I % Vrt* “li Tr* ^ 3«‘‘i -v»f /^. ■»°*^ S'''p ;fS Raptor Resea Volume 29 March 1995 Number 1 Contents Nesting Density, Nest Area Reoccupancy, and Monitoring Implications for Cooper’s Hawks in Wisconsin. Robert N. Roseneeld, John Bielefeldt, Joelle L. Affeldt and David J. Beckmann 1 Winter Movements of Adult Northern Goshawks That Nested in Southcentral Wyoming. John R. Squires and Leonard F. Ruggiero 5 Prey OF Nesting Bald Eagles in Texas. David W. Mabie, M. Todd Merendino and David ' H. Reid 10 What is FaLCO ALTAICUS MeNZBIER? David H. Ellis 15 Prey Capture by Peregrine Falcons Wintering on Southern Vancouver Island, British Columbia. Dick Dekker 26 Short Communications Additional Records of White-tailed Kites in Baja California Sur, Mexico. Ricardo Rodriguez-Estrella, Jose Antonio Donazar and Fernando Hiraldo 30 Nest Structure Cohabitation by Raptors in Southeastern Idaho. Richard W. Hansen and Lester D. Flake 32 Letters 35 Book Reviews. Edited by Jeffrey S. Marks 37 Abstracts of Presentations Made at the Annual Meeting of the Raptor Research Foundation, Inc. 41 Manuscript Referees 75 Thesis and Dissertation Abstracts 76 Index TO Volume 28 79 The Raptor Research Foundation, Inc. gratefully acknowledges a grant and logistical support provided by Weber State University to assist in the publication of the journal. He iH s): N: at >1: ill: ^ 4 # 4: :ii 4::!! Persons interested in predatory birds are invited to join The Raptor Research Foundation, Inc. Send re- quests for information Concerning membership, subscriptions, special publications, or change of address to Jim Fitzpatrick, Treasurer, 143'77 llVtii Street South, Hastings, Minnesota 55033, U.S.A. The Journal of RafM&r Rsseardi (ISSN 0892-101 6) is published quarterly and available to individuals for $24,00 per year and to libraries and institulh>n& for $30.00 per year from The Raptor Research Foundation, Inc., 14377 117th Street South, Hastings, Minnesota 55033, U.S,A. (Add $3 for destinations outside of the conti- nental United States.) Second class postage paid at Hastings, Minnesota, and additional mailing offices. POST- MASTER: Send address changes to The Journal of Raptor Research, 14377 ll7th Street South, Hastings, Min- nesota 55033, U.S.A. Printed by Allen Prem, Inc., Lawrence, Kansas, U.S.A Copyright 1995 by The Raptor Research Foundation, Inc. Printed in U.S.A. 0 This paper meets the mqulfenwnts of ANSl/NJSO Z39. 48-1 992 (Permai^nce of Paper). THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC. VoL. 29 March 1995 No. 1 J. Raptor Res. 29(l);l-4 © 1995 The Raptor Research Foundation, Inc. NESTING DENSITY, NEST AREA REOGGUPANGY, AND MONITORING IMPLIGATIONS FOR GOOPER’S HAWKS IN WISGONSIN Robert N. Rosenfield Department of Biology, University of Wisconsin, Stevens Point, WI 54481 U.S.A. John Bielefeldt Park Planning, Racine County Parks, Sturtevant, WI 53177 U.S.A. JOELLE L. AFFELDT W3832 Manitowoc Road, Kaukauna, WI 54130 U.S.A. David J. Beckmann College of Natural Resources, University of Wisconsin, Stevens Point, WI 54481 U.S.A. Abstract. — We found a stable, long-term nesting density of 331 ha/pair, and a minimal intergeneration turnover time of 6 yr for breeding Cooper’s hawks (Accipiter cooperii) in a rural Wisconsin study site. In zm urban area we documented the highest known nesting density, 272 ha/pair, reported for the species. Both rural and urban Wisconsin study sites exhibited high productivity, comparable to pre-DDT years (1929-45) for the northeastern U.S. We propose evziluating nest area reoccupancy at 6-yr intervals as a practical means of monitoring Cooper’s hawk populations at the level of state and/or other management unit. Key Words: Accipiter cooperii; Cooper's hawk; nesting density; nest area reoccupancy; population monitoring. Densidad de nidificacion, area de reocupacion de nidos y monitoreo de Accipiter cooperii en Wisconsin Resumen. — Encontramos una estable densidad de nidificacion, en el largo plazo, 331 ha/pareja y un tiempo minimo de recambio intergenaracional de seis anos para Accipiter cooperii reproductivos en un sitio rural de estudio, en Wisconsin. En una localidad urbana documentamos la mayor densidad de nidification conocida y reportada para esta especie, 272 ha/pareja. En ambos sitios de estudio, esta especie mostro alta reproductividad, comparable a los anos pre-DDT (1929-45) para el Noreste de los Estados Unidos. Proponemos evaluar el area de reocupacion de nidos en intervalos de seis anos, como un promedio practice de monitoreo de las poblaciones de A. cooperii a nivel de estado y/u otra unidad de manejo. [Traduccion de Ivan Lazo] Long-term research on falconiforms in relatively sta- ble trophic and vegetational environments has often shown a corresponding stability in the hawks’ breeding densities (Newton 1991). Our studies of the Cooper’s hawk {Accipiter cooperii) in Wisconsin have yielded another instance of stable density and nest dispersion at the highest rural density known for the species, an even higher nesting density in a heavily altered urban environment, and productivity indices — both urban and rural — consistent with historical (pre-DDT) levels. We 1 2 Rosenfield et al. VoL. 29, No. 1 Figure 1 . Distribution of Cooper’s hawk nests on the rural KM study area in southeastern Wisconsin. use these results to propose a practical monitoring tech- nique, based on nest area reoccupancy, for a species still considered uncommon or rare in many parts of the eastern United States (Rosenfield and Bielefeldt 1993b). Methods To determine nesting density (hectares per active nest), we searched intensively for Cooper’s hawk nests on two study areas in Wisconsin. The 2980-ha rural area in the Kettle Moraine State Forest (hereafter KM), Waukesha County, was delineated by rectilinear roads and land survey section lines (Fig. 1). The KM area, studied 1982-93, was 40% wooded with conifer plantations contributing one-third of forest cover (for further descriptions of the KM study airea, see Rosenfield et al. 1991, and Bielefeldt zind Rosenfield 1992). The 3540-ha urban area in the city of Stevens Point and its suburbs (hereafter SP), Portage County, was delin- eated by a river on the west and section lines elsewhere (Fig. 2). The SP area, studied 1993, was a mix of residential, commercial, zind industrial land uses with remnant patches of deciduous and coniferous woodland (for more description. Figure 2. Distribution of Cooper’s hawk nests on the urban SP study area in central Wisconsin. see Murphy et al. 1988). We fixed the boundaries of both study areas before beginning our nest searches. In the context of population stability (see below), mark- recapture data from the KM in 1986 and 1992 revealed minimal intergenerational turnover time more clearly than similar data from other study years. In the years considered here, all 18 nests in the KM (1986, 1992) and 12 of 13 nests in SP (1993) were found at pre-laying or incubation stages of breeding. We excluded one SP nest found at the nestling state and used the remaining 30 in calculating nest success. In both areas we counted most clutches, banded all nestlings >14 d of age, and trapped and banded most breeding adults at known nests (Rosenfield and Bielefeldt 1993a). We used number of bandable nestlings per successful nest to compare productivity on our study areas with comparably reported historical data for the northeastern United States (Henny and Wight 1972). We measured interyear nest dis- tances on 1 :4800 aerial photos. A nesting area was considered reoccupied when we found a nest in subsequent year(s) within an arbitrary search area (ca. 800 m diameter) centered on the site’s original nest (Rosenfield and Bielefeldt 1992), as discovered 1982-85. Results and Discussion We found nine nests (all in pine plantations on the rural KM study area in 1986 (Fig. 1), for a minimal density of 331 ha per active nest. In 1992, all nine of these nesting areas (again plantations) were reoccu- pied, with a median interyear nest distance of 335 m (range = 30-665 m); no additional nests were found in 1992. These 1986 and 1992 nesting densities were at the time the highest reported for the species, and March 1995 Cooper’s Hawk Nesting Density 3 Table 1. Productivity indices on the rural KM and urban SP study areas in 1986, 1992, and 1993, KM 1986 KM 1992 SP 1993 X clutch size (JV) 3.7 (6) 4.3 (7) 4.2 (9) X bandable young/successful nest (N) 3.3 (7) 3.8 (8) 4.0 (9) % nest success (N) 78 (9) 89 (9) 75 (12) approximately 2-5 times greater than those previously published (Rosenfield et al. 1991). We marked all breeding adults at the 1986 KM nests; subsequent trapping and banding at these szime nesting areas in following years showed that all the 1986 adults had been replaced by new breeders by 1992. For males we know that replacement was not a result of movement between nesting areas; we have strong evidence from our mark-recapture studies statewide (>200 nests, 1980-93) that male Cooper’s hawks show lifetime fi- delity to breeding sites (Rosenfield and Bielefeldt un- publ. data). We have detected only nine interyear movements between nesting areas in females during 14 yr of statewide study, and mortality rates appear similar for both sexes (Rosenfield and Bielefeldt un- publ. data). We therefore assume that replacement of females over 6 yr on the KM involves the deaths of previous breeders. Both nesting density and nest dis- persion were thus stable during a complete 6-yr inter- generational turnover of breeding adults at all known nest sites on the KM study area. These data provide another example of long-term stability of falconiform densities in stable environments (see Newton 1991). In 1993, we found 13 nests on the urban SP study area (Fig. 2), where density (272 ha per active nest) exceeded the KM density. Means for clutch size and number of bandable young per successful nest, and nest success on both sites (Table 1), were similar to those reported in other recent studies (Rosenfield and Bielefeldt 1993b). Means for clutch size and number of bandable young were also comparable to historical data for pre-DDT years (1929-45) in the northeastern United States (Henny and Wight 1972). Nest site habitat on the urban SP area was char- acterized by small, highly fragmented woodlots (1-12 ha) potentially subject to much human disturbance. All nests in the rural KM area were located in conifer plantations, which might be regarded as inferior to natural forests in carrying capacity for raptors (New- ton 1991). Nevertheless, both urban and rural sites exhibited high productivity and density. Some re- searchers have suggested that the Cooper’s hawk is an area-sensitive species that may be adversely affected by forest fragmentation and loss of nest site habitat (Bosakowski etal. 1993, Robinson 1991 and references therein). Our results on the urban SP area do not support this premise. Monitoring Implications. Population stability and nest area reoccupancy could, of course, be monitored in the long term by resurveying study areas at intervals approximating the maximum known longevity of a species, thereby excluding the potential effect of nest area fidelity. However, the mandates of conservation agencies may require that they survey populations at intervals shorter than a species’ longevity. The lon- gevity record for the Cooper’s hawk is 12 yr (Rosenfield and Bielefeldt 1993b). Reoccupancy of all KM nesting areas with a complete intergenerational turnover of breeding adults in the relatively short span of 6 yr suggests a way of using reoccupancy to monitor the stability or possible declines of a breeding population of Cooper’s hawks on an arbitrary area, such as a management unit, where more intensive techniques are not feasible. From a management standpoint, a prac- tical cost-efficient monitoring procedure for Cooper’s hawks in Wisconsin (or some other area) could be implemented by evaluating nest area reoccupancy at 6-yr intervals when the influence of site fidelity by previous breeders has been minimized. If a studied population exhibits long-term use of breeding sites by different adults (i.e., recruitment), then the population must be at least stable. For management purposes it is usually impractical to determine if the population is sustained by local recruits; nonetheless, if recruitment is adequate, conservation agencies might not need to emphasize active management of this species. We have used our unpublished data on nest site fidelity and adult mortality to assess intergenerational turnover time for the KM population. However, it is unnecessary to determine fidelity or mortality when monitoring other study areas if similar turnover times are assumed. We stress that knowledge of the source of recruits on a given study area is not required for management purposes on that area. We emphasize that our results on nesting reoccupancy and turnover time were obtained in a relatively stable environment. Other 4 Rosenfield et al. VoL. 29, No. 1 monitoring intervals or regimes may be needed in areas of more frequent and extensive alterations of nesting habitat, and monitoring sites must be objectively se- lected (Johnson and Larson 1994). Acknowledgments We thank W. Gould and P.L. Kennedy for discussions regarding our ideas on population ecology. S. DeStefan, C. Henny, and I. Newton provided useful comments on an earlier draft of this manuscript. The University of Wisconsin at Stevens Point provided partial funding for our fieldwork. D. Snyder typed this paper. The University Personnel De- velopment Committee at the University of Wisconsin, Stevens Point, provided support for publication. Literature Cited Bielefeldt, J. and R.N. Rosenfield. 1992. Acadian flycatchers nesting in conifer plantations in southeastern Wisconsin. Passenger Pigeon 54:43-49. Bosakowski, T., R. Speiser, D.G. Smith and L.J. Niles. 1993. Loss of Cooper’s hawk nesting habitat to suburban development: inadequate protection for a state- endangered species. J. Raptor Res. 27:26-30. Henny, C.J. AND H.M. Wight. 1972. Population ecology and environmental pollution: red-tailed and Cooper’s hawks. USDI Fish Wildl. Serv. Rep. 2:229-250. Johnson, D.H. and D.L. Larson. 1994. Declines in am- phibian populations: real or perceived? Page 15 in R. Garvey [Ed.], Proc. N. Dakota Acad. Sci. 48. Murphy, R.K., M.W. Gratson and R.N. Rosenfield. 1988. Activity and habitat use by a breeding male Coop- er’s hawk in a suburban area. J. Raptor Res. 22:97-100. Newton, I. 1991, Population limitation in birds of prey, a comparative approach. Pages 3-21 in C.M, Perrins, J-D. Lebreton, and G.J.M. Hirons [Eds.], Bird popu- lation studies, relevance to conservation cmd management. Oxford Univ. Press, Oxford, U.K. Robinson, S.K. 1991. Effects of habitat fragmentation on midwestem raptors. Pages 195-202 in B.E. Pendleton and D.L. Krahe [Eds.], Proceedings midwest raptor man- ^ement symposium and workshop. Natl. Wildl. Fed. Sci. Tech. Ser. 15, Washington, DC U.S.A. Rosenfield, R.N. and J. Bielefeldt. 1992. Natal dis- persal and inbreeding in the Coojjer’s hawk. Wilson Bull 104:182-184. and . 1993a. Trapping techniques for breeding Cooper’s hawks: two modifications. /. Raptor Res. 27:170-171. AND . 1993b. Cooper’s hawk {Accipiter cooperii). In A. Poole and F. Gill [Eds.], The birds of North America, No. 75. Acad. Naturzil Sci., Philadelphia, PA U.S.A. and Am. Omithol. Union, Washington, DC U.S.A. , , R.K. Anderson and J.M. Papp. 1991. Status reports: accipiters. Pages 42-49 in B.E. Pendleton and D.L. Krahe [.Eds.] Proceedings midwest raptor man- ^ement symposium and workshop. Natl. Wildl. Fed. Sci. Tech. Ser. 15, Washington, DC U.S.A. Received 7 April 1994; accepted 4 October 1994 J Raptor Res. 29(1 );5 -9 © 1995 The Raptor Research Foundation, Inc. WINTER MOVEMENTS OF ADULT NORTHERN GOSHAWKS THAT NESTED IN SOUTHCENTRAL WYOMING John R. Squires and Leonard F. Ruggiero Rocky Mountain Forest and Range Experiment Station, 222 S. 22nd Street, Laramie, fVV 82070 U.S.A. Abstract. — Winter movements of four adult northern goshawks (Accipiter gentilis) that nest in south- central Wyoming were monitored during the winter of 1992-93. Goshawks initiated fall migrations in early fall (primarily mid-September) while weather conditions are moderate. Female 1 migrated 185 km south of her nest. She wintered in a mountainous area in Colorado at a higher elevation (2774 m) than her nest site (2500 m elevation). Male 1 migrated approximately 65 km west southwest of his nest before he was killed by a hard blow from a blunt object. This strike may have been caused by another raptor or a collision with the ground. Both Female 2 and Male 2 migrated in a southerly direction from their nests. They were located approximately 140 km and 70 km, respectively, from their nests before both birds were lost during inclement weather. All birds returned to their nests from wintering areas between 23 March to 12 April. Results from this study suggest to wildlife managers that some goshawk populations in the Rocky Mountains are migratory; efforts to manage this species need to consider both wintering and nesting habitat requirements. Key Words; Accipiter gentilis; Colorado; northern goshawk; winter movements; Wyoming. Movimentos invernales de adultos de Accipiter gentalis que nidificacon en el centrosur de Wyoming Resumen. — Se monitorearon los movimientos de invierno de cuatro individuos adultos de Accipiter gentilis que nidihcaron en el centro-sur de Wyoming, durante el invierno de 1992-93. Accipiter gentilis inicio su migracion otonal tempranamente (a mediados de septiembre) mientras las condiciones climaticas eran moderadas. La hembra 1 migro 185 km al sur de su nido. Ella inverno en un area montanosa en Colorado, a una altitud mayor (2774 m) que el sitio de nidificacion (2500 m). El macho 1 migro aproximadamente 65 km al oesta sur-oeste de su nido antes de ser muerto al sufrir un duro golpe. Esta muerte pudo ser causada p>or otra rapaz o por una colision con el suelo. Tanto la hembra 2 como el macho 2 migraron en direccion al sur, desde sus nidos. Elios fueron localizados aproximadamente a 140 km y 70 km, respectivamente; luego de condiciones climaticas desfavorables se perdio el rastro de ambos individuos. Todas las aves retornaron a sus areas de nidificacion entre el 23 de marzo y el 12 de abril. Los resultados de este estudio sugieren a los especialistas en manejo de vida silvestre que algunas poblaciones de A. gentilis en las Montanas Rocosas son migratorias; los esfuerzos necesarios para el manejo de esta especie deben considerar requerimiantos de habitat invernal y reproductivos. [Traduccion de Ivan Lazo] Winter movements of northern goshawks {Accip- iter gentilis) are poorly understood. Studies of gos- hawk migration in North America are limited (Doerr and Enderson 1965, Alaska Dept, of Fish and Game 1993). The limited knowledge that is available is based mostly on European studies (Opdam et al. 1977, Kenward et al. 1981, Marcstrom and Ken- ward 1981, Widen 1985, 1987, 1989). Those studies investigated a different subspecies of goshawk (A. g. gentilis) that lives in the human-dominated land- scapes of Europe, and their applicability to goshawks wintering in the Rocky Mountains is unknown. During 1992, we studied the winter movements of goshawks that nest in southcentral Wyoming. Study Site and Methods We trapped five (three females, two males) nesting adult goshawks and fitted each bird with a backpack radiotrans- mitter (25.5 g). Each bird was from a different pair. One female’s transmitter failed soon after she began her fall movements. The nest territories of all birds were located on the Medicine Bow National Forest in the Sierra Madre Mountains (1981-3366 m elevation) in southcentral Wy- oming. Lodgepole pine (Pinus contorta) with scattered quaking aspen stands (Populus tremuloides) is the dominant forest type at lower elevations (2300-2600 m) whereas subalpine fir {Abies lasiocarpa) and Engelmann spruce {Picea engelmannii) are dominant at higher (2438-3505 m) el- evations (Alexander et al. 1986, Marston and Clarendon 1988). Sagebrush {Artemisia spp.)-grassland prairies sur- round forested lands. The vegetative composition of this 5 6 John R. Squires and Leonard F. Ruggiero VoL. 29, No. 1 area is described in detail in Alexander et al. (1986). The climate on the study area is montane with precipitation ranging from 81 cm at 2440 m to 122 cm at 3350 m (Marston and Clarendon 1988). At lower elevations ap- proximately 50% of precipitation is snowfall compared to 75% at higher elevations. Nesting birds were trapped using a live great horned owl {Bubo virginianus) as a lure with a dho-gaza erected within 1 m of the lure (Beebe and Webster 1976, Rosen- field and Bielefeldt 1993). Goshawk movements were monitored from fixed-wing aircraft. Radio signals were detected using a scanning receiver (Telonics, Mesa, AZ) with antennas mounted on each wing. Flights were con- ducted an average of 3.5 d apart {N = 38 interflight times, range 1-10 d) between 18 August through 24 December; they were conducted an average of 11.8 d apart (N =14 interflight times, range 1-33 d) between 24 December and 9 June. When birds were located, the aircraft circled at approximately 150 m above the ground while coordinates of the relocation were determined using the airplane’s LORAN navigational system. Only the bird’s general movements were needed for this study so the accuracy of relocations was not determined. Habitat characteristics were not quantified at bird relocations, but general forest types were noted from the aircraft. Results and Discussion Female 1 left her nest area between 26 August and 1 September, approximately 50 d after her young fledged. On 2 September she was relocated approx- imately 65 km south of her nest near Steamboat Springs, Colorado (Fig. 1). The bird remained in this general vicinity from 2 September to 27 October. The forest vegetation of this stop-over area was pri- marily aspen with scattered spruce fir and lodgepole pine groves. A snowstorm between 3-9 November that deposited approximately 28 cm of snow (Steam- boat Springs, GO weather station. National Oceanic and Atmospheric Administration 1992a) apparently caused the bird to move further south. On 4 No- vember, Female 1 was relocated approximately 70 km to the south at an elevation of 3048 m. She continued south and spent the entire winter (8 No- vember 1992 to 12 March 1993) on forested lands between Rifle, Colorado and approximately 48 km to the east near Glenwood Springs, Colorado. The elevation of this area ranged from 2590-2960 m; the dominant forest-cover type of her wintering area was aspen with mixed conifer stands. On 1 2 March 1 993, she was still in the Glenwood Springs area. We were unable to document her return travel route but we did relocate the bird near her 1992 nest on 23 March 1993. Female 2 was relocated during six flights between 1 8 August to approximately 6 September in her nest area. On 10 September she moved approximately 6 km south into a drainage; between 10-28 September she was relocated in the same area seven additional times. On 2 October, she was relocated 28 km south of her nest, and by 14 October she was relocated in a mountain range approximately 140 km south of her nest (Fig. 1). The forest in this area was large contiguous blocks of spruce-fir and lodgepole pine stands. She was relocated during six flights in this same area through 27 October. The same snowstorm from 3-9 November that may have caused Female 1 to move south presumably also caused Female 2 to move from this mountain range. When conditions permitted, forested lands within approximately 40 km of the bird’s last location were searched during three subsequent flights (4, 6, 8 November); this bird was never relocated during the remainder of the winter. On 13 March 1993, Female 2 was re- located near the Wyoming- Colorado border ap- proximately 40 km south of her nest area. The radio signal suggested she was flying, presumably mi- grating back to her nesting territory. She was ob- served back at her nest area on 4 April. From 18 August to 6 September, Male 1 was relocated during six flights in its immediate nest area. From 8 September through 12 October, this bird continued to associate with the nest area but the 13 relocations obtained during this period sug- gested his movements were more extensive, fre- quently ranging 5-10 km from the nest. Twelve surveys between 15 October to 25 November, in- dicated that Male 1 shifted his primary activity area south approximately 8 km. The forest vegetation of this use area was primarily mixed aspen and lodge- pole pine. On approximately 30 November, this male began moving west southwest along a river drainage (Little Snake River) near Baggs, Wyoming (Fig. 1). From 1 December through 24 December, Male 1 was relocated during five surveys along the same drainage approximately 10 km west of Baggs, Wy- oming in an area approximately 65 km from the bird’s nest. Dominant vegetation along this river consisted of small groves (approximately 3 ha) of cottonwood {Populus spp.) surrounded by open sage- brush-wheatgrass prairies. On 24 December, the carcass of Male 1 was re- covered in open sagebrush habitat approximately 40 m from the nearest cottonwood grove. A necropsy by the Wyoming State Veterinary Laboratory, Lar- amie, Wyoming, revealed the bird was killed by a very hard blow from a blunt object. There was acute hemorrhaging under the right wing. Ribs on both March 1995 Winter Movements of Goshawks 7 Figure 1. Winter movements of adult northern goshawks that nested (from four separate pairs) on the Medicine Bow National Forest, Wyoming {N = number of relocations, A = may equal more than one relocation). sides were broken and one punctured the right ven- tricle of the heart. The bird’s neck was also broken. Both golden eagles {Aquila chrysaetos) and bald ea- gles (Haliaeetus leucocephalus) are abundant in this area and peregrine falcons (Falco peregrinus) and gyrfalcons (F. rusticolus) winter in Wyoming (Wy- oming Game and Fish Dept. 1992). Possibly, a strike from one of these raptors was responsible for this mortality but the carcass was not eaten and talon marks were not present. It is also possible the bird collided into the ground. There were no obstructions (trees, powerlines) in the recovery area except for sagebrush that are less than 50 cm tall. Male 2 was relocated three times between 18-28 August in its general nest area. On 2 September, he was relocated approximately 1 7 km south of its nest. The next survey on 4 September was conducted in inclement weather and the bird had returned to its nest area. On 6 September, the bird was relocated 13 km south of the nest and was apparently begin- ning its winter migration. On 10 September, Male 2 was relocated 70 km south of its nest in a wilderness area in Colorado (Fig. 1). The bird was near a high alpine lake at an elevation of 3316 m. We were not able to locate this bird again throughout the re- mainder of the winter. In the spring (12 April 1993), 8 John R. Squires and Leonard F. Ruggiero VoL. 29, No. 1 Male 2 was relocated approximately 10 km from the previous year’s nest site and remained on the forest throughout the spring until his radio failed. We searched extensively for the two birds (Female 2, Male 2) which we lost during their fall migration. During a 16-hr flight conducted over a 2-d period, we searched all major mountain ranges in Colorado, extending as far south as Santa Fe, New Mexico, for the lost birds. Mountain ranges were searched from an elevation of approximately 4270 m; this elevation enabled us to receive signals from approxi- mately 80 km if the birds were approximately line- of-sight from the airplane. No birds were located during this flight. Although it is possible that the lost birds remained in northern Colorado in topog- raphy that blocked radio signals, we think this is improbable given the frequency and number of flights that were conducted over this area throughout the winter. Results from this study suggest that goshawks nesting in southcentral Wyoming migrate during the winter. Three of the four birds migrated in a pri- marily southerly direction, whereas one bird mi- grated west southwest. Our results also indicate that goshawks begin winter movements in early fall (pri- marily mid-September) while weather conditions are moderate. The average high temperature during September was 22.5°C and the average nightly low was 4.6®C (Saratoga, WY weather station. National Oceanic and Atmospheric Administration 1992b). Daily high temperatures were all above 17.2“C. Pre- cipitation only totaled 0.51 cm for the month. Two birds (Female 1, Female 2) remained in areas along their migration route for up to several weeks before continuing their southerly movements. Inclement weather may have initiated continued migratory movements since both females moved in response to the same snowstorm. All birds returned to their nests from wintering areas between 23 March and 12 April. This suggests that logging, timber marking or other forms of human disturbance, in the Rocky Mountains, should be curtailed by early spring to avoid disturbing returning birds that may be in- volved in courtship and nest building. It is puzzling why Female 1 would migrate 185 km south of her nest (2500 m elevation) and then winter in Colorado at a higher elevation (2774 m). Equally high elevations are available immediately adjacent to her nest. We were unable to determine prey abundance on wintering areas and it is un- known whether prey abundance may explain the movement patterns we observed. Further research is needed to determine the extent of winter migrations of goshawks that nest in the Rocky Mountains and to identify habitat characteristics that are important in their winter habitat selection. Although our sam- ple size is small, these results suggest to wildlife managers that some goshawk populations in the Rocky Mountains are migratory; efforts to manage this species need to consider both wintering and nest- ing habitat requirements. Acknowledgments We acknowledge J. Ramsey for his help trapping gos- hawks. We thank D. France, Rawlins, Wyoming, for pro- viding safe and reliable monitoring flights. Support and cooperation were provided by the Rocky Mountain Region (Region 2) of the National Forest System. Literature Cited Alaska Department of Fish and Game Division of Wildlife Conservation. 1993. A summary of sur- vey, radio-telemetry, and other results regarding gos- hawk field studies in southeast Alaska, Ketchikan For- est Raptor Study Final Report. USDA For. Serv., Regional Office, Juneau, AK U.S.A. Alexander, R.R., G.R. Hoffman and J-M. Wirsing 1986. Forest vegetation of the Medicine Bow National Forest in southeastern Wyoming; a habitat type clas- sification. USDA For. Serv. Res. Paper RM-271, Rocky Mountain Forest Range Exper. Sta., Fort Collins, CO U.S.A. Beebe, F.L. and H.M. Webster. 1976. North Amer- ican falconry and hunting hawks. North American Fal- conry and Hunting Hawks, Denver, CO U.S.A. Doerr, P.d. and J.H. Enderson. 1965. An index of abundance of the goshawk in Colorado in the winter. Auk 82:284-285. Kenward, R.E., V. Marcstrom and M. Karlbom 1981. Goshawk winter ecology in Swedish pheasant habitats. J. Wildl. Manage. 45:397-408. Marcstrom, V. and R. Kenward. 1981. Movements of wintering goshawks in Sweden. Swedish Wildl. Res 12:1-36. Marston, R.A. and D.T. Clarendon. 1988. Land system inventory of the Medicine Bow Mountains and Sierra Madre Mountains, Medicine Bow National Forest, Wyoming. USDA For. Serv. Res. Paper MBNF-88-01. Medicine Bow National Forest, Lar- amie, WY U.S.A. National Oceanic and Atmospheric Administration. 1992a. Climatological Data, Colorado. Vol. 97(11). . 1992b. Climatological Data, Wyoming. Vol. 101 (9-10). Opdam, P., j. Thissen, P. Verschuren and G. Mukens. March 1995 Winter Movements of Goshawks 9 1977. Feeding ecology of a population of goshawk Accipiter gentilis. J. Ornithol. 118:35-51. Rosenfield, R.N., AND J. Bielefeldt. 1993. Trapping techniques for breeding Cooper’s hawks. J. Raptor Res. 27:171-172. WidEn, P. 1985. Breeding and movements of goshawks in boreal forest in Sweden. Holarctic Ecol. 8:273-279. . 1987. Goshawk predation during winter, spring, and summer in a boreal forest area of central Sweden. Holarctic Ecol. 10:104-109. . 1989. The hunting habitats of goshawks Accip- iter gentilis in boreal forests of central Sweden. Ibis 13T 205-231. Wyoming Game and Fish Department. 1992. Wy- oming bird and mammal atlas. Wyoming Game and Fish Dept., Cheyenne, WY U.S.A. Received 13 June 1994; accepted 8 October 1994 J Raptor Res. 29(1);10-14 © 1995 The Raptor Research Foundation, Inc. PREY OF NESTING BALD EAGLES IN TEXAS David W. Mabie Texas Parks and Wildlife Department, 715 S. Highway 35, Rockport, TX 78382 U.S.A. M. Todd Merendino Texas Parks and Wildlife Department, Matagorda County Courthouse, Bay City, TX 77414 U.S.A. David H. Reid Texas Parks and Wildlife Department, Rt. 3 Box 247, Bay City, TX 77414 U.S.A. Abstract. — Food habits of nesting bald eagles (Haliaeetus leucocephalus) in Texas were assessed by examining prey remains collected from within and beneath nests. We collected and identified 661 prey items from 27 nesting territories. Nesting bald eagles appeared to be opportunistic feeders and their diets contained nearly equal proportions of birds (33.7%), reptiles (30.7%), and fish (30.1%); American coots (Fulica americana), softshell turtles (Apalone spp.), and freshwater catfish (Ictalurus spp. and Noturus spp.) dominated the respective food categories. The percentage of reptile remains in bald eagle diets is the highest reported in North America. Protection of traditional foraging areas is necessary to provide for an increasing bald eagle population in Texas. Key Words: bald eagle; food habits; Haliaeetus leucocephalus; nest site; prey; Texas. Presas de Haliaeetus leucocephalus nidificantes en Texas Resumen. — Habitos alimentarios de Haliaeetus leucocephalus nidificantes en Texas fueron estudiados a traves del examen de restos de presas colectados en los nidos y alrededores. Colectamos e identificamos 661 categorias presas en 27 territorios de nidificacion. Los individuos de H. leucocephalus nidificantes parecen ser oportunistas y sus dietas contienen proporciones semejantes de aves (33.7%), reptiles (30.7%) y peces (30.1%); Fulica americana, Apalone spp., y los peces Ictalurus spp. y Noturus spp., dominaron las respectivas categorias alimentarias. El porcentaje de restos de reptiles en la dieta de H. leucocephalus es la mas aha reportada en Norteamerica. La proteccidn de areas tradicionales de forrajeo es necesaria para un incremento de las poblaciones de H. leucocephalus en Texas. [Traduccidn de Ivan Lazo] Bald eagles {Haliaeetus leucocephalus) take a di- verse array of prey, Stalnaaster (1987) reviewed 20 food habits studies and found that fish, birds, and mammals comprised 56%, 28%, and 14%, respec- tively, of the bald eagle’s overall diet. Although bald eagle food habits are well documented in many areas of the United States and Canada (Lincer et al. 1979), no food habits data exist for bald eagles nesting in Texas. The bald eagle population in Texas is in- creasing, and knowledge of food habits is important to identify potential management problems, limiting factors associated with food availability, environ- mental contamination, and changes in land-use prac- tices. Our objective was to determine prey species composition and percent occurrence for bald eagles nesting in Texas. Methods This study was conducted in 16 of 51 counties consti- tuting the bald eagle nesting range in Texas (Fig.l). From February through May 1985-91, food remains were col- lected from within and beneath nests representing 27 nest- ing territories. Most food debris were collected from the nest bowl; food remains were usually scarce or absent around the base of nest trees. Field methods were after Mollhagen et al. (1972), Dunstan and Harper (1975), Todd et al. (1982), and Dugoni et al. (1986), except that prey biomass was not measured. Bones, fish scales, turtle shells, feathers, and partially eaten prey were identified in the field or collected for later identification. Whole or partially eaten food items were identified in the field and returned to the nest. Blue catfish {Ictalurus furcatus), chan- nel catfish (I. punctatus), and madtoms {Noturus spp.) were collectively called “catfish” due to the difficulty in accu- rately identifying skulls and bones when only those items 10 March 1995 Prey of Nesting Bald Eagles in Texas 11 Figure 1. Breeding range of the bald eagle in Texas and counties from which food habits data were obtained. were present. Also, we did not distinguish between eastern cottontail {Sylvilagus Jloridanus) and swamp rabbit (5. aquaticus) remains. All remains were identified to species or classified as either bird, mammal, fish, or reptile. Per- cent composition of prey was calculated as a portion of the total number of individual prey items collected from all nest sites. Results and Discussion We identified 661 prey items representing 46 ver- tebrate species (Table 1). Nesting bald eagles ap- peared to be opportunistic feeders and their diets contained nearly equal proportions of birds (33.7%), 12 Mabie et al. VoL. 29, No. 1 Table 1. Food items identified from 27 bald eagle nests in Texas, 1985-91. Prey N %N Birds American coot {Fulica americana) 132 20.0 Snow goose {Chen caerulescens) 26 3.9 Northern shoveler (Anas clypeata) 12 1.8 Black-bellied whistling-duck (Dendrocygna autumnalis) 10 1.5 Cattle egret (Bubulcus ibis) 7 1.1 Blue-winged teal (Anas discors) 5 tr.