(ISSN The Journal of Raptor Research Volume 22 Winter 1988 Number 4 Contents Activity and Habitat Use by a Breeding Male Cooper’s Hawk in a SUBURBAN Area. Robert K. Murphy, Michael W. Gratson and Robert N. Rosenfield 97 Home Range and Dispersal of Great Gray Owls in Northeastern OREGON. Evelyn L. Bull, Mark G. Henjum and Ronald S. Rohweder 101 Nesting and Foraging Habitat of Great Gray Owls. Evelyn L. Bull, Mark G. Henjum and Ronald S. Rohweder . 107 Short Communications Male-biased Sex Ratio in Captive-bred Harris’ Hawks. Harvey D. Bradshaw, Jr. and Thomas D. Coulson 116 Eggs of the Orange-breasted Falcon ( Falco deiroleucus). Lloyd F. Kiff 117 Effect of Saline Added to Food on Weight Gain of Hand-raised Falcons. L. W. Oliphant 119 Osprey Preys on Tiger Salamander. Michael M. King 121 News and Reviews 121 Index to Raptor Research Reports No. 6 and Volumes 21 and 22 123 $ * * aft aft aft afc afe * $ # a|s # afe ## aft aft * $ Persons interested in predatory birds are invited to join The Raptor Research Foundation, Inc. Send requests for information concerning membership, subscriptions, special publications, or change of address to Jim Fitzpatrick, Treasurer, 12805 St. Croix Trail, Hastings, Minnesota 55033, U.S.A. The Journal of Raptor Research (ISSN 0892-1016) is published quarterly for $15.00 per year by The Raptor Research Foundation, Inc., 12805 St. Croix Trail, Hastings, Minnesota 55033, U.S.A. Application to mail at second class rate is pending at Hastings, Minnesota, and additional mailing office. Printed by Allen Press, Inc., Lawrence, Kansas, U.S.A. Copyright 1988 by The Raptor Research Foundation, Inc. Printed in U.S.A. THIS PUBLICATION IS PRINTED ON ACID-FREE PAPER. THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC. Vol. 22 Winter 1988 No. 4 /. Raptor Res. 22(4):97-100 © 1988 The Raptor Research Foundation, Inc. ACTIVITY AND HABITAT USE BY A BREEDING MALE COOPER’S HAWK IN A SUBURBAN AREA Robert K. Murphy, Michael W. Gratson and Robert N. Rosenfield Abstract. — In 1981, we monitored a radio-tagged breeding male Cooper’s Hawk ( Accipiter cooperii) in a central Wisconsin town during early nestling through post-fledging periods; about 150 hr of habitat use and activity data were collected. The hawk’s seasonal home range was 784 ha, and six daily home ranges averaged 231 ha. Wooded residential, residential/business, and open areas were avoided and oak- pine woods and shrub savannah habitats were preferred. The hawk spent 88% of its daylight (non-roost) time in 12% of its home range area; a 50 ha area about 0.7 km from the nest accounted for 54%, 61%, and 58%, respectively, of the hawk’s daylight time, roosts (N = 31 events), and monitored prey captures (N = 24). We also describe routine use of flight routes and suggest the importance of site familiarity to Cooper’s Hawks. Although the secretive nature of Accipiter hawks obstructs study of their activities and habitat needs (Fitch et al. 1946; Fischer 1986), such baseline data should prove useful to resource agencies charged with managing or assessing the status of the Cooper’s Hawk {Accipiter cooperii) in the eastern U.S., where the species is listed as threatened or endangered by several states. Recently, Fischer (1986) reported on activity and habitat use of breeding Accipiter hawks, including Cooper’s Hawks, in montane Utah. Al- though Cooper’s Hawks may nest in suburban or urban areas (Stahlecker and Beach 1979; Palmer 1988:329), almost nothing is known about their nest- ing ecology in such situations. Here we present base information on behavior of a suburban-nesting male Cooper’s Hawk. Study Area and Methods The nest, containing three young, was in a 4.5 ha oak {Quercus spp.) and white pine {Pinus strobus) woodlot in residential Plover (pop. 5500), Portage County, Wisconsin (Fig. 1). We defined “residential” as dwellings, mostly single family houses {x = 2/ha) and adjacent habitat with- in 50 m. Area within the hawk’s home range was composed of 37.3% residential (about Vi of which was wooded) and small businesses, 23.4% miscellaneous open areas (mainly transportation right-of-ways and small fields), 6.6% shrub savannah [fields reverted to grasses, forbs and shrub-stage jackpine ( P . banksiana) and black cherry {Prunus serotina)], 10.1% red pine (P. resinosa ) plantation, 19.3% oak-pine woods and 3.3% wooded riparian (mostly Salix spp., Alnus rugosa, and Acer rubrum) habitat. On 5 June 1981 we trapped the male (>2 yr old) in a mist net (3 x 10 m) placed near the nest (Hamerstrom 1963), attached a 4-g radio-transmitter package (150 mHz) to a central rectrix (Kenward 1978) and banded the hawk (USFWS lock-on band). The transmitter fell off on 20 June, so we recaptured the hawk on 24 June and attached a new transmitter (6 g, <1% of the hawk’s body weight) that functioned until late August, when the central rec- trices molted. We telemetrically located the hawk almost daily (including roost observations) through early August, using a vehicle-mounted Yagi antenna. On seven full-days (dawn to dusk) and 10 part-days (2-8 hr, x — 4 hr 20 min), we monitored the hawk continuously. We easily followed and often saw the hawk because of extensive road access throughout the study area; seldom were we >400 m from the hawk. We calculated home range by measuring the area within a polygon formed by a line connecting the outermost tele- metric or visual observations. The hawk’s seasonal home range thus encompassed all observations collected. Within the seasonal home range, we considered as available hab- itat all but the area added by a single, 1-km excursion outside the normal range of activity. We measured habitat area on an aerial photograph (1:7900) with a Numonics Graphics Calculator (Model 1224, Numonics Corpora- tion, 418 Pierce Street, Landsdale, PA 19446). From changes in radio signal direction and amplitude, we categorized the hawk as 1) active-hunting (AH: fre- quent movement, occasionally perching <10 min), or 2) inactive-perched (IP: stationary, without radio signal changes for >10 min) similar to Marquiss and Newton (1981) and based on duration of Cooper’s Hawk perching 97 98 Murphy et al. Vol. 22, No. 4 RESIDENTIAL/ BUSINESS - OPEN WOODED RESIDENTIAL MISC. OPEN AREAS 3 INE PLANTATION "l OAK-PINE WOODS WOODED RIPARIAN SHRUB SAVANNAH ★ NEST I » 1 0 1 km Figure 1. Habitats within the seasonal home range of a breeding male Cooper’s Hawk in Plover, Wis- consin, 1981 (excludes area added by a 1-km excursion outside the normal range of activ- ity). bouts in Fischer (1986); visual observations helped to con- firm these criteria. We calculated proportions of AH and IP time spent in each habitat during continuous monitor- ing (excluding prey deliveries and other visits to the nest) and compared to respective proportions of habitat available (Ivlev 1961). Habitat use could be assessed accurately only 78% of the time, because error polygons assigned to te- lemetry fixes sometimes were excessive (>2.5 ha, 17% of time), and we occasionally lost radio signal due to equip- ment failures or incorrect anticipation of the hawk’s move- ment (5% of time); we assumed these losses of data to be independent of the hawk’s use of habitats. Also, we did not completely observe all visits to the nest during contin- uous monitoring, but when visits included a steep descent into the nest woodlot and were of short duration, as those we verified as prey deliveries, we assumed that prey was delivered. Results and Discussion We collected 105 visual and 379 usable telemetric observations during 1 50 hr of continuous monitoring and 74 spot-checks, 6 June-26 August. During these months, the hawk covered a nearly elliptical range of 2.8 x 4.3 km, an area <8 km 2 . Late nestling and fledging period ranges were nearly 2 /i of the seasonal range, but ranges during day-long observations and other nesting periods were smaller (Table 1). Rel- atively small range sizes during the early nestling period and late summer may have been artifacts of lower sample size. Oak-pine woods and shrub savannah were pre- ferred habitats and residential/business and open areas were avoided during AH and IP time (Table 2). Cooper’s Hawks in Utah similarly preferred oak- maple woodland and oak shrubland/grassland and avoided open montane slopes, but individual use of habitats varied considerably and appeared unrelated Table 1. Home ranges (minimum perimeter polygon) of a breeding male Cooper’s Hawk in Plover, Wisconsin, 1981. Home Range Type Dates N HR (OBS) a Home Range Size (Ha) Seasonal 6 Jun-26 Aug 180 (484) 784 (Nesting stage) Early nestling 6-19 Jun 23 (33) 193 Late nestling 25 Jun- 5 Jul 53 (155) 451 Fledging 6-19 Jul 42 (145) 571 Post- fledging 20 Jul-3 Aug 42 (113) 274 Late summer X (SD) 4-26 Aug 20 (38) 229 344 (144) Daily b 1 Jul 16(55) 185 2 Jul 16(39) 283 17 Jul 16(60) 294 21 Jul 16 (41) 249 30 Jul 16(34) 177 X (SD) 6 Aug 15 (26) 194 230 (47) a Data from continuous monitoring and spot-checking were used to construct seasonal and nesting stage home ranges; observations (obs) were either visual or telemetric. b A daily home range for 1 1 June, also a full day, was not constructed because few (N = 9) usable telemetry fixes were obtained. to prey abundance (Fischer 1986). In this study wooded residential habitat also was avoided al- though used slightly. Pine plantation and wooded riparian were used in proportion to availability. The hawk disproportionately used areas within its home range. During 54.2% of combined AH and IP time (57.9% and 50.0%, respectively), the hawk was in a 50 ha area composed of oak-pine woods, shrub savannah, and pine plantation, 0.7 km east- southeast of the nest. Based on prey deliveries that we observed in their entirety (N = 24), 58.3% of prey captures apparently also occurred in this area, in addition to 61.3% of roosts (N = 31 events). Other areas that, collectively, accounted for 33.4% of the hawk’s daylight time* and 22.4% of roost locations were: 1) 20 ha of pine plantation, shrub savannah, and wooded residential about 0.4 km northeast of the nest, 2) 15 ha of oak-pine woods, shrub savan- nah, and pine plantation 1.4 km east- southeast of the nest and 3) 10 ha of oak-pine woods and wooded residential 0.3 km south of the nest. The hawk spent 87.6% of its total daylight time (excluding nest visits) Winter 1988 Suburban Cooper’s Hawk 99 Table 2. Habitat use, excluding nest visits and roosts, by a breeding male Cooper’s Hawk in a central Wisconsin town, 1981. Habitat Type Proportion (%) Within the Home Range 3 Active- Hunting Inactive-Perched Proportion (%) of Time (N = 2937 min) Electivity Index* 3 Proportion (%) of Time (N = 3193 min) Electivity Index* 3 Residential /business 26.1 0.1 -0.99 0.0 -1.00 Wooded residential 11.2 2.1 -0.68 2.0 -0.81 Miscellaneous open areas 23.4 0.3 -0.98 0.0 -1.00 Pine plantation 10.1 14.4 +0.18 17.1 +0.26 Oak-pine woods 19.3 57.8 +0.50 53.8 +0.47 Wooded riparian 3.3 5.9 +0.28 3.8 +0.07 Shrub savannah 6.6 19.4 +0.49 23.2 +0.56 •' Home range based on a minimum perimeter polygon including all observations except a single trip > 1 km from the normal range. b Electivity index (Ivlev 1961) = (a — b)/(a + b) where a = proportion of time spent in each habitat and b = proportion of each habitat within the home range; index values range from —1.00 (maximum avoidance) to +1.00 (maximum preference), with a value of 0 suggesting no selection. at the above four areas, which together composed about 12% of home range area. The hawk did not roost in habitats in proportion to their availability (N = 31 events, x 2 = 103.5, P < 0.001); most roosts were in pine plantation (61.3%) and oak-pine woods (32.2%). Pine plantations ap- pear to provide secure roost habitat for Wisconsin Cooper’s Hawks, just as they afford protection for nest sites (Rosenfield and Anderson 1983). Exclud- ing a roost at the nest, roosts occurred 120-1980 m (, x = 765, S.D. = 375) from the nest. Two routes were used for nearly all prey deliveries (N = 24) and subsequent nest departures (N = 26) observed in their entirety. On route A from wooded areas >0.5 km east of the nest, the hawk (carrying prey) ascended in circles, alternating flapping and soaring, to a height of 30-100 m, then maintained this altitude and flew over an oak- pine woodlot/ shrub savannah area 0.8 km southeast of the nest. The hawk then travelled directly northwest over houses and a small (6 ha) field, before stooping (45°) into the nest woods. A nest departure along route A followed an opposite sequence. On route B, the hawk departed from the nest (or delivered prey) by trav- elling in direct flight 1-12 m above a field south of the nest woods to (or from) an oak- pine woodlot 160 m south of the nest to perch temporarily (1-5 min) before flying within wooded habitat. Route A was used for 70.8% of prey deliveries but only 34.6% of nest departures, whereas route B was used for 12.5% of prey deliveries and 57.7% of nest departures. Al- though Accipiter hawks may sometimes forage high in the air (e.g., Clark 1977; Marquiss and Newton 1981), we believe high altitude flight was used for prey deliveries and (less often) nest departures, to avoid mobbing by passerines, which nearly always occurred at low-altitude (<30 m) flight over wood- land or open areas and to avoid a residential area that separated the nest from foraging habitat. Excluding prey deliveries and other nest visits, the hawk was within 1 km of the nest during 58.1% and 65.6% of AH and IP time, respectively, even though <5% of total time was spent at 0.26-0.50 km (Fig. 2), where little preferred habitat was available (Fig. 1). Including prey deliveries, the hawk spent 10.8% of total daylight time at the nest. We did not record Figure 2. Daylight (non-roost) time spent by a male Cooper’s Hawk at varying distances from its nest in Plover, Wisconsin, excluding prey de- liveries and other nest visits. 