The Journal of Raptor Research Volume 36 Number 4 December 2002

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EDITOR: James C. Bednarz, Department of Biological Sciences, P.O. Box 599, Arkansas State University, State University, AR 72467 U.S.A. ASSOCIATE EDITORS

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The Journal of Raptor Research is distributed quarterly to all current members. Original manuscripts dealing with the biology and conservation of diurnal and nocturnal birds of prey are welcomed from throughout the world, but must be written in English. Submissions can be in the form of research articles, short communications, letters to the editor, 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 (8% 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 provided 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 assigned consecutive Arabic numerals. 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. The name of the author (s) and figure number, assigned consecutively using Arabic numerals, should be pencilled on the back of each figure. Names for birds should follow the A.O.U. Checklist of North American Birds (7th ed., 1998) 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 H) and “continental” dating (e.g., 1 January 1999). 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. 36(4), and are available from the editor.

Submit manuscripts to J. Bednarz at the address listed above.

COVER: Bald Eagles {Haliaeetus leucocephalus) Painting by John Schmitt. Contents

Foraging Ecology of Nesting Bald Eagles in Arizona, w. Grainger Hunt, Ronald e.

Jackman, Daniel E. Driscoll, and Edward W. Bianchi 245

Vernal Migration of Bald Eagles from a Southern Colorado Wintering Area. Alan R. Harmata 256

Does Northern Goshawk Breeding Occupancy Vary with Nest-stand Character-

istics ON THE Olympic Peninsula, Washington? Sean p. Finn, Daniel e. Variand, and John M. Marzluff 265

Subordinate Males Sire Offspring in Madagascar Fish-Eagle {Hauaeetus vocife-

ROIDES) PoLYANDROUS BREEDING GROUPS. Ruth E. Tingay, Melanie Culver, Eric M. Hallerman, James D. Fraser, and Richard T. Watson 280

Nesting and Perching Habitat Use of the Madagascar Fish-Eagle. James Berkeiman, James D. Fraser, and Richard T Watson 287

Use of Vegetative Structure by Powerful Owls in Outer Urban Melbourne, Victoria, Australia—Implications for Management. Rayiene Cooke, Robert Waiiis, and John White 294

Nest-site Selection of the Crowned Hawk-Eagle in the Forests of Kwazulu- NATAL, South Africa, and TaI, Ivory Coast. Gerard Malan and Susanne Shultz 300

Short Communications

Juvenile Dispersal of Madagascar Fish-Eagles Tracked by Satellite Telemetry. Simon

Rafanomezantsoa, Richard T. Watson, and Russell Thorstrom 309

Prey of the Peregrine Falcon (Falco Peregiunus cassini) in Southern Argentina and Chile. David

H. Ellis, Beth Ann Sabo, James K. Tackier, and Brian A. Millsap 315

An Elevated Net Assembly to Capture Nesting Raptors. Eugene A. Jacobs and Glenn A. Proudfoot 320

Florida Bald Eagle {Hauaeetus leucocephalus) Egg Characteristics. M. Alan Jenkins, Steve K

Sherrod, David A. Wiedenfeld, and Donald H. Wolfe, Jr. 324

Osprey Ecology in the Mangroves of Southeastern Brazil. Robson Silva e Silva and Fabio Olmos 328

Diet of Breeding Tropical Screech-Owls (Otus chouba) in Southeastern Brazil. Jose Carlos Mottajunior 332

Letters

Comments of the First Nesting Record of the Nest of a Slaty-backed Forest Falcon {Micrastur

MIRANDOUEJ) IN THE ECUADORIAN AMAZON. Russell Thorstrom 335

Micrastur or Acupiter, That is the Question. Tjitte de Vries and Cristian Melo 337

Book Reviews. Edited byJeffery S. Marks 338

Information For Contributors 340

Index to Volume 36 344

The Raptor Research Foundation, Inc. gratefully acknowledges funds and logistical support provided by Arkansas State University to assist in the publication of the journal. THE JOURNAL OF RAPTOR RESEARCH

A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC.

VoL. 36 December 2002 No. 4

FORAGING ECOLOGY OF NESTING BALD EAGLES IN ARIZONA

W. Grainger Hunt/ Ronald E. Jackman, and Daniel E. Driscoll Predatory Bird Research Group, Long Marine Laboratory, University of California, Santa Cruz, CA 93060 U.S.A.

Edward W. Bianchi Entrix, 7919 Folsom Blvd., Suite 100, Sacramento, CA 93826 U.S.A.

