Amazona finschi) en el bosque seco de la costa de Jalisco. M.Sc. dissertation, Universidad Na- cional Autonoma de Mexico, Mexico City, Mex- ico. Snyder, N. E R., J. W. Wiley, and C. B. Kepler. 1987. The parrots of Luquillo: natural history and conservation of the Puerto Rican Parrot. Western Foundation of Vertebrate Zoology, Los Angeles, California. WiRMiNGHAUS, J. O., C. T. DowNS, M. R. Perrin, and C. T. Symes. 2001. Abundance and activity pat- terns of the Cape Parrot {Poicephalus robustus) in two Afromontane forests in South Africa. African Zoology 36:71-77. Zar, j. H. 1999. Biostatistical analysis, 4th ed. Prentice Hall, London, United Kingdom. Wilson Bulletin 1 17(3):296— 305, 2005 PARROT NESTING IN SOUTHEASTERN PERU: SEASONAL PATTERNS AND KEYSTONE TREES DONALD J. BRIGHTSMITH' ABSTRACT. Parrots that inhabit tropical lowland forests are difficult to study, are poorly known, and little information is available on their nesting habits, making analysis of community-wide nesting patterns difficult. I present nesting records for 15 species of psittacids that co-occur in southeastern Peru. The psittacid breeding season in this area lasted from June to April, with smaller species nesting earlier than larger species. Why smaller species bred earlier is uncertain, though it may be related to interspecific competition for nest sites or variations in food availability. This study identified two keystone plant resources used by nesting parrots: Dip- teryx micrantha (Fabaceae) and Mauritia flexuosa (Arecaceae). Local threats to these plant species are discussed. Received 25 August 2003, accepted 14 April 2005. Nesting is a critically important stage in the natural history of all bird species. Reproduc- tive failure has caused numerous conservation crises, so knowledge of nesting habits is crit- ical (Ratcliffe 1967, Herkert et al. 2003). The nesting ecology of many tropical species re- mains poorly documented, especially for can- opy nesters in dense, lowland tropical forests. The family Psittacidae is the most endangered large avian family in the world, making its study a conservation priority (Bennett and Owens 1997, Collar 1997). Most of our knowledge of parrot nesting comes from an- ecdotal accounts by early collectors (Huber 1933), regional avifaunal compendia (Cherrie 1916, Havershmidt 1968), detailed studies of individual taxa (reviewed in Masello and Quillfeldt 2002), and the monumental com- pendium of Forshaw (1989). New World parrot diversity is highest in the western Amazon Basin, where communities commonly include more than 15 species (Roth 1984, Montambault 2002). This diversity peaks in southeastern Peru, where 18 to 20 species have been reported at various sites (Terborgh et al. 1984, Foster et al. 1994). However, the nesting season for all but five species in the region remains undocumented, making community-level analyses impossible. Here, I report on the nesting season for 15 species of sympatric parrots inhabiting low- lands of the western Amazon Basin in south- eastern Peru. Land clearing and pressures on global for- est resources are constantly increasing. As for- ‘ Duke Univ., Dept, of Biology, Durham, NC 27708, USA; e-mail: djb4@duke.edu est areas shrink, conservationists must priori- tize their conservation efforts. Large, old trees and the cavities they contain are vital for the persistence of many cavity-nesting birds (Mawson and Long 1994, Poulsen 2002). However, cavity nesters usually do not use trees in proportion to their abundance, sug- gesting that some tree species are more im- portant than others to these birds (Martin and Eadie 1999, Monterrubio and Enkerlin 2004). In this study, I compiled nesting records for 1 5 species to determine which trees were most important to the nesting parrot community in southeastern Peru. METHODS Study area. — I studied parrot nesting in the Departamento de Madre de Dios in south- eastern Peru. The primary site was the Tam- bopata Research Center (13° 07' S, 69° 36' W; 250 m in elevation) on the border between the Tambopata National Reserve (275,000 ha) and Bahuaja-Sonene National Park (537,000 ha). The center is located in a small (<1 ha) clear- ing surrounded by a mix of mature floodplain forest, riparian successional forest, Mauritia flexuosa (Arecaceae) palm swamps, upland forest, and bamboo (Poster et al. 1994, Gris- com and Ashton 2003; DJB pers. obs.). The forest is classified as tropical moist forest (Holdridge 1967). The site is adjacent to a 500-m-long, 30-m-high riverbank clay lick, where up to 1,000 macaws and parrots gather daily, resulting in high parrot densities in the area (Brightsmith 2004a). Annual rainfall is 3,200 mm. The dry season extends from April to October, during which monthly rainfall av- erages 90-250 mm (Brightsmith 2004a). Ad- 296 Brightsmith • COMMUNITY-WIDE PARROT NESTING IN PERU 297 ditional nesting records come from Posada Amazonas Lodge in the Native Community of Infiemo (12° 48' S, 69° 18' W; 195 m in ele- vation; 2,800 mm annual rainfall; Pearson and Derr 1986, Brightsmith and Aramburu 2004) and Cocha Cashu Biological Station in Manu National Park (11° 54' S, 71° 18' W; 400 m in elevation; 2,000 mm annual rainfall; Terborgh 1983, Terborgh et al. 1984). These two sites are characterized by similar vegetation and dry seasons, and they are located 50 km north- northeast and 250 km northwest of Tambopata Research Center, respectively. Nesting records. — Nesting records consist- ed of two types: confirmed nests and birds at cavities. Confirmed nests were locations where I observed eggs or chicks. Observa- tions of birds at cavities, where contents were not checked, were included only when birds were observed repeatedly at the cavity and where behavioral cues suggested incubation or feeding of young. Single observations of birds at cavities were not included, as parrots may visit cavities when not breeding. Most of the nesting records were from July to August (1998) and November to April (1999 to 2003) in Tambopata and September to November (1993, 1995, 1996, and 1997) in Manu. I collected additional unpublished nest- ing records from researchers and guides with experience working in southeastern Peru. These other observers were stationed at Tam- bopata year-round. Data analysis. — I tested the relationship be- tween body size and the onset of breeding us- ing a rank correlation of body mass versus month of first breeding and a Utest (a = 0.05) of month of first breeding for large (>250 g) versus small (<250 g) psittacids (Gibbons 1985). Body-mass data are from Dunning (1993). RESULTS Red-and-green Macaw (Ara chlorop- tera). — Twelve nests of this species were monitored in Tambopata between 1993 and 2003. 1 determined laying date for nine nests: September (// = 1), November (// = 7), and December (/; = 1). Fledging was confirmed in January (/; = 1) and March (// = 5; Table 1 ). Most nests were in cavities of live, emergent Dipteryx (Fabaceae) trees (// = 7), although one nest was in a cavity of an unidentitied tree. One pair, consisting of a wild bird and a hand-raised bird released to the wild, nested in wooden nest boxes in 2 years (see Nycan- der et al. 1995 for a description of the nest boxes). Three nests were in floodplain forest (one <10 m from the river edge) and nine were in terra firme forest. Blue-and-yellow Macaw (Ara ararauna). — Seventy-two nests in at least 50 different cav- ities were recorded. Most cavities (47 of 50) were in dead Mauritia flexuosa palms. Be- cause it is difficult to climb dead palms, only 21 nest trees were climbed, and nest contents were checked infrequently. I estimated that egg laying occurred in November (n = 9), De- cember (n = 2), and January (n = 2). I con- firmed fledging in late February (n = 1), March (n = 4), and May (n — 1). Fifty of these nests were in a 3-ha section of naturally dying Mauritia flexuosa palm swamp, where dead palms occurred at a density of >200 per ha (A. Bravo and DJB unpubl. data). Sixteen nests were in a small (<0.25 ha) section of a swamp being managed to encourage nesting of Blue-and-yellow Macaws (Nycander et al. 1995). Three other nests were in tall, dead palms that rose above the surrounding vege- tation in an otherwise healthy palm swamp. Two nests were in floodplain forest in dead Iriartea palms <10 m from the river edge. One additional nest was in an unidentified dead, hollow tree in terra firme forest, 10 m from the edge of a cliff that overlooked the Tambopata River. The cavity was a deep, open-topped tube, similar in structure to a hol- low palm. Scarlet Macaw (Ara macao). — 1 studied 55 clutches at 26 different nest sites. 1 was certain of first-clutch initiation for 40 nests: late Oc- tober {n = I ), November (n = 32), and De- cember (n = 1). When the first clutch was lost or did not hatch, 35% (7 of 20) of the birds re-laid in the same nest. Second clutches were initiated in late December (// = 4) or early January (// = 3). Fledging took place in Feb- ruary (/; = 4), March (/; = 14), and April (// = 2). No eggs from second clutches hatched. Nests were found in natural cavities of live Dipteryx niicrantha {n - 6), live Hymenaea ohlongifolia (Fabaceae; n — 1), dead Iriartea palm (// = 1 ), and in artificial nest boxes made of wood or PVC’ pipe (/; = 18). No nests were found in dead Mauritia palms. Nests were in 298 THE WILSON BULLETIN • VoL 117, No. 3, September 2005 floodplain forest {n = 15), terra firme forest {n = 9), and Maiiritia palm swamp {n = 1); the habitat for one nest was not recorded. Chestnut-fronted Macaw (Ara severa). — Birds were observed attending seven cavities from November to February (Table 1). Ob- servers saw the nest contents in only one cav- ity; the nest was in a dead Mauritia flexuosa palm in the dying section of swamp discussed under Blue-and-yellow Macaw. It contained chicks in February. The other nests were in canopy branches of emergent Dipteryx mi- crantha trees {n = 6). All of the nest cavities were in trees that were relatively isolated from the surrounding vegetation in terra firme for- est {n = 4), floodplain forest {n = 2), or Mau- ritia palm swamp {n = 1). Red-bellied Macaw ( Orthopsittaca manila- ta).—\ observed birds attending 26 cavities in Tambopata from October to February. Four nests contained eggs or chicks, and I estimat- ed that eggs were laid in October {n = 2) and November {n = 2). All nests were in dead Mauritia fiexuosa palms; three nests were in the small (<0.25 ha) section of managed palm swamp, and 22 nests were in the 3-ha section of naturally dying Mauritia flexuosa swamp. Both habitats are described above in the sec- tion on Blue-and-yellow Macaw. White-eyed Parakeet (Aratinga leucopthal- mus). — In January, my assistants observed birds repeatedly attending a cavity in a dead palm in the center of a farm field. The pair was likely incubating or brooding because one bird entered the palm and refused to leave, even when observers knocked on the trunk of the palm. Dusky-headed Parakeet (Aratinga weddel- lii)_ — No chicks of this species were seen; all three records reported here are of birds at- tending cavities in dead trees or dead branches in live trees. The reports from Tambopata come from July, December, and January. These observations are congruent with a re- port from local residents who say that the spe- cies nests “year-round” (Sixto Duri pers. comm.). Nest cavities were in a dead tree of an unknown species (n — 1), a dead palm (n = 1), and a dead branch in a live Cecropia (Cecropiaceae) tree {n — 1). The nesting hab- itats included river edge (n = 1), small farm (n = 1), and a large natural gap in terra firme forest (n = 1). Scarlet-shouldered Parrotlet (Touit hue- tii). — This species is rare at the study sites. From August to September 1998, guides and guests at Tambopata Research Center repeat- edly saw two birds at a hole in an arboreal termite mound 3.5- to 4-m above the ground. The site was in terra firme forest with a mix of trees and bamboo {Guadua sarcocarpa). The birds were seen regularly attending the cavity over a period of a few weeks. Red-crowned Parakeet (Pyrrhura roseif- rons). — I located one nest of this species dur- ing October 1997 in Manu National Park. The nest was approximately 9 m high in a live tree in late-successional floodplain forest. One newly hatched chick and three eggs were seen on 4 October. A total of four birds attended this nest. They appeared to be adults, although two of the birds had less red on the head and may have been young from the previous year. During my last visit to the nest (4 November), I heard young birds begging inside the cavity. White-bellied Parrot (Pionites leucogas- ter). — Two live featherless chicks were found at the base of a suspected nesting tree in Oc- tober, indicating that eggs were laid in August; fledging would have occurred in November or early December. Birds were seen attending three additional cavities in Tambopata and Manu from September to February. The nest cavities were in canopy branches of live trees (two Dipteryx micrantha and one unknown species). Blue-headed Parrot (Pionus menstruus). — Five nests of this species were found, all from June to November (Table 1). Laying dates were calculated for two nests: late May or ear- ly June (n = 1) and September (n = 1). Chicks were seen in three nests. Fledging in November was confirmed at one nest. Nest sites were dead palms (n = 2) and PVC nest boxes (n = 2). All nests were near some sort of forest edge: river edge (n = 2), clearing edge (n = 1), and a steep drop-off in terra firme forest (n = 1). Habitat was not recorded for one nest. Yellow-crowned Parrot (Amazona ochro- cephala).—A member of this species was seen attending a dead palm from at least December to March in mature floodplain forest (A. del Campo pers. comm.). However, local people report that the chicks of this species fledge in October. Birds were also seen briefly at three TABLE 1. Parrot nesting phenology, by month and by season (dry or wet), in southeastern Peru (Departamento de Madre de Dios), 1993-1999. An “X” indicates peak breeding season (and chicks or eggs seen in the nest), “o” indicates periods when few birds breed, and “C” indicates that birds were observed regularly attending cavities (but no eggs or nestlings observed). Brightsmith • COMMUNITY-WIDE PARROT NESTING IN PERU 299 O o X X X X X U x: X X X u X X xxxxuxx uuu xxxxuxx uu XXX UXXX X XX X XX X XX X X X X X U X X U X X u o»/^iooooor^r^iooor^ir)OaN (N — — — ^ ~ c ^ ‘o 2 s 2 i: ^ 5 i i ~ CL X y. 1) 2 ^ 9 c £ §£ 2 ~ 9 ^ >1 *2 ^ ^ Oc 5b 2 C =Q 2 B III X. X u t S 2 •:= O £ 3 fc il II ■6 U X OQ -2 V — ^ 'k O JO, ■U t 2 ^ ^ ■i '9 p ^ r. t CL O ^ T3 2ri ? g r= o ■S ^ ^ c i» o O a: ;/2 i B ~ .£ &i> E E 5 c S i sf- C X i £ 300 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 other cavities in floodplain forest (Dipteryx micrantha, Erythrina sp. and an unknown spe- cies; A. del Campo and J. I. Rojas pers. comm.). Mealy Parrot (Amazona farinosa). — I ob- served two nests of this species. Eggs were laid in December {n = \) and January {n = 1). Both nests were in floodplain forest; one had two eggs, the other one egg and one chick. One was in a dead Iriartea palm, the other in a natural cavity in a live emergent Dipteryx micrantha tree. Relationship between body size and breed- ing season. — Most parrots and parakeets bred from June to November, whereas the macaws. Mealy Parrot, and White-eyed Parakeet nested from November to March (Table 1). Smaller parrot species initiated nesting significantly earlier in the season than larger parrots. This trend held for all 15 species (rank correlation: r = 0.70; Utest: t - 3.08, df = 13, P = 0.009; species listed in Table 1) and for the 11 spe- cies of which I observed chicks or eggs (rank correlation: r = 0.81; r-test: t = 5.25, df = 9, P < 0.001). I was unable to analyze body size versus nesting season using only phylogenet- ically independent contrasts because there is no complete phytogeny of New World parrots (Wolf et al. 1998, Tavares et al. 2004). How- ever, the available partial phytogenies show that there are at least two independent com- parisons in the data set: Red-bellied Macaw versus Blue-and-yellow Macaw and Blue- headed Parrot versus Mealy Parrot (Russello and Amato 2003, Ribas and Miyaki 2004). In both cases, the smaller species nests first. DISCUSSION During this study, nests or suspected nest sites were found for 13 of the 20 species of psittacids. This includes the first nest-site de- scription for Scarlet-shouldered Parrotlet and the second for White-bellied Parrot. For White-bellied Parrot, the only previous nest- ing record is of an incubating female in a tree cavity in eastern Brazil (Forshaw 1989). Of the seven psittacid species for which nests were not discovered, previous nest data are available for three. In Manu National Park, Cobalt-winged Parakeet {Brotogeris cyanop- tera) and Tui Parakeet {B. sanctithomae) both nest in termite mounds, lay eggs in August and September, and have chicks from mid- September to mid-November (Brightsmith 2000, 2004b). Amazonian Parrotlets {Nannop- sittaca dachilleae) in Tambopata attended a tree cavity in July and September (O’Neill et al. 1991). Of the remaining four species, none has been found nesting in the region: Dusky- billed Parrotlets (Forpus sclateri) were seen going in and out of a tree cavity in July in northern Peru (Forshaw 1989). No nests have been reported for Orange-cheeked Parrots (Pionopsitta barrabandi), but sightings of re- cently fledged young of this species at the Tambopata clay lick in December and Febru- ary suggest that the birds may lay eggs in Oc- tober or earlier (DJB pers. obs.). In Brazil, recently fledged Orange-cheeked Parrots also were seen during February and early March (Roth 1984, Forshaw 1989). No nesting in- formation is available for Black-capped Par- akeet (Pyrrhura rupicola) or Blue-headed Ma- caw (Propyrrhura couloni; Forshaw 1989, Collar 1997, Juniper and Parr 1998). The finding that smaller species bred earlier was unexpected, but it could be related to in- terspecific competition for nest sites or vari- ations in the availability of food resources (Roth 1984). Competition between species is potentially important because Chestnut-front- ed Macaws, Mealy Parrots, Yellow-crowned Parrots, toucans (Ramphastos spp.). Scarlet Macaws, and Red-and-green Macaws all over- lapped in their nest-site preferences (DJB un- publ. data). However, most of the smaller spe- cies that nested early in the season used sub- strates and cavities ignored by larger birds (e.g., termite mounds, thin dead palms, and small cavities; DJB pers. obs.) suggesting that something other than just competition drives the nesting phenology patterns I observed. Seasonal differences in nesting may be due to differences in diet and food availability. The smaller parrots that nest in the dry season usually eat more nectar, flowers, and small seeds than larger species (Roth 1984, Desenne 1994; see also Terborgh 1983 for similar pat- terns exhibited by primates). Flowering in many tropical communities peaks in the dry season (van Schaik et al. 1993, Fenner 1998) and many wind-dispersed plants fruit in the dry season, when deciduous canopy trees lose their leaves and higher wind velocities pro- duce ideal dispersal conditions (Fenner 1998). Because flowers and small wind-dispersed Brightsmith • COMMUNITY- WIDE PARROT NESTING IN PERU 301 seeds are relatively low-quality foods that re- quire a large energy investment to harvest, smaller-bodied parrots should have an advan- tage when exploiting these resources (Ter- borgh 1983). As a result, larger species should incur comparatively greater food shortages in the dry season than smaller species, explain- ing the wet season breeding of larger parrots found in Tambopata. Notably, the earliest- breeding species was the mid-sized Blue- headed Parrot; members of its genus (Pionus) are known to eat many flowers (Galetti 1993). Nest searching was not conducted with equal intensity in all months. Although sam- pling efforts were more intense later in the season, most of my nesting records for small species come from the early part of the sea- son. I have had crews observing macaws con- tinuously from November 2000 to May 2004, and they did not witness large macaws nesting earlier in the season. Conducting more nest searches from May through August would likely reveal additional small species breed- ing, corroborating the trend we found. Few studies have addressed parrot nesting seasonality at the community level. Roth (1984) hypothesized that congeners staggered breeding to avoid competition for food. His data support the pattern for Aratinga and Amazona, where smaller species did nest ear- lier, but Pyrrhura and Ara overlapped exten- sively. My data, however, do not support tem- poral spacing by congeners, and my analysis of Roth’s (1984) data shows that smaller spe- cies tended to nest earlier, but not significantly so (rank correlation: r = 0.34; r-test: t — 0.94, df = \2, P = 0.37). Future studies should in- vestigate the interplay of competition for nest sites, diet, and phenological cycles in deter- mining the seasonality of parrot breeding. My study highlighted two types of sites that are very important to nesting parrots: emer- I gent Dipteryx micrantha trees and dead palms. Six species were recorded using large, emer- gent Dipteryx micrantha trees, and 75 and 88% of the natural nests used by Scarlet and Red-and-green macaws, respectively, were in these trees (see also Nycander ct al. 1995). Large emergents of this species often con- tained dozens of cavities, and individual trees often had multiple pairs of macaws nesting in them simultaneously (A. Hepworth and D.IB unpubl. data). Because Dipteryx micrantha can live for over 1,000 years, cavities in these trees may remain useable by macaws for de- cades or centuries (Chambers et al. 1998; but see Fichtler et al. 2003). As a result, hundreds of macaw chicks may be produced from a sin- gle tree during its lifetime. The fruits of Dip- teryx species are also a keystone resource for a variety of tropical frugivores and granivores, including Great Green Macaws {Ara ambigua; G. Powell unpubl. data), bats {Artibeus spp.; Romo 1997), squirrels {Sciurus spp.), and agoutis (Dasyprocta spp.; Emmons 1984, For- get 1993) Unfortunately, Dipteryx trees are increas- ingly logged throughout their range. Dipteryx wood is in high demand for hardwood flooring (Toledo and Rincon 1999, Wood Flooring In- ternational 2003) and, in Peru, people use the wood to make charcoal. Landowners sell trees >1 m in diameter for as little as US $30 (A. Hepworth unpubl. data). The recent increased harvest of Dipteryx panamensis in Costa Rica is the most probable cause for the precipitous decline of Great Green Macaws in that coun- try (Bjork and Powell 1995, Chassot and Monge 2002). Management schemes involv- ing planting of Dipteryx trees are underway in Costa Rica. This can produce fruiting trees, but large, gnarled adult trees riddled with use- able cavities are practically irreplaceable, as they take hundreds of years to grow. Palms have long been recognized as vital to the survival of tropical frugivores and gran- ivores (Emmons 1984, Henderson 1995). In fact, several New World parrots are thought to be almost completely dependent on palms for food, nesting sites, or both (Yamashita 1987, Forshaw 1989, Yamashita and Valle 1993, Ya- mashita and Barros 1997, Salamaii et al. 2001). Eight parrot species were observed nesting in palms during this study, and reports from the literature show that two additional species also use palms (Red-and-green Macaw and Dusky-headed Parakeet; Forshaw 1989, Nycander et al. 1995). In sum, half of the par- rot species in this community nest in palms and palms are important not (uily for special- ists, but for many generalists as well. Manritia flexuosa palms arc particularly valuable resources for parrots (Forshaw 1989, Bonadie and Bacon 2()()0). In Peru, at least seven species of psittacids nest in Manritia palms (Gon/alez 2003; this study), and studies 302 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 on Trinidad show that palm swamps are key to the maintenance of parrot populations (Bonadie and Bacon 2000). Dying palm swamps are particularly valuable because par- rots nest at high densities in these sites. Gon- zalez (2003) reported aggregations of macaws in dying sections of Mauritia palm swamps in northern Peru, similar to what I report for Tambopata. Nesting densities there (0.075 nests/ha; range = 0.038-0.128/ha) were lOOX smaller than those in Tambopata (>29 nests in 3 ha or >9. 7/ha). In northern Peru, the par- rots spread out over larger areas of dying swamp, and parrot collectors regularly re- duced the nest densities (Gonzalez 2003). In Tambopata, the birds were concentrated in a small, protected area near a large clay lick (Brightsmith 2004a). Breeding near the clay lick may be particularly important because adult parrots feed their nestlings clay and con- centrate their use of the lick during the breed- ing season (DJB unpubl. data). Areas of palm swamp can die synchro- nously in response to flooding and other events that result in depositions of large sed- iment loads (Kahn 1988, Gonzalez 2003; DJB pers. obs.). How long the dead palms remain useable for nesting parrots under natural con- ditions is unknown. However, Mauritia palms that died when their tops were cut off re- mained upright an average of 4 to 5 years be- fore they fell (Nycander et al. 1995; DJB un- publ. data). The short, useful lifetime of in- dividual dead palms suggests that dying palm swamps slowly shift in the landscape as new areas die and old areas become unusable. Like most parrots, those that nest in these dead swamps probably “wander,” tracking shifts in food resources and nest-site availability (Col- lar 1997, Renton 2002). As a result, dying palm swamps probably serve as breeding “source” areas in landscape-level source-sink dynamics and play a disproportionately large role in maintaining regional populations of these long-lived and highly mobile psittacids. Palms are valuable to local people, and doz- ens of species are used for food, fiber, con- struction materials, fuel, and medicines (Vas- quez and Gentry 1989, Henderson 1995). Overexploitation is common and its potential impact on the ecosystem is great (Johnson 1986, Bonadie and Bacon 2000). Mauritia flexuosa swamps cover at least 2 million ha in the Iquitos region alone, but they are threat- ened because local people commonly cut en- tire trees to harvest weevil larvae (Dry- ophthoridae: Rhynchophorus palmarum) and fruit (Peters et al. 1989, Vasquez and Gentry 1989). However, many psittacids, game spe- cies, and large-bodied seed dispersers that move between the swamps and the surround- ing landscape also depend on these fruits (Bodmer 1990, Bonadie and Bacon 2000). As a result, the loss of these swamps would have great impacts on the ecosystem. The two primary nesting resources exploit- ed by parrots in southeastern Peru are struc- turally different. In fact, they represent op- posite ends of the tree-cavity spectrum. The dead palms are hollow tubes with open tops that allow rain to enter. They are thin-walled, poorly insulated, and flimsy; also, they last for only a few years before collapsing. In com- parison, Dipteryx cavities have thick walls of hard wood, full roofs that provide protection from the rain, and are usually in live sections of solid trees that live for centuries (Chambers et al. 1998; DJB pers. obs.). It is surprising that two such different substrates attracted the majority of nesting parrots. The only charac- teristic they shared was their isolation from the surrounding vegetation. Dead-palm nest sites were almost always in the open: along river edges, in dead swamps, above the sur- rounding canopy, or in forest openings. The Dipteryx cavities were far from heavy epi- phyte and vine cover, distant from adjacent trees, and high above the ground. This sug- gests that protection from non-volant preda- tors has a great influence on parrot nest-site selection (Massello and Quillfeldt 2002, Brightsmith 2005a, 2005b). The availability of suitable nest sites limits the reproductive output of many cavity-nest- ing species, especially in anthropogenically modified landscapes (Newton 1994). This study suggests that Dipteryx micrantha and Mauritia flexuosa are keystone tree species for parrots nesting in southeastern Peru. Clearing for agriculture, targeted destruction of parrot nests by collectors, and selective felling of key tree species will reduce the density of suitable nest cavities. Future studies should continue to identify key nesting resources for parrots and other cavity-nesting species so Brightsmith • COMMUNITY- WIDE PARROT NESTING IN PERU 303 that these important habitat features can be I conserved in tropical landscapes. I ACKNOWLEDGMENTS I thank the following people for contributing nest records, library work, and support in the field: G. Ar- rospide, D. Brooks, A. del Campo, C. Carrasco, D. Combs, Sixto Duri, Silverio Duri, J. Gonzalez, A. Hep- worth, H. Lavado, R. Masias, R. von May, A. Mishaja, J. Moscoso, E. Nycander, R. Olivera, J. Pesha, R. Pi- ana, J. I. Rojas, A. Valdez, and L. Zapater. Thanks also to my assistants in Manu and Tambopata, the staffs of Cocha Cashu Biological Station and Tambopata Re- i search Center, and the Native Community of Infierno for permission to work on their lands. Thanks also to the offices of the Institute Nacional de Recursos Na- turales (INRENA) in Lima, Cuzco, and Puerto Mal- donado. Earlier drafts of this work were improved by * the comments of E. Villalobos, J. Wiley, L. Pautrat, and two anonymous reviewers. This work was funded by the National Science Foundation (grant number DEB- ' 95-20800), Conservation Food and Health Foundation, EarthWatch Institute, Rainforest Expeditions (www. perunature.com.pe), Raleigh-Durham Cage Bird Socie- ty, Amigos de las Aves USA, and W. and L. Smith. LITERATURE CITED Bennett, P. M. and I. P. F. Owens. 1997. Variation in extinction risk among birds: chance or evolution- ary predisposition? Proceedings of the Royal So- ciety of London, Series B 264:401-408. Bjork, R. and G. V. N. Powell. 1995. Buffon’s Ma- caw: some observations on the Costa Rican pop- ulation, its lowland forest habitat and conserva- tion. Pages 387-392 in The large macaws: their care, breeding and conservation (J. Abramson, B. L. Spear, and J. B. Thomsen, Eds.). Raintree Pub- lications, Ft. Bragg, California. Bodmer, R. E. 1990. Responses of ungulates to sea- sonal inundations in the Amazon floodplain. Jour- nal of Tropical Ecology 6:191-201. Bonadie, W. a. and P. R. Bacon. 2000. Year-round utilization of fragmented palm swamp forest by j Red-bellied Macaws (Ara mcmilata) and Orange- ' winged Parrots (Amazona arnazonica) in the Na- riva Swamp (Trinidad). Biological Con.servation 95:1-5. I Brightsmith, D. J. 2000. Use of arboreal termitaria by nesting birds in the Peruvian Amazon. Condor 102:529-538. I Brightsmith, D. J. 2004a. Effects of weather on avian i geophagy in Tambopata, Peru. Wilson Bulletin 1 16:134-145. Brightsmith, D. J. 2(M)4b. Nest sites of termitarium nesting birds in SE Peru. Neotropical Ornithology 15:319-330. Brightsmith, D. J. 2(K)5a. Competition, predation and nest niche shifts among tropical cavity nesters: phylogeny and natural history evolution of parrots (Psittaciformes) and trogons (Trogoniformes). Journal of Avian Biology 36:64-73. Brightsmith, D. J. 2005b. Competition, predation and nest niche shifts among tropical cavity nesters: ecological evidence. Journal of Avian Biology 36: 74-83. Brightsmith, D. J. and R. Aramburu. 2004. Avian geophagy and soil characteristics in southeastern Peru. Biotropica 36:534-543. Chambers, J. Q., N. Higuchi, and J. P. Schimel. 1998. Ancient trees in Amazonia. Nature 391:135-136. Chassot, O. and G. Monge. 2002. Great Green Ma- caw: flagship species of Costa Rica. PsittaScene 53:6-7. Cherrie, G. K. 1916. a contribution to the ornithology of the Orinoco region. Museum of Brooklyn In- stitute of Arts and Sciences Bulletin 2:133-374. Collar, N. J. 1997. Family Psittacidae. Pages 280- 479 in Handbook of the birds of the world, vol. 4: sandgrouse to cuckoos (J. del Hoyo, A. Elliott, and J. Sargatal, Eds.). Lynx Edicions, Barcelona, Spain. Desenne, P. 1994. Estudio preliminar de la dieta de 15 especies de psitacidos en un bosque siempreverde, Cuenca del Rio Tawadu, Reserva Forestal El Cau- ra, Edo. Bolivar. Pages 25-42 in Biologia y con- servacion de los psitacidos de Venezuela (G. Mo- rales, I. Novo, D. Bigio, A. Luy, and F. Rojas- Suarez, Eds.). Graficas Giavimar, Caracas, Vene- zuela. Dunning, J. B. 1993. CRC handbook of avian body masses. CRC Press, London, United Kingdom. Emmons, L. H. 1984. Geographic variation in densities and diversities of non-flying mammals in Ama- zonia. Biotropica 16:210-222. Fenner, M. 1998. The phenology of growth and re- production in plants. Perspectives in Plant Ecol- ogy, Evolution and Systematics 1:78-91. Fichtler, E., D. a. Clark, and M. Worbes. 2003. Age and long-term growth of trees in an old- growth tropical rain forest, based on analyses of tree rings and '“*C. Biotropica 35:306-317. Forget, P. M. 1993. Post-dispersal predation and scat- terhoarding of l^ipteryx pamunensis (Papiliona- ceae) seeds by rodents in Panama. Oecologia 94: 255-261. Forshaw, j. M. 1989. Parrots of the world, 3rd ed. Landsdowne F^ditions, Melbourne, Australia. Fo.ster, R. B., T. a. Parker, A. H. Gentry, L. H. Emmons, A. CiiirciioN, T. SriiuLENBiiRG, L. Ro- DRiGiiEZ f;t al. 1994. The Tambopata-C'andamo Reserved Zone of southeastern Peru: a biological assessment. RAP Bulletin, no. 6. Conservation In- ternational, Washington, D.C. www. conservation. org/xp/CABS/publications/cabs_pubLrcsearch/rap_ buIlctins/tcrrestriaLrap-bullctins/tcrrrapbulletins. xml (accessed May 2004). CiALi-rri, M. 1993. Diet of the Scaly-hcaticd Parrot {/*ionns ma.xitniUani) in a scmideciduous forest in southeastern Brazil. Biotropica 25:419-425. Gibbons, J. D. 1985. Nonparametric methods forquan- 304 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 titative analysis. American Sciences, Columbus, Ohio. Gonzalez, J. A. 2003. Harvesting, local trade, and conservation of parrots in the northeastern Peru- vian Amazon. Biological Conservation 114:437- 446. Griscom, B. W. and P. M. S. Ashton. 2003. Bamboo control of forest succession: Guadua sarcocarpa in southeastern Peru. Forest Ecology and Man- agement 175:445-454. Havershmidt, H. 1968. Birds of Surinam. Oliver and Boyd, London, United Kingdom. Henderson, A. 1995. The palms of the Amazon. Ox- ford University Press, New York. Herkert, J. R., D. L. Reinking, D. A. Wiedenfeld, M. Winter, J. L. Zimmerman, W. E. Jensen, E. J. Finck et al. 2003. Effects of prairie fragmenta- tion on the nest success of breeding birds in the midcontinental United States. Conservation Biol- ogy 17:587-594. Holdridge, L. R. 1967. Life zone ecology, revised ed. Tropical Science Center, San Jose, Costa Rica. Huber, W. 1933. Birds collected in northeastern Nic- aragua in 1922. Proceedings of the Academy of Natural Sciences Philadelphia 84:205-249. Johnson, D. V. 1988. Worldwide endangerment of use- ful palms. Pages 268-273 in The palm-tree of life: biology, utilization, and conservation (M. J. Balick, Ed.). New York Botanical Garden, Bronx, New York. Juniper, T. and M. Parr. 1998. Parrots: a guide to parrots of the world. Yale University Press, New Haven, Connecticut. Kahn, E 1988. Ecology of economically important palms in the Peruvian Amazon. Pages 42-49 in The palm-tree of life: biology, utilization, and conservation (M. J. Balick, Ed.). New York Bo- tanical Garden, Bronx, New York. Martin, K. and J. M. Eadie. 1999. Nest webs: a com- munity-wide approach to the management and conservation of cavity-nesting forest birds. Forest Ecology and Management 115:243-257. Masello, j. E and P. Quillfeldt. 2002. Chick growth and breeding success of the Burrowing Parrot. Condor 104:574-586. Mawson, P. R. and j. L. Long. 1994. Size and age parameter of nest trees used by four species of parrot and one species of cockatoo in southwest Australia. Emu 94:149-155. Montambault, j. R. 2002. Informes de las evalua- ciones biologicas Pampas del Heath, Peru; Alto Madidi, Bolivia; y Pando, Bolivia. RAP Bulletin 24. Conservation International, Washington, D.C. www.biodiversityscience.org/xp/CABS/ publications/cabs_publ_research/rap_bulletins/ terrestriaLrap-bulletins/terrrapbulletins.xml (ac- cessed May 2004). Monterrubio, T. and E. C. Enkerlin. 2004. Present use and characteristics of Thick-billed Parrot nest sites in northwestern Mexico. Journal of Field Or- nithology 75:96-103. Newton, I. 1994. Experiments on the limitation of hire breeding densities: a review. Ibis 136:397-411. Nycander, E., D. H. Blanco, K. M. Holle, A. del Campo, C. a. Munn, j. I. Moscoso, and D. G. Ricalde. 1995. Manu and Tambopata: nesting success and techniques for increasing reproduc- tion in wild macaws in southeastern Peru. Pages 423-443 in The large macaws: their care, breed- ing and conservation (J. Abramson, B. L. Spear, and J. B. Thomsen, Eds.). Raintree Publications, Ft. Bragg, California. O’Neill, J. R, C. A. Munn, and I. Franke. \99\.Nan- nopsittaca dachilleae, a new species of parrotlet from eastern Peru. Auk 108:225-229. Pearson, D. L. and J. A. Derr. 1986. Seasonal pat- terns of lowland forest floor arthropod abundance in southeastern Peru. Biotropica 18:244-256. Peters, C. M., M. J. Balick, E Kahn, and A. B. An- derson. 1989. Oligarchic forests of economic plants in Amazonia: utilization and conservation of an important tropical resource. Conservation Biology 3:341-349. PouLSEN, B. O. 2002. Avian richness and abundance in temperate Danish forests: tree variables impor- tant to birds and their conservation. Biodiversity and Conservation 11:1551-1566. Ratcliffe, D. a. 1967. Decrease in eggshell weight in certain birds of prey. Nature 215:208-210. Renton, K. 2002. Seasonal variation in occurrence of macaws along a rainforest river. Journal of Field Ornithology 73:15-19. Ribas, C. C. and C. Y. Miyaki. 2004. Molecular sys- tematics in Aratinga parakeets: species limits and historical biogeography in the ' solstitialis" group, and the systematic position of Nandayus nenday. Molecular Phylogenetics and Evolution 30:663- 675. Romo, M. 1997. Seasonal variation in fruit consump- tion and seed dispersal by canopy bats {Artibeus spp.) in a lowland forest in Peru. Vida Silvestre Neotropical 5:110-119. Roth, P. 1984. Reparti^ao do habitat entre psitacideos simpatricos no sul da Amazonia. Acta Amazonica 14:175-221. Russello, M. a. and G. Amato. 2003. A molecular phylogeny of Amazona: implication for Neotrop- ical parrot biogeography, taxonomy and conser- vation. Molecular Phylogenetics and Evolution 30:421-437. Salaman, R, a. Cortes, P. Florez, J. C. Luna, O. Nieto, J. E Castano, and G. Suarez. 2001. Proy- ecto Ognorhynchus progress report IV. www. ognorhynchus.com/report4.htm (accessed August 2003). Tavares, E. S., C. Yamashita, and C. Y. Miyaki. 2004. Phylogenetic relationships among some Neotropical parrot genera (Psittacidae) based on mitochondrial sequences. Auk 121:230-242. Terborgh, j. 1983. Five New World primates: a study in comparative ecology. Princeton University Press, Princeton, New Jersey. Brightsmith • COMMUNITY-WIDE PARROT NESTING IN PERU 305 ERBORGH, J., J. W. Fitzpatrick, and L. H. Emmons. 1984. Annotated checklist of birds and mammals species of Cocha Cashu Biological Station, Manu National Park, Peru. Fieldiana Zoology 21:1-29. ■OLEDO, E. AND C. RiNCON. 1999. Utilizacion indus- trial de nuevas especies forestales en el Peru. Ca- mara Nacional Forestal, Lima, Peru. an Schaik, C. R, j. Terborgh, and S. J. Wright. 1993. The phenology of tropical forests: adaptive significance and consequences for primary con- sumers. Annual Review of Ecology and System- atics 24:353—377. Vasquez, R. and a. H. Gentry. 1989. Use and misuse of forest-harvested fruits in the Iquitos area. Con- servation Biology 3:350—361. Wolf, C. M., T. Garland, and B. Griffith. 1998. Predictors of avian and mammalian translocation success: reanalysis with phylogenetically indepen- dent contrasts. Biological Conservation 86:243- 255. Wood Flooring International. 2003. Species hard- ness. www.wflooring.com/Technical_Info/Species_ Tech_ Info /species- hardness, htm (accessed May 2004). Yamashita, C. 1987. Field observations and com- ments on the Indigo Macaw {Anodorhynchus lean), a highly endangered species from north- eastern Brazil. Wilson Bulletin 99:280-282. Yamashita, C. and Y. M. de Barros. 1997. The Blue- throated Macaw Ara glaucogularis: characteriza- tion of its distinctive habitats in savannahs of the Beni, Bolivia. Ararajuba 5:141-150. Yamashita, C. and M. de P. Valle. 1993. On the linkage between Anodorhynchus macaws and palm nuts, and the extinction of the Glaucous Ma- caw. Bulletin of the British Ornithological Club 113:53-59. Wilson Bulletin 1 17(3);306-312, 2005 GROUP-SIZE EFFECTS AND PARENTAL INVESTMENT STRATEGIES DURING INCUBATION IN JOINT-NESTING TAIWAN YUHINAS (YUHINA BRUNNEICEPS) HSIAO-WEI YUAN,' SHENG-FENG SHEN,« KAI-YIN LIN,^ AND PEI-FEN LEE^'* ABSTRACT. We investigated the effect of group size on incubation effort in Taiwan Yuhinas (Yuhina hrunneiceps) at the Highlands Experimental Farm of National Taiwan University at Meifeng, Nantou County, central Taiwan, during 2000 and 2001. The Taiwan Yuhina is a joint-nesting, cooperatively breeding species endemic to Taiwan. We compared differences in parental investment among individuals of different sexes and status, explored the effect of group size on group incubation effort, and investigated whether individuals show compensatory reductions in care with respect to the number of females laying. Constancy of incubation increased as group size increased. Alpha females exhibited a significantly greater incubation effort than other individuals, but effort was similar among other group members. Both alpha males and females decreased their relative and absolute incubation effort as group size increased (i.e., there was a compensatory reduction in parental effort). However, beta pairs maintained a consistent but low incubation effort when either gamma pairs or an extra individual joined the group. Our study also demonstrated a new potential group-size benefit for cooperatively breeding birds — an increase in the constancy of incubation. Received 6 July 2004, accepted 31 March 2005. The effect of group size on individual fit- ness is one of the most important aspects in understanding the evolution of sociality (Brown 1983, Kokko et al. 2001). In cooper- atively breeding animals, individuals share pa- rental effort with other group members. The optimal parental investment of each individual depends largely on the sum of other group members’ parental efforts; that is, parental ef- fort is affected by group size. Much attention has been paid to how individual provisioning effort is affected by group size in helper-at- the-nest systems (Hatchwell 1999). Two types of provisioning effort are recognized: additive and compensatory (Hatchwell 1999). Additive provisioning occurs when parents maintain the same provisioning effort, regardless of the number of helpers; thus, the total provisioning rate increases as group size increases (Emlen and Wrege 1991). On the other hand, com- pensatory provisioning occurs when total ef- fort is comparatively constant and breeding individuals reduce their parental effort in re- sponse to increasing levels of effort by helpers (Brown et al. 1978). In a detailed comparative ' School of Forestry and Resource Conservation, National Taiwan Univ., Taipei 106, Taiwan. 2 Inst, of Ecology and Evolutionary Biology and Dept, of Life Science, National Taiwan Univ., Taipei 106, Taiwan. 3 Current address; Dept, of Neurobiology and Be- havior, Cornell Univ., Ithaca, NY 14853, USA. Corresponding author; e-mail: leepf@ntu.edu. tw Study, Hatchwell (1999) showed that (1) care tends to be additive when the probability of nestling starvation is high and (2) parents are more likely to show compensatory reductions in care when the chance of starvation is low. In addition, Hatchwell hypothesized that male breeders may tend to exhibit compensatory re- ductions due to the uncertainty of parentage. Little research has been conducted on the parental investment strategies of cooperative breeders during incubation (Vehrencamp 1977, Heinsohn and Cockbum 1994, Kom- deur 1994). Mammalian studies have demon- strated that variation in the relative contribu- tions of individual helpers to different coop- erative activities, such as nursing and guard- ing, is important (Clutton-Brock et al. 2003). Incubation is certainly an important compo- nent of reproductive success in most bird spe- cies and has been considered a costly behavior (Visser and Lessells 2001, Reid et al. 2002b). Incubation among cooperative breeders is es- pecially interesting to study because — in con- trast to the cues received from nestlings — par- ents and helpers receive no cues from the eggs as to how much care is being given by other group members. We investigated the effect of group size on incubation effort in a joint-nesting passerine, the Taiwan Yuhina {Yuhina hrunneiceps, here- after referred to as yuhina). Our study focused on whether additive and compensatory in- vestment strategies, developed in the context 306 Yuan et al. • PARENTAL INVESTMENT IN TAIWAN YUHINAS 307 I of nestling provisioning, are also applicable to incubation effort. We explicitly considered two issues. First, we explored the effect of group size on total incubation effort. Second, we investigated whether individuals exhibited compensatory reductions in care by compar- ing the differences in parental investment strategies between individuals of different sex and status with respect to the number of breeding pairs. METHODS Study population. — The Taiwan Yuhina, a Timaliine babbler, is endemic to Taiwan (Cle- ments 2000). Since Yamashina (1938) first de- scribed the species’ communal nesting behav- iors, there has been no detailed study of this species. We have been studying a color-band- ed population of Taiwan Yuhinas since 1995 : at the Highlands Experimental Farm of Na- 1 tional Taiwan University at Meifeng, Nantou j County, central Taiwan (24° 05' N, 121° 10' I E; 2,150 m in elevation). During June 2000, average daytime and nighttime temperature was 25.2° C and 12.2° C, respectively. The study site has been described in detail else- where (Yuan et al. 2004). The yuhinas’ breed- ing season lasts 6 months, usually from March or April to August or September. Yuhinas build open-cup nests 1-15 m above ground in various substrates along forest edges. Most ju- i veniles (78%) disappear from the study area I after their hatch year; therefore, most (92%) new group members are not closely related. ! Breeding groups comprise one to three mo- ■ nogamous pairs (mode = 2 pairs) and some- times one extra male. Within each group, there ) is a linear hierarchy of socially monogamous I pairs with all pairs contributing some eggs. ' The combined clutch size increases as group size increases. However, the average number ' of eggs laid by each female decreases with i increasing group size (Yuan et al. 2004). Ac- cording to data from microsatellitc genetic i markers, mean reproductive skew (the parti- I tioning of reproduction among same-sex in- dividuals within social groups) is low (Yuan et al. 2004), and all breeding pairs contribute to nest building, incubation, and provisioning (H-WY unpubl. data). Alpha and beta individuals were identified by observing chasing and displacement be- havior among group members. Particular in- dividuals— both males and females — consis- tently chased and displaced same-sex mem- bers of their group. In larger groups, gamma individuals were chased by both alpha and beta individuals (see Yuan et al. 2004 for fur- ther details). Sex of all banded individuals (97% of the birds that we observed were col- or-banded) was assigned tentatively in the field based on observations of singing and copulation; later, gender was verified against sex-specific genetic markers via PCR (Fri- dolfsson and Ellegren 1999). Incubation. — We observed diurnal incuba- tion bouts from blinds 10-15 m from nests by using 15 X 40 image-stabilized binoculars. We recorded incubation effort at 21 nests of 1 1 breeding groups from June to August in 2000 and from March to August in 2001. The mean total observation time for each nest was 683 min (range = 252-1,096 min) and the mean continuous observation period was 414 min (range = 235-839 min). We successfully identified most individuals (89 ± 2.4%) in- volved in incubation at each nest. We ob- served incubation effort during the first 10 days of the incubation period (mean = 5.69 days ± 2.33 SD of observation per nest). Data analysis. — Constancy of incubation (i.e., the time that the eggs are in contact with any adult bird, expressed as the percentage of time eggs were incubated; Deeming 2002) dif- fered from nest to nest. A mixed model was originally used to deal with the problem of repeated measurement of different nest at- tempts within the same group. However, be- cause “group” (indicating different breeding group) had a negative component of variance, the mixed model was equivalent to GEM in this case (Schall 1991); therefore, GEM was used. Individual incubation effort was assessed in two ways; as relative incubation elfort (RIE) and as absolute incubation effort (AIEL). We calculated RIE by dividing each individuaTs incubation time by the group's total incubation time. We calculated AIE by dividing each in- dividual’s incubation time by total observation time (group’s total incubation lime + time during which nest was unattcndetl). We ana- lyzed individual incubation efl'ort (R1I{ and A1E4 by using the residual maximum likeli- hood (RPA1E) algorithm (mixed model) in SPSS 12.0 (SPSS. Inc. 2003) with normal er- Constancy of incubation (%) 308 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 Number of breeding pairs FIG. 1. Relationship between group size (number of breeding pairs) and incubation constancy for Taiwan Yuhinas in Nantou County, central Taiwan, 2000- 2001. Larger groups had significantly greater constan- cy of incubation than smaller groups. Error bars are ± SE. Sample size (number of nests) shown above bars. ror structures, in which both fixed and random terms can be fitted. Random terms control for the use of repeated measurements within a given group, nest (different nest attempts of each group), pair status (i.e., alpha, beta, and gamma birds, and extra males without mates in odd numbered groups), and sex. However, the only interaction term we used in the anal- ysis of alpha’s and beta’s incubation effort was “group” X “status” because all other factors had a negative component of variance (Schall 1991). The incubation effort of gamma pairs and extra males were excluded in all analyses due to their small sample sizes. However, gamma pairs affected group size and “extra” was used as a categorical variable to see if an extra male would affect other individuals’ in- cubation effort. Least significant difference (LSD) post hoc pairwise comparisons were used to compare individual effort for each sex and social rank. Given that sex and status had a significant interaction effect, we also use a mixed model REML to analyze factors affecting alpha pairs’ and beta pairs’ incubation efforts sep- arately. However, group fitted as the random term had a negative component of variance, so the mixed model is equivalent to GLM in this analysis. We report means ± SE through- TABLE 1. Results from a mixed model (residual maximum likelihood, REML) of relative incubation ef- fort (RIE) for breeders of alpha and beta pairs of Tai- wan Yuhinas in Nantou County, central Taiwan, 2000- 2001. Effect df F p Intercept 1, 8 15.59 0.004 Sex 1, 34 4.21 0.048 Status 1, 8 5.94 0.040 Group size 1, 7 1.89 0.21 Sex X status 1, 34 4.68 0.038 Status X group size“ 1, 8 2.99 0.12 Sex X group size 1, 34 1.53 0.23 Extra X group size 1, 6 0.09 0.77 ® Status X group size was included in the model as a random factor. Estimate of variance = 33.90 ± 46.37 (SE). out this paper. All tests are two-tailed, with a significance criterion of P < 0.05. RESULTS Factors influeticing constancy of incubation and individual contributions to incubation. — Constancy of incubation (% of time eggs were incubated) was significantly influenced by group size (GLM, F121 — 7.32, P = 0.014; Eig. 1), but not by month of breeding (F^ ^i ^ 0.20, P = 0.25), number of previous nesting attempts = 0-297, P = 0.59), or days after first incubation (Pi,2i ~ 0.475, P = 0.50). Individual RIE differed between sexes (group sizes combined, alpha and beta birds com- bined: 23.13 ± 2.38% for males, 35.64 ± 3.64% for females) and status class (group sizes combined, males and females combined: 36.34 ± 2.91% for alpha birds, 17.63 ± 2.33% for beta birds), and there was a signif- icant sex X status interaction (Table 1). AIE did not differ between the sexes (P = 0.18) or between birds of different status (P = 0.11), but there was a significant interaction between sex and status (Table 2). Pairwise comparisons show that alpha females contrib- uted more than all other birds in RIE (group sizes combined): alpha female (45.73 ± 3.93%) versus alpha male (26.94 ± 3.23%, P < 0.001); alpha female versus beta female (18.28 ± 3.87%, P < 0.001). Alpha females also contributed more than all other birds in AIE (group sizes combined): alpha female (34.16 ± 2.54%) versus alpha male (20.22 ± 2.44%, P < 0.001); alpha female versus beta female (15.92 ± 3.35%, P = 0.001). There Yuan et al. • PARENTAL INVESTMENT IN TAIWAN YUHINAS 309 TABLE 2. Results from a mixed model (residual maximum likelihood, REML) of absolute incubation effort (AIE) for breeders of alpha and beta pairs of Taiwan Yuhinas in Nantou County, central Taiwan, 2000-2001. Effect df F p Intercept 1, 6 10.87 0.018 Sex 1, 28 1.91 0.18 Status 1, 5 3.74 0.11 Group size 1, 5 0.20 0.67 Sex X status 1, 28 4.37 0.046 Status X group size"* 1, 5 1.63 0.26 Sex X group size 1, 28 0.40 0.53 Extra X group size 1, 3 0.48 0.54 Status X group size was included in the model as a random factor. Estimate of variance = 17.02 ± 30.77 (SE). FIG. 2. Mean (± ,SE) relative incubation effort (RIE) of (A) females and (B) males in different group sizes (number of breeding pairs) of Taiwan Yuhinas in Nantou County, central Taiwan. 2(KK)-2(K)1. Sample size (number of nests) shown above bars. FIG. 3. Mean (± SE) absolute incubation effort (AIE) of (A) females and (B) males in different group sizes (number of breeding pairs) of Taiwan Yuhinas in Nantou County, central Taiwan, 2()()()-20() 1 . Sample size (number of nests) shown above bars. were no significant differences among other individuals in either RIE or AIE (Figs. 2 and 3). Incubation effort betw een sexes and ^roup sizes of different status. — Because there was a strong sex X status interaction, we further an- alyzed alpha anti beta pairs separately. RIE of alpha fctnalcs was greater than that of alpha males (CiEM, /*', ,7 = 6.43, P = 0.016: Fig. 2) and RIE; of the three group sizes differetl (males anti females ct>mhinetl, alpha birtls t)nly): 46.23 ± 2. .38% (tuie breeding pair), 32.33 ± 3.97% (twt) breetling pairs), and 22.32 ± 4.32% (three breetling pairs) (/'i ^7 = 16.24, P < 0.001; Fig. 2). Fhere was no in- 310 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 teraction between sex and group size (F, 37 - I 37^ p = 0.25) or between the extra male and group size (F, 37 = 0.03, P = 0.87). AIE of alpha pairs differed marginally between the sexes (group sizes combined): 20.22 ± 2.44% (males), 34.16 ± 2.54% (females) (Fj 37 = 3.78, P = 0.059; Fig. 3). AIE of alpha pairs also differed between group sizes (males and females combined, alpha birds only): 31.44 ± 3.20% (one breeding pair), 25.80 ± 3.11% (two breeding pairs), and 20.53 ± 4.19% (three breeding pairs) (F137 = 4.04, P = 0.043; Fig. 3). Again, the interaction between sex and group size (F137 = 0.40, P = 0.53) and the interaction between the extra male and group size (Fi 37 = 0.29, P = 0.59) were not significant. In beta pairs, all factors tested above did not significantly affect either RIE or AIE. DISCUSSION To our knowledge, this is the first study showing that constancy of incubation increas- es with increasing group size. Greater con- stancy of incubation may provide a more sta- ble thermal environment, resulting in more rapid embryo development (Deeming 2002). This suggests that sharing the incubation ef- fort does not necessarily lead only to “load lightening” of other breeders (Brown and Brown 1981, Crick 1992). Breeders may also maintain the same level of incubation effort, thus increasing overall incubation effort as more individuals participate. This response may be analogous to the “additive” effects of helpers during nestling provisioning (Hatch- well 1999), presumably increasing the fitness of breeders by increasing the number of off- spring. Here, we showed that both alpha males and females reduced their incubation effort when more individuals were present in the group. Beta pairs, however, maintained a constant ef- fort when more individuals participated in in- cubation. This phenomenon explains why constancy of incubation varies positively with group size. Attracting additional group mem- bers reduces the cost of parental care for alpha individuals while providing improved incu- bation constancy. Given that the alpha females contribute more to incubation than other members of their respective groups, it is rea- sonable to expect that alpha females could gain more benefit from larger groups in terms of lightening their work load. This may ex- plain why the survival probabilities of alpha females, but not alpha males, increase with group size (Shen 2002). In this study, alpha females contributed sig- nificantly more to diurnal incubation effort than other individuals. Yuan et al. (2004) found that female yuhinas also contribute more to nocturnal incubation. Female-biased asymmetry in parental care has long been at- tributed to a sex-bias in the uncertainty of par- entage (Trivers 1972, Queller 1997). In co- operatively breeding species, it has been ar- gued that selection favors male survival over parental care, whereas in females, selection fa- vors behavior that promotes offspring surviv- al, largely due to the fact that females have a greater confidence of parentage (Cockbum 1998, Hatchwell 1999). Extra-group paternity is high in yuhinas (21.4%; H-WY unpubl. data), and it seems appropriate to adopt the parentage uncertainty hypothesis to explain the high incubation effort of alpha females, but not males. However, in most joint-nesting species, the male does the bulk of incubating, especially at night (Vehrencamp 2000, Veh- rencamp and Quinn 2004). A possible func- tional explanation for males taking over noc- turnal incubation — which is energetically ex- pensive and imposes a greater risk of preda- tion— is that it allows their mates to produce larger clutches, lay replacement clutches, or contribute more to nestling care (Vehrencamp 2000). Moreover, the low incidence of extra- group paternity in those joint-nesting species may promote greater contributions of parental care among the males (review in Cockbum 1998); yuhinas, on the other hand, exhibit a greater extent of extra-pair paternity. There- fore, different fitness components must be considered to predict patterns of variation in parental investment strategies in complex so- cial groups. Although parental investment strategies de- veloped according to provisioning effort can be analogous to incubation effort, as we have shown above, we believe that there are some important differences that need further exam- ination. For example, are there any differences in parental investment strategies with respect to incubation effort and provisioning, and, if so, why? For cooperatively breeding mam- Yuan et al. • PARENTAL INVESTMENT IN TAIWAN YUHINAS 311 mals, much more attention has been given to comparing division of labor of different activ- ities, such as babysitting, pup feeding, and guarding, than for birds (Clutton-Brock et al. 2003). In birds, Magrath and Komdeur (2003) also argued that the tradeoffs between parental effort and mating effort have more commonly been observed during incubation than during the nestling feeding period in cooperatively breeding species, although little empirical ev- idence supports this view. Another related question is why there are fewer helpers in co- operatively breeding species participating in incubation. Clutton-Brock (1991) speculated that one stimulus for male help with incuba- tion may be an attempt to minimize the prob- ability that females will destroy each others’ eggs. Few studies have been conducted to evaluate this hypothesis. Given that incuba- tion is an important component of reproduc- tive costs in birds (Reid et al. 2002a), it is surprising that there are so few studies dealing with parental investment strategies during in- cubation in cooperatively breeding birds. Our study provides an example of different parental investment strategies exhibited by males and females during incubation, and a potential new group benefit of cooperative breeding that increases incubation effort. We also suggest that AIE should be a better mea- sure than RIE of an individual’s incubation effort. Because AIE reflects the real effort and cost of nesting that each individual contributes and bears, respectively, and because RIE rep- resents only the relative contribution (poten- tially omitting additional information — as we found in this study), only AIE can indicate the extent to which work loads are lightened as group size increases. Future work on incuba- I tion in cooperatively breeding birds will give us a better understanding of the effect of help- ers and co-breeders on other group members’ I parental effort and, thus, will have profound ' implications for the evolution of different in- vestment strategies in different cooperative breeding systems. ACKNOWLEDGMENTS We thank S. L. Vehrencamp, H. L. Mays. Jr., and three anonymous reviewers for valuable comments on a draft of our manuscript. We thank I- Vermeylcn for statistical ccmsultation. We also thank M.-C. Tsai, K.- Z. Lin. and workers at Meifeng harm for logistical support. Finally, we greatly appreciate the volunteers from the NTU Nature Conservation Students’ Club and School of Forestry and Resource Conservation, in particular H.-Y. Hung, I.-H. Chang, K.-D. Zhong, and S.-W. Fu for their help in the field. This study was supported by the National Science Council and the Council of Agriculture, Taiwan. LITERATURE CITED Brown, J. L. 1983. Cooperation — a biologist’s dilem- ma. Advances in the Study of Behavior 13:1-37. Brown, J. L. and E. R. Brown. 1981. Kin selection and individual selection in babblers. Pages 244- 256 in Natural selection and social behavior: re- cent research and new theory (R. D. Alexander and D. E. Tinkle, Eds.). Chiron Press, New York. Brown, J. L., D. D. Dow, E. R. Brown, and S. D. Brown. 1978. Effects of helpers on feeding of nestlings in Grey-crowned Babbler (Pomatosto- mus temporalis). Behavioral Ecology and Socio- biology 4:43-59. Clements, J. F. 2000. Birds of the world: a checklist. Ibis Publishing, Vista, California. Clutton-Brock, T. H. 1991. The evolution of parental care. Princeton University Press, Princeton, New Jersey. Clutton-Brock, T. H., A. E Russell, and L. L. Shar- pe. 2003. Meerkat helpers do not specialize in par- ticular activities. Animal Behaviour 66:531-540. CocKBURN, A. 1998. Evolution of helping behavior in cooperatively breeding birds. Annual Review of Ecology and Systematics 29:141-177. Crick, H. Q. P. 1992. Load-lightening in cooperatively breeding birds and the cost of reproduction. Ibis 134:56-61. Deeming, D. C. 2002. Behavior patterns during incu- bation. Pages 63-87 in Avian incubation: behav- ior, environment, and evolution (D. C. Deeming, Ed.). Oxford University Press, New York. Emlen, S. T. and P. H. Wrege. 1991 . Breeding biology of White-fronted Bee-eaters at Nakuru: the influ- ence of helpers on breeder fitness. Journal of An- imal Ecology 60:309-326. Fridoles.son, a. K. and H. Ellegren. 1999. A simple and universal method for molecular sexing of non- ratite birds. Journal of Avian Biology 30: 1 16-121. Hatchwell, B. j. 1999. Investment strategics of breed- ers in avian cooperative breeding systems. Amer- ican Naturalist 154:205-219. Hi-;in.S()HN, R. and A. Cockburn. 1994. Helping is costly to young birds in cooperatively breetling White-winged Choughs. Proceedings of the Royal Society of London, .Series B 256:293-298. Kokko. H.. R. a. Johnstone, and T. H. C4 i iton- Br(K'k. 2(M)1. The evolution of cooperative breeti- ing through group augmentation. I’roceedings of the Royal Society London, Series B 268:187 196. Komdi UR, .1. 1994. Experimental evidence for helping and hindering by previous offspring in the eoop- crative-breetling .Seychelles Warbler Arrocephalus 312 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 sechellensis. Behavioral Ecology and Sociobiolo- gy 34:175-186. Magrath, M. J. L. and J. Komdeur. 2003. Is male care compromised by additional mating opportu- nity? Trends in Ecology and Evolution 18:424— 430. Ql ELLER, D. C. 1997. Why do females care more than males? Proceedings of the Royal Society of Lon- don. Series B 264:1555—1557. Reid, J. M., P. Monaghan, .and R. G. N.ager. 2002a. Incubation and the costs of reproduction. Pages 314-324 in Avian incubation: behaviour, environ- ment. and evolution (D. C. Deeming, Ed.). Oxford University Press, New York. Reid. J. M., P. Monaghan, .ant> G. D. Rltcton. 2002b. Males matter: the occurrence and consequences of male incubation in starlings (Stumus vulgaris). Behavioral Ecology and Sociobiology 51:255- 261. Schall, R. 1991. Estimation of generalized linear models with random effects. Biometrika 78:719— 727. Shen, S.-E 2002. Ecology of cooperatively breeding Taiwan Yuhinas (Yuhina brunneiceps) in Meifeng areas. M.Sc. thesis. National Taiwan University, Taipei. SPSS, Inc. 2003. SPSS base 12.0 for Windows user’s guide. SPSS Inc., Chicago, Illinois. Trivers, R. L. 1972. Parental investment and sexual selection. Pages 136-179 in Sexual selection and the descent of man, 1871-1971 (B. G. Campbell, Ed.). Aldine, Chicago, Illinois. Vehrencamp, S. L. 1977. Relative fecundity and pa- rental effort in communally nesting anis, Croto- phaga sulcirostris. Science 197:403-405. Vehrenc.amp, S. L. 2000. Evolutionary routes to joint- female nesting in birds. Behavioral Ecology 11: 334-344. Vehrencamp, S. L. and J. S. Quinn. 2004. Joint laying systems. Pages 177-196 in Cooperative breeding in birds: recent research and new theory (W. D. Koenig and J. Dickinson. Eds.). Cambridge Uni- versity Press, Cambridge, United Kingdom. VissER, M. E. .ANT) C. M. Lessells. 2001. The costs of egg production and incubation in Great Tits {Pa- rus major). Proceedings of the Royal Society of London, Series B 268:1271—1277. Yamashina, M. 1938. A sociable breeding habit among timaliine birds. Proceedings of the Inter- national Ornithological Congress 9:453-456. Yuan, H.-W., M. Liu, .and S.-E Shen. 2004. Joint nest- ing in Taiwan Yuhinas: a rare passerine case. Con- dor 106:862-872. Short Communications Wilson Bulletin 1 17(3):313-315, 2005 Rolling Prey and the Acquisition of Aerial Foraging Skills in Northern Mockingbirds Joanna R. Vondrasek* ABSTRACT. — I describe an unusual food-handling behavior performed by juvenile Northern Mocking- birds (Mimus poly g lottos). In the course of one morn- ing, I observed juvenile Northern Mockingbirds re- peatedly roll several prey items down the incline of a roof in Charlottesville, Virginia. I discuss this behavior in the context of the development of aerial foraging skills. Received 20 September 2004, accepted 26 April 2005. Newly independent passerines are often in- efficient foragers and are under selective pres- sure to acquire foraging skills quickly once parental care has ended (Weathers and Sulli- van 1991). Foraging skills take time to master, and some types of foraging, such as aerial hawking, take longer to master than others (Moreno 1984, Marchetti and Price 1989). Object play, which often involves the drop- ping and catching of both food and non-food items, might be an important adaptive behav- ior that helps newly independent birds devel- op such foraging skills (Gamble and Cristol 2002). Instances of apparent solitary object play are occasionally reported in birds, but few such instances have been reported in non- corvid passerines (Ficken 1977, Diamond and Bond 2003). Here, 1 report an observation of unusual prey manipulation and possible object play in a non-corvid passerine, the Northern I Mockingbird {Mimu.s polyglotto.s). OBSERVATION I On 27 July 2004, in suburban Charlottes- I ville, Virginia, from 08:46 to 09:28 EDT (25° C, light rain), I observed a trio of juvenile I Northern Mockingbirds on my neighbor’s ' rooftop (—35° incline). I observed without binoculars for the first 10 min and with bin- oculars for the remaining time. At 08:46, I saw three juvenile Northern ' Dept, of Biology, Univ. of Virginia, Charlottes- ville, VA 22904, USA; e-mail: jv8nC3Wirginia.edu Mockingbirds perched on the peak of the roof. One of the juveniles (bird A) had an earth- worm (4-5 cm in length, clitellum visible) in its beak. It dropped the worm, which formed into a ball and rolled down the roof about 1 m. Bird A ran after and grabbed the worm in its beak. The other two juveniles (B and C) pursued A. When B and C came within 0.5 m of A, A jumped up, flashed its white wing patches, and lifted its feet into the air (see Hayslette 2003 for more on wing-flashing). Birds B and C ran back up to the rooftop. Bird A then flew back to the rooftop, dropped the worm, let it roll 1 m down the incline, ran after it, grabbed the worm in its beak, thrashed the worm against the roof, dropped the worm, let it roll another 1 m down the incline, re- trieved it and returned to the rooftop. Birds B and C ran toward A at the top of the roof, at which point bird A flew up about 1.5 m above the roof line, with the worm in its beak. Two adult-plumaged Northern Mocking- birds flew onto the roof. One adult bird flew toward birds B and C, both of which flew off out of sight. Bird A jumped up and wing- flashed about 1 m from one of the adult North- ern Mockingbirds. After a few minutes, the adult Northern Mockingbirds left. Bird A, now alone on the roof, spent the next 4 to 5 min rolling the worm down the roof, usually 1 m at a time, retrieving it, thrashing it on the surface of the roof, flying or walking back to the roof line, and rolling the worm down again. This behavior was repeated a total of seven times. Finally, bird A consumed the worm and flew out of sight at 08:56. At 09:20, one juvenile Northern Mocking- bird returned to the roof carrying a small winged in.sect (<2 cm in length) in its beak. It dropped the in.sect on the roof ridge, picked it up, and dropped it again, at which point the in.sect rolled about 0.3 m down the roof, fhe bird picked up the insect, ate it, and flew off. 313 314 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 Five min later, one juvenile Northern Mockingbird returned with a large larva, 4-5 cm long, possibly Ceratomia catalpae (Wag- ner et al. 1997). The larva had roughly 10 parasitoid wasp pupae attached to its thorax. Two other juvenile Northern Mockingbirds ar- rived and harassed the owner of the larva. The owner dropped the larva, which rolled down the roof about 1 m. The owner retrieved the larva, brought it to the top of the roof, and thrashed the larva on the edge of the roof. This rolling, thrashing, and retrieving behav- ior was repeated three additional times. Some of the wasp pupae attached to the larva fell off during the thrashing. The owner then flew away with the intact larva in its beak. The two remaining juveniles alternately displaced each other and then flew off together. The birds did not reappear on the roof in the next 2 hr. DISCUSSION Newly independent Northern Mockingbirds in south Florida are less proficient at prey cap- ture than adults (Breitwisch et al. 1987), and studies of Northern Mockingbirds and other passerines have revealed that proficient aerial foraging takes longer to achieve than profi- cient ground foraging (Moreno 1984, Breit- wisch et al. 1987). The rolling of invertebrate prey, as reported here, is possibly a method that Northern Mockingbirds use to develop aerial foraging skills. Juvenile Northern Mockingbirds also have been observed pick- ing up gravel and other inedible objects from the ground and then dropping them, possibly a result of inexperience with prey, but possi- bly an adaptive behavior involved in the ac- quisition of ground foraging skills (Breitwisch et al. 1987). In the present observation, the roof allowed the prey to roll away from the Northern Mockingbirds, but not as quickly as if dropped in mid-air. Therefore, the roof might provide a “safe” place for young birds to practice catching air-bome prey or retriev- ing prey dropped in mid-air (Gamble and Cristol 2002). An alternate explanation is that the juvenile Northern Mockingbirds chose an inappropri- ate location to process prey items and the roll- ing was incidental. Many passerines, such as Spotted Antbirds {Hylophylax naevioides), thrash prey against hard surfaces prior to con- sumption (Willis 1972), and adult Northern Mockingbirds in North Carolina have been observed to do the same (A. Skypala pers. comm.). The juveniles I observed simply could have chosen a poor place to thrash prey items. This observation highlights the difficulty of determining whether instances of apparent play are an adaptive part of an animal’s be- havioral repertoire or whether they are inci- dental outcomes resulting from a lack of ex- perience. Play is notoriously difficult to define and is frequently a catch-all term for any seemingly purposeless behavior, especially if it is observed in young animals (Martin and Caro 1985, Bekoff and Byers 1998, Diamond and Bond 2003). Distinguishing between adaptive play behavior and inexperience is challenging, but such distinctions can lead to insights about the selective pressures that shape learning (Martin and Caro 1985). Lon- gitudinal studies following individuals would be required to determine whether Northern Mockingbirds that engage in prey rolling as juveniles are more efficient at aerial prey cap- ture as adults or achieve aerial proficiency more quickly than birds that do not roll prey down inclines (Gamble and Cristol 2002). ACKNOWLEDGMENTS I would like to thank A. Skypala, R. H. Wiley, A. B. Bond, and two anonymous referees for suggestions on an earlier version of this manuscript. I also thank R. Fox for information on parasitoid wasp life cycles. LITERATURE CITED Bekoff, M. and J. A. Byers (Eds.). 1998. Animal play: evolutionary, comparative and ecological perspective. Cambridge University Press, Cam- bridge, United Kingdom. Breitwisch, R., M. Diaz, and R. Lee. 1987. Foraging efficiencies and techniques of juvenile and adult Northern Mockingbirds (Mimus polyglottos). Be- haviour 101:225—235. Diamond, J. and A. B. Bond. 2003. A comparative analysis of social play in birds. Behaviour 140: 1091-1115. Ficken, M. S. 1977. Avian play. Auk 94:573—582. Gamble, J. R. and D. A. Cristol. 2002. Drop-catch behaviour is play in Herring Gulls {Larus argen- tatus). Animal Behaviour 63:339-345. Hayslette, S. E. 2003. A test of the foraging function of wing-flashing in Northern Mockingbirds. Southeastern Naturalist 2:93-98. Marchetti, K. and T. Price. 1989. Differences in the foraging of juvenile and adult birds: the impor- SHORT COMMUNICATIONS 315 tance of developmental constraints. Biological Re- views 64:51-70. Martin, R and T. M. Caro. 1985. On the functions of play and its role in behavioral development. Pages 59-103 in Advances in the study of behav- ior, vol. 15 (J. S. Rosenblatt, C. Beer, M.-C. Bus- nel, and P. J. B. Slater, Eds.). Academic Press, New York. Moreno, J. 1984. Parental care of fledged young, di- vision of labor, and the development of foraging techniques in the Northern Wheatear {Oenanthe oenanthe L.). Auk 101:741-752. Wagner, D. L., V. Giles, R. C. Reardon, and M. L. McManus. 1997. Caterpillars of eastern forests, ver. 11APR2001. FHTET-96-34, USDA Forest Service, Forest Health Technology Enterprise Team, Morgantown, West Virginia. http://www. npwrc.usgs.gOv/resource/2000/cateast/cateast.htm (accessed 27 July 2004). Weathers, W. W. and K. A. Sullivan. 1991. Foraging efficiency of parent juncos and their young. Con- dor 93:346-353. Willis, E. O. 1972. The behavior of Spotted Antbirds. Ornithological Monographs, no. 10. Wilson Bulletin 1 17(3):315-316, 2005 Above-ground Nesting by Northern Bobwhite Theron M. Terhune,'’^’"^ D. Clay Sisson, ^ and H. Lee Stribling* I ABSTRACT — The Northern Bobwhite (Colinus j virginianus) is one of the most studied game birds in North America. It is a ground-nesting galliform capa- I ble of producing multiple nests during a single season. Since 1993, personnel of the Albany Quail Project Ij have radio-tagged >6,000 bobwhites and monitored >2,000 nests via radio telemetry on private lands in southwestern Georgia. We have observed nests in I some peculiar places; however, every nest that we have I monitored has been on the ground. Previously, no case I of above-ground nesting has been documented for this i species. Here, we report an above-ground nest, found j in June 2001. Received 27 September 2004, accepted i 21 May 2005. : Gallinaceous birds typically nest on the ground, and the Northern Bobwhite {Colinus virginianus) is no exception. Bobwhites usu- ally nest in herbaceous vegetation consisting of mixed grasses and forbs, such as that found along fencerows and roadsides or in idle/fal- low areas and other early successional habi- I tats. The bobwhite has a propensity to nest near edges (usually within 15.5 m) of roads, fields, disked strips, or pathways (Stoddard ' School of Forestry and Wildlife Sciences, 108 M. I White Smith Hall, Auburn Univ., Auburn, AL 36849, USA. ^ Albany Quail Project, c/o Pineland Plantation, Kte. 1 Box 1 15, Newton, GA 39870, USA. ^Current address: 200 Brookstone Dr, Athens, GA 30605, USA. ■‘Corresponding author; e-mail: terhutmCohiga.edu 1931, Rosene 1969, Simpson 1972). Typical nests are constructed primarily of grasses (e.g., Andropogon spp.) and pine (Pinus spp.) needles, although other materials may include mosses, leaf litter, and tree-limb debris. It is well documented that bobwhites use a wide variety of nesting sites (Stoddard 1931, Ro- sene 1969, Simpson 1972, Klimstra and Rose- berry 1975) and some are located in peculiar places (e.g., ditch banks, dense stands of hard- woods, and flowerbeds). Carter et al. (2002) reported the importance of prickly pear (Opuntia spp.) as nesting cover following a prescribed burn in Texas. Whereas bobwhite nesting ecology has been thoroughly studied throughout its range, above-ground nesting has not been reported in the peer-reviewed lit- erature. During the course of our ongoing studies for the Albany Quail Project, we have radio- tagged >6,000 bobwhites and found >2,000 nests. The study area is located on private lands in Baker County, southwestern Georgia (3r’21'35"N, 84" 16' 18"W) in the Upper Coastal Plain physiographic region. Study sites are characteri/.cd by old-field pine forests with relatively low basal area that are inten- sively managed for bobwhite. Habitat man- agement regimes typically include annual burning, seasonal diskifig. dnun-chopping and mowing, supplemental feeding, and mamma- lian nest-predator control. As a result of these 316 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 intense management regimes, these areas maintain abundant wild bobwhite populations ranging from 1.48 to 7.41 birds/ha (Yates et al. 1995; Sisson et al. 1997a, b). Between 16 and 19 June 2001, an employee at one of our study areas watched a pair of bobwhites spend a considerable amount of time near a holly bush {Ilex sp.) in his front yard. We surmised that the female was nesting in the holly bush, and on 9 July, we returned to find 16 pipped bobwhite eggs in a nest in the bush. Several days later, we observed a brood near the holly bush. The nest was built above ground (76.2 cm), on top of a passerine nest (unknown species) composed of sticks and dead leaves. It was typical for bobwhite nests, however, having been lined with pine needles. The above-ground nesting reported here may not be entirely novel among bobwhites, as Rosene (1969) reported a similar nesting record (a second-hand observation), from which 12 eggs hatched successfully. Above- ground nests have also been reported for other gallinaceous species, including Wild Turkey {Meleagris gallopavo) and Ring-necked Pheasant {Phasianus colchicus). Fletcher and Parker (1994) reported a Wild Turkey nest 2.4 m above ground in a live oak (Quercus vir- giniana). They speculated that the unusual nest site may have been selected to avoid dep- redation by raccoons (Procyon lotor) or feral hogs {Sus scrofa). Cobb et al. (1989) reported two separate instances in which Wild Turkeys nested above ground — on a log and on a stump in a water tupelo {Nyssa aquatica)PoM cypress (Taxodium distichum) swamp. Cobb et al. (1989) suggested that the anomalous nesting behavior was a result of the hens hav- ing experienced flooding of their nests during the preceding breeding season. Pheasants, es- pecially tragopans (Tragopan spp.), also have been known to nest above ground (J. P. Carroll pers. comm.). The aberrant nesting behavior we observed demonstrates the ability of bobwhite to use almost any available substrate. Of 2,117 nests that we found during the Albany study, 1,503 were in upland piney woods, 551 were in fal- low fields, and 58 were in hardwood-domi- nated sites; only 5 nests were in other habitats (ditch banks, creek swamps, cypress-pond edges, and flowerbeds). Whereas most (71%) nests were in upland piney woods, the re- maining 29% were in areas lacking the bunch grasses more typical of bobwhite nesting hab- itat. Indeed, the range of nesting habitats re- ported indicates that bobwhites are much more opportunistic nesters than once realized. ACKNOWLEDGMENTS We are greatly indebted to the landowners in south- western Georgia for the use of their land and funding for the project. We also thank T. Rumph for his par- ticipation and willingness to report his observations to the Albany Quail Project. LITERATURE CITED Carter, P. S., D. Rollins, and C. B. Scott. 