100 Murphy et al. Vol. 22, No. 4 the hawk >2 km from the nest during IP, and only 1% of AH time was spent >2 km away. The farthest distance from the nest recorded was 3.1 km, during a brief (45 min) excursion. Maximum distances trav- elled daily from the nest (mostly 1-2 km) coincide with the mean distance between nests (1.6 km) on a nearby (30 km) rural area (Meng and Rosenfield, in Palmer 1988:334). Prey delivery rate ranged from 0.38/hr in the late nestling period to 0.06/hr during post-fledging (x = 0.17; S.D. = 0.22). Kennedy and Johnson (1986) also found that prey delivery peaked during the late nestling period. Rates of 0.34-0.45/hr (both adults combined) were found at other Wisconsin Cooper’s Hawk nests (R. N. Rosenfield and J. Bielefeldt, pers. comm.). Cooper’s Hawk pairs in California deliv- ered up to 0.56 prey items (mostly lizards)/hr (Fitch et al. 1946); when young neared fledging, females began to deliver most prey. In our study the male spent 1-48 min (x = 9.8; S.D. = 10.9) at the nest during prey deliveries (N = 39). However, 51.3% of these visits lasted <5 min; the longest prey deliv- ery visits (33, 37 and 48 min) occurred during the early nestling period. Other nest visits (N = 7) lasted at least 20-310 min (x = 67; S.D. = 108), including two occasions when the hawk visited the nest im- mediately after leaving its roost in the morning. The hawk was AH about half of its daylight (non- roost) time. During early morning (roost departure- 091 5 H CDT), late morning (0916-1315 H), after- noon (1316-1715 H) and evening (1716 H until entering the roost), the hawk was AH 54.0%, 53.0%, 55.8%, and 49.4%, respectively, of the time. Breeding male Cooper’s Hawks in Utah are relatively inactive during early morning, perhaps because their main prey are inactive (Fischer 1986), while those in Cal- ifornia forage mainly in mid-morning and late after- noon (Fitch et al. 1946). In our study proportions of AH time during early morning to evening varied little during late nestling through post-fledging pe- riods (data during the early nestling period and late summer were too few for comparison), except that the hawk was more active (76.5% AH) in the evening during fledging. IP periods lasted up to 5 hr; rela- tively short (15-40 min) IP periods followed nest departures after prey deliveries, while longer ones occurred during steady rainfall. Routine use of the same areas and specific flight routes suggests the importance of site familiarity to Cooper’s Hawks and may explain in part the fidel- ity of males to nest areas over a number of years (R. N. Rosenfield and J. Bielefeldt, pers. comm.). Our study quantified aspects of a suburban envi- ronment that satisfied nesting needs of a Cooper’s Hawk; as suburban and urban areas increase, we urge researchers to further document such needs. Acknowledgments Field work was conducted under The Wisconsin Coo- per’s Hawk Study, with financial support mainly from the Wisconsin Department of Natural Resources and the U.S. Fish and Wildlife Service. We thank R. Anderson for guidance and J. Bielefeldt, D. Fischer, P. Kennedy, J. Smallwood, and B. Toland for helpful comments on drafts of the manuscript. Literature Cited Clark, R. J. 1977. Cooper’s Hawk hunting in the city. Auk 94:142-143. Fischer, D. L. 1986. Daily activity patterns and habitat use of coexisting Accipiter hawks in Utah. Ph.D. dis- sertation, Brigham Young Univ., Provo, UT. Fitch, H. S., B. Glading and V. House. 1946. Ob- servations on Cooper’s Hawk nesting and predation Calif. Fish Game 32:144-154. Hamerstrom, F. 1963. The use of Great Horned Owls in catching Marsh Hawks. Proc. Internat. Ornithol Congr. 13:866-869. Ivlev, V. S. 1961. Experimental ecology of the feeding of fishes. Yale Univ. Press, New Haven, CT. Kennedy, P. L. and D. R. Johnson. 1986. Prey-size selection in nesting male and female Cooper’s Hawks Wilson Bull. 98:110-115. Kenward, R. E. 1978. Radio transmitters tail-mounted on hawks. Orms Scandinavica 9:220-223. Marquiss, M. and I. Newton. 1981. A radio-tracking study of the ranging behavior and dispersion of Eu- ropean Sparrowhawks Accipiter msus. J. Anim. Ecol 51:111-113. Palmer, R. S. (Ed.) 1988. Handbook of North Amer- ican birds. Vol. 4, part 1 — diurnal raptors. Yale Univ Press, New Haven, CT. Rosenfield, R. N. and R. K. Anderson. 1983. Status of the Cooper’s Hawk. Unpubl. rep., Wis. Dep. Nat Resour., Madison, WI. Stahlecker, D. W. and W. Beach. 1979. Successful nesting by Cooper’s Hawks in an urban environment Ini. Bird Banding 51:56-57. College of Natural Resources, University of Wiscon- sin-Stevens Point, Stevens Point, WI 54481. Cur- rent address of first author: Lost wood National Wildlife Refuge, RR 2 Box 98, Kenmare, ND 58746. Current address of second author: Department of Biology, University of Victoria, Victoria, BC V8W 2R2. Received 24 March 1988; accepted 6 October 1988 /. Raptor Res. 22(4):101-106 © 1988 The Raptor Research Foundation, Inc. HOME RANGE AND DISPERSAL OF GREAT GRAY OWLS IN NORTHEASTERN OREGON Evelyn L. Bull, Mark G. Henjum and Ronald S. Rohweder 1 Abstract. — The average maximum distance radio-tagged adult Great Gray Owls (Strix nebulosa ) traveled from their nest sites was 13.4 km. Average size of home range was 67.3 km 2 . Maximum dispersal distance of juvenile Great Gray Owls from natal sites averaged 18.3 km, and home range averaged 139 km 2 . Three juvenile owls had an average home range of 1 67 km 2 their first year of life and 1 3 km 2 their second year of life. Over 90% of radio-tagged owls dispersed to areas with less snow during the winter. Great Gray Owls ( Strix nebulosa ) are uncommon throughout their range in North America and were considered rare in the United States until recent research revealed greater densities than anticipated (Nero 1980; Winter 1986; Franklin 1987; Forsman and Bryan 1987). Little is known of the movements of the species in North America, yet such information is essential for management. This paper reports on local movements, dispersal and home range of the Great Gray Owl. Study Area The study was conducted in three areas (called Spring, Bowman and Sheep) in northeastern Oregon. Spring study area (44 km 2 ) was located 17 km west of La Grande at 930-1140 m elevation; Bowman study area (27 km 2 ) was located 50 km west of La Grande at 1380-1500 m ele- vation; Sheep study area (78 km 2 ) was located 37 km southwest of La Grande at 1290-1500 m elevation. All study areas consisted of 60-70% conifer forest, with the remainder occurring as shallow-soiled grasslands, clearcuts and wet meadows. Of the mixed conifer forest, 60-80% had been selectively logged within the last 15 yrs, leaving some stands open and park-like. Isolated stands of unlogged, large trees (>50 cm dbh) occurred in each study area. Tree species included ponderosa pine ( Pinus ponderosa ), Douglas-fir ( Pseudotsuga menziesii) , grand fir (Abies grandis), lodgepole pine ( Pinus contorta ) and western larch ( Larix occidentalis ). Methods During 1982-1986, we located owls by hiking through study areas after dark in February, March, or April, im- itating the territorial call of male Great Gray Owls every 0 1 km. Areas where owls responded at night were searched during the day for nests. Attempts were made to trap birds once located. Adult Great Gray Owls were captured with a variety of traps including bal-chatris, noose poles and mist nets 1 Deceased. (see Bull 1987). Radio transmitters were attached to 10 males and 13 females and replaced each year when pos- sible. Observation periods of radio-tagged adults were 3 yrs for three owls, 2 yrs for seven owls, and 1 yr for 13 owls. We did not include data on seven radio-tagged birds because three died and four were located <10 times. Birds located <10 times had transmitters that malfunctioned We attached transmitters to 32 juvenile owls after fledg- ing. Observation periods of radio-tagged juveniles ranged from up to 1 yr (29 individuals)-2 yrs (3 individuals). We did not include data on 15 juveniles because 1 1 died within 6 mo and four were located <10 times. AVM transmitters (SMI, L Module) were used with a 30-cm wire antenna with heat-shrink tubing on the outside. A 22-g transmitter attached to a back-pack harness of 6-mm tubular teflon ribbon was positioned on an owl’s back. Transmitters lasted 242-505 d. A Telonics TR-2 receiver with a hand-held 2-element Yagi antenna was used for locations; transmitter range varied from 300 m- 15 km but was usually about 3 km. All radio-tagged adults nested each year. Nesting Great Gray Owls normally remained in the vicinity of their nest between March and July, so we determined movements from the nest area from August through February 1983- 1986. We have called these local movements because they are movements within a home range (Caughley 1977). Non-breeding owls (1- and 2-yr-old birds) were located all year, beginning the August after hatching. We have called these movements dispersal because they were move- ments away from natal sites. Caughley (1977) defines dispersal as the movement an animal makes from its point of origin to the place where it reproduces; we are using a slightly modified definition of dispersal because we do not know where the juveniles will reproduce. We located radio-tagged owls from the ground once every 2-3 wks. Owls we could not first find from the ground were located from a fixed wing airplane and later located from the ground. All locations were marked on aerial photos. During winter we also recorded snow depth where each bird was found. We determined maximum distance each bird traveled from its nest or natal site while radio-tagged. Home ranges encompassing movements of each owl were determined by constructing a minimum convex polygon that connected the outermost points of observation (Hayne 1949). Home range of adults included the area used while the bird was 101 102 Bull et al. Vol. 22, No. 4 Figure 1. Home range of three adult Great Gray Owls in Spring study area. A letter refers to a particular bird or pair and the nest used. Numbers preceding a letter refer to the years that bird was located or the year a nest (dot) was used (3 = 1983, 4 = 1984, 5 = 1985, and 6 = 1986). Number of locations = 38 for 5 A male, 72 for 3-5A female and 40 for 3-5B female. radio-tagged. Home range of juveniles defined only that area used within the first 1 or 2 yrs of life and included the natal area, where birds spent 3-4 mo after fledging. We used a <-Test to test for differences in maximum distance traveled and home range size between: 1) males (N = 5) vs. females (N = 8), 2) juveniles in Bowman/ Sheep (N = 3) vs. juveniles in Spring (N = 14), 3) adults in Bowman/Sheep (N = 3) vs. adults in Spring (N = 13), and 4) first-yr vs. second-yr of 3 juveniles from Spring. Birds from Bowman and Sheep areas were combined be- cause the two study areas were in close proximity, snow conditions were similar and sample sizes for each area were small. Significance was established when P < 0.05. Results Local Movements of Adult Owls. During 1983- 1986, maximum distance adults traveled from nest sites averaged 13.4 km (range = 2,4-43.2 km), and home range size averaged 67.3 km 2 (range = 4-312 km 2 ) (Fig. 1). No significant differences in maximum distance traveled from the nest (t = —0.99, df = 2.2, P = 0.43; t = —0.41, df = 7.0, P = 0.69) or in home range size (t = 0.20, df = 8.7, P = 0.85; t = 0.64, df = 10.6, P = 0.54) of adults were found between study areas or between sexes, respectively. Winter 1988 Great Gray Owl Home Range 103 0 1 MILE i l 0 1 2 KM Figure 2. Home range of six juvenile Great Gray Owls hatched in Spring study area and located from August 1985 until June 1986. A dot with a letter refers to a nest site. A letter with a number refers to the home range of each juvenile raised at the nest with the corresponding letter. Number of locations ranged from 12-21/ bird. During winter, 92% of birds from Spring and 83% of birds from Bowman and Sheep were located where snow depths were <40 cm. Spring had <50 cm of snow each winter, and six adults remained in that area for at least one winter. The seven adults that left Spring in the winter went to areas with a mean snow depth of 24 cm. None of the birds wintered at Bowman where snow depth was 70-100 cm. Birds Table 1. Yearly variation in maximum distance traveled (km) and home range size (km 2 ) of radio-tagged adult Great Gray Owls in northeastern Oregon. Bird N a 1983- 1984 1984- 1985 1985- 1986 Distance Area Distance Area Distance Area Female A 72 2.9 4 12.5 18 2.4 5 Female B 40 6.9 10 28.2 151 18.7 115 Female D 89 18.0 135 17.0 43 10.4 26 Female C 42 — — 8.2 27 6.7 16 Female H 27 — — 41.2 91 43.2 68 X 9.3 49.7 21.4 66 16.3 46 Male C 60 22.8 37 19.2 120 — — Male F 35 — — 1.6 2 2.4 2 Male G 38 — — 12.3 84 2.4 2 X — — 11.0 68.7 — — Number of locations. 