Abstract.—^We studied foraging ecology of nesting Bald Eagles (Haliaeetus leucocephalus) in Arizona during 1987-89, with emphasis on the influence of dams and river flow regulation. We examined diet, foraging modes, habitat selection, fish abundance, and factors associated with fish availability. Based on biomass, prey remains yielded 76% fish, 14% mammals, and 10% birds. On rivers, eagles primarily caught live fish as they spawned or foraged in shallow water, whereas, on reservoirs, most fish were obtained as carrion or as they floated moribund on the surface. Fish communities differed among river reaches and reservoirs, and ecological and life-history characteristics influenced vulnerability and seasonal differences in exploitation, Water temperature, a principal factor determining fish community structure among eagle territories, was also associated with temporal differences in fish availability, as was flow and turbidity. Few prey sources remained constant throughout the reproductive cycle, and prey and habitat diversity buffered temporal changes in prey availability. We conclude that dams benefit breeding eagles to the extent that they create water temperature discontinuities and additional aquatic habitats, some that support large populations of fish. However, environments modified by dams are not necessarily better for Bald Eagles than those on free-flowing sections of rivers; our data show that Bald

Eagle reproduction in the two settings is nearly identical.

Key Words: Bald Eagle, Haliaeetus leucocephalus; dams; habitat selection; home range, piscivory; radiotelemetry; rivers.

ECOLOGIA DEL FORRAJEO DE AGUILAS CALVAS NIDIFICANDO EN ARIZONA

Resumen.—Estudiamos la ecologia de forrajeo de aguilas calvas {Haliaeetus leucocephalus) nidificando en Arizona durante 1987-89, con enfasis en la influencia de los embalses y la regulacion del flujo de los rios. Examinamos la dieta, modos de forrajeo, seleccion de habitat, abundancia de peces, y factores asociados con la disponibilidad de peces. Tomando como base la biomasa, los restos de presas arrojaron 76% peces, 14% mamiferos, y 10% aves. En los rios, las aguilas ante todo capturaron peces vivos cuando estos desovaban o forrajeaban en aguas someras, mientras que, en los reservorios, la mayoria del pescado fue obtenido como carrona o cuando flotaban moribundos sobre la superficie. Las comunidades de peces difirieron entre los limites de los rios y las caracteristicas ecologicas y de su historia de vida las cuales influyeron en la vulnerabilidad y las diferencias estacionales en la explotacion. La temperatura del agua, un factor primordial determinante de la estructura de la comunidad ictica entre los territorios de las aguilas, fue asociada ademas con las diferencias temporales en disponibilidad de peces, tal como lo fue con el flujo y la turbidez. Pocos recursos de presas permanecieron constantes a traves de todo el ciclo reproductivo, y las presas y diversidad de habitats amortiguaron los cambios temporales en la disponibilidad de presas. Concluimos que los embalses benefician las aguilas que estan reproduciendose en el sentido en que crean discontinuidades en la temperatura y habitats acuaticos adicionales, algunos

^ Present address: The Peregrine Fund, 5568 West Flying Hawk Lane, Boise, ID 83709 U.S.A.; e-mail address: [email protected]

245 , , ,

246 Hunt et al. VoL. 36, No. 4

de los cuales soportan grandes poblaciones de peces. Sin embargo, los ambientes modificados por las represas no son necesariaraente mejores para las aguilas pescadoras que aquellos que estan en secciones de libre flujo en los rios; nuestros datos muestran que la reproduccion de las aguilas pescadores en los dos escenarios son cercanamente identicos. [Traduccion de Cesar Marquez]

Population persistence in raptors and other ter- from ,329-1719 mask Riparian environments in these regions are composed of Sonoran Riparian Deciduous For- ritorial birds depends on an aggregate of breeding est and Woodlands Biome, Sonoran Riparian Scrubland that to locations contribute above-replacement-rate Biome, and the Sonoran Interior Strands Biome. Up- reproduction (Hunt and Law 2000). Conserving lands in the Lower Sonoran Life Zone are all within Son- high-quality sites requires knowledge of key com- oran Desertscrub Biome (Brown 1998). Upper Sonoran ponents, some being physiographic, others de- Life Zone (Brown 1998) vegetative composition near Bald Eagle breeding territories includes Great Basin Co- pending on the ecology, behavior, and life-history nifer Woodland, Interior Chaparral, and Semidesert characteristics of associated biota. Of particular in- Grassland Biomes. Mean annual precipitation ranges terest are factors relating to food acquisition. Re- from 39 cm at higher elevations to 25 cm in the low productive success requires that breeding pairs desert where temperatures may reach 50°C. The central Arizona landscape has been greatly altered have sustained access to prey within efficient com- by human activity. Cattle grazing, particularly after railway muting distance (Royama 1970). For species with development in the late 1800s, resulted in dramatic ero- prolonged breeding cycles (ca. 5 mo for North sion (Hastings 1959, Hastings and Turner 1965, Hayden American eagles), during which numerous phe- 1965). This and woodcutting reduced riparian forests to nological events transpire, food continuity may in- a scattering of isolated groves and trees. Soil loss drained near-surface aquifers, creating drier soil conditions, and volve switching from one prey type to another over livers became muddy torrents following rains. With the the course of the nesting season et al. (Jamieson increased need for flood control, water storage, and ir- 1982, Edwards 1988). rigation, hve impoundments were constructed on the Prey remains collected from nests of inland- Salt River and two on the Verde River during the early 1900s. Riverine environments downstream of the reser- breeding Bald Eagles {Haliaeetus leucocephalus) of- voirs were changed by flow regulation and sediment fil- ten show dietary diversity. This has been observed tration, and upstream by migrations of fish populations not only for populations as a whole, but for indi- such as common carp {Cyprinus carpio) and catfish (Ic- vidual nests (Todd et al. 1982, Jackman et al. 1999). taluridae) out of the reservoirs.