2002. Initial effects of prescribed burning on survival and nesting success of Northern Bobwhites in west-central Texas. Proceedings of the National Quail Symposium 5:129-134. Cobb, D. T, P. D. Doerr, and M. H. Seamster. 1989. Above-ground nesting by Wild Turkeys. Wilson Bulletin 101:644-645. Fletcher, W. O. and W. A. Parker. 1994. Tree nest- ing by Wild Turkeys on Ossabaw Island, Georgia. Wilson Bulletin 106:562—563. Klimstra, W. D. and J. L. Roseberry. 1975. Nesting ecology of the bobwhite in southern Illinois. Wild- life Monograph, no. 41. Rosene, W. 1969. The Bobwhite quail: its life and management. Rutgers University Press, New Brunswick, New Jersey. Simpson, R. C. 1972. A study of Bobwhite quail nest initiation dates, clutch sizes, and hatch sizes in southwestern Georgia. Proceedings of the Nation- al Quail Symposium 1:199-204. Sisson, D. C., D. W. Speake, and H. L. Stribling. 1997a. Survival of Northern Bobwhites on areas with and without liberated bobwhites. Proceedings of the National Quail Symposium 4:92-94. Sisson, D. C., H. L. Stribling, and D. W. Speake. 1997b. Effects of supplemental feeding on home range size and survival of Northern Bobwhites in south Georgia. Proceedings of the National Quail Symposium 4:128-131. Stoddard, H. L. 1931. The Bobwhite quail: its habits, preservation and increase. Charles Scribner s Sons, New York. Yates, S., D. C. Sisson, H. L. Stribling, and D. W. Speake. 1995. Northern Bobwhite brood habitat- use in south Georgia. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 49:498-504. SHORT COMMUNICATIONS 317 Wilson Bulletin 1 17(3):317-319, 2005 Divorce in the Canary Islands Stonechat {Saxicola dacotiae) Juan Carlos Illera^ ABSTRACT — I report the first case of divorce for the Canary Islands Stonechat {Saxicola dacotiae), an endemic bird species of the semiarid island of Fuer- teventura (Canary Islands, Spain). I studied 72 pairs during three breeding seasons (2000-2001, 2001- 2002, and 2002-2003). In 2001-2002, a female di- vorced after a successful first nesting. This female set- tled in a neighboring territory where the owner was unpaired, built a new nest, and laid four eggs. The low rate of divorce (1.4%) suggests that unforced mate changes by Canary Islands Stonechats are rare. Re- ceived 22 July 2004, accepted 31 May 2005. The Canary Islands Stonechat {Saxicola dacotiae) is an island endemic restricted to Fuerteventura Island, Canary Islands, Spain. Bibby and Hill (1987) estimated the popula- tion size of the species as 650-850 pairs. Al- though there are no recent estimates of the abundance of the species, its status has been modified recently by the Spanish Ornitholog- ical Society (SEO/BirdLife) from “Near Threatened” to “Endangered” on the basis of increasing destruction and alteration of its habitats (Illera 2004a). In spite of its critical status, very little is known about the biology of this species. Here, I describe the first case of divorce in the Canary Islands Stonechat. The Canary Islands archipelago is located in the Atlantic Ocean, 100-460 km off the northwest coast of Africa, and comprises sev- en main volcanic islands and several islets. Fuerteventura is the easternmost (28° 46' N, 14°31'W), second largest (1,660 km^), and oldest island (approximately 22 million years old; Carracedo and Day 2002). The climate is semiarid with dry summers and scarce rainfall in autumn and winter (mean annual precipi- tation = 117 mm; Mar/.ol-Jacn 1984). The vegetation is mainly sparse xerophytic shrub- land. Canary Islands wStoncchats arc largely re- ' Depto. de Biologfa Animal (Zoologfa), F acultail do Biologi'a, Univ. de La Laguna, L-3X206 La l.aguna (Tenerite). Canary fslands, Spain; e-mail: jcilleraC?’ ull.es stricted to slopes of stony fields and ravines covered by medium to large shrubs and large boulders; they avoid lava and sandy habitats (Illera 2001). Stonechats are thought to be monogamous, sedentary, and territorial (Mar- tin and Lorenzo 2001, Urquhart 2002, Illera 2004b). Territory boundaries usually abut those of neighboring pairs (JCI pers. obs.). After settling, individual birds are extremely faithful to their sites all year long, i.e., they do not move after the breeding season, al- though territory boundaries may shift between successive breeding seasons (Illera 2004b; JCI unpubl. data). The breeding period extends from December to April (Martin and Lorenzo 2001, Urquhart 2002, Illera 2004b; JCI un- publ. data). Reproductive effort and the du- ration of the breeding period depend proxi- mately on rainfall and ultimately on food (ar- thropod) availability (Illera 2004b; JCI un- publ. data). Pairs breed over more extended periods and lay two clutches in wet years, whereas in dry years they breed only once or not at all. Clutches are also larger in wet than in dry years (Illera 2004b; JCI unpubl. data). Results presented here were obtained dur- ing studies of stonechat breeding success and site fidelity. Birds were trapped, banded, and monitored (Illera 2004b; JCI unpubl. data). I monitored 72 pairs over three breeding sea- sons (2000-2001, 2001-2002, and 2002- 2003) at 12 study sites in which 1-10 pairs bred at least once in the 3 years. Of 72 pairs, 1 color-banded 1 14 individuals: 32/42 (2000- 2001) , 39/47 (2001-2002), and 43/54 (2002- 2003). Due to sexual dimorphism and individ- ual variability in phenotypic traits, I was also able to identify unbanded individuals. How- ever, because sexual dimorphism traits shift after the molt period (Illera and Atienza 2002) , they were only used to identify indi- viduals within each breeding sea.son. The number of bantled pairs studied during two or more breeding periods was seven. I monitored pairs at least weekly from late October to ear- 318 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 ly November (pre-breeding period) until a month after the last fledgling left the nest (post-breeding period). The time spent moni- toring each pair during each visit varied be- tween 30 min and 2 hr. Stonechats nested once or not at all in the dry (27.3 mm rainfall) breeding season of 2000—2001, and laid two clutches in the two wet years (124.5 and 125.1 mm rainfall in 2002 and 2003, respectively; Illera 2004b; JCI unpubl. data). Of 72 pairs monitored, only one divorced within a breeding season (2001-2002). Di- vorce was not recorded for pairs monitored {n = 7) in successive breeding seasons. The case of divorce reported here was the result of de- sertion by a female that subsequently settled in a neighboring territory where the owner was unpaired. Desertion occurred after the original pair successfully reared a brood (three fledglings). In the first brood (about 15 days previous to divorce), during 90 min of obser- vation, 9 and 10 feeding visits were performed by the female and the male, respectively. In six visits to this territory, I did not observe the second male assisting with feeding young or encounters between the female and the sec- ond male. All three adults were color-banded. Fifteen days after the first brood fledged, the female built a new nest and laid four eggs. Both members of the new pair fed nestlings of the second brood, with no assistance from the divorced male. The nest was depredated, but the new pair did not attempt to breed again, and 2 weeks later the female disap- peared from the territory. The female’s origi- nal mate continued singing and feeding its three chicks alone during the 4 weeks after fledging. The divorced female never returned to her former territory even though the terri- tories were adjacent. The deserted male did not mate with another female during the re- mainder of the 2001-2002 breeding period, and he finally moved to a new territory 5 months later. Limited information is available on divorce in the genus Saxicola (Urquhart 2002). John- son (1961, 1971) recorded several cases of mate exchanges, polygyny, and polyandry in a population of Common Stonechat {S. tor- quata), both within a given breeding season and between successive breeding seasons. H. Flinks (in Urquhart 2002) reported that male Common Stonechats might be vulnerable to mate loss while feeding fledglings. Bibby and Hill (1987) reported that some unpaired male Canary Islands Stonechats assist with feeding young of established pairs. However, during 238.5 hr of observation of feeding (23 pairs), I did not record males or females assisting with feeding young. The low rate of within-season divorce (1.4%, n = 12 pairs; three breeding seasons) and the lack of between-season divorce (0/7) suggests that unforced mate changes by Ca- nary Islands Stonechats are rare. Strong site fidelity reported for this species (Illera 2004b; JCI unpubl. data.) also suggests that occur- rences of between-season divorce are rare. Di- vorce did not appear to have been triggered by poor breeding success, as mean fecundity of all pairs monitored over 3 years was 2.25 ± 0.15 SE (n = 68). The biotic and abiotic homogeneity of Fuerteventura and the likely costs associated with territory switching (e.g., increased probability of predation after a move, aggression of adjacent territory holders, and less efficient foraging in unfamiliar terri- tories; Jakob et al. 2001, Yoder et al. 2004) probably makes divorce maladaptive in this species. ACKNOWLEDGMENTS The Regional Government of the Canary Islands gave the official permit to band this threatened bird species. D. Santana and N. Hernandez provided worms used in trapping birds. A. Moreno and J. C. Atienza helped during banding sessions. M. Nogales reviewed an early draft. M. Diaz encouraged me to write this note and provided useful suggestions that improved this paper a great deal. K. Koivula, E. D. Urquhart, and an anonymous referee provided useful comments during revision. LITERATURE CITED Bibby, C. J. and D. A. Hill. 1987. Status of the Fuer- teventura Stonechat Saxicola dacotiae. Ibis 129: 491-498. Carracedo, J. C. AND S. Day. 2002. Canary Islands. Classic geology in Europe series. Terra Publish- ing, Hertfordshire, London, United Kingdom. Illera, J. C. 2001. Habitat selection by the Canary Islands Stonechat (Saxicola dacotiae) (Meade- Waldo, 1889) in Fuerteventura Island: a two-tier habitat approach with implications for its conser- vation. Biological Conservation 97:339-345. Illera, J. C. 2004a. Tarabilla Canaria (Saxicola daco- tiae). Pages 327-328 in Libro rojo de las aves de Espana (A. Madrono, C. Gonzalez, and J. C. Atienza, Eds.). SEO/BirdLife-Direccion General SHORT COMMUNICATIONS 319 de Biodiversidad/Ministerio de Medio Ambiente, Madrid, Spain. Illera, J. C. 2004b. Biogeografia y ecologia de la Ta- rabilla Canaria (Saxicola dacotiae) con implica- ciones para su conservacion. Ph.D. dissertation, University of La Laguna, Tenerife, Spain. Illera, J. C. and J. C. Atienza. 2002. Determinacion del sexo y edad en la Tarabilla Canaria Saxicola dacotiae mediante el estudio de la muda. Ardeola 49:273-281. Jakob, E. M., A. H. Porter, and G. W. Uetz. 2001. Site fidelity and the costs of movement among territories: an example from colonial web-building spiders. Canadian Journal of Zoology 79:2094- 2100. Johnson, E. D. H. 1961. The pair relationship and po- lygyny in the Stonechat. British Birds 54:213- 225. Johnson, E. D. H. 1971. Observations on a resident population of Stonechats in Jersey. British Birds 64:201-213, 267-279. Martin, A. and J. A. Lorenzo. 2001. Aves del Ar- chipielago Canario. Francisco Lemus Editor, La Laguna, Tenerife, Spain. Marzol-Jaen, M. V. 1984. El clima. Pages 157-202 in Geografia de Canarias (L. Afonso, Dir.). Inter- insular Canaria, Santa Cruz de Tenerife, Spain. Urquhart, E. D. 2002. Stonechats: guide to the genus Saxicola. Christopher Helm, London, United Kingdom. Yoder, J. M., E. A. Marschall, and D. A. Swanson. 2004. The cost of dispersal: predation as a func- tion of movement and site familiarity in Ruffed Grouse. Behavioral Ecology 15:469-476. Wilson Bulletin 1 17(3):3 19-321, 2005 Regurgitated Mistletoe Seeds in the Nest of the Yellow-crowned Tyrannulet (Tyrannulus elatus) Peter A. Hosner’ ABSTRACT. — I describe a Yellow-crowned Tyran- nulet {Tyrannulus elatus) nest built largely of mistletoe seeds, which differs from the cup of plant matter typ- ically constructed by this species. Mistletoe seeds have been observed in the nests of at least two other bird species, but this observation is the first where the nest appeared to be purposely constructed from .seeds, pos- sibly to take advantage of their adhesive properties. Received 20 September 2004, accepted 31 May 2005. Adhesive substances, such as the saliva of Aerodramus and Collocalia swiftlets (Smy- thies 1999, Han.sell 2000), and regurgitated materials, such as fruits and .seeds ingested by Oilbirds (Steatorni.s caripen.si.s; Hilty and Brown 1986), are regularly u.sed for nest con- struction by the.se and a few other bird spe- cies. However, the use of adhesive mistletoe fruit seeds in nest construction is almost un- known. There have been only two other re- ports of mistletoe seeds used in nest construc- tion, both in nests of unrelated flycatcher spe- ' Dept, (^f Ecology and Evolutionary Biology. Cor- nell Univ., Ithaca. NY 14853. U.SA; e-mail: pah24@cornell.edu cies (Tyrannidae: Traylor 1977; Lanyon 1984, 1988; Mobley 2002; Fitzpatrick 2004). A sin- gle atypical nest of Fork-tailed Flycatcher {Tyrannus savana) in Brazil contained mistle- toe seeds regurgitated by an adult into the nest cup during incubation, apparently to help keep the loosely structured nest from falling apart (Sick 1985). Other descriptions of T. savana nests make no mention of mistletoe seeds (Hilty and Brown 1986, Stiles and Skutch 1989, Howell and Webb 1995, Hilty 2003, Fitzpatrick 2004). In Venezuela, a single glob- ular nest of the Great Kiskadee {Pitangns sul- pha ratus) was observed to contain a few re- gurgitated mistletoe seeds about the lower rim and below the side entrance to the nest (J. A. Mobley pers. obs.). No published descriptions of P. sulphuratus nests mention mistletoe seeds (Hilty and Brown 1986, Stiles and Skutch 1989, Howell and Webb 1995, Hilty 2003, F^'itzpatrick 2004). Here, I provide the first report of a nest covered almost entirely with mistletoe .seeds, by the Yellow-crowned Tyrannulet {Tyrannulus clatu.s). Birds, including /’. elatus (Hilty and Brown 320 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 1986, Stiles and Skutch 1989, Hilty 2003, Fitzpatrick 2004), are well-known consumers and dispersers of mistletoes (Viscaceae, Lo- ranthaceae) in the Neotropics (e.g., Calder and Bernhardt 1983, Sargent 1994, Restrepo et al. 2002). However, other uses of these plants by birds are poorly known. The seeds of some mistletoe species contain an extremely adhe- sive layer of viscin tissue under the fruit flesh; once digested, viscin can sometimes elongate to form a thread 3-4 cm long that is attached to one end of the seed. During regurgitation or defecation of the seed, the loose end of this thread will stay in the stomach or cloaca until it is wiped on a substrate, usually a branch. Leverage is then used to remove the strand entirely from the body (Kuijt 1969, Calder and Bernhardt 1983). This is an effective dis- persal strategy for mistletoes, as the seeds are occasionally placed on a branch in a location suitable for germination. The T. elatus nest was found on 20 March 2004, on Barro Colorado Island, Panama (9° 9' 49" N, 79° 50' 16" W; 80 m in elevation) in a clearing in humid, lowland evergreen for- est. When found, the nest was complete and contained a single egg. The nest was placed approximately 7 m above ground on a small horizontal branch — about 2 cm in diameter — in a 20-m broadleaf evergreen tree parasitized by several mistletoe plants, on which the fly- catcher pair fed. The cup-shaped nest was small, approximately 5 cm in diameter (out- side rim to outside rim), and was built of un- determined plant material. Regurgitated seeds covered the entire exterior of the nest, and there was a band of regurgitated seeds that wrapped beneath the branch on which the nest was built. Seeds were also worked into the plant material in the nest’s interior. The mistletoe seeds were probably of the genus Struthanthus or Oryctanthus, with Stru- thanthus more likely based on the round (as opposed to more ovoid) seed shape (S. Sar- gent pers. comm.) Upon regurgitation, the seeds were a whitish color, but seeds already placed on the nest had dried and turned a crimson-red to orange-red color. The single egg was white with small, evenly dispersed blotches of pale cinnamon to raw umber. The color appeared to be from pigment in the egg- shell rather than from stains from the mistle- toe seeds, as the colors were different. The nest did not appear large enough to accom- modate a second egg. Nest-construction ma- terials and the pattern of egg markings dif- fered from those described in other published accounts (Penard and Penard 1910, Snethlage 1935, Hilty and Brown 1986, Stiles and Skutch 1989, Hilty 2003, Fitzpatrick 2004); these authors described the nest as a shallow cup built of small twigs, mosses, spiderwebs, grasses, tree bark, feathers, and other fine ma- terial, and containing a clutch of two un- marked white or cream-colored eggs. A nest of T. elatus found in the same clearing on Bar- ro Colorado in 2003 (R. Moore pers. obs.) was similar to the published descriptions; there- fore, the nest built of mistletoe seeds was not likely to have been a local adaptation. On 20 March 2004, the bird attending the egg (distinguishable from its mate by awk- wardly arranged feathers on the crown) left for short foraging bouts that lasted ~5 min. Upon returning to the nest, it would resume incubation, and then regurgitate three to four additional seeds on the nest. The bird then used its bill to move the seeds to a location on the nest’s exterior, or work them into the plant material in the cup wall, thus continuing to construct the nest after the egg was laid. Placement of each seed took a short period of time — between 5 and 15 sec in 3 hr of obser- vation. I observed four such foraging bouts followed by seed regurgitation and placement. Both the attending bird and its mate also wiped regurgitated seeds on branches in the nest tree. Both adults actively defended the territory against Palm Tanagers {Thraupis pal- marum) and Social Flycatchers {Myiozetetes similis), two other species that may consume mistletoe fruits. Two hypotheses might explain wiping mis- tletoe seeds on nests: either the adhesive prop- erties of the seeds were used intentionally to aid in nest construction, or the nest was sim- ply the most convenient object on which the incubating bird could wipe seeds. The careful placement of regurgitated seeds by T. elatus on the nest exterior, however, suggests that the seeds were being intentionally used for their adhesive properties to hold the small nest to- gether and to adhere it to the branch. Placing seeds underneath the supporting branch and working seeds into the nest cup takes more concentrated effort and care compared to wip- SHORT COMMUNICATIONS 321 ing them on the side of the nest or a nearby branch. Because mistletoe seeds are adhesive and viscin strands are strong, it seems possible that the seeds were used to strengthen the nest, perhaps allowing the overall size of the nest to be smaller than previously described nests, which would decrease the effort needed to build a nest. Because the bright, red-orange color of the seeds contrasted strongly with the surroundings, it seems unlikely that the seeds were used as camouflage. Conversely, Sick’s (1985) description of the T. savana nest and J. A. Mobley’s (pers. comm.) observations of P. sulphuratus nests indicate that the addition of mistletoe seeds to the nest may be only a convenient means of wiping seeds while incubating, with no intent to alter nest structure. Sick (1985) suggested the seeds were inadvertently voided in the nest; neither he nor J. A. Mobley (pers. comm.) observed active placement of, or nest building with, mistletoe seeds, and the few seeds present were not enough to affect nest construction. ACKNOWLEDGMENTS I would like to thank I. J. Lovette, Cornell Univer- sity, and the National Science Foundation (04222333) for funding fieldwork. I also thank R. Moore for ad- ditional observations; J. A. Mobley for observations and suggestions; K. Zyskowski for translations of two nest descriptions into English, as well as comments and suggestions; W. Belton, J. Tobias, M. Hansell, and S. Sargent for their expertise in Neotropical birds, nest biology, and mistletoe biology; and D. W. Winkler and M. J. Andersen for comments. Last, I thank R. E. Ben- netts and two anonymous reviewers for comments and suggestions that improved the manuscript. LITERATURE CITED Calder, M. and P. Bernhardt. 1983. The biology of mistletoes. Academic Press, New York. Fitzpatrick, J. W. 2004. Family Tyrannidae (tyrant- flycatchers). Pages 170-463 in Handbook of birds of the world, vol. 9: cotingas to pipits and wagtails (J. del Hoyo, A. Elliott, and D. A. Christie, Eds.). Lynx Edicions, Barcelona, Spain. Hansell, M. H. 2000. Bird nests and construction be- havior. Cambridge University Press, Cambridge, United Kingdom. Hilty, S. L. 2003. Birds of Venezuela, 2nd ed. Prince- ton University Press, Princeton, New Jersey. Hilty, S. L. and W. L. Brown. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey. Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York. Kuut, j. 1969. The biology of parasitic flowering plants. University of California Press, Berkeley. Lanyon, W. E. 1984. A phylogeny of the kingbirds and their allies. American Museum Novitates 2797:1-28. Lanyon, W. E. 1988. A phylogeny of the thirty-two genera in the Elaenia assemblage of tyrant fly- catchers. American Museum Novitates 2914:1- 57. Mobley, J. A. 2002. Molecular phylogenetics and the evolution of nest building in kingbirds and their allies (Aves: Tyrannidae). Ph.D. dissertation. Uni- versity of California, Berkeley. Penard, F. P. and a. P. Penard. 1910. De vogels van Guyana (Suriname, Cayenne en Demerara), vol. 2. Published by F. P. Penard, Paramaribo, Surina- me. Restrepo, C., S. Sargent, D. J. Levey, and D. M. Watson. 2002. The role of vertebrates in the di- versification of New World mistletoes. Pages 83- 98 in Seed dispersal and frugivory: ecology, evo- lution, and conservation (D. J. Levey, W. R. Silva, and M. Galetti, Eds.). CABI Publishing, New York. Sargent, S. 1994. Seed dispersal of mistletoes by birds in Monteverde, Costa Rica. Ph.D. disserta- tion, Cornell University, Ithaca, New York. Sick, H. 1985. Birds in Brazil: a natural history. Princeton University Press, Princeton, New Jer- sey. Smythies, B. E. 1999. Birds of Borneo, 4th ed. (re- vised by G. W. H. Davison). Natural History Pub- lications, Kota Kinabalu, Borneo. Snethlage, E. 1935. Beitrage zur Fortpflanzungs-biol- ogie brasilianischer Vogel. Journal fiir Ornitholo- gie 83:532-562. Stiles, F. G. and A. F. Skutch. 1989. A guide to the birds of Costa Rica. Cornell University Press, Ith- aca, New York. Traylor, M. A. 1977. A classification of the tyrant flycatchers (Tyrannidae). Bulletin of the Mu.seum of Comparative Zoology 148:129-184. Wilson Bulletin 1 1 7(3):322-326, 2005 Ornithological Literature Edited by Mary Gustafson BIRDS OF CHILE. By Alvaro Jaramillo, illustrated by Peter Burke and David Beadle. Princeton University Press, Princeton, New Jersey. 2003: 240 pp., 96 color plates. ISBN: 0691004994, $55 (cloth). ISBN: 069117403, $29.95 (paper). — South America has the most extensive bird fauna of any continent, yet for many years lacked adequate field identifica- tion guides. For much of the continent, the lack of field guides has now been remedied with a series of books that vary in quality; however, for temperate South America, there were no good (and readily available) field guides. Now, with the present work, one more piece of the jigsaw puzzle has been provid- ed— extremely well. The book sets out to be a field identification guide, so does not purport to provide infor- mation on such topics as nesting or ecology that might be expected in a more comprehen- sive type of handbook. It employs the user- friendly “facing-page” format; that is, the il- lustrations are on one page and the text and range-maps are on the facing page, saving the inconvenience of having to look in two places at once. The text and plates make up the bulk of the book’s 192 pages. There is a useful one- page introduction; four pages on how to use the book; three informative pages on Chilean habitats; worthwhile sections on migration, vagrancy, seabirds, field identification, and conservation; and a glossary. At the rear of the book is an excellent appendix on current taxonomic problems — which are numerous — and I am glad to note that the author is not afraid to admit that more work is needed to resolve these taxonomic issues. In the field-identification section, there is a brief general comment at the top of the page on the species or genera therein. Each species account includes a comprehensive section on identification and how to distinguish the spe- cies from similar-looking species, and notes about habitat, calls, and songs. The plates il- lustrate the most important features of each species; sexes and immature plumages are il- lustrated where necessary, as well as some distinctive races. Occasionally, little vignettes are included, illustrating such things as the feeding behavior of storm-petrels or close-ups of the bills of flamingoes. The book also pro- vides one of the best treatments that I have read on molt sequences in gulls, terns, and jaegers and how they affect identification; this information could be just as useful in North America as in Chile. Above all else, a field guide will be judged by the quality of its plates, and the plates in Birds of Chile are excellent. Having more than one artist contribute to a field guide often leads to an unsatisfactory final product, given differences in the styles and abilities of the artists; that is not the case here. Burke and Beadle have compatible styles, and the overall standard of the illustrations is very high. The format and size of the book limit the scope of the species accounts; nevertheless, all relevant details necessary for identification are given, and the book was obviously written by a field ornithologist for field ornithologists. Emphasis is given to truly useful field iden- tification features rather than details more ap- propriate for a museum collection. The com- bination of text and plates is superior to that of any other book presently and easily avail- able for the same geographic area. In addition to Chile, the book also covers the Falkland Islands, South Georgia, and the area of Chil- ean claims in Antarctica (which overlap with Argentinean and British claims — including the South Shetlands, the South Orkneys, and the Antarctic Peninsula). For other field guides, I have frequently been critical of the range maps, which often seem to be ill-considered afterthoughts with little regard for clarity or accuracy. This does not apply here. Admittedly, Chile — which is as narrow as 100 km in some places but has a latitudinal span equal to that between Wash- ington, D.C., and the mouth of the Amazon — presents a unique mapping problem that has been solved by splitting the maps into as many as three sections. This takes a little get- 322 ORNITHOLOGICAL LITERATURE 323 ting used to, but the maps convey the species’ ranges legibly and precisely. One rather pleasant feature of the book is the inclusion of local Spanish (or rather, Chil- ean) names for birds. This feature will be use- ful in talking to locals, who are frequently knowledgeable about local fauna but unfamil- iar with official names — just as a Newfound- land fisherman will look at you blankly when asked about Long-tailed Ducks (Clangula hyemalis) or Greater Shearwaters {Pujfinus gravis), but will tell you exactly where to find the “hounds” and the “hagdowners.” In fact, some of these local names are much more pic- turesque and poetic than the clumsy English- language equivalents. For example, the Wren- like Rushbird (Phleocryptes melanops) is a “worker,” the White-tailed Kite (Elanus leu- curus) a “dancer,” the Groove-billed Ani (Crotophaga sulcirostris) (mysteriously) a “horse-killer,” and nightjars are “blind hens.” With names like these, who needs polysyllab- ic and humorless official versions anyway? The book contains a few errors, the most blatant being much missing text (at least in my copy) in the account on the Juan Fernan- dez Firecrown (Sephanoides fernandensis), undoubtedly due to someone inadvertently pressing the delete key. A determined nit- picker could list a few more errors; however, the function of a reviewer is to give an overall appraisal of the success or failure of a work rather than to zero in on trivia (the missing text on the firecrown can be obtained at www.birdsofchile.com/errata.htm), and I find that the Birds of Chile is an excellent addition to the literature on South American birds. Not only will it be essential to anyone visiting this “skinny little country” (to quote the author), it will also be extremely useful to visitors of nearby countries for which there are no good field guides — notably Argentina and, to a less- er extent, Bolivia. With this in mind, the pre- sent work would have proven more useful if it had provided the non-Chilean ranges of spe- cies. This could have been done in a concise and abbreviated format without adding signif- icantly to the length of the text. Apart from this minor quibble, the author, artists, and pub- lishers have produced a field guide of superior quality and reasonable price. They are to be commended for a job well done. — DAVID BREWER, Puslinch, Ontario, Canada; e-mail: mbrewer@albedo.net PENGUINS: LIVING IN TWO WORLDS. By Lloyd S. Davis and Martin Renner, illus- trated by Sarah Wroot. Yale University Press, New Haven, Connecticut, 2004: 200 pp. + xii, 8 color plates, 28 line drawings, 20 black and white photos, 27 graphs, 7 tables. ISBN: 0300102771. $40 (cloth). — One of two major themes in this book is that penguins must be like fish because they spend most of their lives at sea; but because they are birds and therefore lay eggs, they must also have attributes that allow a terrestrial existence while breeding. Throughout the text, then, the authors describe the specializations and compromises involved in this bimodal lifestyle. Such is the lifestyle of all seabirds to greater or lesser degrees, but the penguins have exploited the aqueous en- vironment like no other group of extant avian species, with the exception of loons and grebes. However, as the authors point out in a chapter on evolution, the penguins stand alone in their adaptations to swimming and diving among the several families that are flightless. The book’s other major theme revolves around the dichotomy in natural history pat- terns that exists between inshore and offshore foragers. I have always been annoyed at the use of such terms in the literature on seabirds or other marine taxa because these terms lack substance and are confusing in this context. For example, I have seen them used in habitat descriptions of Antarctic krill (Euphausia su- perha). What Davis and Renner really mean is that some species of penguins forage close to penguin colonies and others forage farther away — the cutoff for their purposes being 50 km. The terms inshore and offshore connote habitat rather than distance. If authors mean distance traveled during foraging — and 1 just reviewed a paper that used 40 km to distin- guish inshore from offshore locations — then they should say so (i.e., short- versus long- distance foragers). If they want to connote for- aging habitat, then the appropriate terminolo- gy would be neritic versus pelagic, with the continental slope being a transitional habitat that lies between them. Treating this termi- nology with more rigor has become even more 324 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 critical these days as, following the lead of Henri Weimirskirch and others, more and more researchers are evaluating the distance and duration of foraging trips to determine whether parents are foraging more for them- selves or more for their offspring relative to their own energetic state or condition. The inshore versus offshore dichotomy elaborates on the theme that Davis, along with J. P. Croxall, had emphasized in a summary paper presented at the Third International Symposium on Penguin Biology (Croxall and Davis. 1999. Penguins: paradoxes and pat- terns. Marine Ornithology 27:1-12). In the present volume, the authors cite Croxall and Davis’ paper several dozen, and perhaps as many as 100, times. I definitely agree with their line of thought — that there is a distinct divergence in the natural history patterns of penguin species that are sedentary and forage close to the colony year-round versus species that are seasonally migratory and travel long distances to forage during breeding (Ainley et al. 1983. Breeding Biology of the Adelie Pen- guin. University of California Press, Berke- ley). The present volume certainly presents the topics a reader might expect from a book about penguins. Penguin Evolution (taxonom- ic placement depending on method of analy- sis); Penguins Today (thumbnail sketches of the existing species); Living in Two Worlds (mostly examples of the different life-history patterns of short- versus long-distance forag- ers); A Place to Breed (nest selection and hab- itat); Mate Selection and Courtship', Parental Investment (includes physiology of breeding, mate coordination); Moult and Migration', and Conservation (the majority of the world’s pen- guin species are in jeopardy). What the reader will find, however, is not a review of the vast penguin literature; rather it is a thorough re- view and integration of Lloyd Davis’ past 25 years of research and that of his students — Martin Remmer (the second author) being one of them. This is great, as Davis’ research — mainly on behavioral and physiological as- pects of penguin natural history (his forte, mostly to be found in chapters 6 and 7) — has been marvelously creative, and he has in- spired his students to be likewise. Many of his students’ theses have remained unpublished, which is not unusual, but, combined with his own research, their body of work has greatly advanced our understanding of penguin biol- ogy. With this book, we have it all integrated in one volume. Moreover, this is not just a review; the text advances new ideas as well. Of course, the content of books almost never reaches electronic databases, which means that one downside to Davis and Renner’s ap- proach is that some of the ideas in their book may languish for a long time before being re- discovered by particularly erudite students of penguin biology. One warning to prospective readers: al- though the writing is somewhat “folksy” in places, the fact that the authors present new ideas and interpretations — as well as the ar- gumentative nature of some of their points (they take exception to how others have in- terpreted certain issues) — means that this book is not a quick read. Rather, be prepared to take the time to consider their points versus what has been said elsewhere in the penguin literature. For people who are serious about scratching below the surface of information on penguin biology, I definitely recommend this book.— DAVID AINLEY, HT Harvey and Associates, San Jose, California; e-mail: dainley@penguinscience.com LOOKING FOR MR. GILBERT: THE RE- IMAGINED LIFE OF AN AFRICAN AMERICAN. By John H. Mitchell. Shoemak- er & Hoard, Washington, D.C. 2005: 280 pp., 16 black-and-white photographs. ISBN: 1593760264. $26 (cloth).— At first glance, this book does not seem a likely candidate for review in an ornithological journal, but the story has links to ornithology that those with an interest in the history of ornithology should find noteworthy. The book relates the histor- ical sleuthing of the author in an attempt to recreate the life of an African American, Rob- ert Alexander Gilbert, who lived from 1869 to 1942. For 24 years, Gilbert was the manser- vant and field companion of William Brew- ster, a major figure in the founding of the Nut- tall Ornithological Club and the American Or- nithologists’ Union. The author discovered about 2,000 photographic glass plate nega- tives (mostly of New England scenery) in the attic of the offices of the Massachusetts Au- ORNITHOLOGICAL LITERATURE 325 dubon Society that were attributed to William Brewster, the society’s first president. The au- thor came to believe that these photographs, taken between 1888 and 1917, were mostly the work of Brewster’s servant, Robert Gil- bert. Intrigued by his findings, the author searched archives and interviewed people from the Museum of Comparative Zoology (MCZ) at Harvard University, and even trav- eled to Paris, France, in an attempt to redis- cover and reconstruct the life of Gilbert. Born in Virginia, Gilbert had moved to Boston and, at age 27, was hired by Brew- ster— a wealthy Boston Brahmin whose pas- sion was ornithology — to help him set up his private museum in Cambridge. Gilbert was very bright and learned ornithology quickly; he became Brewster’s chauffer, mechanic, photographer, bird spotter, bird skinner, and general ornithological aid for the next 24 years until Brewster’s death in 1919. Brewster bequeathed his large collection of bird skins to the MCZ, and Gilbert became an assistant curator there, a job he held off and on for the remainder of his life. He became the chef for MCZ Director Thomas Barbour’s famous “Eateria,” a daily luncheon at the museum, visited by notables and featuring such exotic fare as elephant’s-foot stew. Gilbert accompanied Brewster on his pere- grinations from October Farm on the Concord River to Lake Umbagog in Maine and, on sev- eral occasions, to Europe. In later years, Gil- bert contributed bird records and observations of behavior to Brewster that were eventually incorporated in Brewster’s four-volume set Birds of the Lake Umbagog Region of Maine. While reading the extensive Brewster Journals and other archival materials, the author un- earthed some fascinating bits about Louis and Alexander Agassiz, Thomas Barbour, and Barbour’s predecessor at the MCZ, Samuel Henshaw, and he quotes conversations with notables, including one with Ernst Mayr. Most of the book deals with facets of Gil- bert’s life that were non-ornithological, in- cluding the racism encountered by African Americans in the late 19th and early 20th cen- turies. The author paints a convincing picture of life in a bygone era, providing biographical information on the life and times of William Brewster. The book is beautifully written and poignant. The book is not without errors, how- ever: Richard Paynter at the MCZ should be Raymond A. Payntor, Jr., and the Nuttall Club did not change the name of its Bulletin to The Auk — that occurred after the Nuttall Club had handed over the subscriber list to the fledgling American Ornithologists’ Union. This book is an interesting read, and although it is without references — and, as the subtitle “Reimagined Life” suggests, incorporates a great deal of supposition — it is nevertheless an interesting contribution to the history of American orni- thology.—WILLIAM E. DAVIS, JR., Boston University, Boston, Massachusetts; e-mail: wedavis@bu.edu HUMMINGBIRDS OF NORTH AMERI- CA. By Sheri Williamson and John W. Van- derpoel. Peregrine Video Productions, Niwot, Colorado. 2004: 178 minutes. VHS $34.95, DVD $39.95. — This video is the third in the Advanced Birding Series by Peregrine Video Productions, following the two videos on gull identification. The format will be familiar to those who have seen the gull videos, with Jon Dunn providing the narration and acting as a personal guide throughout the video. I partic- ularly enjoyed Jon’s asides on such subjects as how the vocalizations of an Anna’s Hum- mingbird (Calypte anna) sound like a “famil- iar” typewriter to him — before he acknowl- edges that the typewriter is not as familiar as it once was. The identification information is commensurate with that presented in the gull videos, although the editing and overall pre- sentation of the information is perhaps more polished. The video begins with introductory material on watching hummingbirds, identifying hum- mingbirds, and documenting rarities. Those who want a pretty video with lots of exquisite footage of hummingbirds will be only partial- ly satisfied with this tape. While the video is generally of extremely high quality, the focus is not on a celebration of these feathered jew- els, but on the skills and knowledge needed to enable the observer to identify them in the field, which leads to technical discussions of feather shapes, primary width, and the like, riic video is shipped with an insert that shows the topography of a hummingbird aFid defines some general terms, fhe insert also lists the 326 THE WILSON BULLETIN • Vol. 117, No. 3, September 2005 Starting time for each species covered, en- abling the viewer to select species of interest quickly. The film is also available on a DVD. Twenty-four species are covered in depth, with a brief mention of two additional spe- cies— Amethyst-throated {Latnpornis arne- thystmus) and Azure-crowned hummingbird {Amazilia cyanocephala) — that have not been documented in the U.S. or Canada. All breed- ing species of the U.S. and Canada are in- cluded. It is important to note that, although this video is titled Hutnmingbirds of North America, Mexico is not included. Non-breed- ing species include the Bumblebee Humming- bird (Atthis heloisa), Bahama Woodstar {Cal- liphlox evelynae), Cuban Emerald {Chloros- tilbon ricordii), Xantus’s (Hylocharis xantu- sii) and Cinnamon hummingbirds {Amazilia rutila). Green Violet-ear {Colibri thalassmus). Green-breasted Mango (Anthracothorax pre- vostii), and Plain-capped Starthroat {Helio- master constantii). The video categorizes hummingbirds into four large groups by gen- eral coloration (Rufous-Green and Gray- Green groups) or body size (Small Tropical and Large Hummingbird groups). The Ru- fous-Green and Gray-Green groups are further subdivided, thus leading viewers to the genus level — so necessary in hummingbird identifi- cation, particularly for birds in female and im- mature plumages. The video’s approach is straightforward, with a brief discussion of relevant character- istics for a given group or genus followed by detailed discussions of each species in the group. The species discussions include visual presentations of measurements, including weight, bill, and tail length. An animated map of each species’ geographical distribution and breeding and wintering ranges is presented, and extralimital records are mapped. For spe- cies breeding in the U.S. and Canada, the courtship-display dive is illustrated and the nesting chronology is described. This is fol- lowed by an overview of similar species and a discussion of vocalizations — including a sonogram of the calls — created by the Cornell Laboratory of Ornithology’s Raven software. The structure or “jizz” of each species is re- viewed, and then the plumage and character- istics of each age/sex class are discussed in some detail and compared with similar species or other age/sex classes, as needed. The quality of the footage of hummingbirds is nearly uniformly excellent. Some footage was selected that has distant or backlit birds to emphasize points about size or shape, but the identification footage is generally of high quality, with sharp, well-lit birds. Nearly all the footage is of wild hummingbirds; an ex- ception is video from the aviary at the Arizona Sonoran Desert Museum, used to illustrate, in particular, a female Lucifer Hummingbird {Calothorax lucifer). To me, it is preferable to use film of captive individuals if high quality footage of wild birds is not available. This video is highly recommended to any- one with an interest in learning more about hummingbird identification. It is not labeled as a beginner’s guide; however, birders using modem field guides and with an interest in learning more will find it a useful tool, al- though the depth of information presented may be intimidating initially. For advanced birders — the target audience for the series — this video will enhance their hummingbird identification skills and enjoyment when ob- serving hummingbirds. Ornithologists will find that the information on field identifica- tion of hummingbirds, including the details on age/sex classes, will increase the reliabil- ity of their identifications in the field. Band- ers will find tidbits to use as well; I know I did!— MARY GUSTAFSON, Patuxent Wild- life Research Center, Laurel Maryland; e-mail: MGustafson@usgs.gov This issue of The Wilson Bulletin was published on 14 September 2005. THE WILSON BULLETIN ditor JAMES A. SEDGWICK Editorial Board KATHY G. BEAL CLAIT E. BRAUN RICHARD N. CONNER KARL E. MILLER US. Geological Survey Fort Collins Science Center 2150 Centre Ave., Bldg. C. Fort Collins, CO 80256-8118, USA E-mail: wilsonbulletin@usgs.gov Review Editor MARY GUSTAFSON US. Geological Survey Patuxent Wildlife Research Center Laurel, MD 20708-4037, USA E-mail: WilsonBookReview @aol.com Index Editor KATHY G. BEAL Editorial Assistants M. BETH DILLON ALISON R. GOFFREDI CYNTHIA P. MELCHER GUIDELINES FOR AUTHORS Consult the detailed “Guidelines for Authors” found on the Wilson Ornithological Society Web site ^http://www.ummz. lsa.umich.edu/birds/wilsonbull.html). If your address changes, notify the Society immediately. Send your complete new address to Ornitho- logical Societies of North America, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. The permanent mailing address of the Wilson Ornithological Society is: % The Museum of Zoology, The Univ. of Michigan, Ann Arbor, MI 48109. Persons having business with any of the officers may address hem at their various addresses given on the inside of the front cover, and all matters pertaining to the Bulletin should be sent directly to the Editor. MEMBERSHIP INQUIRIES Membership inquiries should be sent to James L. Ingold, Dept, of Biological Sciences, Louisiana State Univ., Shreveport, LA 71115; e-mail: jingold@pilot.lsus.edu NOTICE OF CHANGE OF ADDRESS CONTENTS HOME-RANGE SIZE, RESPONSE TO FIRE, AND HABITAT PREFERENCES OF WINTERING HENSLOW’S SPARROWS - - - Catherine L. Bechtoldt and Philip C. Stouffer SPACING AND PHYSICAL HABITAT SELECTION PATTERNS OF PEREGRINE FALCONS IN CENTRAL WEST GREENLAND - - — - Catherine S. Wightman and Mark R. Fuller SURVIVAL AND CAUSES OF MORTALITY IN WINTERING SHARP-SHINNED HAWKS AND COOPER’S HAWKS - - Timothy C. Roth, II, Steven L. Lima, and William E. Vetter HABITAT USE BY RIPARIAN AND UPLAND BIRDS IN OLD-GROWTH COASTAL BRITISH COLUMBIA RAINFOREST - - - - - DENSITY AND DIVERSITY OF OVERWINTERING BIRDS IN MANAGED FIELD BORDERS IN MISSISSIPPI Mark D. Smith, Philip J. Barbour, L. Wes Burger, Jr, and Stephen J. Dinsmore COMPOSITION, ABUNDANCE, AND TIMING OF POST-BREEDING MIGRANT LANDBIRDS AT YAKUTAT ALASKA - — Brad A. Andres, Brian T Browne, and Diana L. Brann VARIATION IN INCUBATION PATTERNS OF RED-WINGED BLACKBIRDS NESTING AT LAGOONS AND PONDS IN EASTERN ONTARIO J Ryan Zimmerling and C Davison Ankney SEASONAL VARIATION IN ACTIVITY PATTERNS OF JUVENILE LILAC-CROWNED PARROTS IN TROPICAL DRY FOREST Alejandro Salinas-Melgoza and Katherine Renton PARROT NESTING IN SOUTHEASTERN PERU: SEASONAL PATTERNS AND KEYSTONE TREES Donald J. Brightsmith GROUP-SIZE EFFECTS AND PARENTAL INVESTMENT STRATEGIES DURING INCUBATION IN JOINT-NESTING TAIWAN YUHINAS {YUHINA BRUNNEICEPS) Hsiao- Wei Yuan, Sheng-Feng Shen, Kai-Yin Lin, and Pei-Fen Lee SHORT COMMUNICATIONS ROLLING PREY AND THE ACQUISITION OF AERIAL FORAGING SKILLS IN NORTHERN MOCKINGBIRDS Joanna R. Vondrasek ABOVE-GROUND NESTING BY NORTHERN BOBWHITE — ___Theron M. Terhune, D. Clay Sisson, and H. Lee Stribling DIVORCE IN THE CANARY ISLANDS STONECHAT (SAXICOLA DACOTIAE) Juan Carlos Illera REGURGITATED MISTLETOE SEEDS IN THE NEST OF THE YELLOW-CROWNED TYRAN- NULET (TYRANNULUS ELATUS) - Peter A. Hosner ORNITHOLOGICAL LITERATURE 211 226 237 245 258 270 280 291 296 306 313 315 317 319 322 TbcWlsonBulkttn PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY VOL. 117, NO. 4 DECEMBER 2005 PAGES 327-456 (ISSN 0043-5643) MCZ UBR^RY THE WILSON ORNITHOLOGICAL SOCIETY FOUNDED DECEMBER 3, 1888 Named after ALEXANDER WILSON, the first American Ornithologist. President — Doris J. Watt, Dept, of Biology, Saint Mary’s College, Notre Dame, IN 46556, USA; e-mail: dwatt@saintmarys.edu First Vice-President — James D. Rising, Dept, of Zoology, Univ. of Toronto, Toronto, ON M5S 3G5, Canada; e-mail: rising@zoo.utoronto.ca Second Vice-President — E. Dale Kennedy, Biology Dept., Albion College, Albion, MI 49224, USA; e-mail: dkennedy@albion.edu Editor— James A. Sedgwick, US. Geological Survey, Fort Collins Science Center, 2150 Centre Ave., Bldg. C, Fort Collins, CO 80526, USA; e-mail: wilsonbulletin@usgs.gov Secretary— Sara R. Morris, Dept, of Biology, Canisius College, Buffalo, NY 14208, USA; e-mail: 1 morriss@canisius.edu ' Treasurer— Melinda M. Clark, 52684 Highland Dr., South Bend, IN 46635, USA; e-mail: MClark@tcservices.biz i Elected Council Members — Robert C. Beason, Mary Gustafson, and Timothy O’Connell (terms expire ^ 2006); Mary Bomberger Brown, Robert L. Curry, and James R. Hill, III (terms expire 2007); Kathy ' G. Beal, Daniel Klem, Jr., and Douglas W. White (terms expire 2008). Membership dues per calendar year are: Active, $21.00; Student, $15.00; Family, $25.00; Sustaining, $30.00; Life memberships $500 (payable in four installments). The Wilson Bulletin is sent to all members not in arrears for dues. THE JOSSELYN VAN TYNE MEMORIAL LIBRARY The Josselyn Van Tyne Memorial Library of the Wilson Ornithological Society, housed in the Univ. of Michigan Museum of Zoology, was established in concurrence with the Univ. of Michigan in 1930. Until 1947 the Library was maintained entirely by gifts and bequests of books, reprints, and ornithological mag- azines from members and friends of the Society. Two members have generously established a fund for the purchase of new books; members and friends are invited to maintain the fund by regular contribution. The ftmd will be administered by the Library Committee. Terry L. Root, Univ. of Michigan, is Chairman of the Committee. The Library currently receives over 200 periodicals as gifts and in exchange for The Wilson Bulletin. For information on the library and our holdings, see the Society’s web page at http://www.ummz.lsa.umich.edu/birds/wos.html. With the usual exception of rare books, any item in the Library may be borrowed by members of the Society and will be sent prepaid (by the Univ. of Michigan) to any address in the United States, its possessions, or Canada. Return postage is paid by the borrower. Inquiries and requests by borrowers, as well as gifts of books, pamphlets, reprints, and magazines, should be addressed to: Josselyn Van Tyne Memorial Library, Museum of Zoology, The Univ. of Michigan, 1 109 Geddes Ave., Ann Arbor, MI 48109-1079, USA. Contributions to the New Book Fund should be sent to the Treasurer. THE WILSON BULLETIN (ISSN 0043-5643) THE WILSON BULLETIN (ISSN 0043-5643) is published quarterly in March, June, September, and December by the Wilson Ornithological Society, 810 East 10th St., Lawrence, KS 66044-8897. The subscription price, both in the United States and elsewhere, is $40.00 per year. Periodicals postage paid at Lawrence, KS. POSTMASTER; Send address changes to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. All articles and communications for publications, books and publications for reviews should be addressed to the Editor. Exchanges should be addressed to The Josselyn Van Tyne Memorial Library, Museum of Zoology, Ann Arbor, Michigan 48109. Subscriptions, changes of address and claims for undelivered copies should be sent to OSNA, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. Phone: (254) 399-9636; e-mail: business@osnabirds.org. Back issues or single copies are avail- able for $12.00 each. Most back issues of the Bulletin are available and may be ordered from OSNA. Special prices will be quoted for quantity orders. All issues of The Wilson Bulletin published before 2000 are accessible on a free Web site at the Univ. of New Mexico library (http://elibrary.unm.edu/sora/). The site is fully searchable, and full-text reproduc- tions of all papers (including illustrations) are available as either PDF or DjVu files. © Copyright 2005 by the Wilson Ornithological Society Printed by Allen Press, Inc., Lawrence, Kansas 66044, U.S.A. 0 This paper meets the requirements of ANSI/NISO 239.48-1992 (Permanence of Paper). FRONTISPIECE. Ovenbirds (Seiurus aurocapilla) at the Hemlock Hill Biological Research Area in Pennsyl- vania avoid forest interior and occupy only regenerating forest edges. Eastern chipmunks {Tamias striatus), abundant in forest interior but nearly absent in Ovenbird territories at Hemlock Hill, appear to influence this atypical habitat selection — highlighting the importance of general, simple cues to habitat selection. Original painting (watercolor) by Don Radovich. THE WILSON BULLETIN A QUARTERLY JOURNAL OF ORNITHOLOGY Published by the Wilson Ornithological Society VOL. 117, NO. 4 December 2005 PAGES 327-456 Wilson Bulletin 1 17(4);327-335, 2005 PREDATION AND VARIATION IN BREEDING HABITAT USE IN THE OVENBIRD, WITH SPECIAL REFERENCE TO BREEDING HABITAT SELECTION IN NORTHWESTERN PENNSYLVANIA EUGENE S. MORTON* 2 ABSTRACT. — From 1971 through 2003, Ovenbirds (Seiurus aurocapilla) at the Hemlock Hill Biological Research Area in northwestern Pennsylvania never bred in forest interior. Instead, they exhibited atypical habitat selection for breeding by occupying regenerating forest edges. Pairs in 14 territories, the entire population, showed normal annual return rates and pairing rates compared with other studies. For this ground-foraging bird, other studies showed that deep soil litter is preferred — but at my study site, soil litter depth in Ovenbird-occupied areas was lower than that found in the unoccupied forest interior. During May, July, and August, songs played in forest interior to attract Ovenbirds to settle there were unsuccessful. I tested the hypothesis that eastern chipmunk (Tamias striatus) abundance influenced this atypical habitat selection. Chipmunks were nearly absent from Ovenbird territories, but were abundant in the forest interior. I discuss habitat selection in birds in relation to simple cues and relate this to variation in habitat selection and use found in Ovenbirds. Received 29 December 2004, accepted 9 August 2005. The Ovenbird {Seiurus aurocapilla) is a clas- sic example of a “forest interior” and “area sen- sitive” songbird (Frost 1916, Forman et al. 1976, Ambuel and Temple 1983, Kroodsma 1984, Gibbs and Faaborg 1990, Freemark and Collins 1992). In some areas, it avoids edge habitat altogether, irrespective of forest patch size (e.g., Missouri; Van Horn et al. 1995), but in other areas it does not appear to do so (e.g.. New Brunswick 1 Sabine et al. 1996], Saskatch- ewan (Mazerolle and Hobson 2(K)31). In areas where Ovenbirds do breed in both edge and for- est interior, edge-inhabiting birds often do poor- ly, suggesting that they are forced from pre- ferred habitat and are making the best of a bad situation. However, they do not always have poor success in edge (Table I). That Ovenbirds ' Migratory Bird Center. .Smithsonian Institution, National Zoological Park, Washington. DC’ 2()()()S. USA. ‘ Dept, of Biology, York Univ., Toronto, ON M3.I IP3, C'anada; e-mail; mortoneCoAi.edu may sometimes avoid forest interior and u.se only edge for breeding has not been previously reported. A species with a wide breeding distribution might show geographic differences in habitat preferences, because habitat selection and use by breeding birds is based upon a complex mix of ultimate and proximate forces (Lack 1971, Cody 1985, Hutto 1985, Jones 2001). The costs and benefits of using available hab- itats may be influenced by predation, nest site, or food (Hutto 1985). In addition, intraspecific competition may force birds into marginal habitat (Fretwell and Lucas 1970), obscuring relationships between habitat preference, qual- ity, and use. One would expect habitat use to vary if costs and benefits change geographi- cally, even if the cues indi\ iduals use in se- lecting habitat are simple (e.g.. a single ele- ment, such as light intensity, out of the mul- titude of features foimtl in complex natural habitats). CTies to habitat selection must he simple if 327 328 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 TABLE 1 . Regional variation in reproductive and pairing success of Ovenbirds in edge habitats versus forest interior in North America. Location Reproductive succe.ss^ Pairing success^ Reference Northern Missouri Lower Lower Van Horn et al. 1995 Central Missouri ?b No difference‘s Porneluzi and Faaborg 1999 Southern Indiana No difference 7 Eord et al. 2001 New Jersey 7 Lower Wander 1985 Northern Wisconsin No difference No difference Flaspohler et al. 2001 North-central Minnesota Lower 7 Manolis et al. 2002 Alberta No difference No difference Lambert and Hannon 2000 Southern Saskatchewan 7 Lower Bayne and Hobson 2001 Southern Saskatchewan 7 No difference Mazerolle and Hobson 2003 Northern New Hampshire No difference No difference King et al. 1996 Southern Ontario Lower Lower Burke and Nol 1998 Quebec/Ontario 7 No difference Villard et al. 1993 ^ Along forest edge (0-100 m) as compared with interior. No data. ^ P > 0.05, or as stated by authors. they are genetically grounded (Lack 1971, Partridge 1978). Laboratory studies of habitat- choice cues by naive birds have supported the ideas of both genetic basis and cue simplicity (Partridge 1974). Morton (1990) showed that nonbreeding female Hooded Warblers {Wil- sonia citrina) chose habitats with oblique trunks and branches, whereas males chose habitats with vertical structures, irrespective of vegetation height. Breeding habitat consists of a mix of these oblique and vertical habitat features (James 1971). Greenberg (1992) showed that both Swamp (Melospiza georgi- ana) and Song sparrows (M. melodia) choose habitat differing in a single cue, the presence of water, and that this cue was innate. Innate cues are one element in predicting settlement patterns and these are probably due to selec- tion over ultimate time scales. Proximate cues are more likely to involve individual assess- ment of costs. Predators, for example, can make otherwise suitable habitat unusable (Block and Brennan 1993). General habitat- selection cues may coexist with microhabitat cues, such as those important in avoiding nest predation (Martin 1998). These factors have not been well studied. Here, I report a study of habitat use by Ov- enbirds in northwestern Pennsylvania, where they use only edge habitat contiguous to ma- ture, deciduous forest-interior habitat. I show that this aberrant selection of breeding habitat appears to be influenced by predators, notably the eastern chipmunk {Tamias striatus). I also describe a playback experiment designed to attract Ovenbirds to settle in forest-interior habitat. My results, and those of others, show that habitat usage may vary across diverse geographic areas. METHODS Study area.—T\\& study took place at the 150-ha Hemlock Hill Biological Research Area (HHBRA), Crawford County, in north- western Pennsylvania (41° 46' N, 79° 56' W), which is characterized by mature beech {Fa- gus spp.), maple {Acer spp.), oak {Quercus spp.), hickory {Carya spp.), and hemlock {Tsuga spp.) forest (Fig. 1; see also Howlett and Stutchbury 1996). Elevations range from 305 to 396 m and the terrain is largely flat or gently sloping. HHBRA is situated in an area fragmented by agriculture. Total forest cover for the region (740 km^) was 39% (Fraser and Stutchbury 2004) and 63% within a radius of 2 km of HHBRA (Rush 2004). HHBRA is surrounded by roads, fallow and active agri- cultural fields, and second-growth forest from 20 to 45 years old. To facilitate the mapping of territories, the entire 150-ha research area was grid-marked at 50-m intervals with or- ange plastic stakes in the ground and yellow flagging on trees. Beginning in 1971, and an- nually thereafter, I censused the entire area for breeding Ovenbirds. Censuses were conducted from 1 May to 1 July by listening for singing males, often in conjunction with ongoing studies of other species (e.g., Stutchbury et al. Morton • PREDATION AND OVENBIRD BREEDING HABITAT 329 I ^ I 0 500 m FIG. I. Aerial photo of the Hemlock Hill Biological Research Area (HHBRA bortleretl in black) in lUMth- western Pennsylvania (41° 4' N. 79° 5' W), taken in April 1994. Dark areas are dominated by eastern hemlock canadensis): deciduous forest is light-colored because trees were not yet leafed out. Fhe entire Ovenbird population at the site (// ~ 14 pairs; territories depictetl by white ovals) occurs in edge habitat, fhe IS-ha scuig playback area, indicated by the tlashed oval, is in the interior of mature deciduous forest. path can be seen going through the playback area aiul continuing in a loop thiough the forest. The four Osenbird territories at the southern boundary abut a pavetl roatl bortlering HHBRA; there are hay liekls to the south (4 the road. No Ovenbirds have bred within the playback area o\er the past years ( 1971 through 2(H)3). 330 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 1994, Morton et al. 1998). Each year, 9-14 Ovenbird territories were detected at the same sites and only at forest edges (Fig. 1 ). To show differences in forest maturity, I established transects (50 m long) between two grid points to count and measure tree species and trunk diameters in Ovenbird territories {n — 10) and in areas not used by Ovenbirds {n = 7). All trees >5 cm diameter at breast height (dbh) and within 2 m of the transect line were tal- lied. Hypotheses. — The 33 years of censuses at HHBRA showed that Ovenbirds bred in edge habitat in preference to forest interior. During this time, not a single breeding territory was located within the forest interior. With this background, in 2001—2003, I studied use of edge habitat by Ovenbirds at HHBRA in more detail, with the goal of testing why they might avoid forest-interior habitat. I tested several hypotheses: (1) Ovenbirds at HHBRA are nonbreeding, non-pairing transients; (2) food abundance is greater in edge habitat than in forest interior; and (3) Ovenbirds avoid using habitat with dense populations of eastern chip- munk, a potential predator. I tested the first hypothesis by color band- ing all breeding males and mapping their ter- ritories each year. The pairing status of all males in the study area was assessed 5-10 times each year between late May and late June for the presence of mates. Returns by birds in subsequent years and acquiring mates and nesting would indicate that the Ovenbirds are not nonbreeding, non-pairing transients, but are breeders. To test hypothesis 2, in 2003 I sampled lit- ter depth on territories and compared those samples with random samples from the forest interior (unused habitat) following the proto- col of Burke and Nol (1998). Those authors found that litter depth is positively correlated with food abundance for Ovenbirds, a ground- foraging species. I sampled litter depth at 10- m intervals along nine 50-m transects between grid points, six of which encompassed Oven- bird territories and three of which — randomly chosen — crossed forest-interior areas without breeding Ovenbirds. Chipmunks are common forest and edge in- habitants in the research area and are preda- tors on eggs, nestlings, and fledglings (Hill and Gates 1988, Reitsma et al. 1990, Fenske- Crawford and Niemi 1997, King et al. 1998, Maier and DeGraaf 2000, Zegers et al. 2000). To test hypothesis 3, whether Ovenbirds avoid areas with many chipmunks, I assessed chip- munk prevalence by walking to a randomly chosen grid point, either within or outside of an Ovenbird territory. Once positioned there, I sat quietly on a folding chair and after 2 min began recording the time it took to detect (hear or see) a chipmunk within a radius of 25 m during the next 10 min. If no chipmunk was detected, a time of 600 sec was recorded. All chipmunk surveys were conducted on sun- ny, warm days from 09:30 to 11:30 EDT in July of 2001 and 2003. On- and off-territory chipmunk detection trials were paired for date, weather, and time of day. All on-territory tri- als were conducted in forest-edge habitat be- cause there were no Ovenbird territories in the forest interior. Off-territory trials were either in forest interior within 200 m of an Ovenbird territory, or in an edge area unoccupied by Ovenbirds. Playback study. — I conducted daily dawn- to-dusk playbacks of Ovenbird songs to in- duce settlement by simulating territorial oc- cupation (Reed et al. 1999). A series of high- quality songs were recorded at normal singing cadence from one male breeding on the study site in 1985. Songs were played back contin- uously, except during heavy rains, from three Johnny Stewart Mini Wildlife Callers on 6- min TDK endless loop cassettes. Callers were located 100 m apart in the interior of mature deciduous forest. The broadcast covered an area of 18 ha (Fig. 1), determined by mapping points at distances from the speakers where the playback could just be detected by a hu- man observer. The speaker locations were chosen because the mature forest surrounding them had no breeding Ovenbirds during the past 3 decades, and a trail allowed access. Speakers were placed 1 00 m apart, rather than randomly throughout the study area, because Ovenbird territories are clumped and a single, isolated speaker would not depict this normal situation. I conducted playback trials over two seasons. The first (16 July to 31 August 2001), consisted of 201 hr, 45 min of playback av- eraging 7 hr, 45 min per day and was designed to attract birds that were prospecting for ter- ritories for the next breeding season, spring 2002. The second series (24 April to 20 May Morton • PREDATION AND OVENBIRD BREEDING HABITAT 331 2003) ended when all traditional territories were filled and males were paired and nesting. This series consisted of 183 hr, 43 min of playback averaging 7 hr, 43 min per day, be- ginning at 06:00. Here, I wanted to see wheth- er spring migrants could be attracted to settle immediately for the 2003 breeding season. Two-hr surveys for Ovenbirds that may have settled in response to playbacks were con- ducted every other day during the territory ac- quisition period (5 May to mid-June) in 2002 and 2003. RESULTS Ovenbird reproductive and pairing success varies among regions and studies. Edge hab- itat may be used, but with less reproductive success than in forest interior; it may be avoided; or, there may be little difference in nesting and pairing success (Table 1). Only at HHBRA and surrounding areas have Oven- birds entirely avoided nesting in forest inte- rior. I will first describe the situation at HHBRA and then report on the hypotheses testing mentioned above. For 33 years, no Ovenbird territories oc- curred in the interior of the mature deciduous forest (Fig. 1). Instead, territories bordered roads, fields, and on one occasion in 2001, a large clearing for a gas well adjacent to a new clear-cut in the forest. Occupied areas were former agricultural fields abandoned in the 1950s and regrown with aspens (Populus ^ranclidentata and P. tremuloides), American elms (Ulmus americcma), and red maples {Acer nth rum). On the ten 50-m transects through Ovenbird territories, there was a mean of 4.4 tree spe- cies and 15.2 ± 5.9 SD individual trees that averaged 13.7 ± 1.0 cm in dbh. The seven transects in interior forest had a mean of 6.3 tree species and 15.5 ± 2.5 individual trees that averaged 18.9 ± 12.8 cm in dbh. Amer- ican beech {Pat>us americana), hop hornbeam {Ostrya carpinifo/ia), American hornbeam {Carpi Hits caroliuiaua), and northern red oak {Querciis horeaPis) were found only in the for- est-interior transects. transient versu.s breeding adults. — Annual return rates for banded males (// = 14 terri- tories) were 67% in 2002 and 627r in 2003, within the normal range of return rates for male Ovenbirds; 85% were after-sccond-ycar Territory EIG. 2. Mean litter depth along 50-m transects (sampled every 10 m) in six different Ovenbird terri- tories (1-6) and along three randomly placed forest- interior transects (a-c), northwestern Pennsylvania, 2003. (ASY) birds. During the 2001-2003 study pe- riod, most males (86%) were paired — also within the normal range for forest-interior nesting birds in other studies (reviewed in Sa- bine et al. 1996, Burke and Nol 2001). I did not obtain information on breeding success, but young fledged successfully from four of four nests that were found incidentally. It is clear that these edge-inhabiting Ovenbirds were not transients, but were breeding adults that also had high pairing success and return rates. Food ahundauce in edge habitat versus for- est interior. — Mean litter depth was lower in Ovenbird territories (1.64 cm ± 1.34) than it was in forest-interior habitat (3.17 cm ± 1.12; Mann-Whitney test, c = -4.95, P < O.OOl; Fig. 2). At HHBRA, litter depth in Ovenbird territories was less than that found on any ter- ritories in Ontario (Burke and Nol 1998); the same methods were usetl in both studies. In my forest-interior sample, litter depth (3.17 cm) was approximately the same as that found in Burke and Nol's (1998) most preferretl nesting sites in large forest tracts. Insofar as litter depth is associatetl with footl richness and nest-site preference in Ovenbirds (l^urke ijnd Nol 1998), we can reject the hypothesis that edge habitat at HHBRA offers more food 332 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 <30 30-120 120-240 240-360 360-480 480-600 Time to detect chipmunk (sec) LIG. 3. Time (sec) to detect a chipmunk in the forest interior, unoccupied by Ovenbirds (hatched bars, n = 28), compared with the time to detect a chipmunk within Ovenbird territories (black bars, n = 20), north- western Pennsylvania, July 2001 and 2003. The max- imum time allowed per point for chipmunk detection was 10 min. Chipmunks were rarely detected on Ov- enbird territories but were abundant in forest interior. and is more attractive to Ovenbirds than in- terior forest. Chipmunk populations on and ojf Ovenbird territories. — Chipmunk presence was much greater off Ovenbird territories for each of the 2 years and for both years combined (Mann- Whitney test, z = 4.87, P < 0.001; Fig. 3). The average time to detect a chipmunk was only 2.1 min outside of Ovenbird territories, and chipmunks were found on 97% of the off- territory surveys. On Ovenbird territories, chipmunks were detected during only 3 of 21 surveys (14%) and it took an average of 7.2 min to detect them. Low chipmunk presence was not characteristic of all edge habitats at HHBRA and most edge did not hold Ovenbird territories (Fig. 1). In edge habitat not occu- pied by Ovenbirds (;z = 5 surveys, randomly selected), it took an average of 66 sec to detect Chipmunks, similar to detection times in the forest-interior habitat unused by Ovenbirds. On one territory, occupied during 2001 and 2002, no chipmunks were observed in the 10- min surveys on it. This territory was unoc- cupied in 2003, and a survey then resulted in chipmunks detected in 5 min, 48 sec. Playback study to induce Ovenbird settle- ment in forest interior. — Neither the late-sum- mer nor the spring playbacks induced Oven- birds to establish territories in the 18-ha for- est-interior area (Fig. 1). Individuals were oc- casionally observed in the playback area during the spring playback series, but none sang or remained. Instead, territories were re- occupied in the traditional edge areas. DISCUSSION If one studied Ovenbirds only in north- western Pennsylvania, their habitat and behav- ior would be described as “forest edge; avoids mature interior forest!” This point highlights the need for assessing habitat use in many ar- eas throughout a species’ range. For 33 years, Ovenbirds at HHBRA and the surrounding area have not settled in the interior of mature deciduous forest, despite low Ovenbird den- sity and an abundance of what is usually con- sidered “preferred” interior habitat. Although atypical, it may indicate that Ovenbirds are using nonhabitat cues when making decisions about whether or not to settle. An attempt to use playbacks to stimulate Ovenbird settle- ment in their preferred habitat at HHBRA failed. Summer playbacks failed to attract prospecting birds to settle the next breeding season and spring playbacks failed to induce settlement as well — although lone individuals were seen near the active playback speakers on several occasions. The hypothesis that chipmunks — predators upon eggs, nestlings, and fledglings — deterred Ovenbirds from settling was supported. Chip- munks were nearly absent from Ovenbird ter- ritories during the 3-year study, but were abundant in the forest interior. It is possible that the Ovenbird territories at HHBRA are in edge habitats because some edge areas have low chipmunk numbers. If this is true, then the reasons for low chipmunk numbers should be perennial in the occupied edges; this ap- pears to be the case. Chipmunks require an extensive burrow system for food storage, winter survival, and reproduction, but all Ov- enbird-occupied edges were damp due to the presence of springs and poor drainage condi- tions; they also contained no large trees, whose root systems provide burrow support (Elliott 1978). In contrast, edges that support- ed chipmunk populations were drier and had large trees along former fence lines. Chip- munks are always common or abundant in our area (I have not recorded any year in which they were uncommon), perhaps due to the Morton • PREDATION AND OVENBIRD BREEDING HABITAT 333 abundance of both sugar {Acer saccharum) and red maples, trees that produce plentiful seed crops each year in fall and spring, re- spectively. Could chipmunks be involved in habitat choice by Ovenbirds? As ground nesters and foragers, Ovenbirds are both particularly vul- nerable to discovery by chipmunks and able to assess chipmunk density by directly en- countering them during foraging or nest-site searching. The fact that Ovenbirds have an unusually short nestling period (8 days; Hann 1937) suggests that this species is under in- tense predation pressure (Bosque and Bosque 1995). Ovenbirds probably use litter depth (Burke and Nol 1998), as influenced by edaphic conditions (Smith 1977, Gibbs and Faaborg 1990, Blake et al. 1994), as a cue. Perhaps these direct habitat cues can be over- shadowed by an assessment of chipmunk den- sity. If so, then Ovenbirds at HHBRA might eschew forest interior there, where chipmunks are perennially common to abundant (ESM pers. obs.). As well, Ovenbird avoidance of chipmunks might have influenced the failure of playbacks to stimulate Ovenbirds to settle in the mature forest playback site (assuming they would respond to playbacks in the ab- sence of chipmunks). Some other ground-nesting species vulner- able to chipmunk predation also appear to choose nest sites that are chipmunk-free. For example. Dark-eyed Juncos (Junco hyemalis) and Louisiana Waterthrushes (Seiurus mota- cilla) place their nests only in recesses of ver- tical root balls of fallen trees (ESM pers. obs.). On the other hand, some forest ground nesters, such as Canada Warbler (Wilsonia canadensis). Black-and-white Warbler (Mnio- tilta varia), and Hermit Thrush {Catharus gut- tatus), do not exhibit this possible chipmunk avoidance ploy in their nest placement and are potential, but absent, breeders at HHBRA (ESM pers. obs.). Forstmeier and Weiss (2004) showed that Dusky Warblers (Phyllos- copiis fiiscatus) exhibited adaptive plasticity in their nest-site selection. This tundra-inhab- iting species places nests in safer and higher positions, at the expense of better microcli- mate and access to food, when Siberian chip- munk {Tamias sihiricus) populations are high. Forstmeier and Weiss (2004) suggested that Dusky Warblers, although short lived, are ca- pable of assessing chipmunk numbers and se- lecting nests sites accordingly. The evidence presented here on the impor- tance of chipmunk activity precluding Oven- birds from settling suggests the need for fur- ther experimental work. Future experiments could entail ( 1 ) removing chipmunks and then trying to attract Ovenbirds using playbacks, or (2) enticing chipmunks to invade traditional Ovenbird territories through food provision- ing— and testing the prediction that Ovenbirds would no longer settle there. By altering chip- munk presence/absence, any definitive re- sponse in Ovenbird settlement would provide additional evidence that chipmunks afford cues to Ovenbirds when choosing nesting hab- itats. The importance of looking for general, sim- ple cues to habitat selection is clear. However, nearly all studies of habitat-selection cues have been of temperate zone birds whose ter- ritoriality coincides with reproduction. Ave- nues of habitat selection in tropical birds with yearlong territories, where biotic interactions are features of habitat requirements, await dis- covery. Mixed-species flocks or ant/acacia mutualisms are examples (Janzen 1969, Ter- borgh 1985, Marra and Remsen 1997, Stutch- bury and Morton 2001). Habitat studies of birds should proceed beyond general descrip- tions, such as “forest interior” or “area sen- sitive,” for these terms may constrain, rather than enhance, explanations of habitat use (Vil- lard 1998). ACKNOWLEDGMENTS This study was funded through a grant from the Christensen Foundation administered through the Con- servation and Research Center, National Zoological Park, Smithsonian Institution, and by the Friends of the National Zoo. P. Kappes helped search for Oven- birds in the playback area. B. J. M. Stutchbury and S. Rush provided helpful comments that improved the manuscript. LITERATURE CITED Ambuel, B. and S. a. Temple,. 1983. Area-dependent changes in the bird communities and vegetation of southern Wisconsin forests. Ecology 64:1057- 1068. Bayne, E. M. and K. A. Hobson. 2(K)1. Effects of edge habitat <^n pairing success of Ovenbirds: the importance of male age and floater behavior. Auk I 18:380-388. Bi.ake. .1. Ci., J. M. Amoskie. G. J. Niemi. and P. T. 334 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Collins. 1994. Annual variation in bird popula- tions of mixed conifer-northern hardwood forests. Condor 96:381-399. Block, W. M. and L. A. Brennan. 1993. The habitat concept in ornithology: theory and applications. Current Ornithology 11:35-91. Bosque, C. and M. T. Bosque. 