^ Wood duck (Aix sponsa) 4 tr. American wigeon (Anas americana) 3 tr. Eastern meadowlark (Sturnella magna) 3 tr. Brown-headed cowbird (Molothrus ater) 3 tr. Northern pintail (Anas acuta) 3 tr. Greater white-fronted goose (Anser albifrons) 3 tr. American bittern (Botaurus lentiginosus) 2 tr. Gad wall (Anas strepera) 2 tr. Northern flicker (Colaptes auratus) 1 tr. White ibis (Eudocimus albus) 1 tr. Northern bobwhite (Colinus virginianus) 1 tr. Redhead (Aythya americana) 1 tr. Northern harrier (Circus cyaneus) 1 tr. Unidentified cormorant (Phalacrocorax spp.) 1 tr. Green-winged teal (Anas carolinensis) 1 tr. Unidentified duck (Anas spp.) 1 tr. Reptiles Softshell turtle (Apalone spp.) 182 27.5 Mississippi map turtle (Graptemys kohni) 6 tr. Razorback musk turtle (Kinosternon carinatus) 6 tr. Red-eared slider (Trachemys scripta) 5 tr. Common musk turtle (Kinosternon odoratus) 3 tr. Ornate box turtle (Terrapene ornata) 1 tr. Fish Catfish (Ictalurus spp. and No turns spp.) 129 19.5 Carp (Cyprinus carpio) 40 6.0 Crappie (Pomoxis spp.) 16 2.4 Largemouth bass (Micropterus salmoides) 6 tr. Gar (Lepisosteus spp.) 3 tr. Gizzard shad (Polydactylus cepedianom) 3 tr. Striped bass (Morone saxatilis) 1 tr. Unknown fish 1 tr. Mammals Eastern cottontail (Sylvilagus floridanus) and swamp rabbit (.S’, aquaticus) 23 3.5 Eastern fox squirrel (Sciurus niger) 3 tr. Opossum (Didelphis virginiana) 3 tr. Nine-banded armadillo (Dasypus novemcinctus) 2 tr. Striped skunk (Mephitis mephitis) 1 tr. Plains jxjcket gopher (Geomys bursarius) 1 tr. Feral hog (Sus scrofa) 1 tr. Hispid cotton rat (Sigmodon hispidus) 1 tr. Black-tailed jackrabbit (Lepus californicus) 1 tr. tr. = <1.0%. March 1995 Prey of Nesting Bald Eagles in Texas 13 Table 2. Percent composition of major food items of nesting bald eagles from North America. Location N Nests Examined® Fish Birds Mammals Reptiles Alaska, Aleutian Islands^ 28 6.1 86.0 7.6 0.0 Washington‘S 18 71.0 26.1 2.0 0.0 Minnesota'* 6 90.1 7.9 1.3 0.0 Florida^ 16 78.4 17.3 3.4 0.9 Maine (interior)*^ 31 76.7 16.5 6.8 0.0 Maine (coastal)* 45 17.1 75.7 6.9 0.0 Louisiana^ 10 41.6 42.4 15.6 0.4 Arizona** 11 76.5 11.0 11.9 0.6 California' 8 87.0 9.0 4.0 0.0 Nova Scotiai 76 65.0 24.0 11.0 0.0 Montana** — 28.0 55.0 17.0 0.0 “ In all studies, prey remains were collected from within or beneath eagles returning to nests with prey in California. ^ Murie (1940). Watson et al. (1991). Dunstan and Harper (1975). ' McEwan and Hirth (1980). f Todd et al. (1982). nests. Hunt et al. (1992) also conducted some direct observations of 8 Dugoni et al. (1986). ^ Haywood and Ohmart (1986). ‘ Hunt et al. (1992). j Cash et al. (1985). ** Swenson et al. (1986:31-35). reptiles (30.7%), and fish (30.1%); mammals com- prised 5.5% of prey remains. Our objective was to assess prey species composition and percent occur- rence by number, and we did not quantify biomass of the various prey. Given the preponderance of smaller prey items in the diet of nesting bald eagles in Texas, it is doubtful if estimates of biomass would change the rank importance of prey classes (e.g., bird, reptile, fish, mammal) in the diet (McEwan and Hirth 1980, Haywood and Ohmart 1986, Hunt et al. 1992). Bird Prey. Bird remains were found in 92% of the nests. Twenty-one species of birds were found with American coots {Fulica americana) being most common (Table 1). American coots were also the most abundant bird species in bald eagle diets in Florida (McEwan and Hirth 1980), Louisiana (Du- goni et al. 1986), and Arizona (Haywood and Ohmart 1986). Snow geese {Chen caerulescens), northern shoveler {Anas clypeata), and black-bellied whis- tling-ducks {Dendrocygna autumnalis) were the most common waterfowl species taken (Table 1). Bald eagles were commonly observed feeding on crippled or diseased geese and ducks in rice fields in the study area. Throughout the bald eagle’s nesting range, birds comprise significant portions of the diet when such species are abundant (Table 2). Reptile Prey. The proportion of reptiles in our results is the highest reported for bald eagles in North America. Studies across the bald eagle’s range indicate that reptiles comprise <1% of the diet (Ta- ble 2). Reptile remains were found in 41% of nests visited. Six species of turtles were found with soft- shell turtles {Apalone spp.) being most common (Ta- ble 1). Many nests contained >10 softshell turtle shells and two nests contained >20 shells. Turtle shells were consistently found in nests that were associated with the Colorado, Brazos, and Trinity rivers. Haywood and Ohmart (1986) indicated that some physical characteristics of a river (e.g., sand- bars, riffles, etc.) exposed benthic feeding fish (i.e., catfish) to the surface, thus making them more vul- nerable to aerial predation. This may also hold true for softshell turtles which bask or forage (Leviton 1972) in shallow water or on sandbars (Garrett and Barker 1987). Fish Prey. Fish remains were found in 83% of the nests visited. Seven species of fish were found with freshwater catfish and carp {Cyprinus carpio) being most common (Table 1). Our results are con- sistent with other studies in that catfish were the major fish eaten by bald eagles in the southern Unit- ed States (Bent 1937, Broley 1947, McEwan and Hirth 1980, Dugoni et al. 1986, Haywood and Ohmart 1986). In contrast to our results for southern nesting bald eagles, fish comprised 78% of the diet in Florida (McEwan and Hirth 1980; Table 2). Mammal Prey. Remains of nine mammal species 14 Mabie et al. VoL. 29, No. 1 were found in 33% of nests visited with eastern cot- tontail and swamp rabbits being most common (Ta- ble 1). Rabbits were also common food items in Arizona (Haywood and Ohmart 1986) and Florida (McEwan and Hirth 1980). Retfalvi (1970) re- ported that rabbits were not observed being killed by bald eagles, but rather that bald eagles scavenged rabbit carcasses along roadsides and in fields. Portions of larger prey items (e.g., white-tailed deer, Odocoileus virginianus) lacking fur or bones would be undetectable due to total digestion of the meat portion. We feel, however, that large prey items were probably a minor part of the diet of nesting bald eagles in Texas and are probably obtained op- portunistically while searching for more available prey (birds, reptiles, fish). Overall, mammals are not generally a common prey item of nesting bald eagles (Table 2). Conclusions. Food supply is critical in the estab- lishment and maintenance of breeding bald eagle populations (Dzus and Gerrard 1993). As in other areas, nesting bald eagles in Texas appear to be opportunistic feeders; in contrast to other areas, a high percentage of reptiles were consumed. At pres- ent, food availability does not appear to be a limiting factor in the maintenance or expansion of bald ea- gle’s nesting in Texas. The major prey of nesting bald eagles in Texas are associated with wetland habitats and these areas should be managed to pre- vent or minimize degradation. Acknowledgments Data for this study were collected during a 7-yr banding study funded by Federal Aid Project W-125-R, Job 30, and the Texas Parks and Wildlife Department (TPWD). We thank J. Alexander, D. Bujnoch, B. Carroll, M. Hob- son, R. Jurries, M. Mitchell, K. Powell (deceased), L. Reinecke, L. Schatz, E. Stancik, and TPWD personnel of the Pineywoods District for their assistance in collection of food items. We thank R. George, D. Frels, L. Linam and B. Ortego for helpful comments on the manuscript. We are especially thankful to the many private landowners who graciously allowed us access to their properties. Literature Cited Bent, A.C. 1 937. Life histories of North American birds of prey. Part 1. U.S. Natl. Mus. Bull. 167. Broley, C.L. 1947. Migration and nesting of Florida bald eagles. Wilson Bull. 59:3-20. Cash, K.J., P.J. Austin-Smith, D. Banks, D. Harris and P.C. Smith. 1985. Food remains from bald eagle nest sites on Cape Breton Island, Nova Scotia. J. Wildl. Manage. 49:223-225. Dugoni, J.A., P.J. Zwank and G.C. Furman. 1986. Foods of nesting bald eagles in Louisiana. Raptor Res 20:124-127. Dunstan, T.C. and J.F. Harper. 1975. Food habits of bald eagles in north-central Minnesota. J. Wildl. Manage. 39:140-143. Dzus, E.H. and J.M. Gerrard. 1993. Factors influ- encing bald eagle densities in northcentral Saskatche- wan. /. Wildl. Manage. 57:771-778. Garrett, J.M. and D.G. Barker. 1987. A field guide to reptiles and amphibians of Texas. Texas Monthly Press, Austin, TX U.S.A. Haywood, D.D. and R.D. Ohmart. 1986. Utilization of benthic-feeding fish by inland breeding bald eagles. Condor 88:35-42. Hunt, W.G., J.M. Jenkins, R.E. Jackman, C.G. The- LANDER AND A.T. Gerstell. 1992. Foraging ecology of bald eagles on a regulated river. /. Raptor Res. 26: 243-256. Leviton, A.E. 1972. Reptiles and amphibians of North America. Doubleday and Company, Inc., Garden City, NY U.S.A. Linger, J.L., W.S. Clark and M.N. LeFranc. 1979. Working bibliography of the bald eagle. Natl. Wildl. Fed. Sci. Tech. Ser. No. 2. Washington, DC U.S.A. McEwan, L.C. and D.H. Hirth. 1980. Food habits of the bald eagle in north-central Florida. Condor 82: 229-231. Mollhagen, T.R., R.W. Wiley and R.L. Packard. 1972. Prey remains in golden eagle nests: Texas and New Mexico. J. Wildl. Manage. 36:784-792. Murie, O.J. 1940. Food habits of the northern bald eagle in the Aleutian Islands, Alaska. Condor 42:198- 202 . Retfalvi, L. 1970. Foods of nesting bald eagles on San Juan Island, Washington. Condor 72:358-361. Stalmaster, M.V. 1987. The bald eagle. Universe Books, New York, NY U.S.A. Swenson, J.E., K.L. Alt and R.L. Eng. 1986. Ecology of bald eagles in the Greater Yellowstone ecosystem. Wildl. Monogr. 95. Todd, C.S., L.S. Young, R.B. Owen, Jr. and F.J Gramlich. 1 982. Food habits of bald eagles in Maine. J. Wildl. Manage. 46:636-645. Watson, J.W., M.G. Garrett and R.G. Anthony. 1991. Foraging ecology of bald eagles in the Columbia River estuary. J. Wildl. Manage. 55:492-499. Reeeived 2 April 1994; accepted 6 October 1994 J. Raptor Res, 29(l):15-25 © 1995 The Raptor Research Foundation, Inc. WHAT IS Falco altaicus MENZBIER? David H. Ellis National Biological Survey, Patuxent Environmental Sciences Center, Laurel, MD 20708 U.S.A. Abstract. — The systematics of the Altay falcon {Falco altaicus /lor enzi) remains enigmatic. First reported in 1811, it has been treated as a gyrfalcon {F, rusticolus), a saker (F. cherrug), and two separate species {F. lorenzi and F. altaicus). Of 53 “altaicus” specimens examined, at least two are misidentified gyrfalcons, many are typical sakers, but 34 (the core group) are considered to be the true Altay falcon type. Adults have red, brown, and gray color morphs. The red (backed) morph closely resembles some eastern sakers; the chocolate and gray morphs resemble respective gyrfalcon morphs. While the true affinities of the Altay falcon will be resolved by molecular genetics, the ecological, geographical, and morphological information suggest that the core group represents a gyrfalcon- saker cross that is being swamped through back crosses with the saker. The breeding range of the core group (i.e., the Altay and Sayan Mountains) is much smaller than previously reported. Key Words: Altay falcon; Asia; Falco altaicus; gyrfalcon; saker; Siberia. ^Que es Falco altaicus Menzbier? Resumen. — La sistematica de Falco altaicus /lorenzi se mantiane en el enigma. Reportado primero en 1811, y despues fue tratado como F. rusticolus, como F. cherrug, y dos especies separadas {F. lorenzi y F. altaicus). De 53 especimenes de “altaicus”, al menos dos son F. rusticolus mal identificados, muchos son tipicos F. cherrug, pero 34 (grupo principal) son considerados como verdaderos halcones Altay. Los adultos poseen fase de color rojo, cafe y gris. La fase de dorso rojo es bastante parecida a algunos F. cherrug del este; las fases chocolate y gris son parecidas a las respectivas fases de F. rusticolus. Mientras que las verdaderas afinidades del halcon Altay seran resueltas por la genetica molecular, la informacion ecologica, geografica y morfologica sugiere que el grupo principal representa hibridos de F. rusticolus y F. cherrug. El rango reproductive del grupo principal (i.e., Montanas Altay y Sayan) es mucho mas pequeno que el previamene reportado. [Traduccion de Ivan Lazo] The existence of a gyrfalcon-like {Falco rusticolus) bird from southcentral Siberia and Central Asia is beyond dispute. Some museum specimens labeled Altay falcon {F. altaicus and F. lorenzi) are so unlike sakers {F. cherrug) that Menzbier (1891, 1901) and Sushkin (1938) assigned them separate species sta- tus. Dementiev (1951) and Brown and Amadon (1968:840, 843) presented body measurements for these birds that would categorize them as large gyr- falcons. However, the major problem in defining an altaicus/lorenzi taxon results from the existence of an almost uninterrupted continuum from the most gyrfalcon-like to the most saker-like specimens (Figs. 1-5). Recent works (Brown and Amadon 1968, Baumgart 1978, Cade 1982) have dismissed the al- taicus/lorenzi problem by relegating the bird to either a subspecies or a color morph of the saker. Even Dementiev, who for so long argued that Altay falcons were closer to gyrfalcons than sakers, eventually con- cluded that both altaicus and lorenzi were synony- mous with the saker (Dementiev and Shagdarsuren 1964). However, a few specimens labeled Altay fal- con (mostly those originally labeled lorenzi) are in- distinguishable from gray-morph gyrfalcons. Several papers have treated Altay falcon system- atics (Dementiev 1933a, 1947, 1951, Kots 1948, Vaurie 1961, Dementiev and Shagdarsuren 1964, Baumgart 1980, 1991). Dementiev (1933a) cited 53 publications in his monograph. Pfeffer (1987:23) and Walton et al. (1991) referred to the confusion surrounding the bird. Because of the misinformation and confusion in the literature, it is important to identify those specimens that are most likely to be useful in correctly defining Falco altaicus by means of molecular genetics. Historical Perspective. The image of the Altay falcon was reportedly borne on the shields of the armies of Attila (Schenk 1935/38, Dementiev 1951: 141). Tamerlane, and even the sons of Genghis Khan, reportedly hunted swans with this falcon (Demen- tiev 1951:144). Such romantic notions are compel- ling, but how can we be certain that it was the Altay 15 16 David H. Ellis VoL. 29, No. 1 falcon (rather than the saker or the gyrfalcon) that the Huns and Mongols retained for centuries in their cultural memory? Initially mentioned in a scientific context by Pallas (1811), the first Altay falcon specimen was collected in 1840 (Fig. lA), and the second in 1874. Based on the first specimen and a fledged juvenile collected in 1879, Menzbier (1891) described a new species, Hierofalco altaicus. Later, he examined three gyrfal- con-like birds collected in fall and winter in southern Siberia and thought them distinct enough that he named them H. lorenzi (Menzbier 1901). By the time he wrote his monograph on the large falcons of Russia, Menzbier (1916, in Dementiev 1933a: 137) had six lorenzi and ten altaicus specimens. De- mentiev (1933a) used 34 specimens for his analysis. The Altay Falcon Confusion. The Altay falcon reportedly inhabits high elevations of Central Asia from the Sayan and Altay Mountains in the north to the Tien Shan Mountains in the south and as far southwest as the Alexandrovski Mountains in Tur- kestan (Dementiev 1933b, Stephnyan 1990). Later authors reported it breeding east to Lake Baikal (Johnson 1956, in Dementiev 1960), and one of the lorenzi cotypes (Fig. 5G) was taken in late autumn near the southern end of the Ural Mountains. Other areas of confusion are habitat preference and plumage. The Altay falcon reportedly prefers alpine tundra or tundra-like montane steppe, with the saker occupying lower elevations (Sushkin 1938). The original adult lorenzi specimens (Fig. 5C and D) and two birds from Sushkin’s family (Fig. 4C, 4F) resemble adult gray gyrfalcons in plummage. Dementiev first wrote of only two forms, light and dark (1933a, 1951). Strangely however, in the “dark form” he included the lorenzi types (e.g., Fig. 4C, 4F) that are as light as his light or red form (Fig. 4B). Later, Dementiev and Gladkov (1951 [1966, 1:136]) more accurately described three adult forms: the chocolate, the red-backed, and the gray. Polymorphism was further confused when De- mentiev (1947, 1951) observed that the Altay falcon was polymorphic while the saker was not. Platt (1983), however, described four saker color morphs in Pakistani hawk markets, including a chocolate form, and Baumgart (1978) reported gray, brown, and rufous saker morphs breeding in central Mon- golia. Using the most unique Altay falcon specimens, I redefine the range of the Altay falcon, provide a more accurate estimate of the size of this falcon, compare the ecological similarities between the Altay falcon and sympatric sakers, and consider the probable or- igins of the Altay falcon. Methods Altay falcons (i.e., specimens labeled lorenzi or altaicus) were measured (wing chord and tail), aged, and photo- graphed in the only two sizable collections (ZIAS, 26 specimens; and University of Moscow Zoological Museum [UMZM], 25 specimens), as were single skins from the British Museum (BM) and the American Museum of Natural History (AMNH). Hundreds of sakers and gyr- falcons were also compared with the Altay falcons. All specimens labeled Altay falcon, and a few altaicus sakers were assigned to one of 19 morphological classes. Results and Discussion The Lorenzi /Altaicus Link. The link between lorenzi and altaicus was forged in 1914 when Sush- kin (1915 , in Dementiev 1933a) collected a family of what he thought were gyrfalcons in the Russian Altay Mountains. Both adults were shot and the five nestlings were taken into captivity (Sushkin 1938). The adult male and his five daughters (Fig. 4) even- tually came into the collection of the Zoological In- stitute of the Academy of Sciences (ZIAS), St. Pe- tersburg, Russia. The adult male (Fig. 4F) and one progeny (Fig. 4G) are unquestionably like some lor- enzi cotypes from southwestern Siberia (Fig. 5G, 5D), while three progeny (Fig. 4A, 4D, 4E) are of the dark altaicus type, thus linking lorenzi and al- taicus. If it were not for one of the progeny, I believe the Altay falcon would today be viewed as a disjunct relict subspecies of the gyrfalcon (i.e., F. rusticolus altaicus). The last bird, however, in adult plumage (Fig. 4B) is nearly identical to the red-backed morph of the saker, common in the Altay region. Differences between Altay Falcons and Sakers. Brown and Amadon (1968:840, 843) reported that the Altay falcon had longer wings than even the gyrfalcon (males, 367 mm vs. 361 mm; females, 403 mm vs. 396 mm). These Altay falcon values, how- ever, are likely simplified from Dementiev (1951: 21), whose comparisons, I believe, must be reex- amined for two reasons. First, Dementiev included in his sample the lorenzi birds, some of which I claim to be wintering gyrfalcons. Second, Dementiev’s (1933a) individual measurements for tail length ex- ceeded mine 16 of 16 times and by an average of 18.5 mm. For wing length, his values were greater in 10 of 19 cases (x = 9 mm). Only a small portion of these differences could be accountable to specimen shrinkage or by the difference between ehord vs. March 1995 Altay Falcon Review 17 Figure 1. Adult, brown morph Altay falcons, both from central Altay Mountains. Note extremely dark heads and tails. A: First (Nov. 1840) specimen collected (cotype, ZIAS 75486, female). B: Male collected Dec. 1916 (ZIAS 127701). flattened wing measurements. Both of these biases would exaggerate the size of the Altay falcon. Sushkin (1915, in Dementiev 1933a: 158) main- tained that Altay falcons were more powerfully built than similar-sized sakers. Differences in relative build should be evident by comparing mass with linear measurements. However, only three weights are available for birds in the core Altay falcon subsam- ple. Two females weighed 1050 g (juvenile, UMZM 58635, collected in September) and 990 g (second year, UMZM 58642, collected in May). A juvenile male (AMNH 648864, collected in July) weighed 805 g. These values are smaller than gyrfalcon val- ues from Brown and Amadon (1968:843). Altay falcons are reportedly gyrfalcon-like with Figure 2. Dark flecking in light bars is considered a gyrfalcon trait, especially evident in adult gyrfalcons (above) and gray Altay falcons. tarsi more than one-half feathered (Dementiev 1 933a: 157). However, I detected extensive overlap between gyrfalcons, Altay falcons, and sakers for this trait. The traits I believe best characterize the plumage of the three taxa are presented in Table 1. To this point, my discussion seems to undermine the hy- pothesis that the Altay falcon is a gyrfalcon. How- ever, it is clear that the Altay falcon more closely resembles the gyrfalcon than the saker (Table 1). Figure 3. Unusual patterns in tail barring and spotting for juvenile gyrfalcons (A, B) and sakers (C, D). VoL. 29, No. 1 Figure 4. Family of Altay falcons collected by Sushkin in June 1914 in the southwestern Altay Mountains. Adult male (F) was shot and five siblings were retained alive. Specimen E was sacrificed in autumn 1914 to document juvenile plumage. Other specimens were preserved as they died. A. ZIAS 127699, second year female, chocolate morph. B. ZIAS 127704, sixth year female, red (backed) morph. G. ZIAS 127703, sixth year female, gray morph. D. ZIAS 127702, fifth year female, brown morph. E. ZIAS 127698, Juvenile (first year) female. F. ZIAS 127697, adult male, gray morph. Figure 5. Four adult, gray morph, gyrfalcons. A and B are females from breeding areas in northern Siberia. C (ZIAS 75497) and D (ZIAS 75494) are cotypes of F. lorenzi. C is a female from near Kurgan just southeast of the Ural Mountains. D is a male from western Siberia. 20 David H. Ellis VoL. 29, No. 1 Table 1. A comparison of color traits of adult gyrfalcons, sakers, and Altay falcons of equivalent general color saturation. Topographic Region Gyrfalcon Expression"* Altay Falcon Expression^ (Ally)^ Saker Expression^ Head Slightly lighter As dark as (A)'^ Much lighter Malar stripe Light or diffuse Light or diffuse (G)'" Dark but narrow Cheek Darker As dark as (G)'" Lighter Superciliary line Ill-defined Obscure or ill-defined (G)=-d Well-defined Dark flecking in light Pronounced and Pronounced but fine (G, Rare (western) or sel- bars on primaries and rectrices coarse eastern S)*^ dom present but fine (eastern) Breast Heavily spotted Heavily spotted (G)*^ Lightly spotted Flank Heavily barred Heavily barred (G)'^ Bars mostly lacking (western) to promi- nent (eastern) but seldom as bold as in gyrfalcons Under-tail coverts Heavily barred Heavily barred (G)*" Lightly barred Tail pattern Barred Barred (G and eastern S)^ Spotted (western) to barred (eastern) Tail darkness As dark as or slight- ly lighter Tail as dark as dorsal plumage (G)*^ Lighter ^ Comparison is with general body color (e.g., head lighter than dorsum). ^ Ally used here to indicate whether a particular Altay falcon trait is gyrfalcon-like (G), saker-like (S), or unique to the Altay falcon (A) Feature is well pronounced in most adult Altay falcons. Dementiev (1933a;158) said that in the Altay falcon the eye stripe is brighter than for sakers. Sushkin’s juvenile (ZIAS 127698) seems to confirm this, but in most juvenile museum specimens, and probably in all adults, the eye stripe is less pronounced in Altay falcons than in sakers of comparable darkness. An important element of the gyrfalcon plummage (Table 1) is dark flecking (Fig. 2) in the light bars on wing and tail. This flecking appears to always be evident in all gray and chocolate Altay falcon adults. Flecking is little evident in red-backed Altays, seldom evident in eastern sakers, and almost never evident in western sakers. Head features (Table 1) also suggest gyrfalcon influence. Sakers have a clearly defined light super- ciliary line, a color saturated narrow malar stripe, and contrasting light and dark areas on the cheek. Adult Altay falcons, like adult gray gyrfalcons, have a more diffuse pattern of light and dark in these areas. The red morphs of Altay falcons and sakers are most alike. Dementiev (1933a:158) proposed that, when compared to red sakers, red Altay falcons have more black and less red on mantle, more spots on breast, more gray on upper tail coverts and rump, darker tail, and a less distinct and shorter malar stripe. By contrast, I see an uninterrupted continuum between the two forms, and the single red morph from the Sushkin family (Fig. 4B) has much less gray on the rump than many eastern sakers. Designating Key Specimens. Using traits in Ta- ble 1, I divided museum specimens into 11 color classes for each age group and taxon (Fig. 6). Molt- ing birds revealed that adults of all three taxa are normally one-half or one full cell lighter in Fig. 6 than their corresponding juvenile plumage. Because gyrfalcons winter south to the Altay Mountains (De- mentiev 1951), I classified those fall and winter spec- imens that appear identical to adult gyrfalcons, in- cluding Menzbier’s (1901) lorenzi cotypes (ZIAS 75494 and 75497; Fig. 5), as gyrfalcons. Red-backed and gray adults that exhibited dark flecking and other gyrfalcon or Altay falcon traits in Table 1, were classified Altay falcons as were all birds in the Sushkin family even though the red- backed female (Fig. 4B) is little different from some March 1995 Alt AY Falcon Review 21 Color Code 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6YRFALC0H Adult White Gray- white Gray Dark Gray Dark Streaked, Barred Black (Grayish) 75494 75497 Juvenile White Brown - white Light Brown Brown Dark Brown Black (Brownish) ALTAY FALCON Adult Red- backed Gray- brown Dark Gray Brown Dark Streaked, Barred Black (Brownish) 127704 75493 127697 127703 75488 75489 95287 127699 127702 127701 19 75486 75491 95290 Juvenile Brown Dark Brown B1 ack (Brownish) 21545 21607 75485 75490 75498 75499 75501 127698 58642 75492 75495 75496 75502 648864 75487 75500 95293 127700 58635 95281 SAKER Adult Blond Red- backed Gray- brown Brown 75530* 75570* 95286 95291 96907* 96958 96961* 97698* 168201* 95292 96939* Juvenile Blond Blond, Streaked Brown Dark Brown 95280 58637 58638 58641 95284 58636 58639 58640 69447 95282 95283 95285 95289. 96931 168208* Figure 6. A classification scheme for dividing 62 specimens (53 that bear an altaicus or lorenzi label and the nine sakers that most clearly display Altay falcon traits identified in Table 1) into gyrfalcon, Altay falcon and saker color classes. Specimens from ZIAS have prefixes 12, 16, and 75; those from UMZM bear prefixes 21, 58, 69, 95, 96, and 97; number 19 is from the BM; and 648864 is from the AMNH. Sakers marked ’ never bore the altaicus or lorenzi label. eastern sakers. Some Altay falcons (e.g., Fig. lA), are as dark as the so-called black gyrfalcon {F. r. obsoletus) from Labrador (Dementiev 1951). I ten- tatively classified all dark-headed or dark-tailed, chocolate juveniles as Altay falcons, and dark spec- imens with heads and tails lighter than their general color as sakers. The scheme in Fig. 6 is subjective, but useful in identifying the most important speci- mens for future molecular genetics work. As Cade (1982:82) noted, some juvenile sakers 22 David H. Ellis VoL. 29, No. 1 cannot be safely distinguished from some juvenile gyrfalcons. However, sakers tend to have round tail spots (Table 1) and tails lighter than their general body color, while gyrfalcon tails tend to be barred (Cade 1982:82, Baumgart 1980:20, 1991:36). For the extreme specimens in Fig. 3, the opposite appears true. Because of this overlap in tail pattern, the most taxonomically useful juvenile specimens are the darkest-headed and darkest-tailed birds because most of these molt into dark adults. Light-bellied juveniles were classed as sakers in Fig. 6. In Table 2, the size of four age and sex classes are compared for specimens identified in Fig. 6 as most distinctly Altay falcon (i.e., core group). De- letion of unsexed birds left sample sizes so small that conclusions are tentative. Averages for Altay falcons in Table 2 do not support that it is a large gyrfalcon as suggested by Brown and Amadon (1968:843). Adults were within, albeit at the low end of, gyr- falcon ranges while juvenile Altay falcons averaged smaller than gyrfalcons. It should be noted that the largest sakers also have wing and tail lengths similar to gyrfalcons (Brown and Amadon 1968). Character Displacement. Closely related taxa are usually most diflFerent ecologically and morpho- logically in their zone of sympatry. The literature advances the notion that the Altay falcon breeds at higher elevations than the saker (e.g., Sushkin 1938), but this assertion is not supported by the specimen data. For example, a fledgling (ZIAS 75487) Altay falcon was collected “near the city” of Krasnoyarsk (Dementiev 1933a: 152) which is only 400 m in el- evation. Another eyrie in southcentral Siberia was at 250 m elevation (Dementiev 1933a: 154) while the supposedly lower-elevation saker breeds up to 3400 m (Brown and Amadon 1968:842) and probably even higher in Tibet (G.M. White pers. comm.). Character displacement should also be evident in food habits. Interestingly, the distribution of both rock ptarmigan {Lagopus mutas) and willow ptar- migan {L. lagopus), important prey for the gyrfalcon worldwide (Johnson and Herter 1989:132), extend south into the Altay Mountains (Dementiev and Gladkov 1951 [1967, 4:46]). Unfortunately, few Al- tay falcon food habits data are available (Sushkin 1938:160), and there is anecdotal evidence from only a single eyrie in the Altay Mountains of ptarmigan being important prey (A. Sorokin pers. comm.). If the Altay falcon and sympatric sakers do not hybridize, character displacement predicts that sa- kers from Central Asia should be morphologically more different from Altay falcons than are distant populations of sakers. However, the reverse is true. Conclusions and Explanations for the Altay Falcon. I earlier concluded that at least some of the lorenzi adults are gyrfalcons (e.g.. Fig. 5C, 5D). I also concluded that some specimens labeled Altay falcon are sakers (Fig. 6). The simplest explanation of the remaining Altay falcon core group is that all are merely sakers, the darkest and grayest of which have been arbitrarily tagged Altay falcons because they fit the Altay falcon paradigm. This “saker morph” conclusion is generally accepted today (Cade 1982:80) without explaining the few misidentified specimens that are obviously wintering gyrfalcons. Also left unexplained is the remarkable similarity between some birds that breed in Central Asia (e.g.. Fig. 4F) and the gray morph of the northern gyr- falcon (compare Fig. 4F with Fig. 5B, 5D). Such individuals, I believe, provide the key to the origin of the true Altay falcon. Simply put, Altay falcons in the core group exhibit strong gyrfalcon influence because they are hybrids. Several lines of evidence support the hybrid hy- pothesis. From Table 1, the core Altay falcons ap- pear to be more gyrfalcon-like than saker-like. Kots (1948) believed that some individual Altay falcons look like a conglomeration of gyrfalcon (patches of gray) and saker (brown) plumage. I dispute that some Altay falcon specimens look “patched togeth- er,” but accept the hybrid concept. Dementiev (De- mentiev and Shagdarsuren 1964) resisted Kots’ hy- brid hypothesis to the end. I submit that sakers and gyrfalcons constitute a superspecies with the Altay falcon a hybrid between the two. Lorenzi should be treated as synonymous with rusticolus. There are three probable explanations for the in- fusion of gyrfalcon genes into Central Asia. First, a gyrfalcon deme may have been isolated south of a Pleistocene glacial sheet, an interpretation similar to that explaining the black gyrfalcon in the eastern Nearctic (Palmer 1988). A second explanation is that during post-Pleis- tocene cold periods, limited gene flow occurred (and may still be occurring) between gyrfalcon popula- tions to the north and the mountains of Central Asia. Until two centuries ago, gyrfalcons reportedly bred in the southern Ural Mountains and they today breed in southern Kamchatka Peninsula (Dementiev 1960, Ellis et al. 1992) at the same latitude as the northern Altay Mountains. Third, falconry escapees may have provided much March 1995 Altay Falcon Review 23 c V B V u 3 CD V 6 U V CD T) c a o u u b£) C o CD 'u -d V H-J CD d a QJ S u 3 'd "d "3 g so > s NO V 0 M < cs 0 u < OS 0 (h < ON P3 CQ M; p O'^ CM >0 ON t^‘ CM p O M- 00 Lfi Tt o6 a z r- cc q q ON T— 1 p q m 0 p 0 0 < Ed y-H i> T-^ 06 CNJ 0 so 0 r- 0 r- 0 CM 00 t-H >N (3 cn 1 M" 1 cn 1 Tf 1 1 M- 1 cn 1 1 cn 1 1 1 M- 1 cn 1 • 3 - 1 < lO p q q p p 00 lT) 00 in CM 0 00 SO < CkM Pi 'O ON NO in lO 00 r^ irl m CO NO M" cn 00 m cn 00 cn M" cn r- cn M" cn 00 cn 0 rn fT) cn cn m cn rt QJ 'a d C 3 CD O') 00 m QO NO NO V u 'c 'c 3 3 -o -a cd C 3 d <<<<<<< << c o u >• tS 3i >- < O 3 O CJ 3 U o u CTj c >0 Peh "3 "3 -3 X) "3 X) Td -3 -3 T3 -H u u Jh _3 "o "o "0 '0 3 "o "o "o '0 "o 0 0 0 0 0 0 0 0 0 0 P^ Ceh P Plh pL, ^ Pi Pi PLh PLh u c/3 CJ u CJ ort both winter and summer records of ' Amadon et al. (1988) and Sibley and Monroe (1990) consider that leucurus is the American species of Elanus which is not conspecific with the Old World caeruleus species. We follow this assumption. white-tailed kites in the Cape Region of Baja California Sur, the most southern location for the species on the Pacific coast. In November 1989, we first observed two adults perched on fences around a field in Ciudad Insurgentes (25"10'N, 111"48'W; Fig. 1). Howell and Webb (1992) also observed five kites (two of which were juveniles) at Ciudad Insur- gentes in June 1992. In December 1993, during research in agricultural areas at El Carrizal (23°46'N, 110®19'W; Fig. 1), we observed at least eight kites hunting in three different locations. We were unable to discern if individ- uals were adults or juveniles in this month because, ac- cording to Brown and Amadon (1968), a post-juvenile moult begins in July, and before the following spring juveniles resemble adults. In February 1994, five adults were observed in the same area, and again in May 1994, at least three individuals were seen hovering in the same agriculture lands at El Carrizal. In addition, three kites were recorded hunting in another cultivated field, at Cha- metla-El Centenario (24®05'N, 110“25'W; Fig. 1). In the latter case, a pair was observed in courtship activities. This behavior corresjronded to the description given in Brown and Amadon (1968) for breeding pairs. The increased incidence of white-tailed kites in Baja seems to be correlated with an increase in agricultural activity, which was strongly promoted in Baja California by the Federal government in the 1950s (Tejas et al. 1991). This activity has grown mainly in the Ciudad Insurgentes- Ciudad Constitucion, Centenario-Chametla and El Car- rizal regions. Our observations imply that the Cape Region is a wintering area for the kite because the kite population drops during March to April. However, the increase in agricultural practices in this region may have also pro- moted a range expansion of the white-tailed kite in Baja California. Our May records of kites in the Cape Region, as well as the juveniles observed in June 250 km to the 30 March 1995 Short Communications 31 Figure 1. Range expansion of the white-tailed kite in the Baja California peninsula. Solid black circles are the localities where kites where reported since 1928 (Grinnell 1928), 1985 (Wilbur 1987) and 1994 (Howell and Webb 1992, this study). north by Howell and Webb (1992), indicate a high prob- ability that white-tailed kites are now breeding throughout the Baja California peninsula. Subsequent searches for nests and fledglings in southern Baja will help to correctly determine the breeding status of the white-tailed kite in the Baja California peninsula. Resumen. — En este trabajo se presenta informacion nueva sobre la situacion actual de la poblacion del milano cola- blanca {Elanus leucurus) en Baja California Sur, Mexico. Segun nuestros registros de 1989, 1993 y 1994, la porcion sur de la peninsula es un area importante para la per- manencia de individuos invernantes. Pero ademas, la re- ciente conversion de grandes extensiones de tierra a uso agricola en el sur de la peninsula, parecen haber benefi- ciado la expansion de las poblaciones reproductoras de la especie. A1 parecer, E. leucurus se reproduce actualmente en el sur de Baja California. [Traduccion Autores] Acknowledgments Abelino Cota gave valuable field assistance. S. Pruett- Jones, Eugene S. Botelho, and an anonymous reviewer greatly improved an early draft. R. Bowers improved the English. Consejo Nacional de Ciencia y Tecnologia and Centro de Investigaciones Biologicas del Noroeste sup- ported this study. Literature Cited Amadon, D., J. Bull, J.T. Marshall and B.F. King. 1988. Hawks and owls of the world: a distributional and taxonomic list. Proc. West. Found. Vert. Zool. 3. 294-357. Brown, L. and D. Amadon. 1968. Eagles, hawks and falcons of the world. McGraw-Hill Book Co., New York, NY U.S.A. Grinnell, J. 1928. A distributional summation of the ornithology of Lower California. Univ. Calif. Publ. Zool 32:1-300. Howell, S.N.G. and S. Webb. 1992. Noteworthy bird observations from Baja California, Mexico. West. Birds 23:153-163. JOHNSGARD, P.A. 1990. Hawks, eagles and falcons of North America. Smithsonian Inst. Press, Washington, DC U S A. Pruett-Jones, S.G., M.A. Pruett-Jones and R.L. Knight. 1 980. Status of the white- tailed kite in North America. Am. Birds 34:682-688. Sibley, C.B. AND B.L. Monroe. 1990. Distribution and taxonomy of birds of the world. Yale Univ. Press, New Haven, CT U S A. Tejas, a., R. Servin and S. Gallina. 1991. Delimi- tacion, zonificacion y tenencia de la tierra. Pages 53- 68 in A. Ortega and L. Arriaga [Eds.], La Reserva de la Biosfera El Vizcaino en la peninsula de Baja Cal- ifornia. CIB Publications, La Paz, B.C.S., Mexico. Wilbur, S.R. 1987. Birds of Baja California. Univ. Calif. Press, Berkeley, CA U.S.A. Received 13 June 1994; accepted 5 October 1994 32 Short Communigations Vol. 29, No. 1 J Raptor Res. © 1995 The Raptor Research Foundation, Inc. NEST STRUCTURE COHABITATION BY RAPTORS IN SOUTHEASTERN IDAHO Richard W. Hansen' and Lester D. Flake Department of Wildlife and Fisheries Sciences, Box 2140B, South Dakota State University, Brookings, SD 57007 U.S.A. Key Words: nest cohabitation; American kestrel; Swain- son’s hawk; long-eared owl; Idaho. Competition for nest space may limit raptor populations in some areas (Newton 1976). Much of this competition may be lessened by raptors nesting in different habitats or at different times of the year or by differences in temporal activity patterns that may allow raptors to nest closer together than rhight be expected. For example, great horned owls {Bubo virginianus) have been reported to nest near red-tailed hawks \Buteo jamaicensis) (Hagar 1957, Shupe 1986). We observed two situations where different raptor species nested simultaneously in the same nest structure on the Idaho National Engineering Laboratory (INEL). The 230000-ha INEL is located on the upper Snake River Plain of eastern Idaho. The climate is typical of a cool desert with temperatures ranging between — 42°G and 39“G (x = 6“G) and precipitation averaging 22.1 cm (Clawson et al. 1989). Sagebrush {Artemisia spp.) com^ munities cover the majority of the INEL (McBride et al. 1978) . Utah Junipers {Juniperus osteosperma) are widely scattered on most of the study area and narrowleaf cot- tonwoods {Papulus angustifolio) occuring only in a narrow band along the Big Lost River, provide the majority of available raptor nesting sites on the INEL (Hansen 1994). Tree-nesting raptors which build their own nests on the INEL include red-tailed, Swainson’s, and ferruginous hawks. Even though Swainson’s hawks usually build their own nests, they will use nests built by other raptors (Schmutz et al. 1980). Swainson’s hawks readily use nests built by red-tailed and ferruginous hawks on the INEL (Hansen 1994). American kestrels {Falco sparverius) ,\ong- eared owls {Asia otus), and great horned owls which do not build nests also nest on the INEL. Both American kestrels and long-eared owls nest primarily in abandoned black-billed magpie {Pica pica) nests (Craig and Trost 1979) . The first case of nest cohabitation we observed involved American kestrels and long-eared owls (Fig. 1). In this instance, both pairs of raptors nested among the sticks in ' Present address; Department of Range and Wildlife Management, Texas Tech University, Lubbock, TX 79409-2125 U.S.A. the understructure of an abandoned ferruginous hawk nest in a Utah juniper. The understructure of this nest was slowly collapsing and several cavities had formed among the sticks and debris. The long-eared owls nested in a cavity on one side of the structure while the American kestrels occupied another cavity on the opposite side of the old nest. The cavities had less than 10 cm of sticks between them. The only instance of interspecific aggression we observed at this nest site was when the female American kestrel stooped on an adult long-eared owl that flushed during a nest inspection. The attack was short, less than one minute, and ended when the owl perched in a nearby tree (30 m away). Both pairs of raptors fledged two young. The second occurrence of nest cohabitation involved Swainson’s hawks and American kestrels (Fig. 2). This incident also occurred in an abandoned ferruginous hawk nest which was built on an old black-billed magpie nest in a Utah juniper. In this case the S wainson’s hawks nested in the nest bowl of the old ferruginous hawk nest while the American kestrels nested in the cavity of the old black- billed magpie nest. The nests were separated by about 1 5 cm of sticks and a total distance <30 cm. We did not observe any interaction between these species. The Swain- son’s hawks fledged one nestling and the American kestrels fledged four nestlings. Close nesting by raptors of different species has been reported in several raptor communities, but such nests have usually been less successful than solitary nests (Hagar 1957, Smith 1970, Houston 1975). In addition, territorial interactions between raptors nesting close together are usu- ally intense, often resulting in the desertion of one or both nests (Freemyer and Freemyer 1970, Houston 1975). The success of both raptor species inhabitating the same nest on the INEL seems unusual when compared to the other studies (Hagar 1957, Smith 1970, Houston 1975). The lack of observed interspecific territorial defense during our 10 nest inspections appears unusual, especially for a species as territorial as the American kestrel. Swain- son’s hawks and American kestrels displayed intense nest defense during our nest inspections on other parts of the INEL. Interspecific aggression between Swainson’s hawks and other buteos, as well as between American kestrels and buteos and great horned owls was commonly observed during our 3-yr nesting study. Daily activity patterns, nesting chronology, or nest placement may have lessened SH6kt COMMUNICAtlONS 33 March 19S>'5 74 cm 60 cm Figure 1 . Relative positions of American kestrel and long- eared owl nesting cavities in the understucture of a dete- riorating ferruginous hawk nest on the Idaho National Engineering Laboratory. interspecific contact. Craig et al. (1988) found that long- eafed owls on the IN EL are highly nocturnal. This would minimize their contact and potential conflict with the di- urnal American kestrel. The Swainson’s hawks were in- cubating the majority of the time they shared a nest with American kestrels, which reduced their activity around the nest while the kestrels were feeding their young. In ad- dition, the low {X)sition of the entrance to the kestrels’ nest reduced their visibility to Swainson’s hawks sitting on top of the structure. Limited nesting structures may have been responsible for a lack of intersp>ecific territorial behavior in these ex- amples of cohabitation. Lack of water in the Big Lost River due to drought and diversion has resulted in severe degradation of cottonwoods along that river. Craig and Trost (1979) counted 30 potential American kestrel nest- ing cavities in narrowleaf Cottonwoods along 25 km of the Big Lost River on the INEL; They noted clOse nesting among American kestrels, as well as between kestrels and long^eared- owls and red-tailed Hawks. Junipers large enough to support black-billed magpie or ferruginous hawk nests are also very scarce over most of the INEL. We counted 32 Junipers (^2 m tall) along 185 km of fire trails on the study area. Cavity-nesting birds such as American kestrels, and to a lesser extent long-eared owls, must cope with a scarcity of nest sites on the INEL. As a result of nest site scarcity, these cavity-nesting raptors may have been forced to nest closer together than they normally would. Interspecific contact may have been reduced through Swainson’s hawk ftttd d«it> ft American kestrel cak«t)r d««d brcnc^ Figure 2. Relative positions of American kestrel and Swainson’s hawk nests in an old ferruginous hawk nest combined with an old black-billed magpie nest on the Idaho National Engineering Laboratory. jLrIp*' tateQ* daily activity patterns, nesting chronology, and, to some extent, nest placement. Resumen. — Observamos dos casos de diferentes especies rapaces nidificando simultaheamente en la misma estruc- tura en el sureste de Idaho, en los E.E.U.U. El primer caso de cohabitacion de una estiructura nido invOlucro a Falco sparverius y a Asio otus; el segundo ejemplo involucro a F. sparverius y a Buteo swainsoni. Ambos episodios de cOhabitaCion ocuriieroh Cn viejOs nidos de B. regalis y fueron exitosos, con uilo a cuatro polios volantones. COm- petencia por las limitadas estructuras de nidificacion puede haber sido respOnsable de la coiiducta que observamOs. [Tradiicdon de Ivan Lazo] ACimOWLEDGMENTS We thank 0;D. Markham for providing useful assis- tance and comments during this project and for reviewing this manuscript. S. Cooper, R. Morris, and A. Yost pro- vided field assistance. This research is a contribution of the Environmental Science and Research Foundation, Ida- 34 Short Communications VoL. 29, No. 1 ho Falls, ID, and was funded by the U.S. Department of Energy. Literature Cited Craig, E.H., T.H. Craig and L.R. Powers. 