Thus, it is tempting to hypothesize that prey variety Fisheries. Three native species of fish, appropriate for eagle exploitation, remain in substantial numbers within and, by inference, environmental variation within the study area: desert sucker {Catostomus insignis), Sonora the foraging range are important components of sucker (C. clarki), and roundtail chub {Gila robusta) Bald Eagle territories in some regions (Grubb (Minckley 1973). Introduced species of potential impor- 1995). tance to eagles in rivers and/ or reservoirs include chan- From January 1987-June 1989, we investigated nel catfish {Ictalurus punctaLus), bullhead {Ameiurus ne- bulosus and A. natalis), flathead catfish {Pylodictis olivaris) the effects of dams and flow regulation on the nest- common carp, black crappie {Pomoxis nigromaculatus) ing population of Bald Eagles in central Arizona yellow bass (Morone mississippiensis) largemouth bass {Mi- (Driscoll et al. 1999). We obtained information on cropterus salmoides), smallniouth bass {M. dolomieui), blue- the spatial and temporal aspects of foraging. We gill {Lepomis macwchirus) green sunfish {L. cyanellus), walleye (Stizostedion vitreum). recorded shifts of eagle prey use, foraging behav- and Fish distribution in central Arizona, as elsewhere, is ior, and ranging patterns that followed temporal strongly influenced by water temperature (Vannote et al variation in factors influencing prey availability. We 1980, this study). Trout (Salmonidae) inhabit cool head- found that water temperature and clarity, the struc- waters. Suckers, smallmouth hass, and then channel cat- ture of various riverine and lacustrine habitats, and fish increase in abundance as water warms downstream With increasing water temperature, carp and catfish be- life-histories and behavior of prey species were in- come the primary species in size categories suitable for terrelated with respect to food availability. Bald Eagle foraging. When a river enters a reservoir, perciforms (hass, perch, and crappie) predominate, al- Study Area though carp and catfish cemtribute importantly to overall General Description. Our study centered on Bald Ea- fish biomass in the reservoir. Water temperature and vol- gle breeding territories along the Salt and Verde rivers ume released from the reservoir influence the fish com- in central Arizona (Fig. 1), a generally open, desert land- munity below the dam. Cool releases from the hypolim- scape of the Upper and Lower Sonoran Life-Zones (Lowe nion of deep, stratified reservoirs favor sucker 1964, Brown 1998). Eagles nested at elevations ranging populations. If the reservoir is shallow or unstable and December 2002 Bald Eagle Foraging Ecology 247

Figure 1. The Salt and Verde river systems of central Arizona. The six names in italics identify breeding territories where Bald Eagle foraging was studied with radio telemetry.