1995. Nest predation as a selective factor in the evolution of develop- mental rates in altricial birds. American Naturalist 145:234-260. Burke, D. M. and E. Nol. 1998. Influence of food abundance, nest-site habitat, and forest fragmen- tation on breeding Ovenbirds. Auk 115:96-104. Burke, D. M. and E. Nol. 2001. Ratios and return rates of adult male Ovenbirds in contiguous and fragmented forests. Journal of Field Ornithology 72:433-438. Cody, M. L. 1985. Habitat selection in birds. Academ- ic Press, Orlando, Florida. Elliott, L. 1978. Social behavior and foraging ecol- ogy of the eastern chipmunk (Tamias striatus) in the Adirondack Mountains. Smithsonian Contri- butions to Zoology, no. 265. Fenske-Crawford, T. J. and G. J. Niemi. 1997. Pre- dation of artificial ground nests at two types of edges in a forest-dominated landscape. Condor 99: 14-24. Flaspohler, D. j., S. a. Temple, and R. N. Rosen- FiELD. 2001. Effects of forest edges on Ovenbird demography in a managed forest landscape. Con- servation Biology 15:173-183. Ford, T. B., D. E. Winslow, D. R. Whitehead, and M. A. Koukol. 2001. Reproductive success of forest-dependent songbirds near an agricultural corridor in south-central Indiana. Auk 118:864- 873. Forman, R. T, A. E. Galli, and C. F. Leck. 1976. Forest size and avian diversity in New Jersey woodlots with some land-use implications. Oec- ologia 26:1-8. Forstmeier, W. and I. Weiss. 2004. Adaptive plastic- ity in nest-site selection in response to changing predation risk. Oikos 104:487-499. Fraser, G. S. and B. J. M. Stutchbury. 2004. Area- sensitive forest birds move extensively among for- est patches. Biological Conservation 118:377- 387. Freemark, K. E. and B. Collins. 1992. Landscape ecology of birds breeding in temperate forest frag- ments. Pages 443-454 in Ecology and conserva- tion of Neotropical migrant landbirds (J. M. Ha- gen, III, and D. W. Johnston, Eds.). Smithsonian Institution Press, Washington, D.C. Fretwell, S. D. and H. L. Lucas. 1970. On territorial behavior and other factors influencing habitat dis- tribution in birds. Acta Biotheoretica 19:16-36. Frost, R. 1916. The Oven Bird. Page 9 in Mountain interval. Henry Holt and Company, New York. Gibbs, J. P. and J. Faaborg. 1990. Estimating the vi- ability of Ovenbirds and Kentucky Warbler pop- ulations in forest fragments. Conservation Biology 4:193-196. Greenberg, R. 1992. Innate response to a single hab- itat cue in Song and Swamp sparrows. Oecologia 92:299-300. Hann, H. W. 1937. Life history of the Ovenbird in southern Michigan. Wilson Bulletin 49:146-237. Hill, S. R. and J. E. Gates. 1988. Nesting ecology and microhabitat of the Eastern Phoebe in the cen- tral Appalachians. American Midland Naturalist 120:313-324. Howlett, j. S. and B. j. M. Stutchbury. 1996. Nest concealment and predation in Hooded Warblers: experimental removal of nest cover. Auk 113:1-9. Hutto, R. L. 1985. Habitat selection by nonbreeding, migratory land birds. Pages 455-476 in Habitat selection in birds (M. L. Cody, Ed.). Academic Press, Orlando, Florida. James, EC. 1971. Ordinations of habitat relationships among breeding birds. Wilson Bulletin 83:215- 236. Janzen, D. H. 1969. Birds and the ant X acacia inter- action in Central America, with notes on birds and other myrmecophytes. Condor 71:240-256. Jones, J. 2001. Habitat selection studies in avian ecol- ogy: a critical review. Auk 118:557-562. King, D. L, C. R. Griffin, and R. M. DeGraaf. 1996. Effects of clearcutting on habitat use and repro- ductive success of Ovenbirds in forested land- scapes. Conservation Biology 10:1380-1386. King, D. L, C. R. Griffin, and R. M. DeGraaf. 1998. Nest predator distribution among clearcut forest edge and forest interior in an extensively forested landscape. Forest Ecology and Management 104: 151-156. Kroodsma, R. L. 1984. Effect of edge on breeding forest bird species. Wilson Bulletin 96:426—436. Lack, D. L. 1971. Ecological isolation in birds. Black- well Scientific, Oxford, United Kingdom. Lambert, J. D. and S. J. Hannon. 2000. Short-term effects of timber harvest on abundance, territory characteristics, and pairing success of Ovenbirds in riparian buffer strips. Auk 117:687-698. Maier, T. j. and R. M. DeGraaf. 2000. Rhodamine- injected eggs to photographically identify small nest-predators. Journal of Field Ornithology 71: 694-701. Manolis, j. C., D. E. Anderson, and F. J. Cuthbert. 2002. Edge effect on nesting success of ground nesting birds near regenerating clearcuts in a for- est-dominated landscape. Auk 119:955-970. Marra, P. P. and j. V. Remsen. 1997. Insights into the maintenance of high species diversity in the Neo- tropics: habitat selection and foraging behavior in understory birds of tropical and temperate forests. Ornithological Monographs 48:445-483. Martin, T. E. 1998. Are microhabitat preferences of coexisting species under selection and adaptive? Ecology 79:656-670. Mazerolle, D. F. and K. A. Hobson. 2003. Do Ov- enbirds (Seiurus aurocapillus) avoid boreal forest Morton • PREDATION AND OVENBIRD BREEDING HABITAT 335 edges? A spatiotemporal analysis in an agricultur- al landscape. Auk 120:152-162. Morton, E. S. 1990. Habitat segregation by sex in the Hooded Warbler: experiments of proximate cau- sation and discussion of its evolution. American Naturalist 135:319-333. Morton, E. S., B. J. M. Stutchbury, J. S. Howlett, AND W. Piper. 1998. Genetic monogamy in Blue- headed Vireos, and a comparison with a sympatric vireo with extrapair paternity. Behavioral Ecology 9:515-524. Partridge, L. 1974. Habitat selection in titmice. Na- ture 247:573-574. Partridge, L. 1978. Habitat selection. Pages 351-376 in Behavioural ecology: an evolutionary approach (J. R. Krebs and N B. Davies, Eds.). Blackwell Scientific, Oxford, United Kingdom. PoRNELUZi, P. A. AND J. Eaaborg. 1999. Scason-long fecundity, survival, and viability of Ovenbirds in fragmented and unfragmented landscapes. Con- servation Biology 13:1151-1161. Reed, J. M., T. Boulinier, E. Danchin, and L. W. Oring. 1999. Informed dispersal: prospecting by birds for breeding sites. Current Ornithology 15: 189-259. Reitsma, L. R., R. T. Holmes, and T. W. Sherry. 1990. Effects of removal of red squirrels, Tamia- sciurus hudsonicus, and eastern chipmunks, Tam- ias striatus, on nest predation in a northern hard- wood forest: an artificial nest experiment. Oikos 57:375-380. Rush, S. 2004. The effects of forest fragmentation on post-fledging survival and dispersal in a forest songbird. M.Sc. dissertation, York University, To- ronto, Ontario, Canada. Sabine, D. L., A. H. Boer, and W. B. Ballard. 1996. Impacts of habitat fragmentation on pairing suc- cess of male Ovenbirds, Seiurus aurocapillus, in southern New Brunswick. Canadian Eield-Natu- ralist 110:688-693. Smith, K. G. 1977. Distribution of summer birds along a forest moisture gradient in an Ozark watershed. Ecology 58:810-819. Stutchbury, B. J. M. and E. S. Morton. 2001. Be- havioral ecology of tropical birds. Academic Press, London, United Kingdom. Stutchbury, B. J., J. M. Rhymer, and E. S. Morton. 1994. Extra-pair paternity in Hooded Warblers. Behavioral Ecology 5:384-392. Terborgh, j. 1985. Habitat selection in Amazonian birds. Pages 311-338 in Habitat selection in birds (M. L. Cody, Ed.). Academic Press, Orlando, Florida. Van Horn, M. A., R. M. Gentry, and J. Eaaborg. 1995. Patterns of Ovenbird {Seiurus aurocapillus) pairing success in Missouri forest tracts. Auk 112: 98-106. ViLLARD, M.-A. 1998. On forest-interior species, edge avoidance, area sensitivity, and dogmas in avian conservation. Auk 115:801-805. ViLLARD, M.-A., P. R. Martin, and C. G. Drummond. 1993. Habitat fragmentation and pairing success in the Ovenbird {Seiurus aurocapillus). Auk 110: 759-768. Wander, S. A. 1985. Comparative breeding biology of the Ovenbirds in large vs. fragmented forests: implications for the conservation of Neotropical migrant birds. Ph.D. dissertation, Rutgers Univer- sity, New Brunswick, New Jersey. Zegers, D. a., S. May, and L. J. Goodrich. 2000. Identification of nest predators at farm/forest edge and forest interior sites. Journal of Field Orni- thology 71:207-216. Wilson Bulletin 1 17(4 ):336— 340, 2005 AVIAN FRUGIVORY ON A GAP-SPECIALIST, THE RED ELDERBERRY (SAMBUCUS RACEMOSA) BRIDGET J. M. STUTCHBURY.'^ BIANCA CAPUAXO.' .AND GAIL S. FRASERS ABSTR.A.CT. — In the temperate zone, few plants produce fruit during the peak of the avian breeding season when arthropods are abundant. This study examined avian frugivory on red elderberry (Sambucus racemosa pubens). a gap-specialist that fruits in late June and early July. First, we videotaped fruiting elderberry plants {n = 67 hr) within a forest to determine which avian species ate elderberry fruit. The birds that fed most frequently on red elderberry fruits were Scarlet Tanagers (Piranga olivacea) and Rose-breasted Grosbeaks iPheucticus ludovicianus). We then analyzed radiotelemetry data for Scarlet Tanagers to determine ( 1 ) whether tanagers shifted their territories when elderberry was in fruit, and (2 ) whether tanagers traveled long distances off territory to visit fruiting elderberr\ . During the fruiting period, male tanagers shifted their home ranges and spent more time near elderberry bushes; however, they left their territories only 0.25 times per hr and moved an average of only 115 m during trips off territory. These results suggest that while tanagers do focus their activit>- near fruiting elderberry, they do not leave their territories regularly to find fruit. Received 23 November 2004, accepted 18 July 2005. In the temperate zone, few plants produce fruit during the avian breeding season (Thompson and Willson 1979. \Mieelwright 1988). and the typical pattern is for temperate zone plants to fruit in late summer and early fall (Morton 1973). Only a small fraction of the breeding bird community is even partly frugivorous. largely because of the high abun- dance and protein content of anhropods (al- though we note that many insectivorous mi- grants do eat fruit in the nonbreeding season). Little is known about the imponance of fruit to temperate breeding birds (McCarty et al. 2002). or about the movements of territorial bird species in response to early-fruiting plants (Gorchov 1988). Red elderberry {Sambucus racemosa pub- ens). ty pically found in forest gaps, is among the earliest woody plants to fruit in the north- eastern region of the United States (Stiles 1980) and is available to forest birds while they are still nesting. In this smdy. we vid- eotaped ripe elderberry shrubs to quantify- which avian species fed on elderberry fruit and the rate at which plants were visited. We also analyzed radiotelemetry movements of one key species that eats elderberry, the Scar- let Tanager {Piranga olivacea) — to determine whether it shifts its territory use in response Dept, of Biology. York Univ., Toronto. ON M3J 1P3. Canada. - Faculty of Environmental Smdies. York Univ.. To- ronto. ON M3J 1P3, Canada. -Corresponding author; e-mail; bsmtch@yorku.ca to fruiting elderberry or makes long distance movements off territory in search of fruit. METHODS Study area. — From 2000 to 2003. we stud- ied avian frugivory on red elderberry at the Hemlock Hill Biological Research Area (41“ 46' X, 79“ 56' W). a 150-ha mixed forest in Crawford County, northwestern Pennsylvania. The fruiting period for elderberry was be- tween mid-June and mid-July, although indi- vidual plants were sometimes depleted of fruit within 7-10 days of ripening in mid- or late June. We searched the smdy site for elderber- ry plants and found 54 different plants (0.36/ ha) at 19 different sites (defined as >50 m apart: 0.13 sites/ha). Fruiting plants typically- had 20-50 clusters of fruit per plant (mean = 24. SD = 25.8. n = 49 plants), with about 200 individual fruits per cluster. Fruits are brilliant red. small (3-5 mm diameter; 0.05 g wet mass), and have a relatively high-energy- content (68.8 kcal/100 g: Usui et al. 1994). Bird visits and bird sun eys. — We selected medium- or large-sized elderberry plants for videotaping; for a subset of these plants, the mean number of fruit clusters was 46 (SD = 33. range = 8-105 clusters per plant. /? = 11 ). Some sites contained several adjacent elder- berry plants that were videotaped separately, but were considered the same site because presumably' the same individual birds fed on adjacent elderberry plants. We videotaped 14 different sites. 3 of which were taped in 2 dif- 336 Stutchbury et al • AVIAN FRUGIVORY ON RED ELDERBERRY 337 TABLE 1. The occurrence of videotaped species foraging on red elderberry fruit (n = 17 sites) from mid- June to mid-July in northwestern Pennsylvania, and the detection of those species (percentage of sites) during bird surveys in early July 2003 at elderberry sites (n = 14). Foraging observations are based on the percentage of sites at which the species was videotaped and percentage of all bird visits (ji = 106) to elderberry represented by that species. Elderberry foraging Sjjecies % sites % visits Bird surveys Scarlet Tanager {Piranga olivacea) 35.3 45.3 64% Rose-breasted Grosbeak (Pheucticus ludovicianus) 23.5 22.6 36% Red-eyed Vireo {Vireo olivaceus) 17.6 6.6 100% Veery {Catharus fuscescens) 17.6 7.5 50% American Robin {Turdus migratorius) 5.9 1.9 29% Wood Thrush {Hylocichla mustelina) 5.9 0.9 79% Northern Cardinal {Cardinalis cardinalis) 5.9 1.9 71% Gray Catbird {Dumetella carolinensis) 5.9 5.7 21% Eastern Towhee {Pipilo erythrophthalmus) 5.9 3.8 14% Downy Woodpecker {Picoides pubescens) 5.9 1.9 — Yellow-bellied Sapsucker (Sphyrapicus varius) 5.9 0.9 — Unidentified birds 29.4 8.5 ferent years, yielding a sample size of 17 sites. Video cameras (Sony Hi-8) were positioned so that most or all of one fruiting plant could be observed, and we collected 1-4 hr of tape per taping session depending on the weather and the camera’s capability. We videotaped plants between 09:00 and 17:00 EDT, only during dry weather. Tapes were later viewed on a television screen, and bird species were identified visually and/or by their call notes. We noted the time each bird spent foraging before departing from an elderberry plant. We could not accurately count the number of fruits eaten because our view of an individual was often blocked by vegetation as it foraged. To assess the abundance of frugivorous spe- cies relative to their visitation to elderberry, in 2003 we surveyed 14 elderberry sites for the presence or absence of frugivores. At each site where fruiting elderberry was present, we listened for singing birds within 50 m of the elderberry site for 10 min. We then played back 1 min of song, followed by 1 min of silence, for nine species of pas.serines that are partially frugivorous (Red-eyed Vireo, Wood Thrush, Veery, American Robin, Northern Cardinal, Scarlet Tanager, Rose-breasted Grosbeak, Gray Catbird, Eastern Towhee; see Table 1 for scientihc names). Surveys were conducted once during morning (09:00- 12:(K)), from 30 June to 3 July 2(X)3. Radiotelemetry'. — In 2000 and 2001, we captured tanagers by using a playback system. decoy, and mist nets and banded them with a federal band and a combination of individu- ally identifiable color bands. Males (n = 10) were fitted with a small (1.4 g), BD-2G radio transmitter (Holohil Systems, Carp, Ontario, Canada) that was attached with a figure-8 har- ness made of cotton embroidery thread (see Rappole and Tipton 1991). The transmitter and harness together weighed about 5% of adult body mass (30 g). Transmitter batteries lasted 8 weeks and the range was approxi- mately 1.5 km. The study site had conspicu- ous grid marks every 50 m and the locations of males were recorded by noting the closest grid mark(s) whenever the bird moved. Move- ments off territory were defined as occurring when a male entered another male’s territory (for known boundaries) or when males moved at least 100 m away from their own territory boundary. Tanagers were tracked between 1 3 May and 30 June to study off-territory movements (Fraser and Stutchbury 2004) and to compare movements before versus after elderberry fruit was ripe. We radio-tracked tanagers for about 2 hr at a time, between 06:()0 and 14:00, and followed males from a distance of about 30 m. Observations were not made during wet weather because the receiver was not water- proof. We mapped the location of all elder- berry shrubs in the territories of radio-tagged males, and quantified the relationship between territory size, movements, and fruiting shrubs. 338 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 We had a total of 116 hr of radio-tracking data — 46 hr during the pre-fruiting period (be- fore 15 June) and 70 hr during the fruiting period (15 June-30 June). We had a minimum of 6 hr of tracking time for each male used in our analyses. For seven males we used paired observa- tions (6 hr pre-fruiting, 6 hr fruiting) and pre- dicted that males would spend more time in an area with ripe elderberries than they would during the pre-fruiting period. We used two measurements during the pre-fruiting and fruiting periods to determine whether males were more likely to include ripe elderberry patches during their movements: (1) the per- cent time spent within 25 m of an elderberry shrub out of the total time tracked, and (2) the total number of elderberry shrubs contained within the male’s home range in each tracking session. Both comparisons were tested with a one-tailed, Wilcoxon paired signed-ranks test. RESULTS Birds that ate elderberry fruit. — From vid- eotapes, we identified 1 1 bird species and one eastern chipmunk (Tamias striatus) foraging on ripe elderberry (Table 1). We were unable to identify the bird species in only 8.5% of visits seen on the videotapes. The Scarlet Tan- ager was the species observed most often on elderberry plants; tanagers were seen at 35.3% of sites, and accounted for 45.3% of all bird visits to elderberry. The Rose-breasted Gros- beak was the second most common visitor to elderberry (22.6% of visits). The occurrence of a given species feeding on elderberry did not correspond closely to the species’ preva- lence— as assessed during our site surveys (Table 1). The percentage of sites visited (r^ = 0.275, n = 9, P = 0.24) and the percentage of visits {r^ = 0.05, n = 9, P = 0.45) were not significantly correlated with the percent- age of surveys on which the species was de- tected. For instance. Red-eyed Vireos and Northern Cardinals were very common birds at our study site (and responded readily to playback) but were rarely seen visiting elder- berry shrubs. In contrast, the low level of fru- givory by American Robins, Gray Catbirds, and Eastern Towhees likely did reflect the low abundance of these species in the forest. The Rose-breasted Grosbeak was often seen feed- ing on elderberry but was detected on only 36% of surveys, which may reflect a low de- tection ability for this species due to low song rates and weak responses to playback. The rate of visits by frugivores was highly variable between sites. For sites that were ob- served for at least 3 hr (n = 10), we observed no visits at three sites, <1 visit/hr at three sites, 1-5 visits/hr at two sites, and >5 visits/ hr at two sites. One elderberry plant was vis- ited by birds 29 times over a 3-hr period, al- though this plant did not have an unusually large amount of fruit (84 clusters). For 2003, when we estimated fruit crop, there was no correlation between the total number of fruit clusters per site and the visit rate/hr at that site (r, = 0.07, n = 1, P = 0.86). The average time spent on elderberry per visit was 59.4 sec (SD = 55.2, range = 5- 260 sec, n = 54 visits). Most birds consumed the small fruits while on the elderberry plant, although several species were occasionally observed feeding elderberries to their fledg- lings or departing with fruit in their bills (Scarlet Tanager, Rose-breasted Grosbeak, Veery, American Robin). Elderberry effect on tanager movements and territory use. — We radio-tracked seven paired males during both the pre-fruiting and fruiting periods to determine whether they shift their home-range use in response to the presence of ripe elderberry fruit. During the fruiting period, males spent significantly more time <25 m from elderberry (12.8% ± 0.14 SD) than they did during the pre-fruiting pe- riod (4.0% ± 0.075; Z = -1.99, n = 1, P = 0.023). There also was a strong but nonsig- nificant trend (Z = —1.47, n = 1 , P = 0.068) among males to shift their home ranges to in- clude more elderberry shrubs during the fruit- ing period (1.71 ± 1.5) compared with the pre-fruiting period (0.71 ± 0.76). Territory size (ha) did not change significantly between periods (pre-fruiting: 0.64 ± 0.27, fruiting: 0.94 ± 0.60; Z = -1.014, n = 7, F = 0.16). Eight of 10 males left their territories dur- ing the fruiting period, although the mean rate of off-territory forays was low (0.25 trips/hr ± 0.21 SD). In most cases, when males did leave their territories, they went only 115 m ± 124 (n = 8 trips) beyond their territory boundaries — roughly equivalent to the diam- eter of one tanager territory — and were not observed feeding on elderberry. We observed Stutchbury et al. • AVIAN FRUGIVORY ON RED ELDERBERRY 339 only one male travel far (300 m) off territory to an area of ripe elderberry. In the 70.2 hr of tracking during the fruiting period, we ob- served 2 of the 10 radio-tagged males forag- ing on elderberry. In both cases, their mates (not radio-tagged) also were observed forag- ing on berries. DISCUSSION We observed 1 1 different species of birds feeding on elderberry. Of 33 passerine species that regularly breed in the forest at this study site (BJMS pers. obs.), 9 species were ob- served feeding on fruit, and all were already known to be partially frugivorous during the breeding season. In some instances, we recorded high visi- tation rates to individual plants (10 visits/hr), but for most plants there were no, or only sev- eral, visits by birds each hour. Nevertheless, most plants were stripped of fruit by mid-July, suggesting that at some point birds (we as- sume) did consume the fruit. Denslow (1987) found that fruit removal rate (number of fruits removed per day) of red elderberry shrubs was significantly higher for isolated plants with large crops and for those with high sugar content in the fruit. We found no correlation between number of fruit clusters per site and bird visitation rate, although our sample sizes were modest. For instance, one site with nine different elderberry shrubs and 198 fruit clus- ters was not visited in 3.5 hr of observation. Another site had only a single elderberry plant with 84 fruit clusters, yet it was visited 9.6 times per hr. The occurrence of a given species foraging on elderberry did not closely correspond to its prevalence in the forest (Table 1). Wood Thrushes were rarely seen on elderberry shrubs, despite this species being detected at 80% of elderberry sites during bird censuses. Similarly, Red-eyed Vireos and Northern Car- dinals were present at most elderberry sites but represented only a small fraction of all bird visits to elderberry shrubs. The species- specific use of elderberry fruit could reflect differences in availability of insect prey to birds with different bill morphologies and for- aging substrates, and hence the relative value of the fruit at a time of year when many adults are feeding offspring. Almost half the visits to elderberry during our videotaping were made by Scarlet Tana- gers. Although male tanagers did not make long trips off territory to find fruit, they did spend more time near elderberry when it was ripe. However, stomach content analysis of forest thrushes revealed relatively low fruit content in June and July (White and Stiles 1990), and the same may be true for tanagers (Mowbray 1999). The low fruit content in the diet could reflect the low number of fruiting species available at that time of year and the low density of these plants. In our study area, the density of elderberry sites was only 0.13/ ha and many tanager pairs had no elderberry plants on their territories. We have observed tanagers feeding elderberries to older nestlings and fledglings, but it is not known whether feeding fruit to young increases the reproduc- tive success of the parents. Our results have implications for under- standing seed dispersal by this early-fruiting plant. One of the potential costs of early fruit- ing is limited seed dispersal due to territori- ality during the peak breeding season of birds (Morton 1973, Willson and Thompson 1982). However, Gorchov (1988) found that dispersal of one early-fruiting species, Amelanchier ar- borea, was not restricted by territoriality, be- cause the main avian disperser was the Cedar Waxwing (Bombycilla cedrorum), which for- ages in flocks. Our results suggest that dis- persal distance of red elderberry within a for- est may indeed be limited by territoriality be- cause male Scarlet Tanagers did not regularly commute off territory to search for fruit. Most of the birds that ate elderberry (Table 1 ) de- fend all-purpose territories and may be simi- larly constrained. Although male (and female) tanagers do often leave their territories after breeding (Vega Rivera et al. 2003), this occurs later in summer after the main fruiting period of red elderberry. Red elderberry is a gap-spe- cialist, but it is not necessarily disadvantaged by dispersal within a bird’s territory. What may be more important than distance per se is that the seeds are dispersed to a favorable site (e.g., Wenny and Levey 1998) — in this case, another gap within the territory — c:>r are dispersed to sites within the forest where they can wait for a gap to form above them. ACKNOWLEDGMENTS We thank Hemlock Hill Biological Research Area and all (he landowners for permission to conduct re- 340 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 search there. This project was funded by awards to BJMS from the Molson Foundation, the Premier’s Re- search Excellence Award, and the Natural Sciences and Engineering Research Council of Canada. K. J. Cooper, R. Norris, M. Ortwerth, and M. Williams all provided excellent field assistance. Special thanks go to M. Ortwerth and K. J. Cooper for their hard work. E. S. Morton, D. J. Levey, B. Woolfenden, and three anonymous reviewers provided comments on the man- uscript. LITERATURE CITED Denslow, j. S. 1987. Fruit removal rates from aggre- gated and isolated bushes of the red elderberry {Sambucus pubens). Canadian Journal of Botany 65:1229-1235. Fraser, G. S. and B. J. M. Stutchbury. 2004. Area- sensitive birds move extensively among forest patches. Biological Conservation 118:377-387. Gorchov, D. L. 1988. Does asynchronous fruit rip- ening avoid satiation of seed dispersers? A field test. Ecology 69:1545-1551. McCarty, J. R, D. J. Levey, C. H. Greenberg, and S. Sargent. 2002. Spatial and temporal variation in fruit use by wildlife in a forested landscape. Forest Ecology and Management 164:277-291. Morton, E. S. 1973. On the evolutionary advantages and disadvantages of fruit eating in tropical birds. American Naturalist 107:8-22. Mowbray, T. B. 1999. Scarlet Tanager {Piranga oli- vacea). The Birds of North America, no. 479. Rappole, j. H. and a. R. Tipton. 1991. New harness design for attachment of radio transmitters to small passerines. Journal of Field Ornithology 62: 335-337. Stiles, G. W. 1980. Patterns of fruit presentation and seed dispersal in bird-disseminated woody plants in the eastern deciduous forest. American Natu- ralist 116:670-688. Thompson, J. N. and M. F. Willson. 1979. Evolution of temperate bird/fruit interactions: phenological strategies. Evolution 33:973-982. Usui, M., Y. Kakuda, and P. G. Kevan. 1994. Com- position and energy values of wild fruits from the boreal forest of northern Ontario. Canadian Jour- nal of Plant Science 74:581-587. Vega Rivera, J. H., W. J. McShea, and J. H. Rappole. 2003. Comparison of breeding and postbreeding movements and habitat requirements for the Scar- let Tanager {Piranga olivacea). Auk 120:632- 644. Wenny, D. G. and D. j. Levey. 1998. Directed seed dispersal by bellbirds in a tropical cloud forest. Proceedings of the National Academy of Sciences USA 95:6204-6207. Wheelwright, N. T. 1988. Fruit-eating birds and bird- dispersed plants in the tropics and temperate zone. Trends in Ecology and Evolution 3:270-274. White, D. W. and E. W. Stiles. 1990. Co-occurrences of foods in stomachs and feces of fruit-eating birds. Condor 92:291-303. Willson, M. E and J. N. Thompson. 1982. Phenology and ecology of colour in bird-dispersed fruits, or why some fruits are red when they are “green.” Canadian Journal of Botany 60:701-713. Wilson Bulletin 1 17(4):341-352, 2005 BIRD COMMUNITIES AFTER BLOWDOWN IN A LATE-SUCCESSIONAL GREAT LAKES SPRUCE-FIR FOREST JOHN M. BURRISi 2 AND ALAN W. HANEYi ABSTRACT. — In 2001 and 2002, we inventoried the bird communities and vegetation of two 6.25-ha plots in a late-successional spruce-fir (Picea mariana-Abies balsamea) forest of northern Minnesota that was severely disturbed by a 1999 windstorm. We compared these results with those from two nearby plots that were largely unaffected by the storm. Using vegetation data collected from one of the two plots in each location before the disturbance in 1996 and 1998, we examined similarities between plots before and after the storm. The most significant effect of the storm on vegetation was a >80% decrease in tree cover and a >100% increase in shrub- layer structure because of trees that were tipped over or snapped off. Of 30 territorial bird species, 9 held territories exclusively in the blowdown, while 2 held territories exclusively in the control. By foraging guild, 10 of 1 1 (91%) species of ground-brush foragers had more territory cover in the blowdown, while 7 of 13 (54%) species of tree-foliage searchers had more territory cover in the control. Black-and-white Warbler (Mniotilta varia). Chestnut-sided Warbler (Dendroica pensylvanica). Mourning Warbler (Oporornis Philadelphia), Yellow- bellied Flycatcher (Empidonax flaviventris), and Red-eyed Vireo (Vireo olivaceus) had significantly {P < 0.05) more territory cover in the blowdown, whereas Blackburnian Warbler {Dendroica fusca). Golden-crowned King- let (Regulus satrapa), and Yellow-rumped Warbler {Dendroica coronata) had more territory cover in the control. Canonical correspondence analysis revealed that differences in avian territory cover were primarily attributable to changes in vegetation structure, in particular the increase of structural debris on the ground and the reduction in tree canopy, occurring because of the wind. Received 25 October 2004, accepted 30 August 2005. Forest composition and structure in the Up- per Great Lakes region is greatly influenced by disturbances, primarily fire, insect out- breaks, logging, and wind (Van Wagner and Methven 1978, Bonan and Shugart 1989, Ber- geron 1991, Drapeau et al. 2000). Although the most prevalent natural disturbances in this region are fire and insects, large-scale wind events that significantly reduce the canopy are believed to occur with average return intervals of 1,000 years or more (Frelich and Reich 1996, Larson and Waldron 2000, Frelich 2002). A number of studies have examined the effects of disturbances such as fire and logging on avian communities in the Upper Great Lakes region (Apfelbaum and Haney 1986, Schulte and Niemi 1998, Drapeau et al. 2000); however, despite its known impact on vegetation structure and composition (Frelich and Reich 1996), few researchers have ex- amined the effects of wind (Smith and Dall- man 1996, Dyer and Baird-Philip 1997). On 4 July 1999, a microburst — known as a derecho, and characterized by straight-line ' College of Natural Resources, Univ. of Wisconsin- Stevens Point, Stevens F’oint, W1 54481. USA. ^Corresponding author; e-mail: John.M.Burris@gmail.com winds in excess of 145 km/hr — disturbed ap- proximately 200,000 ha in northeastern Min- nesota (USDA Forest Service 2002). We doc- umented the effects of severe wind distur- bance by comparing post-disturbance vegeta- tion and bird communities on two blowdown plots with two nearby control plots that had the same disturbance history and vegetation structure before the storm. Because bird spe- cies composition is closely related to habitat structure (Karr and Roth 1971, Willson 1974, Niemi and Hanowski 1984, Pearman 2002), and because the wind reduced tree cover by more than 80%, with a corresponding increase in shrub-layer structure and coarse woody de- bris from tipped trees and snapped tree-tops, we expected a community shift from one dominated by tree-foliage searchers to one dominated by ground-brush foragers. We ex- pected responses similar to those following fire (Apfelbaum and Haney 1981, Morissette et al. 2002) and, in some cases, timber har- vesting (Hobson and Schieck 1999, Lohr et al. 2002). METHODS We conducted our study in a 200-ycar-old black spruce {Picea nuiriana) and balsam fir {Ahies balsamea) forest that originated from 341 342 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 an 1801 stand-replacing wildfire (M. L. Hein- selman pers. comm.) in northeastern Minne- sota’s Superior National Forest (Fig. 1). Two blowdown study plots were located on Seagull Lake (48° 07' N, 90° 54' W) and two control plots, minimally affected by the 4 July 1999 storm, were located near Red Rock Bay (Sa- ganaga Lake), approximately 10 km to the northwest of Seagull Lake. Each 250 X 250- m (6.25 ha) study plot, surrounded by a 25-m buffer zone to reduce the effects of edge, was subdivided with flagging into a grid of 50 X 50-m cells. Using previously collected data from one of the blowdown plots (1996) and one of the control plots (1998), we employed a BACI design (Before, After, Control, Im- pact; Stewart-Oaten et al. 1986, Irons et al. 2000, Stewart-Oaten and Bence 2001) to bet- ter illustrate similarities between plots before the disturbance, and changes occurring be- cause of the windstorm. We did not use a BACI design to analyze our bird data, how- ever, because the annual variation in bird pop- ulations is unpredictable (Blake et al. 1994, Collins 2001) and our pre-disturbance avian surveys were conducted in different years. Post-blowdown vegetation surveys were conducted in 2001 and again in 2002 along 50-m transects running through the center of 10 randomly selected grid cells in each of the four study plots (n = 4 plots/year X 10 cells/ plot X 2 years = 80). Using the same meth- odology, we surveyed vegetation in one of the pre-blowdown plots in 1996 and one of the control plots in 1998 (n = 2 plots X 10 cells/ plot = 20). Tree and shrub cover for each spe- cies were estimated using the line intercept method (Canfield 1941). Trees were defined as stems standing <45 degrees from vertical with a diameter at breast height (dbh) ^5 cm. Shrubs were identified as all stems >1 m tall and <5 cm dbh or as live trees standing >45 degrees from vertical. Dead trees were con- sidered coarse litter if standing >45 degrees from vertical and snags if standing <45 de- grees. After the storm, diameters of all stems >5 cm that crossed the 50-m intercept line were recorded and used to estimate the vol- ume of coarse woody debris per unit area. We estimated tree and shrub density by re- cording the number and diameter (rounded to the nearest 5 cm) of live and dead trees rooted within 1 m of either side of the transect and the number of live and dead shrub stems with- in 1 m of the right side of the transect. We used five 1-m^ circular plots centered at 5, 15, 25, 35, and 45 m along the transect line to estimate percent cover of herbs (height < 1 m), exposed mineral (e.g., rock, bare soil), bryo- phytes, coarse litter (diameter >5 cm), and fine litter (diameter <5 cm). We conducted bird surveys on each of the four plots once per morning for each of 5 days during May-mid-June 2001 and 2002. Sur- veys were performed using a modification of Kendeigh’s flush-plot techniques (Kendeigh 1944, Apfelbaum and Haney 1986). Each sur- vey was conducted by one or two experienced birders who plotted on data sheets all birds seen or heard from grid-cell vertices. Surveys, which were restricted to days without signif- icant wind or rain, averaged about 6 person- hr, each designed to plot every territorial male using the area. After the completion of all five daily sur- veys, bird locations for each plot were com- piled onto summary sheets. Territories were delineated from clusters of survey registra- tions and other evidence of established terri- tories, such as active nests, or adults carrying food or fecal sacs. We considered likely tran- sients, or individuals with territories too large to determine with our method, as visitors (V) unless they were recorded in the same location on at least 3 of the 5 survey days. Data analyses. — To address issues of spatial dependence within the vegetation dataset, we first eliminated repeatedly sampled grid cells while balancing sample sizes between years and plots. Of the 100 grid cells for which we had vegetation data, we retained 62 cells (10 pre-blowdown [1996], 10 pre-blowdown con- trol [1998], 12 post-blowdown [2001], 11 post-blowdown control [2001], 9 post-blow- down [2002], 10 post-blowdown control [2002]) for further analysis. Next, we exam- ined the resulting vegetation data for normal- ity (Q-Q plot and Shapiro-Wilk tests) and ho- mogeneity of variance (Levene’s test) and transformed data according to Box-Cox plots (Box and Cox 1964) as necessary. Finally, we used a two-way analysis of variance (ANO- VA) for each habitat variable {n = 19) to ex- amine differences based both on plot type (blowdown or control) and time (1996 or 1998, 2001, 2002). If the ANOVA yielded a Burris and Haney • BIRD COMMUNITIES AFTER BLOWDOWN 343 100 150 200 M Kilometers FIG. 1. Location of the study area and the blowdown area in northeastern Minnesota's Superior National Forest. The blowdown occurred 4 July 1999, a result of' a >145 km/hr microburst. 344 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 ^ -a ^ S 2 o ti ON (U T3 D LT O g s s ^ o o ^ o ^ O 3 s: ^ o .H ^ o-^ 03 c/3 H O ^ i s ^ i j; 2 8 n ■’“ " s ^ ^ B II II ^ ^ ■'3 B ^ Q c/3 > C/3 (U ^ S S §2'-g2 iilBo g|^ |£ § § S ts 8 ! 8 ° i s||S *= .5?^ II > " II t;? g ’S) § pQ “ 2i 'C flj 4; Oii - & - se w n o ^ S g o c ■o .£ o ^ S "2 3 w- J e h a c S o o 0 '03 £ > _ ^ o ^ ^ X3 3 ^ > 8 c/3 £ •c w jO c/3 -O -5 (U T3 O ^ O i> ^ > c i= Dh3^ s nx 00 T3 > c «a ^ o ^ ^ 2 O - 0 O ^ ^ Z .S o II " r- O (U H ^ ^-43 N ^ V > c2 ^ t+^ , ^ - u h W o cc T3 g X U pq - S C4-< C^ O C/3 !/i 5 (u J9 n ^ o o 3 s 00 i-H Or) c3 o ^ > ,0 (U c>v ^ i-^ c ^ (u o3 g o c s > “ « 8 = 8 O " 03 T3 ^ F c o r. c/3 ~ - cu o ^ C3 03 c/3 Vh ^ O c/3 w ”8 ^ i § ^ F c/D F 5+2 p Q ^1 _C j ■^is II 8| (U ^ o q ' o ^ C« ^ C/D 2 .^2 C/D 2 V (>3 c a 2 O , q .0 h > ^ F c ^ -E ^ '-6 ^ 5 O 52 _5 _ - .2 F I 8 F < ^ ^ -F o q 03 e P S S 2 § II I (U gq 2 2 (50 H 8 Q -Sr'H'lg# Srsi " ^ c" cc c (u U W ■£ S p . Pii l2 .2 ^ DC ^ "2 q "2 p p 00 CQ < «3 DuU Is Is X) n(NrOOs os'it-+osTi-NDr-rtt^ooos'-+‘noo P3 PQ * * * * nro-^(N'':t'^'-^-+'— (NOO +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 Nor-oo+tOsOsONr^foro»nmoooosOs'^'^oO‘no\'Omro>no ro csiON'^NOt^O(X)r^^(NinNOoor^cncon r4 n 0 d" 00 0 m 0 +t in 00 00 (M ''t (N 0 --H 0 (N 0 0 (N ON (N d d d d d d d d d d d d d d d V V 00 m cn Os so 00 m (N cn ON so (N 0 q +t os (N (N p Os p (N q q 0 q d d d d d d d d OS d ON d d O O 00 (N +t -p d d d 00 —I 00 p p p d d NO cn Os r- d d c T3 ■0 t ■0 T3 d ■0 •0 Q d *q JO *q Q T3 d .2 ii 0 pH q q q q q d d d d q g q q q d d d q 0 d d X X X q q q q u E X § (75 (75 (75 H H H u u u u u U U U U u u TABLE 1. Continued. Burris and Haney • BIRD COMMUNITIES AFTER BLOWDOWN 345 P3 c * * (N ON in NO ON in 0 0 o in 0° d + 1 +1 +1 + 1 +1 +1 +1 +1 0 q NO 00 q q 00 00 cu d 00 d in d d in in ^ < * * c r- 0 ON NO r- ON (N q on q q 00 T3 a |8 +1 d d +1 +1 q 00 +1 +1 d (N + 1 +1 +1 £ NO m 0 ON X (N — ^ (N 0 (N '-N C c C c a 0 o? 0 0 0- 0 c 0 T3 0 l§ If .2 § > 2 1 1 "O q U CQ U PQ U CQ U s 0 (n 0, 0 (N (N u E d d d d H V X IT) 0 0 k. q q q ri 06 00 (N m ON 0 (n 0. 0 0 0 0 d d d d < i> > E o z H < (N _ ? Li, 00 q ri r-' d d ■O’ vO q !!. r*'i d d d d r) -t '•C . 'I; ON rj d d oc ■3 £ ■3 c O ■u UJ DC (- < ■3 DC X DC W u Q C cn H SO sj ^ > UJ > > > Q — - O a, a o •o •5 O X) its i C ■? -O ■ - ^ v ■o E £ ill = C C ' ^22' ana ti t) # f ; £3 ra rj ^ Q Q Q t significant interaction, indicating that the blowdown and control plots were changing differently with time, we conducted main ef- fects analyses to examine both differences be- tween plot type in a given year and differenc- es between years within each plot type. To control for Type I error across the two simple main effects, we used a Bonferroni correction procedure (Winer et al. 1991) and set alpha for each simple main effect at 0.025. If the simple main effect (time) was significant, fol- low-up pairwise comparisons between 1996, 1998, 2001, and 2002 were performed using a Bonferroni-adjusted alpha set at 0.008 (0.025/3) to identify time periods of signifi- cant change. Because we wanted to correlate bird pres- ence with habitat characteristics, we analyzed our bird data at the same scale as the vege- tation data (50 X 50-m grid cell), rather than at the 250 X 250-m plot level. This was ac- complished by selecting 42 grid cells equally distributed by both year (2001, 2002) and plot between the blowdown and control plots. To mitigate issues of spatial dependence, we re- quired all of the selected cells within the same year to be a minimum of 50 m apart, and we did not select the same cell in successive years. So that we could later perform a joint analysis using both bird and vegetation data, we further required that selected grid cells were those for which we had also collected vegetation data in the same year. After cell selection, we recorded by species (based upon our territory maps) the percentage of each se- lected cell covered by a territory. For sum- mary purposes, species were assigned to for- aging guilds (e.g., tree-foliage searcher, timber gleaner) according to those described by Bock and Lynch (1970). Next, we tested these data for homogeneity of variance (Levene’s test) and used a one-way ANOVA to test for the effect of disturbance. Although somewhat un- conventional, distinguishing bird use by mea- suring the percentage of each cell covered by a territory allowed us to detect differences be- tween plots on a finer scale — an attribute we felt was required, given the patchiness of the landscape following the blowdown. We are aware that changes in both avian density (Huxley 1934, Wiens et al. 1985) and habitat (Gill and Wolf 1975, Smith and vShugart 1987) may affect territory size, but upon finding lit- 346 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 tie difference in average territory size between plot types (blowdown or control), we con- cluded that significant differences in territory cover per cell would likely be the result of more territories rather than territories of a larger size. In examining the relationship between hab- itat structure and bird species composition, we used only the 42 grid cells (21 blowdown, 21 control) from 2001 and 2002 for which we had both vegetation and bird data. First, we used a Pearson correlation matrix along with principal components analysis (PCA) to min- imize redundancy within the dataset, follow- ing the recommendations of ter Braak (1986, 1994) for subsequent canonical correspon- dence analysis (CCA). If ^2 variables were strongly correlated (r > 0.60) within the cor- relation matrix, we kept only the habitat var- iable most strongly correlated with the first principal component (i.e., the variable ex- plaining a greater amount of the variation within the data). Next, using the remaining variables (10 of 19), we performed PCA again to reduce the complexity of the dataset and summarize the habitat variables within the blowdown and control areas. Finally, we con- ducted CCA, performed by the PC-ORD sta- tistical package (McCune and Mefford 1999), on the 10 selected habitat variables and 15 common bird species (those with territory cover in at least 10% of the 42 grid cells) to investigate more closely the relationship be- tween habitat characteristics and the distribu- tion of bird species. To determine the signifi- cance level of this relationship (ter Braak 1987), the CCA included a Monte Carlo test on the first two canonical functions, conducted with 1 ,000 permutations and using time of day as the source for randomization. Means are presented ± SE. RESULTS Twenty-six percent (5 of 19) of the habitat variables examined in the blowdown were sig- nificantly different after the storm in 2001 or 2002 when compared with pre-storm esti- mates collected in 1996 (Table 1). In contrast, there were no significant differences in habitat variables between years (1998, 2001, 2002) in the control. Percent tree cover (CTREE), which was somewhat higher in the to-be dis- turbed area before the storm (control: 40.1 ± 4.38, blowdown: 51.6 ± 3.75), was signifi- cantly greater in the control after the wind- storm in both 2001 (control: 42.9 ± 5.47, blowdown: 23.4 ± 5.07) and 2002 (control: 37.6 ± 6.08, blowdown: 7.6 ± 3.23). A sim- ilar trend was observed in diameter of live trees (LIVDIA) in the blowdown area: mean diameter decreased by 2002 (7.9 ± 0.86) to only half that observed before the storm (15.6 ± 1.49). Whereas it was not significantly dif- ferent before the storm, evergreen tree cover (CTREE) and shrub or tree cover (CVR) were also significantly greater in the control than in the blowdown after the disturbance. On the other hand, percent shrub cover (CSHRB) was significantly greater in the control before the blowdown (control: 44.1 ± 5.06, blowdown: 22.6 ± 2.04), but was not significantly differ- ent afterwards in either 2001 (control: 45.3 ± 3.96, blowdown: 46.5 ± 5.15) or 2002 (con- trol: 42.8 ± 5.78, blowdown: 32.2 ± 3.45) due to tipped trees and broken-topped trees that were still alive in both years. The volume of coarse woody debris (DEBRIS) — the only variable that was not measured before the storm — was greater {P < 0.001) in the blow- down during both 2001 (control: 57.3 ± 12.35, blowdown: 93.3 ± 15.43) and 2002 (control: 33.6 ± 8.78, blowdown: 89.4 ± 14.05). Of the 30 bird species with identified ter- ritories in either the blowdown or control, 18 had territories in both plot types. Two species had territories only in the control while nine species had territories exclusively in the blow- down. Seven territorial and visitor species re- corded in the blowdown were not recorded in the control, whereas all species recorded in the control had territories or were recorded as vis- itors in the blowdown. Species for which we detected a greater percentage of territory cover per grid cell in the blowdown included Black-and-white War- bler (scientific names listed in Table 2; con- trol: 2.1 ± 1.49, blowdown: 13.3 ± 4.49, F140 = 5.60, P = 0.023), Chestnut-sided Warbler (control: 0, blowdown: 12.1 ± 4.35, ” 7.81, P = 0.008), and Mourning Warbler (control: 0, blowdown: 16.2 ± 5.72, F140 = 8.01, P = 0.007; Table 2). Species with a greater percentage of territory cover per cell in the control included Blackburnian Warbler (control: 20.5 ± 6.57, blowdown: 3.3 ± 1.90, Burris and Haney • BIRD COMMUNITIES AFTER BLOWDOWN 347 c3 g £ (/) w (D C3 s z O - .2 o o T3 3 ^ -C > S b ^ • o <2 > ^ Uh e 2 C/5 a ^ ^ o ^ V O S -c 2 E - 3 C 3 >. .= — ^ 0 3 § ^ O ^I'E i 1 2 ■S 2 ■§ 5 On O ^ On T3 y-v Qn PU - C +1 -J 2 = 11 a> h: o :/3 3; — ”0 u 3 o o > 00 ^ o c ^ cj -r o >. I ^ U 2 V5 2 ,0 2 _ o "d 3 3 O C 2 ^ i> _ a-rj (N g fN 3 3 •o O ri UJ 3 -) < o ffl > s I < s 10 r<^ in NO O — ' CM odd ^ o 00 — ; in ■^' +1 +1 +1 00 CM ^ 06 d d U U U U- [X, £ CO J u >- < J 0^5, ^ o3 o "3 -a x: 2 X — "O 3 o — u >■ < -J 00 inONCNOOl^CNOcncMCM ^cn-^cNO^cnONOtn^ ddddddddddd ooinoor^—'r^o^m -^r^'ONDOOONOpcM cNdd^t^'^— ^odd m On 00 (N ON ^ in +1 I gSi<<„^|a.o.£i. ^cnlZUOZSUcn^ > -5 ■^' 3 id II 3 ^ Nj 2 E ^ 2 ^ Sc § 2 ~ ■1:^ 2 5 -2 I I 2 -S .2 i? t £5 2 all I i = -P S ^ •= ^ 2 2 w, O U !/i 2 2 I ^ > cn ^ 2 H 2 3 X Z ^52 ^ tr ■O -2 •2 A 3 2 "2 E £ -a 2 v5 3 -a w t- X > o U O Z 2: ? I 2 hV ^ > E r ^ ^ § S o ^ S § £ "S « m +1 +1 0\ cn d d O CM ON in in Tt d (N d +1 +1 +1 O p — H d d (N X ac > zu> CO Z ^ OC CO PQ 2 3 I i 3 ai H 2 > "2 2 2 c ^ I 2 ^ Urn •2 ^ "5 ^ c5 u ^ ^ -o ^ § 3 t PC X cn (N NO NO (N 0(ncMNOOOON'^inON(N^oo ddddddddddddd ONt^oocoinoNNO t^ooqcNO-^Tfp (MddododcMO^inNOcn ON 00 00 ON cn (N (noo— '(sicntnminONCMO— 'cn incn coTt— ifO'^tnoocNOr^ OOCM -^^p^tCMpr^TtONOO Tt^t — id-H^oddddd +1 +1 > +1 +1 +1 +i +1 +1 +1 +1 +1 +1 ■^r^p^tcMO'^Otnin 00 (M d o d — ■ o d d d d d — ' cn —I CM in CM o 00 NO m in d d (N d d d d NO I +1 +1 +1 +1 +1 +1 +1 +1 > +1 +1 o in d d d(M-Hpr^—« d NO d d d 00 ON O (N X X < u u ^ u o u u w X m O X H ^ ^ < < < II > ^ » S U d X U §• .2 ‘C 2 2 '? "2 2 2 ^ 2 > c 2 (U g -O - J2 ^ .E §il > ■n o 2 o XXX ^ "2 2 5: 2 wj w E 6t) d ,E -o d —1 c =>c ^ s a. ?! 2? ^2 2 ‘5 ^ 2 ^ c ^ 2 r s 2 2 d X 2 ^ ■E 2 $ I 3 o ^ 2 -o ^ O X o> X ^ 3 ^ ^ 2 X E 2 3 ^ E E ^ ^ ^ i ^ c , C ^ ^ 3 o 2 3 u >- X u i_ oj > 2 Z ^ a 348 THE \STLSON BLXLETIN • Vol 117. So. 4. December 2005 T.ABLE 3. Selected habitat variables and associated correlations vrith each of three principal components ha\ing eigenvalues >1. PC.X based on 2001 and 2002 data from 21 blowdo\\Ti and 21 control cells. Superior National Forest, Minnesota. \-2n2bie PC : PC : PC 3 ^ tree cover 0.43 -0.08 -0.08 No. dead trees/ha 0.17 -0.33 -0.54 Live tree diameter tcm» 0.40 -0.10 0.34 ^te cover 0.31 -0.14 -0.16 ^ coarse liner cover 0.18 -0.31 0.72 Coarse woody debris tm'/hai -0.24 -0.51 -0.02 F = 6.28. P = 0.016). Golden-crowned Kinglet (control: 16.2 = 4.62. blowdown: 0.7 = 744. = 1 1.03. P = 0.002 1 and Yellow- rumped Warbler (control: 9.0 = 3.41. blow- down: 1.0 = 7.42. F — 5.38. P = 0.026: Table 2). By foraging guild. 6 of the 14 (43^) spe- cies of ground-brush foragers and flycatchers held territories in the blowdown but not in the control: 6 of the 8 (75*^) species holding ter- ritories in both blowdown and control had a greater percentage of territory cover in the blowdo\^Ti than in the controls. Four of the 13 (31*^) species of tree-fohage searchers had more territory cover in the control (all P < 0.05 ). Only the Red-eyed \'ireo had a greater percentage of territor\ cover in the blowdo\sTi (control: 2.1 = 2.14. blowdown: 12.6 =: 4.23. = 4.87. P = 0.033: Table 2). Three principal components had eigenval- ues >1 (PC 1 = 3.71. PC 2 = 1.78. PC 3 = 1.18) and together explained 67^ of the var- iance in the vegetation (iataset. The first prin- cipal component explained 37^ of the vari- ance and was positively correlated with the diameter of live trees and tree cover, while being negatively correlated with the volume of debris (Table 3). The second component, which explained 18*^ of the variance, was positively correlated with the number of live shrub stems and negatively correlated with the volume of debris (Table 3). A plot of PC 1 versus PC 2 (not showm) revealed only slight overlap of blowdown and control cells, indi- cating that the 10 habitat variables retained for use with the CCA reasonably separate one t> pe from the other. The Monte Carlo permutations test con- ducted with the CCA indicated that both the first canonical function (P = 0.027) and the overall test (P = 0.010) were significant, with the correlation between selected species and habitat being relatively high (r = 0.84). The first axis of the CCA accounted for 9.9^4 of the variation in the bird (iata. and was posi- ti\ ely correlated with the volume of debris (DEBRIS, r = 0.51 ) and negatively correlated with tree cover (CTREE, r = —0.72). Bird species preferring hea\y cover at or near the ground with little to no canopy cover (Mourn- ing Warbler. Chesmut-sided Warbler. Yellow- bellied Flycatcher, and Winter Wren) were positively correlated with the first axis — the volume of debris in particular — and are shov^m in the extreme right hand portion of Figure 2. Species such as the Golden-Cro\\Tied Kinglet, Blackburnian Warbler. Swainson's Thrush, and Northern Parula were negatively correlat- ed with the first axis and preferred more tree cover (Fig. 2). Although not significant, the second canon- ical function explained 5.0*4 of the variance in the bird data (Monte Carlo test: P = 0.21) and was positively correlated with bryoph>te cover iCBRYO. r = 0.66) and herb cover (CHERB. r = 0.41). Birds most closely as- sociated with bryoph\t:e and herb cover in- cluded Nashville Warbler. Northern Parula, and WTiite-throated Sparrow. DISCUSSION Our data suggest that the primary effect of the 4 July 1999 storm was a sigruficant de- crease in tree canopy and the diameter of live Burris and Haney • BIRD COMMUNITIES AFTER BLOWDOWN 349 O) X Low 4 Volume of debris » High High 4 Tree cover and live tree diameter ► Low F 1 FIG. 2. Bird distribution and vegetation variables (2001, 2002 data) based on functions 1 (FI) and 2 (F2) of a canonical correspondence analysis of 10 vegetation variables (codes defined in Table 1) and 15 bird species (codes defined in Table 2) from 21 blowdown cells and 21 control cells following a catastrophic 1999 blowdown in a black spruce-balsam fir forest in the Superior National Forest, Minnesota. The length and direction of the vector for each habitat variable corresponds to the level of its correlation with each function. trees, with a concomitant increase in shrub layer structure and coarse woody debris. Tree cover, which was generally characterized by black spruce, balsam fir, and paper birch (Bet- ida papyrifera), was slightly greater in the pre-blowdown but reduced to half that of the control as a result of the windstorm. The wind also decreased the number of live trees and the diameter of both live and dead trees by blowing over or breaking off all but the larg- est dead trees and most of the bigger live trees. In the shrub layer, fallen trees and tree- tops eliminated disparities between distur- bance and control plots with respect to shrub cover and the number of live shrub stems that existed before the storm by increasing the amount of cover at or near the ground in the blowdown area. Coarse woody debris in the blowdown area also increased significantly as a result of the storm. Many researchers have documented the im- portance of coarse woody debris to avian communities (Davis et al. 1999, Greenberg and Lanham 2001, Lohr et al. 2002), citing increases in nest-site suitability and food availability as possible explanations (Lohr et al. 2002) for its importance. Chestnut-sided and Mourning warblers, which were strongly associated with the volume of coarse woody debris, are often associated with dense shrub- bery and open woods of early successional forests (Apfelbaum and Haney 1981, Ehrlich 350 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 et al. 1988, Schulte and Niemi 1998). Winter Wren was also associated with the low-canopy blowdown despite being typically associated with old-growth forests (Hejl et al. 2002). Yel- low-bellied Flycatcher, White-throated Spar- row, and Black-and-white Warbler also showed some preference for areas with higher levels of coarse woody debris, with all but the White-throated Sparrow having significantly more territory cover in the blowdown. Red- eyed Vireo, a species often associated with closed-canopy or mature forest (James 1976, Faanes and Andrew 1983), also had signifi- cantly more territory cover in the blowdown but has been shown to respond better than ex- pected to canopy loss (Greenberg and Lanham 2001, Faccio 2003). Golden-crowned Kinglet and Blackburnian Warbler had significantly more territory cover in the control than in the blowdown and were highly correlated with the overall amount of tree canopy cover and the diameter of live trees (Fig. 2). Both species typically forage, and spend most of their time, high in the trees (Ehrlich et al. 1988, Morse 1994), and their numbers would likely decline if that stratum were reduced. Overall, a significant decrease in tree can- opy cover and the volume of coarse woody debris have provided more opportunities for species that forage or nest (or both) at or near the ground, while limiting opportunities for species more likely to use tree canopies. While these effects do parallel some of the responses to fire or timber-harvest disturbanc- es, differences are apparent as well. Both wind and fire lead to a decline in tree canopy, great- er numbers of snags, and an increase in ground and shrub-layer cover. After fire, how- ever, trees often die slowly over several years, and, in the Great Lakes region, they may re- main standing for several years before con- tributing to the volume of coarse woody de- bris. In contrast, severe wind resulted in an immediate decrease in tree cover and a cor- responding increase in shrub-layer structure and coarse woody debris. Like the effects of wind, logging activities also result in a reduc- tion of tree canopy and tree stem density, and an increase in coarse woody debris. Similar to what we found after the wind- storm, post-fire bird communities are typically distinguished by higher densities of flycatch- ers and ground-brush foragers and fewer tree- foliage searchers (Apfelbaum and Haney 1986, Drapeau et al. 2000, Morissette et al. 2002). The effect of logging on bird com- munities is largely dependent upon the num- ber of residual trees and snags and the amount of coarse woody debris (Brawn et al. 2001, Lohr et al. 2002). Unlike fire or wind, rela- tively few snags remain after clear-cuts, which leads to a nearly complete change in avian community composition (Schieck and Hobson 2000, Brawn et al. 2001). Natural disturbances like wind, and arguably timber harvests in some cases, result in more heterogeneous landscapes as a result of different serai stages (Niemi et al. 1998), thereby enhancing the di- versity of bird communities (Angelstam 1998, Brawn et al. 2001). ACKNOWLEDGMENTS We are indebted to E. M. Anderson and T. E Ginnett who suggested improvements to the manuscript. Pro- ject support was provided by E. Linquist with field assistance from R. L. Anderson, S. I. Apfelbaum, T. D. Bischof, J. I. Burton, J. Carlson, L. A. Ebbecke, E. M. Ernst, A. L. Graham, J. B. Graham, E. B. Haney, J. L. Kroll, L. B. Kroll, E. J. Lain, S. M. Lehnhardt, J. J. Nagel, S. E. Nielsen, R. Power, and J. D. Thorn- ton. LITERATURE CITED Angelstam, P. 1998. Maintaining and restoring bio- diversity in European boreal forests by developing natural disturbance regimes. Journal of Vegetation Science 9:593-602. Apfelbaum, S. and A. Haney. 1981. Bird populations before and after wildfire in a Great Lakes pine forest. Condor 83:347-354. Apfelbaum, S. I. and A. Haney. 1986. Changes in bird populations during succession following fire in the Northern Great Lakes Wilderness. Pages 1- 16 in National wilderness research conference: current research (Robert C. Lucas, Comp.). Gen- eral Technical Report INT-212, USD A Forest Ser- vice, Intermountain Research Station, Ogden, Utah. Bergeron, Y. 1991. The influence of island and main- land lakeshore landscapes on boreal forest fire re- gimes. Ecology 72:1980-1992. Blake, J. G., J. M. Hanowski, G. J. Niemi, and P. T. Collins. 1994. Annual variation in bird popula- tions of mixed conifer-northern hardwood forests. Condor 96:381-399. Bock, C. E. and J. E Lynch. 1970. Breeding bird pop- ulations of burned and unburned forest in the Si- erra Nevada. Condor 72:182-189. Bonan, G. B. and H. H. Shugart. 1989. Environmen- Burris and Haney • BIRD COMMUNITIES AFTER BLOWDOWN 351 tal factors and ecological processes controlling vegetation patterns in boreal forests. Landscape Ecology 3:111-130. Box, G. E. R AND D. R. Cox. 1964. An analysis of transformations. Journal of the Royal Statistical Society, Series B 26:211-252. Brawn, J. D., S. K. Robinson, and E R. Thompson, III. 2001. The role of disturbance in the ecology and conservation of birds. Annual Review of Ecology and Systematics 32:251-276. Canfield, R. H. 1941. Application of the line inter- ception method in sampling range vegetation. Journal of Forestry 39:388-394. Collins, S. L. 2001. Long-term research and the dy- namics of bird populations and communities: an overview. Auk. 118:583-588. Davis, L. R., M. J. Waterhouse, and H. M. Armle- DER. 1999. A comparison of breeding bird com- munities in serai stages of the Engelmann spruce- sub-alpine fir zone in east central British Colum- bia. Working Paper, no. 39. British Columbia Min- istry of Forests, Victoria, British Columbia, Can- ada. Drapeau, R, a. Leduc, J. F. Giroux, J. P. Savard, Y. Bergeron, and W. L. Vickery. 2000. Landscape- scale disturbances and changes in bird communi- ties of boreal mixedwood forests. Ecological Monographs 70:423-444. Dyer, J. M. and R. Baird-Philip. 1997. Wind distur- bance in remnant forest stands along the prairie- forest ecotone, Minnesota, USA. Plant Ecology 129:121-134. Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder’s handbook: a field guide to the natural history of North American birds. Simon and Schuster, New York. Faanes, C. a. and j. M. Andrew. 1983. Avian use of forest habitats in the Pembina Hills of northeast- ern North Dakota. Re.source Publication, no. 151, U.S. Fish and Wildlife Service, Washington, D.C. Faccio, S. D. 2003. Effects of ice storm-created gaps on forest breeding bird communities in central Vermont. Forest Ecology and Management 186: 133-145. Frelich, L. E. 2002. Forest dynamics and disturbance regimes. Cambridge University Press, Cambridge, United Kingdom. Frelich, L. E. and P. B. Reich. 1996. Old growth in the Great Lakes region. Pages 144-160 in Eastern old growth forests (M. B. Davis, Ed.). Island Press, Washington, D.C. Gill, F. B. and L. L. Woi.f. 1975. Economics of feed- ing territoriality in the Golden-winged Sunbird. Ecology 56:333-345. Greenberg, C. H. and J. D. Lanham. 2(K)1. Breeding bird assemblages of hurricane-created gaps and closed canopy forest in the southern Appala- chians. Fn)rest Ecology and Management 154: 251-260. Hfjl, S. j., j. a. Hoi.mes, and D. Fi. Kr(K)Dsma. 2002. Winter Wren {Troglodytes troglodytes). The Birds of North America, no. 623. Hobson, K. A. and J. Schieck. 1999. Changes in bird communities in boreal mixedwood forest: harvest and wildfire effects over 30 years. Ecological Ap- plications 9:849-863. Huxley, J. S. 1934. A natural experiment on the ter- ritorial instinct. British Birds 27:270-277. Irons, D. B., S. J. Kendall, W. P. Erickson, L. L. McDonald, and B. K. Lance. 2000. Nine years after the Exxon Valdez oil spill: effects on marine bird populations in Prince William Sound, Alaska. Condor 102:723-737. James, R. D. 1976. Foraging behavior and habitat se- lection of three species of vireos in southern On- tario. Wilson Bulletin 88:62-75. Karr, J. R. and R. R. Roth. 1971. Vegetation struc- ture and avian diversity in several New World ar- eas. American Naturalist 105:423-435. Kendeigh, S. C. 1944. Measurement of bird popula- tions. Ecological Monographs 14:69-106. Larson, B. M. H. and G. E. Waldron. 2000. Cata- strophic windthrow in Rondeau Provincial Park, Ontario. Canadian Field-Naturalist 1 14:78-82. Lohr, S. M., S. a. Gauthreaux, and J. C. Kilgo. 2002. Importance of coarse woody debris to avian communities in loblolly pine forests. Conserva- tion Biology 16:767-778. McCune, B. and M. j. Mefford. 1999. PC-ORD: mul- tivariate analysis of ecological data, ver. 4.33. MjM Software Design, Gleneden Beach, Oregon. Morissette, j. L., T. P. Cobb, R. M. Brigham, and P. C. James. 2002. The response of boreal forest songbird communities to fire and post-fire har- vesting. Canadian Journal of Forest Research 32: 2169-2183. Morse, D. H. 1994. Blackburnian Warbler (Dendroica fusca). The Birds of North America, no. 102. Niemi, G. j. and j. M. Hanowski. 1984. Relationships of breeding birds to habitat characteristics in logged areas. Journal of Wildlife Management 48: 438-443. Niemi, G., J. Hanowski, P. Helle, R. Howe, M. Monk- KONEN, L. Venier, AND D. WELSH. 1998. Ecolog- ical sustainability of birds in boreal forests. Con- .servation Ecology 2(2):article 17. http://www'. consecol.org/vol2/iss2/art 1 7. Pearman, P B. 2002. The scale of community struc- ture: habitat variation and avian guilds in tropical forest understory. Ecological Monographs 72:19- 39. Schieck, J. and K. A. Hoilson. 2000. Bird communi- ties associated with live residual tree patches with cut blocks and burned habitat in mixedwood bo- real forests. Canatlian .lournal i>f F-'orest Research 30:1281-1295. Schulte, L. A. and G. J. Niemi. 1998. Bird commu- nities of early successional burned and logged for- est. Journal of Wildlife Management 62:1418- 1429. .Smith, R. and M. Dai lman. 1996. F-orest gap use by 352 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 breeding Black-throated Green Warblers. Wilson Bulletin 108:588-591. Smith, T. M. and H. H. Shugart. 1987. Territory size variation in the Ovenbird: the role of habitat struc- ture. Ecology 68:695-704. Stewart-Oaten, A. and J. R. Bence. 2001. Temporal and spatial variation in environmental impact as- sessment. Ecological Monographs 71:305-339. Stewart-Oaten, A., W. W. Murdoch, and K. R. Parker. 1986. Environmental impact assessment: “pseudoreplication” in time? Ecology 67:929- 940. TER Braak, C. j. E 1986. Canonical correspondence analysis: a new eigenvector technique for multi- variate direct gradient analysis. Ecology 67:1 167- 1179. TER Braak, C. J. F. 1987. The analysis of vegetation- environment relationships by canonical correspon- dence analysis. Vegetatio 69:69-77. TER Braak, C. J. E 1994. Canonical community or- dination, part I. Basic theory and linear methods. Ecoscience 1:127-140. USDA Forest Service. 2002. After the storm: a pro- gress report from the Superior National Forest. USDA Superior National Forest, Duluth Minne- sota. Van Wagner, C. E. and I. R. Methven. 1978. Pre- scribed fire for site preparation in white and red pine. Pages 95-101 in White and red pine sym- posium (D. A. Cameron, Comp.). Symposium Proceedings O— P— 6. Department of the Environ- ment, Canadian Forestry Service, Great Lakes Forest Research Centre, Sault Ste. Marie, Ontario, Canada. Wiens, J. A., J. T. Rotenberry, and B. Van Horne. 1985. Territory size variations in shrubsteppe birds. Auk 102:500-505. Willson, M. E 1974. Avian community organization and habitat structure. Ecology 55:1017-1029. Winer, B. J., D. R. Brown, and K. M. Michels. 1991. Statistical principles in experimental design, 3rd ed. McGraw-Hill, New York. Wilson Bulletin 1 17(4):353-363, 2005 USE OF GROUP-SELECTION AND SEED-TREE CUTS BY THREE, EARLY-SUCCESSIONAL MIGRATORY SPECIES IN ARKANSAS LYNN E. ALTERMAN,''^'* JAMES C. BEDNARZ,' AND RONALD E. THILL^ ABSTRACT. — Silviculture in the Ouachita National Forest in Arkansas and Oklahoma has shifted in recent years from mostly even-aged management to a mix of even- and uneven-aged regeneration systems, including group-selection. Researchers have described presence/absence of early-successional bird species in forest open- ings created by even- and uneven-aged silviculture, but few have examined nest success. We examined occu- pancy and nest success of three early-successional species — Indigo Bunting (Passerina cyanea). Yellow-breasted Chat (Icteria virens), and Prairie Warbler (Dendroica discolor) — within 6- and 7-year-old openings created by group-selection (uneven-aged, <0.8 ha) and seed-tree (even-aged, 11-16 ha) cuts in Arkansas. We found 54 Indigo Bunting nests in openings created by seed-tree cuts and 28 in openings created by group-selection cuts (hereafter “seed-tree stands” and “group-selection stands,” respectively). We found 50 Yellow-breasted Chat nests in seed-tree stands, but only 2 were found in group-selection stands. We found 14 Prairie Warbler nests in seed-tree and none in group-selection stands. Mayfield nest success for Indigo Bunting was 30.9% in seed- tree stands and 41.9% in group-selection openings, but there was no difference in daily nest survival (0.952 ± 0.009 and 0.964 ± 0.010, respectively; x' = 0.792, P = 0.37). Our data suggest that Indigo Buntings can nest successfully in both regenerating seed-tree and group-selection stands; however, group-selection openings may be too small to support nesting Yellow-breasted Chats and Prairie Warblers. Public concerns about clear-cutting have resulted in increased use of uneven-aged management by the USDA Forest Service. However, before widespread implementation of group-selection cutting, additional research should be conducted to evaluate the effects of this management strategy on Neotropical migratory bird communities. Received 18 November 2004, accepted 24 August 2005. Due to growing public concerns about clear-cutting and planting, the USDA Forest Service (USFS) is now relying more on nat- ural regeneration systems involving both even-aged (e.g., seed-tree and shelterwood) and uneven-aged (e.g., single-tree and group- selection) silvicultural practices (Thill and Koerth 2005). On the Ouachita National For- est (ONF) in west-central Arkansas and east- central Oklahoma, clear-cutting has been largely replaced by seed-tree, shelterwood, single-tree, and group-.selection management. Seed-tree management is similar to clear-cut- ting, but relies on natural regeneration from trees (typically 10-25 mature trees/ha) that are retained as a seed source (Holland et al. 1990). Under group-selection management, roughly 10% of the stand is clear-cut every 10 ' Dept, of Biological Sciences. Arkansas State Univ., Jonesboro, AR 72467-0599, USA. ^ USDA Forest Service, Southern Research Station, Wildlife Habitat and Silviculture Lab., 506 Hayter St.. Nacogdoches. TX 75965-3556, USA. ^ Current address: Fcosphere Hnvironmental .Servic- es, 2257 Main Ave., Patio I.evel. Durango, CO 81301 USA. ■‘Corresponding author; e-mail: alterman@ecosphere-services.com years within small (<0.8 ha) patches that are allowed to regenerate naturally. If the sur- rounding stand (matrix) contains sufficient timber volume, it also may be thinned con- currently with the patch cuts (Smith 1986, Baker et al. 1996). Following a succession of treatments, this system creates a mosaic of forest patches of differing serai stages. In general, tree removal results in the de- cline of many forest-interior bird species (Robinson et al. 1995, Thompson et al. 1995, Annand and Thomp.son 1997). Clear-cutting and heavy thinning treatments, however, can create habitat for a suite of early-successional bird species that would otherwi.se not occur, or occur infrequently, in forested landscapes (Annand and Thomp.son 1997, Germaine et al. 1997, Costello et al. 2()00). Many of these ear- ly-SLiccessional species have experienced widespread population declines in recent years (Askins 1993, Litvaitis 1993). Group-.selec- tion silviculture may be appealing to wildlife managers because it creates habitat for early- successional species and allows some species that require mature forest to remain in the for- est matrix after harvest (Chambers et al. 1999, Robinson and Robinson 1999, Costello ct al. 2()()0). ITirthcrmorc, group-.selection silvicul- 353 354 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 ture may increase overall bird abundance and diversity in some areas relative to untreated stands (Germaine et al. 1997). However, re- cent studies have shown that some early-suc- cessional species that occur in large forest openings do not use, or occur less frequently, in the smaller openings created by group-se- lection cuts (Annand and Thompson 1997, Rodewald and Smith 1998, Robinson and Robinson 1999, Costello et al. 2000). These data suggest that group-selection silviculture may not be suitable for some early-succes- sional bird species in forested landscapes, and that a mix of silvicultural techniques may be necessary to maintain populations of these species (Annand and Thompson 1997, Cham- bers et al. 1999, Costello et al. 2000). Whereas species presence/absence data are meaningful, they are not sufficient to uncover causes of reproductive failure that may limit populations associated with different silvicul- tural practices (Donovan et al. 1995). Several recent studies were designed to evaluate nest success in stands treated with group-selection harvests (e.g., King et al. 2001, Twedt et al. 2001, Gram et al. 2003, King and Degraaf 2004); however, only a few compared nest success of early-successional species in regen- erating group-selection cuts to that in other treatments (King et al. 2001, Gram et al. 2003). Barber et al. (2001) compared nesting success on the ONF under several silvicultural treatments, including single-tree selection, but there are no data for evaluating nesting suc- cess under group-selection systems in this area. These data are needed, however, because the ONF plans substantial use of group-selec- tion silviculture in the future. Our objective was to compare occupancy and nesting success of three early-succession- al Neotropical migrants within stands treated with traditionally sized (<0.8 ha) group-selec- tion cuts and larger seed-tree cuts (10-16 ha) in the Ouachita Mountains of Arkansas. We chose the latter treatment because it is one of the primary even-aged regeneration systems being used on the ONF. We predicted that nest success would be lower in the small, group- selection cuts than in the larger seed-tree cuts. We also predicted higher rates of nest preda- tion in group-selection than in seed-tree cuts. Parasitism by Brown-headed Cowbirds {Mol- othrus ater) is low on the ONF (Barber et al. 2001) and elsewhere in forested landscapes (Hoover and Brittingham 1993, Hoover et al. 1995, Hanski et al. 1996); therefore, we did not expect parasitism to be an important cause of nest failure. In addition to examining oc- cupancy and nest success, we also evaluated microhabitat characteristics at nest sites. We compared habitat structure (1) between nests in small openings created by group-selection silviculture and those in larger openings cre- ated by seed-tree silviculture, and (2) between successful and unsuccessful nests. METHODS Study area. — Our study was conducted in 2000 and 2001 on the easternmost portion of the ONF in Garland. Perry, and Saline coun- ties, Arkansas. Mixed pine-hardwood stands on the ONF occur at elevations ranging from approximately 90 to 820 m, and are charac- terized by a diverse mix of vegetation domi- nated by shortleaf pine {Pinus echinata), oaks (Quercus spp.), and hickories (Carya spp.). Common hardwoods include white oak {Quer- cus alba), black oak {Q. velutina), northern red oak {Q. rubra), post oak {Q. stellata), blackjack oak {Q. marila?-idica), mockemut hickory {Carya tomentosa), red maple {Acer rubrum), black tupelo {Nyssa sylvatica), winged elm {Ulmus alata), and flowering dog- wood {Comus florida). Common shrubs in- clude winged sumac {Rhus copallinum), big- leaf snowbell {Styrax grandifolia), American beautyberry {Callicarpa americana), sparkle- berry {Vaccinium arboreu??i), and other Vac- cinium species. Our study areas included three group-selec- tion and three seed-tree stands; one of the lat- ter had to be replaced in 2001 because it was inadvertently burned after the 2000 held sea- son. Each treatment was 6 years post-harvest at the initiation of this study in 2000. Seed- tree stands ranged from 11 to 16 ha in size. Two of the group-selection stands were 12 ha, and each contained three openings. The third group-selection stand was 36 ha, and con- tained 15 openings. Our group-selection stands had been subjected only to their first treatment in a series of harvests; thus, these stands were in transition from an even-aged to an uneven-aged condition. The 21 group- selection openings from our three stands ranged in size from 0.14 to 0.76 ha (mean = Alterman et al. • USE OF GROUP-SELECTION AND SEED-TREE CUTS 355 0.33 ha); however, 19 (91%) of the openings were <0.40 ha, which is half the upper limit (0.8 ha) used under traditional group-selection management. The mean nearest-neighbor dis- tances between adjacent group-openings in the two smaller stands were 169 and 131 m, and the mean in the larger stand was 48 m. The ratios of early successional to forested habitat in the smaller group-selection stands were 1 .0: 13.8 and 1.0:7. 5 ha, and the ratio in the larger stand was 1. 0:9.0 ha. Fieldwork. — Fieldwork was conducted be- tween early May and mid-August in 2000 and 2001. We chose three focal study species — Indigo Bunting {Passerina cyanea). Yellow- breasted Chat (Icteria virens), and Prairie Warbler (Dendroica discolor) — for monitor- ing nest success in regenerating seed-tree and group-selection stands. These species were se- lected because they are common in forest openings in the ONF and their nests are rel- atively easy to find. We located nests of target species by fol- lowing adults carrying nest material or food, by observing them return to their nests to re- sume incubation, and by systematic searches of the study areas. We found a few additional Yellow-breasted Chat nests by attaching radio transmitters (Johnson et al. 1991) to the backs of females that we caught with mist nets. We tracked these birds until we found their nests or until the transmitters fell off. Nests were monitored an average of once every 3-4 days following the techniques of Martin and Geu- pel (1993). Whenever possible, we used bin- oculars to check nest status from a distance; however, we approached nests and checked contents when we expected a transition from one nesting phase to the next (e.g., incubation to nestling). When checking nest contents, we approached from one path and left from an- other to reduce the probability of attracting predators. Nests were considered successful if at least one host young fledged from the nest. Fledging was confirmed if we observed fledg- lings, heard begging calls outside of the nest, or observed adults carrying food or behaving defensively (chipping) on or near the expected fledging date. Nests were considered depre- dated if they were empty prior to the expected fledging date. Habitat characteristics of nest sites were quantified within 5.0- and 1 1 .3-m-radius cir- cles (0.04 ha) centered on the nests, following a modified BBIRD Protocol (Martin et al. 1997). Between late June and August of each year, we measured habitat characteristics after nests had failed or the young had fledged. We did not conduct habitat sampling at nests that were abandoned prior to egg laying, deserted with eggs or chicks in the nest, or when nest fate was unknown. Characteristics measured at nests included nest height, height and diameter of the nest plant, number and mean diameter of branches supporting the nest, and distance from the nest to the nearest forest edge. We also visually estimated nest concealment (from 1 m away) from the side of the nest in each of the four cardinal directions. At each location, we as- signed a concealment index value from 1 to 6 (1 = 0-5, 2 - 6-25, 3 = 26-50, 4 = 51-75, 5 = 76—95, and 6 = 96—100%), corresponding to the percent of the nest that was concealed by vegetation. We then calculated the mean index value for concealment from the side. Habitat characteristics measured within the 5.0-m-radius circles included slope, mean shrub height, shrub density in two size classes (<2.5 and >2. 5-8.0 cm diameter), and indices of various types of ground cover, including shrubs (in three height classes: 0-0.5, 0.5-1, and >1 m), grasses, forbs, ferns, vines, leaf litter, downed logs, and bare ground. Slope of the circle was measured using a clinometer. For all other measurements, we divided the circle into four quadrants, bounded by the four cardinal directions (Martin et al. 1997). Each characteristic was measured within each of the four quadrants, and a mean value was calcu- lated. Mean shrub height was estimated visu- ally using a meter stick as a reference. We considered all trees <3 m in height to be shrubs. We calculated shrub density by count- ing the number of stems in each size class within a I-nF quadrat placed in each of the four quadrants of the circle. Indices of ground cover were estimated visually using the same categories as those used for nest concealment. Characteristics measured in the 11. 