104 Bull et al. Vol. 22, No 4 from August 1985 until June 1986. A dot with a letter refers to a nest site. A letter with a number refers to the home range of each juvenile raised at the nest with the corresponding letter. Number of locations ranged from 10-20/bird. from Bowman went to areas with shallower snow depths, except one female which was located for two winters in an area 43 km from Bowman with >150 cm of snow. Of eight adults followed two or more winters, six returned to the same area or even the same stand in more than one winter. However, considerable vari- ation occurred in local movements and home range size among birds (Fig. 1) and even between years for the same bird (Table 1). Pairs did not stay to- gether during non-breeding periods; however, pairs did return to the same area to nest. Dispersal of Juveniles. Maximum distance 17 juveniles traveled from natal sites in their first year averaged 18.5 km (range = 7.5-32 km), and home range size averaged 157 km 2 (range = 20-637 km 2 ). Juveniles from Bowman and Sheep areas dispersed significantly farther ( t = —3.69, df = 3.5, P = 0.03) than juveniles from Spring area (Figs. 2, 3). Mean dispersal distance for Bowman/Sheep and Spring were 29 and 16 km, respectively. Home range sizes were not significantly different ( t = — 1.5, df = 2.1, P = 0.27) between the two areas. All juveniles from Bowman and Sheep moved to areas with less snow. Twelve of 14 juveniles from Spring area spent most of their first winter 6-13 km to the southeast in an area characterized by open ponderosa pine stands. One juvenile spent the winter in Spring and another 6 km north of Spring in an area that was being logged; as logging operations moved location, the bird followed. Dispersal of 2-yr-old Birds. We followed two male and one female juveniles for 2 yrs. Although the difference was not significant ( t = 2.13, df = 2, P = 0.17), juveniles had a larger home range their first year (167 km 2 , range = 23-245 km 2 ), then Winter 1988 Great Gray Owl Home Range 105 Figure 4. Home range of a male juvenile Great Gray Owl during first and second year of life (August 1984-J une 1986) hatched in Bowman area at nest (dot) H; number of locations = 34. restricted their movements to a smaller area their second year (13 km 2 , range = 6-22 km 2 ) (Fig. 4). No juveniles were known to nest. Discussion Much greater movements have been reported for the Great Gray Owl than we observed. Nero and Copland (1981) captured an adult female in Canada that had been banded as an adult 3 yrs prior 223 miles (359 km) away. Nero (1981) found a dead juvenile 468 miles (753 km) from its natal site. Mik- kola (1981) in Finland reported the range of a female as 110 km, of a male as 22 km, of one juvenile as 20 km and of a second juvenile as 220 km. He found that in years with normal mouse populations, most birds spent the winter in breeding areas in Finland. In the Sierra Nevada in California Great Gray Owls moved to lower elevations in the winter (Winter 1986). Franklin (1987) observed elevational move- ments in Great Gray Owls in southeastern Idaho and northwestern Wyoming and theorized that when snow reached a certain depth, prey became unavail- able and owls moved to areas with shallower snow We think the relatively short distances we ob- served birds travel were a function of topography. Owls had to travel only a short distance to change elevation, snow depth and probable availability of prey. In contrast owls in Ontario, Manitoba and Minnesota must travel long distances to change el- evation or snow depth (R. W. Nero, pers. comm.). In winter all adult owls in Bowman, and all ju- venile owls in Bowman and Sheep (study areas with deepest snow), moved to areas with less snow. In contrast six of 13 adults remained in Spring (study area with least snow). Birds presumably left areas with deep snow which rendered small mammals un- available; nesting birds fed primarily on voles ( Mi - crotus spp. — 52% of diet) and Northern Pocket Go- phers ( Thomomys talpoides — 29% of diet) in northeastern Oregon (Bull et al., in press). However, 106 Bull et al. Vol. 22, No. 4 the fact that one female spent two winters in an area with >150 cm of snow suggests that at least some birds can survive in areas with deep snow. We were surprised to find a juvenile owl adjacent to active logging operations. Presumably, tree falling and soil disturbance displaced many small mammals which became easy prey. Both this juvenile and an adult female in another winter followed logging op- erations which moved to different stands. Our observations showed considerable variability in local movements, dispersal, and home range size among individuals and even between years for the same bird, suggesting that Great Gray Owls in Or- egon were not associated with a specific area year- round and were somewhat nomadic, versatile and opportunistic. Acknowledgments Funding was provided by the USDA Forest Service’s Pacific Northwest Research Station and Oregon Depart- ment of Fish and Wildlife Nongame Fund. Additional assistance was provided by Wallowa Valley and La Grande Ranger Stations. We are grateful to R. G. Anderson, H. A. Akenson, J. Akenson, S. Feltis, R. Goggans, R. A. Grove, J. S. Henderson, J. E. Hohmann, M. Hunter, M. D. Snider, M. E. Walker, and W. G. Williams. Literature Cited Bull, E. L. 1987. Capture techniques for owls. Pages 291-293. In R. W. Nero, R. J. Clark, R. J. Knapton and R. H. Hamre, Eds. Proceedings of biology and conservation of northern forest owls. USDA For. Serv. Gen. Tech. Rep. RM-142, USDA, Fort Collins, CO. , M. G. Henjum and R. S. Rohweder. In press Diet and optimal foraging of great gray owls. J. Wildl Manage. Caughley, G. 1977. Analysis of vertebrate populations John Wiley & Sons, New York. 234 pp. Forsman, E. D. and T. Bryan. 1987. Distribution, abundance, and habitat of great gray owls in south- central Oregon. Murrelet 68:45-49. Franklin, A. B. 1987. Breeding biology of the great gray owl in southeastern Idaho and northwestern Wy- oming. M.S. Thesis. Humboldt State Univ., Areata, CA. 83 pp. Hayne, D. W. 1949. Calculation of size of home range /. Mammal. 39:190-206. Mikkola, H. 1981. Der Bartkauz Strix nebulosa. Die Neue Brehm-Bucherei 538. A. Ziemsen Verlag. Wit- tenberg-Lutherstadt. 124 pp. Nero, R. W. 1980. The great gray owl — phantom of the northern forest. Smithsonian Inst. Press, Wash- ington, DC. 167 pp. . 1981. Manitoba’s beautiful and bold great gray owls. Can. Geographic April/May :40-43. , and H. W. R. Copland. 1981. High mortality of great gray owls in Manitoba — winter 1980-81. Blue Jay 39:158-165. Winter, J. 1986. Status, distribution and ecology of the great gray owl {Strix nebulosa) in California. M. S. Thesis. San Francisco State Univ., CA. 121 pp. USDA Forest Service, Forestry and Range Sciences Laboratory, La Grande, OR 97850. Address of sec- ond author: Oregon Department of Fish and Wild- life, La Grande, OR 97850. Received 22 February 1988; accepted 5 October 1988 /. Raptor Res. 22(4):107-1 15 © 1988 The Raptor Research Foundation, Inc. NESTING AND FORAGING HABITAT OF GREAT GRAY OWLS Evelyn L. Bull, Mark G. Henjum and Ronald S. Rohweder 1 Abstract. — During 1982-1986, 46 Great Gray Owl (Strix nebulosa ) nests were located in northeastern Oregon. Twenty-five of these nests were on stick platforms, 11 were on artificial platforms, and 10 were on broken-topped dead trees. Mean dbh and height of trees containing stick nests were 58 cm and 30 m, respectively, and the majority (76%) of nests were in live western larch ( Larix occidentalis). Broken-topped dead trees with nests averaged 78 cm dbh and 11m tall. Forest types in which nests were found included: Douglas-fir ( Pseudotsuga menziesii)- grand fir (Abies grandis) (50%); western larch-lodgepole pine (Pinus contorta) (29%); ponderosa pine (Pinus ponderosa)- Douglas-fir (15%); and ponderosa pine (7%). Nesting males foraged primarily in mature, open stands (11-59% canopy closure) of ponderosa pine or Douglas- fir. The Great Gray Owl (Strix nebulosa) is the largest strigiform found in North America and is an im- pressive owl of great interest to bird enthusiasts. This circumpolar species is widespread and occurs in bo- real forests from Alaska, east to Ontario, south to Idaho, western Montana, northwestern Wyoming, northern Utah, northern Minnesota, northern Wis- consin, and the Sierra Nevada in California; in Eurasia, this owl occurs in northern portions of Scandinavia, Russia and Siberia (American Orni- thologists’ Union 1983). Surprisingly little is known about the Great Gray Owl, making management difficult. To manage for the species, information on the habitat used for nest- ing and foraging is essential. If foraging habitat is lacking and prey densities are low, the owls will not nest even if nest sites are available. If prey is ade- quate and nest sites are lacking, again there will be no nesting. Because these owls depend on existing nest plat- forms such as old raptor nests, broken-topped dead trees, and artificial platforms (Nero 1980; Mikkola 1983; Winter 1986; Bull et al. 1987; Franklin 1987; Forsman and Bryan 1987), managers have a good opportunity to manage the species by providing nest platforms where they want the owls — provided there is adequate prey and habitat to support them. It is therefore essential to know what habitats are suitable for nesting and foraging. Our objectives were to determine habitat used for nesting and foraging of Great Gray Owls during the breeding season in northeastern Oregon. Nesting habitat included the nest tree and the area surround- ing the tree, in addition to the habitat used by ju- 1 Deceased. veniles after fledging who were still dependent on the adults. Foraging habitat included areas used by males who were feeding females and offspring. Study Area During March-May 1982 we surveyed for Great Gray Owls in 2 large areas: the area within a 60-km radius around La Grande, Oregon and a 50 km 2 area 47 km north of Enterprise, Oregon. During 1983-1986 survey efforts were confined to 4 areas where Great Gray Owls were located in 1982 — the Spring, Bowman, Sheep and Thomason study areas. Forest types in each area were categorized using a mod- ification of Burr’s (1960) classification by tree species in the dominant and codominant crown classes. Dominant trees were defined as those with crowns extending above the general level of the crown, and codominant trees were those whose crowns formed the general level of the crown (Smith 1962:33). Each of the 4 study areas contained 4 different forest types: 1) ponderosa pine (Pinus ponderosa), 2) ponderosa pine-Douglas-fir (Pseudotsuga menziesii), 3) Douglas-fir-grand fir (Abies grandis), and 4) western larch (Larix occidentalis)-\o&ge,po\t pine (Pinus contorta). Successional stages in each area were classified based on tree size and stand structure as subclimax, mature, over-mature and remnant. In subclimax stands all trees were <30 cm dbh; in mature stands the largest trees were 30-50 cm dbh; over-mature stands were unlogged and larger trees were >50 cm dbh; remnant stands were typ- ically logged and had 1-3 trees/ha >50 cm with the re- mainder of trees <30 cm. The remnant stage identified stands that did not resemble unlogged over-mature stands but contained a few large-diameter trees. The Spring study area (44 km 2 ) was 17 km west of La Grande at 930-1140 m elevation. Cover types included conifer forest (63% of area), shallow-soiled grasslands (32%) and clearcuts (5%). During the previous 10 yrs, 66% of forested stands within the Spring study area had been selectively logged. As a result most forests in this area consisted of open, park-like stands dominated by ponder- osa pine. These stands were on deep soils with a dense cover of grasses. Isolated stands of unlogged, large trees (>50 cm dbh) comprising 22% of this study area remained Isolated stands contained Douglas-fir, lodgepole pine, 107 108 Bull et al. Vol. 22, No. 4 Table 1. Characteristics of 3 types of Great Gray Owl nest structures at 46 nest sites in northeastern Oregon, 1982- 1986. Nest Structure Characteristic Stick Broken-topped Tree Wooden Platform No. nests in Spring 16 1 4 No. nests in Bowman 3 2 2 No. nests in Sheep 5 1 — No. nests in Thomason 1 6 5 Nest tree species Western larch 76% 10% 45% Douglas-fir 20% 20% Ponderosa pine 4% 70% 36% Lodgepole pine — — 18% X S.D. X S.D. X S.D. Nest height (m) 17 5.05 11 3.88 12 3.01 Tree dbh (cm) 58 17.16 78 15.24 58 17.20 Tree height (m) 30 4.98 11 3.65 29 8.73 Bole height (m) 10 5.00 8 4.24 13 6.59 Tree age 151 35.07 173 25.40 129 51.73 western larch, and occasionally grand fir. A total of 52 artificial nest platforms were erected in 1984 in the Spring area. Bowman (27 km 2 ) was 50 km west of La Grande at 1380-1500 m elevation. Cover types included coniferous forest (68%), shallow-soiled grasslands (20%) and clear- cuts (12%). Dense stands of lodgepole pine or mature and over-mature stands of grand fir and Douglas-fir with some western larch and ponderosa pine dominated the Bowman area. About 60% of the forested area had been logged in the 15 yrs prior to our study; lodgepole pine stands had been clearcut, and ponderosa pine and Douglas-fir stands had been selectively logged. Fifty-four artificial nest plat- forms were erected in this area in 1984. Sheep (78 km 2 ) was 37 km southwest of La Grande at 1290-1500 m elevation. Cover types included coniferous forest (68%), clearcuts (12%), wet meadows along streams (12%) and shallow-soiled grasslands on ridges (8%). Pon- derosa pine forests occurred on south-facing slopes, and lodgepole pine stands or mixed stands of Douglas-fir, west- ern larch and grand fir occurred on north-facing slopes. Greater than 80% of the forested area had been logged (40% clearcut and 60% selectively logged) during the 15 yrs prior to this study. Thomason (34 km 2 ) was 47 km north of Enterprise at 1350-1470 m elevation. Cover types included coniferous forest (71%) and wet meadows (29%). Forest stands were lodgepole pine and ponderosa pine or mixed stands of Douglas-fir, western larch and grand fir. About 80% of the area had been selectively logged in the 10 yrs prior to this study. There were 38 artificial nest platforms in Thomason at the onset of this study. Methods Locating Birds and Nests. Owls were located after dark in February, March and April by imitating the ter- ritorial call of a male Great Gray Owl every 0.1 km while walking through each study area. Areas containing owls were searched for active nests during the day. Radio Telemetry. Adult Great Gray Owls were cap- tured with bal-chatri traps, noose poles and mist nets (Bull 1987). Radio transmitters (AVM Instrument Co. — SMI, L Module) were placed on 10 males and 13 females and 35 post-fledging juveniles. Transmitters were attached