fails to maintain a cool hypolimnion, or if releases issue Methods from the epilimnion, warm releases favor carp and catfish Telemetry. We used radio-controlled bow nets, power in the river reach below the dam. During spring, spawn- snares, and noosed fish (Jackman et al. 1993, 1994) to ing runs of carp and catfish from downstream reservoirs capture territorial eagles for radio-tagging. We attached may augment riverine fish populations. 65-g transmitters with a backpack configuration of teflon Study Sites. We studied Bald Eagle foraging at six ribbons adjoined with cotton string over the carina to territories (defined to include the forag- breeding here permit eventual loss of the radio (Hunt et al. 1992, to ing range) chosen compare regulated with unregulat- McClelland et al. 1994). Mercury (activity) switches ed (i.e., free-flowing) environments (Fig. 1). All six ter- changed the pulse rate when tilted from near-vertical to ritories have been occupied by eagles since the 1970s horizontal (Kenward 2001). We refined signal interpre- (Driscoll et al. 1999). Two breeding territories (Ladders tation on the basis of frequent visual verification. and East Verde) were on free-flowing rivers far from res- From the early brooding period to fledging, tracking ervoirs. Two other pairs (Bardett and Blue Point) occu- teams collected data in 8-d sessions separated by 6-d pe- pied settings in which all flows were regulated by dam riods of no data collection. The objective was to obtain releases, i.e., reservoirs releasing cold water and fed by uninterrupted, minute-by-minute records (time lines) of other dams upstream. The remaining two breeding ter- movements and activities of radio-tagged eagles. To over- ritories (Horseshoe and Pinal) included both reservoir come the bias associated with observer location, trackers systems and the free-flowing rivers that fed them. spread out to strategic viewing sites and maintained com- 248 Hunt et al. VoL. 36, No. 4 munication by hand-held radios. Tracking teams of three km segments (or larger zones) where the eagle perched. to five members later conferred to eliminate duplicate Weighting each location equally as a measure of use was data points. To reference eagle locations, habitat vari- supported by our data: in 80% of observed foraging ables, and prey, we marked river centerlines and reservoir events, the eagle perched within sight of the foraging shorelines depicted on USGS topographic maps to show location just before the event, and in 70% of cases, the 1-km and 0.1-km intervals. If we could not identify the eagle appeared to have seen the prey before leaving the eagle’s location to the level of even a 1-km segment, we perch. marked the location within larger zones positioned be- Each perching visit to a O.Tkm segment received a tween familiar landmarks. score of one point. If the eagle left a location and en- We measured variables at prey-strike points as soon as tered another O.l-km segment along the river, but then possible after a foraging event but without disturbing the returned to the original location, the latter received an- eagle. Recorded information included attack method other point. Segments visited repeatedly thereby received aquatic habitat type, as follows: “pools” are depres- and the most points. The large number of nest visits over- sions in the streambed, with hydrologic control in the shadowed other relocation scores; however, eliminating downstream end and low current velocities relative to the nest area from the analysis was inappropriate because prevailing streamflow; are deep, usu- “runs” moderately the nest vicinity was often an important foraging area. ally with relatively fast current, but little narrow channels Therefore, we used the prey delivery data to estimate the or no white water; “riffles” are characterized by shallow, percentage of foraging events occurring in the nest vicin- fast-moving water flowing down gradients and over sub- ity. This became the relocation percentage for the nest strates usually no larger than small boulders; “pocket wa- area, and percentages for all other areas within the home ter” usually contains larger boulders, with fast water in- range were adjusted accordingly so the total was 100%. terspersed across the width of the stream among frequent Collection and Analysis of Prey Remains. Collection. We pockets of quiet water; “cascades” are steep gradient collected prey remains within and below nests at five of white water with less than 10% quiet water (Hunt et al. the six breeding territories studied (one nest was on an 1992). Microhabitat features measured at strike points in- inaccessible pinnacle) and at 16 other breeding sites in cluded water depth, water temperature, and turbidity Arizona. Collections occurred during the middle to late (Secchi disk). We collected evidence (e.g., scales) of prey part of the brood-rearing period and again after the species identity, and estimated prey size and whether it young had fledged. We attributed variation in the was obtained alive or as carrion. amount of remains present to removal by the adults (ob- Prey Delivery, Observers recorded prey deliveries to served) and to the activities of woodrats (Neotoma spp.) the nests from points permitting clear views of nest bowls and other scavengers. We collected ca. 2 L of fine nest and at distances of 125-400 m, typically beginning when lining from each nest for scale analysis to detect soft- young were 2-3 wk of age. Prey items were assigned to boned fish (e.g., trout, chub) (Jackman et al. 1999). general taxonomic categories (e.g., class), then to more Analysis. We collected 5—10 individuals of differing sizes specific categories (e.g., family, species), where possible. of each fish species expected to occur in the eagles’ diet. For fish, diagnostic features included fin and scale char- We weighed and measured each fish, then parboiled it acteristics, body and mouth shapes, jaw configurations, to remove all flesh. We weighed, dried, and labeled all barbel presence, caudal peduncle thickness, and mark- bones for reference. ings. Observers noted their confidence in each identifi- We developed regression equations to relate bone cation; items identified with low confidence were as- length to total body length for each species (Hunt et al. signed to a higher taxonomic level. We sometimes 1992, Jackman et al. 1999). Because unattached bones confirmed identification with body parts (e.g., scales) col- were often from the same fish, we used the following lected at eagle foraging sites. We did not distinguish be- procedure to avoid duplication: first, we determined the tween desert and Sonora suckers. We estimated prey size 95% confidence intervals from each equation to deter- by comparing the item with the length of the eagle’s bill mine the probable range of total length represented by or with objects of known size in the nest. the bones. For a given collection and species, we calcu- Analysis of Tracking Data. Time line tracking data con- lated fish total length from each bone and then sorted sisted of 22 742 records of the movements and activities all like bones. Bones with the most entries and relatively ol nine radio-tagged adults in six breeding territories, for a mean of 2327 records per tagged eagle. We recorded low confidence intervals were examined first. We pairs these of the size the number of minutes an eagle remained at a location grouped of bones same (<1.0 mm difference or for e.g., left and the frequency of visits to each location. The first <5 mm broken bones), and mea.sure (time) offered a relatively poor estimate of area right opercula. We marked each pair and the remaining use compared to relocation frequency. Consider an ex- odd entries as individual prey items. We next matched ample in which an eagle loafed for 146 min at a location the opcrcula(s) from one fish with other bones whose 300 m downstream of the nest (in sight of the nest), then confidence intervals for total body lengths overlapped flew 2 km upstream where it perched for 5 min at each with those computed from the opercula. Because differ- of three locations, some 200 m apart. At the last of these, ent parts of the same fish had specific proportional re- the eagle caught a fish, after which it returned to the lationships (e.g,, ±2.0 mm for sucker opercula and clav- nest area where it spent 62 rain. Clearly, a time-based icles), we eliminated those entries that were eclipsed by assessment awards small significance to the foraging area the confidence intervals, a procedure that left the fewest where the eagle spent only 2% of its time. By contrast, numbers of unmatched parts and, thus, the fewest pos- the relocation-based appraisal recognized each of the 0.1- sible number of individual fish represented. Results un- .