3-m-ra- dius circles included mean tree height, percent canopy cover, and density of trees and snags. We used a clinometer to measure the height of all trees in the circle, and then calculated the mean height. Canopy cover was measured using a ccmcave spherical densiometer. For 356 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 tree and snag density, we separated trees into three size classes (8—23, >23—38, and >38 cm dbh) and snags into two size classes (<12 and >12 cm dbh). Density was calculated by counting the number of trees and snags in each size class. Statistical analyses. — We calculated daily nest survival probabilities for Indigo Bunting and Yellow-breasted Chat using the Mayfield (1975) method with the standard error esti- mator developed by Johnson (1979). We did not use the Mayfield method for Prairie War- bler because we found too few (<20) nests (Hensler and Nichols 1981); instead, we cal- culated apparent nest success (the number of successful nests divided by the total number of nests). For Indigo Bunting and Yellow- breasted Chat, we calculated daily survival probabilities for each phase of nesting (egg laying, incubation, and nestling), as well as for the entire nesting period. We only included nests in the Mayfield analysis that were ob- served for >1 day (i.e., we did not include nests that were found on the day of failure or fledging). Survival estimates were based on a 25 -day nesting period for Indigo Bunting (4 egg-laying days, 12 incubation days, and 9 nestling days) and a 24-day nesting period for Yellow-breasted Chat (4 egg-laying days, 12 incubation days, and 8 nestling days) based on our nest-monitoring data. To calculate nest success, survival probabilities were raised to the power of the number of days in the nesting period (e.g., daily nest survivaP^ = nest suc- cess for Indigo Bunting). We tested for a year effect between 2000 and 2001 by comparing daily nest survival of Indigo Bunting and Yel- low-breasted Chat using program CON- TRAST (Hines and Sauer 1989) and an alpha level of 0.05. There were no significant dif- ferences between years for either species; therefore, we used CONTRAST (Hines and Sauer 1989) to compare daily nest survival of Indigo Bunting in seed-tree versus group-se- lection stands. We did not compare daily sur- vival between the two stand types for Yellow- breasted Chat because we found too few nests in group-selection stands. We could not com- pare apparent nest success of Prairie Warbler in the two stand types because this species did not nest in group-selection stands. We used Minitab (Minitab, Inc. 1998) to conduct all statistical analyses for habitat var- iables. We examined plots of the data and test- ed for normality. Most habitat variables were normally distributed; therefore, we tested for a year effect using two-sample r-tests (alpha level = 0.05). Nest-site habitat characteristics were similar between years for all species and data were pooled across years. We used two- sample r-tests to compare nest-site habitat var- iables between group-selection and seed-tree stands for Indigo Bunting. To determine whether habitat variables differed between the two stand types, we also evaluated effect size and 95% Cl around the effect size (Anderson et al. 2001, Di Stefano 2004) instead of using only the P-values generated from r-tests. To determine which habitat variables best explained nest success, we conducted binary logistic regression analysis. Logistic regres- sion was conducted for Indigo Bunting nests in group-selection and seed-tree stands as well as for all nests pooled, and for Yellow-breast- ed Chat nests in seed-tree stands. Successful and unsuccessful nests were binary indepen- dent variables. For each analysis, we reduced the number of candidate independent variables by conducting univariate logistic regression analyses for each habitat variable (Hosmer and Lemeshow 1989) — retaining variables that differed between successful and failed nests and using an alpha level of <0.15. We tested for correlation between the retained var- iables by calculating Pearson correlation co- efficients; when two or more variables were correlated {P < 0.05), we included the vari- able that we thought was more biologically meaningful, based on our knowledge of the birds’ behavior and ecology. For each analy- sis, we then performed logistic regression us- ing all variables (full model) and on all sub- sets of the full model. We ranked models us- ing Akaike’s Information Criterion modified for small sample size (AIC^; Anderson et al. 2001), and present all models where AAIC^ < 2. If AAIC^ for all other candidate models was > 2, we present the second-best model as a comparison. Model fit was evaluated using the Hosmer-Lemeshow lack-of-fit test (Hosmer and Lemeshow 1989), in which higher P-val- ues indicate that the data fit the model well. RESULTS Nest success. — We found a total of 82 In- digo Bunting (54 in seed-tree and 28 in group- Alterman et al. • USE OF GROUP-SELECTION AND SEED-TREE CUTS 357 TABLE 1. Daily survival for Indigo Bunting nests in seed-tree (n = 48) and group-selection stands (n = 25) on the Ouachita National Forest, Arkansas, 2000-2001. Seed-tree Group-selection Nest phase Failed nests Exposure days Daily survival ± SE Failed nests Exposure days Daily survival ± SE pa Egg laying 1 21 0.952 ± 0.047 1 26 0.962 ± 0.038 0.231 0.88 Incubation 8 283 0.972 ± 0.010 6 195 0.969 ± 0.012 0.248 0.88 Nestling 17 242 0.930 ± 0.017 5 117 0.957 ± 0.019 1.209 0.27 Total 26 545 0.952 ± 0.009 12 338 0.964 ± 0.010 0.792 0.37 2nd P- values were calculated using program CONTRAST (Hines and Sauer 1989). selection stands), 52 Yellow-breasted Chat (50 in seed-tree and 2 in group-selection stands), and 14 Prairie Warbler (all in seed-tree stands) nests. The two chat nests in group-selection stands were found during different years, but both were located in the same stand and with- in the largest of all 21 group-openings (0.76 ha). We observed male Prairie Warblers in 3 of the 21 group-selection openings, but we did not observe any females or nesting activity at these sites. As these two latter species were rarely found in group-selection stands, we could not compare nesting success between the two treatment types. Mayfield nest success for Yellow-breasted Chats in seed-tree stands was 31.3% (n = 46 nests, excluding 4 discovered on the day of fledging or failure) and overall daily nest sur- vival was 0.951 ± 0.009 SE. Both chat nests found in group-selection stands failed. Appar- ent nest success for Prairie Warblers was 45.4% (n = 11). Three Prairie Warbler nests were not included because we could not de- termine nest fate. Mayfield nest success for Indigo Buntings was 41.0% in group-selection (n = 25) and 29.2% in seed-tree stands (n = 48), but there was no significant difference in daily nest sur- vival between the two stand types (Table 1 ). Nine of the 82 nests were not included in the analysis because they were discovered either on the day of fledging or failure. Predation was the primary cause of nest failure for Indigo Bunting (37 of 44 failed nests; 84.1%), Yellow-breasted Chat (30 of 33 failed nests; 90.9%), and Prairie Warbler (5 of 6 tailed nests; 83.3%). For all species com- bined, 72 of 83 (86.7%) nests failed because of predation. Nest desertion (eggs or chicks present) was the second highest cause of nest failure for buntings (6 of 44 failed nests; 13.6%), chats (2 of 33 failed nests; 6.1%), and warblers (1 of 6 failed nests; 16.7%). Other causes of nest failure included nest abandon- ment prior to egg laying (1 of 33 failed nests; 3.0% for chats) and brood parasitism by Brown-headed Cowbird (1 of 44 failed nests; 2.3% for buntings). Overall nest predation for Indigo Bunting was 45.1% (37 of 82 nests). Cowbird eggs were observed in three bunting nests, but only one of these nests failed to fledge host young. The other two nests fledged at least one cowbird and one bunting. Overall nest predation for Yellow-breasted Chat was 57.7% (30 of 52 nests). Cowbird eggs were also observed in two chat nests (3.8%), but these nests failed due to predation. Overall nest predation for Prairie Warbler was 35.7% (5 of 14 nests). Cowbird parasitism was not observed in Prairie Warbler nests. Habitat characteristics. — Eleven habitat variables differed between Indigo Bunting nests in seed-tree compared with group-selec- tion stands (Table 2). Distance to forest edge, tree height, and grass and forb cover were greater at nests in seed-tree stands. Fern and vine cover, total tree density, density of trees 8-23 and >38 cm dbh, total snag density, and density of snags >12 cm dbh all were greater at nests in group-selection stands. Based on the results of the univariate re- gressions and Pearson correlation tests, we identified four habitat variables for multiple logistic regression analysis that explained the variation in Indigo Bunting nest success in group-selection stands: diameter of branches supporting the nest, distance to forest edge, mean shrub height, and vine cover. The best models (AAIC, < 2) explaining nest success in group-selection stands indicated that nests in areas with increased cover of vines were more likely to be successful ( fable 3). The 358 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 TABLE 2. Habitat characteristics at Indigo Bunting nests in group-selection (n = 26y and seed-tree (n - 42Y stands on the Ouachita National Lorest, Arkansas, 2000-2001. Habitat characteristic*’ Group-selection mean ± SE Seed-tree mean ± SE Effect size 95% Cl pc Distance to forest edge (m) 15.80 ± 2.30 35.71 ± 6.88 -19.91 -5.27 to -34.56 0.009 Grass cover index^ 1.86 ± 0.14 2.63 ± 0.15 -0.78 -0.36 to -1.19 <0.001 Lorb cover index‘d 1.13 ± 0.03 1.55 ± 0.06 -0.42 -0.27 to -0.57 <0.001 Pern cover index‘d 1.42 ± 0.10 1.02 ± 0.01 0.40 0.20 to 0.60 <0.001 Vine cover index'* 2.13 ± 0.16 1.71 ± 0.10 0.42 0.04 to 0.80 0.030 Tree height (m) 13.03 ± 0.68 17.55 ± 0.93 -4.52 -2.23 to -6.83 <0.001 Total tree density^ 11.63 ± 1.80 6.12 ± 0.64 5.51 1.61 to 9.40 0.007 Tree density (8-23 cm dbh)^ 8.48 ± 1.60 2.98 ± 0.54 5.51 1.98 to 9.03 0.003 Tree density (>38 cm dbh)® 0.93 ± 0.20 0.45 ± 0.12 0.47 0.00 to 0.95 0.049 Total snag density® 3.30 ± 0.49 1.00 ± 0.24 2.30 1.19 to 3.41 <0.001 Snag density (>12 cm dbh)® 2.37 ± 0.38 0.55 ± 0.17 1.82 0.98 to 2.66 <0.001 3 Habitat characteristics were not measured at nests that were abandoned prior to egg laying, deserted with eggs or chicks in the nest, or when nest fate was unknown. See Alterman (2002) for nonsignificant habitat data. P-values from two-sample f-tests. Index based on cover classes described in methods. ^ Tree and snag densities are reported per 0.04 ha. best model also indicated that nests in areas with shorter shrubs were more likely to be successful. Four habitat variables were con- sidered for multiple logistic regression models explaining variation in bunting nest success in seed-tree stands: nest height, nest concealment from the side, shrub cover 0. 5-1.0 m, and mean tree height. The models that best ex- plained variation in nests success in seed-tree stands (AAIC^ < 2) indicated that nests lower to the ground in areas with shorter trees were more likely to be successful (Table 3). The best model also indicated that nests in areas with increased cover of shrubs 0.5- 1.0 m tall were more likely to be successful; however, the Hosmer-Lemeshow lack-of-fit test indicat- ed that the data were not a good fit to the model (Table 3). Four habitat variables were also considered for multiple logistic regres- sion models explaining variation in nest suc- cess for pooled Indigo Bunting nests: mean shrub height, vine cover, mean tree height, and density of trees >38 cm dbh. The model that best explained variation in nest success for the pooled sample indicated that nests in areas with shorter shrubs, shorter trees, and fewer large trees were more likely to be successful (Table 3). Increased vine cover was also an indicator of nest success in the second-best model. Based on the results of the univariate re- gressions and Pearson correlation tests, we identified five habitat variables for inclusion in multiple logistic regression analysis ex- plaining variation in Yellow-breasted Chat nest success in seed-tree stands: nest height, nest concealment from the side, distance to forest edge, density of trees >38 cm dbh, and density of snags <12 cm dbh. Most of the models that best explained variation in nest success indicated that nests lower to the ground and farther from the forest edge were more likely to be successful (Table 3). Some of the models also indicated that nests in areas with fewer large trees and small snags were more likely to be successful. DISCUSSION Occupancy and nest success. — Our data clearly show that Indigo Buntings can nest successfully in regenerating forest created by group-selection and seed-tree silviculture. Furthermore, daily nest survival was similar among treatments and we did not observe el- evated levels of predation in group-selection openings. As expected, parasitism by Brown- headed Cowbird was very low for all species. Few studies have presented similar compara- tive data on nest success of early-successional species in large and small forest openings. Our results are consistent with those of King et al. (2001), who found no difference in daily nest survival for Chestnut-sided Warbler {Dendroica pensylvanica) in 6- to 10-ha clear- cuts (0.993) and 0.2- to 0.7-ha group-selection cuts (0.987) in New Hampshire. They also TABl.E 3. l.ogistic regression models explaining nest success for Indigo Buntings and Yellow-breasted Chats on the Ouachita National Forest, Arkansas 2000- 2(K)1. Alterman et al. • USE OF GROUP-SELECTION AND SEED-TREE CUTS 359 y < < ON »n X 3- ON X ON X X 3" t^ rx X SO o 1-H o X X 00 X X ON 00 X X 0 o u (U c ’> ON d > o o X 00 'S X (U D > 0 O > o CJ 0 (U o c 3 0 (U 3 C 3 0 3 3 C 3 0 3 3 C 3 V c 3 c 3 'y C 3 •3 3 3 3 3 0 C 3 •3 3 3 L. OX) 3 C y rx ON p, u. o o 3 L. u. X ON (N (N Ov (N d + a X ■y 00 c > X (N X _c y CN n y •3 (N y •3 00 y 0 rx •3 OX) 3 c y 0 0 X X X d 1 r~ X d d -1- u (N d X •3 i c d q d q y X T X X -p 1 -p w c d -p -P E o -p + -P -p -P CN -P -p E ^3 OJ) •3 3 OX) •3 -P "3 OX) 3 Wj 3 -p oc ^ 1 3 3 3 X 3 'S X X X X X X X X 1 X X rx 0 0 op C JC r~ X op op op op op op op V 3 3 '3 3 3 X; O Olj 'B u '53 'S 'C '3 '3 + ’3 ‘3 3 3 X 3 c 'C X X X X X X X X C C C X y 3 u. X X y y 0) X a c s X -P -P -p -P DC X -P X -P -p 1 -P o + 'y -P -P y -P -P + 3; r- Os X ■3- d X -t Os 3 (U u 3- O' X X -P 3- 00 X A 00 n q c •3 2 X C 3 -3 X X d 3 •3 X (N rx 1 X 3; r- d 1 1 — d ri d ri — d ri ri X T 1 1 T - C ^ -y, 3 f "3 25 Cl C 3 3 OL i- •y k. ■a o c/5 3 u •3 O y 3 O 1» • Akaike weight. ^ Probability values from x‘ test indicating overall mtxJel significance. ‘ Probability from Hosmer-l.emeshow lack-of-fit test (Hosmer and l.emeshow' 1989). 360 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 found no difference in daily nest survival after pooling data for 16 species. Gram et al. (2003) also reported no difference in daily nest sur- vival for Indigo Buntings in regenerating 3- to 13-ha clear-cuts (0.969) and stands treated with both group- and single-tree harvest (0.967) in the Missouri Ozarks. From our study, it is evident that group- selection openings <0.4 ha may be too small to support nesting Yellow-breasted Chats or Prairie Warblers. This conclusion is consistent with Annand and Thompson’s (1997) pres- ence/absence data for these species in clear- cuts and group-selection openings. In our study, chats did nest in one group-selection opening; however, this was the largest (0.76 ha) of the 21 openings. Chats were not ob- served in any of the other 20 group-openings (all but 1 were <0.4 ha). Prairie Warblers were also observed in two of the group-selec- tion cuts, one of which was the largest open- ing, while the other was <0.4 ha. Because we monitored nests frequently, we are confident that we spent enough time in the group- selec- tion stands to determine that both Yellow- breasted Chats and Prairie Warblers were in- deed absent from the majority of the group- selection openings. In the near future, forest managers in the ONF are considering imple- menting experimental clear-cuts of interme- diate size (2 ha), which may be more suitable for nesting Yellow-breasted Chats and Prairie Warblers. Additional research is needed to evaluate the minimum patch-size require- ments for these and other early-successional species. The change in condition of group-selection stands over time may also be an important factor for early-successional birds. The group- selection stands in this study had been treated only once, and represented a transition phase from an even-aged to an uneven-aged condi- tion. The effects of repeated treatments every 10-15 years are unknown and should be stud- ied. Nevertheless, occupancy and nest-success data are important for early-successional spe- cies in transitional group-selection stands be- cause all even-aged stands go through this process when subjected to uneven-aged man- agement. Habitat characteristics. — Although there were a number of significant differences in microhabitat variables at Indigo Bunting nests in seed-tree versus group-selection openings (Table 2), daily nest survival in the two stand types was similar. Some of these differences are more likely a function of the differences in opening size rather than avian selection for specific nest-site characteristics. The results of regression analyses indicated that most micro- habitat variables were similar for successful and failed nests of Indigo Buntings and Yel- low-breasted Chats; however, differences in a few key variables may be biologically impor- tant to nesting success. Increased vegetative cover surrounding nests explained a large por- tion of the variation in nest success in group- selection (vine cover) and seed-tree (shrub cover 0.5- 1.0 m tall) stands, and for all nests pooled (vine cover). Nests in areas with more vegetative cover may be less conspicuous to some predators. In addition to shrubs, our study areas contained several vine species, es- pecially muscadine grape {Vitis rotundifolia), which often afforded excellent vegetative cov- er. Logistic regression models also indicated a negative relationship between nest height and probability of nest success for buntings and chats in seed-tree stands. Nests placed lower to the ground may be less conspicuous to some avian predators, which usually detect nests from above. In contrast, Ricketts and Ritchison (2000) found that height of Yellow- breasted Chat nests was greater for successful (median = 0.83 m) than failed (median = 0.75 m) nests in mixed woodland and early-suc- cessional habitat in Kentucky. Burhans et al. (2002) also found increased nest predation at Indigo Bunting nests that were lower to the ground. There may be an optimal range of nest height that reduces predation rates in spe- cific habitats, and this may differ among hab- itat types and geographical locations. One other habitat variable that may be bi- ologically important to some early-succes- sional species in the ONF is distance to the forest edge. In our study, increased distance to the forest edge was important in explaining nest success for Yellow-breasted Chat in seed- tree stands. Because predation was the pri- mary cause of nest failure for chats, our model suggests that predation may have increased with decreasing distance to the habitat edge. Distance to edge did not explain variation in Indigo Bunting nest success, however. Wood- Alterman et al • USE OF GROUP-SELECTION AND SEED-TREE CUTS 361 ward et al. (2001) also found some evidence of edge effect on Yellow-breasted Chat (but not Indigo Bunting) nest success in the Mis- souri Ozarks. In that study, chat nests closest to edges (<20 m) had higher predation rates than nests 21-40 m from forest edges. Pre- dation increased, however, at nests >40 m from edges. Other recent studies suggest little or no edge effect associated with openings created by silviculture in predominantly for- ested landscapes for forest-interior (Hanski et al. 1996, Duguay et al. 2001, Rodewald 2002) and early-successional species (Hanski et al. 1996, King et al. 2001). However, Manolis et al. (2000) showed that many studies that failed to detect edge effects in forested land- scapes did not have sufficient power. Other recent studies in forested landscapes have documented mixed results — that is, they showed edge-related increases in nest preda- tion for some species but not others (Burke and Nol 2000, Flaspohler et al. 2001). Management implications. — Our results suggest that group-selection silviculture may not be the most appropriate strategy on the ONF for providing habitat for some early-suc- cessional, migratory bird species. If seed-tree cuts are replaced by group-selection cuts on a large scale, this management strategy might reduce availability of nesting habitat for some early-successional species, such as Yellow- breasted Chat and Prairie Warbler. Suitable habitat for these species during the breeding season is important because many have exhib- ited population declines in Arkansas and else- where in recent decades (James et al. 1992, Sauer et al. 2001 ). The USFS and other land management agencies have begun to shift their silvicultural practices toward uneven-aged management (Costello et al. 2000). Group-selection silvi- culture may increase avian abundance and di- versity in forested communities because these treatments create habitat for early-succession- al species while retaining forested habitat and many forest-interior species (Germaine et al. 1997). However, several studies have shown that early-successional species occur less fre- quently in small forest openings (Annand and Thompson 1997, Rodewald and Smith 1998, Robinson and Robinson 1999). Our data are consistent with these latter findings. Imple- mentation of widespread management tech- niques in national forests that improve habitat for some species at the expense of other spe- cies of conservation concern, such as Yellow- breasted Chat and Prairie Warbler, should be undertaken with the knowledge of the poten- tial negative impacts on those species. Before its widespread adoption, forest managers should understand how group-selection man- agement techniques affect the abundance and diversity of the entire avian community. Im- plementing a mix of silvicultural techniques may be necessary to maintain populations of early-successional species in the ONF and similar forested landscapes. ACKNOWLEDGMENTS This project was funded by the Southern Research Station of the USD A Forest Service, the Arkansas Game and Fish Commission, and Arkansas State Uni- versity. We thank G. Perry for her field assistance. R. Perry assisted with study site selection and provided logistical support for this project. R. Grippo, D. In- gram, R. Johnson, and C. Kellner provided technical, editorial, and statistical advice. LITERATURE CITED Alterman, L. E. 2002. Nesting success and postfledg- ing survival of Neotropical migratory birds in the Ouachita Mountains of Arkansas. M.Sc. thesis, Arkansas State University, State University. Anderson, D. R., W. A. Link, D. K. Johnson, and K. P. Burnham. 2001. Suggestions for presenting the results of data analysis. Journal of Wildlife Man- agement 65:373-378. Annand, E. M. and E R. Thompson, III. 1997. Forest bird response to regeneration practices in central hardwood forests. Journal of Wildlife Manage- ment 61:159-171. Askins, R. a. 1993. Population trends in grassland, shrubland, and forest birds in eastern North Amer- ica. Current Ornithology 1 1:1-34. Baker, J. B., M. D. Cain, J. M. Guldin. P. A. Murphy, AND M. G. Shelton. 1996. Uneven-aged silvicul- ture tor (he loblolly and shortleaf pine forest cover types. General Technical Report SO- 118, USDA Forest Service. Southern Research Station, Ashe- ville, North Carolina. Barrer, D. R., T. E. Martin, M. A. Melchiors. R. E. I MILL, AND T. B. WiCiLHY. 2001. Nesting success of birds in different silvicultural treatments in .southeastern U.S. pine forests. Conservation Bi- ology 15:196-207. Bi'rhans, D. F'.. D. Di:arhorn, F! R. Thompson. III. AND J. FaaborCi. 2(M)2. F'acttirs affecting predation at songbird nests in old lields. Journal of Wildlife Management 66:240-249. Burki;. D. M. and F:. Nol. 2(HM). Landscape and frag- ment si/e effects on reproductive success of for- 362 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 est-breeding birds in Ontario. Ecological Appli- cations 10:1749-1761. Chambers, C. L., W. C. McComb, and J. C. Tappei- NER, II. 1999. Breeding bird responses to three silvicultural treatments in the Oregon Coast Range. Ecological Applications 9:171-185. Costello, C. A., M. Yamasaki, P. J. Pekins, W. B. Leak, and C. D. Neefus. 2000. Songbird response to group selection harvests and clearcuts in a New Hampshire hardwood forest. Forest Ecology and Management 127:41-54. Di Stefano, j. 2004. A confidence interval approach to data analysis. Forest Ecology and Management 187:173-183. Donovan, T. M., E R. Thompson, III, J. Faaborg, and J. R. Probst. 1995. Reproductive success of mi- gratory birds in habitat sources and sinks. Con- servation Biology 9:1380—1395. Duguay, j. P, P. Bohall Wood, and J. V. Nichols. 2001. Songbird abundance and avian nest survival rates in forests fragmented by different silvicul- tural treatments. Conservation Biology 15:1405- 1415. Flaspohler, D. j., S. a. Temple, and R. N. Rosen- FiELD. 2001. Species-specific edge effects on nest success and breeding bird density in a forested landscape. Ecological Applications 11:32-46. Germaine, S. S., S. H. Vessey, and D. E. Capen. 1997. Effects of small forest openings on the breeding bird community in a Vermont hardwood forest. Condor 99:708-718. Gram, W. K., P. A. Porneluzi, R. L. Clawson, J. Faa- borg, AND S. C. Richter. 2003. Effects of exper- imental forest management on density and nesting success of bird species in Missouri Ozark forests. Conservation Biology 17:1324-1337. Hanski, I. K., T. J. Fenske, and G. J. Niemi. 1996. Lack of edge effect in nesting success of breeding birds in managed forest landscapes. Auk 1 13:578- 585. Hensler, G. L. and j. D. Nichols. 1981. The Mayfield method of estimating nesting success: a model, estimators and simulation results. Wilson Bulletin 93:42-53. Hines, J. E. and J. R. Sauer. 1989. Program CON- TRAST: a general program for the analysis of sev- eral survival or recovery rate estimates. Wildlife Technical Report 24, U.S. Fish and Wildlife Ser- vice, Washington, D.C. Holland, L, G. Rope, and D. Anderson. 1990. For- ests and forestry. Interstate, Danville, Illinois. Hoover, J. P. and M. C. Brittingham. 1993. Regional variation in brood parasitism of Wood Thrushes. Wilson Bulletin 105:228-238. Hoover, J. P, M. C. Brittingham, and L. J. Good- rich. 1995. Effects of forest patch size on nesting success of Wood Thrushes. Auk 112:146—155. Hosmer, D. W. and S. Lemeshow. 1989. Applied lo- gistic regression. John Wiley and Sons, New York. James, F. C., D. A. Wiedenfeld, and S. E. Mc- Culloch. 1992. Trends in breeding populations of warblers: declines in the southern highlands and increases in the lowlands. Pages 43—56 in Ecology and conservation of Neotropical migrant landbirds (J. M. Hagan and D. W. Johnston, Eds.). Smith- sonian Institution Press, Washington, D.C. Johnson, D. H. 1979. Estimating nest success: the Mayfield method and an alternative. Auk 96:651- 661. Johnson, G. D., J. L. Pebworth, and H. O. Krueger. 1991. Retention of transmitters attached to pas- serines using a glue-on technique. Journal of Field Ornithology 62:486-491. King, D. I. and R. M. DeGraaf. 2004. Effects of group-selection opening size on the distribution and reproductive success of an early-successional shrubland bird. Forest Ecology and Management 190:179-185. King, D. L, R. M. DeGraf, and C. R. Grifhn. 2001. Productivity of early successional shrubland birds in clearcuts and groupcuts in an eastern deciduous forest. Journal of Wildlife Management 65:345- 350. Litvaitis, j. a. 1993. Response of early-successional vertebrates to historic changes in land use. Con- servation Biology 7:866-873. Manolis, j. C., D. E. Anderson, and E J. Cuthbert. 2000. Patterns in clearcut edge and fragmentation effect studies in northern hardwood-conifer land- scapes: retrospective power analysis and Minne- sota results. Wildlife Society Bulletin 28:1088— 1101. Martin, T. E. and G. R. Geupel. 1993. Nest-monitor- ing plots: methods for locating nests and moni- toring success. Journal of Field Ornithology 64: 507-519. Martin, T. E., C. R. Payne, C. J. Conway, W. M. Hochachka, P. Allen, and W. Jenkins. 1997. BBIRD field protocol. Cooperative Wildlife Re- search Unit, University of Montana, Missoula. Mayfield, H. F. 1975. Suggestions for calculating nest success. Wilson Bulletin 87:456—466. Minitab, Inc. 1998. Minitab user’s guide: release 12 for Windows. Minitab, Inc., State College, Penn- sylvania. Ricketts, M. S. and G. Ritchison. 2000. Nesting suc- cess of Yellow-breasted Chats: effects of nest site and territory vegetation structure. Wilson Bulletin 112:510-516. Robinson, S. K., F. R. Thompson, III, T. M. Donovan, D. R. Whitehead, and J. Faaborg. 1995. Re- gional forest fragmentation and the nesting suc- cess of migratory birds. Science 267:1987-1990. Robinson, W. D. and S. K. Robinson. 1999. Effects of selective logging on forest bird populations in a fragmented landscape. Conservation Biology 13:58-66. Rodewald, a. D. 2002. Nest predation in forested re- gions: landscape and edge effects. Journal of Wildlife Management 66:634-640. Rodewald, P. G. and K. G. Smith. 1998. Short-term effects of understory and overstory management Alterman et al. • USE OF GROUP-SELECTION AND SEED-TREE CUTS 363 on breeding birds in Arkansas oak-hickory forests. Journal of Wildlife Management 62: 141 1-1417. Sauer, J. R., J. E. Hines, and J. Fallon. 2001. The North American Breeding Bird Survey: results and analysis 1966-2000, ver. 2001.2. USGS Pa- tuxent Wildlife Research Center, Laurel, Mary- land. http://www.mbr-pwrc.usgs.gov/bbs/bbs.html (accessed 15 October 2002). Smith, D. M. 1986. The practice of silviculture. John Wiley and Sons, New York. Thill, R. E. and N. E. Koerth. 2005. Breeding birds of even- and uneven-aged pine forests of eastern Texas. Southeastern Naturalist 41:153-176. Thompson, E R., Ill, J. R. Probst, and M. G. Rapha- el. 1995. Impacts of silviculture: overview and management recommendations. Pages 201-219 in Ecology and management of Neotropical migra- tory birds (T. E. Martin and D. M. Finch, Eds.). Oxford University Press, New York. Twedt, D. j., R. R. Wilson, J. L. Henne-Kerr, and R. B. Hamilton. 2001. Nest survival of forest birds in the Mississippi Alluvial Valley. Journal of Wildlife Management 65:450-460. Woodward, A. A., A. D. Fink, and E R. Thompson, III. 2001. Edge effects and ecological traps: ef- fects on shrubland birds in Missouri. Journal of Wildlife Management 65:668-675. Wilson Bulletin 1 17(4):364-374, 2005 FLIGHT SPEEDS OF NORTHERN PINTAILS DURING MIGRATION DETERMINED USING SATELLITE TELEMETRY MICHAEL R. MILLER, '•= JOHN Y. TAKEKAWA,^ JOSEPH P. FLESKES,' DENNIS L. ORTHMEYER,’-'* MICHAEL L. CASAZZA,' DAVID A. HAUKOS,^ AND WILLIAM M. PERRY' ABSTRACT. Speed (km/hr) during flight is one of several factors determining the rate of migration (km/ day) and flight range of birds. We attached 26-g, back-mounted satellite-received radio tags (platform transmitting terminals; PTTs) to adult female Northern Pintails {Anas acuta) during (1) midwinter 2000-2003 in the northern Central Valley of California, (2) fall and winter 2002-2003 in the Playa Lakes Region and Gulf Coast of Texas, and (3) early fall 2002-2003 in south-central New Mexico. We tracked tagged birds after release and, in several instances, obtained multiple locations during single migratory flights (flight paths). We used data from 17 PTT- tagged hens along 21 migratory flight paths to estimate groundspeeds during spring {n = 19 flights) and fall (n = 2 flights). Pintails migrated at an average groundspeed of 77 ±4 (SE) km/hr (range for individual flight paths = 40-122 km/hr), which was within the range of estimates reported in the literature for migratory and local flights of waterfowl (42-116 km/hr); further, groundspeed averaged 53 ± 6 km/hr in headwinds and 82 ± 4 km/hr in tailwinds. At a typical, but hypothetical, flight altitude of 1,460 m (850 millibars standard pressure), 17 of the 21 flight paths occurred in tailwinds with an average airspeed of 55 ± 4 km/hr, and 4 occurred m headwinds with an average airspeed of 71 ±4 kmyOir. These adjustments in airspeed and groundspeed in response to wind suggest that pintails migrated at airspeeds that on average maximized range and conserved energy, and fell within the range of expectations based on aerodynamic and energetic theory. Received 19 November 2004, accepted 6 September 2005. The overall rate at which birds travel during migration, often referred to as migration speed (measured in km/day), includes the time re- quired to accumulate fat reserves and rest pri- or to migration and at stopovers, and the ac- tual time spent in flight during which fat is catabolized (Alerstam and Lindstrom 1990). Flight speed (km/hr) is expressed as ground- speed (velocity with respect to ground) or air- speed (velocity with respect to air); the ratio of groundspeed to airspeed directly measures the effects of wind on the energetic costs of migration (Alerstam 1978, Richardson 1990). This ratio is proportional to migration speed (Alerstam 2003), and can predict the strength * U.S. Geological Survey, Western Ecological Re- search Center, Dixon Field Station, 6924 Tremont Rd., Dixon, CA 95620, USA. 2 U.S. Geological Survey, Western Ecological Re- search Center, San Francisco Bay Estuary Field Sta- tion, 505 Azuar Dr., Vallejo, CA 94592, USA. 3 U.S. Fish and Wildlife Service, Dept, of Range, Wildlife, and Fisheries Management, Texas Tech Univ., Lubbock, TX 79409, USA. ^ Current address: California Waterfowl Association, 4630 Northgate Blvd., Ste. 150, Sacramento, CA 95834, USA. ^ Corresponding author; e-mail: michaeLr_miller@usgs.gov of migration (the number of birds aloft; Rich- ardson 1990). For many birds, migration speed may be controlled largely by the time required to acquire fat reserves at stopovers (Alerstam 2003). However, Liechti and Bru- derer (1998) concluded that for birds making long nonstop flights, selection of favorable tailwinds to boost groundspeed and save en- ergy (fat) is more important than timing de- parture based on the rate of fat accumulation. Birds in headwinds, for example, may lower flight altitude until wind velocity declines, thereby increasing groundspeed and conserv- ing energy (Kerlinger and Moore 1989). Birds migrate at groundspeeds that reflect, among other things, airspeed in the presence or absence of tailwinds or headwinds (Rich- ardson 1990, Alerstam 2003) and aerodynam- ic characteristics of the species (Pennycuick 1975, Rayner 1990). Aeronautical flight me- chanics and bioenergetics theory suggest that birds should fly at one of two characteristic airspeeds during migration. The first minimiz- es energy cost per unit of time to remain air- borne as long as possible (minimum powei speed; V^^), and the second minimizes the en- ergy cost per unit of distance flown to maxi- mize distance over the ground with a certair fuel load (maximum range speed; Vny.) (Tuckei 364 Miller et al. • PINTAIL FLIGHT SPEED 365 and Schmidt- Koenig 1971, Alerstam and Hed- enstrom 1998). A third conceptual speed, which is not as well defined (Bruderer and Boldt 2001), minimizes total duration of the migration by maximizing overall speed (min- imum time speed; however, in practice it is rarely separable from (Alerstam and Hedenstrom 1998, Hedenstrom and Alerstam 1998). In general, waterfowl are well designed for relatively rapid long-distance migration (Rayner 1988), and the moderately sized Northern Pintail {Anas acuta), in particular, features an aerodynamic design (streamlined shape, long narrow wings) that supports effi- cient long-distance flight (Pennycuick 1975, Bellrose 1980, Bruderer and Boldt 2001). However, it is not known whether pintails mi- grate with flight speeds that adhere to theo- retical models. Investigators have used satellite telemetry to estimate the groundspeeds of migrating swans (Cygnus spp.; Pennycuick et al. 1996a, Ely et al. 1997) and Brant {Branta bernicla; Green et al. 2002), but we found no such information for ducks. A recent pro- ject to track migration of adult female pin- tails outfitted with satellite-receiving radio tags (platform transmitting terminals; PTTs) in California, Texas, and New Mexico win- tering regions (Miller et al. 2001, 2005) pro- vided an opportunity to directly estimate groundspeed. By using archived speeds and directions of winds at a typical waterfowl migration altitude, we then determined their potential airspeed and compared it with the- oretical values of and (Bruderer and Boldt 2001). METHODS We captured pintails at the following times and locations: (1) December-January 2000- 2003 in California at Sacramento Valley na- tional wildlife refuges (NWR) and state wild- life areas (central location: 39° 24' N, 121° 58' W); (2) November-Janiiary 2001-2002 in the Playa Lakes Region of Texas at Buffalo Lake NWR (34° 54' N, 102° 7' W) and on pri- vate lands (33° 46' N, 101° 51' W), and along the Texas Gulf Coast on a unit of Aransas NWR (28° 33' N, 96° 33' W) and on private lands (27°20'N, 97°48'W); and (3) Octo- ber—November 2(K)1— 2002 in New Mexico at Bosque del Apache NWR (33°48'N, 106° 51' W). These areas are located in important pintail wintering or fall staging regions (Bell- rose 1980). We tagged only adult female pintails be- cause of their critical role in population dy- namics (Flint et al. 1998). We sorted all hens by sex and age (Carney 1992), attached fed- eral leg bands, and obtained body mass (±5 g). We used Model 100 PTTs from Microwave Telemetry, Inc. (Columbia, Maryland), and annually attached 25-55 on females in Cali- fornia, 20 in Texas, and 6-9 in New Mexico. The units, with harness and protective neo- prene pad, weighed about 26 g, which was 2. 7-3. 2% of average body mass at capture in California (900-950 g), Texas (820-920 g), and New Mexico (935-975 g), well under commonly used guidelines (Caccamise and Hedin 1985). We attached each PTT dorsally between the wings by fashioning a harness of 0.38-cm-wide (sold as 3/16 in) Teflon ribbon (Bally Ribbon, Bally, Pennsylvania). The completed harness included fore and aft body loops connected with a 1-cm-length of ribbon over the keel, similar to designs used by Ma- lecki et al. (2001). Ours, however, consisted of a single length of ribbon without metal clips, buckles, shrink-tubing, or sewed areas, and we hardened knots with cyanoacrylate glue. We released tagged hens at trap sites 5- 19 hr after capture — either during evening pintail flights or at night. To encompass spring migration, we pro- grammed PTTs to last 6-8 months by using a repeating duty cycle consisting of a 5- to 6-hr transmission period followed by a 72-hr rest- ing period; some PTTs lasted long enough to provide data during fall migration. We used the Argos location and data collection system (Argos, Inc. 1996), including multi-satellite service with standard and auxiliary location processing, to monitor the locations of PTT- tagged pintails. Argos estimates PTT locations from the Doppler shift in transmission fre- quency received by satellites as they approach and then mcwe away from the PTT. Argos checks the plausibility of locations via (1) minimum residual crnn; (2) transmission fre- quency continuity, (3) shortest distance cov- ered since previous location, and (4) plausi- bility ol velocity between locations. The num- ber of positive checks (NOPC; 0-4) is includ- ed with each location received via daily 366 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 e-mails. The PTTs also provided sensor data to index the unit’s temperature, remaining voltage, and motion. We used these, especially the latter, to determine whether birds were alive and to verify that they were flying. Argos classifies each PTT location based on estimated accuracy and the number of trans- missions (messages) received from each PTT during a satellite overpass. The classes of lo- cation quality (LC 3, LC 2, LC 1, LC 0) are based on >4 messages received by the satel- lite via standard data processing; respective accuracies are <150, 150-350, 350-1,000, and >1,000 m. Accuracy is expressed as the probability that 67% of the locations will fall within stated limits; therefore, high-quality lo- cations might be inaccurate, while lower-qual- ity locations might be very accurate (Hatch et al. 2000). Argos does not estimate accuracy of LC A (3 messages received), LC B (two messages received), or LC Z (latitude/longi- tude often provided if >1 message received), which are received via auxiliary processing; however, field tests have shown that LC A can be as accurate as LC 0 or LC 1 (Britten et al. 1999, Hays et al. 2001), and LC B can be as accurate or better than LC 0 (Hatch et al. 2000, Hays et al. 2001). Therefore, the accu- racy of individual points along a flight path likely varies, even among those of the same LC (Hatch et al. 2000). If a PTT-tagged bird is stationary (not flying), several criteria are normally used to choose one best location from among the many normally provided by Argos (Ely et al. 1997, Butler et al. 1998, Pe- tersen et al. 1999, Hatch et al. 2000). Because of continuous forward travel, however, Argos cannot provide alternate points at each loca- tion for pintails in migratory flight. Therefore, we initially plotted all locations of birds in flight and subsequently examined each of them in detail to determine flight paths. We analyzed and displayed location data using Arcinfo and ArcView Geographic In- formation System software (Environmental Systems Research Institute, Redlands, Cali- fornia). Eor each female, we plotted individual flight paths using all PTT locations acquired while the bird was flying. Each flight path consisted of segments formed by successive pairs of adjacent location points (e.g., a path formed by five points would have four flight- path segments). We used only locations re- corded during pintail migratory flights — iden- tified from multiple locations of birds heading generally northerly or southerly during a sin- gle transmission period — concurrently with PTT motion sensor data that suggested vig- orous activity. Additionally, we used only lo- cations >200 km from the location recorded on the previous or subsequent (or both) loca- tion-days; these criteria precluded inadver- tently including stationary pintails or those making only local flights. We selected only those points that best de- fined the flight path, and deleted those that deviated from the general line of flight, re- versed direction, occurred in clusters (indicat- ing a stationary bird), occurred too close to- gether in space and time, or represented movement too fast or too slow between points — especially if LC was A or worse (Hatch et al. 2000 used LC 0). For example, we considered a given point to be an obvious outlier from the general line of flight if the perpendicular distance from the flight line was greater than the average error distance from true position as determined for the least ac- curate LCs in recent field tests of PTTs (i.e., 7.5 km for LC 0 and LC A, and 23-35 km for LC B [Blouin et al. 1999, Britten et al. 1999]; 20 km for LC A and LC B [Hatch et al. 2000]; 1-10 km for LC 0 and LC A, and 7 km for LC B [Hays et al. 2001]). We also considered points to be outliers if the time be- tween location points along the path was <10 min and the distances between them <20 km, unless this was typical along the flight path and produced similar intervening ground- speeds among segments. We rejected one of two points that created sharp-angled direction changes (usually >45°) and reversals. Addi- tionally, we questioned the accuracy of indi- vidual locations if the groundspeed along path segments seemed biologically impossible. We defined this as (1) >160 km/hr, the speed of a Red-breasted Merganser (Mergus serrator) flying with a 32 km/hr tailwind, while being chased by a small aircraft (Thompson 1961), or (2) <20 km/hr when point separation was <20 km, unless intervening groundspeeds matched those between other more widely separated points along the path. These criteria are somewhat arbitrary, but provided a con- sistent method for selecting and rejecting lo- cations— similar to procedures used by Hatch Miller et al. • PINTAIL FLIGHT SPEED 367 et al. (2000), in which they discarded loca- tions “conspicuously outside” clusters of points (stationary birds) because they violated their redundancy rule. We estimated apparent groundspeeds along each outlier-corrected flight path by summing the total time (hr) and distance (km) of each flight-path segment, and then dividing total distance over the flight path by total time from the first to the last accepted location point. We used multiple flight paths from individual tagged hens, if available, and estimated groundspeed as mean ± SE for all flights. For comparison, we also estimated groundspeed for all flights using all recorded locations (out- liers retained) to recognize our uncertainty with the deletions and determine how our cri- teria may have affected final groundspeed es- timates. We wanted to determine reliable airspeeds for PTT-tagged pintails, but wind speeds in- crease and their directions change markedly with increasing altitude (Kerlinger and Moore 1989, Ahrens 2000); in addition, we did not know at what altitudes our tagged ducks mi- grated (our PTTs did not have altitude sen- sors). We had no means to predict when or where measurable flight paths would occur, and as a result, we could not a priori deploy radar and weather balloons to obtain ground- speed, wind speed, wind direction, and flight altitude simultaneously, as done when birds pass predictable locations (Bruderer and Boldt 2001). Therefore, to assess the effect of head- winds or tailwinds along the 21 pintail flight paths, we assumed migration altitudes of sea level and 1 ,460 m above sea level ( 1 ,000 and 850 millibars [mb] at standard pressure; Ah- rens 2000), which is within the typical range used by migrating waterfowl (Kerlinger and Moore 1989, Berthold 1996), and for which archived weather data were readily available. The higher altitude was used by Dau (1992), wShamoun-Barancs et al. (2003), and Gill et al. (2005) to examine migration of Brant, White Storks (Ciconia ciconia), and Bar-tailed God- wits (Limosa lapponica), respectively. We ob- tained wind speed and direction on the dates of pintail flights using North American Con- stant Pressure weather charts (850 mb) for ()():()() UTC and 12:00 UTC, published by the National Center for Environmental Prediction (NCEP; National Climatic Data Center 2005). We assumed that the weather charts repre- sented conditions at the location of flying pin- tails, and we used wind speeds and directions nearest to each pintail flight path (Shamoun- Baranes et al. 2003). Because exact flight al- titudes remained unknown, we did not add un- justified precision to the generally imperfect data to account for the angle at which tail- winds or headwinds may have intercepted pin- tail flight paths (Gill et al. 2005). Instead, we assumed that tailwinds and headwinds essen- tially paralleled flight paths, and ignored com- pensation and drift (Wege and Raveling 1984, Alerstam and Hedenstrom 1998). We calcu- lated airspeeds either as (1) groundspeed — tailwind or (2) groundspeed + headwind. To characterize migration conditions at the sur- face, we obtained archived sky conditions and surface wind speed and direction at the time of flights from weather stations nearest the flight paths (Weather Underground 2005). RESULTS During 2001, 2002, and 2003, we obtained 21 flight paths of 17 PTT-tagged pintails for which we estimated groundspeeds (Fig. 1). Of this total, 19 flights from 16 pintails occurred during spring, and 2 flights from 2 birds oc- curred during fall (1 hen provided 1 spring and 1 fall flight; Table 1). These data included 14 pintails tagged in California, 2 in Texas, and 1 in New Mexico. We used all original Argos locations from 10 pintail flight paths (uncorrected), but deleted >1 location from each of 1 1 others (outlier-corrected), because they did not meet our established criteria. Out- lier correction resulted in increases in ground- speed of 4-21 km/hr for five flight paths, de- creases in speed of 1-69 km/hr for five flight paths, and no change for one flight path. Out- lier correction reduced our total number of lo- cations from 108 to 77. Correction for outliers did not markedly increase the proportion of high-quality locations forming flight paths compared with that in the uncorrected data set. For example, the proportion of LC 1 and LC 2 locations increased to 17% from 12% of all locations, and those (4' LC A, B, and Z declined to 25% from 32% (no change in pro- portion of LC 0). When we used the 1 I outlier-corrected flights and the 10 uncorrected flights, ground- speeds of pintails along all 21 flight paths 368 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 FIG. 1. Migration flight paths and path segments of adult female Northern Pintails PTT-tagged in California, Texas, and New Mexico, used to estimate groundspeed and airspeed (km/hr), 2001-2003. Circled uppercase letters are bird identifiers from Tables 1, 2. Thick black lines show the measured flight paths divided into segments by open circles representing pintail locations. Thin gray lines show migration routes prior and sub- sequent to the measured path. ranged from 40 to 122 km/hr (Table 1) and averaged 77 ± 4 km/hr (CV = 5.6, 90% Cl — 69-84). Two-thirds of the speeds (14 of 21 flight paths) occurred over a narrower range of 61-80 km/hr. Without omitting outliers. groundspeeds ranged from 45 to 111 km/hr and averaged 78 ± 4 km/hr (CV = 4.9, Cl = 72-84), indistinguishable from the outlier-cor- rected value. Groundspeed averaged 75 ± 4 km/hr (CV - 4.6, Cl - 70-81) for the 10 Miller et al. • PINTAIL FLIGHT SPEED 369 TABLE 1 . Outlier-corrected groundspeeds of adult female Northern Pintails, including start and end times, distance flown, and time in flight, along flight paths determined via satellite telemetry, 2001-2003. All times are Pacific Standard Time, except as noted. Bird identifiers (uppercase letters) correspond to those in Figure 1. Year Start date Bird Location of flight («i, «2)^ Start-end times Distance flown (km) Time in flight (hr) Ground speed (km/hr) 2001 21 Mar A West-central Idaho (4, 4) 04:15-08:42^ 288.7 4.45 65 2001 25 Apr B West of Washington/British Columbia (8, 6) 03:55-09:23 393.3 5.45 72 2001 27 Apr C Northeastern Alberta (10, 5) 04:29-07:58® 267.4 3.49 77 2001 27 Apr D Western Alberta (4, 4) 19:31-00:38® 511.4 5.12 100 2001 3 May E West of Washington/Oregon (4, 4) 02:30-06:23 309.2 3.90 79 2002 23 Feb F Northern California (8, 3) 17:05-20:06 212.6 3.13 68 2002 20 Mar G Southern Idaho (4, 3) 01:09-03:42® 294.4 2.55 116 2002 21 Mar Eastern Oregon to western Idaho (3, 3) 19:55-23:57® 257.8 4.03 64 2002 13 Apr I North Dakota (10, 5) 15:54-19:52^ 180.1 2.28 79 2002 19 Apr J British Columbia coast (7, 4) 02:20-07:13 216.3 4.89 44 2002 21 Apr West of Washington/British Columbia (8, 5) 11:51-15:46 157.6 3.91 40 2002 24 Apr L“ Western Oregon/ocean (3, 3) 23:17-01:25 292.7 3.79 77 2002 25 Apr M Eastern Texas (3, 3) 20:41-22:20^ 218.3 3.06 71 2002 8 May Nb Central Alberta (3, 3) 21:08-22:49® 206.1 3.36 62 2002 9 May O Central Oregon (2, 2) 21:35-23:14 127.4 1.66 77 2002 14 May pb Southeastern Yukon (9, 5) 09:08-10:48 366.4 3.01 122 2002 26 May West-central British Columbia (4, 3) 22:47-02:15 277.3 3.46 80 2002 10 Oct Western Oregon/ocean (3, 2) 21:38-23:16 99.8 1.64 61 2002 12 Nov S Southern New Mexico to Mexico (6, 5) 18:49-22:17® 428.1 4.51 95 2003 19 Mar T Northeastern Oregon (2, 2) 01:07-02:46 135.3 1.66 82 2003 31 Mar U Eastern Oregon (3, 3) 19:28-22:39 243.1 3.19 76 = total number of separate location points recorded during flight and used to estimate groundspeed without correcting for outliers; nj = number of accepted location points used to estimate outlier-corrected groundspeed. Superscripts of the same letter indicate multiple flights for the same pintail. ® Mountain Standard Time. ^ Central Standard Time. uncorrected flights, 78 ± 8 km/hr (CV = 10.1, Cl = 65-90) for the 1 1 outlier-corrected flights, and 80 ± 7 km/hr (CV = 8.4, Cl = 69-91) for the 1 1 flights when not corrected for outliers. Most (19 of 21) flights occurred partially or entirely at night (Table 1 ), and two paths transited land and sea (Fig. 1). Based on wind speeds and directions at 1,400 m (850 mb), 17 of the 21 flights (81%) occurred in tailwinds and four in headwinds (Table 2). Groundspeeds averaged 82 ± 4 km/hr (CV = 8.2, Cl = 75—89) in tailwinds and 53 ± 6 km/hr (CV = 1 1.8, Cl = 43-63) in headwinds. Three of the four flights that occurred in headwinds at 850 mb (birds A, J, and K; Table 2) would have had tailwinds near the ground surface of 6-13, 7-11, and 13-15 km/hr, respectively (weather station data), and the fourth flight (bird N) would have had headwinds of 6-9 km/hr. Corre- sponding airspeeds of pintails at 850 mb ranged from 24 to 97 km/hr in tailwinds and from 59 to 80 km/hr in headwinds (Table 2), with means of 55 ± 4 km/hr (CV = 7.9, Cl = 48-62) in tailwinds and 71 ± 4 km/hr (CV = 6.2, Cl = 64-78) in headwinds. The ratios of groundspeed to airspeed averaged 0.73 ± 0.6 in headwind (CV = 8.2, Cl = 0.63-0.83) and 1.61 ±0.14 in tailwind (CV = 8.5. Cl = 1.39-1.83). riie longest distance flown by a pintail for which we estimated groundspeed (bird B), was 2,926 km — from Goo.se Lake in southern Oregon (42° 15' N, 120° 23' W) to the Kenai Peninsula in Alaska (59°12'N, 151°46'W; Fable 1). Assuming that pintails flew at the 370 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 TABLE 2. Airspeeds of adult female Northern Pintails estimated using satellite telemetry and supporting wind speed and direction data from North American Constant Pressure weather charts (850 millibars or 1,460 m), 2001-2003. Local sky and surface wind direction categories at weather stations nearest to flight paths are also given. Bird identifiers (uppercase letters) correspond to those in Figure 1. Year Date Bird Ground- speed (km/hr)^ Highest wind speed (km/hr)'^ Wind direction (compass)'^ Wind category‘s Airspeed (km/hr)^* Local sky conditions; surface wind category^ 2001 21 Mar A 65 9 NW QHW 74 MC; QTW' 2001 25 Apr B 72 37 ssw QTW 35 OC; QHW2 2001 27 Apr C 77 19 ssw QTW 58 OC; QTW3 2001 27 Apr D 100 28 ssw QTW 72 MC; none'' 2001 3 May E 79 46 ssw QTW 33 PC; QTW2 2002 23 Feb F 68 19 SSE TW 49 OC; VAR5 2002 20 Mar G 116 19 w TW 97 CL; QTW6 2002 21 Mar Hf 64 28 SW QTW 36 CL; QHW" 2002 13 Apr I 79 28 SW QTW 51 PC; TW^ 2002 19 Apr J 44 28 WNW QHW 72 MC; QTW9 2002 21 Apr Kg 40 19 NNW, N HW 59 LR; QTW'« 2002 24 Apr Lh 77 19 SW QTW 58 CL; VAR" 2002 25 Apr M 71 28 WSW, SW QTW 43 MC; QHW'2 2002 8 May Nf 61 19 N HW 80 OC; HW^ 2002 9 May O 77 9 SE TW 68 OC; HW'3 2002 14 May P' 122 56 SE TW 66 LR; QTW'^ 2002 26 May Qg 80 56 SSE TW 24 LR; QTW'5 2002 10 Oct Rh 61 9 NW, NNW TW 52 OC; none" 2002 12 Nov S 95 28 NNW, N QTW 67 CL; QTW'^ 2003 19 Mar T 82 19 SSW TW 63 CL; QTW'" 2003 31 Mar U 76 9 SW QTW 67 R; QTW'« ^ Values rounded to nearest km/hr from Table 1 . h Wind speeds and compass directions obtained from airspeed/direction symbols on 850 mb constant pressure weather charts nearest pintail flights. Symbols for relative wind direction category apply to upper air and surface data: Q = quartering, TW = tailwind, HW = headwind, SW = sidewind, VAR = variable, none = calm. Airspeed = groundspeed - tailwind, or groundspeed + headwind; wind speed used is the highest of the ranges obtained from weather charts, e Sky conditions: OC = overcast, LR = light rain, R = rain, MC = mostly cloudy, PC = partly cloudy, CL = clear; where >1 condition applied, we show the condition least favorable for migration. Numbered superscripts refer to the nearest weather station: 1 = Boise, Idaho; 2 = Hoquiam, Washington; 3 = Fort Smith, Northwest Territories; 4 = Edmonton, Alberta; 5 = Redding, California; 6 = Burley, Idaho; 7 = Ontario, Oregon; 8 = Jamestown, North Dakota; 9 = Vancouver, British Columbia; 10 = Quillayute, Washington; 11 = Newport, Oregon; 12 = College Station, Texas; 13 = Redmond, Oregon; 14 = Watson Lake, Yukon; 15 = Terrace, British Columbia; 16 = Truth or Consequences, New Mexico; 17 = Hermiston, Oregon; 18 = Bums, Oregon. Superscripts of the same letter indicate multiple flights for the same pintail. average outlier-corrected groundspeed of 77 km/hr, they would have required 38 hr to com- plete the flight nonstop. DISCUSSION The estimated 77 km/hr migration ground- speed of PTT-tagged adult female pintails was consistent with that of the upper range of pin- tail groundspeeds (local flights) estimated us- ing radar (65-76 km/hr; Bruderer and Boldt 2001). Average groundspeeds of other ducks during local flights have ranged from 42 to 116 km/hr (Speirs 1945, Lokemoen 1967, Kerlinger 1995, Bruderer and Boldt 2001), very similar to the range we obtained for mi- grating pintails. During migration, PTT-tagged Whooper (Cygnus cygnus) and Tundra (C. columbianus) swans migrated at 60-90 km/hr (Pennycuick et al. 1996a, Ely et al. 1997), and Canada Geese (Branta canadensis) fitted with VHP radio-transmitters migrated at ground- speeds of 49-110 km/hr (Wege and Raveling 1984). Bellrose and Crompton (1981) clocked migrating Canada Geese at 61-73 km/hr. Lesser Snow Geese {Chen caerulescens) at 67-83 km/hr, and Mallards {Anas platyrhyn- chos) at 72 km/hr by following in automobiles or aircraft. Using satellite telemetry, radar, and other means, migrating Brant have been re- corded at groundspeeds of 99 km/hr (Dau 1992), 90 km/hr (Lindell 1977 cited in Eb- binge and Spaans 1995), 30—115 km/hr (Green and Alerstam 2000), and 58-109 km/ hr (Green et al. 2002). Wide interspecific var- iation in these reported groundspeed estimates probably resulted from species-specific flight aerodynamics (Pennycuick 1975, Rayner 1990), atmospheric conditions (Kerlinger and Miller et al. • PINTAIL FLIGHT SPEED 371 Moore 1989), and errors associated with the various methods (Bruderer and Boldt 2001). The relatively wide range of pintail ground- speeds in our study undoubtedly reflected pri- marily wind conditions, and perhaps angle of flight (ascending, descending, horizontal; Green and Alerstam 2000); however, the close agreement between outlier-corrected and un- corrected data suggests that measurement er- ror was minimal. We recommend that inves- tigators report groundspeeds and groundspeed to airspeed ratios because of their implication in analysis of flight range and cost. Birds use tailwinds to minimize the ener- getic cost of migration by increasing ground- speed and range, reducing airspeed to main- tain groundspeed, or both (Richardson 1990, Alerstam and Hedenstrom 1998), and this has been verified for migrating waterfowl (Blok- poel 1974, Bellrose and Crompton 1981, Wege and Raveling 1984, Dau 1992, Green et al. 2002). Most pintails (had they migrated at our specified altitude of 1,460 m) would have benefited from tailwinds, as exemplified by their average higher groundspeed and lower airspeed in tailwinds. Birds are known to alter flight altitudes and move to those with favor- able winds (Gauthreaux 1991). If three of the four pintails in our study that we assumed were flying into headwinds aloft had instead been flying near the ground surface, they would have had tailwinds. Also, the three flights occurred partially or completely during the day (Table 1 ), when low-altitude migration flights are typical (Richardson 1990). How- ever, we cannot be sure of the migration alti- tude, and sky conditions observed from the ground varied from mostly cloudy to light rain and overcast (Table 2), weather types that tend to discourage migration (Richardson 1990). Birds generally adjust airspeed when wind direction changes; waterfowl increase air- speed to compensate for headwinds and re- duce airspeed as tailwinds increase (Tucker and Schmidt-Koenig 1971, Bellrose and Crompton 1981, Wege and Raveling 1984, Pennycuick et al. 1996a), but the adjustments are not necessarily proportionate (Bellrose and Crompton 1981). Our pintails clearly did not have a strategy to maintain airspeeds in changing wind conditions (Table 2), although Blokpoel (1974) concluded that migrating Lesser Snow Geese did. Our estimates of av- erage pintail airspeed support the hypothesis that their airspeed was faster, and groundspeed slower, in headwinds compared with tail- winds. The ratios of groundspeed to airspeed for tagged pintails show that compared with still air (ratio = 1.0), pintails decreased their groundspeeds about 27% in headwinds and in- creased groundspeeds by about 61% in tail- winds, suggesting that migration occurred at Vmr- Demonstrating such compensation during local flights. Tucker and Schmidt-Koenig (1971) reported a pintail airspeed of 56 ± 1 km/hr with tailwinds and 66 ± 1 km/hr against headwinds, similar to our results (55 and 71 km/hr, respectively). Because Tucker and Schmidt-Koenig (1971) did not report re- spective groundspeeds or wind directions, we estimated groundspeeds from their study by using their reported average wind speeds of 18 and 31 km/hr and applying them as tail- winds and headwinds. This produced potential respective groundspeeds of 74 and 87 km/hr in tailwinds and 48 and 35 km/hr in head- winds, similar to our findings. Using the theoretical flight models of Pen- nycuick (1989) and Rayner (1990), Bruderer and Boldt (2001) calculated and for pintails as 64 and 40 km/hr, respectively. The average airspeed of our pintails in tailwinds (55 km/hr) was above V^p and below and their average airspeed in headwinds (71 km/ hr) was greater than both V^p and In four instances, our pintails flew more slowly than in tailwinds (24-36 km/hr), and on nine flight paths in variable wind directions, they flew faster than (66-97 km/hr); on eight paths, pintails flew at speeds between the the- oretical speeds (43-63 km/hr; Table 2). Our data support Welham’s (1994) findings that pintail-sized birds tend to migrate at but are not bound by theoretical flight models (Pennycuick 1998); more data are needed to compare field results with their predictions. The four excessively slow speeds in tailwinds ( 0) by increasing PTT power, or, for large species, adopt new PTT models that in- corporate global positioning systems (GPS; Microwave Telemetry, Inc. 2005). This would improve estimation of groundspeeds and air- speeds and their precision along individual flight-path segments. Back-mounted PTTs may have reduced our estimates of pintail groundspeed; however, re- sults from previous studies that addressed this issue have been inconclusive. For example, Butler et al. (1998) estimated a potential 5% increase in the energetic costs of flight of Bar- nacle Geese {Branta leucopsis) outfitted with 33-g PTTs. Because geese are able to reposi- tion PTTs under their body feathers while preening (Butler et al. 1998), wind resistance due to PTTs may be reduced (Obrecht et al. 1988). Harnessed transmitters increased the energy cost of rapid flight in homing pigeons (Rock Pigeon, Columba livia\ Gessaman and Nagy 1988), perhaps due to the vertically flat- tened posterior ends of the test transmitters (Obrecht et al. 1988). In wind tunnel experi- ments that tested the aerodynamic character- istics of three transmitter sizes attached to fro- zen Lesser Snow Geese and Mallards, stream- lined transmitters created the least drag, and the smallest test transmitters (slightly larger than our 20-g unit [excluding harness]) cre- ated drag too small to be measured (Obrecht et al. 1988); the sloped anterior and posterior ends of our pintail PTTs mimicked the stream- lined shape of these units. Pennycuick et al. (1996b) recently reduced their estimate of body-drag coefficients for flying birds from 0.4 to 0.08, suggesting that drag may not be as important as once thought. Based on this new information and our typical mean groundspeeds and airspeeds of PTT-tagged Miller et al. • PINTAIL FLIGHT SPEED 373 pintails, we conclude that the variation in groundspeed caused by wind direction and speed likely overwhelmed wind resistance and mass effects of PTTs. Nonetheless, we en- courage researchers to develop reliable, im- plantable PTTs for moderately sized water- fowl because of potential aerodynamic bene- fits and reduced energetic costs of flight. ACKNOWLEDGMENTS We thank A. A. Marnell, II, and the Tuscany Re- search Institute for providing all operational funding to support the California work through annual grants to Ducks Unlimited, Inc., Memphis, Tennessee, and supporting grants to the California Waterfowl Associ- ation, Sacramento, California. D. P Connelly, F. A. Reid, and G. L. Stewart secured the funding, and B. D. J. Batt, M. Petrie, and G. S. Yarris managed donated funds. B. D. J. Batt, M. Petrie, D. P. Connelly, F. A. Reid, G. S. Yarris, M. G. Anderson, K. L. Guyn, and D. C. Duncan contributed to project development and other planning. The U.S. Fish and Wildlife Service (Region 2), Texas Parks and Wildlife, and the Playa Lakes Joint Venture provided funding for the Texas and New Mexico work. P. Howey provided technical assistance. P. Blake, D. Campbell, N. M. Carpenter, S. Cordes, C. Dennis, J. G. Mensik, and J. A. Moon lo- cated pintail capture sites. We thank the many field technicians who trapped ducks and assisted with PTT attachment, especially C. Lee, B. Ballard, S. Cordts, J. A. Laughlin, and D. L. Loughman. J. K. Daugherty, S. Burnett, C. J. Gregory, and L. L. Williams managed all satellite data. We thank S. E. Schwarzbach, B. D. J. Batt, B. M. Ballard, R. R. Cox, and three anonymous referees for thorough reviews of the manuscript. LITERATURE CITED Ahrens, C. D. 2000. Meteorology today: an introduc- tion to weather, climate, and the environment. Brook.s/Cole, Pacific Grove, California. Alerstam, T. 1978. Analysis and a theory of visible bird migration. Oikos 30:273-349. Alerstam, T. 2003. Bird migration speed. Pages 253- 267 in Avian migration (P. Berthold, E. Gwinner, and E. Sonnen.schein, Eds.). Springer- Verlag, Ber- lin, Germany. Aler.stam, T. and a. Heden.strom. 1998. The devel- opment of bird migration theory. Journal of Avian Biology 29:343-369. Aler.stam, T. and A. Lind.str()m. 1990. Optimal bird migration: the relative importance of time, energy, and safety. Pages 331—351 in Bird migration (E. Gwinner, Ed.). Springer- Verlag, Berlin, Germany. Argos, Inc. 1996. User's manual. I.iindover, Maryland. http://www.argosinc.com (accessed 10 April 2(K)5). Bellrose, F. C. 1980. Ducks, geese, and swans of North America. Stackpole Books, Harrisburg, Pennsylvania. Bellrose, F. C. and R. C. Cromrion. 1981. Migration speeds of three waterfowl species. Wilson Bulletin 93:121-124. Berthold, P. 1996. Control of bird migration. Chap- man and Hall, London, United Kingdom. Blokpoel, H. 1974. Migration of Lesser Snow and Blue Geese, part 1. Report Series, no. 28, Cana- dian Wildlife Service, Ottawa, Ontario, Canada. Blouin, F, j. F. Giroux, J. Ferron, G. Gauthier, and G. J. Doucet. 1999. The use of satellite telemetry to track Greater Snow Geese. Journal of Field Or- nithology 70:187-199. Britten, M. W., P. L. Kennedy, and S. Ambrose. 1999. Performance and accuracy evaluations of small satellite transmitters. Journal of Wildlife Management 63:1349-1358. Bruderer, B. and a. Boldt. 2001. Flight character- istics of birds: I. Radar measurements of speeds. Ibis 143:178-204. Butler, P. J., A. J. Woakes, and C. M. Bishop. 1998. Behaviour and physiology of Svalbard Barnacle Geese Branta leucopsis during their autumn mi- gration. Journal of Avian Biology 29:536-545. Caccamise, D. F. and R. S. Hedin. 1985. An aerody- namic basis for selecting transmitter loads in birds. Wilson Bulletin 97:306-318. Carney, S. M. 1992. Species, age, and sex identifi- cation of ducks using wing plumage. U.S. Fish and Wildlife Service, Washington, D.C. Dau, C. P. 1992. The fall migration of Pacific Fly way Brent Branta bernicla in relation to climatic con- ditions. Wildfowl 43:80-95. Ebbinge, B. S. and B. Spaans. 1995. The importance of body reserves accumulated in spring staging ar- eas in the temperate zone for breeding in dark-bel- lied Brent Geese {Branta bernicla bernicla) in the high Arctic. Journal of Avian Biology 26:105-1 13. Ely, C. R., D. C. Douglas, A. C. Fowler, C. A. Bab- cock, D. V. Derksen, and j. Y. Takekawa. 1997. Migration behavior of Tundra Swans from the Yu- kon-Kuskokwim Delta, Alaska. Wilson Bulletin 109:679-692. Flint, P. L., J. B. Grand, and R. F. Rockwell. 1998. A model of Northern Pintail productivity and pop- ulation growth rate. Journal of Wildlife Manage- ment 62: 1110-1118. Gauthreaux, S. a. 1991. The flight behavior of mi- grating birds in changing wind fields: radar and visual analy.ses. American Zoologist 31:187-204. Ges.saman, j. a. and K. a. Nagy. 1988. Transmitter loads affect the flight speed and metabolism of homing pigeons. Condor 90:662-668. Gill, R. E., Jr., T. Pif:rsma, G. Hufeord, R. Sf-:r- VRANCKX, AND A. Rif:gf:n. 2(H)5. Crossing the ul- timate ecological barrier: evidence for an 1 I OfK)- km-long nonstop flight from Alaska to New Zea- land and eastern Australia by Bar-tailed Godwits. C'ondor 107:1-20. Grfen, M. and T. Alerstam. 2(X)0. Flight speeds and climb rates of Brent Geese: mass-tlependent dif- ferences between spring and autumn migration. Journal of Avian Biology 31:215 225. 374 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Green, M., T Alerstam, P. Clausen, R. Drent, and B. S. Ebbinge. 2002. Dark-bellied Brent Geese Branta bernicla bernicla, as recorded by satellite telemetry, do not minimize flight distance during spring migration. Ibis 144:106-121. Hatch, S. A., P. M. Meyers, D. M. Mulcahy, and D. C. Douglas. 2000. Performance of implantable satellite transmitters in diving seabirds. Waterbirds 23:84-94. Hays, G. C., A. Akesson, B. J. Godley, P. Lushci, AND P. Santidrian. 2001. The implications of lo- cation accuracy for the interpretation of satellite- tracking data. Animal Behaviour 61:1035-1040. Hedenstrom, a. and T. Alerstam. 1998. How fast can birds migrate? Journal of Avian Biology 29: 424-432. Jenni, L. and M. Schaub. 2003. Behavioural and phys- iological reactions to environmental variation in bird migration: a review. Pages 155-171 in Avian migration (P. Berthold, E. Gwinner, and E. Sonnen- schein, Eds.). Springer- Verlag, Berlin, Germany. Kerlinger, P. 1995. How birds migrate. Stackpole Books, Mechanicsburg, Pennsylvania. Kerlinger, P. and E R. Moore. 1989. Atmospheric structure and avian migration. Current Ornitholo- gy 6:109-142. Kvist, a., M. Klaassen, and A. Lindstrom. 1998. Energy expenditure in relation to flight speed: what is the power of mass loss rate estimates? Journal of Avian Biology 29:485-498. Liechti, E and B. Bruderer. 1998. The relevance of wind for optimal migration theory. Journal of Avi- an Biology 29:561-568. Liechti, R. and E. Schaller. 1999. The use of low- level jets by migrating birds. Naturwissenschaften 86:549-551. Lindell, L. 1977. Migratory Brent Geese Branta ber- nicla in south Sweden on 25 September 1976. An- ser 16:146-147. Lokemoen, J. T. 1967. Elight speed of the Wood Duck. Wilson Bulletin 79:238-239. Malecki, R. a., B. D. j. Batt, and S. E. Sheaffer. 2001. Spatial and temporal distribution of Atlantic population Canada geese. Journal of Wildlife Management 65:242-247. Microwave Telemetry, Inc. 2005. Product and servic- es catalogue. Columbia, Maryland. http://www. microwavetelemetry.com (accessed 10 April 2005). Miller, M. R., J. P. Eleskes, J. Y. Takekawa, D. L. Orthmeyer, M. L. Casazza, and W. M. Perry. 2001. Satellite tracking of Northern Pintail spring migration from California, USA: the route to Chu- kotka, Russia. Casarca 7:229-233. Miller, M. R., J. P. Eleskes, J. Y. Takekawa, D. C. Orthmeyer, M. L. Casazza, and W. M. Perry. 2005. Spring migration of Northern Pintails from California’s Central Valley wintering area tracked with satellite telemetry: routes, timing, and destina- tions. Canadian Journal of Zoology 83:1314-1332. National Climatic Data Center. 2005. Upper-air data: data and products, NCEP charts. Asheville, North Carolina, http://www.ncdc.noaa.gov/oa/up- perair.html (accessed 10 April 2005). Obrecht, H. H., C. j. Pennycuick, and M. R. Fuller. 1988. Wind tunnel experiments to assess the effect of back-mounted radio-transmitters on bird body drag. Journal of Experimental Biology 135:265-273. Pennycuick, C. J. 1975. Mechanics of flight. Avian Biology 5:1-75. Pennycuick, C. J. 1989. Bird flight performance: a practical calculation manual. Oxford University Press, Oxford, United Kingdom. Pennycuick, C. J. 1998. Towards an optimal strategy for bird flight research. Journal of Avian Biology 29:449-457. Pennycuick, C. J., O. Einarson, T. A. M. Bradbury, AND M. Owens. 1996a. Migrating Whooper Swans Cygnus cygnus: satellite tracks and flight perfor- mance calculations. Journal of Avian Biology 27: 118-134. Pennycuick, C. J., M. Klaassen, A. Kvist, and A. Lindstrom. 1996b. Wingbeat frequency and the body drag anomaly: wind tunnel observations on a Thrush Nightingale {Luscinia luscinia) and a Teal {Anas crecca). Journal of Experimental Bi- ology 199:2757-2765. Petersen, M. R., W. W. Earned, and D. C. Douglas. 1999. At-sea distribution of Spectacled Eiders: a 120-year mystery resolved. Auk 116:1009-1020. Rayner, j. M. V. 1988. Form and function in avian flight. Current Ornithology 5:1-77. Rayner, J. M. V. 1990. The mechanics of flight and bird migration performance. Pages 283—299 in Bird migration (E. Gwinner, Ed.). Springer- Verlag, Berlin, Germany. Richardson, W. J. 1990. Timing of bird migration in relation to weather: updated review. Pages 78-101 in Bird migration (E. Gwinner, Ed.). Springer- Ver- lag, Berlin, Germany. Shamoun-Baranes, j., A. Baharad, P. Albert, P. Berthold, Y. Yom-Tav, Y. Dvir, and Y. Lesham. 2003. The effect of wind, season and latitude on the migration speed of White Storks Ciconia ci- conia, along the eastern migration route. Journal of Avian Biology 34:97-104. Speirs, j. M. 1945. Flight speed of the Old-squaw. Auk 62:135-136. Thompson, M. C. 1961. The flight speed of a Red- breasted Merganser. Condor 63:265. Tucker, V. A. and K. Schmidt- Koenig. 1971. Flight speeds of birds in relation to energetics and wind directions. Auk 88:97—107. Weather Underground. 2005. Weather station histo- ries. Ann Arbor, Michigan. http://www. weatherunderground.com (accessed 10 April 2005). Wege, M. L. and D. G. Raveling. 