to the bird with a back-pack harness of 6 mm tubular teflon ribbon. The entire package weighed 25 g and lasted 242- 505 d. A Telonics TR-2 receiver with a hand-held 2- element Yagi antenna was used for locating owls. Adult radio-tagged owls were located each spring at their nests. Juveniles were located every 1-3 d for 7 d after fledging. Eight nesting males were followed in the morning (first light until roosting) and evening (departure from roost until dark) 1-2 times/wk from the time trans- mitters were put on until 2 mo after fledging, or until the radio failed or the nest was abandoned. Habitat Quantification. Variables recorded at nests included nest type (stick, broken-topped dead tree, or ar- tificial platform), nest height (m), tree species, dbh (cm), height (m), age (increment bore used), and bole height (height of lowest live branch) (m) (Table 1). Stick nests were classified as natural platforms created by dwarf mis- tletoe ( Arceuthobium spp.) or as vacated nests built by Northern Goshawks ( Accipiter gentilis ) or Red-tailed Hawks (Buteo jamaicensis) . At 4 sites we saw hawks con- Winter 1988 Great Gray Owl Habitat 109 Table 2. Habitat characteristics in circular 0.1 -ha plots centered on 46 Great Gray Owl nests in north- eastern Oregon, 1982-1986. Characteristic X S.D. Fre- quency Forest type Douglas-fir-grand fir 50 Lodgepole pine-western larch 29 Ponderosa pine-Douglas-fir 15 Ponderosa pine 7 Successional stage Mature 26 Over-mature 41 Remnant 33 Logging None 72 Partial cut 19 Adjacent to clearcut 9 Canopy closure (%) 0-10 7 11-59 30 >60 63 Live trees/0.1 ha 2:50 cm dbh 3.2 2.51 Dead trees/0.1 ha >50 cm dbh 1.0 2.10 Live trees/0.1 ha <50 cm dbh 26.7 14.70 Dead trees/0.1 ha <50 cm dbh 9.2 7.80 Leaning trees/0.1 ha <10 cm dbh 5.1 14.45 Regeneration (trees/0.1 ha) 41.8 55.47 Distance to water (m) 231.6 209.98 Distance to clearing (m) 77.1 70.13 structing nests in prior years; at the remainder, a nest below the canopy in a dense forested stand was classified as an old Goshawk nest, and a nest high in the canopy of a more open forest was classified as an old Red-tailed Hawk nest. In a circular 0.1 -ha plot centered on each nest, we recorded the variables listed in Table 2. Regeneration included all trees <10 cm dbh. We also recorded landform (flat, draw, or slope), slope aspect and gradient, number of canopy layers and height (m) of tallest canopy. With aerial photos (scale 1:24 000) and a planimeter, we de- termined the percent area in forest, grassland, clearcut and selectively logged forest within a 500-m radius of each nest. The linear distance in edge between forest and grass- land within the 500-m radius was calculated with a map measure. Edge was defined as a 60-m wide band where forests and openings met. Juvenile owls were located every 1-3 d during the week after fledging. Each time a juvenile owl was located, we recorded type of perch used (branch, leaning tree, or top of a broken-off dead tree) and perch height. Tree species, condition (live or dead), dbh, and height of the tree used for perching were measured. In addition we noted the presence of leaning trees that provided owlets access to perches in upright trees. For the next 2 mo, juveniles were located every 1-2 wks and locations recorded on aerial photographs. While following radio-tagged males, activity and habitat use data were recorded at 15-min intervals and each time an owl hit the ground when pursuing prey (hereafter referred to as a foraging site). Activity categories were hunting or roosting. Birds actively searching for prey, flying from perch to perch, and staring intently at the ground were classified as hunting. Birds quietly perched in a tree next to the trunk and not watching the ground intently were classified as roosting. Every 15 min we recorded location of the bird on an aerial photo, estimated canopy closure over the bird and recorded forest type, successional stage, physiognomy of the stand (open or dense forest or edge), logging activity, number of stand layers, type of perch and tree species supporting perch. If a bird was roosting when first located, we recorded the data once and waited until the bird left the roost before continuing. At each foraging site we recorded percent, height and type of ground cover within a 1-m radius, presence or absence of downed wood within a 1-m radius, diameter (at largest point) of the downed wood, distance owl flew to prey, height of perch, diameter of perch tree and distance to nest. Home range of hunting males was delineated by connecting the outermost radio locations to form minimum convex polygons which were then measured with a pla- nimeter. LANDS AT data (Isaacson et al. 1982) were used to determine forest canopy closure classes (0-10%, 11-59% and >60%) available in 3 of the study areas and in the home range of 5 of the 8 males. The 0-10% class comprised openings; the 11-59% class contained relatively open stands, many of which had been selectively logged; the >60% class was primarily unlogged, overmature forest stands. Density. We calculated density of active nests of Great Gray Owls in Spring and Thomason by counting the number of nests within a polygon defined by the outermost nests in 1984. We chose 1984 because we believe all nesting pairs within the polygons were located that year. We did not present the density as number of nests/study area because we believe all nests in the study areas were not found. Analysis. Chi-square analyses were used to compare the observed number of foraging locations in each canopy closure class and in edge with the expected number of locations based on the percent edge and canopy closure classes in the home range of each radio-tagged male. We compared habitat characteristics of hunting birds in Spring with those in Bowman and Sheep using a Chi-square analysis. Habitat used by 3 birds studied in Sheep and Bowman were combined because of the small sample size and because the 2 areas had similar habitat and logging activity. We used P < 0.05 as the level of significance. We could not test for preference for nest type or nest habitat because we did not determine the number or distribution of available nest sites. 110 Bull et al. Vol. 22, No, 4 Results Nest Sites. During 1982-1986, we located 46 nests, 14 of which were used more than once (Table 1). Of the 14 nests used more than once, 6 were used 2 years, 6 were used 3 years, 1 was used 4 years, and 1 was used twice in the same year, so we ob- served 69 nesting attempts on 46 nest structures. Fifty-four pecent of the nests were stick platforms, 24% were artificial platforms and 22% were natural depressions on broken-topped dead trees (Table 1). Of the stick nests, 68% were originally made by Northern Goshawks, 12% were made by Red-tailed Hawks and 20% were natural platforms created by dwarf mistletoe infections. All 3 types of nests were commonly used, although nests in broken-topped trees and wooden platforms had a lower rate of nest failure (20%) than did nests in stick platforms (34%), suggesting that the latter was a less stable structure because young or eggs fell through on at least 4 occasions. The majority of stick nests were in large diameter (>50 cm dbh) live western larch (Table 1). The majority of nests in broken-topped dead trees were in large diameter ponderosa pine at least 7 m tall. Nests in wooden platforms were at least 9 m above the ground in live trees. The mean size of 11 stick nests was 74 cm (SD = 17.32) long, 65 cm (S.D. = 11.97) wide, 27 cm (S.D. = 14.04) high, with a depression 7 cm (S.D. = 2.70) deep. The only nest on a broken-topped dead tree that was measured had a circular depres- sion in the top of the tree that was 56 cm in diameter and was 26 cm deep. The majority of the nests occurred in Douglas- fir-grand fir forest types and in over-mature and remnant stands (Table 2). Sixty-nine percent of nests occurred on slopes, 22% on flat ground, and 9% in draws; mean slope gradient at nests was 13% (S.D. = 9.28). Sixty-five percent of nests were on north- facing slopes. Northern aspects are preferred by Northern Goshawks (Reynolds et al. 1982), the pri- mary builder of nests used by Great Gray Owls. Western larch comprised the dominant crown class at 52% of nest sites, ponderosa pine 28%, and Doug- las-fir and grand fir the remainder. Ponderosa pine comprised the dominant crown class at nests in Thomason, and western larch comprised the dom- inant crown class in the other study areas. The co- dominant crown class was comprised of lodgepole pine at 51% of the nests, Douglas-fir at 31% and ponderosa pine at 18%. Seventy-two percent of nest sites had not been logged, but 60-80% of stands in each study area had been logged. Forty-four (96%) of 46 nest sites had > 2 canopy layers, the tallest layer having a mean height of 34 m (S.D. = 4.90). Density of live trees < 50 cm dbh at nest sites ranged from 5-64 stems/ 0.1 ha, and of live trees > 50 cm dbh ranged from 0-10 stems/0.1 ha. Density of dead trees ranged from 0-36 stems/0.1 ha at nest sites. Regeneration ranged from 0-290 stems/0.1 ha. Area in forest within a 500-m radius of each nest ranged from 52-99%, and forested area that had been logged ranged from 0-97%. The amount of edge between forests and openings within 500 m of the nest averaged 4.2 km (range = 0.7-8. 3 km). The amount of area in natural openings within 500 m of the nest ranged from 0-40%. Nests in Thomason contained the greatest amount of natural opening (£ = 25%), and nests in the other 3 study areas con- tained 13-15%. Bowman contained the greatest amount of clearcut area (13%) within 500 m of nests; nests in the other 3 areas contained <6%. Total area in openings (natural and clearcut combined) ranged from 18-26%. Nest Site Fidelity. We observed 18 nesting at- tempts by 9 pairs where at least 1 member of each pair was radio-tagged. Of the 18 nesting attempts, 39% were on the same nest the next year, 39% were within 1 km of the nest used the previous year, and 22% were farther than 1 km away from the nest used the previous year. Average distance between alternate nests was 1.3 km (range = 0.2-4. 5 km, Fig. 1). In 4 cases in which a bird or a pair moved farther than 1 km from their previous year’s nest, we found previous nest sites occupied by new pairs. Density. Shortest distance between 2 active nests was 430 m; 2 other nests were 460 m apart. In 1984 the minimum density of owls was 7 pairs/9.4 km 2 (entire study area was 44 km 2 ) at Spring and was 5 pairs/2.9 km 2 (entire study area was 34 km 2 ) at Thomason. At Spring, 2 different females used the same nest in 1984 and were counted as 2 pairs. Perches Used by Juveniles. Owlets left the nest before they could fly but were capable climbers, using talons, bills and wings to claw and flap their way up tree trunks. For the first few days, leaning trees with bark were easiest for the young to climb. After several days, juveniles could climb up some vertical trees, particularly those with branches or deeply fissured bark (characteristic of large-diameter trees). As owlets aged, they perched higher in the Winter 1988 Great Gray Owl Habitat 111 Figure 1. Locations of nests of radio-tagged Great Gray Owls in Spring area 1982-1986. Lines connect nests used in successive years by the same bird. canopy. Perches used the first week after the young left the nest averaged 6.2 m (S.D. = 4.13) above the ground, had an average canopy closure of 50% (S.D. = 22.16) and were all within 200 m of the nest. Of 116 perches used by juveniles, 67% were lean- ing trees or trees which could be reached by climbing a leaning tree; the remainder were branches or bro- ken-topped trees. Leaning perch trees were typically small- diameter (x = 16 cm, S.D. = 7.82) lodgepole or ponderosa pine, with an average of 87% (S.D. = 23.80) of the bark remaining. Branches used as perches were typically in live ponderosa pine or Douglas-fir trees with a mean dbh of 37 cm (S.D. = 20.10). After leaving the nest, juveniles typically moved toward dense forest cover (if the nest was not in a dense stand). Within 2 wks after fledging juveniles gradually became more mobile but generally stayed within forest stands with >60% canopy closure (Fig. 2). Family group G ranged the farthest and roosted less frequently in stands with dense canopies than did other family groups (Fig, 2). Foraging Habitat. During 229 hrs of radio- tracking 8 male Great Gray Owls, we recorded 223 foraging sites and 622 hunting locations at 15-min intervals. Males usually hunted in open forested stands from perches close to the ground. Hunting perches averaged 5.5 m (S.D. = 6.65) high and were in trees with mean dbh of 27 cm (S.D. = 14.06). Mean distance males flew from perches to prey was 10.5 m (S.D. = 9.39). Vegetative ground cover at foraging sites averaged 88% with an average plant 112 Bull et al. Vol. 22, No. 4 Figure 2. Location of nests and perches used by juveniles of 4 Great Gray Owl family groups in Spring study area. Juveniles were located during 2 mo after fledging. Family groups A and B nested in 1983, and family groups G and D nested in 1985. height of 21 cm. Grasses dominated in 96% of the sites. Downed wood with a mean diameter of 20 cm was present within 1 m in 77% of the sites. Mean distance the 8 males moved from the nest when hunting was 0.62 km. One male foraged no further than 0.7 km from his nest, whereas the great- est distance foraged by a male was 3.2 km. Home range of 5 males with ^ 90 foraging locations av- eraged 4.5 km 2 (range = 1.3-6. 