December 2002 Baed Eagi.e Foraging Ecology 249

derestimated total fish numbers to the extent that boat, identifying and measuring all carrion fish, birds, matched parts may have been from different fish. and mammals encountered. We noted factors contribut- We calculated total mass for the selected (nondupli- ing to death, e.g., trauma, evidence of spawning, fishing cate) fish prey items, using length-to-mass equations from paraphernalia. On rivers, we selected one to three 100- this study and from Carlander (1969, 1977) and Becker m areas in each territory where carrion was likely to ac- (1983). We subtracted the mass of bones and scales cumulate, and with particular attention to channel (from regression equations) plus 5% of total mass (esti- bends. We surveyed for waterbirds from one or two mated unavailable biomass) to calculate the edible bio- points offering wide views per territory, or by making mass for each prey item. We identified nonfish remains counts while traveling along water bodies (e.g., during from museum reference collections and then used stan- carrion surveys), noting the species and numbers pres- dard body mass for each species less 10% for inedible ent. parts. Fish Sampling. Objectives of fish sampling within eagle Results territories were to identify: (1) relative abundance of prey Diet. We identified 19 species of fish, 26 birds, fish, (2) seasonal changes in their distribution, with emphasis on availability to eagles (e.g., fish moving into shal- 16 mammals, and three reptiles from (1) the re- low water), (3) spawning and its effect on fish availability, mains of 2601 prey individuals collected from and (4) effects of water management on prey fish avail- nests, under perches, and after foraging events at ability. 23 breeding territories, and (2) observations of Fish abundance, activity, and distribution. We conducted prey items delivered to nests (Table both roving and fixed-point visual surveys. In roving sur- 713 1). Mean veys, one or two biologists (depending upon flow) walked biomass percentages for each class in remains from along the river bank, noting abundance and activity of all sites were 75.5% fish, 14.3% mammals, and fish, aquatic habitat, depth, location (within standard 0.1- 10.2% birds. Four groups accounted for nearly all km segment), and water temperature. We also observed fish biomass: catfish (mainly channel catfish), suck- fish activity and behavior from fixed points. Prior to sur- (desert veying, we compiled information on fish communities in er and Sonora suckers), carp, and perci- the various river reaches, tributaries, and reservoirs, in- forms (mainly largemouth bass, black crappie, and cluding Arizona Game and Fish Department (AGFD) yellow bass). Seven taxa exceeded 15% of fish bio- and U.S. Fish and Wildlife Service reports and field data mass at one or more of 23 territories sampled in from D. Henrickson (AGFD), M. Jakle (U.S. Bureau of central Arizona: sucker at 12 territories, carp at 12, Reclamation), and C. Zeibell (Arizona Cooperative Fish- eries Unit) channel catfish at 10, largemouth bass at six, flat- To verify our observational data and to determine go- head catfish at three, crappie at two, and yellow nadal development, we sampled fish in representative bass at two. habitats with gill nets and throw nets, and occasionally by Comparisons of prey remains with prey deliver- snorkeling surveys. We removed all collected fish from ies over similar time frames consistently showed the system, many of which were used in the prey reference series. We conducted an electrofishing survey at the that biomass estimates from remains overrepre- East Verde territory just after the eagle nesting season. sented mammals and birds over fish, and catfish surveys. habitat dis- Aquatic habitat We surveyed aquatic over suckers and perciforms (Hunt et al. 1992). In tribution in four of the six eagle territories. We mapped three territories where items and deliveries were sections of rivers and tributaries within eagle home rang- within comparable time frames, 7 of 56 fish es into basic habitat units, including pools, runs, riffles, pocket water, and cascades, as defined by Hunt et al. (10.3%) identified in remains were suckers, where- (1992). We differentiated between two types of riffles: as 124 of 342 (33.2%) fish deliveries were suckers channel-riffles, which become runs during moderate flow 7* (X^ = 13.1, df — 1, = 0.0003). Remains versus increase, and bar-riffles which remain as riffles under a delivery ratios for catfish in these samples were 24: variety of flows. Bar-riffles are characterized by the pres- = = ence of a gravel/ cobble bar oriented diagonally or per- 56 (42.8%) and 56:342 (16.4%) (x^ 47.6, df pendicularly to flow. As flow increases, water depth and 1, P < 0.0001). An experiment involving a blind velocity increase only partially in bar-riffles, whereas the sample of 45 fish fed to a captive eagle supported of shallow water increases overall due to spread- amount our field data in that soft-boned fishes tended to ing of water across the gravel/ cobble bar. We mapped be underrepresented, e.g., 100% of carp appeared reservoirs according to distributions of shallow water ar- catfish, eas. We obtained river flow and reservoir water surface in the remains, 80% of 60% of the some- elevation data from agencies maintaining gaging stations. what softer-boned suckers, and only 8% of trout (T. Carrion and Waterbird Surveys. We conducted peri- Gatz and M. Jakle, unpubl. data). odic surveys on rivers and reservoirs to assess temporal As expected, suckers were the most common availability of carrion. We sampled representative stretch- prey for pairs nesting on cool, free-flowing reaches es of reservoir shoreline where we expected carrion to accumulate, e.g., coves, bends, and especially where riv- nearest the headwaters or at sites offering access ers entered reservoirs. We slowly followed shorelines by to regulated river reaches downstream of hypolim- 250 Hunt et al. VoL. 36, No. 4