1984. Flight speed and directional responses to wind by migrating Canada Geese. Auk 101:342—348. Welham, C. V. J. 1994. Flight speeds of migrating birds: a test of maximum range speed predictions from three aerodynamic equations. Behavioral Ecology 5:1-8. Wilson Bulletin 1 17(4):375-38 1, 2005 HOST USE BY SYMPATRIC COWBIRDS IN SOUTHEASTERN ARIZONA JAMESON E CHACEi 2 ABSTRACT. — Sympatric avian brood parasites may compete for the same nests to parasitize. Host-resource partitioning, or “alloxenia,” is exhibited by several Old World cuckoos where they are sympatric in Africa, Japan, and Australia. I examined host use by sympatric Brown-headed Cowbirds {Molothrus ater) and Bronzed Cowbirds (M. aeneus) from 1997 to 1999 in pine-oak and montane riparian forests in southeastern Arizona. Bronzed and Brown-headed cowbirds partitioned hosts by host body size. Brown-headed Cowbirds did not parasitize larger hosts (i.e.. Western Tanager, Piranga ludoviciana; and Hepatic Tanager, P. flava), while Bronzed Cowbirds did not parasitize smaller hosts (i.e.. Painted Redstarts, Myioborus pictus\ and Bell’s Vireos, Vireo bellii). Although there was some host overlap (only 2/7 parasitized host species were parasitized by both cowbird species), only 3/48 nests (all Plumbeous Vireo, V. plumbeus) contained eggs of both parasite species. Parasitism by sympatric cowbirds in southeastern Arizona appears to fit the pattern of alloxenia. Received 16 October 2003, accepted 13 June 2005. Avian obligate brood parasites do not build nests, but lay their eggs in the nests of other species, the “hosts,” which raise young par- asites (Friedmann 1929, Davies 2000). Fitness of obligate brood parasites is directly related to choosing suitable hosts. Such hosts lack ef- fective anti-parasite behaviors (e.g., egg rejec- tion; Rothstein 1990), effectively incubate the parasite’s eggs, and feed the parasite’s young an appropriate diet (Middleton 1991). Inter- ference by other brood parasites at an already parasitized host nest — in the form of egg puncturing, egg removal, or multiple parasit- isms— can reduce parasite fitness (Peer and Sealy 1999, Nakamura and Cruz 2000, Trine 2000). Partitioning of hosts may reduce the poten- tial costs of interference competition between sympatric brood parasites. Sympatric brood parasitic cuckoos {Cue ulus, Chrysococcyx, Clamator, Eudynamys, Oxylophus, Scythrop.s) in Africa, Australia, and Japan partition their primary hosts, possibly reducing competition for nests (Friedmann 1967, Payne and Payne 1967, Brooker and Brooker 1989, 1992; Hi- guchi 1998). FTiedmann (1967) coined the terms “alloxenia” to describe host partition- ing by obligate brood parasites in sympatry and “homoxenia” to describe overlap in host ' Dept, of Ihivironmcntal, Population, and Organis- mic Biology, Univ. of C’olorado, ttouldcr, C'O 80309- 0334, USA. ‘Current address: Dept, ol FJiology and Itiomedical Sciences, Salve Regina Univ., Newport, KI 02840- 4192. USA; e-mail: Jameson. chaceCn'salve.edu use. In contrast to studies of Old World cuck- oos, there is little information on host use by sympatric New World brood parasites (but see Carter 1986, Peer and Sealy 1999, Mermoz and Fernandez 2003). The brood-parasitic Brown-headed {Mol- othrus ater) and Bronzed (M. aeneus) cow- birds are sympatric in the southern United States and northern Mexico (Lowther 1993, 1995). Bronzed and Brown-headed cowbirds are considered host generalists that have been recorded parasitizing 94 and 230 different host species, respectively; they overlap in the parasitism of 37 species (Sealy et al. 1997, Ortega 1998; P. E. Lowther pers. comm.). The reproductive success of female cowbirds is di- rectly related to the number of eggs laid in appropriate host nests during the host’s laying period (Ortega 1998). Body size of the host also may affect the reproductive success of parasites: relatively small hosts may not be able to effectively incubate the larger eggs of parasites (Davies and Brooke 1988, McMaster and wSealy 1997, Peer and Bollinger 1997), whereas large hosts may be able to grasp and eject cowbird eggs (Rothstein 1975, Rohwer and Spaw 1988). Host selection may differ be- tween the two cowbird species because Bronzed Cowbirds are larger (female mass = 56.9 g) than Brown-headed Cowbirds (female mass = 32.0 g; Johnsgard 1997). Similar to sympatric species of brood par- asites elsewhere (e.g., Brooker and Brooker 1992), coexisting cowbirds may reduce poten- tial interspecific competition for nests through 375 376 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 differential host use (i.e., alloxenia). I tested the hypothesis that sympatric Bronzed and Brown-headed cowbirds exhibit host-size al- loxenia in southeastern Arizona. METHODS Study sites. — My study was conducted in the Huachuca Mountains (elevation 1,500- 2,450 m, 31° 26' N, 1 10° 20' W) of southeast- ern Arizona near Sierra Vista. During the breeding seasons (May-July) of 1997-1999, I examined host use by Bronzed and Brown- headed cowbirds at four discrete study sites (—20 ha each) in two distinct habitat types: Reef Townsite and Sawmill Canyon in pine- oak woodlands, and Garden Canyon and Hua- chuca Canyon in montane riparian forests. The two montane riparian forest sites were 7 km apart, and the pine-oak woodland sites were 9 km apart. Of the four sites. Garden Canyon and Sawmill Canyon were closest to one another (1.5 km apart). The overstory in the pine-oak woodland sites was dominated by ponderosa {Pinus pon- derosa), southwestern white (F. strobiformis), Apache (F. latifolia), and Chihuahuan (F. chi- huahuana) pines. Dominant shrubs of the un- derstory included silverleaf (Quercus hypo- leucoides) and netleaf (Q. reticulata) oaks, and, especially at Reef Townsite, manzanita {Arctostaphylos pungens). Montane riparian habitat is narrow, linear (<200 m wide), and extends along an eleva- tional gradient (1,500-1,800 m) surrounded by a matrix of xeric habitats: piny on-juniper, desert scrub, montane chaparral, desert grass- land, and Madrean oak woodlands. Primary canopy species included Fremont cottonwood (Populus fremontii), velvet ash (Fraxinus ve- lutina), Arizona sycamore {Platanus wrightii), bigtooth maple {Acer grandidentatum), and Arizona walnut {Juglans major). Common in the understory were Arizona white {Q. ari- zonica) and netleaf oaks, Arizona madrone {Arbutus arizonica), silk-tassel {Garrya wrightii), poison ivy {Rhus radicans), and canyon grape {Vitis arizonica). Frequency of host parasitism, impact, and cowbird reproductive success. — Searches for potential host nests were conducted daily from 20 May to 15 July at Reef Townsite and Saw- mill Canyon during 1997-1999, and in Hua- chuca Canyon and Garden Canyon during 1998-1999. Potential nests included those of all known host species (Ortega 1998) and con- geners of known hosts. Nests were monitored at least once every 3 days, either directly or with a 6-m telescoping mirror-pole. I defined the frequency of parasitism as the proportion of parasitized nests. Clutch initiation was de- termined by backdating from the hatching date, using published incubation information (Ehrlich et al. 1988). The frequency of cow- bird and host egg laying was standardized into 10-day periods across the total pool of nests. Cowbird egg-laying patterns then were com- pared with host clutch initiation by size clas- ses of hosts (small: <10 g; medium: 10.0- 29.9 g; large: >30 g). Statistical analysis. — To determine whether Bronzed and Brown-headed cowbirds laid their eggs randomly (i.e., the “shotgun” ap- proach; Kattan 1997) among host nests, I compared cowbird laying patterns to both a typical Poisson distribution (Preston 1948, Mayfield 1965, Elliott 1977, Kattan 1997, Trine 2000) and an adjusted Poisson distri- bution (Lowther 1984, Lea and Kattan 1998). Unparasitized nests are a special case because some of them may be found by cowbirds and not selected, or found too late in the egg-lay- ing cycle to parasitize (Lowther 1984, Lea and Kattan 1998). Following Lea and Kattan (1998), I calculated the proportion of nests without cowbird eggs based on the distribu- tion of nests with cowbird eggs. A Poisson distribution adjusted for zero-class parasitism can serve as a more conservative measure of cowbird egg-laying patterns, where a signifi- cant departure of the observed distribution from the Poisson suggests that cowbirds target nests. I used the Kolmogorov-Smirnov test (Zar 1984) to compare the distribution of Bronzed and Brown-headed cowbird egg lay- ing, nonparametric rank sum tests to compare central tendencies when data were not nor- mally distributed, and likelihood tests {G- tests) adjusted with William’s correction (So- kal and Rohlf 1981). Unless otherwise stated, all values are reported as mean ± SD; statis- tical significance was set at F = 0.05. For sta- tistical analysis, I used the software package IMP (SAS Institute, Inc. 1995). RESULTS Parasitism frequency. — I monitored 220 nests of 15 species (Table 1); 8 species were Chace • ALLOXENIA IN COWBIRDS 377 TABLE 1. Frequency of Bronzed and Brown-headed cowbird parasitism, Huachuca Mountains Arizona 1997-1999. Host species Mass (g)^ Total nests Nests parasitized Bronzed Brown-headed Cowbird Cowbird n (%) n {%) n (%) Hosts parasitized by both cowbird species Hutton’s Vireo 11.6 6 (2.7) 3 (50.0) 2 (33.3) Plumbeous Vireo 16.6 68 (30.9) 7 (10.3) 22 (32.3) Subtotal 74 (33.6) 10 (13.5) 24 (32.4) Hosts parasitized by Bronzed Cowbirds only Warbling Vireo 14.8 1 (0.4) 1 (100) Western Tanager 28.1 5 (2.3) 1 (20.0) Hepatic Tanager 38.0 8 (3.6) 6 (75.0) Subtotal 14 (6.4) 8 (57.1) Hosts parasitized by Brown-headed Cowbirds only Painted Redstart 7.9 7 (3.2) 1 (14.3) Bell’s Vireo 8.5 12 (5.4) 8 (75.0) Subtotal 19 (8.6) 9 (47.4) Species not parasitized Buff-breasted Flycatcher 7.9 16 (7.3) Western Wood-Pewee 12.8 37 (16.8) Yellow-eyed Junco 20.4 8 (3.6) Greater Pewee 27.2 28 (12.7) Black-headed Grosbeak 42.2 18 (8.2) Cassin’s Kingbird 45.6 3 (1.4) Mexican Jay 124.0 1 (0.4) Steller’s Jay 128.0 2 (0.9) Subtotal 113 (51.4) TotaP 220 (100) 18 (8.2) 33 (15.0) ^ Bird mass data from Dunning (1993). ‘’Although cowbirds parasitized 48 nests, the overlapping parasitism at three Plumbeous Vireo nests raises the total to 51 instances of nest parasitism among the 48 nests. ^ not parasitized {n = 113 nests) and 7 species were parasitized {n = 107 nests of host spe- cies; /I = 45 at Reef Townsite, 21 at Sawmill Canyon, 22 at Huachuca Canyon, and 19 at Garden Canyon). Forty-five percent (48/107) of all host nests were parasitized; two host species were parasitized by both cowbird spe- cies (Hutton’s Vireo, Vireo huttoni\ and Plum- beous Vireo, Vireo phimheus), and three nests (all Plumbeous Vireo) contained at least one egg of both cowbird species (Table 1). For hosts parasitized by both species. Bronzed Cowbird parasitism (13.5%, 10/74) was less than hall that of Brown-headed Cowbirds (32.4%, 24/74; Table 1). Only Bronzed Cow- birds parasitized Hepatic Tanager {Piranha Jiciva\ large host) and Western Tanager (/^ lu- dovicicuui\ high end of medium-size class), and only Brown-headed Cowbirds parasitized Painted Redstart {Myiohorus pictus) and Bell’s Vireo {Vireo hellii; Table 1). Two of the medium-sized hosts (Hutton’s Vireo, Vireo huttoni, and Plumbeous Vireo) were parasit- ized by both cowbird species, and the War- bling Vireo {Vireo gilvus) was parasitized only by the Bronzed Cowbird (Table 1). Potential host nests monitored, but not par- asitized, included those of Buff-breasted Fly- catcher {Empidonax fiuvifrons). Western Wood-Pewee {Contopiis sordididus). Greater Pewee (C. pertinax), Cassin’s Kingbird {Ty- rcumus vociferous), Mexican Jay {Aphelocoma idtramorina), Steller’s Jay {Cyanocitta stel- leri). Yellow-eyed Junco {Jimco phaeonotus), and Black-headed Grosbeak {Phencticus nie- lonoceplialus: Table 1 ). Other known cowbird hosts (Ortega 1998) commonly observed on at least two ot the study sites, but for which 378 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 FIG. 1. Host clutch initiation (bars) and cowbird egg laying (lines) in southeastern Arizona, 1997-1999. Brown-headed Cowbirds (BHCO; 41 eggs, 29 nests) laid eggs earlier than Bronzed Cowbirds (BROC; 21 eggs, 16 nests) (0.50 ® Mean number of cowbird eggs observed per parasitized nest. ^ goodness-of-fit test for cowbird egg dispersion versus Poisson distribution. Mean number of cowbird eggs per nest, calculated across 107 nests available to cowbirds (following Lea and Kattan 1998). Significance of Kolmogorov-Smirnov D for test of cowbird egg dispersion versus an adjusted, zero-egg class Poisson distribution. small hosts (Bell’s Vireo and Painted Redstart; Fig. 1). Nonrandom egg laying. — Combined para- sitism of both cowbird species was random with respect to the Poisson distribution (Table 2): available host nests were randomly para- sitized by at least one of the two cowbird spe- cies. Evaluated individually, however, both Bronzed and Brown-headed cowbirds at my study sites laid their eggs nonrandomly among host nests (Table 2), as demonstrated by sig- nificant departures from the Poisson. Both the traditional approach (e.g., Elliott 1977) and Lea and Kattan’s (1998) more conservative approach yielded the same result (Table 2). Most parasitized nests contained only one par- asite egg (range 1-3) and there was no sig- nificant difference between the number of Brown-headed and Bronzed cowbird eggs laid per nest (Wilcoxon z = 0.68, P = 0.75). DISCUSSION In southeastern Arizona, Bronzed Cowbirds typically parasitized larger species than those parasitized by Brown-headed Cowbirds. Both cowbird species dispersed their eggs uniform- ly with respect to available host nests and gen- erally avoided multiple parasitisms; congru- ence between the two statistical procedures (typical Poisson and adjusted Poisson distri- butions) strengthens this assertion. Only Bronzed Cowbirds parasitized tanagers (the two largest host species ob.served), while only Brown-headed Cowbirds parasitized the two smallest species (Bell’s Vireo and Painted Redstarts). Two of three intermediate-sized hosts were parasitized by both cowbird spe- cies, but parasitism of the same nest by both cowbird species was rare. My results are con- sistent with Friedmann’s (1967) definition of alloxenia, albeit to a lesser degree than that observed among cuckoos, which, in sympatry, exhibit very low overlap in host use (Brooker and Brooker 1992, Higuchi 1998). An impor- tant caveat from my study is that many nests of potential hosts were not found; however, the majority of the nests of the six focal host species were likely found and monitored. My interpretation may have been different had I been able to monitor nests of other species, including those that nest high in the canopy. Based on the host nests I was able to mon- itor, my results are not consistent with those indicating that homoxenia occurs among sym- patric Bronzed and Brown-headed cowbirds in Texas (Peer and Sealy 1999). Compared with Peer and Sealy’s study site in the mesquite grasslands and chaparral of the Texas coastal plains, southeastern Arizona has a greater di- versity of hosts, especially smaller, insectivo- rous passerines. Although not designed as a community study. Peer and Sealy (1999) did not record Bronzed Cowbird parasitism on the smallest host species (Verdin, Auriparus fia- viceps) in their study area, but they did find extensive overlap in parasitism. Both brood parasites laid eggs in the nests of small- to medium-sized host species (Painted Bunting, Passerina ciris\ and Olive Sparrow, Arremo- nops rufivirgatus). Surprisingly, Bronzed Cowbirds did not parasitize some of the larger host species (Red-winged Blackbird, Agclaius phoeniceu.s: and Bullock's Oriole) that were parasitized by Brown-headed Cowbirds. No species were found to be parasitized only by Bronzed Cowbirds (Peer and Sealy 1999); however, sample sizes for some of these spe- 380 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 cies were very small. Different patterns of host use in southern Texas may have been ob- served had sample sizes for some of these spe- cies been larger (B. D. Peer pers. comm.). Sympatric cuckoos in Asia, Australia, and Africa, as well as Bronzed and Brown-headed cowbirds reported here, overlap in the use of secondary hosts (Friedmann 1967, Payne and Payne 1967, Brooker and Brooker 1990, 1992; Higuchi 1998). Each of nine species of cuckoos {Chrysococcyx spp., Clamator spp., Cuculus spp.) in southern Africa primarily parasitize one or two hosts of 65 known host species, with only occasional host overlap (Payne and Payne 1967). Australian bronze- cuckoos {Chrysococcyx spp.; Brooker and Brooker 1992) and Cuculus spp. cuckoos in Japan (Higuchi 1998) are highly host specific in sympatry, but exhibit host overlap when al- lopatric. Where parasites overlap in host use, subtle aspects of habitat selection may be involved in segregation (Southern 1954). Differential habitat selection by sympatric brood parasites has been observed among cuckoos (Fried- mann 1967, Brooker and Brooker 1992) and cowbirds (Peer and Sealy 1999, Chace 2004). In Africa, three sympatric Cuculus spp. cuck- oos exhibit a high degree of host specificity as well as habitat specificity (Friedmann 1967). Red-chested Cuckoos (C. solitarius) largely parasitize thrushes (Cossypha spp.), African Cuckoos (C. gularis) parasitize shrikes {Corvinella spp.) and drongos {Dicru- rus spp.), and Black Cuckoos (C. clamosus) parasitize boubous (Laniarus spp.; Friedmann 1967). To some degree this host partitioning is due to habitat partitioning; Red-chested Cuckoos use the more wooded sites, whereas the African and, especially. Black Cuckoos use relatively open woodlands (Johnsgard 1997). While Bronzed and Brown-headed cowbirds occupied the same four riparian and pine-oak forests in this study. Brown-headed Cowbirds were found across a wider range of habitats than Bronzed Cowbirds (Chace 2004). At broader spatial scales. Bronzed and Brown-headed cowbirds may reduce or avoid competition for host nests through divergent habitat use. Similar to sympatric cowbirds, sympatric cuckoos overlap extensively in diet, habitat re- quirements, and use of hosts (Payne and Payne 1967, Brooker and Brooker 1992). Un- like host-generalist cowbirds, however, cuck- oos tend to be host specialists (Davies 2000). Alloxenia is clearly a pattern that is most like- ly to occur among host and habitat specialists, and it is therefore rather interesting that we find this pattern among generalist cowbirds in Arizona. ACKNOWLEDGMENTS Financial support for this research came through the U.S. Department of Defense, the Research Ranch Foundation, the American Museum of Natural Histo- ry’s Frank M. Chapman Memorial Fund, the Sigma Xi Grants-in-Aid of Research, and the University of Col- orado. I thank S. T. McKinney, S. E. Severs, D. M. Stahl, A. J. Orahoske, S. D. Factor, and D. Waltz for their assistance in the field. R. Bernstein, C. E. Bock, T Brush, A. Cruz, D. Dearborn, K. Ellison, R E. Lowther, C. P. Ortega, B. D. Peer, and S. G. Sealy provided valuable comments on earlier drafts of this manuscript. I thank Fort Huachuca and Coronado Na- tional Forest for allowing me access to study sites on their property. LITERATURE CITED Brooker, L. C. and M. G. Brooker. 1990. Why are cuckoos host specific? Oikos 57:301-309. Brooker, M. G. and L. C. Brooker. 1989. Cuckoo hosts in Australia. Australian Zoological Review 2:1-67. Brooker, M. G. and L. C. Brooker. 1992. Evidence for individual female host specificity in two Aus- tralian bronze-cuckoos {Chrysococcyx spp.). Aus- tralian Zoological Review 40:485-493. Carter, M. D. 1986. The parasitic behavior of the Bronzed Cowbird in south Texas. Condor 88:11- 25. Chace, J. F. 2004. Habitat selection by sympatric brood parasites in southeastern Arizona: the influ- ence of landscape, vegetation and species rich- ness. Southwestern Naturalist 49:24-32. Davies, N. B. 2000. Cuckoos, cowbirds and other cheats. T. and A. D. Poyser, London, United King- dom. Davies, N. B. and M. de L. Brooke. 1988. Cuckoos versus Reed Warblers: adaptations and counter- adaptations. Animal Behaviour 36:262-284. Dunning, J. B., Jr. 1993. CRC handbook of avian body masses. CRC Press, Boca Raton, Florida. Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder’s handbook: a field guide to the natural history of North American birds. Simon and Schuster, New York. Elliott, P. F. 1977. Adaptive significance of cowbird egg distribution. Auk 94:590-593. Friedmann, H. 1929. The cowbirds: a study in the bi- ology of social parasitism. C. C. Thomas and Co., Springfield, Illinois. Chace • ALLOXENIA IN COWBIRDS 381 Friedmann, H. 1967. Alloxenia in three sympatric Af- rican species of Cuculus. Proceedings of the U.S. National Museum 124:1-14. Higuchi, H. 1998. Host use and egg color of Japanese cuckoos. Pages 80-112 in Parasitic birds and their hosts (S. I. Rothstein and S. K. Robinson, Eds.). Oxford University Press, New York. JoHNSGARD, P. A. 1997. The avian brood parasites: de- ception at the nest. Oxford University Press, New York. Kattan, G. H. 1997. Shiny Cowbirds follow the ‘shot- gun’ strategy of brood parasitism. Animal Behav- iour 53:647-654. Lea, S. E. G. and G. H. Kattan. 1998. Reanalysis gives further support to the ‘shotgun’ model of Shiny Cowbird parasitism of House Wren nests. Animal Behaviour 56:1571-1573. Lowther, P. E. 1984. Cowbird nest selection. Wilson Bulletin 96:103-107. Lowther, P. E. 1993. Brown-headed Cowbird {Mol- othrus ater). The Birds of North America, no. 47. Lowther, P. E. 1995. Bronzed Cowbird {Molothrus aeneus). The Birds of North America, no. 144. Mayheld, H. E 1965. Chance distribution of cowbird eggs. Condor 67:257-263. McMaster, D. G. and S. G. Sealy. 1997. Host-egg removal by Brown-headed Cowbirds: a test of the host incubation limit hypothesis. Auk 114:212- 220. Mermoz, M. E. and G. J. Fernandez. 2003. Breeding success of a specialist brood parasite, the Scream- ing Cowbird, parasitizing an alternative host. Con- dor 105:63-72. Middleton, A. L. 1991. Failure of Brown-headed Cowbird parasitism in nests of the American Goldfinch. Journal of Field Ornithology 62:200- 203. Nakamura, T. K. and A. Cruz. 2000. The ecology of egg-puncture behavior by the Shiny Cowbird in southwestern Puerto Rico. Pages 178-186 in Ecol- ogy and management of cowbirds and their hosts (J. N. M. Smith, T. L. Cook, S. 1. Rothstein, S. K. Robinson, and S. G. Sealy, Eds.). University of Texas Press, Austin. Ortega, C. P. 1998. Cowbirds and other brood para- sites. University of Arizona Press, Tucson. Payne, R. B. and L. L. Payne. 1967. Cuckoo hosts in southern Africa. Ostrich 38:135-143. Peer, B. D. and E. K. Bollinger. 1997. Explanations for the infrequent cowbird parasitism on Common Crackles. Condor 99:151-161. Peer, B. D. and S. G. Sealy. 1999. Parasitism and egg puncture behavior by Bronzed and Brown- headed cowbirds in sympatry. Studies in Avian Biology 18:235-240. Preston, F. W. 1948. The cowbird (M. ater) and the cuckoo (C. canorus). Ecology 29:115-116. Rohwer, S. and C. D. Spaw. 1988. Evolutionary lag versus bill-size constraints: a comparative study of the acceptance of cowbird eggs by old hosts. Evo- lutionary Ecology 2:27-36. Rothstein, S. I. 1975. An experimental and teleonom- ic investigation of avian brood parasitism. Condor 77:717-728. Rothstein, S. I. 1990. A model system for coevolu- tion: avian brood parasitism. Annual Review of Ecology and Systematics 21:481-508. SAS Institute, Inc. 1995. JMP statistics and graphics guide. SAS Institute, Inc., Cary, North Carolina. Sealy, S. G., J. E. Sanchez, R. G. Campos, and M. Marin. 1997. Bronzed Cowbird hosts: new re- cords, trends in host use, and cost of parasitism. Omitologia Neotropical 8:175-184. SoKAL, R. R. AND E J. Rohlf. 1981. Biometry: the principles and practice of statistics in biological research, 2nd ed. W. H. Freeman and Co., San Francisco, California. Southern, H. N. 1954. Mimicry in cuckoos’ eggs. Pages 219-232 in Evolution as a process (J. Hux- ley, A. C. Hardy, and E. B. Ford, Eds.). George Allen and Unwin, London, United Kingdom. Trine, C. L. 2000. Effects of multiple parasitism on cowbird and Wood Thrush nesting success. Pages 135-144 in Ecology and management of cowbirds and their hosts (J. N. M. Smith, T. L. Cook, S. 1. Rothstein, S. K. Robinson, and S. G. Sealy, Eds.). University of Texas Press, Austin. Zar, j. H. 1984. Biostatistical analysis, 2nd ed. Pren- tice Hall, Engelwood Cliffs, New Jersey. Wilson Bulletin 1 17(4):382-385, 2005 RESIGHTINGS OF MARKED AMERICAN OYSTERCATCHERS BANDED AS CHICKS CONOR R McGOWAN,! 23 SHILOH A. SCHULTE, i AND THEODORE R. SIMONS^ ABSTRACT. — Since 2000, we have been banding American Oystercatcher (Haematopus palliatus) chicks at Cape Lookout and Cape Hatteras national seashores as part of a long-term demographic study. Between 2000 and 2002, we banded 23 chicks. We report on resightings of eight chicks that returned to the Outer Banks of North Carolina in the summers of 2003 and 2004. These are the first records of American Oystercatcher chicks resighted near their natal areas in their 2nd and 3rd years. The 3-year-old birds appeared to be paired and acted territorial, whereas the 2nd-year birds were observed alone or in groups and did not exhibit territorial behavior. Our observations suggest that the American Oystercatcher’s life history is similar to that of the Eurasian Oys- tercatcher {Haematopus ostralegus). Received 17 November 2004, accepted 1 July 2005. The American Oystercatcher {Haematopus palliatus) is a species of concern (Brown et al. 2001, Davis et al. 2001) that breeds along the eastern coast of the United States (Nol and Humphrey 1994). It is listed in the U.S. Shorebird Conservation Plan as highly imper- iled due to habitat loss and because popula- tions are apparently declining in the south- eastern U.S. (Brown et al. 2001, Davis et al. 2001). By 1900, the species had been elimi- nated from regions north of Virginia, primar- ily due to hunting (Nol and Humphrey 1994). American Oystercatchers have been steadily expanding northward since the 1950s, and the first successful breeding record of oystercatch- ers in Nova Scotia was in 1997 (Nol and Humphrey 1994, Mawhinney and Benedict 1999, Davis et al. 2001). They are now be- ginning to occupy new habitats for breeding, such as salt marshes and dredge spoil islands (Frohling 1965, McNair 1988, Humphrey 1990, Toland 1992, Nol and Humphrey 1994, Davis et al. 2001, McGowan et al. 2005). Lit- tle is known about dispersal after fledging or about survival in the first 2 years, and these demographic parameters could be important for population viability (Davis 1999). Chicks banded during previous studies in Massachu- setts and Virginia (Nol and Humphrey 1994) were never seen after fledging. * uses. North Carolina Coop. Fish and Wildlife Research Unit, Dept, of Zoology, North Carolina State Univ., Campus Box 7617, Raleigh, NC 27695, USA. 2 Current address; Dept, of Fisheries and Wildlife, Univ. of Missouri-Columbia, 302 Anheuser Busch Natural Resources Bldg., Columbia, MO 65211, USA. ^ Corresponding author; e-mail: cpm4h9@mizzou.edu As part of a long-term study of oystercatch- er demography, we have been banding Amer- ican Oystercatcher adults and chicks since 2000 at Cape Hatteras and Cape Lookout na- tional seashores in North Carolina (Godfrey and Godfrey 1973). The national seashores are composed of six barrier islands along the North Carolina coast (36° 2' N, 75° 32' W to 34° 35' N, 76° 32' W), including Bodie Island (at the northern end), Hatteras Island, Ocra- coke Island, North Core Banks, South Core Banks, and Shackleford Banks (at the south- ern end). At Cape Lookout National Seashore, a mile-marker system denotes locations within the park; mile 0.0 is located at the northern end of North Core Banks at Ocracoke Inlet. From 2000 to 2002, we banded 23 chicks between 10 and 25 days after hatching. In 2000, we used federal stainless steel bands and engraved colored aluminum bands to in- dividually mark birds, but the colors faded quickly and we could not identify individual birds without recapturing them. In 2001 and 2002, we marked birds with a federal stainless steel band and a unique combination of col- ored wrap-around plastic bands. Here, we re- port on birds banded as chicks that we recap- tured or observed in their natal area as 2- and 3-year-olds. These observations were inciden- tal to a separate, long-term study of American Oystercatcher nesting success, and sightings of these birds were recorded opportunistically as we searched for, and checked, nests from AT Vs and trucks. On 4 April 2003, we trapped a territorial adult oystercatcher at mile marker 8.5 on North Core Banks using a noose carpet trap and a decoy (McGowan and Simons 2005). 382 McGowan et al. • RESIGHTINGS OF BANDED AMERICAN OYSTERCATCHERS 383 This bird was originally banded as a chick on 8 June 2000 on South Core Banks (—25 km to the south). The bird and its presumed mate vigorously defended a territory from a neigh- boring pair of oystercatchers. The recaptured bird was not seen again during the breeding season and we suspect that it abandoned its territory due to disturbance associated with trapping it. On 3 June 2003, we observed a 2nd-year bird with three unbanded birds at mile 3.5 on North Core Banks; this bird was originally banded as a chick on 1 July 2001 at Ocracoke Inlet (—5 km away). We observed the same individual again, also with three unbanded birds, on 15 June 2003 at mile 2.4 on North Core Banks. During late May and early June of 2004, this same bird was observed on nu- merous occasions defending a territory with an unbanded mate near mile marker 4.5 on North Core Banks. On 22 June, it was seen in the same location with a different, banded bird. On 24 June, we observed this bird with three other unbanded birds, and it was no lon- ger exhibiting territorial behavior. We found no evidence of breeding, but its earlier terri- torial behavior indicated that it might breed on North Core Banks within 1-2 years (Nol and Humphrey 1994, Ens et al. 1996). During the summer of 2004, we observed six additional 2nd-year birds that were banded as chicks during the summer of 2002 at Cape Lookout and Cape Hatteras national seashores (Table 1 ). Four of the six birds were seen within 10 km of their hatching site (Table 1). One of those six birds — banded on 1 1 June 2002 as a chick just north of Buxton Village at Cape Hatteras National Seashore — was ob- served many times during the winters and I summers of 2003 and 2004 at Little Estero Lagoon, near Ft. Myers Beach on the gulf coast of Florida (26° 26' N, 81° 57' W); it was last seen at Little Estero Lagoon on 26 May 2004. On 28 June 2004, that same individual was resighted at Pea Island National Wildlife I Refuge, at the northern end of Hatteras Island, ! and was seen throughout July of 2004 at many I locations in the northern part of Hatteras Is- I land. j The 2- and 3-year-oId birds that we ob- I served were not breeding. These observations I support the notion that American Oystercatch- I ers are long-lived birds with delayed matura- tion (Nol and Humphrey 1994), with a life history similar to that of the closely related and extensively studied Eurasian Oystercatch- er (Haematopus ostralegus\ Ens et al. 1996, Bruinzeel 2004). The birds observed as 3- year-olds were apparently attempting to ac- quire territories and establish pair bonds with a mate. We observed both 3-year-olds exhib- iting territorial interactions with other birds, and both were observed with a single other individual (Table 1). None of the 2nd-year birds exhibited territorial behavior or appeared to be paired; rather, they often were seen in groups of three or more birds (Table 1). These 2nd-year birds exhibited behaviors similar to those of subadult Eurasian Oystercatchers that Bruinzeel (2004) called “intruders” or “ag- gressive club-birds,” which move about the breeding grounds alone or in small groups of young birds, gathering information on terri- tory availability and quality. At this point, we cannot report on dispersal distances because we are uncertain whether birds that we ob- served will return to breed at the locations where we resighted them; however, our ob- servations suggest that American Oystercatch- ers exhibit strong natal philopatry. Dispersal during the pre-breeding stage probably ex- plains the northward expansion of the Amer- ican Oystercatcher’s breeding range over the last 50 years (Frohling 1965, McNair 1988, Humphrey 1990, Toland 1992, Nol and Hum- phrey 1994, Mawhinney and Benedict 1999, McGowan et al. 2005). We observed birds moving up to 57 km, and to different islands, from their hatching sites. Our observations represent the first records of American Oystercatcher chicks to be re- sighted near their natal territories within 2—3 years of hatching; 34% of the chicks we band- ed between 2000 and 2002 have been resight- ed as 2- or 3-year-olds. Although we cannot calculate survival rates on the basis of our op- portunistic observations, these relatively high rates of resight ings and recaptures bode well for the species and for future analyses of an- nual survival and dispersal. A better under- standing ol oystercatcher demography and dispersal is important for safeguarding the fu- ture of this species along the eastern coast of the United States (Davis 1999, Davis et al. 2001 ). 384 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 TABLE 1. Original capture dates and locations of eight American Oystercatchers and subsequent capture or resighting dates and locations in North Carolina, 2000-2004. We report national seashore mile markers as reference locations (GPS data were not collected). Individual Capture date Capture location^ Recapture date(s) Recapture location^* Distance from initial capture^ No. in group‘d 805-60047 6 Aug 2000 South Core Banks 4 Apr 2003 Mile 8.2, North >25 km 2 Core Banks 805-60059 1 Jul 2001 Mile 0.0, North 3 Jun 2003 Mile 3.5, North 5.6 km 4 Core Banks Core Banks 15 Jun 2003 Mile 2.4, North 3.9 km 4 Core Banks May-Jun 2004 Mile 4.5, North 7.2 km 2 Core Banks 805-60085 1 Jun 2002 Mile 5.9, North 28 Sep 2004 Shackleford Banks 57 km 1 Core Banks 805-60088 1 1 Jun 2002 Buxton, Hatteras 28 Jun 2004 Pea Island NWR 42 km 1 Island 805-60091 14 Jun 2002 Ocracoke Island 1 Jul 2004 Mile 6.0, North >11.2 km 2 Core Banks 15 Jul 2004 Mile 4.5, North >8.9 km 2 Core Banks 805-60093 16 Jun 2002 Mile 9.6, North 24 Jun 2004 Mile 11.1, North 2.4 km — Core Banks Core Banks 30 Jun 2004 Mile 8.0, North 2.6 km 5 Core Banks 805-60100 29 Jun 2002 Mile 9.6, North 30 Jun 2004 Mile 8.0, North 2.6 km 2 Core Banks Core Banks 975-85202 1 Jul 2002 Mile 2.3, North 10 Jun 2004 Mile 7.0, North 7.6 km 3 Core Banks Core Banks 1 1 Jun 2004 Mile 5.0, North 4.3 km — Core Banks 22 Jun 2004 Mile 4.5, North 3.5 km 4 Core Banks 24 Jun 2004 Mile 5.5, North 5.1 km — Core Banks 1 Jul 2004 Mile 8.0, North 9.2 km 3 Core Banks ^ For some birds, exact locations and mile markers were not recorded; instead, we report the island or general location where captured or resighted. Approximate distances were calculated using the difference in mile markers and converting to kilometers. Where mile markers were not recorded for captures or recaptures, we report the minimum distance between islands. These distances do not represent dispersal distances, because the breeding or settlement status of these birds is uncertain. Group size in which each individual was observed. Dashes indicate that no information was recorded. ACKNOWLEDGMENTS We thank the National Park Service, U.S. Geologi- cal Survey, and U.S. Fish and Wildlife Service for sup- port of this research. We are grateful to S. Harrison, M. Lyons, M. Rikard, J. R. Cordes, J. M. Altman, K. M. Sayles, and S. McKeon for their assistance in the field and for logistical support. We are grateful to L. W. Bruinzeel, B. Lauro, and one anonymous reviewer for helpful comments on an earlier version of this pa- per. LITERATURE CITED Brown, S., C. Hickey, B. Harrington, and R. Gill (Eds.). 2001. The U.S. shorebird conservation plan, 2nd ed. Manomet Center for Conservation Sciences, Manomet, Massachusetts. Bruinzeel, L. W. 2004. Search, settle, reside and re- sign: territory acquisition in the oystercatcher. Ph.D. dissertation. University of Groningen, Har- en. The Netherlands. Davis, M. B. 1999. Reproductive success, status and viability of American Oystercatcher (Haematopus palliatus). M.Sc. thesis. North Carolina State Uni- versity, Raleigh. Davis, M. B., T. R. Simons, M. J. Groom, J. L. Weav- er, AND J. R. Cordes. 2001. The breeding status of the American Oystercatcher on the East Coast of North America and breeding success in North Carolina. Waterbirds 24:195-202. McGowan et al. • RESIGHTINGS OF BANDED AMERICAN OYSTERCATCHERS 385 Ens, B. J., K. B. Briggs, U. N. Safriel, and C. J. Smit. 1996. Life history decisions during the breeding season. Pages 186-218 in The oyster- catcher: from individuals to populations (J. D. Goss-Custard, Ed.). Oxford University Press, Ox- ford, United Kingdom. Frohling, R. C. 1965. American Oystercatcher and Black Skimmer nesting on salt marsh. Wilson Bulletin 77:193-194. Godfrey, P. G. and M. M. Goderey. 1976. Barrier island ecology of Cape Lookout National Sea- shore and vicinity. North Carolina. U.S. Govern- ment Printing Office, Washington, D.C. Humphrey, R. C. 1990. Status and range expansion of the American Oystercatcher on the Atlantic Coast. Transactions of the Northeast Section of The Wildlife Society 47:54-61. Mawhinney, K., B. Allen, and B. Benedict. 1999. Status of the American Oystercatcher (//. pallia- tus), on the Atlantic Coast. Northeastern Naturalist 6:177-182. McGowan, C. P. and T. R. Simons. 2005. Method for trapping breeding adult American Oystercatchers. Journal of Field Ornithology 76:46-49. McGowan, C. P, T. R. Simons, W. Golder, and J. CoRDES. 2005. A comparison of American Oys- tercatcher reproductive success on barrier beach and river island habitats in coastal North Carolina. Waterbirds 28:149-154. McNair, D. B. 1988. Atypical nest site of the Amer- ican Oystercatcher in South Carolina. Chat 52:1 1- 12. Nol, E. and R. C. Humphrey. 1994. American Oys- tercatcher (Haematopus palliatus). The Birds of North America, no. 82. Toland, B. 1992. Use of forested spoil islands by nest- ing American Oystercatchers in Southeast Florida. Journal of Field Ornithology 63:155-158. Wilson Bulletin 1 17(4):386— 389, 2005 COMPARISON OF WOOD STORK FORAGING SUCCESS AND BEHAVIOR IN SELECTED TIDAL AND NON-TIDAL HABITATS F. CHRIS DEPKIN,‘ LAURA K. ESTEP, ‘ ^ A. LAWRENCE BRYAN, JR.,'-^ CAROL S. ELDRIDGE,' AND I. LEHR BRISBIN, JR.' ABSTRACT. — In 1999, we compared foraging success rates (captures/min) and foraging behaviors of Wood Storks {Mycteria americana) at tidal (Georgia) and non-tidal freshwater (South Carolina) foraging sites. Foraging success rates were 30 times greater at the tidal site, but storks foraging in tidal areas only fed at low tide, which limited their foraging time at that site. On-site behaviors indicated the window of prey availability. Storks at the tidal site engaged almost exclusively in foraging behaviors, whereas storks at the non-tidal site devoted more time to other, non-foraging behaviors (e.g., preening, resting). The greater foraging success rate associated with the tidal site suggests that salt marsh/tidal creek habitats are high-quality foraging areas. Received 21 December 2004, accepted 6 September 2005. Wading birds use a diversity of behaviors to acquire prey. Wood Storks {Mycteria amer- icana) feed mostly by tactilocation, literally bumping into their prey with partially open bills and capturing prey with a rapid reflex action (Kahl and Peacock 1963). They also employ a repertoire of associated behaviors (e.g., foot stirring, wing flashing) for startling prey or otherwise making them more active and possibly more catchable (Kushlan 1978). To forage effectively. Wood Storks require shallow wetlands with concentrations of prey (Kahl 1964). Non-tidal freshwater foraging habitats in Georgia are typically shallow, rel- atively free of vegetation, non-flowing, and support prey densities ranging from 0.1 to 50.0 prey items/m^ (mean = 7.8 prey/m^; Coulter and Bryan 1993). The use of tidal salt marshes by foraging storks has also been doc- umented during both breeding and nonbreed- ing seasons, and it is presumed that tidal creeks draining as the tide recedes (2.5 m tidal amplitude in Georgia) provide excellent con- ditions for foraging storks (Gaines et al. 1998, Bryan et al. 2002). To test this presumption, we observed storks within tidal and freshwater non-tidal foraging habitats in 1999 to compare foraging success rates and behaviors. The Wood Stork was federally listed as an endan- gered species in 1984 due to population de- ' Savannah River Ecology Lab., RO. Drawer E, Aik- en, SC 29802, USA. 2 Current address: Dept, of Epidemiology and Public Health, Yale School of Medicine, New Haven, CT 05620, USA. ^ Corresponding author; e-mail: bryan@srel.edu dines resulting from loss of their shallow wet- land foraging habitats (U.S. Fish and Wildlife Service 1986, 1996). Determining the type and quality of foraging habitat is an important step toward the recovery of this species. METHODS Study areas and behavioral observations. — We studied Wood Stork foraging behavior in salt marsh (tidal site) and freshwater (non-tid- al site) systems. The 180-ha Purvis Creek salt marsh (tidal site) is located on the western edge of the Brunswick peninsula in Camden County, Georgia (31°11'N, 81°31' W). We conducted observations during daylight hours between 6 July and 24 September 1999. The storks included in our observations were non- breeding (postbreeding season) birds. Wood Storks typically forage in the tidal creeks of salt marshes at low tide (Gaines et al. 1998); therefore, we limited our observations to 2 hr before and after dead low tide in tidal creek habitat. We conducted behavioral observa- tions from a camouflaged boat temporarily an- chored in an area used by storks. The boat was positioned during high tide and became stranded on the mudflats during our low tide observations. We recorded behaviors of focal storks with a Panasonic VHP video camera. One person (CSE) reviewed all VHP tapes and documented stork behaviors. We observed foraging storks at a non-tidal freshwater site at the Kathwood ponds in south-central (Aiken County) South Carolina (33° 20' N, 81° 50' W). These 16 ha of fresh- water impoundments were established in 1986 and stocked with fish to provide foraging hab- 386 Depkin et al. • WOOD STORK FORAGING SUCCESS RATES 387 itat for storks during the postbreeding season. Coulter et al. (1987) and Bryan et al. (2000) provide detailed descriptions of impoundment management activities. We conducted our ob- servations of storks during crepuscular and daylight hours of July and August 1999, when the impoundments were partially drained to mimic the natural drawdown of freshwater systems. Prey densities in the partially drained impoundments were high relative to natural foraging sites (densities ranged from 10 to 30/ m^; Bryan et al. 2001). At Kathwood, we used binoculars and spotting scopes to observe storks from a 2-m-tall blind placed at the edge of the impoundments. We conducted continuous sampling of focal storks (Altmann 1974), which allowed us to calculate time budgets of both foraging and non-foraging behaviors for individual birds. Birds were observed for a minimum of 5 min (Walsh 1990), although longer observations were attempted. Focal storks were observed until they disappeared from view (departed from the site, moved behind an obstruction, or could no longer be distinguished from other storks), at which point we switched to a dif- ferent focal stork. We recorded the following behaviors while the focal bird was actively foraging: foraging success (captures/min), lo- comotion patterns (walking with bill out of water, flushing/flying, or standing still), limb movements (foot stirring and wing flashing to enhance foraging), interactions with other birds on the foraging site (aggression), and other general behaviors. We categorized for- aging as successful when the focal bird snapped its bill in the water, then raised its bill out of the water (prey were often ob- served) and tilted its head back as if swallow- ing. Possible unsuccessful foraging attempts (e.g., bill snapping in the water without sub- sequently raising the bill) could not be deter- mined with certainty given field conditions (distance and lighting). Stork age (adult, sub- adult, hatch-year) was determined by plumage characteristics (Coulter et al. 1999). Data analysis.— ^pcc'xWc behaviors during each observation were calculated both on a per-minute basis and as percentages of the to- tal observation period for that bird. We used Wilcoxon rank-sum tests to compare foraging success rates and observation duration of focal storks. Activity patterns and foraging behav- iors of storks feeding in the tidal site are dis- cussed relative to those of storks in non-tidal sites. Results are presented as means ± SD. RESULTS We observed the foraging behaviors of 37 Wood Storks (n = 33 adult, 3 subadult, 1 hatch-year) at the tidal site (n = 523 min total observation time) and 34 Wood Storks (n = 14 adult, 8 subadult, 12 hatch-year) at the non-tidal site (n = 2,987 min total observation time). There were no significant differences in foraging success rates between adult and im- mature storks at either the tidal (Z = 1.05, P = 0.29) or the non-tidal (Z = 0.84, P = 0.40) site; therefore, we pooled the data for adult and immature birds by site. The mean time that focal birds remained and were observable at the tidal site was only 14.1 ± 8.6 min, but was 87.9 ± 73.6 min at the non-tidal site (Z = 6.39, P < 0.001). The foraging success rate at the tidal creek site was nearly three prey items captured per min (Table 1). Foraging was by far the most frequent behavior of Wood Storks at the tidal site (Table 1), followed by walking and stand- ing; preening, flying, and aggression com- bined occupied <5% of the birds’ time. Be- haviors that potentially enhanced foraging ef- ficiency (i.e., foot stirring and wing flashing) were employed at the tidal site. The foraging success rate at the non-tidal site (0.10 ± 0.09 prey items/min) was signif- icantly lower than it was at the tidal site (Table 1; Z = -6.75, P < 0.001). Foraging was also the most frequent activity at the non-tidal site (38% of observation time), with standing and preening being next in importance, together constituting more than half of the birds’ activ- ities (Table 1 ). We did not record observations of foot stirring and wing flashing because doc- umenting these behaviors was not part of the methods used at this site. DISCUSSION The tidal creek system appeared to be a temporally prey-rich foraging habitat for coastal Wood Storks, although there are tide- related time constraints on site use, and prey sizes may be smaller than at non-tidal sites. Storks tended to forage in the tidal creek hab- itat for shorter periods, but their foraging suc- cess rate (2.95 prey itcm.s/min) was very high 388 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 TABLE I. Comparison of foraging behaviors (mean per min) and activity patterns (mean percent time) of Wood Storks using tidal (Purvis Creek, Georgia; n = 37 birds) and non-tidal (Kathwood foraging ponds, inland South Carolina; « = 34 birds) habitats in 1999. Tidal Non-tidal Foraging behavior^ Success rate (captures/min) 2.95 ± 2.42 (0. 1-9.6) 0.10 ± 0.09 (0.0-0.46) Foot stirs/min 8.1 (0.1-17.0) Not recorded'’ Wing flashes/min 0.2 (0.0-1. 5) Not recorded'’ Activity‘S Foraging 78.6% (13.7-99.7%) 38.1% (0.1-99.3%) Standing 10.8% (0.0-31.5%) 32.4% (0.0-81.4%) Walking 7.6% (0.0-27.1%) 7.3% (0.0-75.0%) Preening 3.1% (0.0-49.7%) 20.9% (0.0-62.9%) Flying‘* 0.2% (0.0-0.9%) 1.1% (0.0-12.1%) Aggression 0.1% (0.0- 1.6%) <1% ^ Mean ± SD (range). Documenting these behaviors was not part of the methods used at the non-tidal site. Mean (range). Flying indicates movement within the observation area (bird visible throughout movement). relative to that at the non-tidal site (~30X greater), supporting suggestions that tidal creeks near low tide provide excellent forag- ing habitat for storks (Gaines et al. 1998, Bry- an et al. 2002). Similarly, Grey Herons (Ardea cinerea) feeding in Asian tidal sites also had a greater prey-catching rate than those feeding in non-tidal sites (Sawara et al. 1990). Salt- water prey, however, are generally smaller than freshwater prey (Bryan and Gariboldi 1998), and storks likely require more of the smaller prey to meet their energetic needs. Foot stirring was very prevalent (8.1/min) at our tidal site compared with foot stirring in freshwater impoundments in a similar study (0.1/min; Walsh 1990), and may be a more effective strategy within turbid, flowing tidal environments (Kahl 1964). Wood Storks in tidal habitat spent twice the percentage of time foraging as storks in the non-tidal habitat, possibly due to constraints on prey availability due to tidal cycles. There simply may not have been enough time for storks to spend on non-foraging behaviors during the short period of low tide and prey availability at this tidal site. Storks at the non- tidal site apparently were able to forage at a slower pace, given the longer period of prey availability; thus, they were able to spend more time resting and preening. Environmental variables at the tidal site also may have affected stork presence. Micro- habitat differences (e.g., creek-bed contour. depth) among tidal creeks result in suitable depths at different times and for varying du- rations when the tide is ebbing. Variations in fish abundance and diversity occur daily and seasonally within individual tidal creeks (Cain and Dean 1976, Shenker and Dean 1979, Var- nell et al. 1995), which likely affect prey availability in the creek. In addition, the tidal creek site had a narrower field of view than the non-tidal site, and the linearity of the hab- itat may have limited the length of time focal birds could be kept in view. Finally, distur- bances caused some storks to abandon the tid- al site. The birds were cognizant of the ob- server during many of our observations at the tidal site (FCD pers. obs.); on rare occasions, sounds made by the observer within the boat and other boat traffic (from local fishermen) may have resulted in site abandonment by storks. In conclusion, tidal creeks are important, prey-rich foraging habitats for Wood Storks. Tidal systems are more dynamic than non-tid- al systems, with storks having higher foraging efficiencies but shorter periods of prey avail- ability. Storks can move to different tidal creeks within the marsh system, but with as- sociated costs (e.g., travel). In the non-tidal system, capture rates of prey are far lower, but prey items are available for longer periods and are likely larger. It is not known whether the overall mass of prey consumed by individual storks differs between tidal and non-tidal for- Depkin et al. • WOOD STORK FORAGING SUCCESS RATES 389 aging habitats. Additional studies of foraging strategies employed by birds using salt marsh- es (e.g., number of creeks used, total daily for- aging time and associated travel time) are needed to determine whether overall con- sumption rates are similar for the tidal and non-tidal habitats. Regardless, salt marshes are important coastal foraging habitats for postbreeding Wood Storks and should be pro- tected to aid stork recovery. ACKNOWLEDGMENTS We thank G. M. Masson, R. K. Hastie, and K. Sol- omon for their assistance and support throughout the project. The U.S. Fish and Wildlife Service (USFWS)- Savannah Coastal Refuges provided housing for coast- al field personnel. L. B. Hopkins assisted with obser- vations at both sites. The Kathwood ponds are located on the National Audubon Society’s Silverbluff Sanc- tuary and are ably managed by D. M. Connelly and R Koehler. Earlier drafts of this manuscript were im- proved by three anonymous reviewers. LKE was fund- ed by a National Science Foundation Grant (DBI- 0139572) to the Savannah River Ecology Laboratory. Other aspects of this study were funded by grants from the USFWS-Brunswick Field Office; and the Environ- mental Remediation Sciences Division of the Office of Biological and Environmental Research, U.S. Depart- ment of Energy through a Financial Assistance Award (DE-FC09-96SR 18546) to the University of Georgia Research Foundation. LITERATURE CITED Altmann, J. 1974. Observational study of behavior: sampling methods. Behaviour 49:227-267. Bryan, A. L., Jr., M. C. Coulter, and I. L. Brisbin, Jr. 2000. Mitigation for the endangered Wood Stork on Savannah River Site. Studies in Avian Biology 21:50-56. Bryan, A. L., Jr., K. F. Gaines, and C. S. Eldridge. 2002. Coastal habitat use by Wood Storks during the non-breeding sea.son. Waterbirds 25:429-435. Bryan, A. L., Jr. and J. C. Gariboldi. 1998. Food of nestling Wood Storks in coastal Georgia. Colonial Waterbirds 21:152-158. Bryan, A. L., Jr., J. W. Snodgrass, J. R. Robinette, J. L. Daly, and I. L. Brisbin, Jr. 2001. Nocturnal activities of post-breeding Wood Storks. Auk 1 18: 508-513. Cain, R. L. and J. M. Dean. 1976. Annual occurrence, abundance, and diversity of fish in a South Car- olina intertidal creek. Marine Biology 36:369- 379. Coulter, M. C. and A. L. Bryan, Jr. 1993. Foraging ecology of Wood Storks (Mycteria americana) in east-central Georgia. I. Characteristics of foraging sites. Colonial Waterbirds 16:59-70. Coulter, M. C., W. D. McCort, and A. L. Bryan, Jr. 1987. Creation of artificial foraging habitat for Wood Storks. Colonial Waterbirds 10:203-210. Coulter, M. C., J. A. Rodgers, J. C. Ogden, and F. C. Depkin. 1999. Wood Stork {Mycteria ameri- cana). The Birds of North America, no. 409. Gaines, K. E, A. L. Bryan, Jr., R M. Dixon, and M. J. Harris. 1998. Foraging habitat use by Wood Storks nesting in the coastal zone of Georgia, USA. Colonial Waterbirds 21:43-52. Kahl, M. P. 1964. Food ecology of the Wood Stork {Mycteria americana) in Florida. Ecological Monographs 34:97-117. Kahl, M. P. and L. J. Peacock. 1963. The bill-snap reflex: a feeding mechanism in the American Wood Stork. Nature 199:505-506. Kushlan, j. a. 1978. Feeding ecology of wading birds. Pages 249-298 in Wading birds (A. Sprunt, J. C. Ogden, and S. Winckler, Eds.). Research Re- port, no. 7, National Audubon Society, New York. Sawara, Y., N. Azuma, K. Hino, K. Fukui, G. De- MACHi, AND M. Sakuyama. 1990. Feeding activity of the Grey Heron {Ardea cinerea) in tidal and non-tidal environments. Japanese Journal of Or- nithology 39:45-52. Shenker, j. M. and j. M. Dean. 1979. The utilization of an intertidal salt marsh creek by larval and ju- venile fishes: abundance, diversity and temporal variation. Estuaries 2:154-163. U.S. Fish and Wildlife Service. 1986. Recovery plan for the U.S. breeding population of the Wood Stork. U.S. Fish and Wildlife Service, Atlanta, Georgia. U.S. Fish and Wildlife Service. 1996. Revised re- covery plan for the U.S. breeding population of the Wood Stork. U.S. Fish and Wildlife Service, Atlanta, Georgia. Varnell, L. M., K. j. Havens, and C. Hershner. 1995. Daily variability in abundance and popula- tion characteristics of tidal salt-marsh fauna. Es- tuaries 18:326-334. Walsh, J. M. 1990. Estuarine habitat use and age-spe- cific foraging behavior of Wood Storks {Mycteria americana). M.Sc. thesis. University of Georgia. Athens. Wilson Bulletin 1 17(4):390-393, 2005 SEXUALLY DIMORPHIC BODY PLUMAGE IN JUVENILE CROSSBILLS PIM EDELAAR,^ 23,6,7 g PHILLIPS, ^ AND PETER KNOPS^ ABSTRACT. — Sexual dimorphism in color and pattern of contour feathers is rare in juvenile songbirds. We describe how captive-bred Juvenile males of Scottish Crossbill {Loxia scotica) and nominate Red Crossbill (L. curvirostra curvirostra) can be differentiated from females prior to prebasic molt by an unstreaked patch on the males’ upper breast. There may be a functional relationship between sexual dimorphism and the formation of pair bonds or breeding while the birds are still in juvenile plumage. Sexually dimorphic Red Crossbills and Bearded Tits (Panurus biarmicus) are known to form pair bonds, and even breed successfully, while still in juvenile plumage. Received 6 August 2004, accepted 10 July 2005. Among songbirds, sexual dimorphism in ju- venile flight feathers (which are often retained until after the first breeding season) is not un- usual, but sexual dimorphism in juvenile con- tour feathers is rare (Pyle et al. 1987, Svens- son 1992). Sexual dimorphism in juvenile crossbills {Loxia spp.) has not been reported in the scientific literature (e.g., Svensson 1992, Cramp and Perrins 1994, Adkisson 1996), but, in an unreviewed bulletin for breeders of captive birds (United Kingdom), Castell (1983) reports that juvenile crossbills are sexually dimorphic. Females are described as completely streaked on the underparts, from the base of the lower mandible to the belly. Males differ in that they have a yellow- ish, unstreaked band or patch at the upper breast, just below the throat (Fig. 1) and an unstreaked chin (but see Fig. 1). In addition, the streaks on the breasts of males are less bold, narrower, and rounder-edged (not square-edged), and the ground color of the breast is a richer color (more yellowish, not whitish). Here, we address the reliability of using the unstreaked breast patch to sex ju- ' Dept, of Biology, New Mexico State Univ., Las Cruces, NM 88003, USA. ^ Dept, of Zoology, Univ. of British Columbia, Van- couver, BC V6T 1Z4, Canada. 3 Dept, of Theoretical Biology, Univ. of Groningen, 9750 AA, Haren, The Netherlands. Yetholm, St. Catherine’s Place, Elgin, Moray, Scot- land, United Kingdom. ^ Molsteeg 37, 6369 GL Simpelveld, The Nether- lands. ^ Current address: Dept, of Ecology and Evolution- ary Biology, Univ. of Arizona, Tucson, AZ 85721, USA. ^ Corresponding author; e-mail: w.m.c.edelaar@umail.leidenuniv.nl venile crossbills. We only assessed and report on results pertaining to the breast patch; no quantitative information was available to us for evaluating the reliability of other reported sexually dimorphic traits, although we concur that juvenile males are generally more yellow- ish in color than juvenile females. From 1993 to 2003, we tested the validity of using the unstreaked patch to sex 228 ju- venile crossbills bred in captivity. All birds were kept in chicken wire and metal-frame aviaries. Adults and chicks were fed with commercial birdseed, supplemented with grit, eggshell or fish bone, and high protein egg feed, and were provisioned regularly with co- nifer cones. Birds were banded as nestlings with uniquely numbered bands. Pedigrees were known, and most birds were related due to regular inbreeding. The putative and actual sex of each bird was determined by each of three breeders. Our study entailed sexing juveniles from two different crossbill taxa. The identification of some crossbill taxa can be challenging, and birds in the wild should be identified primarily on the basis of vocalizations, measurements, and geographic location (Groth 1993, Sum- mers et al. 2002, Edelaar et al. 2003). Despite the fact that calls of captive birds are unlike those of wild birds, the (nominate) Red Cross- bill {Loxia curvirostra curvirostra) is readily distinguished in captivity from other crossbill taxa by bill and body size, as long as the part- ly overlapping — but typically larger — Scottish Crossbill (L. scotica) can be excluded. Our Red Crossbill stock originated from continen- tal Europe (Germany, Austria, and Russia) and had not been crossed with other crossbill 390 Edelaar et al. • DIMORPHIC PLUMAGE IN JUVENILE CROSSBILLS 391 FIG 1. A juvenile female (left) and male (right) Scottish Crossbill {Loxia scotica). Note the continuous streaking across the underparts of the female and the unstreaked patch on the upper breast of the male (upper ! arrows), and the denser streaking on the underparts (lower arrows) of the female (dark stripes wider than pale ' stripes) compared with those of the male (pale stripes wider than dark stripes). Contrary to initial reports, ' however, both sexes seem to have a streaked chin. taxa. The Scottish Crossbills used in this study were all progeny of wild birds caught in the Scottish Highlands and subsequently isolated from other crossbill taxa during breeding. Our Scottish Crossbill stock has an average bill size thought to correspond clo.sely with that of wild Scottish Crossbills (REP and R. W. Sum- mers unpubl. data), confirming that it did not derive from sympatrically breeding smaller- billed Red and larger-billed Parrot crossbills ! (L. pytyopsittacLis). The putative sex of individuals in Juvenile plumage was determined only by the pre.scnce (males) or absence (females) of an unslreaked patch on the upper breast, before any Juvenile contour feathers had been molted. Actual sex was determined by plumage after prebasic molt. It is known that adult coloration of cap- tive crossbills is dependent on whether many carotenoids are provided during molt (Hill and Benkman 1995). If carotenoids are not pro- vided, the normally red males develop a yel- lowish, female-like plumage. On the other hand, unlike many other species, female crossbills in captivity may develop a red plumage when provided with food that is ar- tificially enriched with carotenoids (e.g.. Hill and Benkman 1995). Hence, overall color (yellowish or reddish) is of little use when at- tempting to .sex adult birds in captivity. Ca- rotenoid-enriched food was given only to .some juveniles (putative males) during the study, but this did not preclude us from cor- rectly .sexing all of them after they had un- dergone prebasic moll. Whether in yellow or red plumage, males have brighter, unmarked feathers on the crown and have a colored (yel- low' or reddish) chin; females (at least in the taxa we investigated here) have small dark spots on the crown and have a grayish chin 392 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 TABLE 1 . Reliability of body plumage for sexing captive-bred juvenile crossbills. Putative sex of juveniles was based on the presence (males) or absence (females) of an unstreaked patch on the upper breast and compared to actual sex following prebasic molt. P is from a Fisher exact test. Males Females Taxon n Putative Actual Putative Actual p Scottish Crossbill 205 101 99 104 104 <0.001 Red Crossbill 23 8 8 15 15 <0.001 (Phillips 1977, Castell 1983; REP pers. obs.). In offspring kept for subsequent breeding, sex determined on the basis of these adult plum- age characteristics was always confirmed by reproductive behavior. We used Fisher exact tests to determine the correspondence between the putative sex de- termined by juvenile plumage and the actual sex determined after prebasic molt. A signif- icant P-value (P < 0.05) indicates that the pu- tative and actual sex correspond better than predicted by chance. We assumed that there were no effects of relatedness, parental care, or rearing environment; we also assumed no differences between observers. Scottish and Red crossbills were sexed in juvenile plumage with a high degree of reli- ability (Table 1). Only 2/205 juvenile female Scottish Crossbills were sexed incorrectly (P < 0.001), and all 23 Red Crossbills were sexed correctly (P < 0.001) in juvenile plum- age. We also obtained small sample sizes for Parrot, Himalayan (L. c. himalayensis), and Two-barred crossbills (L. leucoptera bifascia- ta). Preliminary information suggests that sex- ual dimorphism in juvenile plumage of these taxa is not as evident as in Scottish and Red crossbills, as several individuals of both sexes were identified incorrectly as males or fe- males: 6/20 (30%), 2/6 (33%), and 3/7 (43%), respectively. In order to determine the useful- ness of plumage dimorphism to sex juvenile crossbills of different taxa, more data on sex- ual dimorphism in juvenile body plumage should be collected, especially in wild cross- bills and for the many Eurasian and North American subspecies of Red Crossbill. There appears to be a correlation between life history and the occurrence of sexual di- morphism in juvenile body plumage. Juvenile Bearded Tits {Panurus biarmicus), which have sexually dimorphic contour feathers, normally form pair bonds, and, like juvenile Red Crossbills, may even reproduce success- fully while still in juvenile plumage (Glutz von Blotzheim and Bauer 1993, Adkisson 1996; K. van Eerde pers. comm., PE pers. obs.). Because reproductive behavior is at least as rare as sexual dimorphism among birds in juvenile plumage, the coincidence of these two traits suggests a possible functional relationship. However, a few other passerine species that exhibit sexual dimorphism in ju- venile body plumage (e.g., Serinus citrinella [Borras et al. 1993], S. serinus [Senar et al. 1998], Parus major [Domenech et al. 2000], P. caeruleus [Johnsen et al. 2003]) are not known to form pair bonds or breed while in juvenile plumage. Thus, we hypothesize that species that form pair bonds or reproduce while still in juvenile plumage will show sex- ual dimorphism in juvenile body plumage; the reverse is not necessarily true. For instance, the Red Crossbill subspecies L. c. tianschan- ica is often reported to breed in juvenile plum- age (Edelaar et al. 2003); therefore, we predict that juvenile males of this taxon can be dis- tinguished easily from juvenile females on the basis of traits we describe in this paper. ACKNOWLEDGMENTS We thank M. Kleijnen for kindly providing data on his Parrot Crossbills. We thank K. Roselaar for corre- sponding with us about sexual dimorphism in the plumage of Western Palearctic birds and life history of Bearded Tits, and C. W. Benkman for discussing sex- ual dimorphism in White-winged Crossbills and for hosting PE. We thank M. Marquiss, R. Rae, J. C. Sen- ar, and an anonymous reviewer for comments on a previous version of the manuscript. Our study was sup- ported by a TALENT stipend from the Netherlands Organization for Scientific Research and an Honorary Scholarship from the University of Groningen to PE. LITERATURE CITED Adkisson, C. S. 1996. Red Crossbill {Loxia curviros- tra). The Birds of North America, no. 256. Edelaar et al. • DIMORPHIC PLUMAGE IN JUVENILE CROSSBILLS 393 Borras, a., J. Cabrera, X. Colome, and J. C. Senar. 1993. Sexing fledglings of cardueline finches by plumage color and morphometric variables. Jour- nal of Field Ornithology 64:199-204. Casteel, P. 1983. Sexing young crossbills. Cage & Aviary Birds, May 28 issue, p. 9, 20. Cramp, S. and C. M. Perrins. 1994. The birds of the Western Palearctic. Oxford University Press, Ox- ford, United Kingdom. Domenech, j., j. C. Senar, and E. Vilamajo. 2000. Sexing juvenile Great Tits Parus major on plum- age colour. Bulletin GCA 17:17-23. Edelaar, P, R. Summers, and N. Iovchenko. 2003. The ecology and evolution of crossbills Loxia spp.: the need for a fresh look and an international research programme. Avian Science 3:85-93. Glutz von Blotzheim, N. and K. M. Bauer. 1993. Handbuch der Vogel Mitteleuropas. Band 13-1. Muscicapidae-Paridae. Aula-Verlag, Wiesbaden, Germany, [in German] Groth, j. G. 1993. Evolutionary differentiation in morphology, vocalizations, and allozymes among nomadic sibling species in the North American Red Crossbill (Loxia curvirostra) complex. Uni- versity of California, Berkeley and Los Angeles. Hill, G. E. and C. W. Benkman. 1995. Exceptional response by female Red Crossbills to dietary ca- rotenoid supplementation. Wilson Bulletin 107: 555-557. JOHNSEN, A., K. Delhey, S. Andersson, and B. Kem- PENAERS. 2003. Plumage colour in nestling Blue Tits: sexual dichromatism, condition dependence and genetic effects. Proceedings of the Royal So- ciety of London, Series B 270:1263-1270. Phillips, A. R. 1977. Sex and age determination of Red Crossbills (Loxia curvirostra). Bird-Banding 48:110-117. Pyle, R, S. N. G. Howell, R. P. Yunick, and D. E DeSante. 1987. Identification guide to North American passerines. Slate Creek Press, Bolinas, California. Senar, J., J. Domenech, and M. J. Conroy. 1998. Sex- ing Serin Serinus serinus fledglings by plumage colour and morphometric variables. Ornis Svecica 8:17-22. Summers, R. W, D. C. Jardine, M. Marquiss, and R. Rae. 2002. The distribution and habitats of cross- bills Loxia spp. in Britain, with special reference to the Scottish Crossbill Loxia scotica. Ibis 144: 393-410. SvENSSON, L. 1992. Identification guide to European passerines. Svensson, Stockholm, Sweden. Wilson Bulletin 1 1 7(4):394-399, 2005 A DESCRIPTION OF THE NEST AND EGGS OF THE PALE-EYED THRUSH {PLATYCICHLA LEUCOPS) WITH NOTES ON INCUBATION BEHAVIOR GUSTAVO ADOLFO LONDONO^ feed the nest, Thrushes (Turdinae) belong to one of the most widely distributed avian families and oc- cupy a variety of habitats throughout the world (Clement 2000). Although many of the temperate-zone thrush species have been well studied, little is known about thrushes occur- ring in the New World tropics. There are only two species of Platycichla, both of which are restricted to South America, including the is- land of Trinidad (Ridgley and Tudor 1989, Fjeldsa and Krabbe 1990). In contrast, the closely related Turdus genus is widespread and species rich (Clement 2000). The two genera are weakly differentiated, leading some authors to suggest that Platycichla should be merged with Turdus (e.g., Ridgley and Tudor 1989). Mitochondrial DNA sequence data seem to support this suggestion (Klicka et al 2005). The Pale-eyed Thrush {Platycichla leucops) inhabits montane evergreen forest at eleva- tions of 1,300—2,100 m in the northern and Central Andes and in the tepui region of southern Venezuela and adjacent Guyana and Brazil (Hilty and Brown 1986, Ridgley and Tudor 1989). This species is uncommon and seemingly local in humid montane forest. Fundacion EcoAndinaAVildlife Conservation So- ciety, Colombia Program, Apartado Aereo 25527, Cali, Colombia. 2 Florida Museum of Natural History, Dickinson Hall, Univ. of Florida, Gainesville, FL 32611-8525, where it occurs singly, in pairs, or in group that congregate at fruiting trees in the fores canopy (Hilty and Brown 1986, Ridgley an. Tudor 1989, Fjeldsa and Krabbe 1990). Fo the Turdus genus, there is abundant informa tion on incubation and nestling periods, par ticularly for those species inhabiting the tern perate zone. However, this information i; lacking for most of the Neotropical species and little is known about the Platycichla ge nus (Hilty and Brown 1986, Ricklefs 1997 Clement 2000). Here, I describe the nest, eggs, and nest- lings of the Pale-eyed Thrush and make rele- vant comparisons to the well-studied thrushes of the Turdus genus. In addition, I describe the nest microclimate and incubation patterns of the Pale-eyed Thrush. METHODS Study site. — The study was conducted in the 489-ha Santuario de Fauna y Flora Otun- Quimbaya (4°43'11"N, 75° 28' 70" W), on the western slope of the Central Range of the Andes, east of Pereira, Department of Risar- alda, Colombia. The area is a mosaic of forest patches (e.g., Cecropia telealba, Siparuna echinata, Saurauia brachybotrys. Ficus andi- cola, Prestoea acuminata, Palicourea angus- tifolia, Miconia acuminifera) that differ in — most trees are 40 years or older — and patches are mixed with plantations of Chinese ash {Fraxinus chinensis). Small patches of mature, native forest (e.g.. Magnolia hernan- dezii. Ficus killipii, Prumnopytis harmsiana. ^ Current address: Univ. of Florida, Dept, of Zool- ogy, 223 Bartram Hall, P.O. Box 118525, Gainesville, FL 32611-8525, USA; e-mail: galondo@ufl.edu 394 Londono • NEST DESCRIPTION OE THE PALE-EYED THRUSH 395 Juglans neotropica, Aniba perutilis) occur on the ridges (Londono 1994). Elevations of the study site range from 1,900 to 2,100 m. Mean maximum and min- imum annual temperatures are 20.2° and 11.3° C, respectively. Mean annual rainfall is 2,700 mm and is distributed bimodally; dry seasons ^(<100 mm rainfall per month) occur Decem- ^iber-January and June-August (Rios et al. 12005). I' Nest monitoring. — I monitored nests by vis- iting them at different times in the morning and afternoon. To record patterns of incuba- tion and nest microclimate, I placed a Hobo data logger (Onset Computer Corporation, Bourne, Massachusetts) in each nest. The units had two temperature sensors: one was i placed inside the nest cup (at the bottom) and t|the other was placed outside the nest at the • same level as — and 20 cm from — the first sen- sor. These devices measure temperature with an accuracy of ±0.36° C with a resolution of !±0.2° C at +20° C. The units were set to re- cord simultaneously the inner and outer nest temperatures every 2 min. During the day, I assumed that females had left their nest to for- age if the nest temperature dropped below the range of incubation values known from noc- turnal records (when females typically spent all of their time on the nest). RESULTS Nest description and incubation patterns. — } I report on two nests of the Pale-eyed Thrush. I On 15 April 2003, I found the first nest next \ to a tree-fall gap within a Chinese ash plan- ^tation, 35 m from a creek. The nest was 1 m It above ground in a 10-cm depression where the J three main branches of a live ash (dbh 35 cm) t formed a crotch. The nest, built in a clump of if epiphytic Anthurium sp. (Araceae), was 40 rmm deep, had a moss exterior, and an interior r lining of black rhizomorph fibers. Because the nest was placed in a tree crotch, the cup was not perfectly round. The nest’s inner dimen- sions were 96.3 X 70.0 mm, the outer dimen- sions were 104.6 X 132.4 mm, the height was 61.6 mm, and the nest wall averaged 24.7 mm thick. It contained two greenish-colored eggs with brown blotches (concentrated at one end) that varied in shape and density. The eggs dif- fered slightly in size (26.1 X 20.0 mm and 27.4 X 19.4 mm), but weighed the same (5.25 g)- During the incubation period, 35 observa- tions at different times of day revealed that only the female incubated. Internal tempera- tures indicated that the female consistently left the nest at dawn (05:30 EST) and returned at dusk (18:00; Fig. lA). (External nest temper- atures were not recorded because the sensor failed.) Nocturnal nest temperatures (when the adult was sitting in the nest) varied between 24° and 27° C. On 18 April, the adult left the nest at approximately 01:00, after which the nest temperature dropped to the lowest re- corded (—11° C) during the incubation period. For the next 2 days, the female did not incu- bate during daylight hours (Fig. lA). As a re- sult, the general incubation pattern at this nest was highly irregular (Fig. 2A, B). On 22 April, the eggs were depredated. I collected the nest and deposited it in the ornithological collection of the Institute de Ciencias Natur- ales, Universidad Nacional de Colombia (ICN nest collection catalog # ICN-N193). On 14 May 2003, M. M. Rios found a sec- ond nest 25 m from a creek in mature, native forest. The nest was located in a Dendropanax macrophyllum (Araliaceae) tree 1.3 m above ground and inside a 17-cm diameter hole of a broken limb. The nest cup was 64.4 mm deep, and, like the first nest, was not perfectly round because it was constrained by the shape of the hole. The nest’s inner dimensions were 71.1 X 82.1 mm, the outer dimensions were 1 10.2 X 130.0 mm, the height was 81.6 mm, and the nest wall averaged 37.6 mm thick. The nest contained two greenish-colored eggs with brown blotches, resembling those of the first nest. These eggs, however, were slightly larger (28.7 X 20.0 mm and 30.6 X 20.0 mm), and each weighed 5.5 g. The nest was also con- structed of mosses and had a lining of black rhizomorphs. After activating the temperature data logger on 15 May, I left the field site on 20 May and did not return until 2 June, at which time I observed two nestlings in the nest. A substantial temperature increase inside the nest suggested that the eggs hatched late in the afternoon of 27 May (Fig. 1C). On 2 June (day 6 after hatching), the nestlings had yellow down on their heads and backs, their skin was orange, and feather sheaths were emerging on their wings and middle backs. 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 29 28 27 26 25 24 23 22 21 20 29 28 27 26 25 24 23 22 21 :an 2 n THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 A D^wn B I I I I I I • 16 April o 17 April ▼ 18 April V 19 April ■- — 20 April □ 21 April • 16 May o 17 May ▼ 18 May V 19 May — 20 May □ 21 May Time (hr) urly internal nest temperatures at two Pale-eyed Thrush nests in the Central Andes of Nest 1: 16-21 April; (B) nest 2; 16-21 May; and (C) nest 2: 22-27 May. Temperatures during the incubation period with a Hobo Data Logger. On-bouts (min) Londono • NEST DESCRIPTION OF THE PALE-EYED THRUSH 397 700 150^ 100 50 H 0 -50 •U*i{ 700 600 500 400 / / 150^ 100 50 ^ 0 £ 1 23456789 1011 12131415 -50 W 3 E 100 goo 80 70 60 50 40 30 20 10 0 B !/ L . / V / « • X 1 « ■Jj. - - CO - CM 5 6 7 8 9 1011 12 13 1415 16 17 18 19 D ■ i n i H i 1 " i.ii 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hr) FIG. 2. Female attentiveness at two Pale-eyed Thrush nests in the Central Andes of Colombia, 2003. (A) Nest 1: mean incubation time, 16-21 April; (B) nest 1: mean time spent off the nest, 16-21 Apnl; (C) nest 2: mean incubation time, 16-27 May; (D) nest 2: mean time spent off the nest, 16-27 May. Error bars are _ S . The nestlings weighed 24.3 and 23.3 g, and their eyes were slightly open. One day later the nestlings weighed 24.5 and 23.8 g, their feather sheaths were longer, and feather sheaths had begun to emerge on their heads. During the nestling stage, both the male and female responded to my presence with noisy alarm calls. I saw both parents feed the nest- lings fruits of Dendropanax macrophyllum\ I later found seeds of this fruit and insect parts in the nestlings’ feces. By the morning of 4 June, the nestlings had been depredated. 1 col- lected the nest and deposited it in the ICN ornithological collection (catalog # ICN- N194). Photos of the nest, nestlings, and eggs are available at http://www.zoo.un.edu/gustavo/ gallery.html. Temperature data recorded in the .second nest also indicated that the adult left the nest at dawn (05:30) and returned at dusk (18:00; Fig. IB, C) and that the incubation pattern varied during the day. However, frequent off- bouts resulted in shorter incubation periods during the early morning and late afternoon compared with those of the first nest (Fig. 2C, D). The longest on-bouts occurred at midday, whereas the longest off-bouts occurred during the next hour (13:00). DISCUSSION The nest of P. leucops has been described previously only by Marin and Carrion (1991) and possibly by Goodfellow (1901). Nest shape and egg coloration of the Pale-eyed Thrush were similar to those described by Ma- rin and Carrion (1991 ) and similar to descrip- tions for many other species in the thrush fam- ily (Hilty and Brown 1986, Ridgely and Tudor 1989, Stiles and Skutch 1989, Clement 2000). However, the nest-site locations of the previ- ously described nests were different from those I describe here; the ones found in Ec- uador were located in embankments (Marin and Carrion 1991). The nest of the congeneric 398 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Yellow-legged Thrush {P. flavipes) is a shal- low cup constructed of roots and mud, lined with moss and hne roots, and typically placed on a bank (ffrench 1976). Clutch size is two, and eggs are pale blue or greenish-blue marked with reddish-brown (ffrench 1976). The primary difference in the nests of the two Platycichla species is that Pale-eyed Thrushes apparently do not use mud in nest construc- tion. Nest shape, nest materials, and egg col- oration of the Pale-eyed Thrush are very sim- ilar to those of several species in the Turdus genus (Hilty and Brown 1986, Stiles and Skutch 1989, Clement 2000). Nest materials (e.g., moss exterior, black rhizomorphs in the lining), and the nest’s low height are similar to those of Catharus spp. {Turdus nests are usually placed higher than Catharus nests; F. G. Stiles pers. comm.). Typical of thrushes, only the female incu- bated, but both adults attended nestlings (Clement 2000). Based on the hatching date of the second nest, the Pale-eyed Thrush in- cubates for at least 13 days. Incubation peri- ods reported for 21 species in the Turdus ge- nus average 13 days (range = 11-18 days; Clement 2000); thus, the estimated incubation period of the Pale-eyed Thrush is within the range of Turdus spp. There also are no ap- parent differences in duration of incubation and nestling periods between tropical and temperate species of Turdus, although com- plete information is lacking for all but 2 of the 29 tropical species. As in many species, the clutches of temperate thrushes are larger than those of tropical thrushes (Ricklefs 1997). Because the Pale-eyed Thrush nest- lings were depredated, I could not determine the length of their nestling period. It averages 14 days for the Turdus genus (range = 9-19 days; Clement 2000). Nocturnal nest temperatures varied little, due to nearly 100% adult attentiveness. An exception occurred on the night of 18 April, when the female left the nest — possibly to avoid predation — and the nest temperature dropped to 11°C for at least 4 hr. Such be- havior can have a strong influence on embry- onic development (Turner 2002). Nest microclimate, and therefore adult be- havior at the nest, is determined by a variety of factors, including wind, rain, ambient tem- perature, nest orientation and shape, clutch size, and predation risk (Facemire et al. 1990, Sidis et al. 1994, Ghalambor and Martin 2002). Nest microclimate and temperature are probably affected by nest location and mate- rials, especially for open-cup nests (Ar and Sidis 2002, Hansell and Deeming 2002, Hil- ton et al. 2004). Although I did not measure variables that may have influenced nest mi- croclimate, potential microclimatic differences between nest locations were reflected in the rates of heat loss. These differences were clear when the adult left the nest at dawn: in the first nest the temperature dropped 10-12° C (Fig. lA), but in the second nest the temper- ature dropped only 1-2.5° C (Fig. IB, C). Maintaining nest temperatures during the day can affect the time adults need to spend in bouts of nest attentiveness (Ar and Sidis 2002); in turn, this can affect adult foraging time. Although descriptions of nests are an im- portant aspect of basic natural history infor- mation, they are lacking for many Neotropical bird species. Nest descriptions are crucial for understanding the mechanisms that may drive the high diversity of nest forms and locations, the causes of high predation rates among Neo- tropical bird species, and the factors that in- fluence nest attendance behavior. ACKNOWLEDGMENTS I thank M. M. Rios for providing me with the lo- cation of the second nest. C. D. Cadena, G. Kattan, J. Foster, F. G. Stile, and two anonymous reviewers made valuable suggestions to improve earlier versions of this manuscript. Idea Wild provided field equipment that was essential for data collection. Finally, I thank the staff of the Santuario de Fauna y Flora Otun-Quimbaya and the National Parks Unit for logistic support and permission to work at the park. Financial support was provided by the John D. and Catherine T. MacArthur Foundation and the Nando Peretti Foundation. LITERATURE CITED Ar, a. and Y. Sidis. 2002. Nest microclimate during incubation. Pages 143-160 in Avian incubation behaviour, environment, and evolution (D. C. Deeming, Ed.). Oxford University Press, New York. Clement, P. 2000. Thrushes. Princeton University Press, Princeton, New Jersey. Facemire, C. F, M. E. Facemire, and M. C. Facemire. 1990. Wind as a factor in the orientation of en- trance of Cactus Wren nests. Condor 92:1073- 1075. FFRENCH, R. 1976. A guide to the birds of Trinidad and Londono • NEST DESCRIPTION OF THE PALE-EYED THRUSH 399 Tobago. Harrowood Books, Valley Forge, Penn- sylvania. Fjeldsa, J. and N. Krabbe. 1990. Birds of the high Andes. Zoological Museum, University of Copen- hagen, Denmark. Ghalambor, C. K. and T. E. Martin. 2002. Compar- ative manipulation of predation risk in incubating birds reveals variability in the plasticity of re- sponses. Behavioral Ecology 13:101-108. Goodeellow, W. 1901. Results of an ornithological journey through Colombia and Ecuador. Ibis 1 ; 300-319. Hansell, M. H. and D. C. Deeming. 2002. Location, structure and function of incubation sites. Pages 8-25 in Avian incubation behaviour, environment, and evolution (D. C. Deeming, Ed.). Oxford Uni- versity Press, New York. Hilton, G. M., M. H. Hansell, G. D. Ruxton, J. M. Reid, and P. Monaghan. 2004. Using artificial nests to test importance of nesting materials and nest shelter for incubation energetics. Auk 121: 777-787. Hilty, S. L. and W. L. Brown. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey. Klicka, j., G. Voelker, and G. M. Spellman. 2005. A molecular phylogenetic analysis of the “true thrushes” (Aves: Turdinae). Molecular Phyloge- netics and Evolution 34:486-500. Londono, E. 1994. Parque Regional Natural Ucumari: un vistazo historico. Pages 13—21 in Ucumari: un caso tipico de la diversidad biotica andina (J. O. Rangel, Ed.). Corporacion Autonoma Regional de Risaralda, Pereira, Colombia. Marin A., M. and J. M. Carrion B. 1991. Nests and eggs of some Ecuadorian birds. Ornitologia Neo- tropical 2:44-46. Ricklefs, R. E. 1997. Comparative demography of New World populations of thrushes {Turdus spp.). Ecological Monographs 67:23-43. Ridgley, R. S. and G. Tudor. 1989. The birds of South America, vol. 1: the oscine passerines. Uni- versity of Texas Press, Austin. Rios, M. M., G. A. Londono, and M. C. Munoz. 2005. Densidad poblacional e historia natural de la Pava Negra {Aburria aburri) en los Andes Cen- trales de Colombia. Ornitologia Neotropical 16: 205-217. SIDIS, Y, R. ZiLBERMAN, AND A. Ar. 1994. Thermal aspects of the nest placement in the Orange-tufted Sunbird (Nectarinia osea). Auk 111:1001-1005. Stiles, E G. and A. E Skutch. 