5 km 2 ). There was a significant difference in canopy clo- sure of stands used for foraging by 5 males compared to expected use based on availability (x 2 values for 5 males: 48.1, 41.1, 37.3, 109.8, 58.4; 2 df , P < 0.01). Males preferentially foraged in stands with 11-59% canopy closure and avoided clearings. Four of the males avoided stands with >60% canopy closure, while 1 male used such stands in proportion to their occurrence. Use of edge was significantly greater ( P < 0.05) than expected with 2 males, less than expected with 2 males, and not different than expected with 1 male. There were significant differences between 5 for- aging males at Spring and 3 at Sheep and Bowman in all habitat variables measured except canopy clo- sure (Table 3). Males at Spring hunted more often in stands that were open, logged, younger, with 1- 2 canopy layers and containing more ponderosa pine than did males at Sheep and Bowman (Fig. 3). Males Winter 1988 Great Gray Owl Habitat 113 at Sheep and Bowman hunted more often in stands that were unlogged, older, with 2-3 canopy layers and containing more Douglas-fir and lodgepole pine. Males roosted during the day in stands with 11- 59% canopy closure (71 %) and stands with 60% or more canopy closure (29%). Eighty-three percent of 62 roost sites were in mature or older stands with 2 or more canopy layers. Sixty-eight percent of roosts were in unlogged stands. Owls roosted at least 7 m above the ground 56% of the time, 3-6 m above the ground 38% of the time and lower than 3 m 6% of the time. Discussion Great Gray Owls are versatile in their use of nest structures and readily use artificial nests. In Finland Mikkola (1981) observed the species using nests on branches, on stumps, on the ground, on a cliff and on a barn. Great Gray Owl use of artificial nest structures has been reported by Nero et al. (1974), Nero (1982) and Helo (1984) and provides oppor- tunities for management. Owls may prefer artificial structures over natural platforms; 3 females in our study nested on platforms even though stick nests were available nearby. Great Gray Owls are flexible in their use of hab- itats as well. Nero (1980) and Servos (1986) found Great Gray Owl nests in poplar ( Populus spp.) and tamarack ( Larix larcinia) trees adjacent to muskeg in Canada. Winter (1986) found nests on dead trees in conifer forests only within 260 m of meadows in California. Harris (1984) described nests in forests of tamarack and black spruce ( Picea mariana ) in Canada, and Mikkola (1981) reported nests in dense spruce and pine forests, deciduous stands, wet spruce moors, and swamps in Finland and Sweden. Mik- kola (1981) suggested that the owls preferred edges of older stands rather than the interior of large, dense forests. In Oregon we found Great Gray Owl nests in all forest types available within the study areas; however, the majority of nests were in over-mature or remnant stands of Douglas-fir and grand fir forest types on north-facing slopes. Although the majority of each study area had been logged within 15 yrs of our study, 72% of nests occurred in unlogged stands. Either owls preferred unlogged stands or there was a disproportionate number of potential nest sites in stands, as logging activities often remove large-diameter live and dead trees that could support nests. Leaning trees and dense cover near nests are im- Table 3. Foraging site characteristics of 8 nesting male Great Gray Owls in northeastern Oregon, 1985 (data in percent). Sheep/ Spring Bowman 3 Characteristic (N = 357) (N = 265) Forest type (x 2 = 264.2, 3 df, P < 0.01) Ponderosa pine 62 3 Ponderosa pine-Douglas-fir 25 5 Douglas-fir-grand fir 11 60 Lodgepole pine-western larch 2 32 Successional stage (x 2 = 12.1, 3 df, P < 0.01) Subclimax 23 17 Mature 61 58 Over-mature 6 6 Remnant 10 19 Physiognomy of stand (x 2 = 82.6, 2 df, P < 0.01) Open forest 84 51 Edge 14 30 Dense forest 2 19 Logging (x 2 = 54.2, 2 df ,P< 0.01) Unlogged 25 49 Partial cut 74 46 Clearcut 1 5 No. stand layers (x 2 = 130.6, 2 df, P < 0.01) 1 46 13 2 52 54 3 2 33 Perch location (x 2 = 28.3, 2 df, P < 0.01) Branch 68 55 Trunk 27 25 Leaning tree 5 20 Tree species of perch (x 2 — 318.2, 3 df, P < 0.01) Ponderosa pine 82 7 Lodgepole pine 9 55 Douglas-fir 7 25 Other 2 13 a The 3 birds in Sheep and Bowman were combined due to sample size. portant habitat components for fledglings. Owlets left the nest before being able to fly, but leaning trees enabled owlets to climb to perches above the ground. Without leaning trees owlets would be vulnerable to terrestrial predators. Male Great Gray Owls foraged in a variety of habitats; partially logged stands did not appear to be detrimental, as 62% of foraging locations occurred 114 Bull et al. Vol. 22, No. 4 Figure 3. Locations at 15-min intervals of a hunting male Great Gray Owl in Spring study area during daylight. Observations were made on 10 d from 1 April-22 July 1985. there. Open stands of mature forests were used most for foraging, while subclimax and dense over-mature stands and clearcuts were used less frequently. Win- ter (1986) reported that Great Gray Owls foraged primarily in or along meadow edges; Franklin (1987) found them foraging in clearcuts. Factors that are important in foraging habitats include high prey density, perch availability and forests that are open enough to allow birds to move freely. Relatively close spacing of some nesting pairs in Oregon support the belief that Great Gray Owls defend only the immediate vicinity around a nest (Bull and Henjum 1987). Hoglund and Lansgren (1968) reported pairs within 100 m of each other in Sweden; Mikkola (1976) reported 3 nests within 400 m of each other in Finland; and Wahlstedt (1974) reported 5 pairs within 3 km in April. More recently, Lehtoranta (1986) found 2 nests in Finland only 49 m apart, but since only 1 male was seen, polygamy seems possible. Because the species does not generally maintain mutually exclusive territories, fairly high densities can be obtained. Mikkola (1981) reported 8 nests in 100 km 2 in Finland, and Wahlstedt (1974) found 5 nests and an additional 4 pairs that he believed were nesting in a 100 km 2 area in Sweden. In Oregon we found the highest density of nesting Great Gray Owls reported for either North America or Europe. Winter 1988 Great Gray Owl Habitat 115 Acknowledgments We are grateful to R. G. Anderson, H. A. Akenson, J. Akenson, H. D. Cooper, S. P. Feltis, E. D. Forsman, R. Googans, R. A. Grove, W. I. Haight, J. S. Henderson, J. E. Hohmann, M. Hunter, M. D. Snider, M. E. Walker, and W. G. Williams. Funding was provided by the USDA Forest Service’s Pacific Northwest Research Station and Oregon Depart- ment of Fish and Wildlife Nongame Fund. Additional assistance was provided by Wallowa Valley Ranger Sta- tion, La Grande Ranger Station, and North Fork John Day Ranger Station. Literature Cited American Ornithologists’ Union. 1983. Check-list of North American birds. 6th ed. Allen Press, Inc., Lawrence, Kansas. 877 pp. Bull, E. L. 1987. Capture techniques for owls. Pages 291-293. In Proc. Northern Forest Owl Symposium, Winnipeg, Manitoba. USDA For. Serv., Rocky Mtn. Forest and Range Exp. Stn., Gen. Tech. Rep. RM- 142. and M. G. Henjum. 1987. The neighborly great gray owl. Nat. Hist. 9:32-41. , M. G. Henjum and R. G. Anderson. 1987. Nest platforms for great gray owls. Pages 87-90. In Proc. Northern Forest Owl Symposium, Winnipeg, Manitoba. USDA For. Serv., Rocky Mtn. Forest and Range Exp. Stn., Gen. Tech. Rep. RM-142. Burr, J. A. 1960. Soil survey, Starkey Experimental Forest and Range, Union and Umatilla Counties, Or- egon. USDA Soil Conserv. Serv. and For. Serv. 32 pp. Forsman, E. D. and T. Bryan. 1987. Distribution, abundance, and habitat of great gray owls in south- central Oregon. Murrelet 68:45-49. Franklin, A. B. 1987. Breeding biology of the great gray owl in southeastern Idaho and northwestern Wy- oming. M.S. Thesis. Humboldt State Univ., Areata, CA. 83 pp. Harris, W. C. 1984. Great gray owls in Saskatchewan (1974-1983). Blue Jay 42:152-160. Helo, P. 1984. Yon linnut. Kirja Suomen polloista. Kainuun Sanomain Kirjataino Oy. 240 pp. Hoglund, N. H. and E. Lansgren. 1968. The great grey owl and its prey in Sweden. Viltrevy 5:360-421. Isaacson, D. L., D. A. Leckenby and C. J. Alexander 1982. The use of large-scale aerial photography for interpreting Landsat digital data in an elk habitat- analysis project. /. Appl. Photogr. Eng. 8:51-57. Lehtoranta, H. 1986. Lapinpollojen Strix nebulosa la- hekkainen posinta. Lintumies 21:32. Mikkola, H. 1976. Konneveden lapinpollot. Savon Luonto 8:13-22. . 1981. Der Bartkauz Strix nebulosa. Die Neue Brehm-Bucherei 538. A. Ziemsen Verlag. Wittenberg- Lutherstadt. 124 pp. . 1983. Owls of Europe. Buteo Books, Vermil- lion, SD. 397 pp. Nero, R. W. 1980. The great gray owl — phantom of the northern forest. Smithsonian Inst. Press, Wash- ington, D.C. 167 pp. . 1982. Building nests for great gray owls. Siaha 4:41-48. , S. G. Sealy and H. W. R. Copland. 1974. Great gray owls occupy artificial nest. Loon 46:161- 165. Reynolds, R. T., E. C. Meslow and H. M. Wight. 1982. Nesting habitat of coexisting Accipiter in Ore- gon. /. Wild l. Manage. 46:124-138. Servos, M. C. 1986. Summer habitat use by the great gray owl ( Strix nebulosa ) in southeastern Manitoba M.S. Thesis. Univ. of Manitoba, Winnipeg. 63 pp. Smith, D. M. 1962. The practice of silviculture. John Wiley & Sons, Inc., New York. 578 pp. Wahlstedt, J. 1974. Lappugglan Strix nebulosa i Sver- ige 1973. Var Fagelvarld 33:132-139. Winter, J. 1986. Status, distribution, and ecology of great gray owls in California. M.S. Thesis. San Fran- cisco State Univ., CA. USDA Forest Service, Pacific Northwest Research Sta- tion, Forestry and Range Sciences Laboratory, La Grande, OR 97850. Address of second author: Or- egon Department of Fish and Wildlife, La Grande, OR 97850. Received 1 April 1988; accepted 20 September 1988 Short Communications /. Raptor Res. 22(4):1 16-1 17 © 1988 The Raptor Research Foundation, Inc. Male-biased Sex Ratio in Captive-bred Harris’ Hawks Harvey D. Bradshaw, Jr, and Thomas D. Coulson The Harris’ Hawk ( Parabuteo unicinctus ) is one of the few North American raptors in which the breeding unit often contains more than a mated pair. Breeding trios consisting of two males and a female are frequently seen (Mader 1975a, 1975b, 1979; Bednarz 1987), and simul- taneous polyandry has been observed on a few occasions (Mader 1979). In wild populations the sex ratio of adult Harris’ Hawks assessed by trapping may be male-biased in some areas (Mader 1979) but not in others (Hamer- strom and Hamerstrom 1978; J. Bednarz, pers. comm.). Among nestlings in Arizona, Mader (1979) reported that the sex ratio was not significantly different from 1:1 (52% male/48% female; N = 107, x 2 = 0.23, df = 1, P > 0.50). In sharp contrast we find that the sex ratio in captive- bred Harris’ Hawks is strongly skewed toward males. Six breeding pairs of Harris’ Hawks (3-12 yrs old and to our knowledge unrelated) composed of active and retired falconry birds were observed for 1-3 yrs. Breeding enclo- sures and care were as previously described (Coulson and Bradshaw 1982). Egg fertility was determined by candling 7 d after beginning incubation. Pairs were either allowed to hatch and rear their own eggs and young (N = 27) or eggs were removed from the nest as laid and incubated artificially (N = 125) (see Coulson and Bradshaw 1982). No significant difference in sex ratio of fledglings was found between naturally and artificially incubated eggs. Overall, egg fertility was 89.5% (136/152), hatching suc- cess was 89.7% (122/136) of fertile eggs, and 94.3% (115/ 122) of hatched eggs were fledged successfully. Fledglings recorded as female had body weight which at 70 d exceeded 750 g. Harris’ Hawks are highly dimorphic (Hamerstrom and Hamerstrom 1978) and the sexes can be readily dis- tinguished by weight or foot pad measurement (Bednarz 1987). Of 115 fledglings, 74 (64%) were males and 41 (36%) were females, which differed significantly from a 1:1 ratio (x 2 — 9.5, df = 1, P < 0.005). If all eggs hatched but not fledged were female the ratio remains significantly male- biased [74 males (61 %)/ 48 females (39%); x 2 = 5.5, df = 1, P < 0.05]. When each of six pairs was examined for male-biased fledgling sex ratio, two showed significant (P < 0.05) skewing. None of the pairs produced offspring with a sex ratio significantly different from the overall 64% male/3 6% female proportion. Likely, the skewing of sex ratio among Harris’ Hawk fledglings reflects an adaptation to social breeding (poly- andry and/or male nest helpers) observed in wild Harris’ Hawks. Because nest helpers or extra mates are chiefly male, we propose that Harris’ Hawks selectively produce more male offspring to maximize the number of helpers and to increase the likelihood that a related male inherits nesting territory from his parents. A male-biased sex ratio might be fixed genetically or represent a response to en- vironmental factors. In either case an explanation for the discrepancy between captive (male-biased) and wild (un- biased) (Mader 1979) fledgling sex ratio must be found. The survival rate of captive-bred Harris’ Hawks is very high, and the “natural” sex ratio set at egglaying is pre- served at fledging. If a male-biased sex ratio is determined genetically, an unbiased fledgling sex ratio in wild Harris’ Hawks must be due to differential mortality of male em- bryos or young, a possibility which can be explored in wild populations. To determine if environmental factors (such as food abundance and quality, proximity of other breeding pairs of Harris’ Hawks and availability of nest helpers) influence the fledgling sex ratio, the same param- eters can be varied in a captive setting. We have shown that captive Harris’ Hawks produce a preponderance of male offspring. The ability to manip- ulate the environment of captive pairs of Harris’ Hawks and to assess accurately the resulting sex ratio of offspring, free of uncontrolled loss of eggs or young, should help in understanding sex ratio skewing in wild populations. Acknowledgments We wish to thank Jim Bednarz and Mike Braun for many interesting discussions and for access to data prior to publication, and Bill Mader and Dr. Samuel Zeveloff for critical reading of this manuscript. Jerry Fraulini pro- vided sex ratio data for the hawks in his charge. HDB is a Helen Hay Whitney postdoctoral fellow in the labora- tory of Milton P. Gordon. Literature Cited Bednarz, J. C. 1987. Pair and group reproductive suc- cess, polyandry, and cooperative breeding in Harris’ Hawks. Auk 104:393-404. Coulson, T. D. and H. D. Bradshaw, Jr. 1982. Im- proving productivity in a backyard breeding project. Artificial incubation and multiple clutching in Harris’ Hawks. Hawk Chalk 21(3):37-42. Hamerstrom, F. and F. Hamerstrom. 