1988. Ac- tivity patterns and home-range use of nesting long- eared owls. Wilson Bull. 100:204-213. Craig, T.H. and C.H. Trost. 1979. The biology and nesting density of breeding American kestrels and long- eared owls on the Big Lost River, southeastern Idaho. Wilson Bull. 91:50-61. Clawson, K.L., G.E. Start and N.R. Ricks. 1989. Climatography of the Idaho National Engineering Laboratory, 2nd edition. DOE/ID-12118. USDC, NOAA, Environ. Res. Lab., Air Resources Lab. Field Res. Div., Idaho Falls, ID U.S.A. Freemyer, H. and S. Freemyer. 1970. Proximal nest- ing of Harris’ hawk and great horned owl. Auk 87: 170. Hagar, D.C., Jr. 1957. Nesting populations of red- tailed hawks and horned owls in central New York state. Wilson Bull. 69:263-272. Hansen, R.W. 1994. Raptor use of the Idaho National Engineering Laboratory. M.S. thesis, South Dakota State Univ., Brookings, SD U.S.A. Houston, C.S. 1975. Close proximity of red-tailed hawk and great horned owl nests. Auk 92:612-614. McBride, R., N.R. French, A.H. Dahl and J.E. Det- MER. 1978. Vegetation types and surface soils of the Idaho National Engineering Laboratory Site. IDO- 12084 Idaho Operations Office, USDE, Idaho Falls, ID U.S.A. Newton, I. 1976. Population limitation in diurnal rap- tors. Can. Field-Nat. 90:274-300. SCHMUTZ, J.K., S.M. SCHMUTZ AND D A. BOAG. 1980. Coexistence of three species of hawks {Buteo spp.) in the prairie-parkland ecotone. Can. J. Zool. 58:1075- 1089. Shupe, S. 1986. Proximity nesting: the great horned owl and red-tailed hawk. Nebr. Bird Rev. 54:84-86. Smith, D.G. 1 970. Close nesting and aggression contacts between great horned owls and red-tailed hawks. Auk 87:170-171. Received 19 July 1994; accepted 26 September 1994 J. Raptor Res. 29(l):35-36 © 1995 The Raptor Research Foundation, Inc. Letters Chronic Reproductive Failures at a Bald Eagle {Haliaeetus leucocephalus ) NESTING TERRITORY IN Northern California During a long-term study of breeding bald eagles {Haliaeetus leucocephalus) in northern California, we observed repeated reproductive failures at a single nesting territory in our study area. Between 1970 and 1992, eagles at this consistently occupied territory did not produce a single fledgling. Here we rep>ort possible causes of these failures. The territory where repeated failures occurred (South Shore Nesting Territory) was one of six territories where bald eagles bred at Lake Britton in Shasta County in northcentral California. Reproductive data were available for this territory 15 of the 18 yr since 1970 that the territory was known to be occupied. All reproductive attempts were unsuccessful through 1992 (no young fledged). The eagles at no other territory in our study area were as unsuccessful. The female occupying this territory (AF03) was first captured and banded in 1983, and recaptured and color-banded in 1989. We believe she occupied this territory continually between 1983 and 1992 (J.M. Jenkins and R.E. Jackman 1993, Condor 95:1053-1056). Her mate (AM07) was captured and color-banded in 1988. In 1984 and 1985, after nesting failures, we collected and analyzed four whole eggs from this territory which were presumably laid by AF03. Dichloro-diphenyl-dichloroethylene (DDE) concentrations from these four eggs ranged from 4. 2-8. 4 ppm wet weight {x = 5.6; J.M Jenkins 1992, Ph.D. diss., Univ. Calif., Davis, CA U.S.A.). Wiemeyer et al. (1993, Arch. Environ. Contam. Toxicol. 24:213-227) found a marked drop in bald eagle reproduction when DDE concentrations in eggs exceeded 5 ppm (wet weight). Three of the four eggs contained dead embryos and one was infertile. Eggshell thinning of these four eggs ranged from 6.9-11.5% {x = 9.2) based on pre-DDT era standards (0.609 mm standard; L. Kiff pers. comm.). In the mid-1980s, following the egg analyses, we speculated on causes for the chronic reproductive failures that were occurring at the South Shore territory. Certainly, DDE contamination was implicated. One possible scenario was that AF03 held this territory long before her first capture in 1983, and this might explain why the territory had so repeatedly failed since 1970. If this were so, AF03 may have been exposed to relatively greater DDE contamination in the 1960s and 1970s than in the 1980s. Eggs from other territories in our study area, perhaps laid by younger females, did not show the elevated DDE residues at levels that appeared in the South Shore territory eggs. We also considered the possibility that somehow the South Shore territory was inferior in quality, perhaps in food resources. Three of the analyzed eggs were fertile, so it seemed unlikely that the male of the territory might be the cause of the problem. In 1992, AF03 was found dead in her territory and sent to the National Wildlife Health Research Center in Madison, Wisconsin, for necropsy. Results of the necropsy indicated AF03 had likely died because of an aggressive interaction with another eagle. The bird also suffered chronic oviduct impaction created by a stricture in the lower oviduct. In the late 1980s and early 1990s, we did not observe the presence of eggs or note incubation behavior in the South Shore territory, which coincides with the findings of the necropsy. Following the death of AF03 in 1992, a new adult female (AF13) paired with the resident male (AM07). This pair nested successfully in the territory in 1993, fledging one young. This was the first recorded successful reproduction in the South Shore nesting territory since it was first reported and monitoring began in 1970. In 1994, AM07 and AF13 again nested successfully, fledging two young from the South Shore territory. The Pacific Gas and Electric Co. has sponsored studies of bald eagles nesting at Lake Britton since 1983. Ron Jackman and Dan Driscoll assisted with trapping and field observations, and Lloyd Kiff and Sam Sumida, Western Foundation of Vertebrate Zoology, provided eggshell measurements. We thank Lynn Hayes and Nancy Thomas of the U.S. Fish and Wildlife Service, National Wildlife Health Research Center, for permission to rejxtrt necropsy results. T.J. Stohlgren, S.N. Wiemeyer and an anonymous reviewer provided helpful comments on our manuscript. — J. Mark Jenkins, Technical and Ecological Services, Pacific Gas and Electric Company, 3400 Crow Canyon Road, San Ramon, CA 94583 U.S.A., and Robert W. Risebrough, Bodega Bay Institute, 2711 Piedmont Avenue, Berkeley, CA 94705 U.S. A. 35 36 Peregrine Falcon Predation on an Aleutian Canada Goose The diet of the peregrine falcon {Faico peregrinus) consists primarily of birds ranging in size from passerines and shorebirds to grouse and waterfowl (A.G. Bent 1938, U.S. Natl. Mus. Bull. 170, Washington, DG U.S A-; D.A. Ratcliffe 1980, The peregrine falcon, Buteo Books, yermillion, SD U.S. A.). Very large prey items include lesser $now goose (Chen caerulescens caerulescens), brant bernicla), barnacle goose (B. leucopsis), and red-breasted goose (B, rufifollis) (R.S. Palmer 1988, Handbook of North American birds, Vol. 5, Yale Univ. Press, New Haven, GT U.S. A.). Here I describe peregrine predation on the Aleutian Ganada goose (Branta canadensis leucopareia). On 12 March 1993, I was observing a flock of approximately 6000 Aleutian Ganada and cackling Ganada geese (B c. minima) feeding in a pasture near Grcscent Gity, Galifornia. At 0807 H about 200 geese flushed and circled over an adjacent pasture. Sixty geese separated from this group and were making a steeply angled, coordinated flight toward the ground when two birds from the group tumbled to the ground. One was a peregrine falcon and the other an Aleutian Canada goose, After impact with the ground, the falcon and goose separated and the goose came to a standing position- The falcon immediately took flight, made a 10 m arc, and quickly struck the standing goose, knocking it onto its back. The peregrine then landed on the breast of the goose and attacked the neck region with its bill. The last movement by the goose was seen at 0812 H. The peregrine falcqn fed until 0911 H, after which it left. The goose was an adult female and had been banded in 1987 as a Juyenile, A lO cm portion of the upper neck was stripped of tissue down to the vertebral column. The abdominal cavity had been opened and the fat surrounding the internal organs consumed by the peregrine. The breast bone was punctured by the falcon revealing organs and tissue inside the thoracic cavity. Fat and muscle tissue of ope upper thigh had been partially consumed. Depending on the sex of the birds, the goose may have weighed from two to three times as much as the falcon. In western North America, male peregrines average 678 g and females 1038 g (R.$. Palmer 1988). Mean body weights of Aleutian Canada geese are 1700-22G() g (P.H. Johnson et al, 1979, Morphological characteristics of Canada geese in the Pacific flyway, pages 56-8Q in R.L. Jarvis and J-C. Bartonek (Eds.], Management and biology of Pacific flyway geese: a symposium, Oregon State Univ. Bookstores, Ipc. Corvallis, OR U.S, AO- Following this encounter, an adult peregrine falcon was seen pursuing Aleutian Canada geese sia times during several days in the surrounding area. Twice an individual goose was singled out by the falcon, but escaped by diving into water. The other four times the peregrine gave up the chase.— Henning C, Stabins, Wild-life Science Group, College of Forest Resources and Washington Cooperative Fish and Wildlife Research Unit, School of Fisheries, University of Washington, Seattle, ^A 9812^ U-S.A. BOOK REVIEWS Edited by Jeffrey S. Marks J. Raptor Res. 29(1 ):37 © 1995 The Raptor Research Foundation, Inc. The Vultures of Africa. By Peter Mundy, Dun- can Butchart, John Ledger, and Steven Piper. 1992. Academic Press, London, U.K. 460 pp., 23 color plates, 100 color photographs, 33 black-and-white photographs, 31 figures, 47 tables, numerous line drawings, 25 maps. ISBN 0-12-510585-1. Cloth, $118.50. — ^Grammed with information, this splen- didly illustrated and massive volume will be the stan- dard reference on the vultures of Africa (and to a lesser extent, of all those of the Old World) for the foreseeable future. All four of the authors are experts in their subject. Dr, Mundy published an earlier volume on some of the species, whereas Mr. But- chart, a talented artist, has provided a full-page plate of each species and many text figures of the vultures and associated plants and animals. An outstanding series of color photographs is very fully labeled to emphasize details that might otherwise be over- looked; the section on conservation and management has numerous black-and-white photographs. The text is very extensive, with double-column format and rather fine print. The authors’ enthusiasm re- sults in a style that is at times rather colloquial; for example, “It must have been something . . (for this vulture to have carried in its beak such a large branch to its nest). The first four chapters give an overall view of Old World vultures, their characteristics, and what is known of their evolution, including comparisons with the cathartid vultures of the New World, which evolved independently- (As an aside, I must mention that in the much discussed recent classification of living birds based on DNA analysis by G.G. Sibley and J.E. Ahlquist, both groups of vultures are to be found in the order Giconiiformes. This “order” is a fantastic hodgepxidge including, among other groups, the loons, grebes, shorebirds, storks, and penguins! If this is a true clade, its origin must lie far back in avian evolution. Thus, it is a subclass, not an order.) These chapters and others arc buttressed by no fewer than 47 tables on everything from parasites to plum- age patterns. The relevant literature has been ran- sacked for information and is listed in a lengthy bibliography. Species accounts comprise about 40 percent of the text. That for the hooded vulture {Necrosyrtes mon- achus), by no means the longest, takes 12 pages, with color plates, range map, a table of measurements, five text figures, and in all perhaps seven or eight thousand words of text. Also included are the beard- ed vulture {Gypaetus barbatus') and the palmnut vul- ture {Gypohierax angolensis) , though neither may belong phylogenetically with the other species. The Eurasian griffon iGyps fulvus) and the cinereous vulture {Aegypius monachus), which formerly bred in North Africa but are now extirpated there or nearly so, receive shorter treatment (the griffon mi- grates to northern Africa in some numbers). In total, 1 1 of the 15 species of Old World vultures are treat- ed, The remaining four species are Asiatic and close- ly related to the African ones. The next two chapters, drawing upon data in the species accounts and much additional research, an- alyze feeding and nesting dynamics. Although many of the species are centered about a common food base, each has its own requirements and preferences. The same is true for their reproductive behavior. Thus, they are a guild of associated species but not an interdependent community. Finally, it is emphasized that even in Africa, vul- tures over vast areas are dependent upon livestock, not the once vast (and now decimated) herds of game. As a result, the birds are suffering from many vi- cissitudes, including random poisoning of predatory mammals, food shortages, and electrocution by pow- er lines. The Vulture Study Group, with its own publication, and ably supported by the authors of this treatise and other conservationists worldwide, is striving to ensure the future of this remarkable group of birds. — Dean Amadon, Department of Orni- thology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 U.S.A. 37 38 Book Reviews VoL. 29, No. 1 J. Raptor Res. 29(l);38-39 © 1995 The Raptor Research Foundation, Inc. Trends in Geographic Variation of Cooper’s Hawk and Northern Goshawk in North America: A Multivariate Analysis. By Wayne H. Whaley and Clayton M. White. 1994. Proceedings of the Western Foundation of Vertebrate Zoology, Vol. 5, No. 3. 49 pp., frontispiece, 22 figures, 7 tables. ISSN 0511-7550. Paper, S8.00. — Geographic variation was a much simpler subject to understand when re- searchers studied species that supported Berg- mann’s, Allen’s, or Gloger’s ecogeographic rules. Af- ter Frances James suggested that aspects of geo- graphic variation in morphology might be environ- mentally determined and not genetically programmed, the field became very complex. Today, most studies of geographic variation of birds include measures of genetic differentiation among groups and end with a recommendation to the American Ornithologists’ Union Check-list Committee for a name change. This paper provides a return to the simpler days when the primary purpose of the work was docu- mentation. Ten anatomical characters were mea- sured on skins of 781 Cooper’s hawks {Accipiter cooperii) and 464 northern goshawks {A. gentilis) obtained from museums across North America. Adults taken primarily in the breeding season were used. Data analyses were multivariate with the ini- tial cut at geographic variation being explored by principal components analysis (PCA) derived from correlation matrices. Contour maps of PC scores were generated through trend-surface analysis. Fi- nally, multivariate correlations between morpholog- ical and environmental data sets were examined us- ing canonical correlations analysis (CANCORR). General trends noted by the authors include large individuals of both species in the extreme southwest and small individuals in the Pacific Northwest. There was general concordance in trends of geographic variation shown by both species. Wing loading (de- fined by PC II) was lower for eastern populations of Cooper’s hawks, which are more migratory than their western counterparts. Explanations for toe length variation were based on dietary considera- tions. Considerable discussion is provided on the cor- respondence between subspecific designation and morphological variation, particularly in the poly- typic northern goshawk. The monograph has numerous strengths and weaknesses. One strength is the large sample of birds examined by the authors. A weakness is the small sample of birds for western and northern Canada, which could have been augmented had the authors approached museums such as the Provincial Mu- seum of Alberta for specimens (21 Cooper’s hawk and 27 northern goshawk skins). Museums in Brit- ish Columbia could have provided even more spec- imens. I can empathize with the authors in their efforts to obtain as many individuals as possible, but with better use of faxes, e-mail, and even the Or- nithological Newsletter, this thorough study could have been definitive. As a sidebar, the authors noted what everyone who has used museum specimens to study geographic variation knows — no species is repre- sented adequately in North American museums. Of course, those opposed to collecting can point to the thousands of individuals of some species in museum drawers. However, when these specimens are grouped by subspecies, gender, age, and collecting locality, the number in each category drops precip- itously. Although this is not a theoretical monograph about size and its measurements, some of the assumptions made about size and shape would be disputed by others who study morphometries. For example, the authors used museum skins rather than skeletons to explore geographic variation. Furthermore, they as- sumed, without testing, that PC I scores constitute a size axis for both species and that PC II scores constitute a wing-loading axis (Cooper’s hawks) and wing shape/tail length factor (northern goshawks). Because of the seeming relative equality of PCs II, III, and IV, their individual interpretations should be considered tentative pending a sphericity test. The weakest interpretation, in my mind, is the conclusion that an axis contrasting feather measures with bill measures can be presumed to reflect wing loading. To the authors’ credit, they acknowledged and dis- cussed most of the weaknesses in their data. There is an apparent error in the interpretation of the standardized canonical coefficients (Table 9). The authors refer to these coefficients as if they are correlation coefficients (page 188). Standardized ca- nonical coefficients are used to produce canonical variables with unit variance. Unfortunately, the size of a standardized coefficient for a variable does not always correspond to the strength of the correlation between that variable and the canonical axis. This monograph is useful as a review of both the value and the trap of multivariate statistics. It is March 1995 Book Reviews 39 valuable to know major sources of variation in our data (PCA) and to explore correlations between in- dependent data sets (CANCORR). It is especially valuable, when PC axes have unequivocal biological interpretations, to explore their variation relative to other biotic or physical factors. The trap, as in this case, is to acknowledge that PC axes only approx- imate biological factors and then proceed to use these approximations in further analyses. If researchers wish to explore variables such as size, wing loading, or wing shape, then axes can be constructed to mea- sure these directly. There is no obligation to use a PC axis just because it hints at the factors of interest. There is too much noise in the interpretation of these axes to feel comfortable about anything except ex- tremely strong relationships. This monograph includes some interesting results that will be useful in subsequent syntheses of raptor morphological evolution. The concordance of geo- graphic size variation in these two species, and the general similarity to patterns in other species (e.g., peregrine falcon [Falco peregrinus] and great horned owl [Bubo virginianus]), suggest that there is another ecogeographic rule in need of a name. It would be interesting to know if the absence of the Cooper’s hawk from the northern range of the northern gos- hawk is evidenced in the morphology of the latter. More discussion on geographic variation of reversed size dimorphism (RSD) would have been nice. In terms of style and presentation, this is basically a lengthy journal article. Some of the maps are a bit primitive by current standards, but they are reason- ably clear and readable. Perhaps the monograph could have been condensed into a journal article, but the increased length allows for useful discussion. In summary, this monograph is clearly valuable to stu- dents of Accipiter biology and of geographic variation in raptors. The authors’ consideration of a variety of factors affecting hawk size relates to studies of reversed sexual dimorphism and makes for inter- esting reading. Regardless of my concerns with the multivariate analyses, the authors’ presentation of “size” data, which is really the core of the mono- graph, is sound. I would have liked to have seen these data achieve wider distribution through pub- lication in a journal. For a price of $8.00, however, they will be reasonably accessible. — W. Bruce Mc- Gillivray, Provincial Museum of Alberta, Ed- monton, AB T5N 0M6 Canada. J. Raptor Res. 29(l);39-40 © 1995 The Raptor Research Foundation, Inc. City Peregrines: A Ten-Year Saga of New York City Falcons. By Saul Frank. 1994. Hancock House Publishers, Blaine, WA. 313 pp., 34 color photo- graphs, 6 figures, 24 tables. ISBN 0-88839-330-X. Cloth, $29.95. — This is an intensive account of the colonization of the New York City area by peregrine falcons {Falco peregrinus) in the last decade that resulted from The Peregrine Fund’s release of hun- dreds of birds in the eastern United States. The author and his wife, Dolores, learned of one of the early nesting attempts from a television news short; their apartment was in full view of the 1983 Throgs Bridge site. The Franks became compulsive observ- ers. The book relates this passion and the compassion the Franks developed for these birds. If you must have your peregrines on massive cliffs in wilderness, then this book may not at first seem attractive. But Frank matures rapidly as an observer and relates year by year, site by site, a wealth of detailed ob- servations on nesting successes and failures and the hunting flights that underscore the enormous ver- satility of this falcon. Prey availability is almost limitless, and the max- imum nesting density these birds may reach is un- predictable in view of the great supply of buildings and bridges for nesting. Prey were caught from stoops, rushes, or by being forced to the water and then plucked from the surface. One adult male was ac- tually seen to fall into the water, return to the sur- face, and regain flight. Several times fledgling per- egrines swam to save themselves, or were rescued from drowning by their human caretakers. Frank came to accept the loss of individual birds and the broader view of natality and mortality as population phenomena. In the New York City area, peregrines were nest- ing on bridges by 1983; the New York Hospital nest in 1988 was the first on a building. Both bridges and buildings were equipped with nest boxes to en- hance the nesting substrate. My calculations from data in Appendix B show that about 58% of the eggs counted on bridges from 1983 to 1992 produced fledged young, versus about 55% for eggs laid on buildings (excluding clutches removed for captive incubation and nesting attempts interrupted by maintenance workers). However, only 36% of the bridge eggs resulted in young reaching independence compared with 49% for buildings. On bridges, young 40 Book Reviews Vol. 29, No. 1 are seeiningly at gresiter risk after they first leave the nest box. Even at that, nests on bridges produced an average of about 1.2 dispersed young per attempt (N = 22), a value surely on par with many non- urhan populations. Nesting attempts on buildings (N - 12) averaged about 2.0 dispersed young per pair. Gpllectively, these are very strong production values that no doubt were due in part to great effort by human caretakers such as the Franks, J. Aronian, M. Gilroy, J. Weaver, K. O’Brien, and J. Barkley- Sometimes the daily diary-like accounts seem rep- etitious, and the subjective explanations of peregrine behavior may be distracting to some readers. Chapter and section heading titles are not always helpful in alerting the reader as to what follows (e.g., one chap- ter is entitled “Oops”). Appendix F, a histogram, includes year headings that are badly misplaced. Most of the color photographs are of good quality and are appropriate. However, the use of inserted photos, such as on the dust cover, is excessive. An insert ruins what would have been a spectacular photograph of the Hudson Palisades. These prob- lems are easily overlooked in view of the vast, tireless work underlying this report. Overall, the book is significant in revealing how peregrines function in cities, a “habitat” used across North America. I predict that this volume will be enjoyed by a wide spectrum of people interested in natural history. Frank laments the vacant (through 1993) historical cliff sites on the Hudson Palisades not far from where bridges and buildings draw nest- ing pairs. He must indeed have been delighted to learn that in 1 994, peregrines once again nested on the Palisades. — James H. Endersnn, Pepartment of Biology, Colorado College, ColoradQ Springs, CO 30903 U,S.A. y. Raptor Res. 29(l):41-74 © 1995 The Raptor Research Foundation, Inc. Abstracts of Presentations Made at the Annual Meeting of the Raptor Research Foundation, Inc., Held at Flagstaff, Arizona, 014 2-6 November 1994 Northebn Goshawk Symposium Influence of Vegetation Structure on Selection of Foraging Habitat by Northern Goshawks in a P oNDEROSA Pine Forest BeieR, P. Department of Forestry , Northern Arizona Uni- versity, Flagstaff, AZ 86011 U.S.A. Data are needed to assess the relative importance of veg- etation structure versus prey abundance in selection of foraging sites by northern goshawks (Accipiter gentilis) in the ponderosa pine yegetatiDn type. Therefore, we radio- tagged adult breeding godiRwks on the Goconino National Forest in 1993-94, and used precise (±25 m) radio-lo- cations as centers of 1 .8-ha plots, and contrasted vegetation structure at these plots to nearby paired plots within the same aniniaFs home range. Thus we studied selection of sites within individual home ranges; Drennan (this sym- posium) indexed prey abundance at these same paired plots. We measured tree heights, tree diameters, canopy closure, ground coyer, and numbers of shrubs, saplings, snags, and ic>gs. Preliminary results from 43 pairs of plots suggest that some goshawks selected sites with more and larger trees. Results from about 60 plots and 10 goshawks will be presented- Intersexual Prey Partitioning in Northern Goshawks BOAL, G-B. AND R.W. Mannan. School of Renewable Natural Resources, University of Arizona^ Tucson, AZ 85721 U.S.A. A common explanation proffered for reversed sexual size dimorphism among raptors is that size dimorphism allows prey size partitioning between the sexes and reduces in- tersexual competition for fpod. We compared intersexual differences in prey captured by male and female northern goshawks {^Accipiter gentilis) at 16 nests in northern Arir zona during the breeding season of 1990-92. On basis of 192 prey items captured by male and 46 prey items cap- tured by female goshawks, we found no difference between the sexes in mean weight of prey captured (paired I -test, P = 0.14), or in the distribution of prey sizes (Kolomo- gorov-Smirnoff 2.-sample test, P = 0-27). There was no difference between the sexes in capture rates of mammals and birds {P = 0,35); mammals accounted for 85% and 79% of the prey captured by female and male goshawks, respectively. The sexes had a high degree of dietary overlap (92%; Pianka’s Index) but m^l^ goshawks used the avail- able prey species less equitably than female goshawks (male = 0.37, female ^ 0.51; miu ~ 9 0; max = 1.0). Prey captured in different foraging zones did not differ between the sexes (P = 0.72). Our findings suggest that prey par- titioning during the breediiig season may not be an ade- quate explanation for reversed sexuai size dimorphism- Developing a Practical Method for Surveying Northern Goshawks in Managed Forests of the Western Cascades Bosakowski, T. and M-E. VaUGHN- Environ- mental Consultants, 12391 NE 126th Place, Kirkland, WA 98034 U.S.A. We developed and tested several modifications that might potentially improve the current Forest Service protocol for surveying northern goshawks {Accipiter gentilis) in the Pa- cific Northwest (an adaptation of the Kennedy and StRh- lecker method), Because of the steep, rugged terrain of the Western Cascade Mountains, our survey design was in- tended to: (1) make greater use pf numerous logging rpads in managed forests, (2) improve broadcasting equipment used on road suryeys, (3) increase distance between broad- cast stations, (4) avoid traversing ridgetop habitat which is not normally used by goshawks for nesting, and (5) replace transects with a variable distance grid pattern to achieve complete systematic coverage. Road stations were suryeyed usii^ two outdoor powerhorn speakers (40-watt rating) powered by the vehicle cassette player. The speak- ers were mounted on the truck in opposite directions and were audible at 0.32-0.49 km depending on direction. To account for variation in topography, wind, and foliage density, we tested a Gonservative spacing maximum of 0.48 km for all broadcast stations- Foot stations were done by the U-S. Forest Service method using an amplified mega- phone and mini-eassette player which had a similar broad- cast range. A GIS was used to select potential nesting habitat (mean dbh > 30 cm, height > 24 m, density 250- 750 trees/ha) for surveying. Then, buffer circles (240 m calling radius) were drawn centered on road stations. Along ridgeiines, foot stations were set 240 m downslope- Finally, any habitat not covered by buffer circles was covered by additional foot stations. A field test of both methods in two study areas yielded eomparabic results in detection of gos- hawks, but with a savings of 36--50% in labor with the improved method- 41 42 Abstracts VoL. 29, No. 1 The History of Goshawk Habitat Management in THE Southwestern United States Boyce, D.A., Jr., E.L. Fisher and J.R. Lloyd. USD A Forest Service, Southwestern Region, 517 Gold Ave., SW, Albuquerque, NM 87102 U.S.A. Northern goshawk {Accipiter gentilis) habitat management is very controversial in the southwestern United States. In 1993, at the request of the Arizona Chapter of the Wildlife Society, the Wildlife Society and the American Ornithol- ogists’ Union established a blue-ribbon panel of scientists to review USDA, Forest Service goshawk habitat man- agement. We trace the history of goshawk management in the southwest from the 1970s through 1993. We discuss the issues that were raised by the state game and fish agencies, the environmental community and industry. We describe how the USDA, Forest Service developed its man- agement policy. We discuss fire and timber management practices and their impact on goshawk habitat quality. Finally, we briefly outline the major components of the “state-of-the-art” goshawk habitat management in North America. Managing Ponderosa Pine Forests for Predator and Prey — A Prototype for Ecosystem Management Boyce, D.A., Jr. USDA Forest Service, 517 Gold Ave., SW, Albuquerque, NM 87102 U.S.A. R.T. Reynolds. USDA Forest Service, 240 West Prospect, Fort Collins, CO 80526 U.S.A. R.T. Graham. USDA Forest Service, In- termountain Research Station, 1221 S. Main, Moscow, ID 83843 U.S.A. Single species management plans are being replaced by multiple-species habitat management plans in the south- western United States. Here we describe the basis for managing ponderosa pine forests using the habitat needs of a wide-ranging predator and the habitat needs of its prey. We present pre-settlement forest conditions, existing forest conditions, and the desired forest conditions needed to sustain the ecosystem for the northern goshawk {Accip- iter gentilis) and its prey centuries into the future. We discuss the sustainability of the ponderosa pine forest in terms of vegetative structural stages and illustrate the im- portance of a single vegetative structural stage for one prey species. Northern Goshawk and Southwestern Forest Management; A Review Braun, C.E. Colorado Division of Wildlife, 31 7 West Pros- pect Road, Fort Collins, CO 80526 U.S.A. J.H. Enderson. Colorado College, Department of Biology, Colorado Springs, CO 80903 U.S.A. M.R. Fuller. USDI National Biolog- ical Survey, 3948 Development Avenue, Boise, ID 83705 U.S.A. Y.B. LinhaRT. University of Colorado , Department E.P.O. Biology, Boulder, CO 80309 U.S.A. C.D. Marti. Weber State University, Department of Zoology, Ogden, UT 84408 U.S.A. The American Ornithologists’ Union and The Wildlife Society organized a review, November 1993, of USDA Forest Service management guidelines and implementa- tion designed to maintain habitats for the northern gos- hawk {Accipter gentilis) in southwestern forests. Specific charges were to review the scientific literature concerning northern goshawk biology and management pertinent to the Southwest, evaluate the scientific basis and policy guid- ance for the interim guidelines, perform an on-the-ground inspection of forest management conditions in the South- west relative to implementation of the interim guidelines, and prepare a report outlining the findings and recom- mendations. A summary of this report that focuses on status of the northern goshawk, forest management, and implementation guidelines is presented. Northern Goshawk Reproduction Relative to Selection Harvest in Arizona Crocker-Bedford, D.G. 243 Wood Road, Ketchikan, AK 99901 U.S.A. In Crocker-Bedford (1990, Wildl. Soc. Bull. 18:262-269), I limited my 1985-87 analyses of the effects of timber harvesting on northern goshawk (Accipiter gentilis) to 31 nest clusters which were consistent with the 1982 study plan. At the 1993 RRF annual meeting Boyce et al. sug- gested that I should have used all my 1987 data. The following analysis does so, except for nest clusters first discovered in 1987 (to avoid bias due to active territories being easier to discover). Rates of goshawk occupancy and nestling production in 1987, on the North Kaibab Ranger District, Arizona, were compared against the amount of selection harvesting 1973-86 within an assumed home range of 2.7-km radius around the center of each nest cluster. Species use of clusters was confirmed by goshawks in nests (83% of clusters — was 97% for territories in Grock- er-Bedford 1990), or was presumed from nest and stand characteristics along with nearby goshawks (15% of clus- ters — was 3% in Grocker-Bedford 1990). Occupancy in 1987 was confirmed by eggs or goshawks in nests (86% — was 100% in Grocker-Bedford 1990), recently fledged gos- hawks near used nests (9%), or by reconstruction of his- torical nest with adult goshawk nearby (5%). Young were counted near time of fledging. I separated 53 nest clusters into four categories: 12 in assumed home ranges which had received little or no harvesting 1973-86; 14 which had selection harvesting on 10-39% of each home range area; 16 which had harvesting on 40-69% of each home range area; and 11 which had selection harvesting 1973- on 70-90% of each home range area. For the four cate- gories, respectively, occupancy rates were 83%, 43%, 31%, and 9% {P < 0.001). Mean young per nest attempt were, respectively, two, two, one, and zero. Gonsidering both March 1995 Abstracts 43 occupied and unoccupied nest clusters, young produced per nest cluster were, respectively, 1.67, 0.86, 0.31, and 0.00 (P < 0.001). These and other data could indicate some real decline in the local breeding population and produc- tivity, and/or represent movement of successful breeders from more logged to less logged areas. Influence of Prey Abundance on Selection of Foraging Habitat by Northern Goshawks in a Ponderosa Pine Forest Drennan, J.E. Department oj Forestry, Northern Arizona University, Flagstaff, AZ 8601 1 U.S.A. Data are needed to assess the relative importance of prey abundance versus vegetation structure in selection of for- aging sites by northern goshawks (Accipiter gentilis) in the ponderosa pine vegetation type. Therefore, we radiotagged adult breeding goshawks on the Coconino National Forest in 1993-94, and used precise (±25 m) radio-locations as centers of 2.25-ha plots, and contrasted prey abundance at these plots to nearby paired plots within the same an- imal’s home range. Thus we studied selection of sites with- in individual home ranges; Beier (this symposium) mea- sured vegetation structure on these same plots. We indexed abundance of mammalian prey by track stations, and abundance of avian prey by point counts. The track station counts were highly correlated with numbers of chipmunks (r^ = 0.79) and golden-mantled ground squirrels (r^ = 0.71) on 15 plots where live-trapping immediately fol- lowed track station sampling. Preliminary results do not suggest that bird or sciurid abundance is an important factor in site selection. Results from about 60 pairs of plots will be presented. Nest-site Selection by Northern Goshawks in a Ponderosa Pine Forest in Eastcentral Arizona Ingraldi, M.F. Nongame and Endangered Wildlife Pro- gram, Arizona Game and Fish Department, 2221 West Greenway Road, Phoenix, AZ 85023 U.S.A. Physical and vegetative characteristics at 20 nest sites of northern goshawks {Accipiter gentilis) and 54 random sites on the Sitgreaves National Forest were measured to de- termine if selection occurs. Nest sites and random plots were limited to the ponderosa pine {Pinus ponderosa) hab- itat type. Survey plots consisted of a 25-m-radius area (main plot) centered around the nest tree or the nearest tree >30.5 cm dbh to the random point. Canopy cover, basal area, number and dbh of all stems >30.5 cm, plot aspect, percent slope and ground cover were measured. Within each main plot four randomly selected 4-m-radius satellite plots were established to measure all woody stems <30.5 cm. Northern goshawks selected larger and taller nest trees {P < 0.01 and P < 0.001, respectively) with a smaller green crown length {P < 0.001) than expected. Northern goshawks selected a nest tree that was part of a clump {P < 0.001) and placed on the lower third of a slope {P < 0.001) more often than expected. Canopy cover in the immediate vicinity of the nest tree {P < 0.05) and within the main plot {P < 0.001) was higher more often than expected. Northern goshawks exhibited an apparent selection for nest placement in stands with mature forest characteristics. Postfledging Movements of the Northern Goshawk in Northcentral New Mexico Kennedy, P.L. and J.M. Ward. Department of Fishery and Wildlife Biology, Colorado State University, Fort Col- lins, CO 80523 U.S.A. The postfledging movements of 42 radio-tagged northern goshawks {Accipiter gentilis) from 28 broods were studied in northcentral New Mexico during 1992-93. These 28 broods were part of a food supplementation experiment to determine the influence of extra food on the timing and pattern of dispersal. Half of the broods were given sup- plemental food from hatching (late April) until mid-Oc- tober. The remaining broods were controls. Telemetry locations were made approximately every 2 d from fledging until mid-October in 1992 and late November in 1993. During the early fledgling-dependency period (wk 1-4 after fledging) the majority of the juveniles, treatment and controls, were located within 200 m of the nest. From 4- 8 wk postfledging the treatment and control juveniles were usually within 1 km of the nest. However, by 1 1 wk post- fledging, most control birds were located >20 km from their nests. Treatment birds were never located >30 km from the nest for the duration of the experiment. We conclude that the control birds migrated out of the study