1989. A guide to the birds of Costa Rica. Cornell University Press, Ith- aca, New York. Turner, J. S. 2002. Maintenance of egg temperature. Pages 119-141 in Avian incubation behaviour, en- vironment, and evolution (D. C. Deeming, Ed.). Oxford University Press, New York. Short Communications Wilson Bulletin 1 17(4):400-^02, 2005 Interspecific Nest Sharing by Red-breasted Nuthatch and Mountain Chickadee Patrick A. Robinson,^ Andrea R. Norris,^ and Kathy Martin^*^’^ ABSTRACT. — We report an observation of inter- specific nest sharing between Red-breasted Nuthatches {Sitta canadensis) and Mountain Chickadees (Poecile gambeli) near Williams Lake, British Columbia, Can- ada. The nest contained two Red-breasted Nuthatch and three Mountain Chickadee nestlings. The nest was attended by a pair of Mountain Chickadees earlier in the observation period and later by an adult female Red-breasted Nuthatch; all five nestlings fledged. Competition for nest sites due to a decrease in cavity availability may have contributed to this occurrence. Received 5 November 2004, accepted 18 July 2005. The advantage of nesting in cavities is often high success, but cavity nesters must compete with other individuals and species to secure this resource. Competition for cavities can limit population densities where cavity avail- ability is low (Brush 1983, Peterson and Gau- thier 1985, Holt and Martin 1997). Red- breasted Nuthatches {Sitta canadensis) regu- larly excavate new cavities; however, they also may reuse or renovate existing cavities. Mountain Chickadees {Poecile gambeli) pri- marily reuse existing cavities, but very infre- quently renovate or excavate cavities (KM un- publ. data). Both species are common at our study sites in the Williams Lake area of Brit- ish Columbia, Canada. The area consists of interior Douglas-fir {Pseudotsuga menziesii) and lodgepole pine {Pinus contorta) inter- spersed with patches of grassland and stands of quaking aspen {Populus tremuloides; Mar- tin and Eadie 1999). Red-breasted Nuthatches and Mountain Chickadees are resident species that compete for similar nest sites, as both pre- fer mixed forest with a strong conifer com- * Centre for Applied Conservation Research, Faculty of Forestry, Univ. of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada. 2 Canadian Wildlife Service, 5421 Robertson Rd., RRl, Delta, BC V4K 3N2, Canada. ^ Corresponding author; e-mail: kmartin @ interchange. ubc.ca ponent and have similar cavity preferences (Ghalambor and Martin 1999, McCallum et al. 1999, Martin et al. 2004). Chickadees and nuthatches, along with Downy Woodpeckers {Picoides pubescens), comprise a sub-group of small-bodied cavity nesters competing for cavity resources in the nest web (Martin et al. 2004). The rate of ex- tra-group cavity reuse among nuthatches and chickadees is low (17%) relative to the rate of reuse (70%) for primary cavity nesters (Ait- ken et al. 2002). Thus, high intra-group cavity reuse is the primary source of competition for nest sites among chickadees and nuthatches. If absolute or relative availability of suitable cavities decreased, competition in this group would increase, promoting cavity acquisition strategies, such as usurpation or nest sharing. Steeger and Dulisse (2002) reported increased competition and aggression among cavity nesters in response to changes in the relative abundance of nest sites. Usurpation also oc- curs in response to decreased nest-site abun- dance (McCallum et al. 1999). Although not previously reported among Red-breasted Nut- hatches and Mountain Chickadees, nest shar- ing could result from cavity competition if nest initiation by a subordinate pair occurs pri- or to occupation by a dominant pair, and if the new occupants do not destroy the progeny of the initial pair. In this note, we report a case of interspecific nest sharing, where adults of both species attended the nest, and young of both species were reared to fledging. OBSERVATION In May and June 2004, during the course of our 10-year held investigation of cavity nesters in an area approximately 40 km west of Williams Lake, British Columbia, Canada, we monitored a case of nest sharing involving Mountain Chickadees and Red-breasted Nut- hatches (Martin et al. 2004) in a quaking as- pen. On 3 1 May, we observed two adult 400 SHORT COMMUNICATIONS 401 Mountain Chickadees attending the nest and taking insects into the cavity. On I June, PAR flushed an adult Mountain Chickadee from the cavity. This was the last detection of adult chickadees at or near the nest. At this time, the cavity was presumed to contain Mountain Chickadee chicks of unknown age. On the next visit (7 June) a female Red-breasted Nut- hatch was tending the nest; she entered the cavity with food twice within 5 min. PAR vi- sually inspected the cavity and found five chicks (two nuthatch and three chickadee). On 10 June, the female nuthatch made frequent (approximately once per min) foraging trips from a nearby Douglas-fir tree to the nest. At least two fecal sacs were removed during 6 min of observation. On 1 1 June, ARN ob- served all five chicks still in the cavity, and two nuthatch chicks (estimated at 16 days of age) fledged during the observation period. The fledgling nuthatches were seen the next day foraging with the adult nuthatch on and near the nest tree while the cavity still con- tained three healthy chickadee nestlings. With fewer chicks in the cavity, ARN could see that the nest was lined with fur, typical of chick- adee nests, but fresh pitch had been applied to the cavity entrance, which is typical of Red- breasted Nuthatch nests. During this obser- vation, the adult female nuthatch arrived at the cavity without food and vocalized toward the cavity from a nearby branch, apparently en- couraging the remaining Mountain Chickadee nestlings to fledge. The female nuthatch then provisioned the chickadee nestlings twice, re- moving fecal sacs following both visits. On 16 June, the cavity was empty, and with no evidence of predation, we presumed that the chickadees had fledged successfully. Because no birds were banded, subsequent sightings of Red-breasted Nuthatches or Mountain Chick- adees in the area could not be associated with this nest. The study plot where the observation oc- curred was in a 26-ha stand of mixed decid- uous and coniferous forest consisting of 85% Douglas-fir, 4% lodgepole pine, 8% spruce {Picea spp.), and 3% quaking aspen. In 2002, we found four Red-breasted Nuthatch nests, and in 2003, we found one nuthatch and five Mountain Chickadee nests. The study plot was selectively harvested in the fall of 2003. The nest tree (recently dead aspen, 30.2 cm dbh) was situated at the edge of the cutblock. In 2004, the first post-cut year, we monitored two Red-breasted Nuthatch and two Mountain Chickadee nests in addition to the shared nest cavity. This was our only observation of in- terspecific nest sharing and brood rearing in our 10-year study of cavity nesters, during which we monitored 69 1 nests of small cavity nesters (52 Black-capped Chickadee, Poecile atricapillus; 42 Downy Woodpecker; 340 Mountain Chickadee; and 257 Red-breasted Nuthatch). DISCUSSION Although active competition — in the form of aggression before clutch initiation and nest usurpation before and during incubation — is frequently reported (Ghalambor and Martin 1999, McCallum et al. 1999), this is the first record of Mountain Chickadees and Red- breasted Nuthatches successfully rearing their young in a nest attended by both parental spe- cies. In our study area, nuthatch nest density more than tripled from 0.03 nests/ha during 1996-2000 to 0.10 nest/ha during 2001-2004; during the same period, chickadee nest density increased from 0.05 to 0.14 nests/ha (KM un- publ. data). This may be a result of regional changes in tree condition and an increased abundance of forest insects (KM unpubl. data). Nuthatches and chickadees prefer dead and decaying aspen trees, which composed <7% of trees on our stands (Martin et al. 2004). Furthermore, nest-site availability de- creased at a local scale, due to cutting on the site. Thus, both the absolute and relative avail- ability of nest sites decreased in our study area. These factors, combined with the recent tripling of nuthatch and chickadee popula- tions, may have increased encounter rates and interspecific competition, facilitating the nest- sharing occurrence. We were able to confirm nest sharing be- cause we visited the nest tree and inspected the cavity visually on multiple occasions. Un- fortunately, we did not locate this nest until after the eggs had hatched; thus, we could not determine the circumstances during clutch ini- tiation and incubation. We suspect that Moun- tain Chickadees initiated the nest because the cavity was lined with fur. In addition. Moun- tain Chickadees consistently fledge in 21 days (McCallum et al. 1999), whereas Red-breasted 402 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Nuthatches remain in the nest anywhere from 14 to 21 days (Ghalambor and Martin 1999); therefore, the nuthatches could have fledged before the chickadees, even if the nuthatch eggs were laid after the chickadee eggs. Last, we did not observe a male nuthatch at the nest. Given the aggressive nature of male nut- hatches and the fact that nuthatch pairs can out-compete Mountain Chickadee pairs (ARN unpubl. data), we suspect the absence of a male nuthatch was an important contributing factor in this occurrence of interspecific nest sharing. Others have reported interspecific nest shar- ing where two species laid eggs in the same nest, and in some cases, successfully fledged broods because of cooperative incubation and feeding of nestlings (Skutch 1961, Sundkvist 1979). In Norrbotten, Sweden, a pair of Pied Flycatchers (Ficedula hypoleuca) and a fe- male Common Redstart {Phoenicurus phoen- icurus) shared a nest box and successfully reared the young of both species, despite ag- gressive encounters between the species dur- ing incubation (Sundkvist 1979). Variation in timing of breeding and domi- nance can result in cross-species broods. Cav- ity-nesting Great Tits (Pams major) and Blue Tits (Parus caeruleus) regularly produce cross-species broods when the earlier-nesting, socially subordinate Blue Tits initiate clutches that are subsequently usurped by the later- nesting, but dominant. Great Tits (Slagsvold 1998). Our nest-sharing observation had some similarities to the tit example, as Mountain Chickadees are subordinate to nuthatches but tend to initiate clutches about 3 days earlier (KM, ARN unpubl. data). Because chickadees do not readily defend their territories against intrusions by nuthatches (ARN unpubl. data), the female nuthatch may not have been de- terred by territorial behavior of the chickadee pair. ACKNOWLEDGMENTS Eunding and logistics were provided by a Sustain- able Forest Management Network for Centres of Ex- cellence and a Natural Sciences and Engineering Re- search Council of Canada (NSERC) grant to K. Mar- tin. A. R. Norris was supported by an NSERC Indus- trial Post-graduate Scholarship (sponsored by Tolko Ltd.), Environment Canada’s Science Horizons Youth Internship Program, and a Southern Interior Bluebird Trail Society grant. We thank D. A. McCallum and C. K. Ghalambor for discussions about prevalence of this unusual behavior. K. A. Otter and D. A. McCallum made helpful suggestions in the revision of the man- uscript. LITERATURE CITED Aitken, K. E. H., K. L. Wiebe, and K. Martin. 2002. Nest-site reuse patterns for a cavity-nesting bird community in interior British Columbia. Auk 1 19: 391-402. Brush, T. 1983. Cavity use by secondary cavity-nest- ing birds and response to manipulations. Condor 85:461-466. Ghalambor, C. K. and T. E. Martin. 1999. Red- breasted Nuthatch {Sitta canadensis). The Birds of North America, no. 459. Holt, R. E and K. Martin. 1997. Landscape modifi- cation and patch selection: the demography of two secondary cavity nesters colonizing clearcuts. Auk 1 14:443-455. Martin, K., K. E. H. Aitken, and K. L. Wiebe. 2004. Nest sites and nest webs for cavity-nesting com- munities in interior British Columbia, Canada: nest characteristics and niche partitioning. Condor 106:5-19. Martin, K. and J. M. Eadie. 1999. Nest webs: a com- munity-wide approach to the management and conservation of cavity-nesting forest birds. Forest Ecology and Management 115:243-257. McCallum, D. A., R. Grundel, and D. L. Dahlsten. 1999. Mountain Chickadee (Poecile gambeli). The Birds of North America, no. 453. Peterson, B. and G. Gauthier. 1985. Nest site use by cavity-nesting birds of the Cariboo Parkland, Brit- ish Columbia. Wilson Bulletin 97:319-331. Skutch, A. E 1961. Helpers among birds. Condor 63: 198-226. Slagsvold, T. 1998. On the origin and rarity of inter- specific nest parasitism in birds. American Natu- ralist 152:264-272. Steeger, C. and J. Dulisse. 2002. Characteristics and dynamics of cavity nest trees in southern British Columbia. Proceedings of the Dead Wood in Western Forests Symposium, November 2-4, 1999. Reno, Nevada. Sundkvist, H. 1979. Pied Flycatcher, Ficedula hypo- leuca, and Redstart, Phoenicurus phoenicurus, breeding in the same nest-box. Var Fagelvarld 38: 106. SHORT COMMUNICATIONS 403 Wilson Bulletin 1 17(4):403^04, 2005 Nelson’s Sharp-tailed Sparrow Nest Parasitized by Brown-headed Cowbird Ted J. Nordhagen/ Matthew R Nordhagen^ and Paul Hendricks^^ ABSTRACT — On 22 July 2004, we found a Nel- son’s Sharp-tailed Sparrow (Ammodramus nelsoni) nest in Sheridan County, Montana, containing a single Brown-headed Cowbird {Molothrus ater) nestling that was about to fledge. A punctured sharp-tailed sparrow egg was found below the nest. This is the second de- finitive report of cowbird brood parasitism of a Nel- son’s Sharp-tailed Sparrow nest and the first indicating successful rearing of a cowbird by this host species. The impact of cowbird parasitism on nesting success of Nelson’s Sharp-tailed Sparrow has not been studied, but our record indicates that nest failure (i.e., produc- ing no host young) may be an outcome for some nests of this species. Received 18 January 2005, accepted 10 August 2005. During an inventory of wetland-associated bird species in northeastern Montana, we sur- veyed wetlands on McCoy Creek, Sheridan County (48° 49' 57" N, 104° 35' 36" W), in June and July 2004 to observe the activities of singing grassland sparrows found there. On 19 July, TJN and MPN saw a pair of Nelson’s Sharp-tailed Sparrows {Ammodramus nelsoni) carrying food four times and fecal sacs three times during 75 min of observation, but could not find the nest. On 22 July, TJN and MPN found the nest after watching the adults make two feeding trips to the same general area. The nest was in dense wetland vegetation of sedges (Carex spp.), rushes (Scirpus spp.), and unidentified grasses about 100 cm tall; the nest rim was 23 cm above ground. The nest was built of coarse grass and lined with finer grasses; inside cup dimensions were 3.5 cm deep and 5.0 cm in diameter, typical for nests of this species (Greenlaw and Rising 1994). The nest contained a single Brown-headed Cowbird {Molothrus ater) nestling that filled ' P.O. Box 44, Westby. MT 59275, USA. ' Montana Natural Heritage F^rogram, 909 l.ocust St., Mi.ssoula, MT 59S02, USA. 'Corresponding author; e-mail; phendricks@mt.gov the entire nest cup. The cowbird was well feathered, with sheathing present on the prox- imal two-thirds of the primaries; we estimated that it was about 8 days old, or within a few days of fledging (Scott 1979). We photo- graphed and videotaped the nest contents and surrounding area and deposited digital copies with the Montana Natural Heritage Program in Helena. On 24 July, we revisited the nest and found it empty. We assumed the cowbird nestling had fledged, but neither saw nor heard the sparrows or the cowbird during 30 min of ob- servation. We found a single, punctured sharp- tailed sparrow egg on the ground below the nest that had been overlooked on the day the nest was discovered. The egg measured 17.5 X 14.2 mm, was bluish-white in color, and was covered with numerous fine, light-brown maculations — typical in size, coloration, and markings for Nelson’s Sharp-tailed Sparrow, although slightly shorter than average (Green- law and Rising 1994). The eggs and nest of Le Conte’s Sparrow {A. leconteii) are similar (Lowther 1996) to those of Nelson’s Sharp- tailed Sparrow, and, in northeastern Montana wetlands, Le Conte’s Sparrow is sympatric with Nelson’s Sharp-tailed Sparrow (PH pers. obs.); however, we neither saw nor heard any Le Conte’s Sparrows at this site on any of our five visits. Thus, we are confident that the nest and egg belonged to the pair of Nelson's Sharp-tailed Sparrows we observed near the nest site. The nest and punctured egg were collected and deposited in the Philip L. Wright Zoological Museum at the University of Mon- tana, Missoula (UMZM 18620). Our observation of cowbird brood parasit- ism on Nelson's Sharp-tailed Sparrow is sig- nificant for several reasons, f irst, it is only the second definitive record of a cowbird parasit- izing this host species. The first was of a sin- gle cowbird egg found in a clutch of four sharp-tailed sparrow eggs near Brafulon, Man- 404 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 itoba, on 20 June 1962 (Hill 1968). In his comprehensive summary of host species, Friedmann (1963) listed an earlier, third-party recollection of an associate who found a Nel- son’s Sharp-tailed Sparrow nest containing a cowbird egg, but no additional details regard- ing date or location were provided; thus, the record is hypothetical. Second, our report is the first to confirm that this species can suc- cessfully rear a cowbird nestling (Friedmann and Kiff 1985, Greenlaw and Rising 1994, Shaffer et al. 2003). Third, our observation indicates that nest failure (i.e., producing no host young) is a possible outcome when cow- birds parasitize Nelson’s Sharp-tailed Spar- row, perhaps resulting in reproductive failure for an entire breeding season. Nelson’s Sharp-tailed Sparrow is arguably among the most poorly known of North American sparrows. In particular, very little information is available on this species’ nest- ing ecology or its habitat requirements in the northern prairie states and provinces (Green- law and Rising 1994) because the nests are notoriously difficult to locate. Therefore, the impact of parasitism by Brown-headed Cow- birds on populations of Nelson’s Sharp-tailed Sparrow in the northern Great Plains is un- known. Friedmann (1963) was probably over- ly optimistic in concluding that the nesting habitat used by Nelson’s Sharp-tailed Sparrow would buffer it from significant cowbird par- asitism. On a small North Dakota site occu- pied by both Le Conte’s and Nelson’s Sharp- tailed sparrows (Murray 1969), all five Le Conte’s Sparrow nests found were parasitized, indicating that cowbirds were active in the habitat where sharp-tailed sparrows nested. Studies of additional Nelson’s Sharp-tailed Sparrow nests may prove that cowbird para- sitism is more frequent than evidence cur- rently indicates. ACKNOWLEDGMENTS Field surveys were made possible from funds pro- vided by Montana Department of Fish, Wildlife, and Parks through a State Wildlife Grant to the Montana Natural Heritage Program; we thank J. C. Carlson for securing the grant. We are grateful to L. D. Igl for reviewing a photograph of the cowbird nestling and verifying our identification, and to L. D. Igl, P Paton, and J. D. Rising for suggestions that improved the manuscript. LITERATURE CITED Friedmann, H. 1963. Host relations of the parasitic cowbirds. U.S. National Museum Bulletin, no. 233. Smithsonian Institution, Washington, D.C. Friedmann, H. and L. F. Kief. 1985. The parasitic cowbirds and their hosts. Proceedings of the West- ern Foundation of Vertebrate Zoology 2:226-304. Greenlaw, J. S. and J. D. Rising. 1994. Sharp-tailed Sparrow (Ammodramus caudacutus). The Birds of North America, no. 112. Hill, N. P. 1968. Nelson’s Sharp-tailed Sparrow. Pages 815-819 in Life histories of North American car- dinals, grosbeaks, buntings, towhees, finches, sparrows, and allies (O. L. Austin, Jr., Ed.). U.S. National Museum Bulletin, no. 237, part 2. Lowther, P. E. 1996. Le Conte’s Sparrow {Ammodra- mus leconteii). The Birds of North America, no. 224. Murray, B. G., Jr. 1969. A comparative study of the Le Conte’s and Sharp-tailed sparrows. Auk 86: 199-231. Scott, T. W. 1979. Growth and age determination of nestling Brown-headed Cowbirds. Wilson Bulletin 91:464-466. Shaffer, J. A., C. M. Goldade, M. F. Dinkins, D. H. Johnson, L. D. Igl, and B. R. Euliss. 2003. Brown-headed Cowbirds in grasslands: their hab- itats, hosts, and response to management. Prairie Naturalist 35:145-186. SHORT COMMUNICATIONS 405 Wilson Bulletin 1 17(4):405-407, 2005 Dunking Behavior in American Crows Julie Morand-Ferron^ ABSTRACT. — Dunking behavior, the immersion of food items in water, is a relatively rare behavior in birds. I observed American Crows {Corvus brachy- rhynchos) dunking several types of food in rain pud- dles at Mont-Royal Park, Montreal, Quebec, Canada. Pieces of dry bread and unshelled peanuts were pro- vided in two experiments to test the potential effects of item size (bread) and shell softening (peanuts) on crow behavior. Crows dunked large pieces of bread more often than small ones. Dunking unshelled pea- nuts did not speed up the opening process. These ob- servations further support the suggestion that food dunking among birds facilitates food ingestion by soft- ening large, hard items. Received 3 November 2004, accepted 11 July 2005. Dunking behavior, the immersion of food items in water, is a relatively rare behavior in free-ranging birds; fewer than 40 species have been reported dunking food (Morand-Ferron et al. 2004). Prevalent among these records are members of the genera Quiscalus (5 spe- cies out of 6) and Corvus (7 species out of 43). In this paper, I describe dunking behavior in another corvid species, Corvus brachyrhyn- chos. Although well known among naturalists (C. Caffrey pers. obs.), dunking behavior in American Crows has not been reported in the literature. Reports of unusual behaviors are useful in estimating the taxonomic distribution of innovative behaviors, which can be used to test predictions in neurobiology, ecology, evo- lution, and cognition (Reader and Laland 2003). On 21 September 2003, at 1 1:00 EST, 1 ob- served a single crow pick up two pieces of dry white bread (3 X 3 cm) that had been thrown on the ground near the entrance of the Lac-aux-Castors section of Mont-Royal Park in Montreal, Quebec, Canada. The bird then flew to a nearby (10 m) rain puddle and dunked the food in it twice before eating it on ' Dept, of Biology, 1205 Docteur Penfield Ave., Mc- Gill Univ., Montreal, PQ H3A IBl, Canada; e-mail: julie.morand-ferron@mail.mcgill.ca the spot. On 23 September, I returned to the park and again witnessed a free-ranging crow dunking bread. Between 23 September and 16 October, I observed at least three different in- dividuals (birds were not marked, but some- times they dunked almost simultaneously in different puddles) dunking fresh and dry bread and unshelled peanuts. I also observed crows eating dry dog food pellets (n = 16), maraschino cherries (n = 2), and live crickets (n = 6) that I placed 8 m from the nearest rain puddle; however, I observed no crows dunk- ing these items (all previously reported as dunked by other species; see table in Morand- Ferron et al. 2004). From these observations alone, it is difficult to determine the function of dunking behavior in wild American Crows. Among the different functions suggested for this behavior in birds, using food as a sponge for bringing water to nestlings (Koenig 1985) can be ruled out be- cause the events I observed occurred many weeks after juveniles had fledged. Washing soiled food (Simmons 1950, Watkin 1950, Caldwell 1951, Jordheim 1965, Wible 1975, Johnson 1976, Seibt and Wickler 1978, Vader 1979, Zach 1979, Schardien and Jackson 1982, del Hoyo et al. 1996, Henry et al. 1998) also may be ruled out because the food items were soiled during the process of dunking clean food into muddy rainwater. I conducted two field experiments with bread and peanuts to examine two possible de- terminants of dunking: the effect of item size on the dunking frequency of bread and the advantage that dunking might offer in soft- ening peanut shells (making them easier to open). In the first set of trials, I tested the hypothesis that dunking hard food would be more prevalent with larger items (too large to be swallowed whole) than with smaller items. I provided crows (/? = 3) at Mont-Royal Park with two sizes of dry bread: small (2X2 cm, n = 16) and large (4X4 cm, n = 17). I ran one trial per day between 1 ():()() and 12:00 on 406 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 4 days in October 2003. During each trial, I recorded the behavior of crows provided with 6 to 10 pieces of bread. One piece at a time, I threw bread on the ground, alternating be- tween the two sizes each time. I noted whether the crow that took the piece dunked it in a nearby puddle (8 m away) or ate it dry. A chi- square test revealed that the large pieces were dunked more often than the small ones (58.8 versus 18.8% respectively; = 5.53, df = 1, P = 0.014). This result suggests that the size of food items might influence the frequency of dunking behavior in birds. In the second set of trials, I tested the hy- pothesis that crows dunking peanuts could ac- celerate the shelling process by softening the shell in water. The potential advantage of re- duced handling time, however, needs to be distinguished from the possibility that dunk- ing peanuts lubricates them and allows the bird to swallow them whole. I observed the latter behavior once in Ring-billed Gulls (Lar- us delawarensis) — which also have been re- ported dunking crackers (Stokes and Stokes 1985) — but not in crows. From 10:00 to 12:00 on 4 days between 26 September and 16 October 2004 and on 4 days between 7 and 14 April 2005 (n = 5 trials in 2004 and n = 6 in 2005), I provided crows with unshelled peanuts near a rain puddle (8 m away) at Mont-Royal Park. On each day, I made a sim- ilar number of observations on peanuts that crows dunked and did not dunk {n = 4-8 pea- nuts per day). I defined shelling latency as the time it took to access the seeond peanut inside a two-peanut shell, not including the time spent in loeomotion. I discarded observations where the crow did not eat the second peanut but cached it in the grass {n = 3). On average, shelling latency was 55.1 sec ± 35.7 SD when the crows dunked {n = 22) and 65.4 ± 48.6 sec when crows did not dunk the peanuts {n = 26; r = 0.818, df = 46, P = 0.42); thus, dunking did not accelerate the peanut-shelling process. After extracting them from the shell, crows sometimes dunked peanut halves in wa- ter, which resulted in removal of the peanut skin. This behavior has also been observed in Common Crackles (Quiscalus quiscula; Wible 1975). The function of dunking behavior seems to vary depending on the species performing it and the item dunked. For example, raptors kill live prey by holding it under water (e.g., Ac- cipiter nisus\ Weekley 1997). Shorebirds are thought to wash muddy items by rinsing them in water before consumption (e.g., Tringa hy- poleucos; Simmons 1950). Studies on Carib Crackles {Quiscalus lugubris) have revealed that birds dunk dry bread more often than fresh bread (Morand-Ferron et al. 2004) and that dunking hard items reduces handling time (JM-F unpubl. data); these results suggest that food dunking among Carib Crackles is a food- processing technique to facilitate the ingestion of items that otherwise would be difficult to swallow. My observations on American Crows dunking bread suggest a similar func- tion. A peculiarity of corvid dunking behavior seems to be its variability: observations indi- cate that dunking is used to transport water to nestlings {Corvus corax; Hauri 1956), drown live prey (e.g.. Pica nuttalli; Blackburn 1968), wash soiled items (e.g., Corvus caurinus; Zach 1979), and soften hard {Corvus corone; Goodwin 1986) or large items {Corvus bra- chyrhynchos; this study). My observations add to the diversity of dunking behaviors re- ported for corvids and further support Good- win’s (1986) suggestion that dunking may be a standard part of the feeding repertoire in the genus Corvus. ACKNOWLEDGMENTS I would like to thank L. Lefebvre, C. Caffrey, and two anonymous referees for helpful comments on a previous version of the paper. I am also grateful to E. Trottier for help in the field. LITERATURE CITED Blackburn, C. E 1968. Yellow-billed Magpie drowns its prey. Condor 70:281. Caldwell, J. A. 1951. Food- washing in the Water- Rail. British Birds 44:418. DEL Hoyo, J., a. Elliott, and J. Sargatal (Eds.). 1996. Handbook of the birds of the world, vol. 3: Hoatzin to auks. Lynx Edicions, Barcelona, Spain. Goodwin, D. 1986. Crows of the world, 2nd ed. British Museum, London, United Kingdom. Hauri, R. 1956. Beitrage zur biologie des kolkraben {Corvus corax). Ornithologische Beobachtungen 53:28-35. Henry, P.-Y., Y Beneat, and P. Maire. 1998. Red- shank Tringa totanus feeding on young edible frogs Rana kl. esculenta. Nos Oiseaux 45:57—58. Johnson, I. W. 1976. Washing of food by Spotless Crake. Notornis 23:357. JoRDHEiM, S. O. 1965. Unusual feeding behavior of yellowlegs. Blue Jay 23:25. SHORT COMMUNICATIONS 407 Koenig, W. D. 1985. Dunking of prey by Brewer’s Blackbirds: a novel source of water for nestlings. Condor 87:444-445. Morand-Ferron, J., L. Lefebvre, S. M. Reader, D. Sol, and S. Elvin. 2004. Dunking behaviour in Carib Crackles. Animal Behaviour 68:1267-1274. Reader, S. M. and K. N. Laland. 2003. Animal in- novation. Oxford University Press, Oxford, United Kingdom. SCHARDIEN, B. J. AND J. A. Jackson. 1982. Killdcers feeding on frogs. Wilson Bulletin 94:85-87. Seibt, U. and W. Wickler. 1978. Marabou Storks wash dung beetles. Zeitschrift fur Tierpsychologie 46:324-327. Simmons, K. E. L. 1950. Food- washing by Common Sandpiper. British Birds 43:229-230. Stokes, D. and L. Stokes. 1985. Bird song, part II. Bird Watcher’s Digest 7:54-59. Vader, W. 1979. Cleptoparasitism on Bar-tailed God- wits by Common Gulls. Fauna 32:62-65. Watkin, R. 1950. Food-washing by blackbird. British Birds 43:156. Weekley, D. R. 1997. Eurasian Sparrowhawk drown- ing Eurasian Jay. British Birds 90:524-526. WiBLE, M. W. 1975. Food washing by grackles. Wilson Bulletin 87:282-283. Zach, R. 1979. Shell dropping: decision-making and optimal foraging in Northwestern Crows. Behav- ior 68:106-177. Wilson Bulletin 1 17(4):407^09, 2005 An Apparent Case of Cooperative Hunting in Immature Northern Shrikes Kevin C. Hannah* ^ ABSTRACT. — Cooperative hunting is a behavior rarely observed in passerine birds. I observed two im- mature Northern Shrikes (Lanius excubitor invictus) apparently hunting cooperatively while preying on American Tree Sparrows (Spizella arborea) in central Alaska. During each of three foraging attempts, both shrikes appeared to work together to flush prey from dense cover into the open where it was then pursued. Cooperative hunting in this otherwise solitary species may be an adaptive behavior among inexperienced birds to increase their foraging efficiency, or to com- pensate for seasonal fluctuations in the accessibility or availability of prey. Received 6 December 2004, ac- cepted 9 July 2005. Many raptorial birds are considered solitary predators (Schoener 1969); however, more so- cial forms of foraging may be adaptive if the outcome results in increased foraging efficien- cy or compensates for fluctuations in prey populations (Packer and Ruttan 1988, Ellis et al. 1993). Cooperative hunting in mammals has been extensively documented in large, so- cial carnivores (Packer and Ruttan 1988) and some diurnal raptors (Hector 1986, Bednarz ' Alaska Bird Observatory, Box 80505, b'airbanks AK 99701, USA. ^Current address: Canadian Wildlife Service, Rm. 2(K), 4999 98th Ave., Edmonton, AB T6B 2X3, Can- ada: e-mail: Kevin. Hannah@ec.gc.ca 1988, Yosef 1991). Only rarely, however, has social foraging been reported in passerine birds (see Bowman 2003). Generally, social foraging is not thought to be a common for- aging strategy within the genus Lanius, al- though a case of cooperative hunting was ob- served in mated Loggerhead Shrikes {Lanius ludovicianus; Frye and Gerhardt 2001). In this paper, I report an apparent case of cooperative hunting by immature Northern Shrikes {Lan- ius excubitor invictus). The observation took place in Denali Na- tional Park, Alaska (63°44'N, 149° 22' W) between km 28.1 and 28.8 of Denali Park Road, near a small tributary creek of the Sav- age River. Vegetation at the site was primarily riparian, with many species of willow {Salix spp.) ranging in height from 1 to 5 m, con- trasting markedly with the surrounding vege- tation. Vegetation in the surrounding area was characteristic of the taiga/lundra interface, consisting of widely spaced, stunted 1- to 5- m-tall white spruce trees {I^icea i*lauca)\ dwarf birch {Hetula ^landulosa), willow {Sa- li.x spp.), and blueberry {Vacciniutti ulii^inos- um) were the dominant cover species. F^lleva- tion at the site was approximately 880 m, with marked topographical relief in the surrounding area. Ambient temperature at the time of the observati(ui was -4° C. 408 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 While driving along the Denali Park Road on 19 September 2003, 1 noticed two Northern Shrikes perched in close proximity to one an- other. I observed and photographed both birds from <12 m and identified them as immature birds — based on the fine dusky vermiculations on their underparts, an overall brownish ap- pearance, and grayish-brown supercilia (Cade and Atkinson 2002). As I exited my vehicle at 10:30 AST, both birds flew approximately 50 m and perched approximately 20 m apart in a thick patch of willows 3-5 m in height. Both birds then flew into the willow thicket, where I could see them sporadically as they hopped along branches. Suddenly, one of the shrikes flew up out of the thicket, chasing an American Tree Spar- row (Spizella arbored). The shrike pursued the sparrow upward, making quick, horizontal lunges at the sparrow as it continued to as- cend. After 5-6 sec, the shrike and the spar- row reached an altitude of approximately 30 m above the ground. At this point, the second shrike joined in the pursuit, with both shrikes alternately making horizontal lunges at the sparrow. After an additional 8-10 sec, the sparrow made a quick vertical descent to a willow thicket. The shrikes discontinued their pursuit of the sparrow and flew back to the original willow thicket, where they perched several meters apart near the top. One of the shrikes then began to sing irreg- ularly, uttering a series of trills and warbles as described by Cade and Atkinson (2002). After approximately 2 min, both birds flew into the willow thicket. At about 10:45, one shrike emerged from the willow thicket, chasing an American Tree Sparrow upward in much the same manner as in the previous chase. Within 5-6 sec, the second shrike joined in the pur- suit. Following several alternating horizontal lunges by the shrikes, the sparrow made a quick vertical descent and flew into dense vegetation. The two shrikes returned to the original willow thicket and flew back into cover. At 10:50, another American Tree Spar- row— pursued by both shrikes — flew up out of the thicket. In contrast to the first two pur- suits, all three birds reached an altitude of —45-50 m above the ground, and both shrikes made 10-15 horizontal lunges at the sparrow. The sparrow, which showed signs of fatigue, began a slightly more horizontal descent than the one made during the previous two chases. One of the shrikes then began a direct pursuit of the sparrow, which was flying almost com- pletely horizontally. After pursuing the spar- row for —8-10 sec, covering a distance of ap- proximately 150 m, the shrike captured the sparrow by grasping it with its bill and quick- ly transferring the prey to its feet. The shrike then flew to a large willow, perched, and bit the sparrow’s head and neck, apparently kill- ing it. At this point, the second shrike flew in, perched —5m away from the first shrike, and uttered a loud “walk” call (Cade and Atkin- son 2002). The first shrike, responding with a similar call, flew approximately 120 m to the east and perched at the top of a small spruce. The second shrike pursued the first shrike, perching nearby and again uttering the waik call. Grasping the sparrow with its feet, the first shrike flew —400-500 m farther before disappearing over a ridge, with the second shrike in pursuit. Thereafter, I was unable to refind the birds; thus, I could not determine whether the prey item was shared. Although little is known about the diet of Northern Shrikes during autumn migration, passerine birds are thought to represent only a minor portion of the summer and winter diet, in both number and biomass (Cade 1967, Atkinson and Cade 1993). Compared with other prey taxa. Northern Shrikes have very low foraging success when hunting birds (Cade and Atkinson 2002), often taking them by surprise and only rarely in flight (Cade 1967). Although insects constitute a large pro- portion of the Northern Shrike’s diet (Atkin- son and Cade 1993), the extremely cold au- tumn temperatures in this region would likely reduce their availability as potential prey. Ac- cess to small mammals — another significant part of the shrike’s diet — might be limited in dense, shrubby habitat such as that along Den- ali Park Road. Therefore, small flocks of mi- grating passerines may represent an opportu- nistic, albeit highly important food source for shrikes migrating through this area in late au- tumn. By hunting cooperatively, inexperi- enced shrikes may overwhelm or surprise elu- sive prey, thereby reducing the potential for escape and increasing hunting success. Con- sequently, social foraging may be adaptive, by increasing the foraging efficiency on this SHORT COMMUNICATIONS 409 highly elusive, though seasonally abundant food resource. According to Ellis et al. (1993), my obser- vation may represent true cooperative hunt- ing— a form known as sibling group hunting, wherein two or more sibling fledglings hunt cooperatively. Although I could not determine whether these birds were siblings, small groups of immature shrikes during the early part of autumn migration are thought to con- sist of siblings (Cade and Atkinson 2002). Whereas true cooperative hunting has never before been reported in the Northern Shrike, cooperative hunting by sibling groups may be an adaptive strategy used by younger, less ex- perienced raptorial birds to improve hunting efficiency (Packer and Ruttan 1988, Ellis et al. 1993). As individual birds develop their hunting skills and increase their foraging ef- ficiency, the need to hunt cooperatively prob- ably declines (Bosakowski and Smith 1996, Brown et al. 2004). Alternatively, as shrikes migrate farther south, other prey taxa may once again become more available and acces- sible, resulting in a smaller proportion of birds in their diet and fewer instances of social for- aging. Generally, previous accounts of coop- erative hunting in passerines, such as Com- mon Raven (Corvus corax; Hendricks and Schlang 1998), Loggerhead Shrike (Frye and Gerhardt 2001), and Florida Scrub-Jay {Aphelocoma coerulescens; Bowman 2003), have involved mated adult pairs cooperatively hunting large or dangerous prey. My obser- vation is novel in that it involved immature passerines cooperatively hunting smaller prey. Further study is required to determine the fre- quency and adaptive significance of social for- aging in passerine birds. ACKNOWLEDGMENTS E. C. Atkinson, T. A. Hannah, C. L. McIntyre, T. Swem, R. Yosef, and an anonymous reviewer provided many helpful comments on earlier drafts of this man- uscript. LITERATURE CITED Atkinson, E. C. and T. J. Cade. 1993. Winter foraging and diet composition of Northern Shrikes in Ida- ho. Condor 95:525-535. Bednarz, J. C. 1988. Cooperative hunting in Harris’ Hawks (Parabuteo unicinctus). Science 239: 1525-1527. Bosakowski, T. and D. G. Smith. 1996. Group hunting forays of wintering Northern Harriers, Circus cy- aneus: an adaptation of juveniles? Canadian Field- Naturalist 110:310-313. Bowman, R. 2003. Apparent cooperative hunting in Florida Scrub-Jays. Wilson Bulletin 115:197-199. Brown, J. L., W. R. Heinrich, J. P. Jenny, and B. D. Mutch. 2004. Development of hunting behavior in hacked Aplomado Falcons. Journal of Raptor Research 38:148-152. Cade, T. J. 1967. Ecological and behavioral aspects of predation by the Northern Shrike. Living Bird 6: 43-86. Cade, T. J. and E. C. Atkinson. 2002. Northern Shrike (Lanius excubitor). The Birds of North America, no. 671. Ellis, D. H., J. C. Bednarz, D. G. Smith, and S. P. Fleming. 1993. Social foraging classes in raptorial birds. Bioscience 43:14-20. Frye, G. G. and R. R Gerhardt. 2001. Apparent co- operative hunting in Loggerhead Shrikes. Wilson Bulletin 113:462-464. Hector, D. P. 1986. Cooperative hunting and its re- lationship to foraging success and prey size in an avian predator. Ethology 73:247-257. Hendricks, P. and S. Schlang. 1998. Aerial attacks by Common Ravens, Corvus corax, on adult feral pigeons, Columba livia. Canadian Field-Naturalist 112:702-703. Packer, C. and L. Ruttan. 1988. The evolution of cooperative hunting. American Naturalist 132: 159-198. SCHOENER, T. W. 1969. Models of optimal size for sol- itary predators. American Naturalist 103:277-313. Yosef, R. 1991. Foraging habits, hunting, and breed- ing success of Lanner Falcons {Falco biarmicus) in Israel. Journal of Raptor Research 25:77-81. 410 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Wilson Bulletin 1 17(4):410— 412, 2005 A Field Observation of the Head-down Display in the Bronzed Cowbird Kimball L. Garrett''^ and Kathy C. Molina' ABSTRACT. — We describe a photodocumented field observation in Sinaloa, Mexico, of a head-down (or “preening invitation”) display performed by a male Bronzed Cowbird {Molothrus aeneus), which elicited both grooming and pecking responses from a female Great-tailed Crackle {Quiscalus mexicanus). Previously, such displays by parasitic cowbirds and re- sponses by conspecific or various heterospecific bird species have been documented mainly under aviary conditions; most field observations have involved Brown-headed (M. ater) and Shiny (M. bonariensis) cowbirds. The function and evolutionary significance of such interspecific interactions remain elusive, but continued documentation of such occurrences may help elucidate their biological significance. Received 10 December 2004, accepted 2 August 2005. On 17 December 2003 at 08:15 MST, we observed a mixed group of icterids, including 40 Great-tailed Grackles {Quiscalus mexican- us), 20 Bronzed Cowbirds {Molothrus aene- us), and 1 Brown-headed Cowbird (M. ater), in several small palo verde {Cercidium spp.) trees along the southern shoreline of the Eus- taquio Balbuena reservoir in Guamuchil, Sin- aloa (25°28'N, 108° 06' W). Among these birds was a male Bronzed Cowbird giving a head-down display with its neck ruff flared out, matching the “interspecific preening in- vitation display” described by Selander and La Rue (1961). The bird remained very still in this position for most of our 5 -min obser- vation. A female Great-tailed Grackle spent several minutes within 5—15 cm of the cow- bird, lateral to and slightly below it, gently picking at the cowbird’s head about eight times. The grackle also delivered six slightly stronger pecks toward the Bronzed Cowbird, but did not cause the cowbird to move from its perch. At the end of this interaction, the cowbird shifted upward along the branch to a position about 30 cm from the grackle. We ' Section of Ornithology, Natural History Museum of Los Angeles County, 900 Exposition Blvd., Los An- geles, CA 90007, USA. ^ Corresponding author; e-mail; kgarrett@nhm.org could not determine whether the grackle was obtaining food items — such as ectoparasites — from the cowbird, but its bill motion was clearly that of gentle picking rather than preening through the feathers. KCM photo- graphed the display (a series of eight digital images) under clear conditions at 15° C with a very light breeze (Fig. 1). It appears that head-down displays directed by cowbirds toward — and eliciting responses from — much larger grackles are not common. Selander and La Rue (1961) described inter- specific preening invitation displays by Brown-headed Cowbirds in captive, mixed- species flocks and briefly mentioned a similar display performed by two captive Bronzed Cowbirds; these authors noted brief displays by Brown-headed Cowbirds toward female Great-tailed Grackles, which elicited no re- sponses from the grackles. Selander (1964) re- corded additional such displays to heterospe- cifics by captive Shiny (M. bonariensis) and Bay-winged cowbirds {Agelaioides [Molo- thrus] badius). Such preening invitation, or head-down (Rothstein 1977), displays are now well documented in wild Brown-headed Cow- birds (Selander and La Rue 1961, Dow 1968, Rothstein 1977, Lowther and Rothstein 1980, Hunter 1994) and in captive (Harrison 1963) and wild (Chapman 1928, Payne 1969) Giant Cowbirds (M. oryzivorus). Post and Wiley (1992) observed Shiny Cowbirds in the field directing 33 of 238 head-down displays to- ward Greater Antillean Grackles {Q. niger). Rothstein (1977) has also documented these head-down displays among conspecifics. Discussions of the function of cowbird head-down preening solicitation initially cen- tered on heterospecific functions that may re- duce the aggressiveness of cowbird host spe- cies (Selander and La Rue 1961). However, Rothstein (1977, 1980) showed that the head- down display also occurs in an intraspecific context, usually directed toward a behavior- ally subordinate individual; although he found SHORT COMMUNICATIONS 411 FIG. 1. Male Bronzed Cowbird {Molothrus aeneus, left) giving a head-down (preening invitation) display to female Great-tailed Grackle {Quiscalus mexicanus, right), 17 December 2003, Guamuchil, Sinaloa, Mexico. that the displays were motivated by aggres- sion, Rothstein (1980) reported that they were responded to as if they represented appease- ment, thus constituting a form of behavioral mimicry. A display directed by a male Bronzed Cowbird toward a female grackle is similar to a display directed to a subordinate individual (S. 1. Rothstein pers. comm.), even though the grackle is approximately 60% larg- er (Dunning 1992). Our midwinter observa- tion of this display is not consistent with Se- lander and La Rue’s (1961) argument that the display reduces interspecific aggressiveness from potential cowbird hosts. Scott and Grum- strup-Scott (1983) hypothesized that the head- down display is “an appeasing, agonistic be- havior that reduces agonistic behaviors of the recipient toward the displaying cowbird.” fhe displaying bird is generally dominant to the recipient, and preening may stimulate subse- quent displaying by the preened cowbird. These authors cite possible social functions of this display relating to obtaining footl, roost- ing energetics, and/or maintaining flock order (Scott and Grumstrup-Scott 1983). Although previous discussions about re- sponses to head-down displays (e.g., Selander and La Rue 1961) relate to heteropreening, none explicitly mentioned foraging by the “preening” bird for ectoparasites on the dis- playing cowbird. We could not determine whether ectoparasites were actually obtained during our observation, but the female grack- le s picking motions resembled foraging be- havior rather than preening. Great-tailed Grackles exhibit a wide range of foraging be- haviors (Johnson and Peer 200 1). including taking ectoparasites from livestock (Skutch 1954). fhe Common Grackle ((/• quiscuUi) also has been noted picking leeches from the legs of map turtles (Graptcnixs ouachitensis: Vogt 1979). As Rothstein (1977) (■>ointed out. observa- tions of |■)reening solicitation behaviors in cap- tive birds may not accurately reflect the con- text and funetions of such beha\ iors in the 412 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 wild. Little is known of the importance of this behavior in wild cowbirds; as such, it is im- portant to continue cataloguing the occurrence of such behavior and the identities of both the displaying bird and the recipient. Ours is among the few field observations of a head- down display performed by a Bronzed Cow- bird, and it is the first report of such a display directed by a wild cowbird toward — and elic- iting a response from — a Great-tailed Grackle. ACKNOWLEDGMENTS We thank S. I. Rothstein for his advice in the prep- aration of this note. We are greatly appreciative of the Faucett Family Foundation for providing support for our 2003 work in western Mexico. Three anonymous referees provided important critical comments that im- proved the manuscript. LITERATURE CITED Chapman, EM. 1928. The nesting habits of Wagler’s Oropendola (Zarhynchus wagleri) on Barro Col- orado Island. Bulletin of the American Museum of Natural History 58:123-166. Dow, D. D. 1968. Allopreening invitation display of a Brown-headed Cowbird to Cardinals under natural conditions. Wilson Bulletin 80:494—495. Dunning, J. B. 1992. CRC handbook of avian body masses. CRC Press, Boca Raton, Florida. Harrison, C. J. O. 1963. Interspecific preening display by the Rice Grackle, Psomocolax oryzivorus. Auk 80:373-374. Hunter, J. E. 1994. Further observations of head- down displays by Brown-headed Cowbirds. West- ern Birds 25:63-65. Johnson, K. and B. D. Peer. 2001. Great-tailed Grack- le {Quiscalus mexicanus). The Birds of North America, no. 576. Lowther, P. E. and S. I. Rothstein. 1980. Head-down or “preening invitation” displays involving juve- nile Brown-headed Cowbirds. Condor 82:459— 460. Payne, R. B. 1969. Giant Cowbird solicits preening from man. Auk 86:751-752. Post, W. and J. W. Wiley. 1992. The head-down dis- play in Shiny Cowbirds and its relation to domi- nance behavior. Condor 94:999-1002. Rothstein, S. I. 1977. The preening invitation or head- down display of parasitic cowbirds. I. Evidence for intraspecific occurrence. Condor 79:13-23. Rothstein, S. I. 1980. The preening invitation or head- down display of parasitic cowbirds. II. Experi- mental analysis and evidence for behavioural mimicry. Behaviour 75:148—184. Scott, T. W. and J. M. Grumstrup-Scott. 1983. Why do Brown-headed Cowbirds perform the head- down display? Auk 100:139-148. Selander, R. K. 1964. Behavior of captive South American cowbirds. Auk 81:394-402. Selander, R. K. and C. J. La Rue, Jr. 1961. Inter- specific preening invitation display of parasitic cowbirds. Auk 78:473-504. Skutch, a. F. 1954. Life histories of Central American birds, vol. 1. Pacific Coast Avifauna, no. 31. Vogt, R. C. 1979. Cleaning/feeding symbiosis be- tween grackles {Quiscalus: Icteridae) and map tur- tles {Graptemys: Emydidae). Auk 96:608-609. SHORT COMMUNICATIONS 413 Wilson Bulletin 1 17(4):413-415, 2005 Filial Cannibalism at a House Finch Nest William M. Gilbert,' ^ Paul M. Nolan,^^ Andrew M. Stoehr,^'* and Geoffrey E. HilP ABSTRACT. — We report on a female House Finch {Carpodacus mexicanus) eating one of her own eggs from a clutch of six on the 3rd day of incubation. This observation is a confirmed case of filial cannibalism in the egg stage. The reason for this behavior is unknown, but we suggest and discuss three possibilities: (1) an idiosyncratic response to human disturbance, (2) re- moval of a damaged egg from the nest, and (3) fac- ultative brood reduction in the egg stage. Received 12 January 2004, accepted 15 July 2005. There are relatively few records in the lit- erature of birds eating their own eggs, and we could find reports of this behavior for only seven species. The proximate causes for “fil- ial cannibalism” in the egg stage (Stanback and Koenig 1992) can be classified as adap- tive or nonadaptive. Adaptive behaviors in- clude eating one’s own infertile (presumably) eggs that remain in the nest beyond normal incubation time (Walsh 1964, Berger 1981, Stiehl 1985, Banko et al. 2002), or eating eggs that have been damaged (Trail et al. 1981). In addition, female Acorn Woodpeckers {Mela- nerpes formicivorus) occasionally participate in eating their own eggs after those eggs have been removed from shared nests as an integral part of a unique, but apparently adaptive, communal breeding system (Mumme et al. 1983). In contrast, Chardine and Morris (1983) reported a presumably nonadaptive egg-eating behavior in Herring Gulls {Larus argentatus) after observing two males brood- ing at different nests eat their own eggs (at one nest, all eggs were eaten). This apparently abnormal behavior in the two males was at- ' 3745 Highland Rd., Lafayette, CA 94549, USA. ^ Dept, of Biological ,Sciences, Auburn Univ., Au- burn, AL 36849, USA. ’Current address: Dept, of Biology, Ithaca College Ithaca, NY 14850, USA. ■‘Current address: Dept, of Biology, Univ. of Cali- fornia, Riverside, CA 92521, USA. ’Corresponding author; e-mail: wmglbrt@aol.com tributed, respectively, to a possible displace- ment response caused by a female gull return- ing late to her nest to brood, and to a possible idiosyncratic reaction to human disturbance. Here, we report on a female House Finch {Carpodacus mexicanus) that ate a single egg from her clutch of six on the 3rd day of in- cubation. Timing of egg laying indicated that the egg was not laid by another House Finch (intraspecific brood parasitism is not known for the species; Hill 1993). We have no evi- dence that the eaten egg had been damaged, and it did not appear deformed, discolored, or undersized. We describe circumstances asso- ciated with the egg-eating event, and discuss possible causes for the behavior. METHODS Observations were made on the campus of Auburn University, Auburn, Alabama, where wooden nest platforms (12 X 13 X 8 cm) were maintained under walkways and eaves of buildings. These platforms were open at the top and on one side and were designed to ac- cept the bottom portion of 1.9-1 plastic milk or juice containers (held in place by metal clips), which served as nest boxes. House Finches readily accepted the platform design, and typically built >60 nests each year at the study site. At various stages of the breeding cycle, video cameras were placed near some of the nests, usually <2 m away. These cam- eras provided good-quality video sequences, viewable with a freeze-frame feature. The vid- eo camera recording the event reported here was placed ~ 1 .5 m from the nest at an acute angle from vertical, thus providing an excel- lent view. The House Finch pair at this nest was banded with a distinct combination of color bands that were readily identifiable in the videotape. Each day, we examined tho.se nests in which egg laying was occurring by using a mirror on an extended pole. We marked eggs at the large end with a nontoxic marker to 414 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 indicate laying order. While examining nests for newly laid eggs, we were able to closely examine the upper sides of all eggs; eggs re- moved from nests during marking were thor- oughly inspected by hand. After clutches were complete, we inspected nests every 2 days us- ing a mirror on a pole. OBSERVATIONS The video camera at the House Finch nest site recorded the following events at 08:35 EST on 19 April 1997, the approximate start of the 3rd day of incubation (n ^ 6 eggs). The resident male landed at the nest and briefly fed the resident female. Both birds then flew off for about 30 sec. The resident female, posi- tively identified in the video by her color bands, then returned to the nest and appeared to inspect the nest contents. She then bit into one of the eggs and began to eat it. She con- tinued eating for approximately 3 min and then perched on the edge of the nest for about 1 min with the eggshell in her beak. She then flew off, carrying the eggshell with her. Subsequent examination showed that the egg had been the third one laid. It was 6 days old when eaten, had been incubated for 2 days, and was normal in size, shape, and color. The six eggs in the clutch were laid at 1-day intervals over 5 days. After the egg-eating event, no additional eggs were lost from the nest, and the pair hatched and fledged the re- maining five young. Six-egg clutches made up only 5.5% (12/ 217) of all clutches observed at the study site, whereas five-egg clutches composed 55% (119/217), four-egg clutches 29% (63/217), and three-egg clutches 5% (11/217). The male of the pair was 2 years old; the female’s age was unknown. Our records do not indicate whether we had hand-inspected the eaten egg after the day it was marked, but all eggs had been viewed from above. We observed no de- fects in any of the six eggs from the time the final egg was laid through the time of camera installation early on 19 April; videotape re- cordings made before the egg-eating event also revealed no defects. DISCUSSION The egg-eating event we report represents a case of filial cannibalism in the egg stage (Stanback and Koenig 1992), a behavior for which there are few published records for birds. We propose three possible explanations for this behavior. First, it may have been an idiosyncratic, and presumably nonadaptive, response by the female House Finch, perhaps to human disturbance (Chardine and Morris 1983). The most likely human disturbance would have been the placement of the video camera on the morning the egg was eaten. However, video cameras had been placed near 63 other House Finch nests during the study with no apparent abnormal responses (PMN unpubl. data). Also, two other nests from which single eggs disappeared did not have cameras placed near them. Second, the female House Finch may have eaten one of her eggs because it had been damaged, perhaps punctured, during marking. There is at least one published report of a fe- male bird eating one of her own eggs after it was damaged (Trail et al. 1981). However, we detected no damage to the egg, and even if the female House Finch had detected damage unnoticed by us, it is uncertain that she would have removed and eaten the egg. Third, the female House Finch may have eaten one of her own eggs to reduce the size of her clutch. Six-egg clutches in House Finches are rare (5.5% of total), whereas four- and five-egg clutches are common. Clutch siz- es larger than normal could be a trigger for female House Finches to remove eggs. In fact, the proportion of single eggs disappearing from six-egg clutches (2/12; including the six- egg clutch discussed above) differed from the proportion disappearing from smaller clutches (1/205; from a five-egg clutch; Fisher exact test, P = 0.008; PMN unpubl. data). When brood reduction occurs in bird nests, it usually happens during the nestling stage, and sometimes involves filial cannibalism (e.g., Ricklefs 1965, Ohmart 1973, O’Conner 1978, Mock and Parker 1986). In some Eudyptes penguin species, brood reduction regularly oc- curs in the egg stage, but it does not involve filial cannibalism (St. Clair et al. 1995). In some non-avian taxa, however, brood reduction occurs in the egg stage and involves filial can- nibalism (Mock and Parker 1997). Our observation of a House Finch eating her own egg is a confirmed case of filial cannibal- ism in the egg stage. However, we were unable to determine whether it was (1) an idiosyn- SHORT COMMUNICATIONS 415 cratic, nonadaptive response, presumably due to human disturbance; (2) an adaptive response to eliminate a damaged egg; or (3) an adaptive response to reduce clutch size. Studies of House Finch responses to disturbances near ac- tive nests, deliberate egg puncturing, and arti- ficial increases in clutch size would shed light on the causes of filial cannibalism in House Finches. ACKNOWLEDGMENTS We thank R. Dyer, S. Horn, S. Lovell, R. Shurette, and W. Underwood for assistance in the field, and S. Forbes, W. D. Koenig, D. W. Mock, and an anonymous reviewer for helpful comments on the manuscript. This research was supported by a grant from the National Science Foundation (Grant No. IBN9722171 to GEH). LITERATURE CITED Banko, P. C., D. L. Ball, and W. E. Banko. 2002. Hawaiian Crow (Corvus hawaiiensis). The Birds of North America, no. 648. Berger, A. J. 1981. Hawaiian birdlife, 2nd ed. Uni- versity of Hawaii Press, Honolulu. Chardine, J. W. and R. D. Morris. 1983. Herring Gull males eat their own eggs. Wilson Bulletin 95:477- 478. Hill, G. E. 1993. House Finch (Carpodacus mexican- us). The Birds of North America, no. 46. Mock, D. W. and G. A. Parker. 1986. Advantages and disadvantages of egret and heron brood re- duction. Evolution 40:459-470. Mock, D. W. and G. A. Parker. 1997. The evolution of sibling rivalry. Oxford University Press, Ox- ford, United Kingdom. Mumme, R. L., W. D. Koenig, and F. A. Pitelka. 1983. Reproductive competition in the communal Acorn Woodpecker: sisters destroy each other’s eggs. Nature 306:583-584. O’Conner, R. J. 1978. Brood reduction in birds: se- lection for fratricide, infanticide, and suicide. An- imal Behaviour 26:79-96. Ohmart, R. D. 1973. Observations on the breeding ad- aptations of the Roadrunner. Condor 75:140-149. Ricklefs, R. E. 1965. Brood reduction in the Curve- billed Thrasher. Condor 67:505-510. St. Clair, C. C., J. R. Waas, R. C. St. Clair, and P. T. Boag. 1995. Unfit mothers? Maternal infanti- cide in Royal Penguins. Animal Behaviour 50- 1177-1185. Stanback, M. T. and W. D. Koenig. 1992. Cannibal- ism in birds. Pages 277-298 in Cannibalism: ecol- ogy and evolution among diverse taxa (M. A. El- gar and B. J. Crespi, Eds.). Oxford Science Pub- lications, Oxford, United Kingdom. Stiehl, R. B. 1985. Brood chronology of the Common Raven. Wilson Bulletin 103:83-92. Trail, P. W, S. D. Strahl, and J. L. Brown. 1981. Infanticide in relation to individual and flock his- tories in a communally breeding bird, the Mexican Jay (Aphelocoma ultramarina). American Natu- ralist 118:72-82. Walsh, T. P. 1964. Blackbird eating own eggs. British Birds 57:436. Wilson Bulletin 1 17(4):415^1 8, 2005 An Observation of Foliage-bathing by an Orange-breasted Falcon (Falco deiroleucus) in Tikal, Guatemala Knut Eisermann' ABSTRACT. — 1 ob.served a pair of Orange-breasted Falcons {Falco deiroleucus) in Tikal, Guatemala, on 30 December 2003 and 1 January 2004. I ob.served the birds flying through wet foliage as a means of bathing, which has not been described previously for this spe- cies. During a morning with light rain, an adult falcon took off from a perch, flew low over the forest canopy, and appeared to crash intentionally into the wet. upper foliage ot emergent trees before returning to its perch. 1 ob.served three repetitions of this behavior. Received 16 November 2004, accepted 13 July 2005. ' PO. Box 098, F^erif^rico, Guatemala City, Guate- mala; e-mail: knut.eisermann@cayaya-birding.com The Orange-breasted Falcon {Falco deiro- leucu.s) is a little known and rare Neotropical falcon (Collaret al. 1994, Baker 1998, Baker et al. 2()()(), Thorstrom et al. 2002). Using a 10 X 42 binocular, I observed a pair of Orange-breasted Falcons in Tikal, Peten, Gua- temala (17° 14' N, 89° 37' W) on 30 Decem- ber 2003 and on 1 January 2004. This species is often confu.sed in the field with the Bat Fal- con {Falco rufi^ularis: Jenny and Cade 1986, Howell and Whittaker 1995; D. F Whitacre in litt.). However, the bird's bulky shape, which re.sembles that of a Peregrine Falcon (/•'. per- 416 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 egrinus), and its extensively orange chest al- lowed me to make a positive identification (photographs of one of the Orange-breasted Falcons described herein are available online at http://www.cayaya-birding.comypubs.htm). Tikal is an ancient Mayan city, characterized today by pyramids (up to 65 m tall) surround- ed by semi-deciduous lowland broadleaf for- est. Ascending some of the pyramids permits a view over the forest canopy, which is —30 m tall. Dispersed emergent trees rise 15 m above the canopy. Nesting of the Orange- breasted Falcon in the ancient Mayan build- ings of Tikal has been reported by Smithe (1966), Boyce (1980), and Baker et al. (2000). The initiation of courtship in northern Peten and Belize occurs in January and February (Baker 1998). On 30 December 2003, at 09:00 CST, I ob- served courtship behavior of a pair of Orange- breasted Falcons from —30 m away in the “Lost World” complex of Tikal. When first observed, one falcon — perched on a branch stub in the upper part of a 40-m-tall tree — left a piece of an unidentified bird prey item be- fore flying off. The second bird then landed on the prey and began feeding on it. I assumed the second bird was the female, because prey transfers are reported to occur from male to female (Baker 1998). I never saw both birds close enough to each other to judge size dif- ferences (females are larger than males; How- ell and Whittaker 1995, Baker 1998). Because both falcons were vocalizing from tree perch- es —40 m apart, the size and color pattern of both birds appeared to be similar. Prey trans- fers were also observed on several days in April 2004 at the entrance of the assumed nesting cavity on Temple IV, 500 m northwest of the Lost World complex (M. Cordova pers. comm.) On 1 January 2004, at approximately 08:00, I observed foliage-bathing behavior from where I was standing at the upper landing of Temple IV in Tikal. During a light rain, one Orange-breasted Falcon perched on top of a snag, 300 m away from the temple, and a sec- ond falcon perched on the top of the temple, where I detected it by its calls; I was unable to distinguish the gender of either bird. The falcon that was perched on the snag flew off low over the canopy. It gained elevation be- fore reaching an emergent tree and crashing into the wet upper foliage. What appeared at first to be accidental turned out to be an in- tentional behavior that I interpreted as bath- ing. The falcon continued flying and again crashed into the upper foliage of another emergent tree —200 m away before returning to its original perch, where it shook and re- peatedly ruffled its feathers. I did not observe any active preening. After several minutes, the same falcon flew off again and crashed twice more into the same group of trees. I observed this behavior three times over a period of 10 min. An obvious splashing of water drops was visible during each crash. Sometimes the fal- con stretched out its legs shortly before reach- ing the emergent tree and grasped a twig, let- ting itself fall into the wet foliage before con- tinuing the straight-line flight into the next tree. The possibility that the observed behavior was an unusual way of capturing prey almost certainly can be excluded, because I did not see the falcon holding anything in its feet when it left the tree, nor was it eating during the flight or on the perch after landing again. Given that the observation was made at the beginning of the breeding season, the spectac- ular crashing was possibly part of courtship behavior. Jenny and Cade (1986) and Baker (1998) found that females spend most of their time near the nest area during courtship and incubation, and males deliver food to them. The observed bathing might have been a male’s display flight — an advertisement of its fitness for obtaining prey during the nesting season. Baker (1998) described display flights as strong flapping flights in front of cliffs — with rare rolling to either side — and diving flights obviously not directed at prey. There appear to be no published descrip- tions of bathing behavior in Orange-breasted Falcons, although a similar bathing behavior has been described by Meinecke (1993) for a Eurasian Hobby (Falco subbuteo), which was flying in circles around two solitary broadleaf trees during a light rain. That falcon repeat- edly clung to the outer twigs, letting itself fall — with wings spread — into the wet foliage beneath. Griinhagen (1983) observed two ju- venile Eurasian Hobbys falling into wet fo- liage, although it appeared that the birds fell because the small twigs on which they had perched could not support them. Barreto SHORT COMMUNICATIONS 417 (1968) reported a captive Bat Falcon bathing by rubbing against wet foliage. Most reports of bathing falcons are based on observations of ground bathing in shallow water (Taverner 1919, Fischer 1977, Heller 1985, Christen 1986, Holthuijzen et al. 1987, Glutz von Blotzheim et al. 1989, Sodhi et al. 1993, Clum and Cade 1994, del Hoyo et al. 1994, Keddy-Hector 2000, Smallwood and Bird 2002, White et al. 2002). The few reports of other bathing strategies during flight in- clude a Peregrine Falcon flying through mist from waterfalls (White et al. 2002) and a Eur- asian Hobby and a Peregrine Falcon flying through a light rain (Fiuczynski 1988 and Fi- scher 1977, respectively). Ristow et al. (1980) reported juvenile Eleonora’s Falcons {F. eleo- norae) bathing in the rain while standing in their nest, and Sodhi et al. (1993) reported a Merlin {F. columbarius) bathing in the rain with its wings and tail extended. Falcons (Falco spp.) are generally consid- ered birds of open habitats (del Hoyo et al. 1994). Although the Orange-breasted Falcon is restricted to tropical forest (Cade 1982), it mainly uses the open space over the canopy and that along nearby rock cliffs and rivers (Jenny and Cade 1986, Whittaker 1996, Baker et al. 2000). Small pools of water occur near Tikal, but there are no larger water bodies of- fering open space. To my knowledge, the Orange-breasted Falcon has not been reported to enter the forest below the canopy, and it seems unlikely that the birds would bathe at small pools within the forest, entering a hab- itat unfamiliar to them. Therefore, it appears that bathing in rain and foliage, or in puddles on top of the Mayan ruins, are the only alter- natives for Orange-breasted Falcons in Tikal. ACKNOWLEDGMENTS S. Toussaint, L. F. Kiff, T. Rosenberry, G. Eiser- mann, and M. A. Echeverry provided access to some of the cited references, an invaluable support for res- idents in developing countries. I am thankful to I). E Whitacre, A. J. Baker, S. C. Latta, and C. Avendaho lor critical comments on the manuscript. I appreciate the improvements in English usage made by I). M. Brooks through the Association of Field Ornitholo- gists’ program of editorial assistance. LITERATURE CITED Bakf.r, a. J. 1998. Status and breeding biology, ecol- ogy, and behavior of the Orange-breasted Falcon {Falco deiroleucus) in Guatemala and Belize. M.Sc. thesis, Brigham Young University, Provo, Utah. Baker, A. J., D. F. Whitacre, O. Aguirre B., and C. White. 2000. The Orange-breasted Falcon Falco deiroleucus in Mesoamerica: a disjunct, vulnera- ble population. Bird Conservation International 10:29-40. Barreto, A. T. 1968. Observaciones sobre comporta- miento y muda en cautiverio de Falco rufigularis rufigularis. Lozania (Acta Zoologica Colombiana) 19:1-8. Boyce, D. A., Jr. 1980. Hunting and prenesting be- havior of the Orange-breasted Falcon. Raptor Re- search 14:35-39. Cade, T. J. 1982. The falcons of the world. Comstock/ Cornell University Press, Ithaca, New York. Christen, W. 1986. Weitere Beobachtung badender Wanderfalken {Falco peregrinus). Ornithologis- che Mitteilungen 38:122. [In German] Clum, N. J. and T. J. Cade. 1994. Gyrfalcon {Falco rusticolus). The Birds of North America, no. 1 14. Collar, N. J., M. J. Crosby, and A. J. Stattersfield. 1994. Birds to watch 2: the world list of threat- ened birds. BirdLife Conservation Series, no. 4. BirdLife International, Cambridge, United King- dom. DEL Hoyo, J., A. Elliott, and J. Sargatal (Eds.). 1994. Handbook of the birds of the world, vol. 2: New World vultures to guineafowl. Lynx Edi- cions, Barcelona, Spain. Fischer, W. 1977. Der ^Vanderfalk, Falco peregrinus und Falco peregrinoides. 4. Auflage. Die Neue Brehm Bucherei. A. Ziemsen Verlag, Wittenberg Lutherstadt, Germany. [In German] Fiuczynski, D. 1988. Der Baumfalke, Falco suhhuteo. Die Neue Brehm Bucherei. A. Ziemsen Verlag, Wittenberg Lutherstadt, Germany. [In German] Glutz von Blotzheim, U., K. M. Bauer, and E. Bez- ZEL. 1989. Handbuch der Vogel Mitteleuropas. Band 4, Ealconiformes. 2. Auflage. Aula- Verlag, Wiesbaden, Germany. [In German] Grunhagen, H. 1983. Laubbadende Baumfalken. Charadrius 19:124—125. [In German] Heller, M. 1985. Freilandbeobachtung eines baden- den Wanderfalken {Falco peregrinus). (Jrnitholo- gi.sche Mitteilungen 37:301. [In German] Holthuijzen, A. M. A., P. A. Duley, .1. C. Hagar. S. A. Smith, and K. N. W(X)d. 1987. Bathing be- havior of nesting Prairie Falcons {Falco tne.xican- us) in southwestern Idaho. Wilson Bulletin 99- 135-136. Howell, S. N. G. and A. Whittaker. 1995. Field identilication of Orange-breasted and Bat falcons. C'otinga 4:36-43. Jenny, J. P. ANt) T. .1. C’ade. 1986. Observations on the biology of the Orange-breasted Falcon Falco dei- roleucus. Birds of Prey Bulletin 3:1 19-124. KEDtiY-llECTOR. D. P. 2(MM). Aplomado Falcon {Falco femoralis). The Birds of North America, no. 549. Meinecke. H. 1993. Beobachtung eines laubbadenden 418 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Baumfalken {Falco subbuteo). Okologie der Vo- gel 15:115-118. [In German] Ristow, D., C. Wink, and M. Wink. 1980. The bathing behaviour of Eleonora’s Falcon. Bird Study 27: 54-56. Smallwood, J. A. and D. M. Bird. 2002. American Kestrel {Falco sparverius). The Birds of North America, no. 602. Smithe, E B. 1966. The birds of Tikal. Natural History Press, New York. SoDHi, N. S., L. W. Oliphant, P. C. James, and I. G. Warkentin. 1993. Merlin {Falco columbarius). The Birds of North America, no. 44. Taverner, P. A. 1919. The birds of Red Deer River, Alberta. Auk 36:1-21. Thorstrom, R., R. Watson, A. Baker, S. Ayers, and D. L. Anderson. 2002. Preliminary ground and aerial surveys for Orange-breasted Falcons in Central America. Journal of Raptor Research 36: 39-44. White, C. M., N. J. Glum, T. J. Cade, and W. G. Hunt. 2002. Peregrine Falcon {Falco peregrinus). The Birds of North America, no. 660. Whittaker, A. 1996. First record of the Orange- breasted Falcon Falco deiroleucus in central Am- azonian Brazil, with short behavioural notes. Co- tinga 6:65-68. Wilson Bulletin 1 17(4):418^20, 2005 Bare-necked Umbrellabird {Cephalopterus glabricollis) Foraging at an Unusually Large Assemblage of Army Ant-following Birds Johel Chaves-Campos^’2 ABSTRACT. — I observed a juvenile male Bare- necked Umbrellabird {Cephalopterus glabricollis) for- age on arthropods flushed by a large swarm of the army ant Eciton burchellii in the Caribbean foothills of Costa Rica. Apparently, this is the first report of this species attending an army ant swarm. At least 60 birds of eight different species were foraging at that swarm, the largest assemblage of army ant-following birds re- ported in the Neotropics. Received 13 October 2004, accepted 1 July 2005. The Bare-necked Umbrellabird {Cephalop- terus glabricollis’, Cotingidae) is an elevation- al migrant endemic to forests of the Caribbean slope of Costa Rica and western Panama (Snow 1982, Ridgely and Gwynne 1989, Stiles and Skutch 1989). Entire populations of this species spend the breeding season (Feb- ruary-July) in the highlands and then migrate to the lowlands, where they remain for at least 6 months (Chaves-Campos et al. 2003). The species feeds on fruit, large arthropods, and small vertebrates (Snow 1982, Ridgely and Gwynne 1989, Stiles and Skutch 1989; JC-C ' Fscuela de Biologia, Univ. de Costa Rica, San Jose, Costa Rica. 2 Current address: Dept, of Biological Sciences, Pur- due Univ., West Lafayette, IN 47907, USA; e-mail: jchavesc@costarricense.cr pers. obs.). The possibility of extinction is high because of recent destruction and/or frag- mentation of lowland habitats (Benstead et al. 2004), which may severely reduce the avail- ability of food sources for populations during the nonbreeding season; however, little is known about the diet of this species when it inhabits the lowlands (Chaves-Campos et al. 2003). Documenting food resources could promote conservation strategies designed to protect this species. On 13 January 1999, from 08:00 to 09:15 CST, in the foothills of the Tilaran Moun- tains, Costa Rica, I watched a juvenile male Bare-necked Umbrellabird forage over a swarm of army ants {Eciton burchellii’, see Bolton 1995). The site was located at 400 m above sea level, the lowest elevation where forest still remains on the Caribbean slope of the Tilaran mountain range (see Chaves- Campos et al. 2003 for a description of the site). The bird perched on tree branches 3-4 m above ground, catching large arthropods flushed by a column of ants that climbed the tree trunk above the main swarm. This swarm was particularly large (about 12 m wide) and the assemblage of ant-following birds was noteworthy. Although it was difficult to es- timate the numbers of foraging birds due to SHORT COMMUNICATIONS 419 their constant movement, I estimated at least 20 Ocellated Antbirds (Phaenostictus mcleannani), 10 Bicolored Antbirds {Gym- nopithys leucaspis), 10 Spotted Antbirds {Hylophylax naevioides), and 10 Plain-brown Woodcreepers {Dendrocincla fuliginosa) at- tending the swarm at the same time. In ad- dition, I recorded a few Northern Barred- Woodcreepers (Dendrocolaptes sanctitho- mae). Rufous Motmots {Baryphthengus mar- tii), and White-fronted Nunbirds {Monasa morphoeus). This is the largest assemblage of army ant- following birds reported for the Neotropical area, comparable only with assemblages of African birds at large swarms of Dorylus spp. driver ants (E. O. Willis pers. comm.). Large assemblages of army ant-following birds in the Neotropics are usually composed of no more than 20-30 individuals (Oniki 1971, Gochfeld and Tudor 1978, Dobbs and Martin 1998, Wrege et al. 2005; JC-C pers. obs.). The simultaneous presence of 10 or more ob- ligate ant-following birds of the same species at the same swarm also constitutes an ex- traordinary event (see Swartz 2001, Chaves- Campos 2003, Willson 2004). The observa- tion of a Bare-necked Umbrellabird is unusu- al as well. To the best of my knowledge, this is the first report of a Bare-necked Umbrellabird for- aging at a swarm of army ants. Members of the family Cotingidae rarely follow army ants, perhaps because they generally do not inhabit, or forage in, the forest understory (Willis 1983, Willis and Oniki 1992). However, Bare- necked Umbrellabirds sometimes eat fruits close to the forest floor (I— 3 m above ground; JC-C pers. obs.), suggesting that they might be more inclined to take prey flushed by swarms of army ants than other cotingids (e.g., more so than cock-of-the-rock Rupicoki spp., which occasionally forage at army ant swarms; E. O. Willis pers. comm.). Thus, the presence of the Bare-necked Umbrellabird at this swarm suggests that it might be an oc- casional ant follower. The absence of previous reports regarding Bare-necked UFiibrellabirds in association with swarms of army ants could be due to a number of factors: low abundance and small geographic range for this birti species, char- acteristic elevational fiiigratory behavior, and/ or the lack of research conducted on umbrel- labirds during seasons when they inhabit the lowlands. I sampled umbrellabird abundance seven times during 1998-1999 (see Chaves- Campos et al. 2003), and this was the only occasion on which I saw army ants. I speculate that Bare-necked Umbrellabirds may follow swarms of army ants primarily during the nonbreeding season, when the um- brellabirds are in the lowlands. Army ants seem to flush more insects in the lowlands than in the highlands (JC-C pers. obs.), prob- ably because the abundance and size of their colonies decreases with increasing elevation (Hilty 1974, Gochfeld and Tudor 1978). In ad- dition, they seem to flush more insects during the rainy season (Willis and Oniki 1992) — particularly on trees (Willson 2004) — when Bare-necked Umbrellabirds migrate to the lowlands (Chaves-Campos et al. 2003). ACKNOWLEDGMENTS I thank A. M. Class, E. O. Willis, and three anon- ymous referees for their comments on an earlier ver- sion of this note. LITERATURE CITED Benstead, R, J. Eckstrom, and R. G. Pople. 2004. Threatened birds of the world 2004 (rev.). CD- ROM. BirdLife International, Cambridge, United Kingdom. Bolton, B. 1995. A new general catalogue of the ants of the world. Harvard University Press, Cam- bridge, Massachusetts. Chaves-Campos, J. 2003. Localization of army-ant swarms by ant-following birds on the Caribbean slope of Costa Rica: following the vocalization of antbirds to find the swarms. Ornitologfa Neotrop- ical 14:289-294. Chaves-Campos, J., J. E. Arevalo, and M. Araya. 2003. Altitudinal movements and con.servation of the Bare-necked LJmbrellabird {Cephciloptcrus filahricollis) of the Tilaran Mountains, Costa Rica. Bird Con.servation International 13:45-58. Dobbs, R. C. and P. R. Martin. 1998. Migrant bird participation at an army ant swarm in montane ■lalisco, Mexico. Wilson Bulletin 1 10:293-295. Ckk'Hiti.d, M. and Ci. Tudor. 1978. Ant-following birds in South American subtropical forests. Wil- son Bulletin 90: 139-141. llii.iY, S. L. 1974. Notes on birds at swarms of army ants in the highlands of Colombia. Wilson Bulle- tin 86:479 481. Oniki, Y. 1971. Waiulering interspecific flocks in re- lation to ant-following birds at Belem. Brazil. C'ondor 73:372-374. Rifkili Y. R. S. ANF) J. A. Gwynnf;. Jr. 1989. A guide 420 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 to the birds of Panama with Costa Rica, Nicara- gua, and Honduras. Princeton University Press, Princeton, New Jersey. Snow, D. W. 1982. The Cotingas. Cornell University Press, Ithaca, New York. Stiles, E G. and A. E Skutch. 1989. A guide to the birds of Costa Rica. Cornell University Press, Ith- aca, New York. Swartz, M. B. 2001. Bivouac checking, a novel be- havior distinguishing obligate from opportunistic species of army-ant-following birds. Condor 103: 629-633. Willis, E. O. 1983. Flycatchers, cotingas, and dron- gos (Tyrannidae, Muscicapidae, Cotingidae, and Dicruridae) as ant followers. Gerfaut 73:265- 280. Willis, E. O. and Y. Oniki. 