1978. External sex characters of Harris’ Hawks in winter. Raptor Res. 12:1-14. 116 Winter 1988 Short Communications 117 Mader, W. J. 1975a. Extra adults at Harris’ Hawk nests. Condor 77:482-485. . 1975b. Biology of the Harris’ Hawk in southern Arizona. Living Bird 14:59-85. . 1979. Breeding behavior of a polyandrous trio of Harris’ Hawks in southern Arizona. Auk 96:776- 788. Department of Biochemistry SJ-70, University of Washington, Seattle, WA 98195. Address of second author: Department of Biochemistry, Louisiana State University Medical Center, 1100 Florida Av- enue, New Orleans, LA 70119. Received 23 March 1988; accepted 5 October 1988 /. Raptor Res. 22(4-): 1 17—118 © 1988 The Raptor Research Foundation, Inc. Eggs of the Orange-breasted Falcon ( Falco deiroleucus) Lloyd F. Kiff Earlier, Boyce and Kiff ( Raptor Res. 15:89-93, 1981) indicated there were probably no authentic egg specimens of the Orange-breasted Falcon ( Falco deiroleucus) in mu- seum collections. Recently, eggs laid by a captive female Orange-breasted Falcon at The Peregrine Fund, Inc., fa- cility at Cornell University were deposited with the West- ern Foundation of Vertebrate Zoology (WFVZ), thus en- abling a description of the eggs of this poorly studied species. The female which laid the eggs was taken as a nestling from a site near Tikal, El Peten, Guatemala, in April 1980. The sample includes 3 eggs (WFVZ 140,454) laid in 1983, 4 eggs (WFVZ 150,680) laid in 1984, and 3 eggs from 2 clutches (WFVZ 150,679) laid in 1985 (Fig. 1A). The eggs are typical of Falco in color, having a white ground color and markings of medium brown, reddish- brown and lilac. Markings vary greatly between years, as the clutch laid in 1984 is almost completely suffused with fine medium brown spots, whereas nearly all eggs laid in 1983 and 1985 are more boldly splotched with reddish- brown and lilac (Fig. 1 A). The extreme range of variation in the egg markings is of interest, given traditional as- sumptions of oologists and falconers that particular female falcons tend to lay eggs with consistent markings from one year to the next (e.g., Ratcliffe, D. E., The Peregrine Falcon, Buteo Books, Vermillion, South Dakota, 1980). In general Orange-breasted Falcon egg coloration more closely resembles eggs of the Prairie Falcon {Falco mexi- canus) and Aplomado Falcon (F. femoralis) than the gen- erally darker-colored eggs of the Peregrine {Falco pere- gnnus) and Bat Falcon {F. rujigulans) (Fig. IB). The eggs are short subelliptical (7) or subelliptical (3) in shape (Preston In Palmer, Handbook of North American birds, Vol. 1, Yale Univ. Press, New Haven, Connecticut, 1972). Average measurements of the sample of 10 eggs are 49.09 (46.71-52.99) x 38.96 (37.07-39.92) mm, and the empty shell weights averaged 0.344 g. Mean eggshell thickness for 10 whole eggshells and 4 additional samples of shell fragments from other eggs laid in 1985 was 0.335 (0.297-0.368) mm. Eggs tended to become shorter (50.60 to 48.97 to 47.73 mm) and broader (38.39 to 38.97 to 39.50 mm) in successive years of laying. Based on egg size and female body weight relationships in the genus Falco, Boyce and Kiff (1981) predicted that Orange-breasted Falcon eggs should measure about 48.0 x 37.5 mm with 95% confidence intervals ranging from 44.0 to 52.1 mm (length) and 33.8 to 40.0 mm (breadth). Measurements of Orange-breasted Falcon eggs given here fall close to predicted measurements and within associated 95% con- fidence intervals, which provides further confirmation that the purported Orange-breasted Falcon egg measurements discussed by Boyce and Kiff (op. cit.) were not authentic. Acknowledgments Tom J. Cade and Willard Heck of The Peregrine Fund, Inc., kindly made the Orange-breasted Falcon eggs avail- able to me, and Clark Sumida of the Western Foundation of Vertebrate Zoology provided the shell thickness mea- surements and egg photographs. The manuscript was im- proved greatly by the comments of Douglas Boyce and Clayton White. Support was provided by the Western Foundation of Vertebrate Zoology. Western Foundation of Vertebrate Zoology, Suite 1400, 1100 Glendon Ave., Los Angeles, CA 90024. Received 5 April 1988; accepted 15 September 1988 118 Short Communications Vol. 22, No. 4 Figure 1. (A) Orange-breasted Falcon eggs laid in 1983 (top), 1984 (middle), and 1985 (bottom). (B) Eggs of American Falco species. Smallest to largest: American Kestrel ( F . sparverius ), Bat Falcon ( F . rufigularis ), Aplomado Falcon (F. femorahs ), Orange-breasted Falcon ( F . deiroleucus), Prairie Falcon (F. mexicanus ), Peregrine Falcon (F. peregrinus), and Gyrfalcon (F. rusticolus). Winter 1988 Short Communications 119 J. Raptor Res. 22(4): 1 19-120 © 1988 The Raptor Research Foundation, Inc. Effect of Saline Added to Food on Weight Gain of Hand-raised Falcons L. W. Oliphant A number of published studies have suggested the im- portance of adequate fluids in the diet of nestling raptors (Olendorflf, R. R., Raptor Res. 6(1 ):6— 10, 1972; Dobbs, J. C. et al. Hawk Chalk 18(3):34-36, 1979; Oliphant, L. W. and S. V. Tessaro, Raptor Res. 19(2/3):79-84, 1985). Weaver and Cade (Falcon propagation. The Peregrine Fund, Inc., Boise, Idaho. 1985) recommend the addition of 0.9% saline or Ringers solution to ground Common Quail ( Coturnix coturnix ) to feeding young falcons, stating that sufficient fluids are necessary “to ensure proper diges- tion.” Nevertheless, numerous comments made at raptor propagation workshops indicate that many breeders are still not supplementing diets with fluids. This paper pre- sents data suggesting that growth rates of hand-reared falcons are substantially increased if saline is added to their food. Data were collected from young falcons raised at The Peregrine Fund, Inc., Cornell University, Ithaca, New York. Weight gain of offspring hatched in 1980 from 5 pairs of Peregrines (Falco peregrinus) and one pair of Gyr- falcons ( F . rusticolus ) were compared with weights of their offspring hatched in 1977. Young were raised in a similar manner both years except that 0.9% saline was added to the diet in 1980. An unmeasured quantity of saline was added to ground quail sufficient to produce a semi-fluid consistency. Drying 2 samples of ground quail (with and without saline) showed an increased water content of about 5% in the saline sample (72.7% and 67.8%, respectively). Weights of young falcons were taken in the early morning prior to first feeding at days 0 (hatch day), 5 and 10. Birds were not differentiated as to sex since a major divergence in body weight does not occur until after day 10. Day 10 weights of 1980 offspring were approximately twice that of 1977 offspring (Fig. 1). In spite of the small sample sizes the differences in average weights at day 5 and day 10 are consistent and statistically significant for most of the pairs. A /-Test pooling weight data from the 5 peregrine pairs showed a highly significant difference at days 5 and 10 (P < 0.0001). This level of significance is especially surprising considering that it pools data from subspecies with considerably different average body weights and possibly different growth rates. Although effects of saline added to the diet appear con- siderable, other uncontrolled factors may have contributed to the remarkably consistent differences in growth rate between the 2 years. There may have been, for example, small differences in feeding regimes such as amount fed/ feeding, number of feedings/day, timing of feedings, etc It was not determined if salt(s) are important or only increased water content. Similarly, the physiological mech- anism for the observed stimulation of growth rate is pres- ently unknown. After day 10 young falcons were returned to adults for further rearing and long-term effect, if any, on body size was not determined. These questions should be addressed under carefully controlled conditions using larger sample sizes, perhaps with a species such as the American Kestrel (F. sparverius). Acknowledgments This project was carried out at Cornell University while on sabbatical leave from the University of Saskatchewan. I am indebted to Tom Cade and The Peregrine Fund for allowing me to spend time at their facility and particularly to Bill Heck in helping me to gather data for this study. Department of Veterinary Anatomy, University of Sas- katchewan, Saskatoon, Saskatchewan S7N 0W0. Received 20 January 1988; accepted 8 December 1988 Figure 1. Average weights at 0, 5 and 10 days of age of young from 5 pair of Peregrines (Pairs 1-5) and 1 pair of Gyrfalcons (Pair 6) with (1980) and without (1977) saline added to their diet. Brood sizes (n) for each pair are given and the subspecies of the Peregrine pairs indicated above the graphs. Bars indicate standard deviations. Body Weight (g) Body Weight (g) Body Weight (g) 120 Short Communications Vol. 22, No. 4 Pair #1 (E.p. cassinl /F. p. anatum) Pair #2 (F. p. brookel ) Days Days Pair #3 (f. p. pealei ) Pair #4 (F. p. pereg rinus ) 350 300- 250- 200 - 150- 100 50 -I 0 K 1977 n-5 □ 1980 n-2 Days Days Pair #5 (F- p. tundrius) Pair #6 (F- rustlcolus) Days Days o o Winter 1988 Short Communications 121 /. Raptor Res. 22(4):121 © 1988 The Raptor Research Foundation, Inc. Osprey Preys on Tiger Salamander Michael M. King In addition to fish, Osprey ( Pandion haliaetus ) oppor- tunistically select alternative prey species including small mammals, birds, reptiles and amphibians (frogs) (Wiley, J. W. and F. E. Lohrer, Wilson Bull. 85:468-470, 1973; Swenson, J. E., /. Wildl. Manage. 42: 87-90, 1978; Cas- trale, J. S. and J. McCall, Raptor Res. 17:92, 1983; Lay- her, W. H., Wilson Bull. 93:469-470, 1984; Taylor, P., Raptor Res . 20:76, 1986). This note describes an instance of an Osprey taking a Tiger Salamander ( Ambystoma ti- grinum ) at Hill Air Force Base, Utah (HAFB). HAFB is located in northern Utah between Ogden and Salt Lake City and consists of approximately 2699 ha surrounded on 3 sides by developed communities and on the fourth by agricultural land. Gradually agricultural land is being converted to industrial and housing areas. No Osprey have been sighted at HAFB since the base started its Natural Resources Program over 10 yrs ago. The nearest nesting pair of Osprey is believed to be in the Flaming Gorge Reservoir area, approximately 225 km to the northeast. In light of increased urbanization of sur- rounding areas and the Osprey’s limited status in Utah (Utah Division of Wildlife Resources classification), the sighting of the Osprey on the base is noteworthy. On 8 September 1986 at 1245 H, I observed an Osprey soaring in a relatively tight circular pattern approximately 20 m above a small storm water retention pond at the southern boundary of the base. No fish inhabit the pond, but Tiger Salamanders are numerous and can be readily observed near the surface. During a 15 min period, the Osprey made 4 steep dives at the water and twice plunged into the water attempting to catch salamanders. On the second plunge, the Osprey was successful in grasping a salamander (about 13 cm long) in its talons and flying to the top of a power pole approximately 75 m away. The Osprey consumed the salamander in about 2- 3 min but remained on the pole for approximately 10 min after feeding before flying out of sight beyond HAFB boundaries. The next day, 9 September 1986, 2 Osprey were spotted soaring above the same pond between 0830-0930 H. How- ever, no attempts were made by either bird to catch sal- amanders (M. Sant, pers. comm.), and no Osprey have been observed on base since that time. Winds in excess of 40 km/hr in the HAFB area characterized both days the Osprey were observed. Possibly the birds were migrating to southern winter ranges and were opportunistically uti- lizing a locally abundant food source at HAFB. Environmental Planning, 2849 CES/DEVX, Hill Air Force Base, UT 84056. Present address: Dept. For- estry, Wildlife and Fisheries, University of Tennes- see, P. O. Box 1071, Knoxville, TN 37901-1071. Received 10 November 1987; accepted 8 December 1988 J. Raptor Res. 22(4): 1 21-1 22 © 1988 The Raptor Research Foundation, Inc. News and Reviews Burrowing Owl Colormarking: Request for Information. — During the summer of 1988 young and adult Burrowing Owls were banded and colormarked in southwest Manitoba as part of a management program attempting to conserve Manitoba’s dwindling population. Information is requested from anyone seeing a colormarked owl to aid in determining migration routes and wintering areas which are presently unknown. Each owl carries a U.S. Fish and Wildlife Service aluminum band and one plastic leg jess. Jesses are black, one centimeter wide and extend approximately 1.5 cm beyond the leg. We would appreciate anyone observing colormarked owls to record the following: location, date, leg of attachment of metal band and jess and details of the owl’s situation. Please send this information to Bird Banding Office, Canadian Wildlife Service, Ottawa, Ontario, Canada K1A 0E7 plus an additional copy to the banders Betsy Haug/Bob Nero, Manitoba Dep. Natural Resources, Box 14, 1495 St. James St., Winnipeg, Manitoba, Canada R3H 0W9. Thank you for your assistance. 