Table 1. Prey biomass estimates from prey remains and observed prey deliveries (in italics) for fl Bald Eagle territories on the Salt and Verde rivers where sample sizes exceeded 40 items. Letters in parentheses refer to dam releases from the cool hypolimnion (C) or the warm epilimnion (W).

Percent Biomass

Breeding Perci- Mam- Area Setting N Suckers Carp Catfish forms mals Birds Other

Ladders Free-flowing river 79 8 48 20 1 18 5 0 deliveries 130 45 33 17 0 3 0 2 East Verde 95 5 47 27 2 12 5 2 deliveries 103 14 49 17 8 6 0 6 Redmond 156 5 18 55 1 12 4 5

Final Free-flowing river 107 5 19 47 13 8 8 0 deliveries and reservoir 46 0 10 55 27 0 3 5

Horseshoe 95 1 8 36 31 4 19 1 deliveries 48 0 34 11 40 2 0 13

Blue Point Regulated river (C) 85 10 7 21 22 18 22 0 deliveries and reservoir 152 28 2 9 41 8 8 4 Bartlett 47 55 11 18 7 9 0 0 deliveries 234 66 2 9 15 6 0 2

Orme Regulated river 56 45 4 3 2 34 12 0

Et. McDowell 62 66 5 5 1 18 5 0

Chff Regulated river (W) 45 0 46 18 27 5 4 0 and reservoir

“76” Creek 59 5 38 2 1 41 13 0

netic dam releases (Table 1). Perciforms were tak- compared with fish) were 50% in December, 56% en mainly in the reservoirs. Eagles obtained carp in January, and 13% in February, as compared with primarily in warm, free-flowing reaches upstream 5% in March, 1 % in April, and 0% in May. The most of reservoirs and in a river fed by epilimnetic re- commonly recorded birds taken among 30 identi- leases (Table 1). Catfish (channel and flathead) fied were American Coots {Fulica americana, N— 15) were widely utilized, the highest numbers taken and Eared Grebes {Podiceps nigricollis, N = 8). from free-flowing river reaches and in a reservoir Conditions of Prey Acquisition. Eagles took (Alamo) with only seasonal inflow (Haywood and some fish species only in riverine conditions, oth- Ohmart 1986). ers only from reservoirs, and some from both. Of Estimates of mammal biomass from remains ex- the seven important fish taxa recorded during prey ceeded 25% at six breeding territories. Most fre- delivery observation, numerical ratios of their ori- quently identified were black-tailed jackrabbit {Le- gin in rivers versus reservoirs at four territories pus californicus) and cottontail rabbit (Sylvilagus containing both environments were as follows (riv-

audubonii). We recorded only 32 mammals among er : reservoir) yellow bass (0:31), crappie spp. (0; : 713 prey items observed delivered to nests (4.5% 40), largemouth bass (2:22), flathead catfish (3:5), of items) despite a more substantial representation channel catfish (4:17), sucker spp. (105:0), and m prey remains from those nests (18.3%). We at- carp (3:30). In reservoirs, eagles obtained most fish tribute this disparity to the greater use of mammals as carrion (or moribund), i.e., 66% of 125 fish of early in the breeding season and to biases associ- known status (excluding piracies) were obtained ated with bone persistence. from reservoirs as carrion, whereas 12% of 201 fish Waterbirds were more important to Bald Eagles from rivers were carrion. in early winter than during the nesting season, par- Suckers. At least 83% {N = 114) of suckers were ticularly at territories containing reservoirs. In win- alive when taken, 5% were pirated, 3% were car- ter, the percentages of birds observed taken (as rion, and 9% were of unknown status. Bald Eagles .