1992. As aves e as for- migas de correi^ao. Boletim do Museu Paraense Emilio Goeldi Serie Zoologia 8:123-150. Willson, S. K. 2004. Obligate army-ant-following birds: a study of ecology, spatial movement pat- terns, and behavior in Amazonian Peru. Ornitho- logical Monographs, no. 55. Wrege, P. H., M. Wikelski, J. T. Mandel, T. Ras- SWEILER, AND I. D. CouziN. 2005. Antbirds para- sitize foraging army ants. Ecology 86:555-559. Wilson Bulletin 1 17(4):421-427, 2005 Ornithological Literature Edited by Mary Gustafson THE REMARKABLE LIFE OF WILLIAM BEEBE: EXPLORER AND NATURALIST By Carol Grant Gould. Island Press, Washing- ton, D.C. 2004: 447 pp., numerous photos, in- dex. ISBN: 1559638583. $30 (cloth). — In this biography, Carol Grant Gould chronicles the long, productive life of William (Will) Bee- be— a man with a driven personality, one who suffered from bouts of depression, but who was usually charming and charismatic — a complicated but insightful person. Gould had at her disposal Beebe’s journals that he wrote from boyhood to old age, and the personal papers of Jocelyn Crane, Beebe’s colleague and companion during Beebe’s later years. These documents, not available to earlier bi- ographers, allowed Gould to present new in- sights into the life of William Beebe and into the changes in natural history studies and fo- cus that occurred as the Victorian era came to a close and natural history matured during the first half of the twentieth century. Gould de- scribes the scientific aspects of Beebe’s work effectively and handles the difficult personal aspects of his life — such as his estrangement from his first wife — with sensitivity, thus pro- jecting a very credible story of a remarkable ornithologist and natural historian. The book is divided into four parts: Natu- ralist, Ornithologist, Marine Biologist, and Tropical Ecologist. Part I, Naturalist, traces Beebe’s life from his birth in 1877 through his formative years as he developed an obsession for all things natural; he collected everything from seashells to stuffed birds while “bug- ging” and “fossiling” with his friends. He at- tended Columbia University, where he was mentored by Henry Fairfield Osborn, prepared bird skins, and was sponsored for membership in the American Ornithologists’ Union by Frank Chapman. He eventually left Columbia to take a job tending birds at the new Bronx Zoo. Part II, Ornithologist, covers Beebe’s early ornithological exploits. In 1904 he married, and his honeymoon consisted of a rugged ex- pedition to Mexico that resulted in the publi- cation of his first book. Two Bird Lovers in Mexico (1905, Houghton Mifflin, Boston, Massachusetts). Beebe became a prolific writ- er, producing 24 books and hundreds of sci- entific papers and popular articles. In 1906, he published The Bird: Its Form and Function (Henry Holt, Garden City, New York). Most of his books had at least some focus on birds. Under Osborn’s mentorship, Beebe became a favorite of the New York Zoological Soci- ety, which directed the Bronx Zoo, and through lectures and articles, he became well known to the high society that funded major projects, including scientific expeditions. Bee- be also had a strong relationship with the American Museum of Natural History, and became a confidant of Theodore Roosevelt. All this led to funding for a series of expe- ditions to northern South America, and an ex- pedition around the world to study pheasants for more than a year. That trip culminated in his four volumes: A Monograph of the Pheas- ants (1918—1922, H. F. Witherby, London, United Kingdom). Other tropical adventures involved establishing a research station in what was then British Guiana, where he col- lected animals for the Bronx Zoo and con- ducted research on a broad spectrum of ani- mals and plants. Although his first love was always birds, he was the consummate natural historian. World War I disrupted his adventure in British Guiana, as he trained pilots for the war and eventually flew over the battle zones ot France. After the war, he returned to British Guiana to set up another tropical research sta- tion under the auspices of the New York Zoo- logical Society. Part III, Marine Biologist, deals with Bee- be’s adventures in marine biology, especially his descent in the bathysphere to more than a half mile below the surface of the Atlantic Ocean near Bermuda. This earned Beebe in- ternational notoriety. With Part IV, Tropical Ecologist, we return to an ornithological and more general focus on natural history. During and alter World War II, Beebe established sev- eral research stations, culminating with Ran- 421 422 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 cho Grande, a cliffside ruin in the Andes west of Caracas. Three winters at Rancho Grande led to one of Beebe’s best books. High Jungle (1949, Duell, Sloan and Pearce, New York). Jocelyn Crane did most of the searching for a new research station and found one in Trini- dad that Beebe bought and donated to the New York Zoological Society. Simla, as Bee- be named the estate, became his major place of residence for the remainder of his life. Bee- be invited a succession of researchers to Sim- la, including Konrad Lorenz, Barbara and Da- vid Snow, Lincoln Brower, and Donald Grif- fin. In 1962, with Jocelyn by his side, Beebe succumbed to pneumonia. In the Epilogue, Gould comments on Bee- be’s contributions to science: “The effects William Beebe had on science . . . are enor- mous and lasting. He made an effective tran- sition between Victorian natural historian, content to collect and classify the natural world, and the modern experimental biologist. . . . His early conviction of the truth of Dar- win’s theory of natural selection shaped his enquiry into the lives of pheasants, the em- bryology of fish, and the phenomenon of mimicry, and led him to make pioneering studies of selection on the Galapagos.” In ad- dition, through his popular books and papers, Beebe influenced several generations to de- velop an interest in natural history. As a boy, I read most of Beebe’s books and was strongly influenced by them. In 1961, I was privileged to spend an afternoon with William Beebe and Jocelyn Crane at Simla and listen to him re- count many of the stories I had read in his books a decade before. This book is well written, thorough, and a great read. The Selected Bibliography just scratches the surface of Beebe’s writings, but another section. Books and Articles by Other Authors, includes Robert Welker’s previous biography Natural Man: The Life of William Beebe (1975, Indiana University Press, Bloo- mington) and Tim Berra’s William Beebe: An Annotated Bibliography (1977, Archon Books, Hamden, Connecticut) for those who wish to delve deeper into the life of this fas- cinating man. For those with a biographical bent, this is a must read. — WILLIAM E. DA- VIS, JR., Boston University, Boston, Massa- chusetts; e-mail: wedavis@bu.edu HANDBOOK OF WESTERN AUSTRA- LIAN BIRDS, VOLUME II: PASSERINES (BLUE- WINGED PITTA TO GOLDFINCH). By R. E. Johnstone and G. M. Storr. Western Australian Museum, Perth. 2004: 529 pp., 28 color egg plates, 34 color bird plates, numer- ous line drawings, 3 appendices. ISBN: 1920843116. A$130 (cloth). — Western Aus- tralia, one of seven Australian states, occupies about a third of the Australian continent, and is characterized by an entirely different cli- mate and vegetation in its northern and south- ern sections. Its climatic zones range from hu- mid to desert. Hence, the avifauna varies from resident to migratory to nomadic, and occu- pies three zoogeographic divisions: northern tropical, southwestern temperate, and central arid zones. Detailed descriptions of climate, physical features, vegetation, and a general discussion of Western Australian avifauna are not included in this volume because they were covered thoroughly in volume I (1998); it does, however, include maps of the three zones and a map depicting biogeographical re- gions and botanical provinces. This volume summarizes what is known about the 255 spe- cies and subspecies of passerine birds that oc- cur there. The book is large (23 X 32 cm) and lav- ishly illustrated. Species accounts occupy the bulk of the book (364 pp.). Each of the 32 families is described briefly, usually with two or three sentences. The species accounts are thorough and comprehensive, drawing on thousands of records and measurements of all specimens in the Western Australian Museum plus many other collections. Species accounts typically include names in past and current us- age; a description of plumage; measurements of weight and total length; distribution, habi- tat, and status; food habits and diet; breeding biology; vocalizations; geographic variation and taxonomy; and relationships with other species. Whether a bird is resident, migratory, or nomadic is discussed under Status, and for- aging behavior is covered under Food. Inter- esting behaviors, such as communal roosting in woodswallows {Artamus spp.), are present- ed in a section of Remarks. Range maps show the distributions of subspecies, hybrid zones, and wintering and breeding areas, with arrows indicating migration or nomadic movements. Excellent line drawings by Martin Thompson ORNITHOLOGICAL LITERATURE 423 and Trish Wright of nests for nearly all breed- ing species accompany the species accounts. The color plates by Martin Thompson are out- standing and depict plumage differences among sexes, age groups, subspecies, and geographical differences, with up to 10 im- ages per species. The egg plates consist of col- or photographs of egg clutches, presented ac- tual size, and often including four or five clutches per species. Three appendices follow the species ac- counts. Appendix A is an annotated checklist of Christmas Island birds. Christmas Island is 1,400 km from Western Australia but is ad- ministered by the Commonwealth of Austra- lia. The island has 23 breeding species and 104 visitors and vagrants. The 37 pages of Appendix A consist mostly of species ac- counts and four colored plates painted by John Darnell. Appendix B is an annotated checklist of Cocos-Keeling Islands birds, consisting of 18 pages of species accounts. Appendix C contains species accounts of birds reported for Western Australia since 1998, when volume I of the handbook was published. A glossary, a gazetteer of Western Australian locations, a bibliography of nearly 500 titles, and an index conclude the volume. I find little to criticize in this book, but the lack of in-text citations (a sacrifice to read- ability, I presume) makes it difficult to match references in the bibliography with individual species. I also would like to have seen the bibliography contain a more complete set of references to bird behavior and community structure. Aside from these details, this is a handsomely produced, well-written, and ex- haustively researched book. It should be part of every academic library and the library of anyone who has a serious interest in Austra- lian birds.— WILLIAM E. DAVIS, JR., Bos- ton University, Boston, Massachusetts; e-mail: wedavis@bu.edu THE BIRDS OF AZERBAIJAN. By Mi- chael Patrikeev. Edited by Geoffrey H. Harp- er. Pensoft vSeries Faunistica No. 38, Sofia, Bulgaria. 2004: 380 pp., 241 distribution Fuaps, 6 graphs, 80 photographs (3 black/ white, 77 colored). ISBN: 954642207X. $85.16 (cloth). This large-format (21.5 X 28.5 cm), remarkably informative book is the first monographic description of Azerbaijan birds. The author claims that it is not a comprehen- sive handbook, but it is scholarly and primar- ily a broad historical, biogeographical, and ecological treatment. It is a welcome and needed addition to the ornithology of this fas- cinating, and hitherto little known, area of the southern Palearctic. Azerbaijan is a relatively small country of 86,000 km^ in Eastern Trans- caucasia, bordering the western shore of the Caspian Sea. The book contains no species- specific measurements or identification de- scriptions, but this information is readily available from numerous European field guides. What it does contain is valuable fun- damental knowledge, and guidance and en- couragement for future bird conservation and management. The author’s hope seems to be that birds will do for Azerbaijan what they have done for other countries: contribute to protecting not only the avifauna Tut also the resources needed to rehabilitate and sustain healthy ecosystems. The book begins with a geographic descrip- tion of the country and its associated avian habitats, a historical review of Azerbaijan or- nithology, an overview of the country’s avi- fauna from the mid- 1800s to the late 1900s, and a description of seven avifaunal geo- graphic regions and subregions. It then pro- vides a revealing assessment of bird conser- vation in this developing nation, one with a diverse birdlife and extraordinary human tur- moil. The species accounts follow and include most of the text (pp. 35-284). The accounts include summaries of distribution (usually in- cluding a map), population size, movements, breeding ecology, diet, causes of moitality, behavior, and status (abundance, endangeied or declining, seasonal occuiTence, and taxon- omy). The photographic plates, piesented without obvious oiganization, depict selected habitats, nests, and (locks or individual biids. The photo of the Calandia Lark {Mehuwco- rypha caUuuira) nest containing young is cer- tainly one of the most striking examples of concealment. Eight appendices follow the plates and in- clude ( I ) a systematic species list containing information on abundance and seasonal oc- cunence; (2) a description of 51 Impoitant Biid Areas (IB As) that, for select I BAs, in- 424 THE WILSON BULLETIN • VoL 117, No. 4, December 2005 elude tables detailing numbers of birds per species over time; (3) a list of colonial water- birds at selected wetlands — primarily for three prominent sites (Kalinovsky Liman-Lopatin- sky Marsh, Lake Aggel, Lake Mahmud-cha- la) — for whieh numbers of birds by species are tabulated and for which graphs of changes in species composition over time are present- ed; (4) a description of waterfowl hunting; (5- 6) an assessment of the consequences of cold winters and oil pollution for birds; (7) a glos- sary of Azeri and Russian words used in the text; and (8) a comparison of spelling differ- ences for geographic names published in the text and used in standard atlases. Following the appendices is an extensive reference sec- tion containing many non-English citations, the titles of which are translated into English. The work concludes with indices of species’ English and scientific names. We learn from Patrikeev that in 1773, S. G. Gmelin made the earliest documented ornitho- logical observations in Azerbaijan. In the ear- ly 1800s, E. Menetries was the first naturalist to eollect specimens, describing three new species: Marbled Teal {Mannar onetta angus- tirostris), Bimaculated Lark {Melanocorypha bimaculata), and Menetries ’s Warbler (Sylvia mystacea). In the mid- 1800s, the Italian E deFilippi collected specimens in what is now Azerbaijan, and the Caucasian Museum was established in what is now Tbilisi, Georgia; its first curator, Gustav Radde (a German in Russian service), and his successor, K. A. Sa- tunin, studied the avifauna throughout the Caucasus region, ineluding Azerbaijan, in the early 1900s. From the 1930s to the 1960s, K. Gambarov of the Institute of Zoology, Acad- emy of Science of Azerbaijan, conducted bird studies, ineluding the first to address the ef- fects of oil pollution. From 1950 to 1970, sev- eral authors focused primarily on the study of economically important species. During the 1960s to 1980s, Gara Mustafaev of Azerbaijan University (Baku) was the leading avian re- searcher investigating the nation’s avifauna. Patrikeev ’s principal fieldwork occurred from 1988 to 1991, and most of what is in The Birds of Azerbaijan are his previously unpub- lished results of that period. Although bird study has a long history in Azerbaijan, even increasing in modern times, most of the coun- try awaits detailed ornithological attention, which promises intriguing discoveries. Currently, 372 bird species (17 orders and 58 families) have been recorded in Azerbai- jan; they comprise 107 permanent residents, 139 summer residents, 95 migrants and winter residents, 28 accidentals, and 3 extirpated spe- cies. Another eight species are unconfirmed. Historic and current threats to the country’s birds include hunting, habitat loss or degra- dation, pollution, and depredation. Sacred Ibis (Threskiornis aethiopicus), Lanner Falcon (Falco biarmicus), and Pin-tailed Sandgrouse (Pterocles alchata) are thought to be extirpat- ed. There also are 9 endangered, 11 threat- ened, 39 rare, and 10 vulnerable species; in addition, 10 have restricted ranges, there is in- sufficient information for 14, and 12 no longer breed and 2 no longer overwinter in the coun- try. Among the common species, 12 are de- clining, 8 are increasing, and 7 are undergoing range extensions. From the 1950s to present, four new species have nested and four others were recorded in the country for the first time. Patrikeev informs us that species with positive population trends are wide-ranging and toler- ant of human activities, whereas species whose populations are declining or are already greatly diminished have specific habitat re- quirements or are intolerant of habitat degra- dation. About 5% of Azerbaijan’s land is designat- ed as nature reserves (185,000 ha) and game preserves (250,000 ha) that purport to protect birds and other life within their borders. Pa- trikeev then disappointingly describes how laws are abused or ignored throughout the country, primarily because of paralyzing eco- nomic and political instability. Poachers open- ly take birds and other animals from protected areas; in 1989-1990, 600-700 poachers at one reserve hunted waterfowl without limit, and hunting overall continues unabated or un- regulated. The extravagant toll that oil pollu- tion is taking on birds and the entire Caspian Sea eeosystem is gravely alarming. Moreover, we learn that the Azerbaijan government pol- icy toward natural resource conservation re- mains unknown, and, by inference, it appears that conservation education is meager to non- existent in schools or for the general public. Still, Patrikeev hopes that government stabil- ity and a core of committed citizens will de- ORNITHOLOGICAL LITERATURE 425 velop, eventually resulting in effective protec- tion for all the nation’s natural resources. There are a few typos, some notable omis- sions (such as the incomplete numbering of photographs), and no pagination on the plates (pp. 289-318; page numbers for the plates are in the indices). Notwithstanding these slips, the work is relatively error free. Despite the seemingly random order of the plates, they are attractive and instructive. The distribution maps can be difficult to interpret because the shades designating different occurrence areas (main wintering grounds, other wintering grounds, historical wintering areas) are similar enough to be confusing when viewing one map after another, or when viewing several maps over several different pages where only some of the shading categories are used. Al- though breeding locations are distinctly noted, breeding ranges are unclear, as there are no labels denoting breeding ranges in the map legends. Aside from these shortcomings, this book is an outstanding achievement and a valuable contribution to bird study in a part of the world that is, to date, only modestly known to most ornithologists and other bird students, especially in the West. In my view, this work is a must for institutional libraries every- where, but especially for teaching and re- search institutions, for conservation profes- sionals interested in birds, and for those in- terested in conserving the natural world in de- veloping countries. The plates give one a good sense of the landscape and depict some of Azerbaijan’s most attractive birds. The book will appeal to all readers, especially those who will visit Azerbaijan to birdwatch when it is safe to do so. — DANIEL KLEM, JR., Muhl- enberg College, Allentown, Pennsylvania; e-mail: klem@muhlenberg.edu SHOREBIRDS OF NORTH AMERICA: THE PHOTOGRAPHIC GUIDE. By Dennis R. Paulson. Princeton University Press, Princeton, New Jersey. 2005: 384 pp., 534 color photographs. ISBN: 0691102740, $65 (cloth). ISBN: 0691 121079, $29.95 (paper).— As stated in the preface of this new guide, shorebirds are among our most engaging birds. Their ecology and behavior are the sub- jects of numerous ornithological studies, their identification can challenge the skills of the most serious birdwatchers, and people with a casual interest in birds are captivated by the antics of Sanderlings {Calidris alba) chasing waves along a beach. While some books pro- vide a worldwide perspective on shorebird identification, this book is the first guide de- voted solely to identifying every species oc- curring in North America. Its coverage is truly continental, extending from Alaska to Panama and including the West Indies. This book is strictly an identification guide. The Introduction contains information on top- ics such as anatomy, molt, sexual variation, behavior, and vocalizations, but these topics are addressed within the context of how they pertain to the field identification of shorebirds. Most of the text is devoted to accounts for the 94 species that have been sighted in North America, beginning with Double-striped Thick-knee (Burhinus bistriatus) and ending with Oriental Pratincole (Glareola fnaldivar- um). To the author’s credit, the same level of in- formation is provided for every species, re- gardless of its status in North America. The 1-2 pages of text per account cover size, sub- species, plumages, in-flight characteristics, voice, behavior, habitat, and distribution. The amount of detail included in the plumage de- scriptions varies among species but tends to- ward statements emphasizing general distin- guishing characteristics rather than feather-by- feather details. Each account is accompanied by a series of color photographs illustrating the various plumages and field marks. Most species are portrayed in 4-7 photos, with as many as I 1 for a tew species with complex plumage patterns or that pose considerable field-identification challenges. These photos are invariably of excellent quality and the col- or reproduction appears very good, at least to my eye. The captions discuss specific field marks evident in each photograph, frequently covering details not mentioned elsewhere in the account, fhe book ends with a 3-page list of references, which is by no means a com- plete compilation of the relevant shorebird identification literature. My biggest complaint is the failure to sum- marize the key identification features for a species in (me easily located section of each 426 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 account. The identification information is def- initely provided, but the user may have to wade through the identification, plumage, and possibly subspecies sections and every photo caption to gather all of the pertinent details — no easy task when struggling with the identi- fication of a difficult shorebird in the field. Other criticisms are relatively minor. No sub- species descriptions were provided for Greater Sand-Plover (Charadrius leschenaultii), a se- rious omission when needing to separate some races of this species from potentially similar races of the Lesser Sand-Plover (C. mongo- lus) — a problem most North American birders can only dream about. Similar flaws are rare. The amount of information would likely overwhelm a true beginner who should prob- ably use a field guide with fewer details. How- ever, for novice to expert birders with a pas- sion for shorebirds, this book will likely be- come their standard identification reference. — BRUCE PETERJOHN, USGS Patuxent Wild- life Research Center, Laurel, Maryland; e-mail: bpeterjohn@usgs.gov PIPITS AND WAGTAILS. By Per Alstrom and Krister Mild, illustrated by Per Alstrom and Bill Zetterstrom. Princeton University Press, Princeton, New Jersey. 2003: 496 pp., 30 color plates, and 240 color photographs in 40 plates. ISBN: 0691088349. $67.50 (cloth). — This book covers two closely relat- ed, but rather disparate, groups of birds: the wagtails — spectacular and charismatic, usual- ly brightly colored in blacks and yellows or strikingly patterned in black and white; and the pipits — no less engaging, but whose plum- age is invariably streaked or spotted brown. Wagtails rarely present identification prob- lems; by contrast, more ink and bile has been expended, and more reputations made or lost, on pipit identification (they are famous va- grants) than on almost any other group of birds. To quote some amusing doggerel first published many years ago in the Ringers’ Bul- letin (the house magazine of British bird band- ing), “It’s a pity that the pipits have / No di- agnostic features, / Specifically they are the least / Distinctive of God’s creatures.” The book begins with a useful introduction, including such “nuts and bolts” items as spe- cies concepts (biological versus phylogenetic), the terminology applied to sonograms and to- pography, a glossary of technical terms, com- prehensive treatments of molt and ageing, and nomenclature. Some of these sections, all clearly written and of general application, should be compulsory reading for any first- year student of ornithology, with or without any specific interest in this family of birds. Thirty color plates follow the introduction, with 7-17 illustrations on each plate. Given that fewer than 30 species are covered, the plates are enormously detailed and compre- hensive. Special care has been taken to group together species easily confused during iden- tification, with many figures positioned to em- phasize plumage features of the back and face that would be missed in the conventional broadside postures of most field guides. The quality of artwork is consistently high and the two artists work together seamlessly. The bulk of the book (331 pages) is devoted to individual species accounts. These vary in length from 3 pages for the little-known Ber- thelot’s Pipit {Anthus berthelotii) — endemic to the Canaries and Madeira — to 49 pages for the White Wagtail (Motacilla alba) complex. Spe- cies accounts include sections on distribution; identification (which, given the racial com- plexity of some species, is itself a study); de- tailed plumage descriptions for all ages and both sexes of the nominate race, followed by highly detailed treatments of geographic var- iation; systematics, molt, ageing, and sexing; and behavior, distribution, and habitat. There are large sections in each species account on voice, which are major studies in their own right; for the White Wagtail complex there are 43 individual sonograms, and for the Yellow Wagtail, 34. Many readers will find these a little excessive, but for any serious student they will be the definitive study. What is not given in the species accounts is any treatment of nests and eggs, which would indeed have been of interest to the more general reader, albeit at the expense of making the book larg- er and more expensive. A distribution map ac- companies each species; in contrast to so many other works, the maps have been pre- pared with extreme care and much attention to detail (e.g., the two superbly detailed maps for the Long-billed Pipit, Anthus similis), with political boundaries and major rivers marked. ORNITHOLOGICAL LITERATURE 427 making interpretation easy. For some species, maps of wintering ranges — separated accord- ing to subspecies — are also provided. My main criticism of the section on Distribution (which includes information about migration) is that for several species, such as White or Yellow wagtails, it would have been greatly enhanced by reference to the large database of recoveries that exists for birds banded not only in Europe but also, to a lesser extent, in Israel and East Africa. One pleasing feature of the book is how references have been treated; in many other books of this type, references are clustered to- gether at the end of a species account, making it impossible to link individual references to a specific statement in the text. That is not the case in this book; although an Additional Lit- erature section is given at the end of each species account, individual references are linked to specific statements — a practice that all such works should follow. Given that the bibliography runs to about 500 individual ci- tations, how they are presented is a major is- sue. Toward the end of the book are 40 pages of photographs, 6 per page, accompanied by explanatory text; additionally, there are more sets of photographs embedded in the text, il- lustrating such things as the wing patterns on the flight feathers of wagtails. These photo- graphs are especially useful in combination with the painted illustrations, which depict birds in ideal postures. In the real world, birds are rarely that cooperative. The photographs, with all the usual variations in lighting, back- ground, and activity, give a more realistic idea of the problems with pipit identification, lest the reader get an impression that it is too easy! In fact, in the introduction, the authors show two photographs of the same individual Pad- dyfield Pipit {Anthus rufulus) in different at- titudes, Just to make that very same point. In short. Pipits and Wagtails is a monu- mental piece of scholarship, with a scope and attention to detail rarely found in such works; in fact. New World ornithologists will regret that it did not include the small number of pipits found in South America, which clearly need such a treatment. This book will un- doubtedly be the definitive study of this charming group of birds for many years to come. — DAVID BREWER, Puslinch, Ontar- io, Canada; e-mail: mbrewer@albedo.net Wilson Bulletin 1 17(4):428-441, 2005 PROCEEDINGS OE THE EIGHTY-SIXTH ANNUAL MEETING SARA R. MORRIS, SECRETARY The eighty-sixth annual meeting of the Wilson Or- nithological Society was held Thursday, 21 April, through Sunday, 24 April 2005, at the Sheraton Hotel in Beltsville, Maryland, in joint session with the As- sociation of Field Ornithologists. The meeting was hosted by the U.S. Geological Survey (USGS) Patux- ent Wildlife Research Center and the Maryland Orni- thological Society, in cooperation with Friends of Pa- tuxent, the U.S. Fish and Wildlife Service (USFWS) Patuxent National Wildlife Visitor Center, and the Uni- versity of Maryland, Baltimore County. The Local Committee was co-chaired by Richard C. Banks and Jay M. Sheppard and included Nell Baldacchino, Rog- er B. Clapp, Alicia Craig, Deanna Dawson, Mercedes S. Foster, Mary Gustafson, Judd Howell, Joseph R. Jehl, Jr., Janet Millenson, Kevin Omland, Keith Par- dieck, Bruce Peterjohn, Chandler S. Robbins, Jeff Spendelow, and Monica Tomosy. Additional assistance during the meeting was provided by Evelyn Adkins, Claudia Angle, Sarah Bennett, Kinard Boone, Fred Fallon, Regina Fanning, Jerry Persall, Luther Poell- nitz, Fred Shaffer, Rachel Sturge, Marilyn Whitehead, and the Friends of Patuxent Volunteers. Alicia Craig organized and coordinated the electronic presentations for the paper sessions and Liz Humphries, Chris Hof- mann, Beatrice Kondo, Spring Ligi, Anne Logie, and Bryan Rosensteele served as projectionists and tech- nical support staff. The Council met from 13:10 to 17:45 in the Severn Room and again from 20:30 to 21:57 in the Wye Salon on Thursday, 21 April, at the Sheraton Hotel. That evening there was an opening reception in the Sus- quehanna-Potomac Ballroom from 18:00 to 21:00. Early morning field trips were led on Friday, 22 April, to Greenbelt National Park and Greenbelt by Dave Mozurkewich, Lake Artemesia— Greenbelt by Fred Shaffer, historical sights and sea duck facility of the Patuxent Wildlife Research Center by Matthew Perry, and the Whooping Crane breeding and reintro- duction facility of the Patuxent Wildlife Research Cen- ter by Kathy O’Malley. On Saturday, 23 April, early morning trips included Lake Artemesia led by Fred Shaffer, the central tract of the Patuxent Wildlife Re- search Center led by Fred and Jane Fallon and Barbara Dowell, and a Jug Bay boat trip led by Greg Kearns. Post meeting trips on Sunday, 24 April, included Ft. Smallwood Park-Prince Georges County led by David Mozurkewich and Fred Fallon, the C & O Canal at Seneca/Sycamore Landing led by Jim Stasz and Ed Boyd, and a pelagic trip led by Mary Gustafson and Paul and Anita Guris. On Friday, 22 April, Dick Banks, Co-chair of the Local Committee, welcomed guests to the Susquehan- na-Potomac-Patuxent Room at the Sheraton Hotel. Dick Banks then introduced Judd Howe, Director of the Patuxent Wildlife Research Center, who welcomed attendees and provided some of the ornithological his- tory of the center, including its role as the home of the Breeding Bird Survey and the Bird Banding Labora- tory. Gene Morton, President of the Association of Field Ornithologists, and Charles Blem, President of the Wilson Ornithological Society, welcomed attend- ees on behalf of the two societies. Jay Sheppard, Co- chair of the Local Committee, made several announce- ments about room changes, transportation for the post- er session, and a request that students pick up their banquet tickets during the business meeting. Jim Ris- ing, Chair of the Scientific Program, asked that attend- ees check the errata sheet for changes to the scientific program. Jed Burtt provided background on Margaret Morse Nice and introduced Dr. Eugene S. Morton of Smithsonian Migratory Bird Center and Dr. Bridget J. M. Stutchbury of York University, who presented the ninth annual Margaret Morse Nice Plenary Lecture. Their lecture “Territoriality . . . Beyond the Temperate Zone” discussed territoriality, extra-pair paternity, and breeding synchrony in both the temperate and tropical zones in an attempt to break out of the temperate zone bias. Two concurrent paper sessions were presented in the Severn-Lochraven Room and the Potomac-Susque- hanna Rooms throughout the remainder of the scien- tific program. In addition to the Nice lecture, the sci- entific program included 76 contributed papers, orga- nized into 10 paper sessions and 2 symposia — “Breed- ing Bird Survey” and “The Unselfish Gene: Honoring E. S. Morton’s Contributions to Ornithology” — and 41 contributed posters. The societies co-sponsored a student luncheon with “senior ornithologists” for 50 students at lunch on Fri- day. Friday evening, conferees attended the poster ses- sion and buffet reception at the Patuxent National Wildlife Refuge Visitors Center. Poster presenters were assigned to present their posters during half of the ses- sion, which provided additional room to view posters and fostered discussion. On Saturday evening, a social hour preceded the annual banquet in the Ballroom of the Sheraton Hotel. After the dinner, Dick Banks thanked the local com- mittee and all the individuals who had made the meet- ing a success. To present the Association of Field Or- nithologists’ awards. Gene Morton introduced Don Kroodsma, who presented the Bergstrom Awards, and Elissa Landre, who presented the Alexander Skutch Award. President Charles Blem briefly addressed the conferees, thanking Dick and Jay for hosting the meet- ing, the Local Committee for their service, and the Scientific Program Committee for a successful meet- ing. He thanked the retiring Members of Council for their service, welcomed the new Members of Council, and thanked all committee members for their hard 428 ANNUAL REPORT 429 work. At that time the awards and commendations that follow were presented by Jed Burtt (Margaret Morse Nice Medal), Charles Blem (Student Research Awards), Doris Watt (Student Presentation Awards), and Bob Curry (Commendations). The Student Travel Awards and Commendations for John Smallwood and Martha Vaughan were presented at the Business Meet- ing. The meeting was adjourned by acclamation at 20:58. MARGARET MORSE NICE MEDAL (for the WOS plenary lecture) Dr. Eugene S. Morton and Dr. Bridget J. M. Stutch- bury, “Territoriality . . . Beyond the Temperate Zone.” LOUIS AGASSIZ FUERTES AWARD Joel W. McGlothlin, Indiana University, “Phenotyp- ic integration of sexually selected traits in Dark- eyed Juncos {Junco hyemalis)." PAUL A. STEWART AWARDS Julian Avery, Eastern New Mexico University, “The effects of habitat fragmentation on land- scape-level processes and habitat associations of Nearctic-Neotropical migratory birds in New Mexico.” Aaron Ted Boone, Ohio State University, “Linking winter and migration events in a long-distance migratory songbird using stable-carbon isotope analysis.” Christy Anne Melhart, University of Arkansas, “Re- productive success and philopatry of Prairie War- blers, Blue-winged Warblers, Indigo Buntings, and Field Sparrows in declining scrub succession- al habitat in Connecticut.” Colin E. Studds, University of Maryland, “Linking non-breeding habitat occupancy to population proces.ses in a Neotropical-Nearctic migratory bird.” WILSON 0RNITH0L(K;ICAL SOCIETY STUDENT TRAVEL AWARDS Colleen Bell, Canisius College, “A crash course in communications tower mortality; birds dying to become a statistic in western New York.” Kristen M. Covino. Canisius College, “Getting to the point: rectrix shape morphometries in age dis- crimination of Ovenbirds.” Michael E Gaydos, Xavier Lhiivcrsity, “F actors af- fecting parental nest attendance in Northern Mockingbirds (Minms poly^lotto.s)." Gct)rge S. IFamaoui. Jr., Ohio Wesleyan University, “Analysis of feather-degradation by liaciUus lich- cniformis from the plumage of Botteri's Sparrows living in wet and dry habitats in Ari/ona.” Jennifer McNicoll, New Mexico Slate University, “Burrowing Owl nest site selection on the Janos- Nuevo Casas Grandes, Mexico prairie dog com- plex.” Jennifer Newbrey, North Dakota State University, “Effects of nest contents and minimum daily tem- perature on female Yellow-headed Blackbird nest attentiveness.” Karan Odom, Ohio Wesleyan University, “Differ- ences between vocalizations of wild-reared and human-reared birds of prey as an indication of learning within call development of owls and ea- gles.” Ashley M. Peele, Ohio Wesleyan University, “Feather damage in an albino Greater Frigate- bird.” Jennifer Smolinski, Xavier University, “Numerical competence in wild Northern Mockingbirds {Mi- nins polyglottos)." Rachel Sturge, University of Toronto, “The effects of habitat loss on the Savannah Sparrows {Pas- sercLihis sandwichensis) of La Perouse Bay, Man- itoba.” Rebecca Suomala, University of New Hampshire, “Comparison of species distribution and habitat use during stopover on two islands in the Gulf of Maine.” Jennifer Urbanski, Canisius College, “Is shorter bet- ter? Does truncation increase the utility of open population models in stopover estimation?” Kate E. Williamson, Ohio Wesleyan University, “The microbial ecology in the plumage of Neo- tropical migrants.” ALEXANDER WILSON PRIZE (for the best student paper) Christopher Hofmann, University of Maryland-Bal- timore County, “Pigment co-deposition and the masking of carotenoids in Orchard and Fuertes's orioles.” LYNDS JONES PRIZE (for the best student poster) Beth A. Hahn, University of Michigan, “Using song playbacks to influence breeding habitat selection by American Redstarts.” Selection committee for the Nice Medal — William E. Davis, Jr. (Chair), Charles Blem, James Rising, and Doris Walt; for the I-ueries and Steuart Awards - Ixann Blem (Chair), Charles Blem, Cdail Braun. Dale Gawlik, Dale Kennedy. Dan Klein. David Podlesak. Craig Rudolph, and Doug White; for the Wilson Or- nithological Society Travel Awards — Leann Blem (('hair); and for the Student Presentation Awards Doris Watt (( hair). Alicia ( raig. Bob Beason. Sandra Gaunt, and John Smallwood. COMMENDATION WHIiRI'AS John A. Smallwood accepted the chal- lenge of moving from his role as Secretary of the Wilson Ornithologieal Society to assume the post of 430 THE WILSON BULLETIN • Vol. 1 17, No. 4, December 2005 Editor of The Wilson Bulletin at the start of the new millennium; and WHEREAS he served as Editor for the years 2001- 2003 and oversaw completion of volumes 113, 114, and 115; and WHEREAS John approached his duties with diligent effort, hard work, and careful attention to the quality of the Society’s premiere publication; THEREFORE BE IT RESOLVED that the Wilson Or- nithological Society thanks John Smallwood for his important and valuable service to the Society. COMMENDATION WHEREAS Martha Vaughan served diligently as the Treasurer of the Wilson Ornithological Society over the past four years; and RECOGNIZING that Martha brought to the position a degree of professionalism that has greatly increased the Society’s ability to conduct operations, finances, and audits in a manner that fully reflects the orga- nization’s fiduciary responsibilities; and RECOGNIZING that these improvements to the finan- cial operations of the Society, by being instituted coincident with the doubling of the endowment through the William and Nancy Klamm bequest, represent an especially valuable contribution to the Society; THEREFORE BE IT RESOLVED that the Wilson Or- nithological Society expresses sincere gratitude to Martha for her important service to the Society. COMMENDATION WHEREAS Charles R. Blem served the Wilson Or- nithological Society as its President for the past two years with honor and distinction; and RECOGNIZING that this service represents the con- tinuation of many years of dedicated contributions to the Wilson Ornithological Society in many ca- pacities; and RECOGNIZING that under Charles’s leadership, the Wilson Ornithological Society began evaluating its opportunities and responsibilities in light of receipt of the William and Nancy Klamm bequest, which increased the Society’s endowment twofold; and RECOGNIZING that during his term as President, the Wilson Ornithological Society has initiated a period of reinvigoration and new direction, as exemplified by changing the name of the Bulletin to the Wilson Journal of Ornithology, THEREFORE BE IT RESOLVED that the Wilson Or- nithological Society extends its thanks to Charles for his friendship and service to the Society. COMMENDATION WHEREAS the Wilson Ornithological Society and the Association of Field Ornithologists jointly held their annual meetings in Beltsville, Maryland, with the sponsorship of the Patuxent Wildlife Research Cen- ter, USGS, and the Maryland Ornithological Socie- ty; and RECOGNIZING that the Friends of Patuxent, the Na- tional Wildlife Visitor Center of the USFWS, and the University of Maryland-Baltimore County made important contributions as meeting cooperators, fa- cilitating the conduct of the scientific program, spe- cial events, and field trips; and RECOGNIZING that attendance at the joint meeting was large and diverse, with notable involvement of graduate and undergraduate students as presenters and as volunteers, including especially the dedicated efforts of projectionists Liz Humphries, Chris Hof- mann, Beatrice Kondo, and Spring Ligi; and RECOGNIZING that the Chair of the Scientific Pro- gram Committee, Jim Rising, arranged a rich and extensive program of oral presentations, posters, and symposia; and RECOGNIZING that the Committee on Local Ar- rangements, chaired by Dick Banks with assistance especially from Jay Sheppard and a host of others, organized and carried out an exciting and rich sci- entific conference; THEREFORE BE IT RESOLVED that the Wilson Or- nithological Society and the Association of Field Ornithologists commend the Committee on Local Arrangements, the Scientific Program Committee, and all others who helped to make this meeting in Beltsville a great success and one that will be long remembered. BUSINESS MEETING President Charles Blem called the business meeting to order at 13:09 in the Ballroom of the Sheraton Ho- tel-College Park. He thanked Dick Banks and Jay Sheppard for hosting the meeting and then introduced the members of the Wilson Council. Secretary Sara Morris presented a summary of the Council meeting, which was held Thursday, 21 April. As of 15 April 2005, the Wilson membership stood at 1,848 including 172 students and 104 new members. We also have 555 institutional subscriptions to The Wilson Bulletin, 73 of which are new. As part of the Ornithological Societies of North America (OSNA) re- port, Council learned of several Wilson members who passed away during the last year, and Sara Morris asked those assembled to stand while she read the fol- lowing names: William W. Baum (Cleveland Heights, OH), Frank C. Bellrose, Jr. (Havana, IL), John H. Dick (Meggett, SC), Thomas H. Foster (Bennington, VT), Frederick Greeley (Amherst, MA), Peter Hall (St. George’s, Granada), William A. Jenner (Ofallon, IL), Ernst Mayr (Bedford, MA), Simon Rositzky (St. Jo- seph, MO), and Alexander Skutch (Costa Rica). After members were seated, Sara Morris announced that the Society received a generous bequest of $1,000 from the estate of Thomas Foster. During the last year, the management of the mem- bership and executive director duties for OSNA were transferred from Allen Marketing and Management to the Schneider Group. The database transfer occurred in November, which resulted in late renewal announce- ments. A third renewal notice was sent to members to ANNUAL REPORT 431 help catch any lapsed memberships. OSNA now has a new Web site, www.osnabirds.org, which is also the site of The Flock online. Council thanked the Investing Trustees for their ex- cellent work in managing the investments, and directed them to continue managing the Wilson portfolio for total return. Council approved the creation of three new awards. The William and Nancy Klamm Award will be given annually in recognition of significant contributions to the Society, beginning in 2006. Coun- cil also created the Nancy Klamm Award for the Best Undergraduate Oral Presentation and the Nancy Klamm Award for the Best Undergraduate Poster Pre- sentation. Council increased the number of Stewart Re- search Awards from four to six per year. Council agreed to loan the North American Ornithological Conference (NAOC) organizing committee $10,000 for seed money for the conference. The Council reelected Jim Sedgwick as editor of The Wilson Bulletin for volume 1 1 8, with sincere grat- itude for his work in getting The Wilson Bulletin back on its publication schedule. Now that the journal is back on schedule. Council voted for several changes to upgrade and modernize the Society’s journal. Coun- cil voted to change the name of the journal from The Wilson Bulletin to The Wilson Journal of Ornithology. Council also approved changes to the cover of the journal, both in color and artwork. The Publications Committee will determine the exact artwork to use and the journal cover. These changes will be implemented in 2006, beginning with the first issue of volume 1 18. Council heard updates on the preparations for the NAOC in Veracruz, Mexico next October. The Margaret Morse Nice Plenary lecture will open the NAOC next year. Martha Vaughan presented the Treasurer’s Report and Jim Sedgwick presented the Editor’s Report. Leann Blem introduced the students receiving travel awards and Sara Morris presented banquet tickets to the stu- dents who were presenting papers at the meeting. Jerry Jackson presented the report of the Nominat- ing Committee, which included Charles Blem, Danny J. Ingold, Bette Jackson, and Doris Watt. The com- mittee recommended the following slate of candidates: President, Doris J. Watt; First Vice-President, James D. Rising; Second Vice-President, E. Dale Kennedy; Secretary, Sara R. Morris; Treasurer, Melinda M. Clark; and Members of Council (2005-2008), Kath- leen G. Beal, Daniel Klem, Jr., and Douglas W. White. President Blem thanked the nominating committee and asked for any nominations from the floor. Hearing none, he accepted a motion to close nominations by Jay Sheppard, seconded by Ted Davis. John Kricher made the motion that the Secretary cast a single ballot for the slate of candidates, and Dick Banks seconded that motion. Secretary Morris cast the ballot, electing the officers and council members. Dick Banks announced that 242 people had regis- tered for the meeting. Ernesto Ruelas Inzunza and Juan E. Martinez-G6- mez gave a presentation that provided an overview of the plans for the fourth quadrennial North American Ornithological Conference in Veracruz City, Mexico, which is planned for 3-7 October 2006. The American Ornithologists’ Union, Association of Field Ornithol- ogists, Cooper Ornithological Society, CIPAMEX, Raptor Research Foundation, Society of Canadian Or- nithologists, Waterbird Society, and Wilson Ornitho- logical Society will participate in the conference. The major venues are expected to be the World Trade Cen- ter and the Hotel Galeria and the initial projections expect 1,200 participants. They ended by encouraging everyone to attend the NAOC because, “We know how to have a good party.’’ Jerry Jackson gave a brief presentation on the his- tory ot the Association of Field Ornithologists and the Wilson Ornithological Society. President Blem adjourned the meeting at 14:21 after a motion from John Kricher, which Jay Sheppard sec- onded. REPORT OF THE TREASURER OPERATING BUDGET FOR FISCAL YEAR 2005 Amended and Approved at Annual Meeting, 21 April 2005 Operating Revenue Actual Budget Budget 2004 2004 2005 Direct Public Support (C’ontributions) Memberships Subscriptions fkige C’harges Royalties BioOne Electronic I.icensing Sutton bund— 'fransfer for f ront ispieces Sale ot Back Issues & Books (Van Ivnc I.ibrary) I'otal Operating Revenue 99 1,200 0 38,552 46,000 46,000 9,025 17,000 10,000 7,974 12,000 8,000 1,086 1,600 1,000 6,63 1 6,632 10.055 0 0 4.000 465 1,000 0 63,832 85,432 79,055 432 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Operating Expenses Research Grants and Awards Student Travel Grants Van Tyne Library — Student Salaries/Benefits Printing and Mailing Costs-Bulletin (Allen Press) Editor’s Honorarium, Contract, Expenses OSNA Management Services OSNA Executive Director Storage Costs — Back Issues Membership Development Support — American Bird Conservancy Support — Ornithological Council Support — Ornithological Council Retreat Tax Preparation Fees Accounting Services Insurance Expenses General Expenses — Office, Postage, Copying, Bank Travel Expenses — Ornithological Council, OSNA, NABC, Annual Meetings Annual Meeting 2005 Advance for 2006 NAOC Meeting Nice Award Expenses President’s Discretionary Fund Van Tyne Library Expenses Award Costs 6,000 6,000 6,500 4,220 5,000 4,500 0 2,000 3,000 63,075 70,750 60,000 55,878 55,595 55,000 19,742 17,000 25,000 3,982 4,000 0 1,761 2,000 2,000 0 1 ,500 0 0 150 250 10,000 9,000 9,000 0 1,000 0 525 525 580 3,368 5,500 5,000 1,166 1,150 1,200 347 1,000 1,000 8,153 2,500 5,000 0 0 5,152 0 0 10,000 0 0 5,000 0 0 4,000 1,070 1,000 1,000 801 800 800 Total Operating Expenses Excess (Deficit) — Operating Total Investment Income (net of fees) Excess (Deficit) Including Investments Investment Bequest — Klamm Estate: Howland Capital Management Total Excess (Deficit) Including Klamm Bequest 180,088 186,470 203,982 (116,256) (101,038) (124,927) 229,208 65,340 126,718 112,952 (35,698) 1,791 192,000 0 0 304,952 (35,698) 1,791 STATEMENT OF ACTIVITIES FOR THE YEAR ENDING 3 1 DECEMBER 2004 Change in Unrestricted Fund Balances Revenues and Support Direct Public Support (Contributions) $ 192,099 Memberships 38,552 Subscriptions 9,025 Page Charges 7,974 Royalties 1,086 BioOne Electronic Licensing 6,631 Sale of Back Issues & Books (Van Tyne Library) Interest Income — Cash Accounts $ Total Revenues and Support 255,832 ANNUAL REPORT 433 Investment Income Realized Gains and Losses $ 26,318 Unrealized Gains and Losses (change in market value) 134,976 Investment Earnings 69,827 Total Investment Income 231,121 Total Revenues, Support, and Investment Income $ 486,953 Expenses and Losses Program Services Research Grants and Awards $ 6,000 Student Travel Grants 4,220 Award Costs 801 Van Tyne Library — Student Salaries/Benefits 0 Van Tyne Library Expenses 1,070 Printing and Mailing Costs — Bulletin (Allen Press) 61,075 Editorial Expenses 55,878 OSNA Management Services 19,742 OSNA Executive Director 3,982 Storage Costs — Back Issues 1,761 Support — Ornithological Council 10,000 Total Program Services $ 164,529 Supporting Services Investment Fees $ 14,346 Tax Preparation Fees 3,893 Insurance Expenses 1,166 General Expenses — Office, Postage, Copying, Bank Charges 347 Travel Expenses — Ornithological Council, OSNA, NABC, Annual Meetings 8,153 Total Support Services 27,905 Total Expenses and Losses $ 192,434 Total Change in Unrestricted Fund Balance 294,519 Unrestricted Fund Balance, Beginning 2,089,919 Unrestricted Fund Balance, Ending 2,384,438 Change in Restricted Fund Balance (Sutton Fund) Investment Income Unrealized Gains and Losses $ 9,288 Investment Earnings 3,196 Total Investment Income $ 12,484 F^xpenses and Losses Investment Fees $ 50 Transfer for Plate Fee 2.(K)0 Total F^xpenses and Losses % 2,050 Total Change in Restricted Fund Balance (Sutton Fund) $ 10,434 Restricted Fnind Balance, Beginning 129,510 Restricted Fund Balance, Ending . I 3 v,v44 Total F’lind Balances $ 2,524,382 434 THE WILSON BULLETIN • Vol. 1 17, No. 4, December 2005 STATEMENT OF FINANCIAL POSITION FOR THE YEAR ENDING 3 1 DECEMBER 2004 Assets Current Cash Assets Operating Cash Accounts $ 23,010 Cash Equivalents 24,530 Restricted Cash 2,060 Total $ 49,600 Investments Equities $ 2,036,027 Mutual Funds 26,648 Corporate Bonds 96,889 Fixed Income 315,218 Total $ 2,474,782 Total Assets $ 2,524,382 Fund Balances Unrestricted Fund Balances $ 2,384,438 Restricted Fund Balances 139,944 Total Fund Balances $ 2,524,382 EDITOR’S REPORT— 2004 The Wilson Bulletin Editorial Office received 135 manuscripts during 2004 (vs 130 in 2003, 140 in 2002). All papers received three peer reviews, except in those rare instances when a referee failed to com- plete and return a review (<5% of cases). Correspon- dence from authors and referees was handled promptly (within 3 days of receipt). I accepted 28% and rejected 18% of manuscripts received in 2004, with the re- mainder (54%) having been returned to authors for ex- tensive revision or revision and re-review. Volume 1 16 consisted of 39 major papers and 21 short communi- cations; each issue had a color frontispiece. The mean time from receipt to publication for manuscripts pub- lished in volume 116 was 379 days, comparable with that of Auk (473 days) and Condor (320 days). The dates of publication for the issues of volume 1 16 were 6 August, 12 October, 10 December (2004), and 18 February (2005). Except for the original submission of manuscripts, most of the correspondence and docu- ment transmittal between the Wilson Bulletin Editorial Office and authors, reviewers, and Allen Press is now electronic. I am grateful to Clait Braun, Richard Conner, Kath- leen Beal, and Karl Miller who served on the Editorial Board and reviewed numerous manuscripts. Kathy Beal offered statistical critiques of several manuscripts and compiled the index. Editorial assistants Beth Dil- lon and Cynthia Melcher performed essential editorial office operations, including maintenance of the e-mail Martha Vaughan, Treasurer (ending 23 April 2005) Melinda Clark, Treasurer (beginning 23 April 2005) correspondence tracking system and the author/referee/ manuscript database, corresponding with authors and reviewers, copyediting, and consulting with Allen Press, frontispiece artists, and other editors. I thank Allen Press, and especially Karen Ridgway, for guid- ance and helpful advice on the final stages of the ed- itorial and printing process. The USGS Fort Collins Science Center continues to be instrumental in its sup- port of the editorial office. We welcome suggestions on how to improve the timeliness and quality of The Wilson Bulletin. James A. Sedgwick, Editor The reports of the standing committees are as follows: REPORT OF THE JOSSELYN VAN TYNE MEMORIAL LIBRARY COMMITTEE I am very pleased to submit this report of the activ- ities at the Josselyn Van Tyne Memorial Library. The following happened over the past calendar year with respect to the library: Loans: Loans of library materials to members included 44 transactions to 26 members. These loans included 4 books and 255 photocopied articles. ANNUAL REPORT 435 Acquisitions: Exchanges: We received 136 publications by ex- change from 113 organizations or individuals. Gifts: We received 21 publications from 18 organi- zations. Subscriptions: We also received 25 publications from 21 subscriptions. We spent $768.30 on subscrip- tions in 2004. Donations: Members, friends, and libraries donated 660 items. These donations included 78 books, 1 CD, 426 journal issues, and 155 reprints and reports. Donors: The six members, friends, and libraries do- nating materials include E. H. Burtt, C. Kersting, M. Lowther, M. Sogge, A. E. Staebler, and B. Weaver. Purchases: New items purchased for $200 included 1 1 books and 4 CDs of bird songs. Dispersals: Gifts to other institutions: A total of 33 journal is- sues were donated to Manuel Marin, Chile, and 21 journal issues to the Bonn Museum, Germany. Back issues: We sent out 110 back issues of The Wilson Bulletin for only the cost of postage. Duplicates: We sold 13 duplicate books and 61 du- plicate journal issues for $607: $348 in cash, plus $259 in credit from Buteo Books. Events: Downsizing storage: We moved part of our storage area for back issues of The Wilson Bulletin last sum- mer. We anticipate moving the issues stored in the mu- seum this summer and will probably reduce the num- ber held. We are making a concerted effort to fill in gaps in our journal holdings in anticipation of the Google Dig- itization Project. Every catalogued item in the Univer- sity of Michigan Library will be scanned. All non- copyrighted items will be available to anyone online. Copyrighted items will be available to persons at the University, and through the WOS library, to WOS members. This will be a great project and should make ornithological literature available to re.searchers around the world. Accessibility on the Web: Web site: The Web site (http://www.ummz.lsa. umich.edu/bird.s/wos.html) continues to provide access to the library. Journals currently received are listed on the site as well as how to access the University of Michigan’s online catalogue, which interested people can use to check holdings. Books for sale: We have our duplicate books for sale listed on the Web site. Journals for trade: Also listed on the Web are the journals we have available for sale or trade. Thank Yous: Many thanks to our .secretary Janet Bell for keeping the library loan records and to our work-study student Erin Wiley for copying articles, keeping the library running, and mailing out back issues of Wilson Bul- letin. Janet Hmshaw. Librarian REPORT OF THE UNDERGRADUATE OUTREACH COMMITTEE This WOS Committee continues to maintain the Guide to Graduate Programs in Ornithology on the WOS Web site. I receive occasional e-mails from fac- ulty at listed institutions requesting updates to their entries. Prom time to time, I receive e-mails from users who indicate the guide is a valuable resource for stu- dents contemplating graduate study in ornithology. Herb Wilson, Chair The Committee on the Scientific Program, chaired by James D. Rising, presented the following program of paper and poster sessions. PAPER SESSIONS David A. Aborn, University of Tennessee at Chatta- nooga, Chattanooga, TN, “The use of urban riparian forests by migratory landbirds.’’ Paul J. Baicich, Swarovski Birding and National Wild- life Refuge Association, Oxon Hill, MD, “A rice- and-bird synthesis: is it our ‘next shade-grown cof- fee?’’’ Susan L. Balenger, L. Scott Johnson, and Emilene Os- tlind, Towson University, Towson, MD, “Does male UV-blue color indicate parental effort in Mountain Bluebirds?’’ Jonathan Bart, USGS Forest and Rangeland Ecosystem Science Center, Snake River Field Station, Boise, ID, “Sample size goals for monitoring North Amer- ican nongame birds.’’ Robert C. Reason, Ohio Field Station, USDA Wildlife Services, National Wildlife Research Center, San- dusky, OH, “Avian vision and collision avoidance.” Colleen E. Bell, Sara R. Morris, Canisius College, Buffalo, NY; and Arthur R. Clark, Buffalo Museum of Science, Buffalo, NY, “A crash course in com- munications tower mortality: birds dying to become a statistic in western New York.” Steven R. Beissinger, Mark I. Cook, University of Cal- ifornia, Berkeley, CA; Gary A. Toranzos, University of Puerto Rico, San Juan, PR; and Wayne J. Arendt, International Institute of Tropical Forestry, Luquillo PR, “Does incubation reduce microbial growth on eggshells and infection? . . . Why not!” Peter V. Bradley, Nevada Department of Wildlife, Elko, NV; and Kenneth W. Voget. Ruby Valley. NV. “Winter night roost selection by Black and Gray- crowned rosy-finches in Northeast Nevada.” Jeffery J. Buler, F rank R. Moore, and Robert H. Diehl. 'I'he University of .Southern Mississippi. Hatties- burg. MS. “Landscape-.scale habitat use by land- birds during migratory stopover near an ecological barrier as revealed by leather radar and groutul sur- veys.” Carolec Caflrey. Audubon Science. Ivylatul. I’A; Shau- na S. (’. Smith aiul liffany J. Weston. Oklahoma State University, Stillwater. OK; “West Nile Virus: 436 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 pernicious effects on an American Crow popula- tion.” Paul Callo, Mary Baldwin College, Staunton, VA, “Survivorship and territory fidelity of Red-eyed Vireos (Vireo olivaceus)." B. T. Collins, Environment Canada, Canadian Wildlife Service, Ottawa, ON, Canada, “Optimizing sam- pling effort on remote routes.” Richard N. Conner, Clifford E. Shackelford, Richard R. Schaefer, and Daniel Saenz, USDA Forest Ser- vice, Southern Research Station, Nacogdoches, TX, “Fire suppression and Bachman’s Sparrows in pine forests of eastern Texas.” Kristen M. Covino, Joanna M. Panasiewicz, Sara R. Morris, and H. David Sheets, Canisius College, Buf- falo, NY, “Getting to the point: rectrix shape mor- phometries in age discrimination of Ovenbirds.” C. M. Downes, Environment Canada, Canadian Wild- life Service, Ottawa, ON, Canada, “The BBS in Canada.” H. I. Ellis, University of San Diego, San Diego, CA; and J. R. Jehl, Jr., Smithsonian Institution, Washing- ton, DC, “Fat proportion of migrating and staging Eared Grebes does not differ.” William R. Evans, Old Bird, Inc., Ithaca, NY, “Broad- front migration + low cloud ceiling + hilly terrain = migration channeling.” Joelle L. Gehring, Central Michigan University, Mount Pleasant, MI; Paul Kerlinger, Curry & Kerlinger, LLC, Cape May Point, NJ; and Albert M. Manville, II, USFWS, Division of Migratory Bird Manage- ment, Arlington, VA, “Avian collisions with com- munication towers: a comparison of tower support systems and tower height categories.” Michael F. Gaydos and George L. Farnsworth, Xavier University, Cincinnati, OH, “Factors affecting pa- rental nest attendance in Northern Mockingbirds {Mimus polyglottos)." Kirk M. Goolsby, Northern Virginia Community Col- lege, Annandale, VA, “Uneven energy savings in Canada Geese during formation flight: do birds ex- ploit their position within the flock?” Russell Greenberg, Gregory Gough, and Daniel Boritt, Smithsonian Migratory Bird Center, National Zoo- logical Park, Washington, DC, “Neophobia in Mal- lards and other wild ducks.” George S. Hamaoui, Jr., and Edward H. Bum, Jr., Ohio Wesleyan University, Delaware, OH, “Analysis of feather-degradation by Bacillus licheniformis from the plumage of Botteri’s Sparrows living in wet and dry habitats in Arizona.” Kin-Lan Han, University of Maryland, College Park. MD; and Michael J. Braun, National Museum of Natural History, Smithsonian Institution, Suitland, MD, “Molecular phylogeny of Caprimulgidae (nightjars and nighthawks).” Gary H. Heinz and David J. Hoffman, USGS Patuxent Wildlife Research Center, Beltsville, MD, “The use of wild bird eggs to measure the sensitivity of avian embryos to methylmercury.” Christopher M. Hofmann, Thomas W. Cronin, Kevin E. Omland, University of Maryland-Baltimore County, Baltimore, MD; and Kevin J. McGraw, Ar- izona State University, Tempe, AZ, “Pigment co- deposition and the masking of carotenoids in Or- chard and Fuertes’s orioles.” Rebecca L. Holberton, Jason C. Johnston, University of Maine, Orono, ME; and Peter P. Marra, Smith- sonian Environmental Research Center, Edgewater, MD, “Habitats and hormones: understanding the physiological basis of life history stages in migra- tory birds.” C. Stuart Houston and Brenton Terry, Saskatoon, SK. Canada, “Turkey Vulture nestling travel, Saskatch- ewan to Costa Rica.” Austin L. Hughes and Helen Piontkivska, University of South Carolina, Columbia, SC, “DNA repeat ar- rays in chicken and human genomes and the adap- tive evolution of avian genome size.” Cathie A. Hutcheson, Makanda IL; Leonard I. Was- senaar. National Water Research Institute, Environ- ment Canada, Saskatoon, SK. Canada; and Lewellyn Hendrix, Southern Illinois University, Carbondale, IL, “Preliminary examination of the use of hydro- gen isotope ratios in estimating the natal latitudes of hatch year Ruby-throated Hummingbirds.” Jerome A. Jackson, Florida Gulf Coast University, Ft. Myers, EL, “Art in science: the contributions of George Miksch Sutton.” Helen James, National Museum of Natural History, Smithsonian Institution, Washington, DC, “The bio- geography and paleoecology of Koa-finches, extinct legume-eaters of the Hawaiian Islands.” L. Scott Johnson, Emilene Ostlind, and Susan L. Bal- enger, Towson University, Towson, MD, “Male pa- rental effort at low and high elevations in a Wyo- ming population of Mountain Bluebirds.” Todd Katzner. Department of Conservation and Field Research, National Aviary, Allegheny Commons West. Pittsburgh, PA; E. J. Milner-Gulland, Imperial College London, Ascot, Berkshire, United King- dom; and Evgeny A. Bragin, Naurzum National Na- ture Reserve, Kustanay Oblast, Naurzumski Raijon, Dokuchaevka, Kazakhstan; “Using modeling to im- prove monitoring of birds: are we collecting the right data?” Paul Kerlinger, Curry & Kerlinger LLC, Cape May Point, NJ, “Appalachian ridge following by night migrating birds? A test of the hypothesis using ma- rine surveillance radar in three states.” Daniel Klem, Jr., Muhlenberg College, Allentown, PA, “A humorous look at a deadly conservation issue: birds and glass.” Beatrice Kondo and Kevin E. Omland. University of Maryland-Baltimore County, Baltimore, MD, “Us- ing New World orioles to address an old question: evolution of migration.” Lionel Leston and Amanda D. Rodewald. The Ohio State University, Columbus, OH, “Are urban forests ecological traps for birds?” James E. Lyons and Jaime A. Collazo, USGS Patuxent Wildlife Research Center and North Carolina Co- ANNUAL REPORT 437 operative Research Unit, North Carolina State Uni- versity, Raleigh, NC, “Plasma lipid metabolites and refueling performance at four stopovers along the migratory route of Semipalmated Sandpipers.” Juan E. Martmez-Gomez, University of Missouri Saint Louis, Columbia, MO, and Island Endemics Foun- dation, Mexico, “Island conservation of Mexican insular avifaunas.” Steven M. Matsuoka, Jim A. Johnson, U.S. Fish and Wildlife Service, Migratory Bird Management, An- chorage, AK; Daniel R. Ruthrauff, Teresa L. Tib- bitts, and Robert E. Gill, Jr., U.S. Geological Sur- vey, Alaska Science Center, Anchorage, AK, “Es- timating the global abundance of McKay’s Buntings on St. Matthew Island, Alaska.” Jennifer McNicoll, Martha Desmond, and Leigh Mur- ray, New Mexico State University, Las Cruces, NM, “Burrowing Owl nest site selection on the Janos- Nuevo Casas Grandes, Mexico prairie dog com- plex.” Alex Mills, University of Toronto, Toronto, ON, Can- ada, “Limits of ecomorphological analysis in ex- plaining habitat specificity.” Douglas Mock and P. L. Schwagmeyer, University of Oklahoma, Norman, OK, “Nestling begging and the problem of signal reliability.” Jennifer L. Newbrey and Wendy L. Reed, North Da- kota State University, Fargo, ND, “Effects of nest contents and minimum daily temperature on female Yellow-headed Blackbird nest attentiveness.” Timothy O’Connell and Martin Piorkowski, Oklahoma State University, Stillwater, OK, “Do wind turbines influence the density of breeding songbirds?” Karan J. Odom, Ohio Wesleyan University, Delaware, OH, “Differences between vocalizations of wild- reared and human-reared birds of prey as an indi- cation of learning within call development of owls and eagles.” Kevin E. Omland, University of Maryland-Baltimore County, Baltimore, MD, “Elaborate female colora- tion in tropical orioles (Icterus): phylogenetic and behavioral studies.” Brent Ortego, Texas Parks and Wildlife Department, Victoria, TX, “Practical BBS sampling consider- ations when using volunteers.” Harry W. Power, Rutgers University, New Brunswick, NJ; and Michael P. Lombardo, Grand Valley State University, Allendale, Ml, “A graphical analysis of the costs of female copulatory activity in birds.” John H. Rappole, Smithsonian Conservation and Re- search Center, Front Royal, VA, “Gene Morton’s contributions to migratory bird ecology.” Matthew W. Reudink and Robert L. Curry, Villanova University, Villanova, PA, “Extra-pair paternity and mate choice in a chickadee hybrid zone.” Ferrell D. Rich, U.S. Fish and Wildlife .Service and Partners in Flight, Boise, ID, “Recommendations lor rangewide population trend monitoring of North American landbirds.” Chandler S. Robbins, USGS Patuxent Wildlife Re- search Center, Laurel, MD, “Reflections on 40 years of Breeding Bird Survey.” J. A. Royle and J. R. Sauer, USGS Patuxent Wildlife Research Center, Laurel, MD, “Spatial coverage and inference: trade-offs between survey design and model assumptions in the North American Breeding Bird Survey.” Ernesto Ruelas Inzunza, University of Missouri, Co- lumbia, MO; Stephen W. Hoffman, Predator Con- servation Alliance, Bozeman, MT; and Laurie J. Goodrich, Hawk Mountain Sanctuary Association, Kempton, PA, “Behavior of thermal soaring mi- grants in Veracruz, Mexico.” John B. Sabine, Sara H. Schweitzer, University of Georgia, Athens, GA; and J. Michael Meyers, USGS Patuxent Wildlife Research Center, Univer- sity of Georgia, Athens, GA, “Nest fate and pro- ductivity of beach nesting American Oystercatchers, Cumberland Island National Seashore, Georgia.” John R. Sauer, William A. Link, James D. Nichols, and J. Andrew Royle, USGS Patuxent Wildlife Research Center, Laurel, MD, “The North American Breeding Bird Survey: credible, or not?” Richard R. Schaefer, D. Craig Rudolph, and Richard N. Conner, USDA Forest Service, Southern Re- search Station, Nacogdoches, TX, “Preliminary re- sults from ongoing studies of nesting habitat, nest- ling provisioning, and foraging of the southeastern American Kestrel in the west Gulf Coastal Plain.” Ralph W. Schreiber, Elizabeth A. Schreiber, National Museum of Natural History, Smithsonian Institu- tion, Washington, DC; Ashley M. Peele, and Ed- ward H. Burtt, Jr., Ohio Wesleyan University, Del- aware, OH; “Feather damage in an albino Greater Frigatebird.” Jay M. Sheppard, Laurel, MD; Kenneth P. Able, McArthur, CA; and Robin McCleery, Edward Grey Institute for Field Ornithology, South Parks Rd., Ox- ford, UK, “O.W.L. update.” John A. Smallwood, Valerie Dudajek, Montclair State University, Montclair, NJ; Sivajini Gilchrist, New- ark Museum, Newark, NJ; and Mary Anne Small- wood, Ironia School, Randolph, NJ, “Vocal devel- opment in American Kestrel (Falco sparverius) chicks: acoustical characteristics and ontogenetic patterns.” Jo.seph Smith, Peter P. Marra, Smithsonian Environ- mental Research Center, Edge water, MD; and Leo- nard R. Reitsma, Plymouth State University, Plym- outh, NH, “Roosting behavior of the Northern Wa- terthrush during the non-breeding sea.son.” Jennifer L. .Smolinski and George L. Farnsworth, Xa- vier University, Cincinnati, OH, “Nutnerical com- petence in wild Northern Mockingbirds {Minins po- l\\i> lottos)." Paul R. Spit/er, C'ooperative Oxford Lab, Oxford, MD, “Ospreys a la Faaborg.” Rachel Sturge, University of Tt)ionto, Toronto, ON, Canada; and Robeil Rockwell, American Mu.seum of Natural History, New York City, NY. “The ef- fects of habitat loss on the .Savannah Sparrows {Pas- 438 THE WILSON BULLETIN • Voi ! 