122 News and Reviews Vol. 22, No. 4 L’Aigle Royal (Aquila chrysaetos ) en Europe. Actes du Premier Colloque International sur l’Aigle Royal en Europe, 13-15 Juin 1986 a Arvieux, France, edited by Alpine Research Center on the Vertebrates (C.R.A.V.E.). 1987. 174 pp., 4 color plates, numerous charts and graphs and b & w drawings. Available from C.R.A.V.E., B.P. 28, 05000 GAP, France or Michel Samuel le Coin, 05350 Molines en Queyras, France. Price + postage $40.00 U.S. (“simple edition”) or $48.00 U.S. (“luxury edition”). This volume is the proceedings of the first international symposium devoted to the Golden Eagle {Aquila chrysaetos ) in Europe held at Arzieuv in the Regional Natural Park of Queyras, France. As such, it represents a summary of what was known about the Golden Eagle in Europe with the principle eagle researchers of Europe having papers presented. The 30 papers are contained in 5 major chapters: The status in Europe (14 countries represented), the status in Mexico, Biology of eagles mainly in western Europe (4 countries represented), Management, and a summary of the direction future research should go. While most papers are in French with English summaries, those from Scotland (2 papers), Greece, Italian Apennines Mts., Norway, Poland, Sweden, Estonia, and Navarra (Spain) are in English. While a wealth of data is contained within the monograph it is difficult at best to say much about papers that methodically trace the distribution and numerical status of the species within a given geographical boundary. A nice review of the species’ status was given, however. Most countries that reported numerical status conditions indicated a stable or slightly increasing population. For example, Switzerland has reached a saturation condition. On the other hand, Greece has a declining population and in Poland the species was extinct by the mid- 1800s except in the Carpathian Mts. Today there may be 15 territories within Poland. Population estimates were given for 19 countries in Europe. The number of pairs was estimated at between 4250 and 4802 (Portugal had the least with 4, Spain the most with an average of 892). Earlier Cramp and Simmons (Handbook of the Birds of the Western Palearctic, vol. 2, Oxford Univ. Press, London, 1979) had estimates for 15 of the 19 reporting countries. The 1979 estimate for the 15 countries was between 1982 and 2341 pairs, while in the present 1986 monograph these 15 countries reported 3420-3802 pairs. The biggest change in estimates between 1979 and 1986 were in Spain (400 to an av. of 892 pairs), France (90 to 280 pairs), and Sweden (150 to 400 pairs). None of the countries represented in both the 1979 and 1986 sample showed a decrease. Some interesting biological data came from the following papers: R. Mathieu (Comportement et maturation sexuelle chez l’Aigle Royal, pp. 97-102) described breeding pairs composed of a bird in adult and a bird in immature plumage. He discussed variation within representative plumages and various selective values of plumages in general. M. Belaud (Observation du plumage de L’Aigle Royal en vol. pp. 130-132) gave useful information on plumage traits used to identify specific individuals while in flight. His illustrations attest to the range of variation and the ability of an array of traits, when taken together, to make an individual distinctive. Lastly, R. Grubac (L’Aigle Royal en Macedoine, pp. 37-39) summarized food data from 40-50 pairs in the Macedonian region of Yugoslavia. Overwhelmingly, the most important food was the Tortoise {Testudo hermanni-graeca ) followed by snakes and then Chamois {Rupicapra rupicapra). Overall, this is an important monograph on Aquila, especially for North American workers who all too frequently do not assess overseas literature. Unless, however, one is especially interested in the Golden Eagle specifically, the price may be somewhat restrictive. — Clayton M. White. Winter 1988 Index to R.R.R. #6, Vol. 21, Vol. 22 123 /. Raptor Res. 22(4):123-136 © 1988 The Raptor Research Foundation, Inc. THE RAPTOR RESEARCH FOUNDATION, INC. PUBLICATIONS INDEX Raptor Research Reports No. 6, The Ancestral Kestrel The Journal of Raptor Research, Volume 21 The Journal of Raptor Research, Volume 22 Compiled by Richard R. Olendorff and Jimmie R. Parrish The Raptor Research Foundation Bibliographic Index (. Raptor Research Reports No. 7) covers the first 20 years of the Foundation’s publications. The system used to compile the 20 year index is called LIT, which is a menu-driven literature retrieval system using dBASE. Coupled with an exhaustive Ornithological Keyword List, the system provides literature re- trieval by author, title, citation, species, geographic location and subject in an extremely user- friendly manner. Recently, the Foundation made the decision to use the system to produce annual indices traditionally published at the end of each volume. The continuity provided should give every user easy access to an extensive raptor data base. The following index covers 3 documents, Raptor Research Reports No. 6 (The Ancestral Kestrel), Volume 21 and Volume 22 of The Journal of Raptor Research. The index is presented in the same format as the 20 year index, using an Ornithological Keyword List which matches numbers assigned to individual papers appearing in indexed volumes. Numbers appearing at the beginning of each article in the contents of each volume are listed with the appropriate Ornithological Keyword. The keyword list is divided into 3 parts, Subject-Author Index, Species Index — Common Name, and Species Index — Scientific Name. An asterisk (*) following a number in the species keyword lists indicates that the article is wholly or substantially dealing with that particular species. A hyphen (-) following a number in the species keyword lists indicates that the species is treated less substantially or is mentioned only in passing. Further details on how to obtain the LIT System and the Raptor Research Foundation Publications Data Base are provided in Raptor Research Reports No. 7, or may be obtained by contacting Richard R. Olendorff, 6009 Viceroy Way, Citrus Heights, CA 95610, U.S.A. Subject-Author Index abandonment of nests 904 AGE AT FIRST BREEDING — CAPTIVE 937 ABSTRACT 931, 932, 933, 934, 935, 948, 949, 950, 951, 952, 968, 1014, 1015 ACTIGRAMS / ETHOGRAMS 909, 910, 924, 938, 1017 AERIAL SURVEY 953, 970, 973 AFRICA 913, 936, 948 AGE AT FIRST BREEDING — WILD 931, 943, 951 AGE CLASSES 953, 980 AGONISTIC BEHAVIOR 938, 959 AGRICULTURE, IMPACTS 903, 905, 906, 907, 909, 922, 938 124 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 AIRCRAFT, IMPACTS 953, 973, 999 BIBLIOGRAPHIES 976, 1026 ALFONZO, JAMES M. 1009 BIERREGAARD, RICHARD O. 983 ANESTHESIA 998 BILDSTEIN, KEITH L. 907 ANIMAL DAMAGE CONTROL 953 BIOMASS CONSIDERATIONS 997 ARIZONA 932 BIOMETRICS 901, 913, 999 ARTIFICIAL INCUBATION 941 BIORHYTHMS 1005, 1017 ARTIFICIAL INSEMINATION 941 BIRD, DAVID M. 912, 915, 917 ARTIFICIAL NESTBOXES 910, 912, 914, 915 BLASTING (DYNAMITE, ETC.) 953 ARTIFICIAL NESTING PLATFORMS 996, 1019 BODY WEIGHT 913, 937, 975, 980, 990, 997, 999 ARTIFICIAL NESTS 958 BOHALL-WOOD, PETRA G. 906 ASIA 949 BOHM, ROBERT T. 986 ASYNCHRONY 957, 958 BOLIVIA 1010 AUMANN, T. 980 BOOK REVIEWS 936, 988, 1002, 1025 AUSTRALIA 974, 980, 989 BORTOLOTTI, GARY R. 996 BALGOOYEN, THOMAS G. 909, 999 BOWMAN, REED 912, 915, 917 BANDING 905, 946, 952, 975, 991, 999 BOYCE, DOUGLAS A., JR. 901 BATHING 992 BEHAVIOR MODIFICATION BRADSHAW, HARVEY D. 1020 989, 1007 BEHAVIOR— GENERAL BREN, WILLIAM M. 989 907, 908, 909, 924, 938, 949, 951, 952, 956, 958, 959, 961, 980, 992, 993, 994, 999, 1015 BROODING 938, 958 BEHAVIORAL DEVELOPMENT 921, 1015 BROWN, BRYAN T. 984 Winter 1988 Index to R.R.R. # 6 , Vol. 21 , Vol. 22 125 BUCHANAN, JOSEPH B. 994 COLLOPY, MICHAEL W. 905 , 906 , 907 , 1001 BULGARIA 921 COLORADO 934 , 990 BULL, EVELYN L. 1018 , 1019 COLORMARKING 905 , 946 , 947 , 952 , 1024 BURKHOLDER, GARY 993 COMPUTER SOFTWARE/PROGRAMS 966 , 967 BYSTRAK, DANNY 902 COULSON, THOMAS D. 1020 CALIFORNIA 909 , 927 , 954 , 958 , 961 , 971 , 985 , 990 , 999 CUBA 904 , 978 CANADA 950 , 973 , 996 , 997 , 1013 , 1024 CURLEY, ELIZABETH M. 915 CANARY ISLANDS 1007 DAMS AND RESERVOIR, IMPACTS 989 , 993 CANNIBALISM 904 , 925 ddt/dde 904 , 916 , 936 CAPTIVE BREEDING — GENERAL 936 , 937 , 943 , 1020 , 1021 , 1022 DEFENSE OF NEST AGAINST MAN 921 CAPTURE 913 , 953 , 974 , 975 , 980 , 983 , 998 , 1005 , 1018 DEFENSE — INTERSPECIFIC 939 CARPENTER, ARTHUR L. 1000 DENSITY 903 , 905 , 957 , 969 , 973 , 978 , 1019 CARPENTER, THOMAS W. 1000 DIMORPHISM — SEX AND COLOR 907 , 909 , 913 , 1005 , 1014 CARRILLO, JOSE 1007 DISEASES OF WILD BIRDS 1003 CARRION FEEDING 940 DISPERSAL 903 , 912 , 931 , 934 , 951 , 967 , 969 , 1018 CEBALLOS, OLGA 1008 DISTRIBUTION — GENERAL 903 , 905 , 922 , 928 , 945 , 960 , 973 , 984 , 1010 , 1025 CENSUS — BIRDS 902 , 944 , 953 , 973 , 978 , 979 DIURNAL RAPTORS 936 , 963 , 979 , 991 , 1002 , 1004 CHILE 990 DONAZAR, JOSE ANTONIO 1008 CLARK, W. 991 DOUBLE CLUTCHING — CAPTIVITY 937 , 941 CLUTCH SIZE 904 , 937 , 950 DUCKS 942 126 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 DUFFY, K. 991 FLOATING POPULATIONS 989 DUNCAN, JAMES R. 912, 1013 FLORIDA 905, 906, 1005, 1014 DZUS, ELSTON A. 996 FOOD CACHING 907, 994 EGG DESCRIPTION 905, 1021 FOOD HABITS ANALYSIS — GENERAL 920, 1005 EGG LAYING IN CAPTIVITY 937, 941, 1020, 1021 FOOD HABITS ANALYSIS — PELLETS 920, 945, 954, 1005 EGG MEASUREMENTS 904, 921 EGGSHELL THINNING 904, 916, 1021 FOOD HABITS — GENERAL 901, 904, 906, 909, 920, 921, 922, 925, 933, 935, 938, 942, 945, 950, 952, 954, 957, 958, 975, 985, 990, 994, 997, 1014, 1018, 1023, 1025 EMISON, WILLIAM B. 989 FOOD SUPPLY, IMPACTS 903, 989, 990, 997 ENDANGERED SPECIES ACT FOSTERING — WILD 929 950, 997 ENERGETICS/FOOD REQUIREMENTS 910, 911, 922, 948 FULLER, MARK R. 902 EUROPE 903, 910, 921, 944, 991, 1006, 1008, 1025 GARNER, MICHAEL M. 998 EVOLUTION GEESE 901 961 FALCONRY — MANAGEMENT 922, 936 GERRARD, JON M. 996 FEDYNICH, ALAN M. 995 GESSAMAN, JAMES A. 911 FEEDING BEHAVIOR 904, 906, 907, 908, 909, 910, 922, 940, 942, 950, GILMER, DAVID S. 1012 952, 955, 959, 980, 985, 994, 998, 1005, 1013, 1014, 1017, 1019, 1023 GODFREY, RALPH D., JR. 995 FEEDING IN CAPTIVITY 937, 941, 1022 GORNEY, E. 991 FIELD IDENTIFICATION 1002, 1004 GRATSON, MICHAEL W. 1017 FLEDGING — CAPTIVITY GREENLAND 937, 941, 1020 957 FLEDGING — WILD GROWTH — GENERAL 921 921, 948, 997, 1022 FLIGHT BEHAVIOR 910, 970, 978, 980, 1011 GUATEMALA 1021 Winter 1988 Index to R.R.R. #6, Vol. 21, Vol. 22 127 HABITAT PREFERENCES 905, 906, 907, 922, 924, 933, 971, 1005, 1007, 1014, 1017, 1019 HACKING 947, 1015 HAGGAS, LUCINDA 11 HAMILTON, LAYNE L. 981 HAND REARING 948, 1022 HARVEST — LEGAL 931 HATCHING — ADULT BEHAVIOR 904, 921 HATCHING — CAPTIVITY 937, 941, 1020 HEAVY METALS 916 HELPERS 1020 HENJUM, MARK G. 1018, 1019 HERNANDEZ, MAURO 1006 HERONS 993 HOFFMAN, MARK L. 905 HOME RANGE 933, 934, 938, 951, 965, 967, 968, 969, 1017, 1018 HOUSING OF CAPTIVE BIRDS 937 HUMAN DIST — GENERAL IMPACTS 904, 952, 989 IDAHO 925, 938 IMPACTS — GENERAL 924 INBREEDING — WILD 912 INCUBATION 911, 921, 926, 958 INDICATORS 916 INDIVIDUAL IDENTIFICATION 932 INSECTS — GENERAL 1013 INTERSPECIFIC BEHAVIOR 909, 914, 915, 939, 957, 959, 961, 990, 993, 994, 999 IRRUPTION — PREY 973 IRRUPTION — RAPTORS 973 ISRAEL 991 JAPAN 949 JAKSIC, FABIAN M. 990 KEMP, ALAN C. 913 KIFF, LLOYD F. 1021 KING, MICHAEL M. 1023 KLEIN, BERT C. 983 KONRAD, PAUL M. 1012 LANE, PATRICIA A. 1013 LAPAROTOMY 937 LATITUDE 920 LEAD 916 LEFRANC, MAURICE N., JR. 979 128 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 LEGISLATION AND REGULATIONS MCKERN AN, ROBERT L. 964 985 LIFE TABLES MEETING SUMMARIES 931 977 LIMITING FACTORS MELANISM 903, 905, 950 1000, 1012 LINCER, JEFFREY L. MERCURY 916, 977 916 listing/status MEXICO 929 984 LOGGING, impacts 904, 1019 MEYER, RUTHE LASH 909 LONG-TERM STUDY 902, 903, 908, 910, 912, 921, 937, 949, 953, 980, 982, 989, 1019 MGMT REC — POWERLINES/ELECTRO. 