December 2002 Bald Eagle Foraging Ecology 251

caught them mainly in riffles while they spawned fles disproportionate to their occurrence along ihe or foraged. Of 64 depth measurements at strike river. At Ladders, 54% of 58 prey captures were in points for live suckers, 80% were in water <30 cm riffles, the latter composing only 5% of riverine in depth; mean depth at strike points of these 51 habitat within the 22-km foraging range of the ea- shallow water captures was 16.4 cm (SD ± 7.3). gles. At East Verde, 46% of 61 observed foraging Carp. Eagles obtained carp from both rivers and events were in riffles, compared to 15% availability reservoirs. In rivers, eagles caught them in the shal- within 19 river km. Along 2-3 kilometers of river at lows of runs and riffles, 17 of 20 strikes in water Bartlett, 73% of 119 observed foraging attempts less than 36 cm deep. We were unable to deter- were in riffles compared with 8% availability. At mine under what conditions carp were captured in Blue Point, 32% of 28 attempts were in riffles com- reservoirs. pared with 4% availability. The frequency of riffle Catfish. We estimate from prey collections that use in part reflected the high proportion of sucker channel catfish contributed almost three times the captures in those territories. As noted, eagles cap- biomass as flathead catfish (301 182 g versus 92 304 tured suckers mainly in riffles, carp most often in g, respectively). Excluding piracies, we observed runs, and channel catfish in pocket water and runs. nesting Bald Eagles taking channel catfish on 51 In 162 measurements of turbidity at strike points occasions: 75% on reservoirs and 25% on rivers. for live fish, 136 (84%) were in water that was On reservoirs, 81% of 26 catfish of known status “clear to the bottom.” When rivers became turbid were obtained as carrion, whereas on rivers, 27% during prolonged periods of snowmelt, eagles of 11 were carrion. Although the sample of con- tended to forage elsewhere, such as in clear trib- ditions at strike points for live channel catfish in utaries. rivers was small, it differed from those noted for At the four breeding areas containing both riv- other species. Eagles captured five in pocket water, erine and reservoir environments, eagles mostly three in runs, and none from riffles. The mean of foraged from reservoirs (>50% of locations). At six depth measurements was 58 cm (SD ± 28.1). two territories where eagles nested on the river 3.6 We occasionally observed catfish swimming near km and 7.0 km from reservoirs, 51% and 61% of the surface in riverine pools (Van Daele and Van total relocations were on the reservoirs, respective-

Daele 1982), and “blooms” of carrion channel cat- ly. For a radio-tagged pair whose nest was situated fish (ca. 20 cm long) appeared in late spring at two where a river entered a reservoir, 85% and 86% of reservoirs (Horseshoe and Roosevelt) relocations were on the reservoir. At a territory Perciforms. At four breeding territories contain- where the nest was about 2 km from both river and ing reservoirs (Bartlett, Saguaro, Horseshoe, and reservoir, 59% of relocations were on the reservoir. Roosevelt), we recorded delivery of 61 largemouth Among a biomass total of 113.5 kg of delivered bass, 51 black crappie, 41 yellow bass, and 14 oth- prey items recorded at these four territories, ers (mainly sunfish). Eagles obtained these perci- 28.4%, 65.9%, 93.9%, and 48.4% were obtained forms mainly as carrion from the reservoir or as from the reservoir. Of 641 forage attempts record- they lay moribund at the surface. Of 76 dead or ed at these territories, 386 (60%) were on reser- moribund perciforms found in carrion surveys on voirs. these same reservoirs, 29 were yellow bass, 15 large- Foraging Range. Free-flowing river. We compared mouth bass, 13 black crappie, eight bluegills, four eagle foraging ranges at two territories (Ladders smallmouth bass, four green sunfish, and three and East Verde) situated on the free-flowing Verde walleye. The yellow bass and black crappie were River far upstream of the dams and reservoirs (Fig. apparent victims of spawning stress, whereas many 1). The nests of both pairs were on cliffs overlook- of the largemouth fatalities were angler-related. ing the river: the two nests at Ladders were directly Birds and Mammals. Coots were attacked when over bar-riffles, but the East Verde nest was about they foraged in the grassy shallows of reservoirs. 1 km from the nearest bar-riffle. At both territo- Eagles caught grebes and waterfowl either by ries, the null hypothesis of random selection by the stooping repeatedly at groups in open water or by eagles of 1-km segments containing bar-riffles was approaching low (<1 m) over the surface, snatch- rejected (Chi-square tests, P < 0.005). At East ing the prey in passing. We observed no attempts Verde, 72% of mainstem relocation points were at live mammals. within seven 1-km segments, in the aggregate con-

Habitat Use. We observed eagles foraging in rif- taining 100% of the bar-riffles within the 19 km •

252 Hunt et ajl. VoL. 36, No. 4

Fast Verde Male

(0 14 494 relocations |„ U Bar Rime J2 10 « S 8 o - c 6 d) g 4 0.