area and the treatment birds remained. To our knowledge, this is the first documentation of a change in migration patterns after providing excess food. Goshawks in Europe and Ranges IV: Some Retrospective Analyses Kenward, R.E. Institute of Terrestrial Ecology, Furze- brook Research Station, Wareham, Dorset BH20 5 AS Unit- ed Kingdom. The Ranges IV software for analyzing animal location data was written after completion of a study in Sweden of more than 350 radio-tagged goshawks {Accipiter gen- tilis). Early analyses of goshawk foraging ranges are re- viewed. More recent techniques, including sociality indices and compositional analysis, are applied to confirm and enhance the previous findings on winter foraging and hab- itat use. Contouring, peeled polygons, concave polygons and incremental cluster analyses are used to examine how range size and structure relate to food supply and breeding success in European goshawks. The conclusion provides answers to the question “What can the behavior of radio- 44 Abstracts Vol. 29, No. 1 tagged goshg.vwks reveal about habitat suitability for this species?” Location qf GosyAtyK Nest Sites in Relation to Riparian Areas in the GENTENNii^ MpqNT^NS, Northeastern Idaho PatLA, S.M. and G.H. T'rosT- Department of Biological Sciences, Idaho State University, Box 8007, Pocatello, Ip 83209 U.S.A. Many studies have reported that northern goshawks {Ac- cipiter gentilis) often build nests near permanent water sources. Fifteen active nest sites found between 1989 and 1992 on the south side of the Centennial Mountains (Tar- ghee National Forest, Idaho) were located an average dis- tance of 238 ± 180 (SD) m from streams 11), springs {N — 3), or ponds {N — 1). In order to determine if goshawks disproportionately select nest sites in or adjacent to riparian habitats we used taped broadcast calls to sys- tematically survey a 75 km^ contiguous area of relatiyely undisturbed habitat. Within the survey area, two active and five alternate nests were found. Average distance to water of these nests, 152 ± 82 (SD) m, did not differ significantly from historic sites. An analysis of available versus used habitats within the study area will be pre- sented. Nest-site characteristics and the density of nests found using systematic survey methods will be compared to nests found on the forest oyer the past 5 yr using non- random search methods. The Breeping Performance of an Introduced Population of Northern Goshawks in Britain: Implications for Forest Manag-ement Petty, S.J. and D.I.K. Anderson. Forestry Authority, Wildlife Ecology Branch, Ardentinny, Dunoon, Argyll PA23 8TS Scotland- Northern goshawks {Accipiter ^entilip were introduced into coniferous forests in the English/hcottish borders in the late 1960s to early 1970s. The first breeding attempts were confirmed in 1972, but it was not until 1977 that successful breeding was recorded. Since then the popu- lation has increased annually to at least 61 occupied home ranges in 1993. We report on breeding performance and range expansion, and explore which factors are limiting the growth of this isolated population. Goshawks are still rare in the UK where they have established numerous widely scattered populations resulting from introductions by falconers. Goshawks also have a high level of legal protection which required the development of a manage- ment strategy to minimize the impact of forestry operations during the breeding season. The rationale behind this strategy is described together with problems associated with an increasing population in managed woodlands. Nest-site and Mate Fideuty qf Northern Goshawks in the Independence and Bull Run Mountains of Northeastern Nevada Shipman, M.S., J.V. Younk and M.J. fiECHi<^Q. Rap- tor Research Center, Department of Biology, Boise State University, Boise, ID 83725 U.S.A. In 1991 , a study was begun to examine possible impacts of gold mining activity on a population of northern gos- hawks {Accipiter gentilis) breeding in the Independence and Bull Run Mountains of northeastern Nevada, Elko Gounty. Aerial surveys by helicopter conducted in early April of 1991, 1992 and 1994 located 10, six and 26 occupied goshawk nests in the study area, respectively. Occupancy was ground-truthed in early to mid-May. An additional 1 4, 22 and five nests were found on foot in 1991, 1992 and 1994, respectively. In 1992, breeding pairs and offspring were banded with USFWS bands and color- anodized alpha-numeric bands, beginning long-term mon- itoring of nest stand fidelity, turnover rates and lifetime reproduction of goshawks in the study area. Adults were trapped using a live great horned owl {Bubo virginumus) and dho-ghaza net. In one case a female was trapped using a plastic decoy owl. By the end of the 1994 season 194 adult and immature goshawks had been colormarked for future identification. In 1993, 1 1 of 1 5 mated pairs banded in 1992 returned to the same nest stand, three nest stands were unoccupied and one female returned to the same nest with a new mate. Of seven nests where the female only was banded in 1992, six returned to the same nest stand. In 1994, only four previously banded pairs returned to the same nest stand and four males returned to the same nest stand with new mates. I’here were five cases of nest switching. Two females moved < 1 .6 km to alternate nests within the nesting territory, two females moved 4.8 and 9.6 km, and one male moved 9.6 km. Despite the apparent stability of the population in the study area, trends may indicate a slate of flux. Further data on the movements of color-marked birds in this population will be necessary before any conclusions concerning the long-term stability of this population can be made. Nesting Habitat Preference and Availability qf Suitable Nesting Habitat of Goexisting Accipiter in the Jemez Mountains of Northcentral New Mexico SiDERS, M.S. USD A Forest Service, North Kaibab Ranger District, Kaibab National Forest, Fredonia, AZ 86022 U.S.A. P.L. Kennedy. Department of Fishery and Wildlife Bi- ology, Colorado State University, Fort Collins, CO 80523 US.A. Three species of accipiter (northern goshawk, Accipiter gentilis, N = 42; Gooper’s hawk, A- cooperii, N = 52; sharp- shinned hawk, A. striatus, N = 16) nest sympatrically in Abstracts 45 March 1995 the Jemez Mountains of New Mexico. It has been pro- f>osed that these three species piirtition their nesting habitat based on vegetation charaeteristics that are correlate;d with their body sizes. From this proposed relationship, we would predict that the accipiter hawks would show preference for nesting habitat in which their body size is (1) positively correlated with stand size class and basal area; and (2) inversely correlated with stand tree density and stand per- cent canopy closure. To evaluate these predictions, we conducted a 2-yr preference study of accipiter habitat using a landscape approach. A Landsat classification was con- ducted to provide habitat availability data for the study area and these data were compared to the nest site data to analyze species preference for forest cover type, percent canopy closure, slope, aspect and thermal reflectance. Size class and basal area preference were determined through comparison of random-point locations and nest sites. Nest- ing habitat characteristics for the three accipiters over- lapped greatly. Areas of suitable nesting habitat were de- termined from areas of use and preference for all habitat layers for each species. Quantity of suitable habitat in the Jemez Mountains was examined for all three species and nesting habitat limitation is discussed. Nest-site Selection of Goshawks in Southcentral Wyoming Squires, J.R. and FuF. Ruggiero. VSDA Forest Service, Rocky Mountain Forest and Range Experirnent Station, m S. 22nd Street, Laramie, WY 82070 U.S.A. Fittle is known regarding nest-site selection of northern goshawks {Accipiter gentilis) in lodgepole pine (Pinus con- tor ta}; forests. In 1992, we studied nest- site selection of goshawks (39 active pairs) in lodgepole pine forests of southcentral Wyoming, Medicine Bow National Forest. We described the nesting habitat of goshawks at three spatial scales^nest tree, nest-tree area (0.04-ha circle cen- tered at nest tree), and nest area (homc^eneous forest stand surrounding nest). Nest-site habitat charaeteristics were compared to those randomly available. Goshawks selected the largest nest trees available. Nest trees were larger (P < 0.001) in dbh than average trees in either the nest-tree area or nest area. Nest trees were taller {P < 0.001) and larger (P < 0.001) than random trees on the study area. Dbh of nest trees ranged from 17.0-50.5 cm (x = 31.6 cm, SE = 1.3). Slopes at goshawk nests were more {P = 0.04): moderate (11%, SE; = 1.1, range 1-34%) compared to those randomly available (16%, SE = 2.1). Aspects at. goshawk nests were similar {P = 0.61) to those randomly available. Nest areas used, by goshawks difl'ered from those (P < 0.001) randomly available. Tree density in goshawk nest stands was lower (1299 trees/ha) than a sample of random stands (1562 trees/ha, P = 0.045). However, nest areas had a higher {P < 0.001) density of large trees (475.3 trees/ha, SE = 17.2, vs. 315.8 trees/ha, SE = 20.1). Trees in nest areas were also taller (mean = 20.2 m, SE = 0.4, P < 0.001) with greater (P = 0.006) heights to live canopy. The density of small trees at nest areas (212.9 trees/ha, SE = 25.3) was less (P = 0.001) than half those present in random stands (452.5, SE = 68.2). Nest areas were not “old-growth” in the classic sense of being multistoried stands with large diameter trees, high canopy closure, and large dead and down woody debris. Rather, nest areas were in even-aged, single-storied, mature forest stands with high canopy closure (mean 65%, SE = 1.4) and clear forest floors. Northern Goshawk Habitat Associations, Use Areas and Juvenile Dispersal on the Tongass National Forest, Alaska Titus, K. and R.E. Lowell. Alaska Department oj Fish and Game, Box 240040, Douglas, AK 99824 U.S.A, C.J. Flatten. Alaska Department of Fish and Game, 2030 Sea Level Drive, Ketchikan, AK 99901 U.i'.d. E.J. Degayner. USDA Forest Service^ Stikine Area, Box 309, Petersburg, AK 99833 U.S.A. We used aerial radiotelemetry to assess habitat associations and the size of areas used by adult and juvenile northern goshawks {Accipiter gentilis) during nesting and p»ost-nest- ing seasons within the temperate rainforest of the Tongass National Forest, southeast Alaska. This information is being used to assist with the development of management guidelines for maintaining goshawk habitat across the Tongass National Forest. A total of 51 goshawks were radiotagged and followed from 1992-94, including 24 ju- veniles. Total areas used in 1992-93 by adult goshawks varied from 7 69-141 240 ha indicating that concepts such as mean home range size do not currently apply because of the extreme individual variability. The size of areas used by adult goshawks during the brood-rearing period varied from 728-19 408 ha for males {N — 9) and 273- 1 1 1 410 ha for females {N == 8). The number of relocations varied from 8-50 per bird making interpretation of home range sizes difficult. The large brood-rearing areas used by two females were the result of nest abandonment during the fledgling-dependency period. Adults were nonmigra- tory. Adult males generally maintained year-round areas of use loosely associated with the nest area. Some adult females vacated the nesting area and had fall/winter use areas distinct from their nesting area. Of seven radio- tagged adult females that renested in subsequent years, two nested near their previous year’s nest, and five selected new mates and moved 4 km, 11 km, 26 km, 27 km, and 43 km to another nest area. Documented juvenile dispersal distances through mid-winter 1993/94 ranged from 1 6- 151 km. Aerial estimates of habitat use based on 667 relocations from 30 goshawks indicated that 89% were judged to be in old-growth coniferous forests. 46 Abstracts VoL. 29, No. 1 Effects of Experimental Food Addition on the Reproductive Ecology of the Northern Goshawk during Brood-rearing Ward, J.M. and P.L. Kennedy. Department oJ Fishery and Wildlife Biology, Fort Collins, CO 80523 U.S.A. In 1992 and 1993, 28 northern goshawk (Accipiter gentilis) broods in northcentral New Mexico were used in a sup- plemental feeding experiment to determine if there was a causal relationship between food availability and survival of young goshawks. The 28 nests were randomly assigned as treatments or controls, and treatment nestlings were given extra food from hatching (late April) until juvenile dispersal (mid-October). Morphometric measurements were taken and tarsal-mounted transmitters with mortal- ity switches were attached to 42 nestling goshawks when they were 21 d old. Telemetry locations were made every 2 d until mid-October in 1992 and late November in 1993. Treatment birds had a significantly higher survival rate during the nestling period in 1993, but not in 1992. Be- cause most control nestlings died from predation, we at- tribute the higher survival not to the slightly better phys- iological condition of supplemented nestlings, but to in- creased time spent in the nest stands by adult females whose presence probably deterred predators. There were no significant differences in nestling size or fledging dates. Treatment birds dispersed first but remained in the study area, whereas the control birds migrated out of the study area by October. We propose that both northern goshawk parental care and juvenile dispersal strategies vary with food availability. Mexican Spotted Owl Symposium Mexican Spotted Owls in Southeastern Arizona: Current Knowledge Duncan, R.B. Southwestern Field Biologists, 8230 E. Broadway Blvd., Suite W-8, Tucson, AZ 85710 U.S.A. S.M. Speich. Dames ir Moore, 1790 E. River Rd., Suite E-300, Tucson, AZ 85718 U.S.A. J.D. Taiz. Southwestern Field Biologists, 8230 E. Broadway Blvd., Suite W-8, Tuc- son, AZ 85710 U.S.A. R.R. Sheehy. Department of Mo- lecular and Cellular Biology , University of Arizona, Tucson, AZ 85701 U.S.A. Mexican spotted owls (Strix occidentalis lucida) exist in a naturally dispersed habitat matrix on isolated “sky-island” mountain ranges in sub-Mogollon Arizona. These moun- tain islands are mainly separated by desert-grassland as- sociations or locally desert scrub, and are biogeographi- caily linked to the Sierra Madre Occidental to the south and the Rocky Mountains to the north. In this mountain archipelago, spotted owls are mainly found in Madrean evergreen woodland and forest associations, and to a lesser degree relict conifer and Rocky Mountain montane conifer forest associations. These sites mainly contain multisto- ried, older-aged stands of trees. The majority of diurnal roost and nest sites coincide with a Mexican oak-pine woodland and mixed conifer or (X)nderosa pine forest mo- saic at 2072-2286 m. These sites are often associated with canyon bottom habitat that includes riparian deciduous forest and woodland associations, and cliff sites are often present. Diet in southeastern Arizona consists of a wide variety of nocturnal and diurnal prey species, but woodrats {Neotoma spp.) and white-footed mice (JPeromyscus spp.) are the most important prey items in terms of biomass and numbers taken. As part of an ongoing colormarking study we have banded over 150 adult, subadult, and juvenile spotted owls in southeastern Arizona. Of 56 hatching year juveniles banded from 1990-93, five have successfully dis- persed and bonded with a mate. The sky-island mountain ranges of southeastern Arizona provides an ideal experi- mental setting to test questions of dispersal, genetic iso- lation, and demographics of small isolated populations of this species. We also discuss their distribution, density, reproduction, dispersal within and between isolated pop- ulations, and other aspects of their natural history in south- eastern Arizona. In addition, a brief discussion of the pos- sible effects of recent sweeping fires to spotted owls in the mountains of southeastern Arizona will be given. Spotted Owls and Associated Raptors in Isolated Coniferous Forests: Implications for the Rapprochement of Man and Nature GehlbaCH, F.R. Department of Biology, Baylor Univer- sity, Waco, TX 76798 U.S.A. For breeding birds of the coniferous forest, area of habitat is the major determinant of avifaunal size which peaks at 28 species in 30 km^ on 12 isolated mountain ranges in southern Arizona, New Mexico, and trans-Pecos Texas. Species with northern biogeographic affinities are strongly constrained by habitat, whereas those with primary Sierra Madrean relations are also determined by isolation dis- tance. Spotted owls (Strix occidentalis) have both Rocky Mountain and Sierra Madrean affinities and nest on for- ested mountain tops with at least 1 0 km^ of habitat along with five other raptors (hawks are Accipiter gentilis and A. striatus). In the guild of four owls (S. occidentalis, Ae- golius acadicus, Glaucidium gnoma, and Otus flammeolus), complementary feeding niches can contribute to habitat stability, so large patches of coniferous forest should be more stable. Implications for forest management in this and the avifaunal size-habitat area relationship are noted with special reference to the controversy about endangered species and habitat loss to a new astrophysical facility on Mt. Graham, Arizona. March 1995 Abstracts 47 Dispersal Behavior of Juvenile Mexican Spotted Owls in New Mexico Hodgson, A. and P.B. Stacey. Department of Envi- ronmental and Resource Sciences, University of Nevada, Reno, NV 89512-0013 U.S.A. Populations of Mexican spotted owls {Strix occidentalis lucida) in the southwestern United States often are small and restricted to “islands” of habitat within isolated moun- tain ranges. Annual variation in the reproductive success of these owls is high, with few or no young produced in some years. Demographic models predict that most pop- ulations under these conditions should quickly go extinct unless there is immigration from other f>opulations. We are currently conducting a study of juvenile dispersal in the Mexican spotted owl in the mountains of central New Mexico to understand the processes by which individuals move among isolated populations. Radiotransmitters were attached to five juveniles in the southern part of the San Mateo Mountains during 1993. All five survived to dis- perse from their natal territories in late August and Sep- tember, and none spent the winter in the area where they had been born. Three birds moved to lower elevations in different parts of the San Mateo Mountains, while two others moved across at least 1 5 km of grasslands to another mountain range southeast of the study area. These birds apparently moved beyond this range as well, although their ultimate fate is unknown. One juvenile that dispersed within the San Mateos in 1993 established a new territory as a singleton at high elevations within the same range during the summer of 1 984. The implications of these and related observations for the management of the Mexican spotted owl in the Southwest will be discussed. Genetic Population Structure of the Mexican Spotted Owl {Strix occidentalis lucida) Johnson, B.S. and P.B. Stacey. Program in Ecology, Evolution, and Conservation Biology/314, University of Nevada, Reno, NV 89557-0013 U.S.A. Mexican spotted owl {Strix occidentalis lucida) populations in the mountains of the American Southwest are typically small and naturally fragmented. We have undertaken a study of the genetic population structure of this subspecies to (1) determine if local populations interact as metapop- ulations, (2) test several alternative models of metapop- ulation function, and (3) determine if local populations exhibit low levels of genetic diversity. As the initial step in this analysis, we are developing primers for microsa- tellite loci which can be used to assess genetic variation within and among populations at different geographic and taxonomic scales. Screening of a genomic library with ten different trinucleotide repeats has thus far revealed an abundance of microsatellite sequences. We present results from a preliminary survey of these loci that will allow us to detect and evaluate variation among owls in adjacent mountain ranges (same potential metapopulation), distant mountain ranges (different metapopulations), geographi- cally isolated populations (limited gene flow), and popu- lations from different subspecies (no gene flow), as well as from sister species and more distantly related species within the same genus. Demography of Two Mexican Spotted Owl Populations in Arizona and New Mexico: Preliminary Results Seamans, M.E., D.R. Olson and R.J. Gutierrez. Wildlife Department, Humboldt State University. Areata, CA 95521 U.S.A. We examined demographic characteristics in a p>opulation of Mexican spotted owls {Strix occidentalis lucida) in central Arizona and a population in westcentral New Mexico. We located owls at 48 sites in Arizona and 37 sites in New Mexico from 1991-93. Each year we captured and color-banded at least 73% of the territorial owls in Arizona and 90% in New Mexico. We measured density, territory occupancy, social status, nesting effort, fledging rate, fe- cundity, and survivorship. The highest densities for both areas were observed in 1993, 0.15 owls/km^ in Arizona, and 0.18 owls/km^ in New Mexico. Higher densities on the New Mexico study area may be due to a higher pro- portion of suitable owl habitat. Proportion of the Arizona population composed of subadults tripled from 1991 (0.1 1) to 1993 (0.33), and more than doubled in the New Mexico population from 1991 (0.07) to 1993 (0.16). The large proportion and rapid increase of subadults in the Arizona population may be due to population recovery following suboptimal years prior to our study. Reproductive activity and survivorship were similar between the two areas for all years. There was a large increase in the territorial population on the Arizona study from 1991-93. Such large fluctuations indicate the population may be unstable, and susceptible to extinction. Our data indicate the New Mex- ico population was close to saturation at the initiation of our study, and is probably more stable. Densities of Mexican Spotted Owls in Mixed-conifer, Ponderosa Pine and Pinyon-juniper Habitats of Southcentral New Mexico Skaggs, R.W. P.O. Box 214, Glenwood, NM 88039 U.S.A R.J. Raitt. Department of Biology, New Mexico State University, Las Cruces, NM 88003 U.S.A. During the spring and summer of 1988 we inventoried Mexican spotted owls {Strix occidentalis lucida) in the Sac- ramento Mountains of southcentral New Mexico in order to estimate relative densities of owls in forest and woodland habitats. We stratified our study area into mixed conifer, ponderosa pine, and pinyon-juniper cover types and within each type we inventoried six randomly selected 23 km^ plots. Each of the 18 inventory plots received three com- 48 Abstracts VoL. 29, No. 1 plete-coverage nocturnal surveys to detect owl presence. Follow-up daytime visits were conducted to search for roosts and nests near nocturnal detection sites. We detected spotted owls in 13 plots and were able to resolve those detections to 33 territories within 12 plots. Density of owl territories in mixed conifer (one territory/5.8 km^) was significantly greater than densities in ponderosa pine (one territory /23. 3 km^) and pinyon-juniper (one territory/ 46.6 km^). Roost sites of owls residing in pine and pinyon- juniper inventory plots were located in mixed conifer stands in canyon bottoms or on sheltered north-facing slopes. Regional Patterns in the Food Habits of the Mexican Spotted Owl Ward, J.P. USDA Forest Service, Rocky Mountain Re- search Station, Fort Collins, CO 80524 IJ-S.A, R.B. Duncan. Southwestern Field Biologists, Tucson, AZ 85710 U.S.A. M.E. Seamans and D.R. Olson. Department of Wildlife, Humboldt State University, Areata, CA 95521 U.S.A. J.L. Ganey and W.M. Block. USDA Forest Service, Rocky Mountain Research Station, Flagstaff, AZ 86001 U.S.A. D.W. Willey. Department of Biology, Northern Arizona University, Flagstaff, AZ 86001 U.S.A. C. Johnson and R.T. Reynolds. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO 80524 U.S.A. S.B. Derosier. P.O. Box 795, Overgaard, AZ 85933 U.S.A. S.E. Rinkevich. USDI Fish & Wildlife Service, Albuquerque, NM 87107 U.S.A. L.A. Tarango Ar- AMBULA. Colegio de Postgraduados, Salinas De Hildago, San Luis Potosi, Mexico 78600 Food habits compiled from 13 studies of the Mexican spotted owl {Strix occidentalis lucida) were examined to help plan a conservation strategy for this threatened spe- cies. Data from these studies were comprised of 11 164 prey items in 25 samples representing 18 different geo- graphic locations and a minimum of 204 owls. A cumu- lative distribution of items (%) ranked according to prev- alence indicated that on average, 90% of the owl’s diet consisted of woodrats {Neotoma spp.; 30%), white-footed mice {Peromyscus spp.; 28%), arthropods (13%), voles {Mi- crotus spp.; 9%), birds (5%), and other medium-sized ro- dents (primarily diurnal sciurids; 4%). A cumulative dis- tribution of consumed biomass (%) indicated that 90% of the owl’s diet consisted of woodrats (53%), rabbits (Syl- vilagus spp., Lepus spp.; 13%), white-footed mice (9%), birds (9%), and other medium-sized rodents (6%). How- ever, we found regional differences in the frequency of woodrats (F = 4.16, df = 6, 18, P = 0.008), birds (F = 5.12, df = 6, 15, F = 0.005), and other medium-sized mammals (F — 4.44, df = 6, 14, F = 0.010) taken by the owls among seven geographic provinces. We also found that range-wide averages of the owl’s diet may not ade- quately reflect prey associated with the owl’s reproduction. We considered these differences to be reflections of local habitat conditions that varied geographically. These find- ings supported a regional approach to conservation of the Mexican spotted owl. Home Range Characteristics of Mexican Spotted Owls in Southern Utah Willey, D.W, Department of Biological Sciences, North- ern Arizona University, Flagstaff, AZ 86011 U.S.A. G.V. Riper III. USDI National Biological Survey, Colorado Plateau Research Station, Northern Arizona University, Flagstaff, AZ 86011 U.S.A. Due to difficulties in observing nocturnal movements of Mexican spotted owls {Strix occidentalis lucida) in rocky canyonland terrain, our understanding of their habitat is poor. We radiotracked 14 adult Mexican spotted owls in rocky canyonlands across southern Utah for 6-22 mo. Owls were tracked on foot using a hand-held receiving system and from a Cessna 172 fixed-wing aircraft using wing-mounted antennae. Owls selected home ranges char- acterized by steep complex cliffs and deeply eroded can- yons within the landscape. Minimum convex polygon home ranges of individual owls were 689-2055 ha and adaptive kernel home ranges were 509-2302 ha. Average summer minimum convex polygon home range size of individual owls was 361 ha in contrast to 886 ha for winter home ranges. Nocturnal spatial use patterns indicated that in- dividuals utilized activity centers within home ranges. Overall, seasonal movements of owls showed considerable variability, and several owls used distinct summer and winter home ranges. Southwestern dwarf woodland was the most common vegetation community found within spotted owl home ranges, followed by mixed-conifer forest, mountain shrub, ponderosa pine forest and deciduous woodland, and finally, various desert grassland-shrub communities. Density, Reproductive Status, and Habitat Relationships of Mexican Spotted Owls in Southwestern Chihuahua, Mexico Young, K.E. Department of Fishery and Wildlife Sciences, New Mexico State University, Las Cruces, NM 88003 US. A. R. Valdez. Department of Fishery and Wildlife Sciences, New Mexico State University, Las Cruces, NM 88003 U.S.A. P. ZWANK. USDA National Biological Survey, New Mex- ico Cooperative Fish and Wildlife Research Unit, Las Cru- ces, NM 88003 U.S.A. In Mexico, little is know about current density, repro- ductive status and habitat use by Mexican spotted owls {Strix occidentalis lucida). The objective of the study was to estimate density, reproductive success and characterize habitat at Mexican spotted owl roosting and nesting sites. Five quadrats of 70-80 km^ each were established in the study area and completely surveyed four times between April and August 1994. Eleven pairs, 10 single males, and one single female were found in the study area. Crude March 1^95 Abstelacts 49 density of spotted owls per km^ in the five quadrats were 0.0708, 0.1007, 0.0794, 0.0563, and 0.0685, respectively. Eight owl territories were checked for reproduction. There was no reproduction for seven owl territories, and only one juvenile was fledged from the nesting pair. Habitat analysis was conducted on 13 roosting sites in 12 owl territories and one nest site. Mexican spotted owls roosting sites were characterized by pine-oak assoeiations. Domi- nant tree species found at roosting sites were oaks {Quercus spp.), Mexican white pine (Finus ayacahuite), Douglas fir (Pseudotsuga menziesii) and Arizona pine (Finus arizonica). Dominant tree species at the nesting site was characterized by Mexican white pine and Arizona pine. Mexican spotted owl habitat in southwestern Chihuahua has become ex- tensively fragmented due to forest exploitation. Swainson’s Symposium Productivity, Food Habits, and Behavior of Swainson’s Hawks Breeding in Southeast Colorado Andersen, D.E. U.S. National Biological Survey, Min- nesota Cooperative Fish and Wildlife Research Unit, De- partment of Fisheries and Wildlife, University of Minnesota, St. Paul, MN 55108 U.S.A. From 1984 through 1988, 1 studied Swainson’s hawk (Bu- teq swainsoni) ecology during the breeding season on the Pinon Canyon Maneuver She (PCMS) in southeast Col- orado, The number of nesting attempts monitored an- nually ranged from a low of four in 1984, to a high of 22 in 1987, Nests used by Swainson’s hawks were located in one-seed juniper (Juniperus monosperma) or cottonwood (Populus spp.) trees. Fractional nest success averaged 0.64 (SE “ 0.341) and ranged from a low of 0.42 in 1985 to a high of 1.00 in 1984. Based on prey remains (N — 60) collected at nest sites, food deliveries to nestlings consisted primarily of small birds (50%) and mammals (45%), and diet breadth (B ^ 2,65) was low. Minimum convex pol- ygon home range size of radio-marked adults during the post-fledging period averaged 21.2 km^ (N=^A, SE = 10.0) in 1985 and 27.3 km^ (N 4, SE = 13.0) in 1986, with males exhibiting larger home ranges than females (P ~ 0.15) across years. Compared with other breeding Swain- son’s hawk populations, birds on the PCMS exhibited high site reoccupancy among years, had large home ranges, and preyed heavily on ground-nesting birds. Home Range and Habitat Analysis of Breeding Swainson’s Hawks in the Sacramento Valley of California Babcock, K.W. Michael Brandman Associates, 10423 Old Placerville Road, Suite 100, Sacramento, CA 95827 U.S.A. Until recently, very little was known about the breeding home range and foraging habitat requirements of the Swainson’s hawk (Buteo swainsoni) in the Sacramento Val- ley of California. And yet, this region is home to the highest concentration of Swainson’s hawks in the state. In the Sacramento Valley, foraging ranges and total home range area are strongly influenced by current aigricultural crop- ping patterns and cover-types. The mean home range size of five radio-marked breeding Swainson’s hawks along the Sacramento River in 1992 was 40.9 km^. Core areas of intensive use by nesting Swainson’s hawks ranged from 0.25-0.82 km^. Individual hawks foraged as far as 24 km from the nest area during foraging activities. During the radiotelemetry study, cover-types with less overall vege- tative cover and greater prey availability (alfalfa, disced and fallow fields, dryland pasture, grain crops) ranked highest in foraging use. The use of crop and other cover- types were directly correlated with the amount of vege- tation cover, prey availability, and farming activities such as harvesting, discing, mowing, and flood irrigating. The predominance of less suitable cover-types within the study area may explain the relatively large home ranges exhib- ited by the Swainson’s hawks in this study. Changes in a Nesting Population of Swainson’s Hawks in the Los Medanos Area, New Mexico (1981-90) Bednarz, J.G. Department of Biological Sciences, Arkan- sas State University, State University, AR 72467 U.S.A. T.J. Hayden. Construction Engineering Lab, P.O. Box 9005, Champaign, IL 61826 U.S.A. Reproductive success of 238 Swainson’s hawk (Buteo swainsoni) nests and the availability of some prey popu- lations were monitored between 1981 and 1990 in the Los Medanos area of southeastern New Mexico. Mean clutch size declined significantly from 2.71 (N = 7) in 1981 to 1.90 (N — 42) in 1988 and 1989. Nest success dropped significantly from 100% (N = 11) in 1982 to 39.1% (N = 23) in 1988. Mean number of young fledged per nest decreased dramatically from 1.91 (N = 22) in 1981-1982 to a low of 0.65 (N — 34) in 1989. Measures of repro- ductive success improved slightly in 1990 but were not statistically different from the lows recorded in 1988 and 1989. Mean counts of desert cottontails (Sylvilagus audu- bonii) dropped precipitously from 11.9 per census in 1985 to 0.9 in 1988. Rodent numbers were lowest in 1986-87 and began increasing slowly thereafter. All measures of hawk reproductive performance were correlated (P < 0.05) with mean numbers of lagomorphs counted on censuses; the strongest relationship was between clutch size and numbers of cottontails (r = 0.86, P = 0.003). Annual precipitation was not correlated with measures of available prey or hawk reproductive success. This analysis dem- onstrates that Swainson’s hawk reproductive performance varies annually and is closely linked to numbers of avail- able prey. Conservation of local Swainson’s hawk popu- lations may ultimately depend on metapopulation phe- 50 Abstracts VoL. 29, No. 1 nomena in which sources and sinks are temporally dy- namic (spreading of risk). GIS Analysis of Land-use Patterns and Nesting Density of Swainson’s and Red-tailed Hawks in Northern Utah Bosakowski, T. Beak Environmental Consultants, 12391 NE 126th Place, Kirkland, WA 98034 U.S.A. D. Ramsey. Department of Geography, Utah State University, Logan, UT 84322 U.S.A. D.G. Smith. Biology Department, Southern Connecticut State University, New Haven, CT 06515 U.S.A. A total of 30 red-tailed hawk {Buteo jamaicensis) nests and 28 Swainson’s hawk {B. swainsoni) nests were discovered in Cache Valley, Utah, during the summers of 1992 and 1993. All nests were found in trees, but red-tailed hawks more often nested in dead trees. GIS analysis of land-use patterns was made for 1-km radius around nest sites. Results revealed that overall land-use at nest areas was dominated by cropland, alfalfa, and pasture, but no sig- nificant differences were found between species. Red-tailed hawk nests were surrounded by greater areas of riparian areas and fallow fields. Swainson’s hawk nests were sur- rounded by significantly greater areas of industrial/com- mercial zones. Despite this difference, distance to the near- est paved road and building was very similar for both species implying that little difference exists in the tolerance levels for human activities. In the intensive study area, ecological nesting densities (minimum convex polygon method) were 2.56 km^/nest for Swainson’s hawk and 6.35 km^/nest for red-tailed hawk. Nearest neighbor dis- tances were 1.52 km for Swainson’s hawk nests and 2.88 km for red-tailed hawk nests. The only clear management strategy favoring Swainson’s hawks would be to keep tree densities down or manage open lands away from riparian zones. Nest-site Selection and Reproductive Performance of Urban Nesting Swainson’s Hawks in the Central Valley of California England, A.S. Department of Wildlife, Fish, and Con- servation Biology, University of California, Davis, CA 95616 U.S.A. J.A. Estep. Jones ^ Stokes Associates, 2600 V Street, Sacramento, CA 95818 U.S.A. W.R. Holt. 3900 River Drive, Stockton, CA 95204 U.S.A. In the last 5 yr, Swainson’s hawks {Buteo swainsoni) have been regularly observed nesting in urban settings in Davis, Stockton, and Woodland, California. These Central Val- ley communities are small- and medium-sized cities sur- rounded by agricultural crops used as foraging habitat by Swainson’s hawks; distance to foraging habitat is typically <5.0 km. Urban nesting hawks select nests in three set- tings: (1) large, non-native trees in neighborhoods greater than 50 yr old; (2) smaller, non-native trees with dense canopies (primarily conifers) in neighborhoods 20-40 yr old; and (3) remnant riparian or oak woodland trees that existed prior to development. Preliminary analysis of the number of young fledged per occupied nesting territory does not indicate a statistically significant difference {P > 0.05, Kruskal- Wallis ANOVA by ranks) between nests in urban, rural, or edge settings. Similar, but unoccupied, urban nesting habitat is located in older neighborhoods in the Central Valley communities of Lodi and Sacramento, small and large communities respectively. These potential nesting areas are surrounded by large expanses of either vineyards (Lodi) or urban development (Sacramento); nei- ther are suitable Swainson’s hawk foraging habitat. In both instances, distance to foraging habitat is typically >8.0 km. The results of this analysis suggest that the success of urban Swainson’s hawk nesting territories in Davis, Stockton, Woodland, or other Central Valley cities may decline as distance to foraging habitat increases. Overview of Swainson’s Hawk Population Status and Natural History Fry, D.M. Department of Avian Sciences, University of California, Davis, CA 95616 U.S.A. Swainson’s hawks {Buteo swainsoni) were originally birds of open savannah-steppe, where nesting habitat of large trees was surrounded by foraging habitat with prey of small mammals, some birds and large insects. The con- version of large areas of western North America to agri- culture has changed much habitat, and Swainson’s hawks have adapted in both breeding and foraging habits. Com- patible agriculture for foraging now includes pasture, su- garbeets and alfalfa cropland, plus newly harvested fields of several crops, and foraging areas are often at consid- erable distance from nesting areas. Some agriculture- adapted Swainson’s hawks have adopted urban breeding locations, nesting in trees in towns and cities in central California. Drought, and its effect on prey populations, has had a cyclical negative effect on Swainson’s hawk populations throughout their breeding range in nonirri- gated areas. Where conditions are favorable, there is evi- dence that individual birds do shift to foraging in agri- cultural areas when natural prey populations drop. How- ever, despite some populations showing adaptation to hu- man encroachment and a shift in foraging to agriculture, a significant loss of breeding populations has occurred. Much loss has been due to urbanization and loss of all suitable foraging habitat, but populations have also been extirpated from some apparently suitable habitat, possibly correlated with long-term rodent control programs. Ecological Relationships between Nesting Swainson’s and Red-tailed Hawks in Southeastern Idaho March 1995 Abstracts 51 Hansen, R.W. and L.D. Flake. Department of Wildlife and Fisheries Sciences, South Dakota State University, Brookings, SD 57007 U.S.A. We compared reproductive success, nest site characteris- tics, and food habits of nesting Swainson’s (Buteo swain- soni) and red-tailed {B. jamaicensis) hawks along the Big Lost River and Birch Creek on the Idaho National En- gineering Laboratory between 1991 and 1993. Productiv- ity was similar between species. Twenty-six red-tailed hawk nests produced 37 fledglings (1.3/attempt) while 17 Swainson’s hawk nests produced 21 fledglings (1.2/at- tempt). Nest trees used by Swainson’s hawks were shorter, smaller, and in better condition than those used by red- tailed hawks {P < 0.01, Wilcoxon). Swainson’s hawk nest trees were more foliated than most trees along Birch Creek and the Big Lost River {P < 0.006, Wilcoxon). Red-tailed hawk nest trees were similar to available trees. Food habits were similar between hawk species with Microtus spp. and leporids comprising the majority of prey consumed. Ri- parian vegetation condition, notably the lack of cottonwood and willow regeneration, appeared to be a major factor accounting for a decline in Swainson’s hawk nesting along river channels on the INEL. The Swainson’s Hawk Productivity Crash Houston, C.S. 863 University Drive, Saskatoon, Saskatch- ewan, S7N Of 8 Canada Swainson’s hawks {Buteo swainsoni) were healthy and re- producing consistently well in western Saskatchewan from 1969 through 1987. Suddenly trouble became apparent, with six consecutive “bad” years occurring in a row, the six worst in 25 yr. Decreased productivity became evident in both grassland pastures and croplands near Kindersley in 1988, but at Alsask only in 1992. By 1993, the number of nesting pairs in Kindersley was less than half of that found 10 yr previously, most pairs failed, and