982 LORENZO, JORGE DE LA CRUZ 904 MGMT REC — ROADS 1006 MICHIGAN LOUISIANA 924, 981 975, 1000 MADAGASCAR 936 MIGRATION 911, 940, 967, 970, 971, 991, 1011 MAN-CREATED SITUATIONS 989, 993 MILLSAP, BRIAN A. 979 MAN-MADE NEST SITES — BUILDINGS 989, 1007 MINING, IMPACTS 989 MAN-MADE NEST SITES— QUARRIES 989, 1007 MINNESOTA 986 MAN-MADE NEST SITES — UTIL STR 986 MISSOURI 922 MANAGEMENT — GENERAL 927, 988 MOLT 910 MANITOBA 1013, 1024 MONTANA 953, 960, 982 MAXWELL, TERRY C. 1010 MORTALITY — ADULT 937, 999 MCALLISTER, CHRIS T. MORTALITY — EGG 1011 904 MCCRARY, MICHAEL D. 985 MORTALITY — GENERAL 936, 966, 969, 981, 1006 MCGRADY, M. 991 MORTALITY — JUVENILE 951, 1006 Winter 1988 Index to R.R.R. #6, Vol. 21, Vol. 22 129 MORTALITY— NESTLING 904 MUELLER, HELMUT C. 908 MURPHY, ROBERT K. 1017 NEAREST NEIGHBOR ANALYSES 935, 950, 957 NEST SITE CHARACTERISTICS 904, 905, 914, 915, 921, 924, 927, 931, 935, 945, 957, 961, 962, 984, 985, 989, 993, 1007, 1017, 1019 NESTING 904, 905, 921, 922, 924, 934, 938, 943, 945, 957, 958, 984, 985, 986, 989, 993, 996, 1007, 1012, 1017, 1019 NETHERLANDS 910 NEW JERSEY 991 NEW MEXICO 926 NOGALES, MANUEL 1007 NOISE, IMPACTS 953 NORTH AMERICA 902, 991 NORTH CAROLINA 1015 NORTH DAKOTA 1012 NORTHWEST TERRITORIES 950, 973, 997 NUTRITION 948 O’NEIL, THOMAS A. 982 OBITUARY 1001 OHIO 993 OLIPHANT, L. W. 1022 OLSEN, GLENN H. 981 OREGON 945, 1018, 1019 OWLS 920, 923, 933, 934, 937, 943, 945, 946, 951, 954, 955, 956, 958, 960, 972, 973, 982, 990, 993, 996, 1003, 1006, 1013, 1018, 1019, 1024 PADRON, MANUEL 1007 PALEONTOLOGY 901 PARENTAL CARE 921, 958, 997 PATERSON, ROBERT M. 902 PERCHING 907, 951, 952, 1011, 1017, 1019 PESTICIDES — GENERAL 904, 916, 936, 937 PHENOLOGY 904, 921, 949, 951, 957, 958, 978, 993 PHILOPATRY 912 PHOTOGRAPHY (STILL AND MOVIE) 1004 PIRACY 925, 938, 959, 994 PLUMAGE 901, 921, 991, 1000, 1012 POISONING, IMPACTS 916, 956 POOLE, K. G. 997 POPULATION DYNAMICS 903, 931 POPULATION ESTIMATES 973, 1025 POPULATION RECOVERY 902, 944, 989, 1025 130 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 POST-FLEDGING REQUESTS FOR INFORMATION 934, 949, 951, 1006, 1008 946, 947, 1003, 1004, 1024 POWERLINES — BENEFICIAL 986 RESEARCH, IMPACTS 964, 973, 996 POWERLINES — ELECTROCUTION 982 RESEARCH — GENERAL 907, 963, 965, 966, 968, 969 POWERLINES— GENERAL REVIEW PAPERS 982, 986, 1006 907 PREDATION THEORY RHODE ISLAND 908, 909, 954, 969, 990, 1005, 1014 920 PREDATION, IMPACTS 1008, 1009 ROAD CENSUSES 970, 978, 979 PREDATORY EFFICIENCY 906, 907, 908, 909, 922, 940, 980, 1017 ROADS, IMPACTS 994, 1014, 907, 935, 978, 1006 ROBBINS, CHANDLER S. PREY STUDIES (SIMULTANEOUS) 909, 989 902 ROBERTS, DAN ALLAN PRITCHETT, CLYDE L. 1009 1015 ROHWEDER, RONALD S. PROCEEDINGS 936, 963, 1025 1018, 1019 ROSENFIELD, ROBERT N. PRODUCTIVITY PARAMETERS 904, 937, 950, 957, 993 1017 SALAMANDERS PUBLIC ATTITUDES 987 1023 SASKATCHEWAN 996 PUBLIC EDUCATION 987 SCHMIDL, DIETER 992 RANGE EXTENSION 960, 989, 1010 SCHREIBER, RALPH W. 985 RAPTOR INFO. CENTER (NWF) 988 SCHULTZ, C. 991 RAPTOR ORGANIZATIONS — GENERAL 918, 919, 930, 977 SEX RATIOS 1020 RAPTOR RESEARCH FOUNDATION 918, 919, 930, 976, 977, 987 SEXING 937 REFUGES — NATURAL AREAS 938 SHAW, DENICE 1010 REHABILITATION SHEEP 923, 981 953 REINTRODUCTION — GENERAL 923, 943, 981, 1015 SHOOTING, IMPACTS 981 Winter 1988 Index to R.R.R. #6, Vol. 21, Vol. 22 131 SITE TENACITY TIME- LAPSE PHOTOGRAPHY 912, 924, 931, 1019 958, 997 SMALLWOOD, JOHN A. 1005, 1014 TOLERANCE OF HUMAN DISTURBANCE 989 SMITH, DWIGHT E. TRANSLOCATION 993 953 SNAKES TRAPPING, IMPACTS 1009 995 SOCIAL BEHAVIOR TROPHIC STRUCTURE 969 990 SONOGRAPHS U.S. BUR. OF LAND MANAGEMENT 932 938 SOUND PLAYBACK CENSUSES U.S. FISH AND WILDLIFE SERVICE 1018 937 SOUTH AFRICA U.S. FOREST SERVICE 913, 948 958 SOUTH AMERICA URBANIZATION, IMPACTS 983, 1010, 1021 905, 1017 SOUTH CAROLINA 962 UTAH 911, 928, 939, 1009, 1023 SPAIN 944, 990, 1006, 1008 VILLAGE, ANDREW 903 STATISTICS 966, 967, 971, 979 VIRGINIA 952, 979 STATUS OF POPULATIONS VISION 924, 978, 1003, 1025 972 STRYCHNINE VOCALIZATION 956 921, 932, 933 SURVIVAL RATES 931, 966, 969, 981 WAGNER, WILLIAM D. 985 TABOR, STEPHEN P. 1011 WASHINGTON 971, 994 taxonomy/phylogeny 901 WEATHER, IMPACTS 907, 911, 924, 933, 978, 981, 996, 1018 TELEMETRY — SPATIAL 933, 934, 938, 940, 947, 953, 955, 963, 964, 965, 966, 967, 968, 969, 970, 971, 981, 983, 998, 1017, 1018, 1019 WHITE, CLAYTON M. 901, 989, 1025 WIEMEYER, STANLEY N. 916 TERRITORIALITY 903, 907, 909, 957, 1005, 1014, 1019 WILEY, JAMES W. 978 TEXAS WILMERS, THOMAS J. 971, 995, 1011 914 132 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 WINTERING 903, 907, 909, 952, 959, 971, 985, 999, 1005, 1014, 1018 WISCONSIN 1017 WOTZKOW, CARLOS 904, 978 WYOMING 935 ZIMBABWE 936 ZWANK, PHILLIP J. 981 Species Index — Common Name AMERICAN KESTREL 901-, 903-, 904*, 90S*, 906*, 907*, 908*, 909*, 911*, 912*, 914*, 915*, 916*, 917*, 922*, 923-, 941-, 990-, 991-, 999*, 1000*, 1005*, 1014* AUSTRALIAN GOSHAWK 980* AUSTRALIAN KESTREL 901-, 903-, 917-, 989- bald EAGLE 923-, 924*, 932*, 940-, 947*, 952*, 959*, 964-, 970-, 971-, 981-, 984*, 985*, 986*, 994-, 996* BARN OWL 920*, 923-, 937-, 943*, 990- BARRED FOREST FALCON 983- BARRED OWL 990- bay-winged HAWK 991- , 998*, 1020* black kite 923-, 974-, 991- black VULTURE 1011 - BOREAL owl 933*, 955* burrowing owl 990-, 1024* CALIFORNIA CONDOR 936- cape VULTURE 948* COLLARED SPARROW-HAWK 980- COMMON BUZZARD 991- COMMON KESTREL 901-, 903*, 907*, 910*, 917*, 992-, 1000-, 1007* COMMON SCOPS OWL 990- COOPER’S HAWK 979*, 982-, 991-, 1017* DICKINSON’S KESTREL 901-, 917- EGYPTIAN VULTURE 1008* ELEANORA’S FALCON 992- EURASIAN PYGMY OWL 945- EUROPEAN SPARROW-HAWK 905-, 991- FERRUGINOUS HAWK 935*, 959-, 1012* FLAMMULATED OWL 934*, 960* FOX KESTREL 901-, 917- GOLDEN EAGLE 927-, 935*, 939*, 940*, 949*, 953*, 956-, 959-, 981-, 982*, 985-, 986-, 989-, 1015*, 1025* GREAT GREY OWL 958*, 1018*, 1019* Winter 1988 Index to R.R.R. #6, Vol. 21, Vol. 22 133 GREAT HORNED OWL 956*, 972*, 982-, 990-, 993* GREATER KESTREL 901-, 903-, 913*, 917- grey KESTREL 901-, 917- griffon VULTURE 944* GYRFALCON 929*, 941-, 950*, 957*, 992-, HOODED VULTURE 991- LANNER FALCON 992- LESSER KESTREL 901-, 903-, 917-, 992- LEVANT SPARROW-HAWK 991- LINED FOREST FALCON 983* LITTLE OWL 990-, 1006* LONG-EARED OWL 990-, 993- long-legged BUZZARD 921*, 991- MADAGASCAR KESTREL 901-, 917- MAURITIUS KESTREL 901-, 917-, 923- merlin 923-, 928*, 991-, 994* MISSISSIPPI KITE 962-, 1010* MOLLUCCAN kestrel 901-, 917- northern GOSHAWK 923-, 969-, 982-, 991-, 1019- northern HARRIER 925-, 938*, 942*, 994-, 995* orange-breasted falcon 1021 * ORNATE HAWK-EAGLE , 996*, 1013* 983- osprey 961*, 986-, 996-, 1023* PEREGRINE falcon 925-, 926*, 938-, 939*, 941*, 957*, 970-, 971-, 989*, 991-, 992-, 999*, 1022* PHILIPPINE EAGLE 923- 997*, 999*, 1022* prairie falcon 925*, 927*, 931*, 935*, 939-, 941*, 992-, 999* PYGMY OWL 945* red-footed falcon 901-, 917- red-shouldered HAWK 981* RED-TAILED HAWK 927-, 935*, 939-, 956*, 959-, 979*, 981*, 982-, 994-, 1009*, 1019- saw-whet OWL 933*, 990- screech OWL 937*, 951*, 990-, 1006- SEYCHELLES KESTREL 901-, 903-, 917- SHARP-SHINNED HAWK 975*, 979*, 980-, 991- short-eared OWL 990- snowy OWL 946*, 973*, 1003* SPOTTED OWL 954* steller’s sea eagle 991- swainson’s hawk 982- swallow-tailed KITE 962* TAWNY OWL 955-, 972- 134 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 TURKEY VULTURE 939-, 978*, 1011* URAL OWL 955- whistling HAWK 974- white-bellied SEA EAGLE 974* Species Index — Scientific Name ACCIPITER BREVIPES 991- ACCIPITER CIRRHOCEPHALUS 980- ACCIPTTER COOPERII 979*, 982-, 991-, 1017* ACCIPITER FASCIATUS 980* ACCIPITER GENTILIS 923-, 969-, 982-, 991-, 1019- ACCIPITER NISUS 905-, 991- ACCIPITER ST HIATUS 975*, 979*, 980-, 991- AEGOLIUS ACADICUS 933*, 990- AEGOLIUS FUNEREUS 933*, 955* AQUILA CHRYSAETOS 927-, 935*, 939*, 940*, 949*, 953*, 956-, 959-, 981-, 982*, 985-, 986-, 989-, 1015*, 1025* ASK) FLAMMEUS 990- ASIO OTUS 990-, 993- AT1IENE CUNICULARIA 990-, 1024* ATHENE NOCTUA 990- , 1006* BUBO VI R GINIANUS 956*, 972*, 982-, 990-, 993*, 996*, 1013* BUTEO BUTEO 991- BUTEO ] A M A ICENSIS 927-, 935*, 939-, 956*, 959-, 979*, 981*, 982-, 994-, 1009*, 1019- BUTEO LI MEATUS 981* BUTEO REGALIS 935*, 959-, 1012* BUTEO RUFINUS 921*, 991- BUTEO SWAIN SON I I 982- CATHARTES AURA 939-, 978*, 1011* CIRCUS CYANEUS 925-, 938*, 942*, 994-, 995* CORAGYPS ATRATUS 1011 - ELANUS FOR FIC ATUS 962* FALCO ALOPEX 901-, 917- FALCO ARAEA 901-, 903-, 917- FALCO ARDOSIACEUS 901-, 917- FALCO BIARMICUS 992- FALCO CENCHROIDES 901-, 903-, 917-, 989- FALCO COLUMBARIUS 923-, 928*, 991-, 994* FALCO DEIR OLE UCUS 1021 * Winter 1988 Index to R.R.R. #6, Vol. 21, Vol. 22 135 FALCO DICKINSONI 901-, 917- FALCO ELEANORAE 992- FALCO MEXICANUS 925*, 927*, 931*, 935*, 939-, 941*, 992-, 999* FALCO MOLUCCENSIS 901-, 917- FALCO NAUMANNI 901-, 903-, 917-, 992- FALCO NEWTONI 901-, 917- FALCO PEREGRINES 925-, 926*, 938-, 939*, 941*, 957*, 970-, 971-, 989*, 991-, 992-, 999*, 1022* FALCO PUNCTATUS 901-, 917-, 923- FAI.CO R UPICOL OIDES 901-, 903-, 913*, 917- FALCO RUSTICOLUS 929*, 941-, 950*, 957*, 992-, 997*, 999*, 1022* FALCO SPARVER1US 901-, 903-, 904*, 905*, 906*, 907*, 908*, 909*, 911*, 912*, 914*, 915*, 916*, 917*, 922*, 923-, 941-, 990-, 991-, 999*, 1000*, 1005*, 1014* FALCO TINNUNCULUS 901-, 903*, 907*, 910*, 917*, 992-, 1000-, 1007* FALCO VESPERTINUS 901-, 917- FALCO ZONIVENTRIS 901-, 917- GLA UCIDIUM GNOMA 945* GLA UCIDIUM PASSERINUM 945- GYMNOGYPS CALIFORNIANUS 936- GYPS COPROTHERES 948* GYPS FULVUS 944* HALIAEETUS LEUCOCEPHALUS 923-, 924*, 932*, 940-, 947*, 952*, 959*, 964-, 970-, 971-, 981-, 984*, 985*, 986*, 994-, 996* IIALIAEETUS LEUCOGASTER 974* HALIAEETUS PELAGICUS 991- HALIASTUR SPHENURUS 974- ICT1NIA M1SISIPPIENSIS 962-, 1010* MIC RASTER GILVICOLLIS 983* MICRASTUR RUFICOLLIS 983- MILVUS MIGRANS 923-, 974-, 991- NECROSYRTES MON ACT! US 991 - neophron PERCNOPTER US 1008* NYCTEA SCANDIACA 946*, 973*, 1003* OPUS AS 10 937*, 951*, 990-, 1006- < 9777.9 FLAMMEOLUS 934*, 960* O'l'US SCOPS 990- PANDION HALIAETUS 961*, 986-, 996-, 1023* PARABUTEO UNICINCTUS 991- , 998*, 1020* PI THE COP HA G A JEFFERY1 923- SPIZAETUS ORNATUS 983- . 97 R IX ALUCO 955-, 972- STRIX NE BUI.OS A 958*, 1018*, 1019* 136 Index to R.R.R. #6, Vol. 21, Vol. 22 Vol. 22, No. 4 STRIX OCCIDENTALIS 954* STRIX URALENSIS 955 STRIX VARIA 990- TYTO ALBA 920*, 923-, 937-, 943*, 990- 1985 Peregrine Falcon Conference Proceedings The Peregrine Fund, Inc., is pleased to offer Peregrine Falcon Populations: Their Man- agement and Recovery, the proceedings of the 1985 Peregrine Conference held in Sacramento, California, in conjunction with the 20th Annual Meeting of The Raptor Research Foundation, Inc. The Peregrine Conference was the 20th anniversary of the now-famous Madison Peregrine Conference convened by Joseph J. Hickey in 1965 at the University of Wisconsin. This hardbound book with four-color jacket is an 850+ page, single volume edited by Tom J. Cade, James H. Enderson, Carl G. Thelander and Clayton M. White, with an Introduction by Tom J. Cade and a Foreword by Roger Tory Peterson. The book includes 81 chapters by Peregrine researchers from around the world, four commentaries and a Conference Summary by Ian Nisbet. Several chapters have been added to those presented at Sacramento, as well as 32 pages of photographs, a four-color plate of a Peregrine painting by Jim Grier, additional artwork by John Schmitt and an up-to-date world distribution map. Sections include: conference keynote addresses by J. J. Hickey, D. A. Ratcliffe and M. W. Nelson; status of Peregrine populations since 1965-North America; status of Peregrine populations since 1965-Europe; Peregrines in the rest of the world; DDT and other chemical problems; migration and banding studies; captive propagation, reintroduction, and management; dynamics and ecology of Peregrine populations; geographic variation in Peregrine populations; and Man and the Peregrine. Copies can be ordered at the price of $45.00 U.S. plus $5.75 postage and handling in the United States. Foreign shipping per copy, $5.00 surface, $20.00 airmail. Privately published by The Peregrine Fund, Inc., as an informational service, this volume represents a real bargain. To order send check or money order (U.S. funds only; please, no cash) to The Peregrine Fund, Inc., World Center for Birds of Prey, 5666 West Flying Hawk Lane, Boise, ED 83709. THE RAPTOR RESEARCH FOUNDATION, INC. (Founded 1966 ) OFFICERS PRESIDENT: Gary E. Duke SECRETARY: James D. Fraser VICE-PRESIDENT: Richard J. Clark TREASURER: Jim Fitzpatrick BOARD OF DIRECTORS EASTERN DIRECTOR: Keith Bildstein CENTRAL DIRECTOR: Patrick T. Redig MOUNTAIN & PACIFIC DIRECTOR: W. Grainger Hunt EAST CANADA DIRECTOR: David M. Bird WEST CANADA DIRECTOR: Lynn Oliphant INTERNATIONAL DIRECTOR: Bernd Meyburg DIRECTOR AT LARGE #1: Michael Collopy DIRECTOR AT LARGE #2: Gary Duke DIRECTOR AT LARGE #3: Jeffrey L. Lincer s******************** EDITORIAL STAFF EDITOR: Jimmie R. Parrish, Department of Zoology, 159 Widtsoe Building, Brigham Young Uni- versity, Provo, Utah 84602 ASSOCIATE EDITORS Reed Bowman — Behavior Susan Chaplin — Anatomy and Physiology Richard J. Clark — Order Strigiformes JEFFREY L. Lincer — Environmental Chemistry and Toxicology Carl Marti — Ecology Patricia P. Rabenold — New World Vultures Patrick T. Redig — Pathology , Rehabilitation and Reintroduction Sanford R. Wilbur — Old World Vultures INTERNATIONAL CORRESPONDENT: Richard J. Clark, York College of Pennsylvania, Coun- try Club Road, York, Pennsylvania 17405 The Journal of Raptor Research is distributed quarterly to all current members. Original manuscripts dealing with all aspects of general ecology, natural history, management and conservation of diurnal and nocturnal predatory birds are welcomed from throughout the world, but must be written in English. Contributors should submit a typewritten original and three copies of text, tables, figures and other pertinent material to the Editor. Two original copies of photographic illustrations are required. All submissions must be typewritten double-spaced on one side of 8% x 11-inch (21 Vi x 28 cm) good quality, bond paper. Number pages through the Literature Cited section. The cover page should contain the full title and a shortened version of the title (not to exceed 30 characters in length) to be used as a running head. Author addresses are listed at the end of the Literature Cited section. Provide an abstract for each manuscript more than 4 double-spaced typewritten pages in length. Abstracts are submitted as a separate section from the main body of the manuscript and should not exceed 5% of the length of the manuscript. Both scientific and common names of all organisms are always given where first appearing in the text and should conform to the current checklists, or equivalent references, such as the A.O.U. Checklist of North American Birds (6th ed., 1983). Authors should ensure that all text citations are listed and checked for accuracy. If five or fewer citations appear in the text, place the complete citation in the text, following these examples: (Brown and Amadon, Eagles, Hawks and Falcons of the World. McGraw-Hill, New York, 1968), or Nelson ( Raptor Res. 16(4):99, 1982). Metric units should be used in all measurements. Abbreviations should conform with the Council of Biology Editors (CBE) Style Manual, 5th ed. Use the 24-hour clock (e.g,, 0830 and 2030) and “conti- nental” dating (e.g., 1 January 1984). A more detailed set of instructions for contributors appeared in J. Raptor Res., Vol. 21, No. 1, Spring 1987, and is available from the Editor. Send all manuscripts for consideration and books for review to the Editor.