17, No. 4, December 2005 serculus sandwichensis) of La Perouse Bay, Mani- toba.” Rebecca Suomala, Kimberly Babbitt, University of New Hampshire, Durham, NH; and Sara Morris, Canisius College, Buffalo, NY, “Comparison of spe- cies distribution and habitat use during stopover on two islands in the Gulf of Maine.” Ethan J. Temeles, Robin S. Goldman, and Alexei U. Kudla, Amherst College, Amherst, MA, “Eoraging and territorial economics of sexually-dimorphic Pur- ple-throated Caribs, Eulampis jugularis, at three hel- iconias.” Monica Tomosy, USGS Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, “North American bird banding program review.” Jennifer M. Urbanski, Jerry Dudziak, Sara R. Morris, and H. David Sheets, Canisius College, Buffalo, NY, “Is shorter better? Does truncation increase the util- ity of open population models in stopover estima- tion?” Kate E. Williamson, University of Northern Colorado, Greeley, CO; and Edward H. Burtt, Jr., Ohio Wes- leyan University, Delaware, OH, “The microbial ecology in the plumage of Neotropical migrants.” Michael D. Wilson and Bryan D. Watts, College of William and Mary, Williamsburg, VA, “The influ- ence of landscape configuration on the distribution and abundance of the Whip-poor-will {Caprimulgus vociferus)." Michael D. Wilson and Bryan D. Watts, College of William and Mary, Williamsburg, VA, “The influ- ence of lunar conditions on the detection rate of the Whip-poor-will {Caprimulgus vociferus): implica- tions for large-scale monitoring programs.” Petra Bohall Wood, USGS West Virginia Cooperative Pish and Wildlife Research Unit, Division of For- estry, West Virginia University, Morgantown, WV, “Cerulean Warblers and canopy heterogeneity in West Virginia.” Bonnie E. Woolfenden, Bridget J. M. Stutchbury, York University, Toronto, ON, Canada; and Eugene S. Morton, National Zoological Park, Smithsonian In- stitution, Washington, DC, “Social isolation leads to a reduction in EP mating; is this a hidden cost of forest fragmentation?” Timothy F. Wright and Christine R. Dahlin, New Mex- ico State University, Las Cruces, NM, “The signal design of pair duets; does structure relate to func- tion?” Tamaki Yuri, Michael J. Braun, National Museum of Natural History, Smithsonian Institution, Suitland, MD; Robert W. Jernigan, American University, Washington, DC; Robb T. Brumfield, Museum of Natural Science, Louisiana State University, Baton Rouge, LA; and Nirmal K. Bhagabati, The Institute for Genomic Research, Rockville, MD, “Different genetic markers reveal different levels of introgres- sion in a Manacus hybrid zone.” POSTERS Jennifer Baldy, Esra Ozdenerol, Lensyl Urbano, Hsi- ang-te Kung, University of Memphis, Memphis, TN; and Paul Hamel, USDA Forest Service, Center for Bottomland Hardwood Research, Stoneville, MS, “Breeding climate preferences of the Cerulean Warbler determined by spatial filtering of Breeding Bird Survey data.” Jacqueline Bennett and Gary Ritchison, Eastern Ken- tucky University, Richmond, KY, “Nest defense be- havior of male and female Eastern Bluebirds.” Andrew J. Bernick, City University of New York- Graduate Center/College of Staten Island, Staten Is- land, NY, “Gull harassment and predation on adult Black-crowned Night-Herons in the New York City area.” M. J. Braun, C. J. Huddleston, K. L. Han, T. Yuri, J. Hunt, M. Krosby, Smithsonian Institution, National Museum of Natural History, Washington, DC; S. J. Hacked, J. Harshman, R. Bowie, S. Reddy, M. Burns, E. Sacked, R. Flynn, Field Museum of Nat- ural History, Chicago, IL; E. Braun, R. Kimball, D. Steadman, J. Chojnowski, University of Florida, Gainesville, EL; W. Moore and K. Miglia, Wayne State University, Detroit, MI; F. Sheldon, B. Marks, C. Witt, Louisiana State University, Baton Rouge, LA; L. Christidis, J. Norman, Victoria Museum, Melbourne, Victoria, Australia; R. Page, University of Glasgow, Glascow, Scotland, United Kingdom; R. T. Chesser, CSIRO, Victoria, Australia; and D. Swofford, Florida State University. Tallahassee, EL “Early bird; a collaborative project to resolve the deep nodes of avian phylogeny.” W. P. Brown, P. Eggermont, V. LaRiccia, and R. R. Roth, University of Delaware, Newark, DE, “Can Wood Thrush growth be modeled using a non-para- metric spline estimator?” Emily A. Caruana, Sarah M. Musilli, Michael S. Hur- ban, Canisius College, Buffalo, NY; Scott Weiden- saul, Ned Smith Center for Nature and Art, Millers- burg, PA; H. David Sheets, and Sara R. Morris, Can- isius College, Buffalo, NY; “Age-related differences in the fall migration of Northern Saw- whet Owls.” Kimberley Corwin, NYS Department of Environmen- tal Conservation, Albany NY; and Kevin J. Mc- Gowan, Cornell Laboratory of Ornithology, Ithaca, NY, “New York’s second Breeding Bird Atlas.” Thomas Dietsch, Russell Greenberg, Peter Bichier, Smithsonian Migratory Bird Center, National Zoo- logical Park, Washington, DC; Ivette Perfecto, Uni- versity of Michigan, Ann Arbor, MI; and Suzanne Langridge, University of California, Santa Cruz, CA, “Foraging ecology of migratory and resident birds in coffee agroecosystems of Chiapas, Mexi- co.” Matthew S. Dietz, University of Michigan, Ann Arbor, MI, “The effects of human and environmental stressors on White-crowned Sparrow corticosterone levels and reproductive success.” Walter G. Ellison, Maryland Ornithological Society, Chestertown, MD; and Mark Wimer, USGS Patux- ent Wildlife Research Center, Laurel, MD, “Possible distributional changes detected by a second Breed- ANNUAL REPORT 439 ing Bird Atlas in Maryland and the District of Co- lumbia.” Kayde Gilbert, Janet Gorrell, and Gary Ritchison, Eastern Kentucky University, Richmond, KY, “Ef- fects of West Nile Virus infection on the nest de- fense behavior of Eastern Bluebirds (Sialia sialis)." Beth A. Hahn, University of Michigan, Ann Arbor, MI, “Using song playbacks to influence breeding habitat selection by American Redstarts.” Marcy Heacker, Smithsonian Institution, National Mu- seum of Natural History, Washington, DC; and Joe Witt, U.S. Eish and Wildlife Service, Potomac River National Wildlife Refuge Complex, Woodbridge, VA, “Osprey activity on the Potomac River.” Christopher M. Heckscher, University of Delaware, Newark, DE, “The Veery call repertoire: calls used in short- and long-distance communication in a mi- gratory oscine passerine.” Elizabeth Humphries, Jeffrey L. Peters, Kevin E. Om- land. University of Maryland-Baltimore County, Baltimore, MD; Jon E. Jonsson, and Alan D. Afton, USGS Louisiana Wildlife and Fisheries Cooperative Research Unit and School for Renewable Resources, Louisiana State University, Baton Rouge, LA; “Phylogenetics and phylogeography of the white goose complex, genus Chen: is Mother Goose spin- ning a new tale?” Michael S. Hurban, Emily A. Caruana, Sarah M. Mu- silli, Canisius College, Buffalo, NY; Scott Weiden- saul, Ned Smith Center for Nature and Art, Millers- burg, PA; H. David Sheets, and Sara R. Morris, Can- isius College, Buffalo, NY; “Stopover rates and du- rations of migrant Northern Saw-whet Owls in southern Pennsylvania.” L. Scott Johnson, Brian S. Masters, Larry E. Wimmers, Bonnie G. Johnson, Robyn Milkie, Rachel Molina- ro, and Brendan Gallagher, Towson University, Towson, MD, “Sex manipulation within broods of House Wrens? A repeat study.” Andrea Kraljevic, University of Michigan, Ann Arbor, MI, “The effects of ski slope fragmentation on avian diversity and behavior.” Patrick J. Kramer and James R. Hill, III, Purple Martin Con.servation Association, Edinboro University of Pennsylvania, Edinboro, PA, “Locating and pro- tecting Purple Martin roosts.” Sara A. Kuebbing, R. R. Roth, and J. L. Bowman, University of Delaware, Newark, DE, “Po.ssible .sexual dimorphism in breast spotting in the Wood Thrush and its potential for .sexing.” Brook Lauro, St. John's University, Jamaica, NY. “Habitat enhancement to improve waterbird pro- ductivity: what is the best method?" Ja.son Law and Emily Silverman, University of Mich- igan, Ann Arbor, Ml, “Evaluating home range es- timators for pas.serines." Spring Ligi and Kevin Omland, University of Mary- land-Baltimore County, Baltimore, MD, “Possible double brooding in temperate-breeditig orioles: breeding behavior of Baltimore Orioles in Mary- land." Stephanie E. Little, Katherine E. Eggleston, Kristin Hnilicka, Bernard Lohr, and Douglas E. Gill, Uni- versity of Maryland, College Park, MD, “Trill rate as a performance measure in Grasshopper Sparrow song.” Anne C. Logie, University of Maryland-Baltimore County, Baltimore, MD; Isabelle A. Bisson, Peter P. Marra, Smithsonian Environmental Research Center, Edgewater, MD; Patrick M. Gillevet, George Mason University, Manassas, VA; and Edward H. Burtt, Jr., Ohio Wesleyan University, Delaware, OH, “A pre- liminary analysis of feather microbial communities on New World passerines.” Dana E. Long, R. R. Roth, and W. P. Brown, Univer- sity of Delaware, Newark, DE, “Characteristics of repeat-pairs of Wood Thrushes: size, age, nesting characteristics and success.” Sarah Mabey, North Carolina State University, Ra- leigh, NC; Bryan Watts, Bart Paxton, Fletcher Smith, College of William and Mary, Williamsburg, VA; Barry Truitt, The Nature Conservancy, Virginia Coast Reserve Program, Nassawadox, VA; and Deanna Dawson, USGS Patuxent Wildlife Research Center, Laurel, MD, “Identifying stopover sites for migrating passerine birds in the lower Chesapeake Bay region.” Kathryn E. Mattern, Canisius College, Buffalo, NY; Rebecca W. Suomala, University of New Hamp- shire, Durham, NH; Melissa S. Mustillo, Peggy E. Buckley, Sara R. Morris, and H. David Sheets, Can- isius College, Buffalo, NY; “Location, location, lo- cation: comparison of stopover at two sites.” Sarah M. Musilli, Michael S. Hurban, Emily A. Car- uana, Canisius College, Buffalo, NY; Scott Weiden- saul, Ned Smith Center for Nature and Art, Millers- burg, PA; H. David Sheets, and Sara R. Morris, Can- isius College, Buffalo, NY; “Sex-related differences in the migration of Northern Saw-whet Owls." Melissa S. Mustillo, Elizabeth H. Lewis, Kathryn E. Mattern, Sara R. Morris, and H. David Sheets, Can- isius College, Buffalo, NY, “Timing is everything: sea.sonal comparison of migratory stopover." Emilene Ostlind, L. Scott John.son, and Susan L. Bal- enger, Towson University, Tow.son, MD, “Egg and clutch size variation along an elevational gradient in Mountain Bluebirds.” Myra Shulman, Julie Ellis, Holly Je.s.sop, Virginia Seng, and Katie Mach, Cornell University, Ithaca, NY, “Catastrophic effects from raccoon presence in gull breeding colonies." Jeffrey A. Spcndelow, USGS Patuxent Wildlife Re- search Center (PWRC), Laurel. MD; David A. Shealer, Loras College, Dubucjue, I A; J. S. Hatfield. J. D. Nichols, PWRC; and I. C. T. Nisbet, I. C'. T. Nisbet & C'o., North F•almouth. MA. ".Sex-specific survival rates of adult Roseate Terns: are males pay- ing a higher reproductive cost than females?" Ian T:. Tracy, C'hris Hofmann, and Kevin I:. Omland. University of Maryland Baltimore C'ounty. Balti- more. MD, “Defining species limits through color; analysis of the Orchard Oriole complex," 440 THE WILSON BULLETIN • VoL 117, No. 4, December 2005 Ursula Valdez, University of Washington, Seattle, WA, “Using aural surveys and radio-telemetry to deter- mine the abundance and habitat use of forest-falcons in lowland Amazonian rainforest of southeast Peru.” Lisa Vormwald, Roland Roth, Isis Johnson, and J. L. Bowman, University of Delaware, Newark, DE, “Inter-year distance between nest sites of Wood Thrush with respect to age, sex, previous year’s suc- cess and mate’s age.” Doris J. Watt, Danelle Duffy, Leslie Kleczek, and Shannon Meyer, Saint Mary’s College, Notre Dame, IN, “Comparisons of stress in House Finches using heterophil to lymphocyte ratios.” Douglas W. White and E. Dale Kennedy, Biology De- partment, Albion College, Albion, MI, “Relation of season, clutch size, and egg order to hatching failure in House Wrens.” Mark Wimer, Bruce Peterjohn, Anna Ott, and Naoko Griffin, USGS Patuxent Wildlife Research Center, Laurel, MD, “North American Breeding Bird Atlas viewer.” Beth A. Wisotzkey and Roland Roth, University of Delaware, Newark, DE, “Survival of Brown-headed Cowbird and Wood Thrush eggs and young in Wood Thrush nests.” Lindsay Zemba and Robert Curry, Villanova Univer- sity, Villanova, PA, “Male dominance rank in an expanding hybrid zone between Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (P. carolinensis) in southeastern Penn- sylvania.” ATTENDANCE Alaska: Anchorage, Steve Matsuoka. Arizona: Phoenix, Troy Corman; Tucson, Clait E. Braun. Arkansas: Fayetteville, Douglas James. California: Berkeley, Steve Beissinger; San Diego, Hugh Ellis. Colorado: Fort Collins, Lori Nielsen, James A. Sedg- wick; Greeley, Kate Williamson. Delaware: Newark, Bill Brown, Dana Long, Roland Roth, Lisa Vormwald, Beth Wisotzkey; Smyrna, Christopher Heckscher; Wilmington, Jean Woods. Florida: Fort Myers, Jerome A. Jackson. Georgia: Athens, John Sabine; Macon, Todd Schnei- der; Savannah, Steven J. Wagner. Idaho: Boise, Jon Bart, Terry Rich, Rex Sallabanks. Illinois: Makanta, Cathie Hutcheson; Springfield, Ve- ron Kleen. Indiana: Indianapolis, Alicia E Craig; Notre Dame, Doris Watt; South Bend, Melinda Clark. Iowa: Ames, Bonnie Bowen. Kentucky: Berea, Jacqueline Bennett; Frankfort, Brainard Palmer-Ball, Jr.; Richmond, Kayde Gilbert, Gary Ritchison. Maine: Orono, Rebecca Holberton. Maryland: Annapolis, Joseph R. Jehl, Jr.; Arbutus, Stephanie Little; Baltimore, Chris Hofmann, Eliza- beth Humphries, Beatrice Kondo, Spring Ligi, Anne Logie, Kevin Omland, Bryan Rosensteel, Ian Tracy; Beltsville, Evelyn Adkins; Chestertown, Walter G. Ellison; Chevy Chase, Ellen Paul; Clarksburg, Jerry Persall; College Park, Bernard Lohr; Edgewater, Pete Marra, Joseph Smith; Fort Washington, Paul J. Baicich; Greenbelt, James A. Smith; Largo, Janet McMillen; Laurel, Deanna Dawson, Naoko Griffin, Mary Gustafson, Judd A. Howell, Marshall Howe, Kathy Klimkiewicz, James Lyons, Keith Pardieck, Bruce G. Peterjohn, Eleanor C. Robbins, Andy Roy- le. Jay Sheppard, Jeff Spendelow, Monica Tomosy, Mark Wimer, David Ziolkowski; Silver Spring, Greg Butcher, Adele Conover, Rob Hilton, Lisa Shannon; Suitland, Kirsten Braun, Michael Braun, Kin-Lan Han, Chris Huddleston, Tamaki Yuri; Takoma Park, Peter Blank; Towson, Susan L. Balenger, L. Scott Johnson; Trappe, Paul Spitzer. Massachusetts: Amherst, Donald Kroodsma, Ethan J. Temeles; Brookline, Holly Jessop; Chilmark, Allan R. Keith; East Falmouth, William E. Davis, Jr.; Hadley, Randy Dettmers; Marblehead, Ann Bou- chard; Marshfield, Andrea Jones; Mattapoisett, Elise Mock, George Mock; Natick, Elissa Landre; Pocas- set, John Kricher, Martha Vaughan. Michigan: Albion, Dale Kennedy, Doug White; Ann Arbor, Matthew Dietz, Beth Hahn, Andrea Kraljev- ic, Jason Law; Chelsea, Janet Hinshaw; Farwell, Joelle Gehring; Kalamazoo, Ray Adams. Minnesota: Fort Snelling, Tom Will. Mississippi: Hattiesburg, Jeffrey Buler; Stoneville, Paul B. Hamel. Missouri: Columbia, Ernesto Ruelas Inzunza; St. Lou- is, Juan E. Martinez Gomez. Nebraska: Hastings, Diane Beachly. Nevada: Elko, Pete Bradley; Las Vegas, Cris Tomlin- son. New Hampshire: Center Harbor, John P. Merrill; Con- cord, Pamela Hunt; Epsom, Rebecca Suomala. New Jersey: Cape May Point, Paul Kerlinger; North Plainfield, Harry Power; Randolph, John A. Small- wood, Mary Anne Smallwood, Nathan Smallwood; Somerset, Bertram G. Murray, Jr. New Mexico: Albuquerque, John Series; Las Cruces, Jennifer McNicoll, Timothy F. Wright. New York: Albany, Kimberley Corwin; Buffalo, Col- leen E. Bell, Peggy Buckley, Emily Caruana, Arthur R. Clark, Kristen Covino, Jerry A. Dudziak, Mi- chael Hurban, Elizabeth Lewis, Katie Mattern, Sa- rah Musilli, Melissa Mustillo, Joanna Panasiewicz, H. David Sheets, Jennifer M. Urbanski; Grand Is- land, Elizabeth Morris, Sara Morris; Ithaca, William Evans; Staten Island, Andrew Bernick; Utica, Judy McIntyre, Pat McIntyre. North Carolina: Raleigh, Becky Browning. North Dakota: Fargo, Jennifer Newbrey, Michael Newbrey; Sawyer, Ron Martin. Ohio: Cincinnati, George Farnsworth, Michael Gay- dos, Jennifer Smolinski, Sandra L. L. Gaunt, Lionel Leston; Delaware, Edward H. Burtt, Jr., George S. Hamaoui, Jr., Chuck Jagger, Sarah A. Manor, Karan ANNUAL REPORT 441 Odom, Ashley Peele, Vinod Saranathan; Sandusky, Bob Reason. Oklahoma: Norman, Douglas W. Mock; Stillwater, Tim O’Connell; Tulsa, Charles R. Brown, Mary Bomberger Brown. Pennsylvania: Allentown, Daniel Klem, Jr.; Cam- bridge Springs, Eugene S. Morton; Conneautville, Joan Galli; Edinboro, James R. Hill, III, Patrick Kramer, John Tautin; Ivyland, Carolee Caffrey; Montgomery, Dana Brauning; New Freedom, Bruce G. Fortman; Orangeville, Douglas A. Gross; Or- wigsburg, Rebekah Augustine, Keith L. Bildstein, Andres de la Cruz Munoz, Yelena Danilova, Gail Hall, Yedi Juarez Lopez, Sergio Seipke; Palmyra, Lindsay Zemba; Philadelphia, Wendy Lenhart; Pittsburg, Todd Katzner; Scranton, Michael Carey; Villanova, Bob Curry. Rhode Island: Narragansett, Suzanne Lussier. South Carolina: Columbia, Austin Hughes. Tennessee: Chattanooga, David Aborn. Texas: Lake Jackson, Cecilia M. Riley; Nacogdoches, Richard N. Conner, Richard B. Schaefer; Victoria, Brent Ortego. Washington, DC: Claudia Angle, Tom Bancroft, Rog- er Clapp, Thomas Dietsch, Robert Fleischer, Mer- cedes S. Foster, Russell Greenberg, Helen James, Chris Milensky. Vermont: Northfield, William Barnard. Virginia: Alexandria, Richard C. Banks, Betty Anne Schreiber; Annandale, Walter Bulmer; Fairfax, Mar- cy Heacker; Front Royal, John Rappole; Lynchburg, Gene Sattler; Portsmouth, Elisa Enders; Richmond, Charles R. Blem, Leann Blem, Sergio Harding, Mike Wilson; Shipman, Allen Hale; Staunton, Paul A. Callo; Warrenton, Kirk M. Goolsby. Washington: Bainbridge Island, Lee Robinson; Seat- tle, Ursula Valdez. West Virginia: Bethany, Albert R. Buckelew, Susan Buckelew; Millstone, Thomas R. Fox; Montgomery, Deborah Beutler; Morgantown, Petra Wood. Canada Alberta: Edmonton, Brenda Dale. British Columbia: Naramata, Dick Cannings. New Brunswick: Sackville, Dan Busby. Ontario: Mississauga, Rachel Sturge; Newmarket, Kimberly Jones; Ottawa, Brian Collins, Constance Downes, Erica Dunn, Charles M. Francis, Bev McBride; Toronto, loana Chiver, Melissa Evans, Alex Mills, Levi Moore, James Rising, Bridget Stutchbury, Bonnie Woolfenden. Quebec: Sainte-Foy, Gilles Falardeau. Saskatchewan: Saskatoon, Mary Houston, Stuart Houston, Alan R. Smith. Wilson Bulletin 1 1 7(4);442-443, 2005 REVIEWERS FOR VOLUME 117 Referees play a critical role in the editorial process. Thoughtful, incisive reviews are paramount in the main- tenance of high scientific standards and journal quality. The following individuals graciously served as referees for this volume of The Wilson Bulletin (referees who contributed two or more reviews appear in boldface). The Wilson Ornithological Society and the editorial staff of The Wilson Bulletin are deeply grateful to them for their assessments and recommendations. — James A. Sedgwick, Editor. E. S. Adams, M. Akesson, A. Aleixo, R. T. Alisauskus, J. C. Alonso, A. L. Altshuler, J. A. Amat, S. H. Anderson, R. D. Applegate, G. W. Archibald, T. Arnold, R. A. Askins, E. C. Atkinson, M. Ausden, A. V. Badyaev, V. Baglione, E Bairlein, A. J. Baker, K. K. Bak- ker, R. R Baida, J. D. Ballou, W. H. Baltosser, G. T. Bancroft, R. C. Banks, G. Barrantes, J. M. Bates, E. M. Bayne, K. G. Beal, C. Beck- mann, J. C. Bednarz, M. D. Beebee, M. D. Beecher, R. E. Bennetts, L. K. Benoit, S. Bensch, A. M. Benson, G. E. Bentley, L. B. Best, K. L. Bildstein, T. R. Birkhead, J. G. Blake, J. Blondel, C. W. Boal, C. E. Bock, T. R. Bogenschutz, A. B. Bond, M. Bradley, C. E. Braun, M. J. Braun, J. D. Brawn, R. M. Brigham, R. R Brooks, L. Brotons, A. Brown, D. Brown, L. Bruinzeel, R. T. Brumfield, A. H. Brush, T. Brush, J. B. Buchanan, R. A. Buckley, J. Burger, L. W. Burger, D. E. Bur- hans, D. Busby, B. E. Byers, B. S. Cade, T. J. Cade, C. D. Cadena, C. L. Caffrey, J. Cal- kins, D. E. Capen, M. Cardillo, J. M. Cardoso da Silva, R Cassey, J. E. Cely, G. Chilton, M. Cichon, R. B. Clapp, R. R. Clay, T. H. Clutton- Brock, A. Cockburn, J. A. Collazo, J. M. Col- uccy, M. Colwell, S. Conant, J. W. Connelly, R. N. Conner, K. E Conrad, C. Conway, E Cooke, J. M. Cooper, R. T. Corlett, M. C. Coulter, R. J. Craig, W. Cresswell, D. A. Cristol, A. Cruz, J. J. Cuervo, R. L. Curry, T. W. Custer, R. Darby, N. B. Davies, C. A. Da- vis, S. E. Davis, W. E. Davis, D. K. Dawson, R. Dawson, C. de la Cruz, A. M. De Marinis, D. C. Dearborn, R. S. DeLotelle, J. Deppe, C. Derrickson, M. J. Desmond, A. Desrochers, E Dessi-Fulgheri, R Deviche, R. Diehl, J. J. Dinsmore, S. J. Dinsmore, T. M. Donovan, L. dos Anos, V. J. Dreitz, E Dubois, B. D. Dug- ger, R. Dukas, J. R. Dunk, E. H. Dunn, J. B. Dunning, Jr., J. R. Eberhard, K. Eckerle, K. S. Ellison, T. R. Engstrom, E. C. Enkerlin- Hoeflich, R. M. Erwin, J. Esely, M. A. Et- terson, M. R. Evans, W. R. Evans, J. Faa- borg, J. B. Falls, G. L. Farnsworth, C. C. Farquhar, R. Fayt, S. Forbes, J. C. Franson, T. Fransson, K. E. Franzreb, R C. Frederick, G. A. Gale, B. G. Galef, S. A. Gauthreaux, E R. Gehlbach, C. K. Ghalambor, D. D. Gibson, R. M. Gibson, K. M. Giesen, S. A. Gill, W. M. Giuliano, M. Gochfeld, H. G. Gomez de Sil- va, J. A. Gonzales, C. E. Gordon, A. Goth, C. H. Graham, C. Gratto-Trevor, G. R. Graves, M. Green, C. H. Greenberg, T. Grim, T. C. Grubb, R. C. Gruys, J. A. Grzybowski, C. G. Guglielmo, M. Guillemette, F. S. Guthery, C. A. Haas, J. C. Hagar, J. C. Hagelin, T. M. Haggerty, T. R Hahn, S. Hall, P. B. Hamel, C. M. Handel, A. R. Harmata, B. A. Har- rington, D. Hasselquist, M. Hau, M. E. Haub- er, E E. Hayes, S. E. Hayslette, E. A. Hebets, D. Heg, B. Heinrich, B. Helm, J. R. Herbert, S. K. Herzog, R. L. Holberton, S. B. Holmes, A. M. A. Holthuijzen, J. H. Homan, J. P. Hoover, S. L. Hopp, D. C. Houston, M. Hughes, W. G. Hunt, W. C. Hunter, T. A. Hurly, R. L. Hutto, J. Hyman, L. Igl, J. L. Ingold, E. E. Inigo-Elias, D. W. Inouye, M. L. Isler, E. Jablonka, B. J. S. Jackson, J. A. Jackson, J. R Jacobs, E M. Jaksic, E C. James, J. R. Jehl, Jr., K. D. Jenkins, S. Jenni-Eier- mann, B. Jobin, K. R Johnson, L. S. Johnson, C. G. Jones, D. N. Jones, I. L. Jones, J. Jones, R. C. Jones, S. L. Jones, L. Joseph, M. V. Kalyakin, R. Kannan, J. F. Kelly, P. L. Ken- nedy, K. P. Kenow, J. Kenyon, D. M. Keppie, A. J. Keyser, J. C. Kilgo, D. I. King, E. M. Kirsch, M. N. Kochert, W. D. Koenig, R. R. Koford, K. T. Koivula, N. B. Kotliar, I. Krams, G. Krapu, A. W. Kratter, J. A. Kush- lan, C. Ladd, P. Laiolo, J. D. Lang, S. M. Lanyon, R. R Larkin, K. Larsson, S. Latta, B. Lauro, M. J. Lawes, A. R Leif, D. M. Leslie, Jr., J. Leyrer, J. T. Lifjeld, J. D. Ligon, C. A. Lindell, D. B. Lindenmayer, B. D. Linkhart, B. C. Livezey, J. Lloyd, J. L. Lockwood, B. A. Loiselle, S. Lovari, P. E. Lowther, J. R. Lucas, J. Lusk, R. S. Lutz, R. M. Mac Nally, 442 REVIEWERS EOR VOLUME 1 17 443 S. A. MacDougall-Shackleton, T. D. Male, M. L. Mallory, J. C. Manolis, P. Manzano, C. A. Marantz, L. O. Marcondes-Machado, L. Marone, M. Marquiss, H. D. Marshall, M. R. Marshall, K. A. Martin, T. E. Martin, B. W. Massey, T. L. Master, S. J. Maxson, D. A. McCallum, N. McCanch, J. P. McCarty, B. R. McClelland, M. C. McGrady, J. A. McNeely, S. B. McRae, E. H. Merrill, E. T. Mezquida, E. H. Miller, M. R. Miller, B. A. Millsap, D. W. Mock, A. P. Moller, M. Monkkonen, E R. Moore, M. S. Mooring, S. R. Morris, J. L. Morrison, M. L. Morrison, R. I. G. Morrison, C. A. Morrissey, D. H. Morse, E. S. Morton, M. T. Murphy, L. Nagle, K. A. Nagy, K. Na- oki, I. Nascimento, D. A. Nelson, J. T. Nelson, S. A. Nesbitt, J. D. Nichols, E. Nol, M. Nores, C. J. Norment, E. Nycander, J. R. Obeso, T. J. O’Connell, K. R B. Oh, C. Olivo, A. L. O’Loghlen, S. A. H. Osborn, K. A. Otter, G. W. Page, B. Palmer, J. W. Parker, P Paton, K. Payne, R. B. Payne, S. E Pearson, B. D. Peer, C. J. Pendlebury, C. J. Pennycuick, M. E. Per- eyra, D. Perkins, M. R. Perrin, L. J. Petit, J. R. Phillips, M. Pichorim, T. Piersma, P J. Pietz, M. A. Pizo, S. M. Plentovich, C. M. S. Plowright, R. G. Pople, W. Post, B. Poulin, A. N. Powell, L. Powell, H. Poysiit, H. D. Pratt, T. D. Price, R. Probst, C. Pruett, R. O. Prum, K. L. Purcell, P Pyle, A. N. Radford, C. J. Ralph, J. H. Rappole, P C. Rasmussen, D. H. Reed, K. Reese, L. Rejt, J. V. Remsen, L. M. Renjifo, K. Renton, C. Restrepo, S. J. Reynolds, O. E. Rhodes, Jr., C. A. Ribic, S. Richardson, R. E. Ricklefs, R. S. Ridgely, K. Riebel, C. C. Rimmer, J. D. Rising, G. Ritch- ison, F. F. Rivera-Milan, C. S. Robbins, M. B. Robbins, R. J. Robel, J.-M. Roberge, G. J. Robertson, S. K. Robinson, W. D. Robin- son, A. D. Rodewald, J. A. Rodgers, Jr., O. Rojas, D. Rollins, C. M. Romagosa, J. J. Rop- er, D. Rosenberg, R. N. Rosenfield, S. Rosen- stock, R. R. Roth, S. I. Rothstein, J. A. Royle, M. A. Rumble, E. M. Russell, G. J. Russell, R. Russell, J. M. Ruth, M. R. Ryan, R. A. Ryder, V. A. Saab, E Sanders, J. E Saracco, J.-P. Savard, M. Schmid, J. Schmutz, M. A. Schroeder, T. S. Schulenberg, K. Schulze- Hagen, T. W. Schwertner, J. M. Scott, W. A. Searcy, J. C. Senar, T. L. Shaffer, P Shaw, D. A. Shealer, M. H. Sherfy, L. L. Short, W. G. Shriver, D. Shutler, J. G. Sidle, L. Siefferman, N. J. Silvy, S. K. Skagen, J. N. M. Smith, J. W. Snodgrass, D. W. Snow, N. F. R. Snyder, J. A. Soha, J. J. Soler, M. Soler, M. Stake, M. T. Stanback, T. R. Stanley, B. B. Steele, L. Stempniewicz, E G. Stiles, D. E Stotz, B. M. Strausberger, B. J. M. Stutchbury, M. Sul- livan Blanken, D. L. Swanson, T. Swem, P. W. Sykes, T. Szekely, M. Takagi, K. Tarvin, J. G. Tello, J. Tewksbury, W. E. Thogmartin, C. E Thompson, B. W. Tobalske, C. A. Toft, M. P. Toms, H. B. Tordoff, O. Tostain, C. H. Trost, J. W. Tucker, R. Urbanek, E. D. Urqu- hart, W. M. Vander Haegen, J. H. Vega Ri- vera, J. Verner, P. D. Vickery, M. V. Vieira, K. T. Vierling, M.-A. Villard, P. A. Vohs, M. J. Wade, J. W. Walk, E. Walters, J. R. Walters, A. B. Ward, N. Warnock, J. W. Watson, M. S. Webster, J. D. Weckstein, H. P. Weeks, Jr., W. Wehtje, D. Wenny, J. K. Wetterer, N. T. Wheelwright, G. C. White, M. A. White- head, M. J. Whittingham, T. L. Whitworth, K. L. Wiebe, M. Wikelski, G. J. Wiles, J. W. Wiley, T. Willebrand, E. O. Willis, M. F. Willson, S. K. Willson, M. Wink, M. Winter, B. Wolf, C. P. Woods, G. Woolfenden, T. F. Wright, M. B. Wunder, J. M. Wunderle, R. H. Yahner, K. Yasukawa, R. Yo.sef, B. E. Young, J.-X. Zhang, K. J. Zimmer, K. Zys- kowski. Wilson Bulletin 1 1 7(4):444— 456, 2005 Index to Volume 117, 2005 By Kathleen G. Beal This index includes references to genera, species, authors, and key words or terms. In addition to avian species, references are made to the scientific names of all vertebrates mentioned within the volume and other taxa mentioned prominently in the text. Nomenclature follows the AOU Check-list of North American Birds (1998) and its supplements. Reference is made to books reviewed, and announcements as they appear in the volume. A abundance of Primolius maracana and other parrots, 154-164 Accipiter cooperii, 237-244 gentilis, 237, 238, 242 nisus, 238, 406 striatus, 237-244, 272 Actitis macularius, 253, 257 Adams, Amy A. Yackel, see Skagen, Susan K., , and Rod D. Adams Adams, Rod D., see Skagen, Susan K., Amy A. Yackel Adams, and Aerodramus spp., 319 Agelaius phoeniceus, 263, 280-290, 379 Aimophila cassinii, 64, 67 Ainley, David, review by, 323-324 Alopex lagopus, 233 Alstrdm, Per, and Krister Mild, Pipits and Wagtails, reviewed, 426-427 Alterman, Lynn E., James C. Bednarz, and Ronald E. Thill, Use of group-selection and seed-tree cuts by three early-successional migratory species in Arkansas, 353-363 Alvarez Alonso, Jose, see Whitney, Bret M., and Amadon, Dean, see Delacour, Jean, and Amazon, Blue-fronted, see Amazona aestiva Amazona aestiva, 97, 155 farinosa, 296—305 finschi, 291-295 ochrocephala, 296-305 viridigenalis, 291 Ammodramus bairdii, 30, 64, 67 henslowii, 64, 211-225 (Frontispiece) leconteii, 214, 403-404 nelsoni, 403-404 savannarum, 24, 57, 64, 67, 216 Ammodytes sp., 137 Anas acuta, 364-374 crecca crecca, 371 Anderson, Stanley H., see Plumb, Regan E., Fritz L. Knopf, and Andres, Brad A., Brian T. Browne, and Diana L. Brann, Composition, abundance, and timing of post-breeding migrant landbirds at Yakutat, Alaska, 270-279 Ankney, C. Davison, see Zimmerling, J. Ryan, and Antbird, Allpahuayo, see Percnostola arenarum Bicolored, see Gymnopithys leucaspis Ocellated, see Phaenostictus mcleannani Spotted, see Hylophylax naevioides Stripe-backed, see Myrmorchilus strigilatus Wing-banded, see Myrmornis torquata Anthus rubescens, 263, 279 Antilocapra americana, 15 Antwren, Ancient, see Herpsilochmus gentryi Aphelocoma coerulescens, 409 ultramarina, 377 Ara ambigua, 301 ararauna, 296-305 chloroptera, 296—305 macao, 296-305 severus, 296-305 Aratinga acuticaudata, 97 leucophthalmus, 154—164, 296—305 weddellii, 296-305 Ardea cinerea, 388 Arendt, Wayne J., John Faaborg, George E. Wallace, and Orlando H. Garrido, Biometrics of birds throughout the Greater Caribbean Basin, re- viewed, 108-110 Aribeus spp., 301 Arremonops rufivirgatus, 379 Ashley, Jane, see Evans, Beth E. I., , and Stuart J. Marsden Asia flammeus, 72, 80, 177-184 Athene cunicularia, 177—184 Atwood, Jonathan L., see Lambert, J. Daniel, Kent P. McFarland, Christopher C. Rimmer, Steven D. Faccio, and Auriparus flaviceps, 379 Aviel, Shaul, see Charter, Motti, Amos Bouskila, , and Yossi Leshem B Baccus, John T, see Small, Michael E, Cynthia L. Schaefer, , and Jay A. Roberson badger, see Taxidea taxus banding resighting of marked Haematopus palliatus, 382- 385 Banks, Richard C., review by, 106-107 Barbour, Philip J., see Smith, Mark D., , L. Wes Burger, Jr., and Stephen J. Dinsmore Bare-eye, see Phlegopsis nigromaculata Barnhill, Rose Ann, Dora Weyer, W. Ford Young, Kimberly G. Smith, and Douglas A. James, Breeding biology of Jabirus (Jabiru mycteria) in Belize, 142-153 444 INDEX TO VOLUME 117 445 Barquero, Marco D., and Branko Hilje, House Wren preys on introduced gecko in Costa Rica, 204- 205 B aired- Woodcreeper, Northern, see Dendrocolaptes sanctithomae Bartramia longicauda, 57 bat, see Aribeus spp. Becard, White-winged, see Pachyrarnphus polychop- terus Bechtoldt, Catherine L., and Philip C. Stouffer, Home- range size, response to fire, and habitat pref- erences of wintering Henslow’s Sparrows, 211- 225 Bednarz, James C., see Alterman, Lynn E., , and Ronald E. Thill behavior acquisition of aerial foraging skills in Mimas poly- g lottos, 313-315 cooperative hunting in immature Lanius excubitor, 407-409 dunking by Corvus brachyrhynchos, 405—407 filial cannibalism in Carpodacus mexicanus, 413- 415 foliage bathing by Falco deiroleucus, 415-418 foraging of Cephalopterus glabricollis with an as- semblage of army ant-following birds, 418- 420 foraging success of Mycteria americana in tidal and non-tidal habitats, 386-389 frugivory on red elderberry, 336-340 head-down display in Molothrus aeneus, 410-412 influence of foraging and roosting behavior on home-range size and movement patterns of Passerculus sandwichensis, 63-71 movement of breeding Charadrius montanus, 128— 132 movement of Primolius maracana and other parrots, 154-164 of Lagopus lagopus on water surface, 12-14 seasonal variation in activity patterns of juvenile Amazona finschi, 291-295 winter foraging of Clangula hyemalis in the Baltic Sea, 133-141 Bell, Colleen E., see Clark, Arthur R., , and Sara R. Morris bison, see Bison bison Bison bison, 15, 128 Blackbird, Red-winged, see Agelaius phoeniceas Rusty, see Euphagus carolinus Bluebird, Eastern, see Sialia sialis Bobolink, see Dolichonyx oryzivorus Bobwhite, Northern, see Colinus virginianus Botnbycilla cedrorani, 339 Bouskila, Amos, see Charter, Motti, , Shaul Aviel, and Yossi Leshem Braman, Shelby C., and Darrell W. Pogue, Eastern Bluebird provisions nestlings with flat-headed snake, 100- 1 01 Brann, Diana L., see Andres, Brad A., Brian I. Brow- ne, and Brant, see Branta bernicla Branta bernicla, 365 canadensis, 370 leucopsis, 372 breeding biology divorce in Saxicola dacotiae, 317-319 of Jabiru mycteria in Belize, 142-153 of Paras varias namiyei, 189-193 parental investment during incubation in Yahina branneiceps, 306—312 reproductive success of Charadrias melodas, 165- 171 variations in incubation patterns of Agelaias phoe- niceas, 280-290 Brewer, David, reviews by, 322-323, 426-427 Brightsmith, Donald J., Parrot nesting in southeastern Peru; seasonal patterns and keystone trees, 296-305 Brisbin, I. Lehr, Jr., see Depkin, E Chris, Laura K. Estep, A. Lawrence Bryan, Jr., Carol S. El- dridge, and Brooks, Daniel M., review by, 207-208 Brotogeris cyanoptera, 299, 300 sanctithomae, 299, 300 versicolaras, 154-164 Browne, Brian T, see Andres, Brad A., , and Diana L. Brann Bryan, A. Lawrence, Jr., see Depkin, E Chris, Laura K. Estep, , Carol S. Eldridge, and I. Lehr Brisbin, Jr. Bacephala albeola, 44-55 Bufflehead, see Bacephala albeola bullsnake, see Pitaophis melanoleacas Bunting, Indigo, see Passerina cyanea Lark, see Calamospiza melanocorys Painted, see Passerina ciris Burger, L. Wes, Jr., see Smith, Mark D., Philip J. Bar- bour, , and Stephen J. Dinsmore Burril, Sean E., see Zimmerman, Christian E., Nicola Hillgruber, , Michelle A. St. Peters, and Jennifer D. Wetzel Burris, John M., and Alan W. Haney, Bird communi- ties after blowdown in a late-successional Great Lakes spruce-fir forest, 341-352 Bateo jamaicensis, 1 86 lagopas, 232 c Calamospiza melanocorys, 23—34 Calcarias lapponicas, 279 ornatas, 24 Campephilas leacopogon, 97 Canis latrans, 24. 3 I Capuano, Bianca, see Stutchbury. Bridget J. M., , and Gail S. b'raser Cardinal, Northern, see Cardinalis cardinalis Cardinalis cardimdis, 195, 261, 264, 337. 338 Cardaelis flananea, 270-279 pinas, 270-279 psidtria, 378 caribou, see Rangifer tarandas C'arpodacas me\icani4s, 378, 413-415 446 THE WILSON BULLETIN • Vol. ! 17, No. 4, December 2005 Casazza, Michael L., see Miller, Michael R., John Y. Takekawa, Joseph R Fleskes, Dennis L. Orth- meyer, , David A. Haukos, and William M. Perry Casiornis rufa, 97 Casiornis, Rufous, see Casiornis rufa Catbird, Gray, see Diimetella carolinensis Catharus hicknelli, 1 — 1 1 (Frontispiece) fuscescens, 337, 338 giittatiis, 270-279, 333, 347, 348 minimus, 1, 276, 279 spp., 398 ustulatus, 7, 37, 245-257, 279, 347, 348 Caziani, Sandra M., see Derlindati, Enrique J., and Cephalopterus glabricollis, 418-420 Certhia americana, 273, 347 Cerx’us elaphus, 57 Ceryle alcyon, 252, 257 Chace, Jameson E, Host use by sympatric cowbirds in southeastern Arizona, 375-381 Chachalaca, Chaco, see Ortalis canicollis Charadrius melodus, 165—171 montanus, 15—22, 31, 128—132 Charter, Motti, Amos Bouskila. Shaul Aviel, and Yossi Leshem, First record of Eurasian Jackdaw (Corx’us monedula) parasitism by Great Spotted Cuckoo (Clamator glandarius) in Israel, 201- 204 Chasiempis sandwichensis, 82 Chat, Yellow-breasted, see Icteria virens Chaves-Campos, Johel, Bare-necked Umbrellabird {Cephalopterus glabricollis) foraging at an un- usually large assemblage of army ant-following birds, 418-420 Chen caerulescens, 370, 371 Chickadee, Black-capped, see Poecile atricapillus Boreal, see Poecile hudsonica Chestnut-backed, see Poecile rufescens Mountain, see Poecile gambeli chipmunk, eastern, see Tamias striatus Siberian, see Tamias sibiricus Chondestes grammacus, 261, 264 Chrysococcyx spp., 375, 379 Ciconia ciconia, 367 Cinclus mexicanus, 252, 257 Clamator glandarius, 201-204 spp., 375, 379 Clangula hyemalis, 133-141 Clark, Arthur R., Colleen E. Bell, and Sara R. Morris, Comparison of daily avian mortality character- istics at two television towers in western New York, 1970-1999, 35-43 Clupea harengus, 134, 137 Cochlearius cochlearius, 150 Colaptes auratus, 273 melanolaimus, 97 Colinus virginianus, 264, 315-316 Collocalia spp., 319 Columba livia, 372 maculosa, 97 picazuro, 95, 97 Columbina picui, 97 community after blowdown in a late-successional Great Lakes spruce-fir forest, 341-352 Condon, Anne M., Eric L. Kershner, Brian L. Sullivan, Douglass M. Cooper, and David K. Garcelon, Spotlight surveys for grassland owls on San Clemente Island, California, 177-184 Contopus cooperi, 253, 257, 279 pertinax, 377 sordidulus, 377 Cooper, Douglass M., see Condon, Anne M., Eric L. Kershner, Brian L. Sullivan, , and David K. Garcelon Cormorant, Double-crested, see Phalacrocorax auritus Corvinella spp., 380 Corvus brachyrhynchos, 405-407 caurinus, 279, 406 corax, 203, 272, 273, 406, 409 corone, 201, 203, 406 macrorhynchos, 1 9 1 monedula, 201-204 rhipidurus, 201 splendens, 201 spp., 405 Coryphospingus cucullatus, 95 Cossypha spp., 380 Coturnix japonica, 25 Cowbird, Bay-winged, see Molothrus badius Bronzed, see Molothrus aeneus Brown-headed, see Molothrus ater Giant, see Molothrus oryzivora Screaming, see Molothrus rufoaxillaris Shiny, see Molothrus bonariensis coyote, see Canis latrans Crane, Sandhill, see Grus canadensis Creeper, Brown, see Certhia americana Crossbill, Himalayan, see Loxia curvirostra himalay- ensis Parrot, see Loxia pytyopsittacus Red, see Loxia curvirostra Scottish, see Loxia scotica Two-barred, see Loxia leucoptera bifasciata White-winged, see Loxia leucoptera Crotalus v. viridis, 24 Crow, American, see Corvus brachyrhynchos Carrion, see Corvus corone House, see Corvus splendens Jungle, see Corvus macrorhynchos Northwestern, see Corvus caurinus Cuckoo, African, see Cuculus gularis Black, see Cuculus clamosus Great Spotted, see Clamator glandarius Red-breasted, see Cuculus solitarius cuckoo, see Cuculus spp., Chrysococcyx spp., Cla- mator spp., Eudynamys spp., Oxylophus spp., Scythrops spp. Cuculus clamosus, 380 gularis, 380 solitarius, 380 INDEX TO VOLUME 1 17 447 spp., 375, 379 Cyanocitta stelleri, 272, 273, 377 Cygnus columbianus, 370 cygnus, 370 olor, 198 spp., 365 Cynomys leucurus, 17 ludovicianus, 1 28- 1 32 spp., 15 D Davis, Lloyd S., and Martin Renner, Penguins: living in two worlds, reviewed, 323-324 Davis, William E., Jr., reviews by, 107-108, 324-325, 421-422, 422-423 deer, red, see Cervus elaphus white-tailed, see Odocoileus virginianus Delacour, Jean, and Dean Amadon, Curassows and re- lated birds, reviewed, 207-208 Dendrocolaptes sanctithomae, 419 Dendroica caerulescens, 37, 43 castanea, 37 coronata, 270-279, 341-352, 378 discolor, 353-363 fusca, 341-352 graciae, 378 magnolia, 37, 347 nigrescens, 378 pensylvanica, 341-352, 358 petechia, 253, 257, 270-279 striata, 9, 37, 276, 279 tigrina, 347 townsendi, 273 V ire ns, 37 Depkin, F. Chris, Laura K. Estep, A. Lawrence Bryan, Jr., Carol S. Eldridge, and 1. Lehr Brisbin, Jr., Comparison of Wood Stork foraging success and behavior in selected tidal and non-tidal habitats, 386-389 Derlindati, Enrique J., and Sandra M. Caziani, Using canopy and understory mist nets and point counts to study bird assemblages in Chaco for- ests, 92-99 Desmond, Martha J., see Ginter, Daniel L., and Dicrurus spp., 380 Dinsmore, Stephen J., see Smith, Mark D., Philip J. Barbour, L. Wes Burger, Jr., and Dipper, American, see Cinclus mexicanus distribution model of Catharus hicknelli in northeastern United States, 1-11 dog, prairie, .see Cynomys ludovicianus, Cynomvs spp. white-tailed prairie, see Cynomys leucurus Dolichonyx oryzivorus, 57 Dove, Collared, see Streptopelia decaocto Mourning, see Zenaida macroura White-tipped, see Ix’ptotila verreauxi White-winged, see Zenaida asiatica Dreitz, Victoria J., Michael B. Wunder, and I ritz L. Knopf, Movements and home ranges of Moun- tain Plovers raising broods in three Colorado landscapes, 128-132 drongo, see Dicrurus spp. Drymornis bridgesii, 97 Dryocopus schulzi, 97 Duck, Long-tailed, see Clangula hyemalis Dumetella carolinensis, 337, 338 Duncan, David C., see Harris, Wayne C., , Re- nee J. Franken, Donald T. McKinnon, and Heather A. Dundras Dundas, Heather A., see Harris, Wayne C., David C. Duncan, Renee J. Franken, Donald T. Mc- Kinnon, and E Eagle, Bald, see Haliaeetus leucocephalus Eared-dove, see Zenaida auriculata Eaton, Muir D., and Daniel L. Hernandez, A cause of mortality for aerial insectivores?, 196-198 ecology of breeding Myadestes palmeri, 12— of breeding Zenaida asiatica, 172-176 Edelaar, Pirn, Ron E. Phillips, and Peter Knops, Sex- ually dimorphic body plumage in juvenile crossbills, 390-393 eggs description for Platycichla leucops, 394-399 Eider, Common, see Somateria mollissima Eisermann, Knut, An observation of foliage-bathing by an Orange-breasted Falcon (Falco deiroleucus) in Tikal, Guatemala, 415-418 Elaenia, White-crested, see Elaenia albiceps Elaenia albiceps, 95 Elaphe obsoleta, 100 Eldridge, Carol S., see Depkin, F. Chris, Laura K. Es- tep, A. Lawrence Bryan, Jr., , and 1. Lehr Brisbin, Jr. Elepaio, see Chasiempis sandwichensis Empidonax alnorum, 270-279, 347 difficilis, 245-257 flaviventris, 9, 279, 341-352 fulvifrons, 377 hammondii, 245-257 minimus, 347 occidentalis, 253 trail I a, 253, 257 Empidonomus aurantioatrocrisiatus, 97 energy expenditure model for wintering waterfowl, 44-55 Eremophila alpestris, 23-34 Erickson, Richard A., and Steve N. G. Howell (Eds.), Birds of the Baja California Peninsula: status, distribution, and taxonomy, reviewed. 208-209 ermine, see Mustela erminea Estep. Laura K., see Depkin. E Chris. , A. Lawrence Bryan. Jr.. C’arol S. Eldridge, and I. Lehr Brisbin. Jr. Eudynamys spp.. 375 Euphagus carolinus, 279 Evans, Beth E7 I., Jane Ashley, and Stuart J. Marsdcn. Abundance, habitat use. and mt)vemcnts of 448 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Blue-winged Macaws {Primolius maracana) and other parrots in and around an Atlantic Forest reserve, 154-164 F Faaborg, John, see Arendt, Wayne J., , George E. Wallace, and Orlando H. Garrido Faccio, Steven D., see Lambert, J. Daniel, Kent P. McFarland, Christopher C. Rimmer, , and Jonathan L. Atwood Falco columbarius, 417 deiroleucus, 415—418 eleonorae, 417 mexicanus, 186 peregrinus, 226—236, 415 rufigularis, 415 spp., 417 subbuteo, 416 tinnunculus, 201 Falcon, Bat, see Falco rufigularis Eleonora’s, see Falco eleonorae Orange-breasted, see Falco deiroleucus Peregrine, see Falco peregrinus Prairie, see Falco mexicanus Fancy, Steven G., see Snetsinger, Thomas J., Christina M. Herrmann, Dawn E. Holmes, Christopher D. Hayward, and ferret, black-footed, see Mustela nigripes Ficedula hypoleuca, 281, 402 Finch, House, see Carpodacus mexicanus Red-crested, see Coryphospingus cucullatus Fleskes, Joseph R, see Miller, Michael R., John Y. Ta- kekawa, , Dennis L. Orthmeyer, Mi- chael L. Casazza, David A. Haukos, and Wil- liam M. Perry Flicker, Northern, see Colaptes auratus Flycatcher, Alder, see Empidonax alnorum Brown-crested, see Myiarchus tyrannulus Buff-breasted, see Empidonax fulvifrons Cordilleran, see Empidonax occidentalis Fork-tailed, see Tyrannus savana Hammond’s, see Empidonax hammondii Least, see Empidonax minimus Olive-sided, see Contopus cooperi Pacific Slope, see Empidonax dijficilis Pied, see Ficedula hypoleuca Social, see Myiozetetes similis Streaked, see Myiodynastes maculatus Willow, see Empidonax traillii Yellow-bellied, see Empidonax fiaviventris fox, arctic, see Alopex lagopus swift, see Vulpes velox Franken, Renee J., see Harris, Wayne C., David C. Duncan, , Donald T. McKinnon, and Heather A. Dundras Fraser, Gail S., see Stutchbury, Bridget J. M., Bianca Capuano, and Frith, Clifford B., and Dawn W. Frith, The bowerbirds; Ptilonorhynchidae, reviewed, 107-108 Frith, Dawn W, see Frith, Clifford B., and Fuller, Mark R., see Wightman, Catherine S., and G Garcelon, David K., see Condon, Anne M., Eric L. Kershner, Brian L. Sullivan, Douglass M. Coo- per, and Garrett, Kimball L., and Kathy C. Molina, A field ob- servation of the head-down display in the Bronzed Cowbird, 410-412 Garrett, Kimball L., review by, 206-207 Garrido, Orlando H., see Arendt, Wayne J., John Faa- borg, George E. Wallace, and Garrulus glandarius, 201 Gasterosteus aculeatus, 137 Gavia immer, 198, 257 gecko, house, see Hemidactylus frenatus Geothlypis trichas, 37, 279 Gilbert, William M., Paul M. Nolan, Andrew M. Stoehr, and Geoffrey E. Hill, Filial cannibalism at a House Finch nest, 413-415 Ginter, Daniel L., and Martha J. Desmond, Influence of foraging and roosting behavior on home- range size and movement patterns of Savannah Sparrows wintering in south Texas, 63-71 Glaucidium brasilianum, 185—188 Gnatcatcher, Guianan, see Polioptila guianensis Iquitos, see Polioptila clementsi (Frontispiece) Masked, see Polioptila dumicola Para, see Polioptila paraensis Rio Negro, see Polioptila facilis Tropical, see Polioptila plumbea Godwit, Bar-tailed, see Limosa lapponica Goldfinch, Lesser, see Carduelis psaltria Goose, Barnacle, see Branta leucopsis Canada, see Branta canadensis Lesser Snow, see Chen caerulescens Goshawk, Northern, see Accipiter gentilis Gould, Carol Grant, The remarkable life of William Beebe; explorer and naturalist, reviewed, 421- 422 Grackle, Antillean, see Quiscalus niger Carib, see Quiscalus lugubris Common, see Quiscalus quiscula Great-tailed, see Quiscalus mexicanus Graptemys ouachitensis, 411 Grosbeak, Black-headed, see Pheucticus melanoce- phalus Blue, see Passerina caerulea Pine, see Pinicola enucleator Rose-breasted, see Pheucticus ludovicianus Grus canadensis, 276 Gull, Herring, see Larus argentatus Gustafson, Mary, reviews by, 1 10—1 1 1, 208—209, 325— 326 Gymnopithys leucaspis, 419 H habitat nest survival relative to patch size in fragmented shortgrass prairie landscape, 23-34 INDEX TO VOLUME 1 17 449 of breeding Seiurus aurocapilla in northwestern Pennsylvania, 327-335 preferences of wintering Ammodramus henslowii, 211-225 selection patterns of Falco peregrinus in central West Greenland, 226-236 use by Primolius maracana and other parrots, 154- 164 use by riparian and upland birds in coastal British Columbia rainforest, 245-257 Haematopus ostralegus, 382, 383 palliatus, 382-385 Haliaeetus leucocephalus, 198 Haney, Alan W, see Burris, John M., and Hannah, Kevin C., An apparent case of cooperative hunting in immature Northern Shrikes, 407- 409 Harper, Geoffrey H., see Patrikeev, Michael and Harris, Wayne C., David C. Duncan, Renee J. Franken, Donald T. McKinnon, and Heather A. Dundras, Reproductive success of Piping Plovers at Big Quill Lake, Saskatchewan, 165-171 Haukos, David A., see Miller, Michael R., John Y. Ta- kekawa, Joseph P. Fleskes, Dennis L. Orthmey- er, Michael L. Casazza, , and William M. Perry Hawk, Cooper’s, see Accipiter cooperii Red-tailed, see Buteo jamaicensis Rough-legged, see Buteo lagopus Sharp-shinned, see Accipiter striatus Hayward, Christopher D., see Snetsinger, Thomas J., Christina M. Herrmann, Dawn E. Holmes, , and Steven G. Fancy Hemidactylus frenatus, 204-205 Hemignathus lucidus, 81 Hemitriccus spp., 124 Hendricks, Paul, see Nordhagen, Ted J., Matthew P Nordhagen, and Hernandez, Daniel L., see Eaton, Muir D., and Heron, Boat-billed, see Cochlearius cochlearius Grey, see Ardea cinerea Herpsilochmus arenarum, 1 1 3 gentryi, 113, 125 herring, Baltic, see Clupea harengus Herrmann, Christina M., see Snetsinger, Thomas J., , Dawn E. Holmes, Christopher D. Hay- ward, and Steven G. Fancy Heterodon nasicus, 24 Higuchi, Hiroyoshi, see Yamaguchi, Noriyuki, and Hilje, Branko, see Barquero, Marco D., and Hill, Geoffrey E., see Gilbert, William M., Paul M. Nolan, Andrew M. Stoehr, and Hillgruber, Nicola, see Zimmerman, Christian li., , Sean E. Burril, Michelle A. St. Peters. and Jennifer D. Wet/el Hirundo rustica, 279 Hobby, Eurasian, see hcdco suhhuteo Holmes, Dawn E., see Snetsinger, Thomas J., Christina M. Herrmann, , Christopher D. Hay- ward, and Steven G. Fancy home range of breeding Charadrius montanus, 128-132 size for wintering Ammodramus henslowii, 21 1—225 Hosner, Peter A., Regurgitated mistletoe seeds in the nest of the Yellow-crowned Tyrannulet (Tyran- nulus elatus), 319-321 Howell, Steve N. G., see Erickson, Richard A., and Hummingbird, Rufous, see Selasphorus rufus Hylophylax naevioides, 314, 419 I, J Icteria virens, 353-363 Icterus bullockii, 378, 379 spp., 195 Illera, Juan Carlos, Divorce in the Canary Island Stonechat (Saxicola dacotiae), 317-319 Ixoreus naevius, 245-257, 270-279 Jabiru, see Jabiru mycteria Jabiru mycteria, 142-153 Jackdaw, Eurasian, see Corvus monedula James, Douglas A., see Barnhill, Rose Ann, Dora Wey- er, W. Ford Young, Kimberly G. Smith, and Jaramillo, Alvaro, Birds of Chile, reviewed, 322-323 Jay, Eurasian, see Garrulus glandarius Mexican, see Aphelocoma ultramarina Steller’s, see Cyanocitta stelleri Jehl, Joseph R., Jr., review by, 106-107 Johnstone, R. E., and G. M. Storr, Handbook of West- ern Australian birds, vol. II: passerines (Blue- winged Pitta to goldfinch), reviewed, 422-423 Junco, Dark-eyed, see Junco hyemalis Oregon, see Junco hyemalis oreganus Slate-colored, see Junco hyemalis hyemalis Yellow-eyed, see Junco phaeonotus Junco hyemalis, 273, 333 hyemalis hyemalis, 273, 274, 276 hyemalis oreganus, 273, 274, 276 phaeonotus, 377 K Kamao, see Myadestes myadestinus Kershner, Eric L., see Condon, Anne M., , Bri- an L. Sullivan, Douglass M. Cooper, and David K. Garcelon Kestrel, Eurasian, see halco tinnunculus Kingbird, Cassin’s, see Tyrannus vociferans Kingfisher, Belted, .see Ceryle alcyon Kinglet, Golden-crt)wned, see Regulus satrapa Ruby-crowned, see Pegidus calendula Kiskadee, Great, see Pitangus sulphuratus Klein, Daniel, .Ir., review by. 423-425 Knopf, Frit/ L., see Droit/, Victoria J.. Michael B. Wunder. and Knopf. Frit/ L.. see I’lumb, Regan I:.. . and Stanley IT Anderson 450 THE WILSON BULLETIN • VoL 117, No. 4, December 2005 Knops, Peter, see Edelaar, Pirn, Ron E. Phillips, and Krabbe, Niels, and Jonas Nilsson, Birds of Ecuador, reviewed, 110-111 L Lagopus lagopus, 12-14 muta, 12-14 Lambert, J. Daniel, Kent P. McFarland, Christopher C. Rimmer, Steven D. Faccio, and Jonathan L. At- wood, A practical model of Bicknell’s Thrush distribution in the northeastern United States, 1-11 Lanius excubitor, 279, 407 ludovicianus, 407 Lark, Horned, see Eremophila alpestris Larus argentatus, 413 Latta, Steven C., review by, 108-110 Lee, Pei-Fen, see Yuan, Hsiao- Wei, Sheng-Feng Shen, Kai-Yin Lin, and Lepidocolaptes angustirostris, 97 Leptotila verreauxi, 97 Leshen, Yossi, see Charter, Motti, Amos Bouskila, Shaul Aviel, and Leslie, David M., Jr., see Whittier, Joanna B., and Lima, Steven L., see Roth, Timothy C., II, , and William E. Vetter Limnothlypis swainsonii, 199-200 Limosa lapponica, 367 Londono, Gustavo Adolfo, A description of the nest and eggs of the Pale-eyed Thrush {Platycichla leucops), with notes on incubation behavior, 394-399 Longspur, Chestnut-collared, see Calcarius ornatus Lapland, see Calcarius lapponicus Loon, Common, see Gavia immer Loxia curvirostra, 273, 390-393 curvirostra himalayensis, 392 leucoptera, 9, 270-279 leucoptera bifasciata, 392 pytyopsittacus, 391, 392 scotica, 390-393 M Macaw, Blue-and-yellow, see Ara ararauna Blue-headed, see Propyrrhura couloni Blue-winged, see Primolius maracana Chestnut-fronted, see Ara severus Great Green, see Ara ambigua Red-and-green, see Ara chloroptera Red-bellied, see Orthopsittaca manilata Scarlet, see Ara macao Magpie, Black-billed, see Pica hudsonia Common, see Pica pica Yellow-billed, see Pica nuttalli Marsden, Stuart J., see Evans, Beth E. I., Jane Ashley, and Martin, Kathy, see Robinson, Patrick A., Andrea R. Norris, and Martin, Purple, see Progne subis McFarland, Kent R, see Lambert, J. Daniel, , Christopher C. Rimmer, Steven D. Faccio, and Jonathan L. Atwood McGowan, Conor R, Shiloh A. Schulte, and Theodore R. Simons, Resightings of marked American Oystercatchers banded as chicks, 382-385 McKinney, Richard A., and Scott R. McWilliams, A new model to estimate daily energy expendi- ture for wintering waterfowl, 44-55 McKinnon, Donald T, see Harris, Wayne C., David C. Duncan, Renee J. Franken, , and Heath- er A. Dundras McWilliams, Scott R., see McKinney, Richard A., and Meadowlark, Eastern, see Sturnella magna Western, see Sturnella neglecta Melanerpes formicivorus, 4 1 3 Meleagris gallopavo, 316 Melospiza georgiana, 258-269, 328, 347 lincolnii, 270-279 melodia, 258-269, 272, 273, 274, 328 Mephitis mephitis, 24, 31 spp., 56 Merganser, Common, see Mergus merganser Red-breasted, see Mergus serrator Mergus merganser, 252, 257 serrator, 366 Merlin, see Falco columbarius methods use of canopy and understory mist nests and point counts to study bird assemblages in Chaco forests, 92-99 use of radio transmitters to monitor Sterna antilla- rum chicks, 85-91 Microcerculus spp., 124 migration flight speed of Anas acuta determined using satellite telemetry, 364-374 of landbirds at Yakutat, Alaska, 270-279 Mild, Krister, see Alstrom, Per, and Miller, Michael R., John Y. Takekawa, Joseph P. Fles- kes, Dennis L. Orthmeyer, Michael L. Casazza, David A. Haukos, and William M. Perry, Flight speeds of Northern Pintails during migration determined using satellite telemetry, 364-374 Mimus polyglottos, 313-315 mink, see Mustela vison Mitchell, John H., Looking for Mr. Gilbert: the re- imagined life of an African American, re- viewed, 324-325 Mniotilta varia, 333, 341-352 Mockingbird, Northern, see Mimus polyglottos Moho braccatus, 81 Molina, Kathy C., see Garrett, Kimball L., and Molothrus aeneus, 194—196, 375—381, 410—412 ater, 194-196, 279, 354, 357, 358, 375-381, 403- 404, 410-412 badius, 410 bonariensis, 410—412 INDEX TO VOLUME 1 17 451 oryzivora, 194-196, 410 rufoaxillaris, 194 Monasa morphoeus, 419 Morand-Ferron, Julie, Dunking behavior in American Crows, 405-407 Morris, Sara R., see Clark, Arthur R., Colleen E. Bell, and mortality for aerial insectivores, 196-198 of wintering Accipiter striatus and A. cooperii, 237- 244 television tower, 35-43 Morton, Eugene S., Predation and variation in breeding habitat use in the Ovenbird, with special ref- erence to breeding habitat selection in north- western Pennsylvania, 327-335 Mustela erminea, 271 frenata, 24 nigripes, 131 vison, 271 Myadestes myadestinus, 81 ob scums, 72 palmeri, 72-84 spp., 398 Mycteria americana, 149, 150, 151, 386-389 Myiarchus tyrannulus, 97 Myioborus pictus, 375-381 Myiodynastes maculatus, 91 Myiopsitta monachus, 91 Myiozetetes similis, 320 Myrmorchilus strigilatus, 95 Myrmornis torquata, 103-105 N Nack, Jamie L., and Christine A. Ribic, Apparent pre- dation by cattle at grassland bird nests, 56-62 Nannopsittaca dachilleae, 300 nest description for Myrmornis torquata, 103-105 description for Platycichla leucops, 394-399 interspecific sharing by Poecile gambeli and Sitta canadensis, 400-402 of Tyrannulus elatus containing regurgitated mistle- toe seeds, 319-321 success of three early-successional species in Ar- kansas, 353-363 survival relative to prairie patch size, 23-34 usurpation by Sphyrapicus nuchalis of Sitta cana- densis, 101-103 nesting above ground by Colinus virginianus, 315-316 of parrots in southeastern Peru, 296-305 success of Parus varius namiyei, 189-193 nestling of Myrmornis torquata, 103-105 Night-Heron, Black-crowned, see Nycticorax nvcti- corax Nilsson, Jonas, see Krabbe, Niels and Nolan, Paul M., see Gilbert, William M., , An- drew M. Stoehr, and Geoffrey E. Hill Nordhagen, Matthew P, see Nordhagen, Ted J., , and Paul Hendricks Nordhagen, Ted J., Matthew P Nordhagen, and Paul Hendricks, Nelson’s Sharp-tailed Sparrow nest parasitized by Brown-headed Cowbird, 403- 404 Norris, Andrea R„ see Robinson, Patrick A., , and Kathy Martin Nukupuu, Kauai, see Hemignathus lucidus Nunbird, White-fronted, see Monasa morphoeus Nuthatch, Red-breasted, see Sitta canadensis Nycticorax nycticorax, 198 o Odocoileus virginianus, 57 Oenanthe oenanthe, 281 Opio, Christopher, see Rothenbach, Christine A., and Oporornis Philadelphia, 341-352 Oriole, Bullock’s, see Icterus bullockii oriole, see Icterus spp. Ortalis canicollis, 95 Orthmeyer, Dennis L., see Miller, Michael R„ John Y. Takekawa, Joseph P. Fleskes, , Michael L. Casazza, David A. Haukos, and William M. Perry Orthopsittaca manilata, 296-305 Osmerus eperlanus, 137 Ovenbird, see Seiurus aurocapilla Ovis aries, 51 Owl, Barn, see Tyto alba Burrowing, see Athene cunicularia Short-eared, see Asio flammeus Oxylophus spp., 375 Oystercatcher, American, see Haematopus palliatus Eurasian, see Haematopus ostralegus p, Q Pachyramphus polychopterus, 91 Panurus biarmicus, 390-393 Parakeet, Black-capped, see Pyrrhura rupicola Blue-crowned, see Aratinga acuticaudata Canary-winged, see Brotogeris versicolurus Cobalt-winged, see Brotogeris cyanoptera Dusky-headed, see Aratinga weddellii Maroon-bellied, see Pyrrhura frontalis Monk, .see Myiopsitta monachus Red-crowned, see Pyrrhura roseifrons Tui, see Brotogeris sanctithomae White-eyed, see Aratinga leucophthalmus parasitism host use by sympatric cowbirds in southeastern Ar- izona, 375-381 of Ammodramus nelsoni by Molothrus ater, 403- 404 of Corvus monedula by Clamator glandarius, 201- 204 of Glaucidium brasilianum by Protocalliphora sia- lia and Hesperocimex sonorensis, 185-188 452 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 of Limnothlypis swainsonii by Protocalliphora lar- vae, 199-200 of Quiscalus mexicanus by Molothrus aeneus, 194- 196 Parrot, Blue-headed, see Pionus menstruus Lilac-crowned, see Amazona finschi Mealy, see Amazona farinosa Orange-cheeked, see Pionopsitta varrabandi Red-crowned, see Amazona viridigenalis Scaly-headed, see Pionus maximiliani White-bellied, see Pionites leucogaster Yellow-crowned, see Amazona ochrocephala Parrotlet, Amazonian, see Nannopsittaca dachilleae Blue-winged, see Forpus xanthopterygius Dusky-billed, see Forpus sclateri Scarlet-shouldered, see Touit huetii Parula, Northern, see Parula americana Parula americana, 347, 348 Parus caeruleus, 186, 281, 392, 402 major, 392, 402 varius, 189-193 Passer domesticus, 239 Passerculus sandwichensis, 56-62, 63-71, 258-269, 270-279, 287 Passerella iliaca, 253, 261, 264, 270-279 Passerina caerulea, 378 ciris, 379 cyanea, 353-363 Patrikeev, Michael, and Geoffrey H. Harper (Ed.), The birds of Azerbaijan, reviewed, 423-425 Paulson, Dennis R., Shorebirds of North America: the photographic guide, reviewed, 425-426 Peer, Brian D., Stephen I. Rothstein, and James W Rivers, First record of Bronzed Cowbird para- sitism on the Great-tailed Grackle, 194-196 Pelecanus occidentalis, 198 Pelican, Brown, see Pelecanus occidentalis Percnostola arenarum, 113 Perry, William M., see Miller, Michael R., John Y. Takekawa, Joseph P. Fleskes, Dennis L. Orth- meyer, Michael L. Casazza, David A. Haukos, and Peterjohn, Bruce, review by, 425-426 Petrochelidon pyrrhonota, 186 Pewee, Greater, see Contopus pertinax Phaenostictus mcleannani, 419 Phalacrocorax auritus, 198 Phasianus colchicus, 56, 316 Pheasant, Ring-necked, see Phasianus colchicus Pheucticus ludovicianus, 336-340 melanocephalus, 377 Phillips, Ron E., see Edelaar, Pirn, , and Peter Knops Phlegopsis nigromaculata, 104 Phoenicurus phoenicurus, 402 Phylloscopus fuscatus, 333 Pica hudsonia, 273 nuttalli, 406 pica, 201 Picoides arcticus, 9 mixtus, 97 pubescens, 273, 337, 400 villosus, 245-257, 273 pig, feral, see Sus scrofa Pigeon, Picazuro, see Columba picazuro Rock, see Columba livia Spot-winged, see Columba maculosa Pinicola enucleator, 279 Pintail, Northern, see Anas acuta Pionites leucogaster, 296-305 Pionopsitta barrabandi, 300 Pionus maximiliani, 154-164 menstruus, 296-305 Pipilo erythrophthalmus, 261, 264, 337, 338 fuscus, 378 maculatus, 253, 378 Pipit, American, see Anthus rubescens Piranga flava, 375-381 ludoviciana, 375-381 olivacea, 336-340 Pitangus sulphuratus, 319, 321 Pituophis melanoleucus, 24 Platichthys flesus, 137 Platycichla flavipes, 97 leucops, 394-399 Plover, Mountain, see Charadrius montanus Piping, see Charadrius melodus plumage sexually dimorphic in juvenile Loxia spp., 390-393 Plumb, Regan E., Fritz L. Knopf, and Stanley H. An- derson, Minimum population size of Mountain Plovers breeding in Wyoming, 15-22 Poecile atricapillus, 273, 347, 401 gambeli, 400-402 hudsonica, 347 rufescens, 245-257, 270-279 Pogue, Darrell W., see Braman, Shelby C., and Polioptila californica, 123, 124 clementsi, sp. nov., 113-127 (Frontispiece) dumicola, 95 facilis, 113, 124 guianensis, 113-127 melanura, 123, 124 paraensis, 113, 124 plumbea, 117 schistaceigula, 113—127 Pomatoschistus sp., 137 Pooecetes gramineus, 67, 261, 264 population density and diversity of overwintering birds in Mis- sissippi, 258-269 minimum size for breeding Charadrius montanus, 15-22 spotlight surveys of grassland owls on San Clemen- te Island, California, 177-184 predation of grassland bird nests by cattle, 56-62 of Hemidactylus frematus by Troglodytes aedon, 204-205 of Tantilla gracilis by Sialia sialis, 100-101 Primolius maracana, 154—164 INDEX TO VOLUME 117 453 proceedings of the eighty-sixth annual meeting, 428-441 Procyon lotor, 56, 316 Progne subis, 186 pronghorn, see Antilocapra americana Propyrrhura couloni, 300 Proudfoot, Glenn A., Jessica L. Usener, and Pete D. Teel, Ferruginous Pygmy-Owls: a new host for Protocalliphora sialia and Hesperocimex son- orensis in Arizona, 185-188 Psittirostra psittacea, 81 Ptarmigan, Rock, see Lagopus muta Willow, see Lagopus lagopus Pyrrhura frontalis, 155 roseifrons, 296-305 rupicola, 300 Quail, Japanese, see Coturnix japonica Quiscalus mexicanus, 194-196, 410-412 niger, 410 quiscula, 406, 41 1 spp., 405 R racoon, see Procyon lotor Ramphastos spp., 300 Rangifer tarandus, 57 rat, black, see Rattus rattus rattlesnake, prairie, see Crotalus v. viridis Rattus rattus, 79, 83 Raven, Common, see Corvus corax Fan-tailed, see Corvus rhipidurus Redpoll, Common, see Carduelis flammea Redstart, American, see Setophaga ruticilla Common, see Phoenicurus phoenicurus Painted, see Myioborus pictus Regulus calendula, 270-279, 347 regulus, 273 satrapa, 37, 245-257, 270-279, 341-352 Renner, Martin, see Davis, Lloyd S., and Renton, Katherine, see Salinas-Melgoza, Alejandro, and Revels, Mia R., and Terry L. Whitworth, First record of Swainson’s Warbler parasitism by Protocal- liphora blow fly larvae, 199-200 Ribic, Christine A., see Nack, Jamie L., and Rimmer, Christopher C., see I.ambert, J. Daniel, Kent P. McFarland, , Steven D. Faccio, and Jonathan L. Atwood Riparia riparia, 279 Rivers, James W., see Peer, Brian D„ Stephen 1. Roth- stein, and Roberson, Jay A., see Small, Michael F, Cynthia L. Schaefer, John T. Baccus, and Robin, American, see Turdus migratorius Robin.son, Patrick A., Andrea R. Norris, and Kathy Martin, Interspecific nest sharing by Red- breasted Nuthatch and Mountain Chickadee, 400-402 Roth, Timothy C„ 11, Steven L. Lima, and William E. Vetter, Survival and cau.ses of mortality in win- tering Sharp-shinned Hawks and Cooper’s Hawks, 237-244 Rothenbach, Christine A., and Christopher Opio, Sap- suckers usurp a nuthatch nest, 101-103 Rothstein, Stephen L, see Peer, Brian D., , and James W Rivers Ruskyte, Dainora, see Zydelis, Ramunas, and s Salinas-Melgoza, Alejandro, and Katherine Renton, Seasonal variation in activity patterns of juve- nile Lilac-crowned Parrots in tropical dry for- est, 291-295 Sandpiper, Spotted, see Actitis macularius Upland, see Bartramia longicauda Sapsucker, Red-breasted, see Sphyrapicus ruber Saxicola dacotiae, 317-319 torquata, 318 Sayornis phoebe, 196-198 Schaefer, Cynthia L., see Small, Michael E, , John T. Baccus, and Jay A. Roberson Schulte, Shiloh A., see McGowan, Conor P, , and Theodore R. Simons Scincella lateralis, 100 Sciurus spp., 301 Scrub-Jay, Florida, see Aphelocoma coerulescens Scythrops spp., 375 Seiurus aurocapilla, 37, 327-335, 347 motacilla, 333 noveboracensis, 276, 279, 347 Selasphorus rufus, 279 Serinus citrinella, 392 serinus, 392 Setophaga ruticilla, 30, 37 sheep, see Ovis aries Shen, Sheng-Feng, see Yuan, Hsiao- Wei, , Kai- Yin Lin, and Pei-Fen Lee Shirley, Susan M., Habitat use by riparian and upland birds in old-growth coastal British Columbia rainforest, 245-257 shrew, see Sorex spp. Shrike, Loggerhead, see Lanins ludovicianus Northern, see Lanius excubitor shrike, see Corvinella spp. Sialia sialis, 100-101 Simons, Theodore R., see McGowan, Conor P, Shiloh A. Schulte, and Siskin, Pine, see Carduelis pinus Sis.son, D. Clay, see Terhune, Theron M.. , and H. Lee Stribling Sitta canadensis. 101-103, 270-279, 347, 400-402 Skagen, Su.san K., Amy A. Yackel Adams, and Rod D. Adams, Nest survival relative to patch size in a highly fragmented shortgrass prairie land- scape, 23-24 skink, ground, see Scincella lateralis skunk, see Mephitis spp. striped, see Mephitis mephitis Slaty-Flycatcher, C'rownetl, see Empidonomus auran- tioatrocristatus Small, Michael FI, Cynthia L. Schaefer, John T. Bac- 454 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 cus, and Jay A. Roberson, Breeding ecology of White-winged Doves in a recently colonized urban environment, 172-176 Smith, Kimberly G., see Barnhill, Rose Ann, Dora Weyer, W. Ford Young, , and Douglas A. James Smith, Mark D., Philip J. Barbour, L. Wes Burger, Jr., and Stephen J. Dinsmore, Density and diversity of overwintering birds in managed field borders in Mississippi, 258-269 snake, flat-headed, see Tantilla gracilis rat, see Elaphe obsoleta western hognose, see Heterodon nasicus Snetsinger, Thomas J., Christina M. Herrmann, Dawn E. Holmes, Christopher D. Hayward, and Stev- en G. Fancy, Breeding ecology of the Puaiohi {Myadestes palmeri), 72-84 Somateria mollissima, 46, 139 So rex spp., 100 Sparrow, American Tree, see Spizella arborea Baird’s, see Ammodramus bairdii Brewer’s, see Spizella breweri Cassin’s, see Aimophila cassinii Chipping, see Spizella passerina Field, see Spizella pusilla Fox, see Passerella iliaca Golden-crowned, see Zonotrichia atricapilla Grasshopper, see Ammodramus savannarum Henslow’s, see Ammodramus henslowii (Frontis- piece) House, see Passer domesticus Lark, see Chondestes grammacus Le Conte’s, see Ammodramus leconteii Lincoln’s, see Melospiza lincolnii Nelson’s Sharp-tailed, see Ammodramus nelsoni Olive, see Arremonops rufivirgatus Rufous-collared, see Zonotrichia capensis Savannah, see Passerculus sandwichensis Song, see Melospiza melodia Swamp, see Melospiza georgiana Vesper, see Pooecetes gramineus White-crowned, see Zonotrichia leucophrys White-throated, see Zonotrichia albicollis Sparrowhawk, see Accipiter nisus Eurasian, see Accipiter nisus species nova Polioptila clementsi, 113—127 Spermophilus tridecemlineatus, 24, 31 Sphyrapicus nuchalis, 101—103 ruber, 279 varius, 337 Spizella arborea, 273, 408 breweri, 279 passerina, 261, 264, 279, 347 pusilla, 261, 264, 265 Sprattus sprattus, 137 squirrel, see Sciurus spp. red, see Tamiasciurus hudsonicus thirteen-lined ground, see Spermophilus tridecem- lineatus St. Peters, Michelle A., see Zimmerman, Christian E., Nicola Hillgruber, Sean E. Burril, , and Jennifer D. Wetzel Starling, European, see Sturnus vulgaris Steatomis caripensis, 319 Sterna antillarum, 85-91 antillarum athalassos, 85 antillarum browni, 87 Stoehr, Andrew M., see Gilbert, William M., Paul M. Nolan, , and Geoffrey E. Hill Stonechat, Canary Island, see Saxicola dacotiae Common, see Saxicola torquata Storer, Robert W., The metazoan parasite fauna of grebes (Aves: Podicipediformes) and its rela- tionship to the birds’ biology, reviewed, 106- 107; The metazoan parasite fauna of loons (Aves: Gaviiformes), its relationship to the birds’ evolutionary history and biology, and a comparison with the parasite fauna of grebes, reviewed, 106-107 Stork, White, see Ciconia ciconia Wood, see Mycteria americana Storr, G. M., see Johnstone, R. E., and Stouffer, Philip C., see Bechtoldt, Catherine L., and Streptopelia decaocto, 175 Stribling, H. Lee, see Terhune, Theron M., D. Clay Sisson, and Stumella magna, 56—62 neglecta, 24, 57 Stumus vulgaris, 101, 239, 281, 287 Stutchbury, Bridget J. M., Bianca Capuano, and Gail S. Fraser, Avian frugivory on a gap-specialist, the red elderberry (Sambucus racemosa), 336- 340 Suiriri suiriri, 97 Sullivan, Brian L., see Condon, Anne M., Eric L. Kershner, , Douglass M. Cooper, and David K. Garcelon Sus scrofa, 316 Swallow, Bank, see Riparia riparia Bam, see Hirundo rustica Cliff, see Petrochelidon pyrrhonota Tree, see Tachycineta bicolor Swan, Mute, see Cygnus olor Tundra, see Cygnus columbianus swan, see Cygnus spp. swiftlet, see Aerodramus spp. and Collocalia spp. T Tachycineta bicolor, 281 Takekawa, John Y., see Miller, Michael R., , Joseph P. Fleskes, Dennis L. Orthmeyer, Mi- chael L. Casazza, David A. Haukos, and Wil- liam M. Perry Tamias sibiricus, 333 striatus, 327-335, 338 Tamiasciurus grahamensis, 271 Tanager, Hepatic, see Piranga flava Palm, see Thraupis palmarum Scarlet, see Piranga olivacea Western, see Piranga ludoviciana INDEX TO VOLUME 1 17 455 Tantilla gracilis, 100 Taxidea taxus, 24, 31 taxonomy of Polioptila guianensis complex, 113-127 Teal, Chestnut, see Anas castanea Common, see Anas crecca crecca Teel, Pete D., see Proudfoot, Glenn A., Jessica L. Use- ner, and Terhune, Theron M., D. Clay Sisson, and H. Lee Stri- bling. Above-ground nesting by Northern Bob- white, 315-316 Tern, California Least, see Sterna antillarum browni Interior Least, see Sterna antillarum athalassos Least, see Sterna antillarum Thill, Ronald E., see Alterman, Lynn E., James C. Bednarz, and Thraupis palmarus, 320 Thrush, Bicknell’s, see Catharus bicknelli (Frontis- piece) Creamy-bellied, see Turdus amaurochalinus Gray-cheeked, see Catharus minimus Hermit, see Catharus guttatus Pale-eyed, see Platycichla leucops Swainson’s, see Catharus ustulatus Varied, see Ixoreus naevius Wood, see Hylocichla mustelina Yellow-legged, see Platycichla flavipes thrush, see Cossypha spp. Tit, Bearded, see Panurus biarmicus Blue, see Parus caeruleus Great, see Parus major Varied, see Parus varius Touit huetii, 296-305 Towhee, Canyon, see Pipilo fuscus Eastern, see Pipilo erythrophthalmus Spotted, see Pipilo maculatus tragopan, see Tragopan spp. Tragopan spp., 316 Tringa hypoleucos, 406 Troglodytes aedon, 101, 185, 204-205 troglodytes. 245-257, 273, 274, 347, 348 Turdus amaurochalinus, 95, migratorius. 245-257, 263, 264, 272, 273, 337, 338 spp., 394, 398 Turkey, Wild, see Meleagris gallopavo turtle, map, see Graptemys ouachitensis Tyrannulet, Yellow-crowned, .see Tyrannulus elatus Tyrannulus elatus, 319-321 Tyrannus savana, 319, 321 vociferans, 377 Tyto alba, 177-184, 201 u, V Umbrellabird, Bare-necked, see Cephalopterus glabri- collis Unitt, Philip, San Diego County bird atlas, reviewed, 206-207 U.sener, Jessica L., see Proudfoot, Glenn A., , and Pete D. Teel Vanderpoel, John W., see William.son, Sheri, and Veery, see Catharus fuscescens Verdin, see Auriparus flaviceps Vermivora celata, 270-279 luciae, 378 peregrina, 37, 279, 347 ruficapilla, 347 virginiae, 378 Vetter, William E., see Roth, Timothy C., II, Steven L. Lima, and Vireo bellii, 375-381 gilvus, 257, 279, 377 huttoni, 253, 377, 378 olivaceus, 37, 95, 337, 338, 341-352 plumbeus, 375-381 solitarius, 347 Vireo, Bell’s, see Vireo bellii Blue-headed, see Vireo solitarius Hutton’s, see Vireo huttoni Plumbeous, see Vireo plumbeus Red-eyed, see Vireo olivaceus Warbling, see Vireo gilvus Vondrasek, Joanna R., Rolling prey and the acquisition of aerial foraging skills in Northern Mocking- birds, 313-315 Vulpes velox, 24, 31 w Wallace, George E., see Arendt, Wayne J., John Faa- borg, , and Orlando H. Garrido Warbler, Bay-breasted, see Dendroica castanea Black-and-white, see Mniotilta varia Black-throated Blue, see Dendroica caerulescens Black-throated Gray, see Dendroica nigrescens Black-throated Green, see Dendroica virens Blackburnian, see Dendroica fusca Blackpoll, see Dendroica striata Canada, see Wilsonia canadensis Cape May, see Dendroica tigrina Chestnut-sided, see Dendroica pensylvanica Dusky, see Phylloscopus fuscatus Grace’s, see Dendroica graciae Hooded, see Wilsonia citrina Lucy’s, .see Vermivora luciae Magnolia, see Dendroica magnolia Mourning, see Oporornis Philadelphia Orange-crowned, see Vermivora celata Prairie, see Dendroica discolor Swainson’s, .see Limnothlypis swainsonii Tennes.see, see Vermivora peregrina Town.send’s, .see Dendroica townsendi Virginia’s, see Vermivora virginiae Wilson’s, see Wilsonia pusilla Yellow, see Dendroica petechia Yellow-rumped, see Dendroica coronata Waterthrush, Louisiana, see Seiurus motacilla Northern, .see Seiurus noveboracensis Waxwing, Cedar, see Bombycilla cedrorum wea.sel, long-tailed, see Mustela frenata Wetzel, .Jennifer D., see Zimmerman, Christian E., Ni- cola Hillgruber, Sean E. Burril, Michelle A. St. Peters, and 456 THE WILSON BULLETIN • Vol. 117, No. 4, December 2005 Weyer, Dora, see Barnhill, Rose Ann, , W. Ford Young, Kimberly G. Smith, and Douglas A. James Wheatear, Northern, see Oenanthe oenanthe Whitney, Bret M., and Jose Alvarez Alonso, A new species of gnatcatcher from white-sand forests of northern Amazonian Peru with revision of the Polioptila guianensis complex, 113-127 Whittier, Joanna B., and David M. Leslie, Jr., Efficacy of using radio transmitters to monitor Least Tern chicks, 85-91 Whitworth, Terry, see Revels, Mia R., and Whooper, see Cygnus cygnus Wightman, Catherine S., and Mark R. Fuller, Spacing and physical habitat selection patterns of Per- egrine Falcons in central West Greenland, 226- 236 Williamson, Sheri, and John W Vanderpoel, Hum- mingbirds of North America, reviewed, 325- 326 Wilsonia canadensis, 333, 347 citrina, 328 pusilla, 270-279 Wood-Pewee, Western, see Contopus sordidulus Woodcreeper, Great Rufous, see Xiphocolaptes major Narrow-billed, see Lepidocolaptes angustirostris Woodpecker, Acorn, see Melanerpes formicivorus Black-backed, see Picoides arcticus Downy, see Picoides pubescens Hairy, see Picoides villosus Wren, House, see Troglodytes aedon Winter, see Troglodytes troglodytes Wunder, Michael B., see Dreitz, Victoria J., , and Fritz L. Knopf X, Y, Z Xiphocolaptes major, 97 Yamaguchi, Noriyuki, and Hiroyoshi Higuchi, Ex- tremely low nesting success and characteristics of life history traits in an insular population of Parus varius namiyei, 189—193 Yellowthroat, Common, see Geothlypis trichas Young, W. Ford, see Barnhill, Rose Ann, Dora Weyer, , Kimberly G. Smith, and Douglas A. James Yuan, Hsiao-Wei, Sheng-Feng Shen, Kai-Yin Lin, and Pei-Fen Lee, Group-size effects and parental investment strategies during incubation in joint-nesting Taiwan Yuhinas (Yuhina brunnei- ceps), 306-312 Yuhina brunneiceps, 306-312 Yuhina, Taiwan, see Yuhina brunneiceps Zenaida asiatica, 172-176 auriculata, 97 macroura, 243 Zimmerling, J. Ryan, and C. Davison Ankney, Varia- tion in incubation patterns of Red-winged Blackbirds nesting at lagoons and ponds in eastern Ontario, 280-290 Zimmerman, Christian E., Nicola Hillgruber, Sean E. Burril, Michelle A. St. Peters, and Jennifer D. Wetzel, Offshore marine observation of Willow Ptarmigan, including water landings, Kusko- kwim Bay, Alaska, 12-14 Zonotrichia albicollis, 261, 264, 279, 347, 348, 350 atricapilla, 270—279 capensis, 123 ^ leucophrys, 261, 264, 273, 274, 277 Zydelis, Ramunas, and Dainora Ruskyte, Winter for- aging of Long-tailed Ducks (Clangula hyema- lis) exploiting different benthic communities in the Baltic Sea, 133-141 JhWsonBulktin PUBLISHED BY THE WILSON ORNITHOLOGICAL SOCIETY VOLUME 117 2005 QUARTERLY EDITOR: EDITORIAL BOARD: REVIEW EDITOR: INDEX EDITOR: EDITORIAL ASSISTANTS: JAMES A. SEDGWICK KATHY G. BEAL CLAIT E. BRAUN RICHARD N. CONNER KARL E. MILLER MARY GUSTAI SON KATHY G BEAL M BETH DILLON ALISON R GOEEREDI CYNTHIA E MELCHER The Wilson Ornithological Society Founded December 3, 1888 Named after ALEXANDER WILSON, the first American Ornithologist President — Doris J. Watt, Dept, of Biology, Saint Mary’s College, Notre Dame, IN 46556, USA; e-mail: dwatt@saintmarys.edu First Vice-President — James D. Rising, Dept, of Zoology, Univ. of Toronto, Toronto, ON M5S 3G5, Canada; e-mail: rising@zoo.utoronto.ca Second Vice-President — E. Dale Kennedy, Biology Dept., Albion College, Albion, MI 49224, USA; e-mail: dkennedy@albion.edu Editor — James A. Sedgwick, US. Geological Survey, Fort Collins Science Center, 2150 Centre Ave., Bldg. C, Fort Collins, CO 80526, USA; e-mail: wilsonbulletin@usgs.gov Secretary — Sara R. Morris, Dept, of Biology, Canisius College, Buffalo, NY 14208, USA; e-mail: morriss@canisius.edu Treasurer — Melinda M. Clark, 52684 Highland Dr., South Bend, IN 46635, USA; e-mail: MClark@tcservices.biz Elected Council Members— Robert C. Beason, Mary Gustafson, and Timothy O’Connell (terms expire 2006); Mary Bomberger Brown, Robert L. Curry, and James R. Hill, III (terms expire 2007); Kathy G. Beal, Daniel Klem, Jr., and Douglas W. White (terms expire 2008). DATES OF ISSUE OF VOLUME 1 17 OF THE WILSON BULLETIN NO. 1 — 19 April 2005 NO. 2 — 21 June 2005 NO. 3 — 14 September 2005 NO. 4 — 15 December 2005 CONTENTS OF VOLUME 117 NUMBER 1 A PRACTICAL MODEL OF BICKNELL’S THRUSH DISTRIBUTION IN THE NORTHEASTERN UNITED STATES T. Daniel Lambert, Kent P. McFarland, Christopher C. Rimmer, Steven D. Faccio, and Jonathan L. Atwood OFFSHORE MARINE OBSERVATION OF WILLOW PTARMIGAN, INCLUDING WATER LAND- INGS, KUSKOKWIM BAY, ALASKA Christian E. Zimmerman, -—Nicola Hillgruber, Sean E. Burril, Michelle A. St. Peters, and Jennifer D. Wetzel MINIMUM POPULATION SIZE OF MOUNTAIN PLOVERS BREEDING IN WYOMING - — - Regan E. Plumb, Fritz L. Knopf, and Stanley H. Anderson NEST SURVIVAL RELATIVE TO PATCH SIZE IN A HIGHLY FRAGMENTED SHORTGRASS PRAIRIE LANDSCAPE — Susan K. Shagen, Amy A. Yackel Adams, and Rod D. Adams COMPARISON OF DAILY AVIAN MORTALITY CHARACTERISTICS AT TWO TELEVISION TOWERS IN WESTERN NEW YORK, 1970-1999 — — Arthur R. Clark, Colleen E. Bell, and Sara R. Morris A NEW MODEL TO ESTIMATE DAILY ENERGY EXPENDITURE FOR WINTERING WATERFOWL — — — Richard A. McKinney and Scott R. McWilliams APPARENT PREDATION BY CATTLE AT GRASSLAND BIRD NESTS - — — — — - famie L. Nack and Christine A. Ribic INFLUENCE OF FORAGING AND ROOSTING BEHAVIOR ON HOME-RANGE SIZE AND MOVE- MENT PATTERNS OF SAVANNAH SPARROWS WINTERING IN SOUTH TEXAS - — - — - - — Daniel L. Ginter and Martha J. Desmond BREEDING ECOLOGY OF THE PUAIOHI (MYADESTES PALMER!) Thomas J. Snetsinger, - — Christina M. Herrmann, Dawn E. Holmes, Christopher D. Hayward, and Steven G. Fancy EFFICACY OF USING RADIO TRANSMITTERS TO MONITOR LEAST TERN CHICKS — - — - — — - Joanna B. Whittier and David M. Leslie, Jr. USING CANOPY AND UNDERSTORY MIST NETS AND POINT COUNTS TO STUDY BIRD ASSEMBLAGES IN CHACO FORESTS Enrique J. Derlindati and Sandra M. Caziani SHORT COMMUNICATIONS EASTERN BLUEBIRD PROVISIONS NESTLINGS WITH FLAT-HEADED SNAKE - — — Shelby C. Braman and Darrell W. Pogue SAPSUCKERS USURP A NUTHATCH NEST. Christine A. Rothenbach and Christopher Opio THE NEST AND NESTLINGS OF THE WING-BANDED ANTBIRD {MYRMORNIS TORQUATA) FROM SOUTHERN GUYANA — — Nathan H. Rice and Christopher M. Milensky ORNITHOLOGICAL LITERATURE 1 12 15 23 35 44 56 63 72 85 92 100 101 103 106 NUMBER 2 A NEW SPECIES OF GNATCATCHER FROM WHITE-SAND FORESTS OF NORTHERN AMA- ZONIAN PERU WITH REVISION OF THE POLIOPTILA GUIANENSIS COMPLEX.. Bret M. Whitney and Jose Alvarez Alonso MOVEMENTS AND HOME RANGES OF MOUNTAIN PLOVERS RAISING BROODS IN THREE COLORADO LANDSCAPES Victoria J. Dreitz, Michael B. Wander, and Fritz L. Knopf WINTER FORAGING OF LONG-TAILED DUCKS {CLANGULA HYEMALIS) EXPLOITING DIF- FERENT BENTHIC COMMUNITIES IN THE BALTIC SEA — Ramunas Zydelis and Dainora Ruskyte BREEDING BIOLOGY OF JABIRUS {JABIRU MYCTERIA) IN BELIZE Rose Ann Barnhill, Dora Weyer, W Ford Young, Kimberly G. Smith, and Douglas A. James ABUNDANCE, HABITAT USE, AND MOVEMENTS OF BLUE-WINGED MACAWS {PRIMOLIUS MARACANA) AND OTHER PARROTS IN AND AROUND AN ATLANTIC FOREST RESERVE Beth E. I. Evans, Jane Ashley, and Stuart J. Marsden REPRODUCTIVE SUCCESS OF PIPING PLOVERS AT BIG QUILL LAKE, SASKATCHEWAN Wayne C. Harris, David C. Duncan, Renee J. Franken, Donald T McKinnon, and Heather A. Dundas BREEDING ECOLOGY OF WHITE-WINGED DOVES IN A RECENTLY COLONIZED URBAN ENVIRONMENT Michael F Small, Cynthia L. Schaefer, John T Baccus, and Jay A. Roberson SPOTLIGHT SURVEYS FOR GRASSLAND OWLS ON SAN CLEMENTE ISLAND, CALIFORNIA Anne M. Condon, Eric L. Kershner, Brian L. Sullivan, Douglass M. Cooper, and David K Garcelon FERRUGINOUS PYGMY-OWLS: A NEW HOST FOR PROTOCALLIPHORA SI ALIA AND HESPER- OCIMEX SONORENSIS IN ARIZONA Glenn A. Proudfoot, Jessica L. Usener, and Pete D. Teel EXTREMELY LOW NESTING SUCCESS AND CHARACTERISTICS OF LIFE HISTORY TRAITS IN AN INSULAR POPULATION OF PARUS VARIUS NAMIYEI Noriyuki Yamaguchi and Hiroyoshi Higuchi SHORT COMMUNICATIONS FIRST RECORD OF BRONZED COWBIRD PARASITISM ON THE GREAT-TAILED GRACKLE -Brian D. Peer, Stephen I. Rothstein, and James W Rivers A CAUSE OF MORTALITY FOR AERIAL INSECTIVORES? Muir D. Eaton and Daniel L. Hernandez FIRST RECORD OF SWAINSON’S WARBLER PARASITISM BY PROTOCALLIPHORA BLOW FLY LARVAE ..Mia R. Revels and Terry L. Whitworth FIRST RECORD OF EURASIAN JACKDAW (CORVUS MONEDULA) PARASITISM BY THE GREAT SPOTTED CUCKOO {CLAMATOR GLANDARIUS) IN ISRAEL Motti Charter, Amos Bouskila, Shaul Aviel, and Yossi Leshem HOUSE WREN PREYS ON INTRODUCED GECKO IN COSTA RICA Marco D. Barquero and Branko Hilje ORNITHOLOGICAL LITERATURE 113 128 133 142 154 165 172 177 185 189 194 196 199 201 204 206 NUMBER 3 HOME-RANGE SIZE, RESPONSE TO FIRE, AND HABITAT PREFERENCES OF WINTERING HENSLOW’S SPARROWS Catherine L. Bechtoldt and Philip C. Stauffer SPACING AND PHYSICAL HABITAT SELECTION PATTERNS OF PEREGRINE FALCONS IN CENTRAL WEST GREENLAND Catherine S. Wightman and Mark R. Fuller SURVIVAL AND CAUSES OF MORTALITY IN WINTERING SHARP-SHINNED HAWKS AND COOPER’S HAWKS Timothy C. Roth, II, Steven L. Lima, and William E. Vetter HABITAT USE BY RIPARIAN AND UPLAND BIRDS IN OLD-GROWTH COASTAL BRITISH COLUMBIA RAINFOREST Susan M. Shirley DENSITY AND DIVERSITY OF OVERWINTERING BIRDS IN MANAGED FIELD BORDERS IN MISSISSIPPI MarkD. Smith, Philip J. Barbour, L. Wes Burger, Jr, and Stephen J. Dinsmore COMPOSITION, ABUNDANCE, AND TIMING OF POST-BREEDING MIGRANT LANDBIRDS AT YAKUTAT, ALASKA Brad A. Andres, Brian T Browne, and Diana L. Brann VARIATION IN INCUBATION PATTERNS OF RED- WINGED BLACKBIRDS NESTING AT LAGOONS AND PONDS IN EASTERN ONTARIO J. Ryan Zimmerling and C. Davison Ankney SEASONAL VARIATION IN ACTIVITY PATTERNS OF JUVENILE LILAC-CROWNED PARROTS IN TROPICAL DRY FOREST Alejandro Salinas-Melgoza and Katherine Renton PARROT NESTING IN SOUTHEASTERN PERU: SEASONAL PATTERNS AND KEYSTONE TREES — Donald J. Brightsmith GROUP-SIZE EFFECTS AND PARENTAL INVESTMENT STRATEGIES DURING INCUBATION IN JOINT-NESTING TAIWAN YUHINAS {YUHINA BRUNNEICEPS) Hsiao- Wei Yuan, Sheng-Feng Shen, Kai-Yin Lin, and Pei-Fen Lee SHORT COMMUNICATIONS ROLLING PREY AND THE ACQUISITION OF AERIAL FORAGING SKILLS IN NORTHERN MOCKINGBIRDS Ioanna R. Vondrasek ABOVE-GROUND NESTING BY NORTHERN BOBWHITE Theron M. Terhune, D. Clay Sisson, and H. Lee Stribling DIVORCE IN THE CANARY ISLANDS STONECHAT {SAXICOLA DACOTIAE) Juan Carlos Illera REGURGITATED MISTLETOE SEEDS IN THE NEST OF THE YELLOW-CROWNED TYRAN- NULET {TYRANNULUS ELATUS) Peter A. Hosner ORNITHOLOGICAL LITERATURE 211 226 237 245 258 270 280 291 296 306 313 315 317 319 322 NUMBER 4 PREDATION AND VARIATION IN BREEDING HABITAT USE IN THE OVENBIRD, WITH SPECIAL REFERENCE TO BREEDING HABITAT SELECTION IN NORTHWESTERN PENNSYLVANIA ...Eugene S. Morton AVIAN FRUGIVORY ON A GAP-SPECIALIST, THE RED ELDERBERRY {SAMBUCUS RACEMOSA) Bridget J. M. Stutchbury, Bianca Capuano, and Gail S. Fraser BIRD COMMUNITIES AFTER BLOWDOWN IN A LATE-SUCCESSIONAL GREAT LAKES SPRUCE-FIR FOREST John M. Burris and Alan W. Haney USE OF GROUP-SELECTION AND SEED-TREE CUTS BY THREE EARLY-SUCCESSIONAL MIGRATORY SPECIES IN ARKANSAS - - - Lynn E. Alterman, James C. Bednarz, and Ronald E. Thill FLIGHT SPEEDS OF NORTHERN PINTAILS DURING MIGRATION DETERMINED USING SATELLITE TELEMETRY Michael R. Miller, John Y. Takekawa, Joseph P. Fleshes, Dennis L. Orthmeyer, Michael L. Casazza, David A. Haukos, and William M. Perry HOST USE BY SYMPATRIC COWBIRDS IN SOUTHEASTERN ARIZONA Jameson F Chace RESIGHTINGS OF MARKED AMERICAN OYSTERCATCHERS BANDED AS CHICKS Conor P McGowan, Shiloh A. Schulte, and Theodore R. Simons COMPARISON OF WOOD STORK FORAGING SUCCESS AND BEHAVIOR IN SELECTED TIDAL AND NON-TIDAL HABITATS F Chris Depkin, Laura K. Estep, A. Lawrence Bryan, Jr, Carol S. Eldridge, and I. Lehr Brisbin, Jr. SEXUALLY DIMORPHIC BODY PLUMAGE IN JUVENILE CROSSBILLS Pirn Edelaar Ron E. Phillips, and Peter Knops A DESCRIPTION OF THE NEST AND EGGS OF THE PALE-EYED THRUSH {PLATYCICHLA LEUCOPS), WITH NOTES ON INCUBATION BEHAVIOR Gustavo Adolfo Londoho SHORT COMMUNICATIONS INTERSPECIFIC NEST SHARING BY RED-BREASTED NUTHATCH AND MOUNTAIN chickadee Patrick A. Robinson, Andrea R. Norris, and Kathy Martin NELSON’S SHARP-TAILED SPARROW NEST PARASITIZED BY BROWN-HEADED COWBIRD Ted J. Nordhagen, Matthew P Nordhagen, and Paul Hendricks DUNKING BEHAVIOR IN AMERICAN CROWS Julie Morand-Ferron AN APPARENT CASE OF COOPERATIVE HUNTING IN IMMATURE NORTHERN SHRIKES Kevin C. Hannah A FIELD OBSERVATION OF THE HEAD-DOWN DISPLAY IN THE BRONZED COWBIRD Kimball L. Garrett and Kathy C. Molina FILIAL CANNIBALISM AT A HOUSE FINCH NEST William M. Gilbert, Paul M. Nolan, Andrew M. Stoehr, and Geoffrey E. Hill AN OBSERVATION OF FOLIAGE-BATHING BY AN ORANGE-BREASTED FALCON {FALCO DEIROLEUCUS) IN TIKAL, GUATEMALA Knut Eisermann BARE-NECKED UMBRELLABIRD {CEPHALOPTERUS GLABRICOLLIS) FORAGING AT AN UNUSUALLY LARGE ASSEMBLAGE OF ARMY ANT-FOLLOWING BIRDS Johel Chaves-Campos ORNITHOLOGICAL LITERATURE PROCEEDINGS OF THE EIGHTY-SIXTH ANNUAL MEETING REVIEWERS FOR VOLUME 1 17 INDEX TO VOLUME 1 17 CONTENTS OF VOLUME 1 17 327 336 341 353 364 375 382 386 390 394 400 403 405 407 410 413 415 418 421 428 442 444 ! 0 I o 3186 THE WILSON BULLETIN Editor JAMES A. SEDGWICK U.S. Geological Survey Fort Collins Science Center 2150 Centre Ave., Bldg. C. Fort Collins, CO 80256-8118, USA E-mail: wilsonbulletin@usgs.gov Editorial Assistants M. BETH DILLON ALISON R. GOFFREDI CYNTHIA P. MELCHER Editorial Board KATHY G. BEAL CLAIT E. BRAUN RICHARD N. CONNER KARL E. MILLER Review Editor MARY GUSTAFSON Texas Parks and Wildlife Dept. 2800 S. Bentsen Palm Dr. Mission, TX 78572, USA E-mail: WilsonBookReview@ aol.com Index Editor KATHY G. BEAL GUIDELINES FOR AUTHORS Consult the detailed “Guidelines for Authors” found on the Wilson Ornithological Society Web site (http://www.ummz.lsa.umich.edu/birds/wilsonbull.html). NOTICE OF CHANGE OF ADDRESS If your address changes, notify the Society immediately. Send your complete new address to Ornitho- logical Societies of North America, 5400 Bosque Blvd., Ste. 680, Waco, TX 76710. The permanent mailing address of the Wilson Ornithological Society is: % The Museum of Zoology The Univ. of Michigan, Ann Arbor, MI 48109. Persons having business with any of the officers may address them at their various addresses given on the inside of the front cover, and all matters pertaining to the Bulletin should be sent directly to the Editor. MEMBERSHIP INQUIRIES Membership inquiries should be sent to James L. Ingold, Dept, of Biological Sciences, Louisiana State Univ., Shreveport, LA 71 1 15; e-mail: jingold@pilot.lsus.edu CONTENTS PREDATION AND VARIATION IN BREEDING HABITAT USE IN THE OVENBIRD, WITH SPECIAL REFERENCE TO BREEDING HABITAT SELECTION IN NORTHWESTERN PENNSYLVANIA - .Eugene S. Morton AVIAN FRUGIVORY ON A GAP-SPECIALIST, THE RED ELDERBERRY (SAMBUCUS RACEMOSA) .Bridget J. M. Stutchbury, Bianca Capuano, and Gail S. Fraser BIRD COMMUNITIES AFTER BLOWDOWN IN A LATE-SUCCESSIONAL GREAT LAKES SPRUCE-FIR FOREST John M. Burris and Alan W. Haney USE OF GROUP-SELECTION AND SEED-TREE CUTS BY THREE EARLY-SUCCESSIONAL MIGRATORY SPECIES IN ARKANSAS Lynn E. Alterman, James C. Bednarz, and Ronald E. Thill FLIGHT SPEEDS OF NORTHERN PINTAILS DURING MIGRATION DETERMINED USING SATELLITE TELEMETRY ..i Michael R. Miller, John Y. Takekawa, Joseph R Fleskes, .Dennis L. Orthmeyer, Michael L. Casazza, David A. Haukos, and William M. Perry HOST USE BY SYMPATRIC COWBIRDS IN SOUTHEASTERN ARIZONA Jameson F. Chace RESIGHTINGS OF MARKED AMERICAN OYSTERCATCHERS BANDED AS CHICKS .Conor P. McGowan, Shiloh A. Schulte, and Theodore R. Simons COMPARISON OF WOOD STORK FORAGING SUCCESS AND BEHAVIOR IN SELECTED TIDAL AND NON-TIDAL HABITATS ... E Chris Depkin, Laura K. Estep, A. Lawrence Bryan, Jr., Carol S. Eldridge, and I. Lehr Brisbin, Jr. SEXUALLY DIMORPHIC BODY PLUMAGE IN JUVENILE CROSSBILLS Pirn Edelaar, Ron E. Phillips, and Peter Knops A DESCRIPTION OF THE NEST AND EGGS OF THE PALE-EYED THRUSH {PLATYCICHLA LEUCOPS), WITH NOTES ON INCUBATION BEHAVIOR Gustavo Adolfo Londoho SHORT COMMUNICATIONS INTERSPECIFIC NEST SHARING BY RED-BREASTED NUTHATCH AND MOUNTAIN CHICKADEE .Patrick A. Robinson, Andrea R. Norris, and Kathy Martin NELSON’S SHARP-TAILED SPARROW NEST PARASITIZED BY BROWN-HEADED COWBIRD Ted J. Nordhagen, Matthew P. Nordhagen, and Paul Hendricks DUNKING BEHAVIOR IN AMERICAN CROWS ...Julie Morand-Ferron AN APPARENT CASE OF COOPERATIVE HUNTING IN IMMATURE NORTHERN SHRIKES Kevin C. Hannah A FIELD OBSERVATION OF THE HEAD-DOWN DISPLAY IN THE BRONZED COWBIRD .... ...Kimball L. Garrett and Kathy C. Molina FILIAL CANNIBALISM AT A HOUSE FINCH NEST William M. Gilbert, Paul M. Nolan, Andrew M. Stoehr, and Geoffrey E. Hill AN OBSERVATION OF FOLIAGE-BATHING BY AN ORANGE-BREASTED FALCON {FALCO DEIROLEUCUS) IN TIKAL, GUATEMALA Knut Eisermann BARE-NECKED UMBRELLABIRD {CEPHALOPTERUS GLABRICOLLIS) FORAGING AT AN UNUSUALLY LARGE ASSEMBLAGE OF ARMY ANT-FOLLOWING BIRDS Johel Chaves-Campos ORNITHOLOGICAL LITERATURE PROCEEDINGS OF THE EIGHTY-SIXTH ANNUAL MEETING REVIEWERS FOR VOLUME 117 INDEX TO VOLUME 117 CONTENTS OF VOLUME 117