even the successful pairs raised only one young per nest. The decline began in drought years and accelerated in two wet years, but finally began to reverse at Kindersley in 1994. Through 1993, the drastically decreased numbers of Richardson ground squirrels {Citellus richardsonii) , the hawk’s main prey species, may in part have been related to increased numbers of foxes {Vulpes spp.) and coyotes {Canis latrans). Sexual and Geographical Color Variation among Swainson’s Hawks ScHMUTZ, J.K. Department of Biology, University of Sas- katchewan, Saskatoon, SK S7N OWO Canada P.H. Bloom. Western Foundation of Vertebrate Zoology, 439 Calle San Pablo, Camarillo, CA 93010 U.S.A. B. Woodbridge. USD A Forest Service, Klamath National Forest, Goosenest Ranger District, 37805 Hwy. 97, Macdoel, CA 96058 U.S.A. S.J. Hawks. USDI Bureau of Land Management, Susan- ville District, P.O. Box 1090, Susanville, CA 96103 U.S.A. We examined ventral plumage coloration of breeding Swainson’s hawks {Buteo swainsoni). These hawks are highly variable in their plumage coloration and this vari- ation was due to differences in the color of melanin pigment and differences in pigment distribution. Females tended to be darker than males. Swainson’s hawks were smaller and darker in California than in Alberta. We could find no differences in reproductive success based on plumage. A comparison of parents and offspring suggests that the differences in coloration are heritable. Swainson’s Hawk Associations in the Sacramento Valley’s Agricultural Landscape Smallwood, K.S. EIP Associates, 1401 21st Street, Suite 400, Sacramento, CA 95814 U.S.A. Most studies of Swainson’s hawk {Buteo swainsoni) for- aging habits and habitat use involve monitoring of birds within a cluster of home ranges. The interpretative value of these studies can be increased by integrating their results with those from studies across a much larger spatial scale. I designed an extensive sampling program to express for- aging habits and habitat use across many potential home ranges, thereby representing the population-level inter- action with an agricultural landscape. After 5 yr and 110 surveys along a 200-km road transect from a car traveling at 50-55 mph, I made 151 observations of Swainson’s hawk. These observations were mapped on a GIS and analyzed for associations with attributes of the landscape. Most Swainson’s hawk observations were on a short stretch of transect in the east-west center of the valley near ri- parian habitat and groves of valley oak {Quercus lobata). Most (82%) were of birds in flight, and 62% were in groups, including 15 pairs and a foraging group of 23 individuals. Given the percentages of landscape elements along the transect, Swainson’s hawks were observed less often than expected by chance at irrigated pasture, rice and rice stubble, and plowed fields with very little plant debris. They preferred alfalfa (especially stands >2 yr old), riparian habitat, asparagus, and especially, annual field crops during harvest and till. In addition to conditions on its wintering range, the future status of the Swainson’s hawk population in the Sacramento Valley will depend on trends in crop acreage, cultural practices, and the extent of high-quality nesting habitat across the landscape. The Swainson’s hawk jxjpulation in the Sacramento Valley might increase substantially by establishing a well-con- nected network of nesting and prey-bearing habitat cor- ridors, which is central to the proposed Habitat Manage- ment Program of Yolo County, California. Annual Turnover and Reproductive Success of Marked Adult Swainson’s Hawks in the Butte Valley, California 52 WOODBKIDGE, B . USDA‘ Forest Service, Klamath National Forest, 1312 Fairtane Eoad, Yreka, €A P6&97 V.S.A. K. Finley. Camassi Consultants, 3A33S Bellfountain, Corvallis, OR 97333 V.S.A. P.H. BlgOM. Western Foun- dation of Vertebrate Zoology, 1361 1 Helves Ave., Santa Ana, CA 92705 V.S.A. Results of a 1 0-yr study of a breeding p>opulation of Swain- son^s hawks (Buteo swainsoni) in the Butte Valley, north- ern California, are presented^ OGeupancy and reproduetive performance were monitored at 23-83 territories between 1984 and 1994, and 454 breeding attempts were recorded. One-hundred and fifty breeding adults have been trapped and eolorbanded since 1984; we present data in territory fidelity and annual turnover rates of marked adults. In 1994, 61 territories were known to be occupied by pairs. Of the 124 adults observed in the study area, 81% were colormarked or banded. Approximately 550 nestlings have been banded since 1979; 42 of these were later recaptured as breeding adults 3-12 yr of age. We discuss annual variability in adult turnover and reproductive perfor- mance. General Scientifig Program Ferruginous Hawks in Montana with Special Emphasis Placed on Delineation of Suitable Habitats FOR Surveys Generated through a Statewide GIS Atkinson, "Ej-O. Raptor Research Center, Boise State Uni- versity, Boise, ID 83725 V.S.A. Statewide distribution of ferruginous hawks {Buteo regalis) in Montana was reviewed with an emphasis placed upon habitat use in four very different and very separated study areas. This habitat assessment was joined with a statewide geographic information system (Montana Agricultural Potentials System) to provide maps of potential ferrugi- nous hawk habitat. These maps were generated with a resolution of 21.3 km^ and were produced through the use of three land-attribute layers: land ownership, land use, and climax vegetation. These maps will provide the land- manager and field biologist with easily accessible baseline information regarding the placement of long-term ferru- ginous hawk nesting quadrats for population monitoring. Orange-breasted Falcon (Falco deiroleucvs) Breeding Biology, Nesting Sites, and Distribution in Guatemala and Belize Baker, A.J. 2702 Boylston Road, Kittitas, WA 98926 V S.A. O. A. Aguirre- Barrera. El Fondo Peregrine, Pe- ten, Guatemala. W. Morales. El Fondo Peregrine, Cayo, Belize. D.F. Whitacre. The Peregrine Fund, Inc., Boise, ID 83709 V.S.A. We Studied the breeding biology of the orange-breasted falcon (Falco deiroleucus) in Guatemala and Belize during 1992, 1993, and 1994. Historicaliy considered a species dependent on vast tTacts of primary forest, four of our 15 known sites exist in severely fragmented habitats- of pri- mary and secondary forest, agriculture, and pasture. To what degree these non-primary forest habitats are utilized is unknown. Of 26 nesting attempts, 13 succeeded in fledg- ing 28 young. Three nests failed during incubation and three while brooding. In 1994 an adult male was trapped and outfitted with a tail-mounted transmitter. Although this pilot Study was conducted through biangulation, it indicates that this male was commonly travelling frOm 5- 10 km from the nest over successional forest, intensive agriculture, and pasture. In 1994 nine active sites in Belize fit inside a diameter of 30 km and 13 active sites in Gua- temala and Belize within a 160 km diameter. Grange- breasted falcons occur and appear to be successful in a variety of habitats and nesting circumstances. Perhaps, like the peregrine falcon, they are more adaptable to a rapidly changing landscape than previously suspected. Comparison of Roadside Counts and Radiotelemetry to Determine Habitat Use of Ferruginous Hawks Wintering on Rocky Mountain Arsenal, Colorado Beane, R.D. Zoology Department, Denver Museum of Natural History and Department of Biology, University of Colorado, Denver, 2001 Colorado Blvd., Denver, CO 80205 V.S.A. C.B.. Preston. Zoology Department, Denver Mu- seum of Natural History, 2001 Colorado Blvd., Denver, CO 80205 V.S.A. The ferruginous hawk (Buteo regalis) is currently classified as a candidate species for inclusion on the federal threat- ened and endangered species list. As a migratory raptor, the over-wintering condition of ferruginous hawks is im- portant to the overall reproductive rate of the species. However, little information is available on the habitat use of wintering ferruginous hawks. We used two standard methods, roadside counts and radio-tracking, to evaluate habitat use of ferruginous hawks wintering on Rocky Mountain Arsenal (RMA), northeast of Denver, Colo- rado. A comparison of the similarities and differences of the two survey methods will be presented. The results of this study will provide information on the advantages, disadvantages, and applicability of survey methods to eval- uate raptor habitat use. The RMA has recently been des- ignated a national wildlife area and is also a major su- perfund site currently in the initial stages of extensive clean-up operations. Providing habitat use information will allow the U.S. Fish and Wildlife Service to manage resources, wildlife viewing opportunities, and provide in- put into clean-up operations that may impact ferruginous hawks. March 1995 Abstracts 53 Habitat Requirements of the Madagascar Fish-Eagle BeRKELMAN, J. Department of Fisheries and Wildlife Sci- ences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 U.S.A. J.D. Fraser. Department of Fisheries and Wildlife Sciences, Virginia Polytechnic In- stitute and State University, Blacksburg, VA 24061 U.S.A. R.T. Watson. The Peregrine Fund, Inc., 5666 W. Flying Hawk Ln., Boise, ID 83709 U.S.A. Madagascar fish-eagle {Haliaeetus vociferoides) popula- tions have declined dramatically in recent decades as a result of habitat loss and human persecution. Fish-eagle habitat requirements were investigated to help determine what management action should be taken to prevent the eagle’s extinction. Characteristics of fish-eagle nesting habitat were examined from May to August 1994 in a 3000 km^ area of lakes, rivers, and wetlands in the An- tsalciva region of Western Madagascar. Habitat variables were measured at sites used by eagles and compared with values measured at random sites within the same area. Comparisons were made at the following levels; nest and perch trees, nest sites, shoreline habitat, and aquatic hab- itat. Logistic regression was used to identify the variables that best distinguish habitat used by eagles and to develop a predictive model for suitable fish-eagle habitat. The mod- el will be used to locate other areas of suitable fish-eagle habitat and to survey these areas for eagle use. The results of this study will help to determine the extent to which the fish-eagle is limited by habitat availability and whether there are areas of unoccupied habitat where the species could be reintroduced. Anticuckoldry Behavior in the Western Burrowing Owl {Speotyto cvnicvlaria hypugaea) Botelho, E.S. and P.C. ArrowooD. Department of Biology, New Mexico State University, Las Graces, NM 88003-0001 U.S.A. Even though burrowing owls {Speotyto cunicularia) are monogamous within a breeding season, their large clutch sizes provide a lengthy fertile period over which extra- pair copulations could take place. Burrowing owls also frequently nest in loose colonies, a situation which makes encounters with conspecifics more likely. If male burrow- ing owls guarded their mates wherever they went, how- ever, they could risk losing their burrows since burrow takeovers are common. We, thus, expected to observe mate guarding behaviors at burrows prior to clutch initiation. For 8 wk following the spring arrival of females into our study area in 1993 and 1994, we recorded the following behaviors that may be involved in paternity assurance: copulations, allopreening and male primary calls. The duration of time that the male and female spent at the burrow entrance alone and together was also recorded alopg with nearest neighbor distances. Copulations oc- curred in all weeks but were most frequent during week five of the observation period. The duration of time that the pair spent together at the burrow entrance was high during weeks 1-5 and declined thereafter. The duration of time that the female was left alone at the burrow en- trance was low initially and peaked during weeks 6-8. The frequency of copulations and male primary calls were not significantly correlated with nearest neighbor distance. The frequency of allopreening was low during weeks 1- 5 but increased sharply during weeks 6-8, after the peak in copulations. A peak in copulations during week 5 and the amount of time in which the female was left alone suggest anticuckoldry behavior by male burrowing owls. Allopreening and the lack of a correlation between cop- ulations and primary calls with nearest neighbor distance, however, do not. Further observations are necessary in order to further confirm anticuckoldry behavior by male burrowing owls. Factors Controlling Bald Eagle Reproduction in THE Great Lares Region Bowerman, W.W. and J.P. GmSV. Department of Fish- eries and Wildlife, Pesticide Research Center, and Institute for Environmental Toxicology, Michigan State University, East Lansing, MI 48824 U.S.A. The bald eagle {Haliaeetus leucocephalus) pop\x\ 2 A.\on, within and adjacent to the Great Lakes Basin, constitutes the greatest single population within the contiguous United States. Bald eagles were largely extirpated from the Great Lakes by the mid-1960s, due to the effects of DDE. Eagles began to repopulate and raise young again along the shores of the Great Lakes, with the exception of Lake Ontario, by the 1980s. Factors limiting bald eagle populations in this region were studied. We compared and contrasted nesting eagles from 10 subpopulations including six in- terior and four Great Lakes, in a region from northern Minnesota though the north shore of Lake Erie in Ohio for the period 1977-93. Ecological factors investigated included food habits, nest tree use, winter habitat use, and the identification of potential nesting habitat. Bald eagles primarily foraged on fish (suckers, bullheads, northern pike, carp, and freshwater drum). Eagle nests were built primarily in white pines, but in cottonwoods near Lake Erie. Potential nesting habitat exists along the shorelines of all Great Lakes, primarily along Lakes Huron and Superior. Habitat availability, however, may limit the Lake Erie subpopulation, which has little unoccupied habitat and great density of nesting eagles. Toxicological aspects investigated included monitoring concentrations of PCBs and p,p' -DDE in plasma, mercury and selenium in feath- ers. Concentrations of p,p'-DDE or PCBs, but not mer- cury or selenium, were significantly, and inversely cor- related with regional reproductive productivity and success rates. Reproductive productivity of bald eagles within this population is primarily regulated by concentrations of or- 54 Abstracts VoL. 29, No. 1 ganochlorine compounds along the shorelines of the Great Lakes, and density dependent factors in the interior, rel- atively uncontaminated areas. The continuing recovery of this population will depend on maintaining greater pro- ductivity in interior areas to compensate for lesser fecun- dity and greater adult mortality along the shorelines of the Great Lakes. Breeding Success of Peregrine Falcons in Relation TO Weather in an Arctic Environment Bradley, M. Wildlife Biologist, Department of Renewable Resources, GNWT, Fort Smith, NWT XOE OPO Canada We studied variability in breeding success and correlated breeding success with weather in an Arctic population of peregrine falcons {Falco peregrinus). We found that breed- ing phenology had a low degree of variability, and was related to weather only one year out of 12. Breeding success was high for the species (on average 1.4 chicks per ter- ritorial pair, or 2.5 chicks per successful pair), but vari- ability was also high (0.6-2. 5 chicks per territorial pair). Clutch size was correlated with rainfall and wind during the prelaying stage (r^ = 0.75, P < 0.01) and severe weath- er events coincided with high mortality of young during both the incubation and nestling stages of the breeding season. We also found that severe weather early in the breeding season could delay and cause subsequent high chick mortality. Mortality of young was significantly dif- ferent among the three stages of the breeding season, but this difference was only seven percent (26% mortality dur- ing the nestling stage, 33% during the incubation stage). Long term climatic changes that result in an increase in snowfall or storms could be deleterious to Arctic peregrine falcons. Autumn Migration of Peregrine Falcons Determined by Satellite Radiotelemetry Britten, M.W. National Park Service, Rocky Mountain Regional Office, Denver, CO U.S.A. and Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO 80523 U.S,A. S. AMBROSE. Endangered Species Office, U.S. Fish and Wildlife Service, Fairbanks, AK 99701 U.S.A. P.L. Kennedy. Department of Fishery and Wildlife Biology, Colorado State University, Fort Col- lins, CO 80523 U.S.A. We rejxirt on the results of a study of fall migration of adult female peregrine falcons (Falco peregrinus) tracked by satellite radiotelemetry. In July and August 1994, we captured 1 5 adult female peregrine falcons on their upper Yukon River breeding area in eastcentral Alaska and at- tached satellite radiotransmitters to them using backpack- style harnesses. We report on the migration route, direc- tion and speed of the birds and analyze their movements in light of broad scale weather patterns during autumn. Gutting the Boreal Forest; Implications for Canadian Forest-dwelling Raptors Court, G. and S. Hannon. Department of Zoology, Biological Sciences Building, University of Alberta, Ed- monton, Alberta T6G 2E9 Canada Recently, very large forestry leases have been granted to companies interested in cutting aspen (Populus spp.) in the mixed- wood boreal forest of western Canada for pulp production. In less than 2 yr, the government of Alberta leased over 220 000 km^ of this forest without any envi- ronmental impact assessments or public hearings. Sub- sequently, several forestry /wildlife impact studies were initiated, however little consideration was given to the effect of these harvests on forest-dwelling raptorial birds. Eight species of owls, three species of accipitrine hawks, and two forest-dwelling buteos may breed within this re- gion and the target harvest species (mature aspen) com- prises the type of habitat used by several of these raptors for foraging and nesting. For some Vulnerable (G.O.S.E.W.I.C.) species, like the Cooper’s hawk (Accip- iter cooperii), the forests of Northern Alberta may represent a large portion of the unbroken nesting habitat remaining within the range of this bird in Canada. Until recently, there has been no attempt to survey for populations of raptors in the mixed-wood leases, much less attempt to determine the relative abundance of different species or how forest cutting practices might affect populations. Dur- ing the summers of 1993 and 1994, we attempted to survey raptors in a portion of the largest forest management area in Alberta. Here, we provide preliminary results of these surveys and detail plans for future work on raptor pop- ulations in this area. We highlight potential impacts of aspen harvesting on migratory species so as to encourage international raptor migration/count programs to evaluate population trends in light of very large industrial forest operations in Canada. Lead Levels in Golden Eagles in Southeastern Idaho Craig, E.H. and T.H. Craig. Western Ecological Stud- ies Team, P.O. Box 82, Tendoy, ID 83468 U.S.A. A.E. Thomas. Bureau of Land Management, State Office, 3380 Americana Terrace, Boise, ID 83707 U.S.A. We studied the occurrence of lead in free-ranging golden eagles (Aquila chrysaetos) in two adjacent river valleys in southeastern Idaho from December 1989 to present. Blood samples (N =178) from golden eagles were analyzed for lead and grouped into one of four categories: <0.20 ppm = background; 0.20-0.59 ppm = exposed; 0.60-0.99 ppm = clinically affected; >1.00 ppm = acute lead poisoning. Forty-two percent of all wintering golden eagles sampled had elevated blood lead levels (>0.20 ppm) and there was a highly significant difference in lead levels between golden eagles wintering in the two river valleys. All the eagles in March 1995 Abstracts 55 the Pahsimeroi Valley with elevated blood lead levels (35.1%) were in the lowest exposure group (0.20-0.59 ppm). In the Lemhi Valley, 48.0% of the golden eagles had elevated blood lead levels and 21.5% of these had levels >0.60 ppm lead. Both resident and migrant golden eagles winter in the study areas; however, recapture data indicate there is little movement of eagles between the two valleys during the winter. Nestling eagles in these valleys did not have elevated blood lead levels. The source of lead con- tamination in Idaho eagles is not known, nor is it known if the lead contamination is confined to resident or migrant eagles. We plan to expand the study in the future in an attempt to answer these questions. Electrocution as a Mortality Factor in an Urban Population of Harris’ Hawks Dawson, J. W. and R. W. Mannan. School oj Renewable Natural Resources, University of Arizona, Tucson, AZ 85721 U.S.A. We studied the ecology of Harris’ hawks {Parabuteo uni- cinctus) nesting in an urban environment in and near Tucson, Arizona, 1990-93, and examined the role of elec- trocution as a mortality agent. We attempted to recover and examine the remains of all hawks that died in our study area. We used a hierarchal approach to classifying electrocutions based on field examinations, laboratory nec- ropsies, and, in some instances, credible anecdotal and circumstantial evidence. We recorded 177 mortalities and classified them as either electrocutions (112), possible elec- trocutions (44) or instances in which we could not deter- mine cause of death (21). Electrocution most commonly occurred on residential power lines and transformers and was the most common mortality factor encountered during our study. Fledglings at some nests were particularly sus- ceptible to electrocution during the first 2 wk after fledging, possibly due to the proximity of power poles to nest trees. Among adults, females were most commonly electrocuted possibly due to larger body size and their behavioral roles in dominance interactions. Although nesting success by urban breeding groups was high, survival of fledglings was low due to electrocution. High mortality among adults in groups appeared to be offset by an abundance of floaters in urban areas that quickly replaced hawks that died. High mortality may have also kept breeding group sizes lower than was common among groups nesting in nonurban areas. Preliminary Raptor Surveys in Western Mongolia Ellis, D.H. Patuxent Environmental Science Center, Laurel, MD 20708-4019 U.S.A. M.H. Ellis. Art De- partment, Brigham Young University, Provo, UT 84601 U.S.A. P. Tsengeg. University of Mongolia, Ulaanbaatar, Mongolia Raptors were observed on a 5200 km expedition from Ulaan Baatar through the Hangay Mountains to the Rus- sian Altay Mountains with return through the Gobi Altay Mountains. The focus of the expedition was on nesting ecology of the Saker (Falco cherrug) and Altay falcons (F. altaicus) (25 eyries were located), but nests were also found for seven other species including more than 30 nests found of the upland buzzard {Buteo hemilasius). We conducted 21 day-long counts and 10 more formal raptor road counts. Raptors were concentrated in areas where perches were common and where food was most abundant. Western Mongolia remains a vast undeveloped land where camel trains and yak carts are normal. No developed highway network exists. Raptor work in the interior must be sup- ported by four-wheel drive vehicles traveling cross country. Food and fuel for a research team are difficult to procure, but raptor populations are largely unexploited. Raptors frequently nest on the ground or on very low cliffs and tress, and often nest in close proximity of pairs of their own and other species. Several areas of special significance to raptors are discussed including the Taleen Ulaan (Red Steppe) areas of granite dells which we recommend for status as an international reserve. POSTFLEDGING BEHAVIOR OF WESTERN Screech-owls; The Effect of Dominance on Timing of Dispersal Ellsworth, E.A. Raptor Research Center and Depart- ment of Biology, Boise State University, Boise, ID 83725 U.S.A. J.R. BelthoFF. Raptor Research Center and De- partment of Biology, Boise State University, Boise, ID 83725 U.S.A. Behavioral dominance may be a proximate factor related to dispersal in birds. One component of dispersal that dominance may affect is the timing of movements that juveniles make away from their natal areas. In one man- ner, subordinate juveniles may initiate dispersal before dominants if dominants aggressively force subordinate sib- lings to dispjerse. For example, dominant birds may chase subordinate siblings from natal areas. Conversely, if vacant territories are limited and early arriving birds are more successful in acquiring territories, selection would likely operate on young to disperse as early as possible. In this case, dominant individuals, because they have priority of access to resources and presumably mature more rapidly, would disperse before subordinate siblings. We are ex- amining the effect of dominance, body size, and sex on dispersal in western screech-owls {Otus kennicottii) in southwestern Idaho using radiotelemetry to observe young during the postfledging period and as they initiate dispersal movements. To assign dominance status within broods, we videotape interactions among nestlings during the pre- fledging period which allows us to evaluate and assign social ranks based on wins and losses during agonistic interactions. Subsequently, the social ranks are examined 56 Abstracts VoL. 29, No. 1 relative to the timing of dispersal. Our paper will focus on results of the first year of a 2-yr study. Diurnal Activities of Migrating Juvenile Red-tailed HaWks FESnock, A.L., K.L. Scheuermann and A.B. HaRPer. Golden Gate Raptor Observatory, Fort Mason, Bldg, 201, San Francisco, C A 94123 U.S.A. From 1990-93, we studied fall movements of nine juvenile red-tailed hawks {Buteo jamaicensis) via radiotracking. Our tracking time for each bird ranged from 24 hr to 9 d (total days of tracking = 76). Birds were observed to begin soaring approximately 2.5 hr after sunrise with their di- rectional flight commencing approximately 1 hr later. The day’s directional flight ceaSed approximately 2 hr before sunset and soaring ceased 1.5 hr before sunset. The mean distance traveled from roost to roost was 65.3 km (range 12-198 km). Additionally, we were able to estimate the distance of the actual travel path {x = 80.5 km, range 12- 207 km). The estimated travel path averaged 20% greater than the roost to roost distance. The amount of time trav- eled each day ranged from 1.12-8.25 hrs (jc = 4.3 hrs). The average daily speed was 21 km/hr, and the maximum speed recorded Was 78 km/hr. Habitat Utilization by Bald Eagles Wintering in Indiana Fink J.P. 400 Hawthorne, Auburn, IN 46707 US. A, Biweekly helicopter surveys of bald eagle iHaliaeettis leu- cocephalus) activity were conducted from November 1991 through April 1992, using 12 specific routes. The survey routes were characterized as to habitat usage by bald eagles through census and statistical determination of the most influential variables, of interface and creek mouths. Thir- ty-six habitat Variables were noted and measured for 696 eagle sightings. Classification of priority management sites for Indiana Was done based on the presence of high eagle use sites. As eagle nesting season was initiated, a sub- stantial increase in sp>ort fishing activity occurred at several sites, as did human activity — ^particularly on the reservoirs. Total eagle sightings peaked in late January. Immature and juvenile eagles were more easily flushed, while adults and subadult birds were more tolerant Of helicopter dis- turbance. Habitat was segmented into 4-km segments, and analyzed for eagle usage. Waterfowl data and human and boat activity are also correlated with eagle occurrence. There is some evidence to suggest that eagles avoid areas of regular human disturbance, and aggregate in certain other areas. These include the Wabash River stretch near a power plant and protected areas on Monroe Reservoir. Trees selected as perch sites were moM often deciduous trees, 6.5 m from the water’s edge. Wintering eagles uti- lized large reservoirs more often than large rivers. There is also some association between eagles utilizing segments with waterfowl present in peak winter months. How TO Measure a Hawk Migration- Evolution OF THE Quadrant System at the Golden Gate Fish, A.M. Golden Gate Raptor Observatory, Building 201 , Ft. Mason, San Francisco, CA 94123 U.S.A. In the 1980s we Were frustrated trying to apply historical hawk counting techniques to the autumn hawk flight over the Marin Headlands, just north Of San Francisco, Cal- ifornia. The conditions Of the count site— steep topogra- phy, unpredictable fog, and lots of year-round raptor ac- tivity — ^^necessitated that We develop a new system of count- ing as well as a new perspective on What We were mea- suring. In 1989, we began using a quadrant system to record daily rates of visible raptor activity for 19 species, with a primary goal of establishing a consistent and re- peatable measure for use over the long-term. In use through 1993, the 4-mo count has yielded annual rates from 21.5- 43.7 hawks per hour, corresponding with absolute counts ranging from 13 600-22 500 hawk-sightings. I will discuss the pros and cons of hawk counting systems, including the importance of defining specific counting techniques, as- sumptions, and units Of measurement. Fat Content of American Kestrels {FaLCO SPARVERIVS) AND ShARP-SHINNED HaWKS {Accipiter striatus) Estimated by Total Body Electrical Conductivity GeSSAMAN, J.A. and S.M. Harden. Department of Bi- ology, Utah State University, Logan, UT 84322-5305 U.S.A. Total body electrical conductivity (TOBEC) is a nonin- vasive method fOr the estimation of lean mass in live sub- jects. Lipid content can be calculated from the body mass measured and the lean mass estimated from TOBEC. We used live American kestrels {Falco sparverius) to study the accuracy of this method. TOBEC measurements Were compared to actual body content determined by Soxhlet fat extraction using petroleum ether as the solvent. TO- BEC estimated 73.7% of the variation in lean mass in a sample of 21 live kestrels and estimated 83.8% of the variation in lean mass for 21 kestrel carcasses Warmed to 39.8°C. No significant difference was found between the slope or elevation of the calibration lines developed using live or dead kestrels. Body temperature altered the TO- BEC measurements by an average of 1.54% (SE = 0.55) for each 1“C change over a temperature range of 7.0“C (37.3-44.4). The calibration developed for kestrels was used to estimate lean mass and compute fat mass of mi- grating kestrels, sharp-shinned hawks {Accipiter striatus) and merlins (Falco columbarius). The average perOent fat mass of kestrels trapped during migration at Cape May, New Jersey, was 6.01% (SE = 1.92, N — 12) for males 57 March 1995 Abstracts and 8.51% (SE = 2 .o 6/A/^ = 13) for females. The fat mass of sharff-shinned hawks averaged 5.55% (SE = 0.94, N — 53) for males and 10.92% (SE = 0.80, N = 87) for females. Male merlins had an average fat mass of 18.05% (SE = 3.35, N = 7) and females averaged 14.19% (SE = 3.15, N = 8): Nest-switching Behavior in Juvenile Ospreys: A Fortunate Accident or Option for Survival? Gii^ON, L.N. Rdptof Research Center, Department of Biology, Boise Stati University, Boise, ID 83725 US. A. In 1993-94 I examined postfledging behaviors of young ospreys (Pandion haliaettis) at Cascade Reservoir, Idaho. I observed single and three-young broods to examine ef- fects of brood size, food distribution, and competition among nest-niates on subsequent fledgling behaviors. I monitored movements, behavior, and interactions of nine fledglings in 1993 (three from single nests, six from sibling groups) and 16 fledglings (seven singles, nine siblings) in 1994. At least three and possibly six fledglings switched from their natal nest to another nest Occupied by breeding ospreys in 1993. In 1994, three fledghngs have moved to nests oc- cupied by reproductive pairs; one switched into the nest of a nonreproductive pair. Analyses of food intake and behavior at nonnatal nests will indicate whether nest- switching is a behavioral strategy to improve individual fitness or a random event. Reproduction and Distribution of Bald Eagles IN Voyageurs National Park, Minnesota, 1973-93 Grim, L.H. Voyageurs National Park, 3131 Highway 53 S., International Falls, MN 56649 US. A. L.W. KalLEMEYN. National Biological Survey, International Falls Biological Station, 31 31 Highway 53 S., International Falls, MN 56649 U.S. A. The bald eagle iHaliaeetus leucocephalus) is classified as a threatened species in Minnesota. In 1973 the National Park Service began monitoring bald eagle distribution and breeding success within and immediately adjacent to Voy- ageurs National Park, to obtain data that could be used by park management to protect eagles from the impacts of visitor use and facility development. Thirty-seven breed- ing areas were identified from 1973-93. Mean productiv- ity ranged from 0.00-1.42 youhg per occupied nest and averaged 0.68 fOr 21 breeding seasons. The number of breeding pairs tripled and the meah number of young fledged increased fiVe times during the study period. The percentage of success for breeding attempts doubled. How- ever, in over three-fourths of the years, mean productivity and percent nest success iii Voyageurs were below the 1.00 yOiiilg per occupied nest and 70% percent nest success criteria considered necessary for healthy bald eagle pop- ulations. We suspect a complex of variables including toxic substances, human disturbance, severe weather and food source availability in early spring may have kept bald eagles at Voyageurs from achieving productivity levels similar to the nearby Chippewa National Forest popu- lation in northcentral Minnesota. The cumulative effects of these variables on bald eagle productivity and habitat are unknown and should be determined. Breeding pairs preferred pine covered island nest sites on the park’s four major lakes near areas free of ice in early spring. Ninety percent of the 129 nests observed were built in super canopy white pines. Only One nest was built on one of the 31 smaller park lakes. Autumn Movements of Radio-tagged Juvenile Red-tailed Hawks in Central Coastal California Harper, A.B., K.L. Scheuermann, and A.L. FesnDck. Golden Gate Raptor Observatory, Fort Mason, Bldg. 201, San Francisco, CA 94123 U.S, A. From 1990-93, nine juvenile red-tailed hawks (R«teo Ja- maicensis) hdiwc been radiotaggCd in the Marin Headlands, Marin County, California. Each haWk was tracked after release by three teams of volunteers of the Golden Gate Raptor Observatory. The overall movements of these haWks is to the southeast. One bird flew 315 km northwest after release, although it was later rediscovered 200 km south- east of the Headlands. The pattern of these red-tailed hawks is similar to the locations of banded juvenile red- tails recovered within a few months of release. The tagged red- tailed hawks were seen to cross San Francisco Bay without hesitation. Total migration distance for these hawks ranged from 51 km to 445 km, and no bird was observed to travel south of Los Angeles Or east of the Central Valley. These data suggest that many of the juvenile red- tailed hawks passing through the Marin Headlands in autumn are travelling to areas south of Sah Francisco within 100 km of the Pacific coast. Activity and CoRTicosTEROisfE Levels in Food Restricted Postfledging American Kestrels {Falco sparverius) Heath, J. and A.M. Dufty. Department of Biology, Boise State University, Boise, ID 83725 US. A. Departure from the natal area occurs in many bird species during the postfledging period, but the corresponding physiological and proximate factors responsible for this movement remain unclear. Physiological and proximate factors may involve environmental conditions (food avail- ability) , vulnerability to environmental conditions (phys- ical condition), and hormonal responses. Corticosterone is the major hormone involved in stressful situations, such as anticipation of starvation, and may be related to in- creased foraging arid locomotor activity. Iri the laboratory, We studied activity and corticosterone levels in 1 2 post- 58 Abstracts VoL. 29, No. 1 fledging American kestrels {Falco sparverius) taken from nest boxes in southwest Idaho. We removed birds from the box at 23-25 d of age and divided them into three groups. We maintained kestrels at 100%, 90%, or S0% of ad libitum body weights for 21 d. We measured movement with pedometers fitted backpack-style and collected blood samples once/wk. We used radioimmunoassay to measure corticosterone levels. Preliminary analysis suggests there may be a threshold body condition below which birds respond to restricted food by increasing activity levels. Male kestrels may be more sensitive to this threshold than females. Effects of Rotenone Use to Kill “Trash” Fish on Osprey Productivity at a Reservoir in Oregon Henny, C.J. National Biological Survey, 3080 SE Clear- water Drive, Corvallis, OR 97333 U.S.A. J.L. Kaiser. U.S. Fish and Wildlife Service, 11103 East Montgomery, Suite #2, Spokane, WA 99206 U.S.A. We studied ospreys {Pandion haliaetus) nesting at two res- ervoirs in the Cascade Mountains of southern Oregon from 1988-92. Both reservoirs had nesting ospreys present in 1988 (1 1 and 27 occupied nests). Productivity rates at both locations were similar and judged to be excellent in 1 988 and 1989. However, in the autumn of 1989 (after the ospreys migrated south), the reservoir with fewer nesting pairs was treated with rotenone to eliminate the brown bullhead population and any other fish. The reservoir was to be later restocked with rainbow trout. The response of nesting ospreys in 1990, 1991, and 1992 to the elimination of fish in one reservoir in the autumn of 1989 is the subject of this preliminary report. Osprey nest site occupancy, foraging parameters (e.g., dive success and prey delivery rates) and reproductive success are compared between the two reservoirs (rotenone treated versus control with no treatment). U.S. Osprey Nesting Distribution ‘T o Hack or Not to Hack” Houghton, L.M. East Stroudsburg University, East Stroudsburg, PA 18301 U.S.A. L.M. Rymon. Environ- mental Studies Director, East Stroudsburg University, East Stroudsburg, PA 18301 U.S.A. Osprey (Pandion haliaetus) once nested throughout most of the United States. The decline in the osprey population due to biocide use is well documented, as is their recovery following the U.S. ban on DDT in 1972. Henny reported the nesting distribution and abundance of osprey in the U.S. and noted a general increase in the population. How- ever, due to a strong natal site fidelity, inland dispersal had been slow or nonexistent in states with low or extir- pated populations. Therefore, in the early 1980s hacking was initiated as a technique for population restoration. In 1988 Rymon conducted a survey of eleven U.S. states known to have attempted osprey hacking projects. His data indicated that hacking was a viable method for accelerating the slow dispersal of this species. Several other states have inquired about the feasibility of initiating their own hack- ing programs. In an attempt to best address this issue, we have conducted a nationwide nesting survey updating Henny’s 1981 data and constructed a model of current nesting dispersal patterns. We have determined that in states where osprey nesting populations had been low, nesting pairs have increased as much as tenfold, and in Pennsylvania where hacking was initiated in 1980, nesting pairs have increased from 0-19. Eight states that had recorded no known nesting pairs in 1981, now have osprey nesting as a result of hacking projects, and/or natural dispersal. The question remains, should areas where dis- persal is slow choose hacking or waiting as a method of recovery ? Home Range Size and Foraging Habitat Patterns of Red-shouldered Hawks in Managed Pine Forests of Georgia Howell, D.L., C.E. Moorman and B.R. Chapman. Daniel B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602-2152 U.S.A. In the southeastern United States, emphasis on production of pine timber continues to reduce riparian woodland, an important habitat of the red-shouldered hawk (Buteo h- neatus), to narrow corridors and streamside management zones. Loss or alteration of riparian habitat has contrib- uted to regional declines in this hawk throughout its range. Without knowledge of its space and foraging habitat re- quirements in the Southeast, it is difficult to predict or mitigate impacts to the species and its habitats. Therefore, movements of five male and two female red-shouldered hawks fitted with posture-sensitive radiotransmitters were monitored on a 5000-ha study area in the Piedmont phys- iographic region of eastcentral Georgia March to July 1994. Hawk home ranges were estimated based on har- monic mean isopleths and minimum convex polygons. A digital database created with the geographic information system ARC/INFO was used to determine macrohabitat characteristics within home ranges. Selection of foraging habitats was determined by comparing the proportion of observed habitat use, based on the number of radio loca- tions within each habitat, with the proportion of available habitat within hawk home ranges. Vegetative structure and physiography of habitats at both foraging and random locations are also examined. Bald Eagle Surveys in Alaska’s Chilkat Valley, 1984-94 Jacobson, M.J. U.S. Fish and Wildlife Service, 3000 Vin- tage Blvd., Suite 240, funeau, AK 99801-7100 U.S.A. March 1995 Abstracts 59 Alaska’s Ghilkat River Valley attracts North America’s largest gathering of bald eagles {Haliaeetus leucocephalus). Aerial surveys were conducted from 1984-94 to assess the fall abundance and distribution of eagles. Surveys were also flown during the nesting seasons of 1984-87 and 1992 to obtain productivity data. Other studies, using radiote- lemetry, have documented movements into the Ghilkat Valley by eagles from distant locations. Returns of spawn- ing chum salmon (Oncorhynchus keta) have recently de- clined, but still attract large numbers of eagles to the Ghilkat. Fall bald eagle numbers varied from 510-3988. Annual peak counts had a mean of 2500 eagles. The designated critical habitat area held 53% of eagles over all surveys. Most occupied nests were abandoned as the nest- ing season progressed. Only 11% of occupied nests were successful in 1986, 44% in 1987, and an estimated 21% success in 1992. Gompared to the marine coastal environ- ment, most Ghilkat Valley nest territories do not supply a reliable source of food throughout the entire nesting period. The number of human visitors in the summer increased dramatically, and will expand further with the construction of a proposed docking facility to accommodate large cruise ships. Seven Years of Raptor Guild Dynamics in Semiarid Ghile Jaksi6, F.M. Departamento de Ecologia, Universidad Ca- tolica de Chile, Casilla 7 14-D, Santiago, Chile I report a 7-yr ongoing study in the semiarid region of Ghile. Goncurrent with the 1987 El Nino episode of un- usually heavy rains, a small-mammal irruption was able to support as many as 10 vertebrate predator species (four hawks, four owls, two foxes). As mammal populations declined over the following 5 yr, all of the hawks and half of the owls sequentially left the site. A hard core of two owl and two fox species remained despite a 10-fold de- crease in mammalian abundance. A second and milder El Nino event (1992) triggered the recovery of mammal pop- ulations to apparently normal levels (100/ha), and owls first and hawks later began to return to the site. One hawk of the original set is still missing. Mammal irruptions are a built-in component of the site’s dynamics, and predators display two different strategies to cope with it. Some (the hard core) wait out the lean years while others scatter broadly and thinly over the landscape. Given this type of ecosystem, affected by large-scale and temporally unpre- dictable factors such as El Nino events, it is very difficult to design preservation units. These results suggest that it is imperative to protect areas with high habitat diversity (e.g., numerous different slopes, exposures, basins, ravines, elevations) in which mammalian fluctuations in different subsets may be out of phase with one another, as I believe that the spatio-temporal variability in the mammalian prey base is at the root of many of the changes in this predatory guild. Serum Gholinesterase Activity from Migrating Raptors in Utah Kim, D.H. Department of Biology and Ecology Center, Utah State University, Logan, UT 84322-5305 U.S.A. J.R. Parrish. Utah Raptor Flyways, 1065 East Canyon Road, Avon, UT 84328-9801 U.S.A. Since the banning of several organochlorine pesticides in the early 1970s, organophosphate (OP) and carbamate (GB) pesticides have seen increased use. Detection of ex- posure to these compounds involves measuring levels of acetylcholinesterase (AGhE) activity from brain tissue or blood serum. With the exception of a handful of domes- ticated species, there are few published values of brain AGhE activity, and even fewer reported values for serum levels in avian species. We will be reporting reference cholinesterase values from all species of diurnal raptors trapped during 1990 fall migration at Squaw Peak band- ing station in Utah Gounty, Utah and 1993-94 fall mi- gration at Gutler Dam Banding Station in Gache Gounty, Utah. In addition, preliminary data which partially char- acterizes serum acetylcholinesterase in sharp-shinned {Ac- cipiter striatus) and Gooper’s (A. cooperii) hawks will be reported. Postfledging Behavior of Burrowing Owls; Effects of Food Availability on Dispersal Movements King, R.A. and J.R. Belthoff. Raptor Research Center and Department of Biology, Boise State University, Boise, ID 83725 U.S.A. One of the proximate factors that may prompt young birds to leave natal areas is the lack of sufficient food. Young birds may have difficulty locating food after parents ter- minate care and/or prey reserves become depleted. In ei- ther case, young may be forced to seek more abundant prey elsewhere by dispersing. In contrast, if young have easy access to abundant food they may delay dispersal movements or fail to disperse. To investigate the effects of food availability on dispersal, we provided supplemental food to individuals in several family groups of burrowing owls {Speotyto cunicularia) in southwestern Idaho in 1994. Supplemental feeding of dead lab mice and day-old chick- ens began in mid-May and continued until juveniles left their respective natal areas. Our research also examined the behavior of juvenile burrowing owls between the time of fledging and the initiation of fall migration. We radi- otracked both adult and juvenile burrowing owls to ex- amine daily movements in relation to natal burrows, as- sociation of individuals in family groups, and relationships between individuals in neighboring family groups. Our study is designed to determine when juvenile owls attain independence, when young disperse, if food availability influences dispersal, and when adult and juvenile owls 60 Abstracts VoL. 29, No. 1 initiate fall migration. We will discuss findings from the first year of this 2-yr study. Reproductive and Provisioning Behavior of the American Kestrel in Eastern Texas KoncHAR, N.L. Department of Biology, Stephen F. Austin State University, Nacogdoches, TX 75962 V.S.A. D.C. Rudolph. USDA Forest Service, Southern Forest Exper- iment Station, P.O. Box 7600, SFA Station, Nacogdoches, TX 75962 U.S.A. In eastern Texas, American kestrels (Falco sparverius) are uncommon breeding residents presumably of the south- eastern coastal plain subspecies F. s. paulus, which is cur- rently listed as threatened in Florida. The apparent rarity of the breeding population and the population declines in the eastern portion of the subspecies’ range warranted our investigation of American kestrel status and breeding be- havior in eastern Texas from March 1992 to the present. Kestrels are opportunistic foragers; their diet consists of a wide range of prey items, including arthropods, small ro- dents, birds and reptiles, and is highly dependent upon location and season. Our data indicate that the percentage of hcrptiles in the diet of forest residents is much higher than that indicated in the literature for kestrels in other areas of the country. Although some kestrels may feed exclusively on arthropods in winter, breeding kestrels in eastern Texas appear to be nutritionally or energetically dependent on vertebrate prey. In most kestrel pairs, fe- males become sedentary within a small area around the cavity tree two or more weeks before commencing incu- bation. The female remains largely dependent upon her mate for food from this time until approximately 2 wk after the eggs hatch, when she will begin foraging, assisting the male in provisioning the young. We have found that kestrels readily capture green anoles (Anolis carolinensis), which are quite abundant during the breeding season. Field observations to date indicate that eastern Texas res- ident kestrels rely almost exclusively upon a lizard prey base during the provisioning portion of the breeding cycle. Adaptive Radiation in Diurnal Birds of Prey on the Basis of the Jaw Apparatus Ladygin, A.V. Kronotskiy State Biosphere Reserve, Eli- zovo, Kamtchatka Region 684010, Russia The results of morpho-functional analysis of the jaw ap- paratus in the Falconiformes are discussed. The particu- larities of structure and functions of the jaw in different groups of raptors are considered. Adaptive interpretations are presented. Factors perceived to influence the formation of specific groups of birds of prey are presen ted. Vultures are perhaps a very ancient group, but evolution of their jaw apparatus could not originate from accipitrid-like an- cestors. It is not possible to connect the specific morpho- logical adaptations in the Gathartidae jaw and hyoid ap- paratus with their foraging techniques. More probable, Gathartidae peculiarities originate from a more closely tied ancestor who was a near-water bird with a low jaw and a relatively long bill. New World vultures are not con- nected with other Falconiformes in their origin. Perhaps vultures should be more closely connected to Procellari- formes and Pelicaniformes. Scavenging was not a major factor in the evolution of Accipitridae. This group evolved into relatively generalized, active woodland raptor life forms. Home- RANGE and Foraging Behavior of the Ferruginous Hawk in Southcentral Washington Leary, A.W. Department of Biology, Boise State Univer- sity, Boise, ID 83725 U.S.A. M.J. Bechard. Department of Biology, Boise State University, Boise, ID 83725 U.S.A. R. Mazaika. Battelle Pacific Northwest Laboratory, Port- land, OR 97232 U.S.A. We studied movements of six adult male ferruginous hawks {Buteo regalis) nesting on and adjacent to the U.S. De- partment of Energy’s Hanford Site in southcentral Wash- ington, from May through August 1994, using radiote- lemetry. Observations were recorded during all daylight hours to determine daily foraging activity. In addition to foraging, we noted the number of prey deliveries to nests, prey sizes delivered, and the distances prey items were carried to nest sites. Preliminary results indicate home ranges of males nesting on the Hanford Site were similar to those of males nesting off-site. Males nesting both on and off of the Hanford Site used agricultural fields for foraging. All males captured and delivered a variety of small- and medium-sized prey items (i.e., small = mice, shrews, voles; medium = ground squirrels and pocket go- phers) to the nest, but none were observed capturing or delivering any large prey items such as jackrabbits. Assessing Abundance and Nesting Success of Benchland Raptors in the Snake River Birds of Prey National Gonservation Area — An Evaluation of Methods Lehman, R.N., L.B. Garpenter, K. Steenhof, and Michael N. Kochert. Raptor Research and Technical Assistance Center, Boise, ID 83702 U.S.A. From 1991-94, we assessed relative abundance and nest- ing success of ferruginous hawks {Buteo regalis), northern harriers {Circus cyaneus), burrowing owls {Speotyto cuni- cularia), and short-eared owls {Asia fiammeus) in the Snake River Birds of Prey National Gonservation Area (NGA) in southwestern Idaho. This was the first attempt to mon- itor these species in the NGA’s desert uplands. To assess relative abundance, we searched randomly selected plots to locate occupied nesting areas using four sampling meth- ods: variable circular plots, line transects, and quadrats of two sizes. To assess reproductive success, we tried to de- March 1995 Abstracts 61 termine fate at nesting areas found during random sam- pling efforts, at historically occupied nesting areas, and at nesting areas found opportunistically by our study team. In this paper, we compare detection rates for the four sampling methods used for relative abundance assess- ments, discuss potential biases in assessing nesting success, and discuss factors affecting raptor monitoring efforts in a desert area where nesting densities tend to be low. Abundance and Diet of Chilean Spotted Owls in New and Old-growth Forests Martinez, D.R. Departamento de Ciencias Basicas, Universidad de Los Lagos, Casilla 933, Osorno, Chile. F.M. Jaksi6. Departamento de Ecologia, Universidad Catolica de Chile, Casilla 7 14-D, Santiago, Chile We report the first quantitative information on the abun- dance of Chilean spotted owls (Strix rufipes) in six new (DBH 10-50 cm, canopy cover 50-75%, 80-200-yr-old) and five old-growth (DBH >50 cm, canopy cover >75%, >200-yr-old) rainforests of southern Chile. Over 37 nights within a year we surveyed 37 linear kilometers of new and 49 km of old-growth forests, detecting by calls the presence of four and 11 spotted owl pairs (0.11 and 0.22 pairs/km), respectively. This difference was marginally significant at P — 0.08. Pooling all data and applying a stepwise regression with five supposedly independent but highly correlated variables, canopy cover accounted for 68% of the variance in owl abundance using a maximum improvement procedure (reduction in residual variance). Mean DBH and snags/ha accounted for only 4% of the unexplained variance. Elevation and age accounted for very little of the residual variance. When removing canopy cover from the stepwise regression, mean DBH accounted for 34% of the variance in owl abundance; adding snag/ ha improved it negligibly, and age explained <8% of the residual variance. We also collected 161 pellets over 4 yr in two patches of old-growth forest, and identified 376 prey items. Insects, amphibians, and birds accounted for 3 3, 0.5, and 1.5% of the prey by numbers, and mammals for the remainder. Among the latter, an arboreal mouse (Irenomys tarsalis = 42 g) and an arboreal opossum {Drom- iciops australis = 34 g), together with a scansorial mouse {Oryzomys longicaudatus — 26 g), accounted for >72% of the total prey consumed. Changes in Golden Eagle Reproductive Success in Denali National Park, Alaska, 1988-94 McIntyre, C.L. National Park Service, Alaska Regional Office, 2525 Cambell Street, Anchorage, AK 99503 U.S.A. Since 1988 I have studied the reproductive success of gold- en eagles {Aquila chrysaetos) in a 2500 km^ study area in Denali National Park, Alaska. Nesting territory occupan- cy, the percentage of territorial pairs nesting, nesting suc- cess and productivity were measured at >60 nesting ter- ritories each year. Data were collected using two system- atic aerial surveys each year. The first annual survey was conducted during incubation in late April and early May to document nesting territory occupancy and nesting at- tempts. A territory was defined as occupied if evidence of a territorial pair was observed during the first annual survey. A pair was considered to be nesting if incubating adults or eggs were observed in a nest during the first annual survey. The second annual survey was conducted in the late nestling stage in late July, when most nestlings had reached >80% of their fledging age, to document nesting success and productivity. Nesting success was de- fined as the percentage of territorial pairs that successfully raised > one fledgling and productivity was defined as the number of fledglings raised per occupied nesting territory. Nesting territory occupancy remained relatively stable (range: 65-87%) among years; however, between 1989 and 1994, the percentage of territorial pairs nesting decreased from 88% to 33%. Over the same time period, nesting success decreased from 71-15% and productivity decreased from 1.22-0.17 fledged young per occupied nesting ter- ritory. Decreases in the percentage of pairs nesting, nesting success and productivity coincided with observed decreases in the number of snowshoe hare {Lepus americanus) and willow ptarmigan {Lagopus lagopus) in the study area among years from 1989-94. I suggest that food supply, particu- larly prior to laying, has a strong influence on whether golden eagles lay eggs. Furthermore, I suggest that food supply after laying influences nesting success and pro- ductivity. Opportunistic Response by Captive Northern Hawk-Owls {Svrnia ulula) to Overhead Corridor Routes to other Enclosures, for Purposes of Social Encounters McKeever, K. The Owl Foundation, R.R. 1 , Vineland Station, Ontario, LOR 2E0 Canada The Owl Foundation is a behavioral observation center, affording permanently damaged, wild, native owls the op- portunity to make choices of territories and potential mates within extended cage complexes. Many observations are through video monitoring devices. Of 54 compounds cov- ering 1.6 ha, seven, on 0.2 ha of forested slope, are des- ignated for the northern hawk owl (Surnia ulula), a species seldom studied in North America. Some 15 yr of contin- uous observation suggest that this nomadic species quickly exploits any new opportunity for investigation. Ten in- dividuals, evenly divided by sex, inhabit these seven en- closures totalling 1160 m^, with six connecting overhead corridors from 1.5-6 m in length. Gates in corridors are opened by March, allowing travel by all residents to any part of the seven-cage complex. Both sexes seize this op- portunity to explore vocally advertised assets, although females more regularly return to familiar territories, often followed by males. Others may solicit males from ‘home’ 62 Abstracts VoL. 29, No. 1 base. Breeding occurs each year with equal success in either male or female ‘owned’ enclosures. An alternate corridor route, opened each September, allows flighted young to vacate parental territories and travel to a more remote overwintering enclosure (with live prey predation and early spring release). Parents do not follow their young. Finally, most corridors are closed again by November when the adults have established winter routines. By this time there is no evidence for recognition of partners of the previous spring. Tracking the Migrations of 30 Raptors by Satellite Meyburg, B.-U. and C. Meyburg. World Working Group on Birds of Prey and Owls, Wangenheimstr. 32, D-14193 Berlin, Germany During the period July 1992 to July 1994 we fitted 30 eagles (10 Aquila nipalensis, \ 0 A. pomarina, three A. clanga, four A. heliaca, one A. wahlbergi, one Haliaeetus albicilla and one H. pelagicus) with satellite transmitters (PTTs) of different sizes (28-95 g). All steppe eagles were caught m Saudi Arabia in October except one immature which was caught in March. All young and most adult steppe eagles migrated into Africa via Bab el Mandeb. From there they dispersed in various directions. One adult and one immature bird turned north and wintered in Ethiopia, Sudan and Chad. One adult female was tracked for over 15 000 km all the way from Saudi Arabia to southern Africa and back to its breeding grounds in Kazakhstan via Suez and Eilat. It stayed in its wintering grounds from 22 November until 29 January, spending most of the time in Botswana. The spring migration lasted from 1 February until 24 March. An adult greater spotted eagle wintered in southwestern Saudi Arabia from 29 October until 24 November, afterwards in northern Yemen east of Saana. It departed on 2 February and arrived in its breeding grounds in western Siberia northwest of Omsk on 21 April. A young lesser spotted eagle from Latvia took one month to arrive in the largest African wetland area, the Sudd in Sudan (ca. 6000 km from the breeding area), where it remained for over 6 wk. It then went into the Serengeti NP and Masai Mara Reserve on the border of Tanzania and Kenya. A new generation of solar-powered transmit- ters has become available in 1993 which gives some hope that the movements of at least large species could be studied in greater detail and for longer periods in the future. Such a transmitter has been fitted to a juvenile sea eagle in Germany. During the first year of its life 877 satellite locations were obtained, each location corresponding to a customarily obtained “recovery” of a ringed bird. Many of the PTTs are still presently active. Nest Site Macrohabitat Selection by Woodland Hawks on a Managed Forest in the Georgia Piedmont Moorman, C.E., D.L. Howell and B.R. Chapman Daniel B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602-2152 US. A. In the southeastern United States, major emphasis in forest management is directed toward increased timber produc- tion. If wildlife management and increased timber pro- duction are to coexist, relationships between wildlife hab- itat preferences and silvicultural practices must be better understood. Previous research on woodland hawks deter- mined that nest site selection occurs at a microhabitat level. However, it is difficult for a land manager to select for habitat characteristics on a small scale. It is more practical to design management schemes that aim for critical mac- rohabitat types. In 1994, 12 red-shouldered hawk {Buteo lineatus) and 10 red-tailed hawk {B . jamaicensis) nests were located on a 5000-ha wildlife management area in the Georgia Piedmont. Nest site macrohabitat preferences were examined using a geographic information system (GIS). Hardwood habitat was separated into upland and bottom- land macrohabitat types, and pine habitat was separated by age and structural characteristics into six macrohabitat types. Using the GIS, three concentric circles of increasing size were created around each nest. Macrohabitat per- centages within each concentric circle were compared to total percentages available on the study area. Circle ma- crohabitats that occurred in higher proportions than ex- pected based on total availability were considered critical. Breeding Biology and Nest Success of Florida’s Crested Caracaras Morrison, J.L. Department of Wildlife and Range Sci- ences, University of Florida, 118 Newins- Ziegler, Gaines- ville, FL 32611 U.S.A. Breeding chronology, nest success, and productivity of the crested caracara (Caracara plancus) in southcentral Florida were examined for 28 nests during the 1993-94 breeding season. Reproductive activity was documented from Oc- tober through June; peaks of the incubation, nestling, and fledging periods occurred in January, February, and early April respectively. Nests were monitored weekly to deter- mine clutch size, laying, hatching, and fledging dates. I estimated weekly Mayfield and traditional nest success and survival probabilities for the incubation, nestling, and fledgling dependency (8 wk postfledging) periods for each nest. Total Mayfield probability of success for each period was 0.74, 1.00, and 0.90 respectively and for all three periods combined for 28 nests was 0.66. Twenty-five nests successfully fledged young (89%), two failed during in- cubation, and one failed just after fledging. Most nests produced two fledglings (53%). At five nests (18%), three fledglings were successfully raised to the end of the fledg- ling dependency period. Productivity for all nests was 1.6. Survival probabilities were also estimated for each egg for all three periods. We documented three cases of double brooding; in all cases the fledglings from the first nest March 1995 Abstracts 63 effort remained in the territory well into the nestling period of the second brood and continued to be fed by the parents. Despite apparent high nest success, continued observation of marked birds suggests much lower recruitment. After the fledgling dependency period, juvenile mortality greatly increases, primarily due to collisions with vehicles. Metabolic Basis for Glucose Intolerance in Raptors Myers, M.R. and K.C. Klasing. Department of Avian Sciences, 3202 Meyer Hall, University of California, Davis, CA 95616 US, A. Anecdotal reports have suggested that raptors are rela- tively intolerant to glucose and in some cases have died after receiving glucose i.v. or subcutaneously. It was of interest to find the mechanisms responsible for their in- tolerance and to access their adaptability to a diet con- taining glucose. Nonreleasable barn owls {Tyto alba) and white leghorn chicks {Callus domesticus) (6 wk) were fed a LPHG (33.44 Protein: 23.67 CHO: 29.96 Fat: 12.93 Ash) diet and HPLG (55.35 Protein: 1.5 CHO: 29.98 Fat: 13.17 Ash) diet for 8 d. Birds were subjected to a glucose tolerance test (1 g glucose/kg of body weight, i.v.) and hepatic glucose metabolism was examined. LPHG diet significantly (P = 0.005) decreased baseline glucose levels in both species yet did not alter the shape of the glucose tolerance curve. Chickens, regardless of diet, reached a peak of 400 mg glucose/dL and took 1 hr to return to baseline while owls peaked at 700 mg glucose/dL and took 3.5 hr to return to baseline. These species differences were significant at P = 0.0001. Malic enzyme (ME) in- creased and alanine aminotransferase (ALT) decreased significantly with LPHG feeding in the chicken but only ALT significantly decreased in the owl. All enzymes mea- sured significantly differed across species with large dif- ferences {P = 0.0001) in glucokinase (GK), ME (five and three times higher, respectively, in chickens), and phos- phoenolpyruvate carboxykinase (PEPCK; three times higher in owls). In vitro experiments revealed that chicken hepatocytes partitioned five times more lactate to glucose as compared to owl hepatocytes, yet owls partitioned three times more threonine to glucose than chickens. It appears from these studies that the owl may be intolerant to glucose because of low enzyme adaptability, low GK activity, and a failure to suppress gluconeogenesis in presence of ex- ogenous glucose. Due to these results it is recommended that injured raptors in need of glucose be given small doses of glucose over time. Sex Allocation in the American Kestrel: Is It Related to the Phenotype of the Parents? Negro, J.J. and D.M. Bird. Avian Science and Con- servation Centre, McGill University, 21,111 Lakeshore Road, Ste. Anne de Bellevue PQ^HQX 3V9 Canada In the case of the American kestrel {Falco sparverius), Wiebe and Bortolotti (1992, Behav. Ecol. Sociobiol. 30:379- 386) reported that small females produced more sons. This could be an adaptive mechanism given than males are smaller and possibly less costly to rear. To determine whether kestrel sex-ratios can be manipulated we con- ducted an experiment on captive American kestrels main- tained at McGill University in 1994. All 300 birds in the colony were weighed and measured (wing chord). The smallest 20 males were paired to the smallest 20 females Conversely, the largest 20 males were paired to the largest 20 females. Small parents reared 16 broods, 10 (63%) of which were male-biased. Sex ratio was 55% males {N = 56). Large parents reared 14 broods, eight (57%) of them male-biased. Sex ratio was 527o males {N = 44). Differ- ences between the two groups were not statistically sig- nificant. Ecology of Bald Eagles Wintering and Breeding near Caballo Reservoir, New Mexico Nicholopoulos, J.E. New Mexico Cooperative Fish and Wildlife Research Unit, Department of Biology, New Mex- ico State University, Las Cruces, NM 88003 U.S.A. P.J. Zwank. National Biological Survey, New Mexico Coop- erative Fish and Wildlife Research Unit, Las Cruces, NM 88003 U.S.A. W.J. Boecklen. Department of Biology, New Mexico State University, Las Cruces, NM 88003 U.S.A The bald eagle (Haliaeetus leucocephalus) was listed as an endangered species in the United States in 1978. Intensive state and federal efforts to protect habitat and nest sites have contributed to downlisting in 1994 from endangered to threatened for all but the southwestern population. The number of bald eagles wintering in New Mexico has in- creased from 175 recorded in 1984 to 478 in 1994; how- ever, there are only two known active nests in New Mex- ico. This project was initiated to determine if reservoir pool size affects bald eagles wintering and breeding near Caballo Reservoir, New Mexico. Bald eagles wintering on the reservoir were censused by boat or truck from December 1992 through March 1993, and December 1993 through March 1994. Concomitantly, aerial census sur- veys were performed throughout the middle Rio Grande valley. Behavioral observations were recorded during both winter periods; foraging behavior, perch use, and food habits documentation were the major areas of emphasis. Caballo Reservoir was sampled every three weeks during winter months to determine fish (prey) availability. Op- timal foraging experiments were conducted on wintering eagles during 1993 and 1994. The pair of breeding bald eagles that nest near Caballo Reservoir were observed in 1993 and 1994. Two eaglets successfully fledged during the 1993 breeding season, while one eaglet fledged in 1994 (the other egg failed to hatch). Nest observations indicated fish, predominantly gizzard shad (Dorosoma cepedianum), were the most common prey item delivered to the nest 64 Abstracts VoL. 29, No. 1 Data will be compiled, analyzed, and utilized in the con- struction of a diurnal time budget and an energetics sim- ulation model. Salt River Project’s Avian Protection Program Nobel, T.A. Salt River Project, Environmental Affairs Division, P.O. Box 52025, Phoenix, AZ 85072-2025 U.S.A. Salt River Project (SRP), an electric and water utility, has had an Avian Protection Program in continual develop- ment since the 1980s. The Avian Protection Program is aimed at protecting birds from harmful contact with elec- trical distribution facilities. Although the program strives to protect all migratory birds, an emphasis is placed on raptors because of their larger wingspan. The most com- mon raptor species to interact with power facilities in the Phoenix, Arizona, area include the Harris’ hawk (Para- buteo unicinctus), red-tailed hawk {Buteo jamaicensis), and great horned owl {Bubo virginianus). SRP protects birds from the electric system in a number of ways. For all new construction, bird protection measures include insulating “jumper” wires, capping transformer bushings and coating transformers with nonconductive paint. Other system re- visions include installation of perches and visual deter- rents, or changes in equipment configuration. The pro- gram also includes partnerships with Arizona Game and Fish Department and Liberty Wildlife Rehabilitation Foundation. Compliance with the Migratory Bird Treaty Act is ensured through permits obtained from U.S. Fish and Wildlife Service. SRP has been tracking bird mor- talities and collecting data including species and location for several years. This information is now being interfaced with a GIS system of the distribution system. The graphic interface enables SRP to identify problem areas and pri- oritize where upgrades of older systems are needed. This proactive approach allows SRP to complete system cor- rections before additional electrocutions can occur. Dispersal and Habitat Selection of Released Aplomado Falcons Perez, C.J. Department of Fishery and Wildlife Sciences, New Mexico State University, Las Cruces, NM 88003 U.S.A. P.J. ZWANK. National Biological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, New Mexico State University, Las Cruces, NM 88003 U.S.A. Aplomado falcons {Falco femoralis) were last recorded in the United States in the 1950s. A priority of the recovery plan is to reintroduce this endangered species in suitable habitats in the United States. As a result of a joint venture between The Peregrine Fund and the U.S. Fish and Wild- life Service, 26 young-of-the-year aplomado falcons were released into the wild in 1993 and 12 during 1994. These falcons were released at Laguna Atascosa National Wild- life Refuge, an 18 000-ha coastal refuge approximately 32 km north of Brownsville, Texas. The young fledgling falcons were recaptured after about 3 wk and tail-mounted radiotransmitters were attached. Ten aplomado falcons with operational transmitters were monitored for 6 mo in 1993. Only four mortalities were confirmed. Thus far, in late 1994, six aplomados are currently being monitored. Monitoring of released falcons is conducted for at least 6 mo or until the transmitter fails. In 1993 dispersal dis- tances ranged from 2-16 km. Average daily movements between roost and forage sites averaged about 5 km. Pre- ferred habitats appear to be coastal grasslands adjacent to marshy areas or saltflats containing scattered mesquite {Prosopis glandulosa) and yucca {Yucca treculeana). Dom- inant vegetation at forage sites is typically less than 60 cm tall with patches of bare ground. Factors Limiting a Population of Tawny Owls in a Coniferous Forest in Northern Britain Petty, S.J. and D.I.K. Anderson. Forestry Authority, Wildlife Ecology Branch, Ardentinny, Dunoon, Argyll PA23 8TS Scotland. The number of occupied tawny owl {Strix aluco) territories increased during 1981-91, while reproduction and turn- over in the owl population varied greatly in response to a 3-yr cycle of field vole {Microtus agrestis) abundance. The increasing number of occupied owl territories resulted ul- timately from an improvement in the carrying capacity of the forest for tawny owls, although the increase in owls lagged behind the habitat improvements. To facilitate this increase, the resident territorial owl population received more recruits than was necessary to replace losses, and recruitment was the proximate factor most closely asso- ciated with year-to-year changes in the number of occupied territories. Recruitment was also influenced by the stage of the vole cycle. In years when vole numbers Were in- creasing, virtually all birds in the nonterritorial sector were recruited. In years when vole numbers were declining or low, only some of the nonterritorial owls were recruited and most deferred recruitment until vole numbers in- creased. Wintering Ecology of Prairie Falcons in the Snake River Birds of Prey National Conservation Area Prokop, R.S. Department of Biology, Boise State Univer- sity, Boise, ID 83725 U.S.A. J.M. Marzluff. Greenfalk Consultants, Inc., Boise, ID U.S.A. 83709 U.S.A. We determined differences in winter home ranges and observed hunting attempts of nine male and six female prairie falcons {Falco mexicanus) trapped in the Snake River Birds of Prey National Conservation Area (SRBOPNCA) in Idaho, between November and March, 1993. Winter home ranges of females were not larger than males. Successful capture attempts suggest prairie falcons prey mainly on horned larks {Eremophila alpestris) (seven March 1995 Abstracts 65 of nine successful attempts). There appears to be two groups of falcons wintering in the SRBOPNCA; those that bred there the previous summer and those that mi- grated into the SRBOPNCA. The sex ratio of the nine breeders that remained was significantly biased toward males (nine males: one female; = 4.01, P < 0.05). However, the sex ratio of the 17 birds trapped during the winter (that likely migrated into the SRBOPNCA) was not significantly dififerent from a 1:1 ratio (10 males: seven females; ~ 1.41, P < 0.25). We will discuss different migration strategies, methodology, climatology, and status of resource base as alternative explanations for the dif- ference in sex ratios between the two groups of wintering prairie falcons. Responses of Great Horned Owls {Bubo virginianus) TO THE SNOWSHOE HaRE CyCLE IN THE Boreal Forest Rohner, C. Department of Zoo logy j University of British Columbia, Vancouver, BC V6T 1Z4 Canada Great horned owls {Bubo virginianus) were studied in the subarctic boreal forest in the southwestern Yukon from 1988-93. During the increase phase of the population cycle of snowshoe hares {Lepus americanus), almost all resident owl pairs bred and raised large broods. Survival of young owls in their first two years of life was high, and two females were observed to breed as yearlings. Densities of territorial owls almost doubled, but most juveniles be- came nonterritorial ‘floaters,’ presumably because social behavior was limiting the number of territories. Floaters were silent, their ranges overlapped with territories, and their density reached 40-50% of the total population. As snowshoe hares declined, the number of recruits dropped sharply. Postfledging mortality was high, and the role of predation and disease in interaction with food shortage are evaluated. Overall mortality and emigration increased earlier for floaters than for territorial birds as hare den- sities further declined. A behavioral mechanism for the time lag in the numerical response to the hare cycle is proposed, and constraints to increase reproduction at high prey densities are interpreted in the context of life history evolution. Grassland Passerines as Indicators of Habitat Use by Northern Harriers in Reclaimed Surface Mines of Pennsylvania Rohrbaugh, R.W. and R.H. Yahner. School of Forest Resources, The Pennsylvania State University, University Park, PA 16802 U.S.A. We documented the presence of grassland passerines as- sociated with areas used by northern harriers {Circus cy- aneus) in reclaimed grassland surface mines of Pennsyl- vania. Reclamation of surface mines in Pennsylvania has created suitable grassland habitat for nesting and foraging harriers and other grassland avifauna. This research was part of a long-term research project that examines the status and the management of northern harriers in Penn- sylvania. Our objective was to determine if grassland pas- serines can be used as indicators of suitable harrier habitat We surveyed and compared communities of grassland pas- serines associated with sites frequently used by harriers (harrier observation sites) to three types of randomly se- lected sites that were infrequently or unused by harriers. Harrier observation sites and random sites were selected based on approximately 124.9 hr of surveying for harriers along 108 km of survey routes that transected reclaimed surface-mine habitat. Three of 10 grassland passerine spe- cies that commonly were associated with harrier obser- vation and random sites significantly differed among site types. Bobolinks {Dolichonyx oryzivorus) {P < 0.001) and Henslow’s sparrows {Ammodramus henslowii) {P < 0.01) were observed more frequently than expected at harrier observation sites, whereas chipping sparrows {Spizella pas- serina) were observed less frequently than expected {P < 0.025) at these sites. Results of this research are being used to develop management recommendations for harriers and grassland passerines using reclaimed surface mines. Nest-site Fidelity of Cooper’s Hawks in Wisconsin RosenfIELD, R.N. Department of Biology, University of Wisconsin, Stevens Point, WI 54481 U.S.A. J. BlELE- FELDT. Park Planning, Racine County Public Works, Stur- tevant, WI 53177 U.S.A. Long-term data on nest-site fidelity on Cooper’s hawks {Accipiter cooperii) is unavailable. Captures of 154 separate individual breeding male Cooper’s hawks at 102 nesting areas during 1980-94, plus 86 recaptures of 60 marked males at 45 nesting areas were used to examine nest- site fidelity in Wisconsin. All recaptured males were found on sites where originally trapped; no movement was detected Detections of inter-year movements in breeding females and natal dispersal of both sexes, and other lines of evi- dence indicated that our sample sizes offered adequate opportunity to detect potential breeding dispersal in males. We suggest that breeding male Cooper’s hawks in Wis- consin exhibit lifetime nest-site fidelity. Breeding Biology, Diet, and Hunting Behavior of Plumbeous Kites {Ictinia plvmbea) in Tikal National Park, Pet6n, Guatemala Seavy, N.D. 17142 Lemolo Shr. Dr. N.E., Poulsbo, WA 98370 U.S.A. M.D. Schulze. 215 Chatham Rd., Colum- bus, OH 43214 U.S.A. M.A. VaSQUEZ. Parque Nacional Tikal, Peten, Guatemala. D.F. Whitacre. The Peregrine Fund, Inc., Boise ID 83709 U.S.A. We studied the breeding biology of the plumbeous kite {Ictinia plumbea) in Tikal National Park, Peten, Guate- 66 Abstracts VoL. 29, No. 1 mala during 1992, 1993 and 1994. Seven of 12 nests failed during incubation, and of the five young that hatched, four survived to fledging age. All clutches documented were of a single egg. Incubation periods of 32 and 33 d were recorded for two nests. Nestling periods for the four suc- cessful nests were 36, 39, 39 and 40 d. Males and females shared tasks of incubation, and of delivering prey to the nest and feeding chicks. Insects made up 73-95% of the prey items delivered to the nest. Lizards, bats, birds, frogs and snakes were also recorded as prey items. Plumbeous kites hunted on the wing, while soaring over the canopy, and by making short flights or stoops from perches. Though most insects were plucked from the air, a smaller per- centage of insects and other prey items were captured when the kites snatched them from the forest canopy. Spatio- temporal patterns of insect abundance have probably ex- erted a strong influence on the evolution of plumbeous kite breeding biology and behavior. A Phylogenetic Analysis of the Avian Family Accipitridae Based on Molecular Data SheeHY, R.R. Committee on Genetics, University of Ari- zona, Tucson, AZ 85721 U.S.A. K.K. OlSHl. Committee on Genetics, Molecular and Cellular Biology Department, and Plant Sciences Department, University of Arizona, Tucson, AZ 85721 U.S.A. The avian family Accipitridae is a large, diverse family composed of approximately 230 species divided into 56 genera. The evolutionary relationships among accipitrid taxa have been examined previously using phenetic and parsimony approaches against a variety of data sets rang- ing from behavior to karyotypic. These studies have re- sulted in conflicting phylogenies, presumably due to the high level of homoplasy, perhaps, the result of morpho- logical convergence on diet. We analyzed DNA sequence data from the mitochondrial encoded cytochrome-b gene using maximum parsimony, distance and maximum like- lihood methods to explore the phylogenetic relationships among the major morphological lineages within Accipit- ridae. Additionally, an analysis of branch lengths between nodes was made under the assumptions cytochrome-b evolving in a clock-like fashion and with differing rates of evolution over time. The major findings in this study in- clude support for the polyphyly of the kite genera and the sister group relationship of the osprey {Pandion haltaetus) with accipitrid taxa, and evidence for a number of periods of rapid morphological diversification. Dichromatism in the Genus Falco: Sexual Selection Versus an Adaptive Peak Smallwood, J.A. Department of Biology, Montclair State University, Upper Montclair, Nf 07043 U.S.A. M.P. Moulton. Department of Wildlife and Range Sciences, University of Florida, Gainesville, FL 32611 U.S.A. D.K. McLain. Biology Department, Georgia Southern Univer- sity, Statesboro, GA 30460 U.S.A. Approximately one-fifth of all species in the genus Falco exhibit marked sexual dichromatism. In the absence of substantial differences in diet or foraging behavior between the sexes, it is likely that dichromatism evolved in response to sexual selection (e.g., mate attraction) rather than to natural selection. Falcons exhibit considerable interspecific variability in diet and in the manner in which prey are captured, ranging from invertebrates and small mammals captured on the ground to birds captured in flight. A number of morphological characteristics, including tarsal length, toe length, overall body size, and the degree of sexual size dimorphism, have been suggested to be adaptive to the specialized foraging niche of aerial avivory. In this study, we examined the associations among dichromatism, foraging niche (bird specialist or not), body size (based on an analysis of log-transformed body mass and wing length), and body size dimorphism. The results support the view that large falcons tend to be monochromatic bird-eaters exhibiting a large degree of size dimorphism. However, in contrast to widespread perception, foraging niche was not significantly related to size dimorphism; for many bird specialists, the female is not much larger than the male. Because foraging specialists likely occupy a steeper adap- tive peak, and therefore lack the evolutionary plasticity to withstand much sexual selection, we expected dichroma- tism to be significantly more common among foraging generalists. Indeed, the merlin (F. columbarius) is the only falcon species that is both dichromatic and a bird specialist. Relationships between Habitat Selection and Productivity of Red-shouldered Hawks in New Jersey and New York Speiser, R. 13 Beam Place, Haledon, Nf 07508 U.S.A. T. Bosakowski. Department of Biological Sciences, Rut- gers University, Nf 07102 U.S.A. (present address: Beak Environmental Consultants, 12931 NE 126th Place, Kirk- land, WA 98034 U.S.A.) Thirty red-shouldered hawk {Buteo lineatus) nests were monitored for productivity and habitat structure was mea- sured. Stepwise multiple regression (SMR) analysis was run for mean annual productivity versus habitat variables. A separate analysis was run for macrohabitat (landscape level), microhabitat (stand level), tree species composition, and nest tree parameters. The macrohabitat SMR indi- cated higher productivity was correlated with greater dis- tance to human habitation (i.e., less forest fragmentation and disturbance) and at lower elevations (i.e., more wet- lands). The microhabitat SMR indicated higher produc- tivity with greater tree densities in the 40-50 and 70+ cm diameter classes and higher percent decadence, parameters associated with older growth stands. The tree species SMR indicated that nest stands with higher relative dominance March 1995 Abstracts 67 of yellow birch {Betula papyrijera) and northern red oak (Quercus rubra) were correlated with higher productivity, although overall, eastern hemlock {Tsuga canadensis) had the highest mean relative dominance. The nest tree SMR indicated that nest tree selection did not effect productivity. Present Southern Breeding Limits of the Boreal Owl in North America StaHLECKER, D.W. Eagle Ecological Services, 30 Fonda Road, Santa Fe, NM 87505 U.S.A. B. Duncan. South- western Field Biologists, 8230 E. Broadway Blvd., Suite W-8, Tucson, AZ 85710 U.S.A. Existence of breeding boreal owls (Aegolius funereus) in North America south of Canada was unknown in the 1950s, but by 1989 residency of the species had been documented to the southern terminus of the Rocky Moun- tains in northern New Mexico. We conducted surveys using tape playback of the staccato song to consolidate distributional data in northern New Mexico (63 hr) and to search for the species in isolated mountain ranges in central and southwestern New Mexico (27 hr) and on the Colorado Plateau of Arizona (280 hr). Eleven additional records between November 1989 and August 1993, in- cluding two of fledged juveniles, firmly establish the boreal owl as a breeding bird in the Sangre de Cristo, San Juan, and Jemez Mountains of northern New Mexico. Response rates of boreal and northern saw-whet owls {Aegolius acad- icus) in northern New Mexico were 0.15 and 0.08 owls/ survey hour, respectively. In mountain ranges apparently not occupied by boreal owls, northern saw-whet owls re- sponded at a rate of 0.11 owls/survey hour; their response rate was higher in New Mexico (0.44/survey hour in 27 hr) than Arizona (0.08/survey hour in 280 hr). This dif- ference was most likely due to sample size and timing of surveys: summer-autumn in New Mexico, spring in Ar- izona. Potential habitat for boreal owls away from the Rocky Mountains was generally isolated, small patches that likely would not sustain minimum viable populations. We continue to believe that the boreal owl in the Rocky Mountains is a pleistocene relict, and the inhospitable nature of their high elevation spruce-fir {Picea engelmanm- Abies spp.) habitat during their most vocal period (Feb- ruary to April) hindered scientific knowledge. Palentolog- ical, archeological, and late 18th- to early 19th-century autumnal sightings in the southern Rockies support this view, despite current efforts to suggest a more recent range expansion. Nest Box Fidelity and Dispersal Distances of American Kestrels in Southwest Idaho, 1993-94 Steenhof, K. Raptor Research and Technical Assistance Center, National Biological Survey, Boise, ID 83705 U.S.A. G. Carpenter and M. Drysdale. Department of Bi- ology, Boise State University, Boise, ID 83725 U.S.A. Few individuals marked as breeding adults in 1993 re- turned to breed in the same box in 1994. Of 37 females marked as breeders in 1993, only three returned to nest in the same box in 1994; two of 22 males reused their 1993 boxes. Four males marked in 1993 moved to different boxes within the study area, 0.4 to 4.6 km from their 1993 boxes. Despite banding nearly 600 nestling kestrels in our study area, we have encountered only six breeding kestrels (five females and one male) that were originally marked as nestlings in the study area. Females moved an average 9.9 km from their natal boxes to their breeding boxes (range: 8.3-10.8 km; SD = 1.03), and the male moved 7.6 km. We suspect that our low return rate and the low reuse of boxes is associated with high mortality, availability of alternative nesting substrates, or a combination of the two Red-shouldered Hawk Reproductive Success within Pools 9-11 of the Upper Mississippi River, 1983-94 Stravers, J.W. Midwest Raptor Research Fund, P.O. Box 32, Pella, I A 50219 U.S.A. K.J. McKay. Midwest Raptor Research Fund, 6143 34th Ave., Moline, IF 61265 U.S.A. E. Nelson. Upper Mississippi National Wildlife and Fish Refuge, USD I Fish and Wildlife Service, 151 E 4th St., Winona, MN 55987 U.S.A. Between 1983 and 1994, we monitored 84 red-shouldered hawk {Buteo lineatus) nesting attempts at 15 territories within the McGregor District of the Upper Mississippi River National Wildlife and Fish Refuge (pools 9-11). Of the 60 attempts with known outcomes, 43 were suc- cessful (71.7%) and 17 were unsuccessful (28.3%). The 43 successful nesting attempts produced 91 red-shouldered hawk fledglings, for an average of 2.12 per successful nest and 1.52 per nesting attempt. Production varied during the study period. Between 1983 and 1989, 20 of 24 (83.3%) nesting attempts were successful; a total of 49 fledglings were produced for an average of 2.45 per successful nest and 2.04 per nesting attempt. However, between 1990 and 1994 production was considerably lower; of 36 known outcomes, 23 (63.87o) were successful and average number of fledglings dropped to 1.83 per successful nest and 1.17 per nesting attempt. Red-shouldered hawk reproduction was especially poor during the record floods of 1993. Flood waters covered shallow wetlands and other feeding areas as well as many of the nest sites causing fledglings to drown when they left the nest. Only four (36.4%) of eleven at- tempts were successful and the number of fledglings dropped to 1.24 per successful nesting attempt and 0.45 per nesting attempt. Also, during the following season, at least four confirmed nesting territories were abandoned, and we ob- served only one juvenile red-shouldered hawk. Conse- quently, we suspect that replacement rates within the study area may not be satisfactory. 68 Abstracts VoL. 29, No. 1 Ecology of the Crane Hawk in Tikal National Park, Pet6n, Guatemala Sutter, J. Raptor Research Center, Department of Bi- ology, Boise State University, Boise, ID 83725 U.S.A. The breeding ecology of the crane hawk (Geranospiza ca- erulescens) was studied from 19 February to 15 July 1994 in Tikal National Park, located in the northern depart- ment of the Peten, Guatemala. This research is part of a comprehensive study of raptors being conducted by The Peregrine Fund, Inc.’s Maya Project in Guatemala, Mex- ico, and Belize. Areas of crane hawk activity were located from observation points in canopy-emergent trees, via foot searches, and by vocalizations. Breeding and nonbreeding crane hawks were monitored to estimate density within the park. Measurements of nesting habitat were collected for both active and historic nest sites. In 1994, five active nests were located and studied in the park. Growth and development of six nestlings were measured. Rodents (Heteromyidae and Muridae) comprised 56.3% of 87 iden- tified prey items in the diet while frogs, lizards, birds, bats, and snakes made up the remainder. Adult crane hawks were fitted with radiotransmitters to estimate home ranges, movements after breeding and habitat use. To study post- fledging dependency and dispersal, one male fledgling was fitted with a radiotransmitter. Preliminary conclu- sions of the first year of a 2-yr study indicate that certain nesting habitat components, as well as intra- and inter- specific interactions are important factors influencing nest- ing success and productivity. DNA Fingerprinting Reveals Successful Polygyny in the Lesser Kestrel (Falco naumanni) Tella, J L , J J Negro, F. Hiraldo and J.A. DoNAZAR. Estacion Biologica de Donana, CSIC, Avda. M. Luisa s/n, Pabellon del Peru, 51013 Sevilla, Spain. M.R. VlLLARROEL, U. Kuhnlein AND D.M. BiRD. Avian Sci- ence and Conservation Centre of McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9 Canada Raptorial species are predominantly monogamous. Al- though a few species seem to practice alternative mating systems, no paternity analyses have been published so far to confirm polygamy in any bird of prey. Using DNA fingerprinting we examined parentage in 28 nests of lesser kestrels {Falco naumanni) from northern Spain and con- firmed the first case of successful polygyny in the species. In one of the nests, two females and one male were observed several times. DNA fingerprinting revealed that the first of the four nestlings reared at the nest was from the earliest arriving female, while the remaining three were from the second female. The attending male was the father of all four nestlings. Our results indicate variability from strict monogamy in this falcon and emphasize the importance of behavioral observations and genetic markers to study breeding success of raptors. The Fertilization Window of the American Kestrel {Falco sparverius): Characterization AND Consequences VlLLARROEL, M.R., P.W. ThOMAS AND D.M. BiRD Avian Science and Conservation Centre of McGill Univer- sity, Ste. Anne de Bellevue, Quebec H9X 3V9 Canada Raptors are believed to increase their frequency of cop- ulation during the fertilization window, a period between ovulation and eggshell formation when the ovum is fer- tilized. This time interval has not been characterized for any raptor species, although its definition in the repro- ductive process and for sperm competition theory is critical We observed the daily laying patterns of 41 pairs of Amer- ican kestrels in captivity recording time, date and consis- tency of laying as well as the effect of weather patterns and egg pulling. Of 156 ovipositions we observed, 48% were laid in the morning (0730-1130 H). Variation be- tween pairs in starting dates and consistency of egg laying did not correlate significantly to bird age or weather. Egg pulling on 20 focal pairs had no significant effects. Our results indicate a wider fertilization window than previ- ously suggested, which better explains the highly variable daily copulation frequency of this falcon. Growth, Development and Experimental Management of the Madagascar Fish- Eagle {HaLIAEETUS VOCIFEROIDES) Watson, R.T., S. Thomsett and D. O’Daniel. The Peregrine Fund, 5666 West Flying Hawk Lane, Boise, ID 83709 U.S.A. Increasing population size and distribution in suitable un- occupied habitat is one of several management options that would help prevent extinction of the Madagascar fish- eagle, one of the rarest raptors in the world. Breeding studies in 1991 and 1992 showed that this species exhibits obligate siblicide. In 1993 we tested “Abel rescue” as a low-cost in situ method for increasing annual production in Madagascar fish-eagles. Of three nests tested, two fledged two young using an abbreviated captive rearing period in which removed siblings were reintroduced to the nest as soon as they could defend themselves from siblings and compete for food. Measurements of growth, and descrip- tion of behavioral development of chicks in captivity and in the nest for a period close to fledging, provided a method to estimate age of chicks in the nest as well as a better understanding of siblicide in this species. March 1995 Abstracts 69 Poster Presentations Status of Raptors in Argentina BellOCQ, M.I. Faculty of Forestry, University of Toronto, 33 Willcocks St., Toronto, Ontario MSS 3B3 Canada A total of 78 species of raptors occur in Argentina (vul- tures: five species; eagles, hawks, and kites: 40 species; falcons and caracaras; 15 species; owls: 17 species; and the osprey). Habitat deterioration, however, is limiting the distribution of several species, some of which are already restricted to protected areas. Approximately 73% of Ar- gentinean raptors have been classified as scarce, uncom- mon, or hypothetically present in the country. In the Red Data Books of 1990-92, the status of eight raptors were classified as rare, undetermined or insufficiently known in Argentina. Of the 40 raptor species known to inhabit the wet forest of northern Argentina, 25 of them were classified as scarce or uncommon, presumably due to deforestation and hunting of prey. An apparent recovery of raptors in northern Patagonia during the 1980s seems related to de- creasing human persecution. During the 1990s, Argentina has quickly begun to develop an increasing awareness of wildlife conservation through education. A New Model for Dispersal in Screech-Owls: Corticosterone, Body Condition, and Behavior Belthoff, J.R. and A.M. Dufty, Jr. Raptor Research Center and Department of Biology, Boise State University, Boise, ID 83725 US. A. In virtually all birds and mammals, juveniles of one or both sexes leave their natal area before breeding. In screech- owls ifJtus asio and O. kennicottii), both sexes of young disperse, but there is variation in the timing of dispersal within and among broods. We developed a model that explains dispersal in screech-owls and similar nonmigra- tory species where young birds obtain and defend terri- tories following dispersal. The model is based on inter- actions among body condition, hormones, and social stim- uli. We hypothesize that corticosterone secretion increases just prior to dispersal, through a combination of endoge- nous and external events. Rising plasma corticosterone may stimulate increased movement, but the precise effect on dispersal timing depends on the body condition of the bird. Juveniles with sufficient body condition and fat re- serves will disperse when corticosterone rises. Birds in poor body condition or with poor reserves will not, but they will increase foraging activity until they obtain the nec- essary body condition to disperse. We will review results of preliminary field and laboratory studies that examine predictions of the model, and we will discuss future di- rections of the work. A Simple and Effective Burrowing Owl {Speotvto cunicularia) Trap E.S. BotELHO and P.C. ArROWOOD. Department of Bi- ology, New Mexico State University, Las Cruces, NM 88003- 0001 U.S.A. A new trap designed to safely live-trap burrowing owls {Speotyto cunicularia) in the most inaccessible burrows was developed and tested on the campus of New Mexico State University in Las Cruces, New Mexico. The trap consists of a 61 cm piece of 10.16 cm diameter PVC pipe in which two (or one depending on the application) plexiglas one- way doors are installed. A hinged door is installed in the tube in order to remove captured owls safely and easily. The trap is inserted into the burrow and the space between the tunnel and the trap filled with mesh screen. This trap possesses the following advantages over other burrowing owl traps: it is easy to transport from burrow to burrow, it is easy to install even in difficult to reach burrows, and it is completely safe (no owl has ever been injured using this trap). This trap has been used to capture both adults and nestlings in southern New Mexico. Habitat Selection and Reproductive Biology of Loggerhead Shrikes in Eastern Canada Chabot, a., d m. Bird and R.D. Titman. Avian Sci- ence and Conservation Centre of McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9 Canada The status and distribution of endangered loggerhead shrikes (Lanius ludovicianus) in southern Ontario and Que- bec was studied during the 1991 and 1992 breeding sea- sons. Shrikes returned from wintering areas in April and egg-laying commenced from the end of April to early May. The population of loggerhead shrikes in eastern Ontario was roughly 50 pairs over three core areas, each associated with a limestone plain. Only one breeding pair was located in Quebec in 1991 and two in 1992. Shrikes nested in hawthorn {Crataegus spp.), red cedar (Juniperus virgi- niana) and other species, most often in actively grazed pastures. Suitable historic nesting sites were reoccupied and there was a high rate of reoccupancy of 1991 sites in 1992. Breeding territory selection was affected by the amount of habitat fragmentation around a site, but nest site selection appeared to be random within a suitable territory. Shrikes nesting in Ontario had a high rate of reproductive success (50-93%); however, only half of the eggs produced young that survived the 3-4 wk postfledging to become independent (2.30 of 4.91 in 1991 and 2.50 of 5.56 in 1992). Shrikes were found to renest several times and double brooding was observed. Breeding Biology of the Zone-tailed Hawk at the Limit of its Distribution. Crowe, D. Department of Biological Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154 U.S.A. P.L. Kennedy and T. Dean. Department of Fishery and Wild- 70 Abstracts VoL. 29, No. 1 life Biology, Colorado State University, Ft. Collins, CO 80523 U.S.A. Twelve zone-tailed hawk (Buteo albonotatus) nest sites in eight territories were studied in northcentral New Mexico during 1990-92 to determine the nesting chronology, nest- ing habitat, diet and productivity of a population that is at the limit of the species’ distribution. Zone-tailed hawks arrived on the study area from late March to early April and their breeding season ended in mid-late September when the family unit left the nesting territory. All nest stands were in ponderosa pine (Finns ponderosa) forests located in steep canyon bottoms or slopes and frequently in close proximity to cliffs. Stand basal area averaged 23,8 m^/ha and % canopy closure averaged 69.2% (N = 10). Nest trees were large, averaging 23.8 m in height and 59.8 cm dbh (N = 8). The diet consisted of a mixture of mam- malian, avian and reptilian prey species that are common in the study area. During 1990 and 1991 only one of six known territories successfully fledged two and one young, respectively. During 1992 two new territories were located and these were the only successful nests (fledged one and two young). We suggest that the low productivity we ob- served during the 3 yr of the study is representative of the population productivity and is not an anomaly due to small sample sizes. We suggest that this pattern is typical of populations at range margins and occurs because (1) the birds are nesting in marginal habitat, and/or (2) the pop- ulation was founded by a few individuals with philopatric young and is exhibiting inbreeding depression. Communal Roosts: Seasonal Dynamics of a White-tailed Kite Population in the Sacramento Valley, California Erichsen, A.L. Department of Avian Sciences, University of California, Davis, CA 95676 U.S.A. A.M. COMMANDA- TORE. Department of Toxic Substance Control, 400 P Street, Sacramento, CA 95812 U.S.A. D.M. Fry. Department of Avian Sciences, University of California, Davis, CA 95616 U.S.A. We studied 10 communal roosts of white-tailed kites (Elanus leucurus) in a 900 km^ area of the Sacramento Valley, California. The objectives were to examine the annual temporal dynamics of roost use and roosting behaviors and to analyze habitat characteristics of roosts using AtlasTM, a geographic information system. In June 1993 first year birds began arriving at roosts with adult escorts. Roosts were observed 4-7 nights/wk. Three roosts were in sub- urban habitat, four were in deciduous orchards, and three were in natural vegetation. Kites aggregated into two to three large roosts in the fall and winter (N = 30-95) and gradually dispersed into more numerous, less populous roosts (10 with N = 10 at each) in the breeding season. In the winter kites came from <1-50 km away. Telemetry on five kites aided in tracking inter-roost shifts. Kites are very loyal to roosts despite frequent human disturbances. Behaviors associated with roosting changed dramatically with season. Roosts were evenly spaced in winter (2.5 km apart) but in spring became centered near nests. Bird species which roosted with kites include northern harriers (Circus cyaneus), herons and egrets (Ardeidae spp.), and American crows (Corvus brachyrhynchos). Pre-roost stag- ing, soaring, ground perching, and hunting were behaviors associated with fall and winter roosts. Eruptions in which groups of kites (N = 5-50) departed abruptly in the same direction, occurred only in December and January. Based on telemetry and banding data, there are sexual shifts in roost attendance. Communal roosting is postulated to have distinct social contexts for individuals, sexes, and families at different times of the year. A Summary of the First Five Years of Raptor Migration Counts at Dinosaur Ridge, Colorado Hein, F.J. Department of Zoology, Denver Museum of Natural History, Denver, CO 80205 U.S.A. M. Shipman. Department of Biology, Boise State University, Boise, ID 83725 U.S.A. C.R. Preston. Department of Zoology, Den- ver Museum of Natural History, Denver, CO 80205 U.S.A. We have counted migrating raptors at Dinosaur Ridge located 19 km west of downtown Denver, Colorado, each spring since 1990. Dinosaur Ridge is staffed jointly by the Denver Museum of Natural History and The Colorado Bird Observatory and is one of only two spring migration count sites currently operated in the southwestern US. As many as 18 raptor species totaling 5443 individuals have been identified at the site in a single season. The most frequently observed species are the red-tailed hawk (Buteo jamaicensis), and American kestrel (Falco sparverius), but moderate numbers of bald eagles (Haliaeetus leucocephal- us), golden eagles (Aquila chrysaetos) and ferruginous hawks (Buteo regalis) are also recorded. The consistent produc- tivity of Dinosaur Ridge, together with its proximity to a large metropolitan area, provide great opportunities for research, monitoring and environmental education. When Juveniles Look Like Adults — Gray Cooper’s Hawks in the San Francisco Bay Area Jesus, D.F., L.J. Jesus, A.C. Hull and A.M. Fish. Golden Gate Raptor Observatory, Building 201, Ft. Mason, San Francisco, CA 94123 U.S.A. K. Francone. 14 Lang- don Court, Piedmont, CA 94611 U.S.A. In the 1993 breeding season, an unusually pale gray- breasted adult male Cooper’s hawk (Accipiter cooperii) was discovered nesting in an urban park in Alameda County, California. The 1994 nesting was monitored closely as the pale gray male mated with a normally plumaged female. Three of four resulting young had gray backs and breast- March 1995 Abstracts 71 streaking in lieu of the normal brown. Across San Fran- cisco Bay, during fall migration trapping in 1993 in the Marin Headlands, two of approximately 500 immature Cooper’s hawks banded were of the gray aberrant plum- age. Photographs of all of these hawks will be shown. We have found no previous reference to gray Cooper’s hawks in the literature. Red-tailed Hawk and Great Horned Owl; Are They Diurnal/Nocturnal Counterparts? Marti, C.D, Weber State University, Ogden, UT 84408 U.S.A. M.N. Kochert. USDI National Biological Survey, Boise, ID 83705 U.S.A. Red-tailed hawks {Buteo jamaicensis) and great horned owls {Bubo virginianus) have been portrayed as ecological equivalents, eating the same prey by day and night. Similar in size (red-tailed hawk mean mass = 1 126 g, great horned owl mean mass — 1354 g), both raptors are relatively common in North America and occupy a wide range of habitats, often sympatrically. We compared trophic char- acteristics in 13 sets of published data from across the United States to test the ecological similarity of the two species. Mean prey weight of red-tailed hawks was sig- nificantly greater than that of great horned owls. Both species ate primarily birds and mammals and mean pro- portions of the two prey types were not significantly dif- ferent between paired diets of the two raptors. Red-tailed hawks ate significantly more reptiles, and great horned owls ate significantly more invertebrates. At the prey class level, dietary diversity was not significantly different, and diet overlap between the two species averaged 91%. At the species level, dietary overlap averaged only 50%, and red- tailed hawk dietary diversity was significantly greater than that of great horned owls. Populations in the western U.S. differed trophically much more than did eastern popula- tions. We conclude that, although the two species are gen- eralist predators, they take largely different prey species in the same localities resulting in distinctive trophic char- acteristics. The U.S. Fish & Wildlife Service’s Proposal to Reclassify the Bald Eagle in Most of the Lower 48 States Millar, J.G. USDI Fish ir Wildlife Service, 4469-48th Avenue Court, Rock Island, IL 61201 U.S.A. The bald eagle {Haliaeetus leucocephalus) is listed as en- dangered under the Endangered Species Act of 1973 (Act) in the lower 48 states, except Washington, Oregon, Min- nesota, Wisconsin, and Michigan, where it is listed as threatened. The bald eagle also occurs in Alaska and Can- ada, where it is not at risk and is not protected under the Act; and in small numbers in northern Mexico. The Fish and Wildlife Service proposes to reclassify the bald eagle from endangered to threatened in the lower 48 states except the southwestern population in Arizona, New Mexico, the southeast corner of California within 10 miles of the Col- orado River or the river’s mainstem reservoirs, and those portions of T exas and Oklahoma that are west of the 1 00th meridian. The bald eagle would remain threatened in the five states where it is currently listed as threatened and be listed as endangered in Mexico under this proposal. In 1963, a National Audubon Society survey reported only 417 active nests in the lower 48 states with an average of 0.59 young per nest. In 1993, the number of occupied territories exceeded 4000 with an estimated young per nest approaching one. This significant rebound is attributable to the banning of DDT in 1972 and the protection pro- vided by the Endangered Species Act. Significant threats remain but with strong public support, population num- bers should continue to improve. National and regional bald eagle population trends are presented. Preliminary Report on Historical Falco peregrinus Nest Site Distribution in Japan Minton, J. Research Center, Wild Bird Society of Japan, 2-24-5 Higashi, Shibuya-ku, Tokyo 150, Japan The distribution and characteristics of historically active peregrine falcon {Falco peregrinus) nest sites in Japan were compiled from published and unpublished reports, per- sonal contacts and questionnaires distributed to 1 20 raptor enthusiasts in 1993. Around the four main islands of Ja- pan, 191 nest sites were identified, 80 of which were on the northern island, Hokkaido. Excluding Hokkaido, the highest numbers were found on the Japan Sea coast, in Fukui (nine), Niigata (10), and Aomori (13) Prefectures. A high concentration was also identified on the coasts of Iwate and Miyagi Prefectures (possibly 41). Only eight inland and three artificial structure sites were recorded, the remaining were on coastal cliffs or islands. The average height of inland nests sites {N = 5) was 83.5 m (range 18-150 m), and that of coastal and island sites {N = 22) was 43.5 m (range 10-110 m). Conservation of these sites demands their protection from disturbance of nearby con- struction, amateur photographers and fishermen, and ju- venile predation by jungle crows {Corvus macrorhynchos). Selective Capture Methods for Crested Caracaras Morrison, J.L. Department of Wildlife and Range Sci- ences, University of Florida, 118 Nevuins-Ziegler, Gaines- ville, FL 32611 U.S.A. During an ongoing study of the reproductive ecology and habitat use of the crested caracara {Caracara plancus) in southcentral Florida, 10 adults and 16 subadults were captured using two methods. Walk-in cage traps proved successful though not reliable for subadult caracaras. Groups of this age class tend to congregate at a large food 72 Abstracts VoL. 29, No. 1 source and with sufficient pre-baiting of the site and a period during which the trap is left open so they can enter and exit freely, up to five individuals were caught at one time. Vultures, however, pose a great interference problem when attempting to capture caracaras at large baits. Adult caracaras are extremely wary and will not approach any trap, despite camouflage or abundant bait. Typically used noose traps are completely avoided. Experimentation with a taxidermic mount of an adult caracara indicated that these birds are very territorial and do not tolerate intruders near the nest. Subsequently, successful capture of adults was accomplished only in the nesting territory, using a large bow-type net (Q-net) and a tethered live caracara. Success rate with this method was 44% and improved over time as we refined our technique. All juvenile caracaras were marked while still in the nest, between 7 and 8 wk of age, because after fledgling, they quickly seem to learn from their parents to avoid traps. Molt in Tawny Owls in Relation to Breeding Performance and Field Vole Abundance Petty, S.J. Forestry Authority, Wildlife Ecology Branch, Ardentinny, Dunoon, Argyll PA23 STS, Scotland The number of flight feathers molted annually in tawny owls {Strix aluco) was investigated by dyeing feathers of captured owls and reexamining the same birds in the fol- lowing year. Owls were caught during the nestling period before molt started. There was considerable annual vari- ation in the number of primary and secondary feathers molted related to breeding success, which in turn was related to a 3-yr cycle of abundance of field voles (Microtus agrestis), the owls’ main food. Owls molted most wing feathers in years of low vole abundance when most pairs did not breed, and fewest in years with high vole numbers when most pairs bred. Tail feather molt was not related to breeding success or to any other factor investigated, with most birds replacing all tail feathers biennially. Reasons for the evolution of this complex molt are discussed. An almost identical molt sequence occurs in the larger Ural owl (Strix uralensis) in Finland, and it would be valuable to undertake similar studies on wild barred (Strix varia) and spotted owls (Strix occidentalis) in North America. Relationship of Water Level to Bald Eagle Reproduction at Shasta Reservoir, California Santolo, G.M. CH2M HILL, Inc., 2485 Natomas Park Drive, Suite 600, Sacramento, CA 95833 U.S.A. P.J. De- TRICH. USDI Fish and Wildlife Service, 2800 Cottage Way, Sacramento, CA 95825 U.S.A. Stable bald eagle (Haliaeetus leucocephalus) populations produce 0.7-1. 2 young per occupied site and the Pacific Bald Eagle Recovery Plan states that the goal for repro- ductive rates for recovery is one eagle chick for each oc- cupied nest site or 50% of the maximum reproductive potential for eagles. Data on the number of occupied bald eagle nests and the number of young produced from these nests has been collected at Shasta Reservoir since 1977. Relationships between water levels at Shasta Reservoir and the number of young eagles produced at each site were determined through regression analyses; these relation- ships are based on the measured water levels at the res- ervoirs (USGS, 1979 through 1991), and data on bald eagle reproduction. At Shasta Reservoir, analyses indi- cated a general increase in eagle reproduction as water level increased. A variety of factors probably contribute to reduced reproductive success in bald eagles. Many of these factors may depend either directly or indirectly on lake water level. Water level affects such factors as surface area of the lake, fish availability, and competition for eagle nesting and foraging areas. About 50% of the variability in bald eagle reproductive success was accounted for by a linear correlation with the average (April through Sep- tember) Shasta Lake water elevation. This percentage of explainable variability suggests a strong relationship be- tween lake water level and eagle reproductive success. The model created predicts that average lake elevations over 311 meters meet the USFWS recovery goal of one bald eagle chick per occupied nest and average levels below 308 m predicts eagle reproduction below the recovery goal. Environmental Components of Differences in Osprey Growth SCHAADT, C.P. Wildlife Technology, School of Forest Re- sources, The Pennsylvania State University, DuBois Cam- pus, DuBois, PA 15801 U.S.A. There is significant geographic variation in growth rate and asymptotic size between osprey (Pandion haliaetus) nesting in arid Sonora, Mexico and temperate Nova Scotia, Canada. This poster presents gradients in environmental variables including, at least, (a) migratory versus sedentary habits, (b) synchronous versus asynchronous breeding, (c) time-limited breeding seasons, and (d) climatic factors as important possible causes to account for the growth and size differences observed between the two populations. Migration Routes and Winter Ranges of Golden Eagles ScHUECK, L.S., J-M. Marzluff and M. Vekasy. Greenfalk Consultants, 8210 Gantz Ave., Boise, ID 83709 U.S.A. M.R. Fuller and T.J. Zarriello. National Biological Survey, Raptor Research and Technical Assis- tance Center, Boise, ID 83705 U.S.A. W.S. Seegar. De- partment of Army, Aberdeen Proving Ground, Aberdeen, MD 21010 U.S.A. Effective conservation of avian breeding populations can involve a very large area (breeding grounds, wintering grounds, and migration routes). Golden eagles (Aquila chrysaetos) that nest in Alaska are difficult to follow on March 1995 Abstracts 73 wintering grounds in southwestern Idaho, because their ranges can be large and include mountainous terrain and roadless areas. We used radiotelemetry to locate and de- scribe golden eagle wintering areas. We radio-tagged 11 golden eagles on their wintering grounds in southwestern Idaho with conventional and satellite received transmitters during 1993-94. Movements were monitored one to two times per week visually and daily by satellite. Adult golden eagles showed fidelity to wintering areas, but did not de- fend them from other eagles. Adults were more consistently tracked by conventional telemetry than were subadults. Wintering areas of subadult eagles were larger than those of adults. Wintering ranges derived from satellite locations were larger than those derived from visual locations. Non- resident adults spent the breeding season in Alaska and western Canada while subadults stayed in the northwest- ern United States. Travel times for migration of adults to presumed breeding grounds varied from 6-27 da. Band Recoveries of Diurnal Raptors Banded in the Marin Headlands, Marin County, California Scheuermann, K.L. and M.A. Weeks. Golden Gate Raptor Observatory, Building 201 , Fort Mason, San Fran- cisco, CA 94123 U.S.A. J.A. Howell. USDI National Biological Survey, Golden Gate Field Station, Fort Mason, Building 201, San Francisco, CA 94123 U.S.A. Since 1 983, 1 5 species of diurnal raptors have been banded in the Marin Headlands, Marin County, California. These birds are trapped at blinds in the Headlands from August through December by volunteers of the Golden Gate Rap- tor Observatory. To date, we have banded 6523 diurnal raptors, and have had 1 62 band recoveries of eight species. We have had 141 band recoveries from California, with the remainder from Oregon, Washington, Idaho, and Baja California and Sonora, Mexico. Of the 15 species, we have banded red-tailed hawks (Buteo jamaicensis), Cooper’s hawks (Accipiter cooperii), and sharp-shinned hawks {A. stnatus) in the greatest numbers. For 2631 red-tailed hawks banded, 83 band recoveries have been reported, with a 3.2% recovery rate. We have mapped the band recoveries by age of bird and by season of recovery to make seasonal comparisons of the data. For example, autumn band re- coveries for juvenile red-tailed hawks extend 1 90 km in- land from the Pacific Coast, and occur from central to northern California. Autumn band recoveries for adult red-tailed hawks are found in a larger area, extending 350 km inland, and extending from southern California to central Washington. Winter band recoveries for juvenile and adult red-tailed hawks occur predominately within 80 km of the Pacific Coast, representing a smaller area than autumn recoveries. These results suggest that there are some differences in geographic areas used in autumn and winter by the juvenile and adult red- tailed hawks. Smaller band recovery sample sizes for Cooper’s and sharp-shinned hawks allow for a more limited set of comparisons. Of interest are several autumn and winter band recoveries in Baja California for juvenile Cooper’s and sharp-shinned hawks. Wintering Habitat and Feeding Behavior of White-tailed Sea-Eagles and Steller’s Sea-Eagles in Hokkaido, Japan Shiraki, S. Graduate School of Environmental Earth Sci- ence, Hokkaido University, Sapporo 060, JAPAN Hokkaido, Japan is a part of the wintering region of white- tailed sea-eagles (Haliaeetus albicilla) and Steller’s sea- eagles (Haliaeetus pelagicus). However their wintering ecology in Hokkaido was little known. I studied the habitat and food resource use of eagles in winter seasons. First, I counted the number of eagles at the 71 fixed sites near water or garbage sites in the northern and eastern parts of Hokkaido as a preliminary study. These censuses were carried out six times at each site during November 1991 to April 1992. These sites were divided into five habitat types such as sea, lake, basin, estuary, and garbage dump. Habitats where eagles congregated shifted according to the census time. Eagles changed wintering areas flexibly cor- responding to environmental conditions and fishery activ- ities. Additionally, it seems that the selection of wintering habitat differed with species and age. Next, I observed the feeding behavior of eagles in three different habitats (river, lake, and garbage dump) from November 1993 to March 1994. The relationships among the food items, inter- and intra- specific interactions, and the feeding strategies will be discussed. This study was funded by WWF Japan. Investigation of Arizona Peregrine Falcon Eggshell Thickness Siemens, M.C. Arizona Game and Fish Department, Nongame Branch, 2221 West Greenway Road, Phoenix, AZ 85023 U.S.A. L.Z. Ward. Arizona Game and Fish De- partment, Nongame Branch, 2221 West Greenway Road, Phoenix, AZ 85123 U.S.A. In 1993, the Arizona Game and Fish Department initiated a study to collect and measure peregrine falcon (Falco peregrinus) eggshells from the Arizona breeding popula- tion. This sample mean will be compared with a sample mean for eggshells collected in Arizona more than 10 yr ago and a pre-DDT sample mean for eggshells collected in California. We present our 1993 and 1994 collection results. Vocalization Behavior of Loggerhead Shrikes (LaNIUS LUDOVICIANUS) IN CAPTIVITY SoENDjOTO, M.A., D.M. Bird and R.E. Lemon. Avian Science and Conservation Centre of McGill University, 74 Abstracts VoL. 29, No. 1 Macdonald Campus, 21,111 Lakeshore Road, Ste. Anne de Bellevue, PQ, H9X 3V9 Canada Loggerhead shrikes are classified as predatory songbirds. Yet song patterns of this species are poorly understood. F rom April until August 1 994 we studied the vocalization behavior of captive-bred shrikes at McGill University and found sex-related song characteristics. During the breed- ing season several types of auditory displays and/or visual displays related to breeding behavior were also analyzed, including nest-site selection, food offering, food begging, courtship (pre-, during-, and post-copulation), feeding, and aggressive calls. First Capture of a Live Madagascar Serpent- Eagle (Eutriorchis astur) and Photographs of a Live Madagascar Red Owl {Tyto soumagnei) Confirm the Survival of These Species Thorstrom, R. and R.T. Watson. The Peregrine Fund, 5666 West Flying Hawk Lane, Boise, ID 83709 U.S.A. Until recently, the Madagascar serpent-eagle, considered among the rarest raptors in the world, was known only from 1 1 museum specimens, the last of which was collected in 1930. A reported sighting in 1989 and a dead bird found in 1990 were the only evidence that the species remained extant. Repeated sightings and the capture of Eutriorchis astur by Peregrine Fund biologists in 1993 and 1994 have provided the first opportunity to study the biology and behavior of this species in the wild. A single sighting and photograph of a Madagascar red owl taken in February 1994 provides only the third account of this species since 1934, when the last museum specimen was collected. Pre- vious sightings were made in 1974 and a bird was found in captivity in 1993 but died soon after discovery. Sightings described in this paper occurred on Masoala Peninsula, northeastern Madagascar. Survey of Savanna Grassland Habitat for Aplomado Falcons and Other Raptors Ward, L.W., M.C. Siemens, R.L. Glinski and M.I. Ingraldi. Arizona Game and Fish Department, Nongame Branch, 2221 West Greenway Road, Phoenix, AZ 85027 U.S.A. Wild aplomado falcons (Falco femoralis) have been ob- served in New Mexico and Texas in recent years. In 1994, the Arizona Game and Fish Department initiated surveys for this species and other raptors in southeastern Arizona grassland habitat. Ten survey routes were established. We will present the protocol and preliminary survey results including data on raptor occurrence, distribution and den- sity. J Raptor Res. 29(1):75 © 1995 The Raptor Research Foundation, Inc. Manuscript Referees The following people reviewed manuscripts for the Journal of Raptor Research in 1994. Peer review plays a vital role in the publishing process and in improving the quality of the Journal. The names of individuals who reviewed two or more papers are followed with an asterisk. Dean Amadon, David J. Anderson, Robert Anthony, Marc J. Bechard, Dale Becker, James C. Bednarz,* James R. Belthoff, Louis B. Best, Keith I. Bildstein, David M. Bird, Peter H. Bloom,* Clint B. Boal, Carl E. Bock, Eric G. Bolen, Gary R. Bortolotti,* Eugene S. Botelho, Nancy Braun, Enrique H. Bucher, Evelyn Bull, Javier Bustamante, Susan Chaplin, Felipe Chavez-Ramirez, Carl D. Cheney, Richard J. Clark, Dale H. Clayton, Erica H. Craig, Timothy H. Craig, Will Cresswell, Cole Crocker- Bedford, David Crompton, James W. Dawson, Steven DeStefano,* Juan A. Donazar,* Katharine E. Duffy, Wade L. Eakle, David H. Ellis,* James H. Enderson, David Evans,* Allen Fish, Paolo Galeotti, Laurie Goodrich, Joseph A. Gubanyi, Patricia A. Hall, Richard W. Hansen, Alan H. Harmata,* Fred H. Harrington, Gregory D. Hayward, Judy Henckel, Charles J. Henny,* Mauro Hernandez, Fernando Hiraldo, Denver Holt, C. Stuart Houston, Richard Howard, Frank B. Isaacs, Ronald Jackman, Fabian M. Jaksic,* Paul C. James, M. Alan Jenkins, Jaime E. Jimenez,* Patricia L. Kennedy,* Paul Kerlinger, David A. Kirk,* John S. Kirkley, Michael N. Kochert, Erkki Korpimaki,* Robert Lehman, Steven L. Lima, Jeffrey Lincer, Jeffrey S. Marks,* L. David Mech, Brian A. Millsap,* Douglas Mock, Anders P. Moller, Janice Moore, James A. Mosher, Helmut C. Mueller,* R. Wayne Nelson, Ian Newton, Susan M. Patla, Colin Pennycuick, Steve Petty, Hannu Pietiainen, Alan F. Poole, Howard Postovit, Leon Powers, Charles R. Preston, Roger Price, Mary H. Pritchard,* Steven G. Pruett- Jones, Robert N. Rosenfield, Ronald A. Ryder, Beth A. Sabo, Elise Vernon Schmidt, Josef K. Schmutz,* Norman Seymour, Robert E. Simmons, John Squires, Dale Stahlecker,* Mark V. Stalmaster, Thomas J. Stohlgren, Ted Swem,* Glen D. Therres, Jean Marc Thiollay, Kimberly Titus, Charles Trost, Helen Ulmschneider, Thomas Van Devender, Andrew Village, Ian G. Warkentin, Clayton M. White, Stanley N. Wiemeyer, James W. Wiley, Neil D. Woffinden,* Petra Bohall Wood. 75 J. Raptor Res. 29(1):76 © 1995 The Raptor Research Foundation, Inc. Thesis Abstract Raptor Use of the Idaho National Engineering Laboratory Raptors are high-trophic-level predators, and thus sensitive to environmental change. I conducted a basic ecological study of raptors using the Idaho National Environmental Laboratory (INEL), in southeastern Idaho, between 1991 and 1993 to assess effects of human activity on the site. Results were compared to previous raptor studies conducted on the INEL from 1974-76 and in 1982, as well as with studies of rough-legged hawks {Buteo lagopus), long-eared owls (Asia otus), and burrowing owls (Speotyto cunicularia) conducted during the late 1970s and early 1980s. Roadside raptor surveys were conducted from January through May in 1992 and 1993. Principal species recorded were rough-legged hawks, red-tailed hawks {Buteo jamaicen sis) , ferruginous hawks {Buteo regalis), golden eagles {Aquila chrysaetos), prairie falcons {Falco mexicanus), and great horned owls {Bubo virginianus). Most raptors were perched on power poles when I observed them. Site facilities did not appear to affect wintering raptor distribution. A high occurrence of raptors within 10 km of site facilities was probably a result of power pole distribution, because power poles were usually close to facilities. Raptor populations were comparable to those noted during the 1970s, but lower than raptor numbers in 1982. I conducted short-eared owl {Asia flammeus) counts during the spring 1992 and 1993. Counts were accomplished by walking 5 transects (2 km long). No owls were flushed; however, owls were observed during other phases of this study. Ten kilometers of transect is probably insufficient to monitor short-eared owl populations on the INEL. To establish species occurrence and distribution of owls on the INEL, I conducted nocturnal calling surveys. At regular stops along five routes, I played owl calls and recorded all responses. Eight species were recorded during these surveys: great horned owl, long-eared owl, short-eared, burrowing owl, boreal owl {Aegolius funereus), northern saw- whet owl {Aegolius acadicus), western screech-owl {Otus kennicottii, and flammulated owl {Otus flammeolus). Most owls were detected in April and May in the juniper forests around the Lemhi foothills and Twin Buttes. I monitored raptor nesting from March through August, concentrating on medium- to large-sized species. Long- eared owls and great horned owls nested in limited numbers during this study. Owl nesting success was comparable to other studies in the Great Basin. Red-tailed hawks, ferruginous hawks, and Swainson’s hawks {Buteo swainsoni) were common nesters on the INEL. Red-tailed hawk numbers have increased since the 1970s, while Swainson’s and ferruginous hawk numbers have remained relatively stable. Reproductive success was comparable to earlier studies. Nest distribution of ferruginous and Swainson’s hawks was fairly random, with some avoidance of human development in the case of ferruginous hawks. Ferruginous hawks, a category 2 species under consideration for threatened and endangered species status, experienced higher nest failure when exposed to increased human activity on site. Red- tailed hawk nests were clustered along the Big Lost River. Food habits comparisons showed dietary overlap between Swainson’s hawks, red-tailed hawks, and great horned owls. Ferruginous hawks and long-eared owls had little overlap with other species. Continued monitoring of raptors on the INEL through prey fluctuations would provide insight into relationships between raptors, as well as with their prey base and habitats. — Richard W. Hansen. 1994. Department of Wildlife and Fisheries Sciences, South Dakota State University, Brookings, SD 57007-1696 U.S.A. 76 J Raptor Res. 29(1 ):77 © 1995 The Raptor Research Foundation, Inc. Dissertation Abstract History, Nesting Biology, and Predation Ecology of Raptors in the Missouri Coteau of Northwestern North Dakota The species composition of raptors (Falconiformes and Strigiformes) that nest in North America’s northern Great Plains is being altered due to land use, but detailed case histories of such change are lacking, few long-term data exist to help understand raptor population dynamics in prairie areas, and implications of changes for other prairie wildlife on which raptors prey are poorly understood. I studied mechanisms and implications of land use impacts on raptors in the Missouri Coteau physiographic region of northwestern North Dakota by (1) tracing change during the past century in raptor species composition and habitat on the 108-km^ Lostwood National Wildlife Refuge (LNWR), (2) assessing current (1981-90) population stability, annual reproductive success, and habitat relationships of raptors on LNWR and comparative species nesting biology on an adjacent area of different land use, and (3) determining prey needs of common, large (>700 g) raptor species on LNWR and use of prey by raptors in relation to habitat on an area of contemporary, mixed land use. Northern harriers {Circus cyaneus), Swainson’s hawks {Buteo swainsoni), ferruginous hawks {Buteo regalis), and burrowing owls {Speotyto cunicularia) comprised the nesting raptors on LNWR before settlement in the early 1900s, great horned owls {Bubo virginianus) were rare but gradually increased over the last 40-50 yr, red-tailed hawks {B. jamaicensis) pioneered about 30 yr ago, and Cooper’s hawks {Accipiter cooperii) pioneered in the past decade. Today, red-tailed hawks and great horned owls have replaced Swainson’s and ferruginous hawks as dominant large raptors, coinciding with succession from mixed grass prairie to aspen parkland with brush- dominated uplands. Harrier abundance apparently has changed little, but nesting burrowing owls have been absent more than 40 yr. The most fundamental causes of change in the raptor community probably were altered susceptibility of prey to foraging behaviors of specific raptor species and decreased abundance of certain key prey species. During the 1980s red-tailed hawks and great horned owls exhibited high, stable nesting densities {x = 0.23 and 0.13 occupied nests/km^, respectively) but erratic and low annual productivity {x — 0.9 and 0.7 young/occupied nest); both species nested mostly in areas with highest densities of tree clumps and the owl was associated with wetlands. Nearly all Swainson’s hawk nests occurred on LNWR’s boundary, and an adjacent area (93 km^) of different land use had twice as many occupied Swainson’s hawk nests/km^ as LNWR. Great horned owl diets were studied during late spring and Swainson’s hawk diets during summer, 1986-87, on land of mixed use; 2900 and 1284 prey items were recorded, respectively. The owl relied heavily on avian prey from wetlands (total wetland prey: 57% of overall frequency and 76% biomass of diet) especially ducks and used less leporid prey than reported elsewhere. Swainson’s hawks also used many prey from wetlands (49% overall frequency, 427o biomass) but mammals were the most important prey and overall diet was more diverse compared to findings elsewhere. Variation in use of several categories of prey among Swainson’s hawk families was explained mostly by nesting area habitat. A cursory survey of great horned owl and red-tailed hawk diets on LNWR suggested these raptors relied on prey from wetlands, especially ducks. Fire suppression and other land-use practices that increase woody vegetation across prairies of the northern Great Plains can expand nesting opportunities for red-tailed hawks and great horned owls. Most species of breeding raptors that historically were common in northern prairies, as well as many other species of migratory birds indigenous to the region, may be inimically affected by such changes due to decreased habitat quality or interspecific interaction (e.g., resource competition and predation) with red-tailed hawks and great horned owls. — Robert K. Murphy. 1993. Ph.D. dissertation, Department of Biology, Montana State University, Bozeman, MT 59717 U.S.A. Present address: U.S. Fish and Wildlife Service, Des Lacs National Wildlife Refuge Complex, Box 578, Kenmare, ND 58746 U.S.A. 77 J. Raptor Res. 29(1 ):78 © 1995 The Raptor Research Foundation, Inc. Dissertation Abstract Offspring Sex Ratio, Mortality and Relative Provisioning of Daughters and Sons in the Northern Harrier {Circus cyaneus) Sex ratio theory has two main paradigms. The first, proposed by R.A. Fisher (1930, The genetical theory of natural selection, Clarendon Press, Oxford, U.K.), posits that natural selection will favor parents that invest equally in the sexes, such that the population sex ratio at the end of the period of parental care should be the inverse of the costs of producing individuals of each sex. The second paradigm supposes that whenever the genetic fitness benefits of producing daughters or sons vary predictably with ecological circumstances individual parents are expected to manipulate the sex ratio of their offspring so as to maximize the number of grandoffspring produced. Offspring sex ratios were documented over 10 yr (1980-85, 1990-93) for a New Brunswick, Canada, population of the northern harrier {Circus cyaneus), a strongly size-dimorphic hawk. In contrast to a population in Orkney, Scotland, in which the sex ratio at fledging was female-biased (N. Picozzi 1984, Ibis 126: 356-365), sex ratios at hatching and at fledging did not deviate from parity in New Brunswick. However, in Scotland, the sex ratio at fledging became progressively less female-biased and eventually male-biased over a 30-yr period. In Orkney, but not in New Brunswick, there existed a shortage of males in the breeding population. Despite the larger size of females, daughters and sons were provisioned similar amounts of food during the period of parental care. This implies that the sexes similarly affect parent residual reproductive value, i.e., the expected contribution to the population through future offspring. These observations are consistent with the expectation of Fisher’s principle of the evolution of population sex ratios, viz., parents should invest equally in daughters and sons, unless the reproductive values, or average expected fitnesses, of the sexes differ, in which case natural selection will favor parents that produce more of the rarer sex. A seasonal decline in sex proportion of males was evident among fledglings, but not hatchlings, implying a differential increase in mortality among male offspring as the breeding season progressed. Increased mortality among males relative to females was primarily due to an overall seasonal increase in nestling mortality, rather than to sex-specific differences in susceptibility to mortality. I found little evidence of facultative parental manipulation of offspring sex ratios depending on ecological circumstances at the time of breeding. Sex ratios varied nonrandomly according to the egg-sequence within clutches. Overall, eggs laid first in the clutch were biased toward females, and second and third eggs laid were biased toward males; however, the proportion of females among eggs laid early increased with increasing clutch size. Regardless of clutch size, neither sex predominated in the last egg laid. I could not confirm that the nonrandom allocation of the sexes within clutches is adaptive; however, growth in females was more strongly negatively associated with correlates of reduced food consumption and increased mortality, including high precipitation, late birth date, and late positions within the laying sequence than was growth in males. Females began flying at an older age and developed flight skills more slowly than males. Furthermore, the ability of fledglings to secure food from parents was strongly influenced by the sequence in which siblings began flying. Thus, a skewing of the sex ratio of first-hatched offspring toward females may enhance the growth, competitive ability, and survival, and hence, fitness of daughters. Eggs hatched asynchronously; consequently, starvation increased with position in the laying sequence. Yet, the proportion of nestlings that died within broods did not increase with brood-size. I propose that the shift toward an even sex ratio among late-hatched eggs is an adaptive mechanism that limits the degree of sex-biased mortality and forestalls the development of a maladaptive sex ratio at the end of the period of parental care. — R. Bruce MacWhirter. 1994. Ph.D. dissertation, Department of Zoology, The Ohio State University, Columbus OH, 43210 U.S.A. Present address: Department of Natural Resource Sciences, McGill University, 21 111 Lakeshore Road, Ste. Anne de Bellevue, Q,C H9X 3V9 Canada. 78 /. Raptor Res. 29(l):79-83 © 1995 The Raptor Research Foundation, Inc. Index to Volume 28 BY Elise Vernon Schmidt The index includes references to genera, species, common names, key words, and authors. Reference is also made to book reviews, dissertation abstracts, meeting abstracts, letters, and reviewers. Taxa other than raptors are included where referenced by the authors. A Abstracts of the 1993 Annual Meeting, 45-71 Abundance, 220-225 Acanthocephala, 34-38 Accipiter cooperi, 1-3 gentilis, 84-92 striatus, 1-3 Anderson, David I.K., see Petty, Steve J. Antipredator, 93-99 Aquila chrysaetos, 268-273 Asia otus, 253-258, 265-268 Azkona, Paz, see Fernanadez, Carmelo B Baja California, 110-112 Banding, 213-219 Barbieri, Francesco, see Bogliani, Giuseppe Bednarz, James C., see Steenhof, Karen Behavior, 100-107 Behavioral ecology, 100-107 Bennett, Gordon F., see Forrester, Donald J. Bibles, Erin L., see Boal, Clint W. Bird, David M., see Morneau, Francois Bird, David M., see Brodeur, Serge Bird selection, 246-252 Blanco, Guillermo, Seasonal abundance of black kites as- sociated with the rubbish dump of Madrid, Spain, 242- 245 Boal, Clint W., Erin L. Bibles and Raymond E. Brown, Unusual parental behaviors by male northern gos- hawks, 120-121 Bogliani, Giuseppe, Francesco Barbieri and Eugenio Tiso, Nest-site selection by the hobby (Falco subbuteo) in poplar plantations in northern Italy, 13-18 Bone digestion, 73-78 Book reviews, 199-203, 276-280 Bortolotti, Gary R., Effect of nest-box size on nest-site preference and reproduction in American kestrels, 1 27- 133 Botelho, Eugene S., A review of The Mississippi Kite: Por- trait of a Southern Hawk, by Eric G. Bolen and Dan Flores, 199-200 Bow net, 268-273 Bowerman, William Wesley IV, Regulation of bald eagle (Haliaeetus leucocephalus) productivity in the Great Lakes Basin: An ecological and toxicological approach (Dissertation abstract), 123 Breeding, 39-42 ecology, 149-153 success, 13-18, 154-157 Brodeur, Serge, Francois Morneau, Robert Decarie, Juan J. Negro and David M. Bird, Breeding density and brood size of rough-legged hawks in northwestern Quebec, 259-262 Brodeur, Serge, see Morneau, Francois Brown, Raymond E., see Boal, Glint W. Bubo virginianus, 164-170 Bustamante, Javier, Behavior of colonial common kestrels {Falco tinnunculus) during the post-fledging depen- dence period in southwestern Spain, 79-83 Bustamante, Javier and Juan Jose Negro, The post-fledg- ing dependence period of the lesser kestrel {Falco nau- manni) in southwestern Spain, 158-163 Buteo buteo, 100-107 lagopus, 259-262 C Canadian Arctic, 4-8 Canova, Luca, see Galeotti, Paolo Captivity, 100-107 Capture techniques, 268-273 Carpenter, George P., see Steenhof, Karen Garriere, Suzanne, see Morneau, Francois Castellanos, Aradit, Federico Salinas-Zavala and Alfredo Ortega-Rubio, Status and reproduction of the pere- grine falcon at a coastal lagoon in Baja California Sur, Mexico, 100-112 Chaplin, Susan B,, see Knuth, Shannon T. Chaviez-Ramirez, Felipe and Felipe G. Prieto, Effects of prescribed fires on habitat use by wintering raptors on a Texas barrier island grassland, 262-265 Circaetus gallicus, 39-42 Circus aeruginosas, 23-26 cyaneus, 262-265 pygargus, 19-22 Clark, William S., see Farquhar, C. Craig Clark, William S., A review of The Black Eagle: A Study, by Valerie Gargett, 277-278 79 80 Index to Volume 28 VoL. 29, No. 1 Clark, William S., A review of Birds of Prey^ by Floyd Scholz, 278-279 Clutch size, 1-3 Coello, Monica, see Farquhar, C. Craig Color-marking, 213-219 Colorado, 43-44 Copsey, Jamieson A., see Houston, David C. Corona, Carlo Vittorio, see Csermely, Davide Cousineau, Elmer, see Ewins, Peter J. Creatine kinase, 27-33 Crompton, D.W.T., see Mclnnes, F.J. Csermely, Davide and Carlo Vittorio Corona, Behavior and activity of rehabilitated buzzards {Buteo buteo) re- leased in northern Italy, 100-107 D Decarie, Robert, see Morneau, Francois Decarie, Robert, see Brodeur, Serge Diet, 246-252, 265-268 composition, 253-258 Dispersal, 100-107, 158-163 Dissertation abstracts, 123-124 Doody, J. Sean, Winter roost-site use by female American kestrels (Falco sparverius) in Louisiana, 9-12 Driscoll, Daniel E., see Jackman, Ronald E. £ Eagle, bald, 113-114, 205-212, 213-219, 268-273 golden, 220-225, 236-241, 268-273 short-toed, 39-42 Eakle, Wade L., A raptor roadside survey in western Turkey and eastern Greece, 186-191 Ectoparasites, 232-235 England, 149-153 Ewald, J.A., see Mclnnes, F.J. Ewins, Peter J. and Elmer Cousineau, Ospreys {Pandion haliaetus) scavenging fish on ice, 120 Exercise, 27-33 Experimental validity, 143-148 F Falco peregrinus, 110-112 naumanni, 158-163 rusticolus, 4-8 sparverius, 9-12, 194-196, 262-265 subbuteo, 13-18 tinnunculus, 79-83 Falcon, peregrine, 110-112 Falconiformes, 226-231 Farm habitat, 164-170 Farmer, Chris A., see Stohlgren, Thomas J. Farquhar, C. Craig, William S. Clark, Robert G. Wright and Monica Coello, First record of interspecific cart- wheeling between large raptors: Buteo poecilochrous and Geranoaetus melanoleucus, 274-275 Fernandez, Carmelo and Paz Azkona, Sexual differences in conspecific territorial defense of marsh harriers {Cir- cus aeruginosus) , 23-26 Ferns, Peter N. and Shelley A. Hinsley, Effects of raptors on the activity of sandgrouse, 236-241 Fire, 262-265 Fledging, 79-83, 158-163 Florida, 226-231 Food habits, 39-42, 84-92, 265-268 technique, 192-193 Forest age structure, 205-212 demography, 205-212 habitat, 164-170 Forrester, Donald J., Sam R. Telford, Jr., Garry W. Foster and Gordon F. Bennett, Blood parasites of rap- tors in Florida, 226-231 Foster, Garry W., see Forrester, Donald J. Franklin, Alan B., see Hunter, John E. Franson, J. Christian, Parathion poisoning of Mississippi kites in Oklahoma, 108-109 G Galeotti, Paolo and Luca Canova, Winter diet of long- eared owls {Asia otus) in the Po Plain (northern Italy), 265-268 Gehlbach, Frederick R., Coordinator, A symposium on using nest boxes to study raptors: do the boxes provide virtual reality? 125-126 Gehlback, Frederick R., Nest-box versus natural-cavity nests of the eastern screech-owl: an exploratory study, 154-157 Goodrich, Laurie, see Powers, Lauren V. Goshawk, 84-92 Great Britain, 34-38 Greece, 39-42, 186-191 Gutierrez, R.J., see Hunter, John E. Gypaetus barbatus, 73-78 Gyrfalcon, 4-8 H Habitat, 259-262 bald eagle, 205-212 characteristics, 164-170 selection, 13-18 use, 262-265 Hacking, 19-22 Haliaeetus leucocephalus, 205-212, 213-219, 268-273 Harrier, marsh, 23-26 Montagu’s, 236-241 northern, 262-265 Hawks, 100-107 Hawk, Cooper’s, 1-3 red-tailed, 27-33 rough-legged, 259-262 sharp-shinned, 1-3, 178-185 Hematology, 178-185 March 1995 Index to Volume 28 81 Hemoparasites, 178-185, 226-231 Hinsley, Shelley A., see Ferns, Peter N. Hobby, 13-18 Houston, David C. and Jamieson A. Copsey, Bone di- gestion and intestinal morphology of the bearded vul- ture, 73-78 Hudson Bay, 220-225, 259-262 Human-altered habitats, 149-153 Hunt, W. Grainger, see Jackman, Ronald E. Hunter, John E., R.J. Gutierrez, Alan B. Franklin and David Olson, Ectoparasites of the spotted owl, 232- 235 I Icosta americana, 232-235 Ictinia mississippiensis , 108-109 Idaho, 194-196 In memoriam: Richard R. Olendorf, 1943-1994, 204 Intestinal morphology, 73-78 Italy, 13-18, 265-268 J Jackman, Ronald E., W. Grainger Hunt, Daniel E. Dris- coll and Frank J. Lapansky, Refinements to selective trapping techniques: a radio-controlled bow net and power snare for bald and golden eagles, 268-273 Jenkins, Andrew R. and Anthony J. van Zyl, Flush-hunt- ing and nest robbing by peregrine falcons, 118-119 Jenkins, M. Alan, see Mulhern, Daniel W. Johnson, Paul N., Selection and use of nest sites by barn owl in Norfold, England, 149-153 Juvenile independence, 171-177 K Kansas, 113-114 Kestrel, American, 9-12, 127-133, 194-196, 262-265 common, 79-83 lesser, 158-163 Kite, black 171-177, 242-245 Mississippi, 108-109 Knittle, C. Edward and Mark A. Pavelka, Hook and loop tabs for attaching a dho-gaza, 197-198 Knuth, Shannon T. and Susan B. Chaplin, The effect of exercise on plasma activities of lactate dehydrogenase and creatine kinase in red-tailed hawks {Buteo jamai- censis), 27-33 Koga, Kimiya and Satoshi Shiraishi, Parent-offspring re- lations during the post- fledging dependency period in the black kite (Milvus migrans) in Japan, 171-177 Kritz, Kevin J., see Wiggers, Ernie P. Kurodaia magna, 232-235 L Lactate dehydrogenase, Tl-'h'h Lapansky, Frank J., see Jackman, Ronald E. Laybourne, Roxie C., see Sabo, Beth Ann Lehman, Robert, In memoriam, Richard R. Olendorff, 1943-1994, 204 Letters, 118-122, 197-198, 274-275 Linkhart, Brian D. and Richard T. Reynolds, Peromyscus carcass in the nest of a flammulated owl, 43-44 Louisiana, 9-12 Lures, 115-117 M Mabie, David W., M. Todd Merendino and David H. Reid, Dispersal of bald eagles fledged in Texas, 213- 219 MacDonald, J., Bald eagle attacks adult osprey, 122 Madrid, 242-245 Manosa, Santi, Goshawk diet in a mediterranean area of northeastern Spain, 84-92 Marks, Jeff, A review of Barn Owls: Predator- Prey Rela- tionships and Conservation, by Iain Taylor, 201-203 Marks, Jeff, A review of Raptor Conservation Today, edited by B.-U. Meyburg and R.D. Chancellor, 279 Mclnnes, F.J., D.W.T. Crompton and J.A. Ewald, The distribution of Centrorhynchus aluconis (Acanthoce- phala) and Porrocaecum spirale (Nematoda) in tawny owls {Strix aluco) from Great Britain, 34-38 Mediterranean, 84-92 Merendino, M. Todd, see Mabie, David W. Mexico, 110-112 Migration, 178-185, 213-219 Milvus migrans, 171-177, 242-245 Missouri, 1-3 Mist nets, 194-196 Moller, Anders Pape, Facts and artefacts in nest-box stud- ies: implications for studies of birds of prey, 143-148 Morneau, Francois, Serge Brodeur, Robert Decarie, Suz- anne Carriere and David M. Bird, Abundance and distribution of nesting golden eagles in Hudson Bay, Quebec, 220-225 Morneau, Francois, see Brodeur, Serge Morrell, Thomas E. and Richard H. Yahner, Habitat characteristics of great horned owls in southcentral Pennsylvania, 164-170 Mulhern, Daniel W., Michael A. Watkins, M. Alan Jen- kins and Steve K. Sherrod, Successful nesting by a pair of bald eagles at ages three and four, 113-114 N Natural cavities, 143-148 Negro, Juan Jose, see Brodeur, Serge Negro, Juan Jose, see Bustamante, Javier Nematoda, 34-38 Nest, 259-262 boxes, 127-133, 134-142, 143-148, 149-153, 154-157 defense, 93-99 predation, 143-148 site, 127-133 82 Index to Volume 28 VoL. 29, No. 1 Nest-site selection, 13-18 use, 154-157 Nesting, 1-3, 110-112, 113-114 O Obst, Joachim, Tree nesting by the gyrfalcon (Falco rus- ticolus) in the western Canadian Arctic, 4-8 Olson, David, see Hunter, John E. Ornithoica vicina, 232-235 Ortega-Rubio, Alfredo, see Castellanos, Aradit Otus asio, 93-99, 154-157 flammeolus, 43-44 Owl, barn 134-142, 149-153 eastern screech, 93-99, 154-157 flammulated, 43-44 great horned, 164-170 long-eared, 253-258, 265-268 spotted, 232-235 tawny, 34-38, 115-117, 134-142, 246-252 P Papageorgiou, Nikolaos K., see Vlachos, Christos G. Parasitism, 34-38, 143-148 Parathion, 108-109 Parental care, 171-177 Pavelka, Mark A., see Knittle, C. Edward Petty, Steve J., Geoff Shaw and David I.K. Anderson, Value of nest boxes for population studies and con- servation of owls in coniferous forests in Britain, 1 34- 142 Plasma enzymes, 27-33 Play, 79-83 Plumage, 113-114 Poisoning, 108-109 Pokras, Mark, see Powers, Lauren V. Pomarol, Manel, Releasing Montagu’s harrier (Circus py- gargus) by the method of hacking, 19-22 Poplar plantations, 13-18 Population, 127-133 Post-fledging, 158-163 dependence period, 79-83, 171-177 Power snare, 268-273 Powers, Lauren V., Mark Pokras, Kim Rio, Cathy Viv- erette and Laurie Goodrich, Hematology and occur- rence of hemoparasites in migrating sharp-shinned hawks (Accipiter striatus) during fall migration, 178- 185 Predation, 43-44 Preparation for feather identification, 192-193 Prevalence, 226-231 Prey analysis, 192-193 size, 253-258 size selection, 246-252 Prieto, Felipe G., see Chavez-Ramirez, Felipe Pterocles alchata, 236-241 orientalis, 236-241 Q Quebec, 220-225 R Raptors, 226-231 Raptor disturbance, 236-241 roadside survey, 186-191 Redpath, S.M. and I. Wyllie, Traps for capturing terri- torial owls, 115-117 Referees for 1993, 72 Rehabilitation, 27-33, 100-107 Reid, David H., see Mabie, David W. Relative abundance, 186-191 Releasing, 19-22 Reproduction, 4-8, 127-133, 220-225, 259-262 Reynolds, Richard T., see Linkhart, Brian D. Rio, Kim, see Powers, Lauren V. Ritchison, Gary, see Sproat, Thomas McKell Roost site, 9-12 Rubbish dump, 242-245 S Sabo, Beth Ann and Roxie C. Laybourne, Preparation of avian material recovered from pellets and as prey re- mains, 192-193 Salinas-Zavala, Federico, see Castellanos, Aradit Sandgrouse, 236-241 Seasonal abundance, 242-245 variation, 253-258 Sexual differences, 23-26 Shaw, Geoff, see Petty, Steve J. Sheffield, Steven R., Cannibalism of a young barn owl (Tyto alba) by its parents, 119-120 Sherrod, Steve K., see Mulhern, Daniel W. Shiraishi, Satoshi, see Koga, Kimiya Slovenia, 253-258 Spain, 23-26, 84-92, 242-245 Sproat, Thomas McKell and Gary Ritchison, The anti- predator vocalizations of adult eastern screech-owls, 93-99 Steenhof, Karen, George P. Carpenter and James C. Bed- narz, Use of mist nets and a live great horned owl to capture breeding American kestrels, 194-196 Stohlgren, Thomas J. and Chris A. Farmer, Reevaluating delineated bald eagle winter roost habitat in Lava Beds National Monument, California, 205-212 Stress, 178-185 Strigiformes, 226-231 Strigiphilus syrnii, 232-235 Strix aluco, 34-38, 115-117, 134-142 occidentalism 232-235 Subadult, 113-114 March 1995 Index to Volume 28 83 Survey, 259-262 Survival, 213-219 T Techniques, 194-196 Telford, Sam R., Jr., see Forrester, Donald J. Territorial behavior, 115-117 Territoriality, 23-26 Texas, 213-219, 262-265 Tiso, Eugenio, see Bogliani, Giuseppe Tome, Davorin, Diet composition of the long-eared owl m central Solvenia: seasonal variation in prey use, 253- 258 Trapping, 115-117, 194-196 Tree-cavity nests, 154-157 Tree nesting, 4-8 Turkey, 186-191 Tyto alba, 134-142, 149-153 U Urban and rural area, 246-252 V Vigilance, 236-241 Viverette, Cathy, see Powers, Lauren V. Vlachos, Christos G. and Nikolaos K. Papageorgiou, Diet, breeding success, and nest-site selection of the short- toed eagle {Circaetus gallicus) in northeastern Greece, 39-42 Vocalizations, 93-99 Vulture, bearded, 73-78 W Watkins, Michael A., see Mulhern, Daniel W. White, Clayton M., A review of Las Rapaces Ibericas, by J.L.G. Grande and F. Hiraldo, 200-201 White, Clayton M., A review of The Peregrine Falcon, by Derek Ratcliffe, 276-277 Wiebe, Karen L., Facultative manipulation of hatching asynchrony in the American kestrel (Falco sparverius) (Dissertation Abstract), 123-124 Wiggers, Ernie P., Productivity and nesting chronology of the Cooper’s hawk and sharp-shinned hawk in Mis- souri, 1-3 Winter, 9-12 Wright, Robert G., see Farquhar, C. Craig Wyllie, I., see Redpath, S.M. Y Yahner, Richard H., see Morrell, Thomas E. Z Zalewski, Andrzej, Diet of urban and suburban tawny owls (Strix aluco) in the breeding season, 246-252 Zyl, Anthony J. van, see Jenkins, Andrew R. Free On-Line Document Search... Discount on Document Delivery UnCaver Announcing Access to UnCover Document search and delivery for readers of Journal of Raptor Research You can now access free of charge the UnCover on-line database of the complete table of contents information from over 15,000 journals. In addition, you can order delivery of fiill text of articles at a discount of $2.00 per article off the regular document delivery price — a discount normally available only to UnCover subscribers who pay an annual password fee. With. Access to UnCover, you can search for articles on particular topics, by particular authors, or from particular Journals. You can then order on-line the full text of articles for delivery by fax within 24 hours. Document delivery fees will be billed to your credit card. Access to UnCover is available now over the Internet. Simply Telnet to the Access to UnCover Address: allen.carl.org At the prompt, enter the Password: DELIVER Access to UnCover makes it easy to find the articles you need. THE RAPTOR RESEARCH FOUNDATION, INC. (Founded 1966) OFFICERS PRESIDENT: Michael W. Collopy SECRETARY: Betsy Hancock PRESIDENT-ELECT: David M. Bird TREASURER: Jim Fitzpatrick VICE-PRESIDENT: Michael N. Kochert BOARD OF DIRECTORS EASTERN DIRECTOR: Brian A. Millsap CENTRAL DIRECTOR: Robert N. Rosenfield MOUNTAIN 8c PACIFIC DIRECTOR: Karen Steenhof CANADIAN DIRECTOR: Gordon S. Court INTERNATIONAL DIRECTOR #1: Jemima ParryJones INTERNATIONAL DIRECTOR #2: M. Isabel Bellocq DIRECTOR AT LARGE #1: James C. Bednarz DIRECTOR AT LARGE #2: John A. Smallwood DIRECTOR AT LARGE #3: Keith L. Bildstein DIRECTOR AT LARGE #4: Josef K. Schmutz DIRECTOR AT LARGE #5: Petra Bohall Wood DIRECTOR AT LARGE #6: Katherine McKeever EDITORIAL STAFF JOURNAL EDITOR: Carl D. Marti, Department of Zoology, Weber State University, Ogden, UT 84408-2505 U.S.A. ASSOCIAl’E ItDirORS Ki’ini L. Bildsikin Fabian Jaksk. Gary R. Borloloi i i Pai kicia L. Ke nnedy CllARLESj. Henny Erkkj Koki’imaki BOOK REVIEW EDHOR: Jeffreys. Marks, Hawaiian Islands National Wildlife Refuge, P.O. Box 50167, Honolulu, HI 96850 U.S.A. EDITOR OF RRF KETTLE; Richard J. Ciark The Journal of Raptor Research is distributed quarterly to all current members. Original manuscripts dealing with thi’ biology and conseivation of diurnal .and nocturnal birds of prey are welcomed from thi'oughoiit the world, but must be written in English. Submissions can be in the form of research articles, letters to the editor, thesis alistracts and book reviews. Contributors should submit a typewritten original and three copies to the Editor. All submissions must be typewritten and double-spaced on one side of 216 X 278 mm {SVi X 11 in.) or standard international, white, bond paper, with 25 mm (1 in.) margins. The cover page should contain a title, the author’s full name(s) and address (es). Name and address should be centered on the cover page. If the current address is different, indicate this via a footnote. A short version of the title, not exceeding 35 characters, should be procided for a running head. An abstract of about 250 words should accompany all research articles on a separate page. Tables, one to a page, should be double-spaced throughout and be as.signed consecutive Arabic numer- als. Collect all figure legends on a separate page. Each illustration should be centered on a single page and be no smaller than final size and no larger than twice final size. 4'he name of the author (s) and figure number, assigned consecutively using Arabic: numerals, should be pencilled on the back ctf each figure. Names for birds should follow the A.O.U. Checklist of North American Birds (6th ed., 1983) or another authoritative source for other regions. Subspecific identification should be cited only when pertinent to the material presented. Metric units should be used for all measurements. Use the 24-hour clock (e.g., 0830 H and 2030 II) and “continental” dating (e.g., 1 January 1990). Refer to a recent issue of the journal for details in format. Explicit instructions and publication policy are outlined in “Information for contributors,” /. Raptor Res., Vol. 27(4), and are available from the editor. 1995 ANNUAL MEETING The Raptor Research Foundation, Inc. 1995 annual meeting will be held on 1-4 November at the Duluth Entertainment and Convention Center in Duluth, Minnesota. Details about the meeting and a call for papers will be mailed to Foundation members in the summer, and can be obtained from Dan Varland, Scientific Program Chairperson, Rayonier, Northwest Forest Resources, 413 8th Street, Hoquiam, WA 98550, (telephone 360 538-4582; FAX 360 532-5426; e-mail DanieLVar- land@RAYNR.CCMAIL.COMPUSERVE.COM), and Gerald Niemi, Local Chairperson, Natural Re- sources Research Institute, University of Minnesota Duluth, Duluth, MN 55811 (telephone 218 720- 4279; e-mail GNIEMI@SAGE.NRRI.UMN.EDU). For information about the associated symposium “A Comparison of Forest Raptor Responses to Forest Management — ^AHolarctic Perspective,” con- tact Gerald Niemi. Raptor Research Foundation, Inc., Awards Recognition for Significant Contributions' The Dean Amadon Award recognizes an individual who has made significant contributions in the field of systematics or distribution of raptors. Contact: Dr. Cla}ton White, 161 WIDE, Department of Zoology, Brigham Young University, Provo, UT 84602 U.SA. Deadline August 15. The Tom Cade Award recognizes an individual who has made significant advances in the area of captive propagation and reintroduction of raptors. Contact: Dr. Brian Walton, Predatory Bird Research Group, Lower Quarry, University of California, Santa Cruz, CA 95064 U.SA. Deadline: August 15. The Fran and Frederick Hamerstrom Award recognizes an individual who has contributed significantly to the understanding of raptor ecology and natural history. Contact: Dr. David E. Anderson, Department of Fisheries and Wildlife, 200 Hodson Hall, 1980 Folwell Avenue, University of Minnesota, St. Paul, IMN 55108 U.SA. Deadline: August 15. Recognition and Travel Assistance The James R. Koplin Travel Award is given to a student who is the senior author of the paper to be presented at the meeting for which travel funds are requested. Contact: Dr. Petra Wood, West Virginia Cooperative Fish and Wildlife Research Unit, P.O. Box 6125, Percival Hall, Room 333, Morgantown, WV 26506-6125 U.SA. Deadline; established for conference paper abstracts. The William C. Andersen Memorial Award is given to the student who presents the best paper at the annual Raptor Research Foundation Meeting. Contact: Ms. Laurie Goodrich, Hawk Mountain Sanctuary, Rural Route 2, Box 191, Kempton, PA 19529-9449 U.S.A. Deadline: Deadline established for meeting paper abstracts. Grants^ The Stephen R. TuUy Memorial Grant for $500 is given to support research, management and conservation of raptors, especially to students and amateurs with limited access to alternative funding. Contact: Alan Jenkins, George Miksch SuttOn Avian Research Center, Inc., P.O. Box 2007, Bartlesville, OK 74005-2007 U.SA. Deadline: September 10. The Leslie Brown Memorial Grant for $500-$1,000 is given to support research and/or the dissemination of information on raptors, especially to individuals carrying out work in Africa. Contact: Dr. Jeffrey L. Lincer, 9384 Hito Court, San Diego, CA 92129-4901 U.S.A. Deadline: September 15. ' Nominations should include: (1) the name, title and address of both nominee and nominator, (2) the names of three persons qualified to evaluate the nominee’s scientific contribution, (3) a brief (one page) summary of the scientific contribution of the nominee, 2 Send 5 copies of a proposal (:^5 pages) describing the applicant’s background, study goals and methods, anticipated budget, and other funding.