‘>7 124 125 Ti ' - *34 37« ^36 137 153 1' UO U’

V'erde River ^ ''Q" Vei e River I 'tritaiHries tribSy 4 ' _

Figure 2. Foraging range of the radio-tagged breeding male Bald Eagle at the East Verde territory. Relocation percentages in the nest vicinity were adjusted according to the proportion of observed prey deliveries from those 1- km segments (see Methods) . Open bars quantify cases in which trackers could not precisely locate the eagles; dotted lines extending laterally from open bars indicate zones of eagle occupancy for the imprecise locations (tributary relocation percentages not shown).

foraging range (123-141 km), but containing only By early May, he was foraging almost exclusively in 21% of the available channel-riffle habitat (Fig. 2). the mainstem Verde River, taking carp and catfish. At Ladders, 54% of visits within the 22 km range His use of river sections downstream of the nest were within the six 1-km segments containing bar- peaked during the mid-point of the brood cycle, riffles. then shifted dramatically to the area upstream of There were clear, seasonal shifts in prey and hab- the nest containing a large bar-riffle. itat use (Fig. 3). For example, in March, when the Regulated river and reservoir. The home ranges of Verde River was turbid, 17 of 18 prey items record- the Bartlett and Blue Point pairs (29 and 26 river- ed at the East Verde territory were mammals. In km, respectively) both contained a deep-release April, the East Verde male traveled up two relative- (cool) regulated river section below a reservoir fed ly clear tributaries to forage on spawning suckers. by a regulated reach. At both breeding territories,

80 Downstream from Nest (A C 70 Upstream from Nest 8 60 H Tributaries O

10 a P li

1-9 April 14-23 April 28 April - 7 May 13-21 May 26 May - June 4

Af =49 N =60 N = 109 A/ = 137 A/ = 121

Figure 3. Chronological shifts in ranging by the radio-tagged male at the East Verde territory to areas outside the nest vicinity. December 2002 Bald Eagle Foraging Ecology 253

most river visits by radio-tagged eagles were in the Horseshoe nest was at the upstream end of a res- vicinity of the first large cliff downstream of the ervoir, and the Pinal nest was 7 airline km up- respective dams. Suckers were abundant in riverine stream of a reservoir. All four radio-tagged adults environments at both territories. At Bartlett, a foraged primarily at the reservoir inflow. Even large bar-riffle was present near the nest cliff. This though the Horseshoe nest was at the inflow, the 1-km segment and the only two others containing use of the river was relatively low (male = 15%, bar-riffles received the three highest relocation female = 18%). Resources offered by these reser- scores (51%, 8%, and 8% of 164 river relocations voirs included wintering waterbirds and carrion of the male) within a home range containing 13 fish. As in the other four territories, the radio- km of river. At Blue Point, the 1-km segment with tagged birds at Horseshoe and Pinal changed their the highest river relocation score (56% of 314 river patterns of home range use during the course of relocations of the male in two breeding seasons) the nesting season. In winter, the Horseshoe and contained a large cliff above a bar-riffle. At both Pinal adults traveled downstream to the body of territories, the eagles traveled downstream as far as the reservoir where waterbirds were concentrated. 9 km to forage on suckers in early spring, but as By March they began foraging closer to the nest, the zones of suitable sucker spawning tempera- and both pairs traveled further to forage during tures moved upstream, the birds responded ac- the late stages of the nesting season. Home range cordingly. At Bartlett, this phenomenon is appar- sizes for the Horseshoe and Pinal pairs were 17 and ent when one divides the 1989 nesting season (26 27 river-km, respectively. February-20 May) into three equal periods. In the Environmental Setting and Nesting Success. We early period, 35% of relocations by the breeding compared reproductive performance for the peri- male were to the area within about 2 km of the od 1980-90 among breeding territories (produc- nest (3.6 km downstream of the dam), but these tive at least once during that period) in modified rose to 59% and 86% in the middle and late pe- versus unmodified environments. Productivity riods. Relocations to the area 3-10 km downstream (mean young fledged ±SE/nest year) of pairs m of the nest declined from 65% to 36% to 14% dur- areas altered by dam construction (1.07 ± 0.11, N ing the three periods. In 20 comparisons of river — 12 territories, 89 nest-years) was almost identical temperatures between the nest vicinity and a lo- to that of pairs in areas not altered by dams (1.04 cation about 5 km downstream, the downstream ± 0.10, N = 9 territories, 71 nest-years) (t — 0.08, temperatures were invariably higher (paired t-test, P = 0.94). t = 11.3, P < 0.0001). During the early period Discussion when the eagle traveled downstream so frequently, the mean stream temperature was 13.5°C at the Bald Eagle pairs foraged on a wide variety of nest vicinity and 15.5°C at the downstream loca- prey, the distribution within each diet was rarely tion. Importantly, Sonora suckers spawn at 14- skewed toward a single taxon. If anything, we un- 18°C. Sucker spawning peaked in the downstream derestimated the degree of dietary diversity by reach in mid-March and ceased by mid-April, when lumping some taxonomic groups, by underrepre- spawning in the upstream section reached its peak. senting the pre-egg-laying diet when birds and Both the Bartlett and Blue Point eagles frequent- mammals made important contributions to fat stor- ly perched and foraged in reservoir environments: age, and by not including the 4-9-wk post-fledging 51% of 334 relocation points by the Bartlett male period when dependent young remained in their were on the reservoir, and 59% {N — 765) for Blue natal territories. Our results were consistent with Point. Waterbirds (mainly American Coots and those of Grubb (1995) who hypothesized that

Eared Grebes) attracted eagles at both territories mammals may help to fill a dietary gap during pe- to the reservoir in winter. In spring, the main in- riods of high turbidity (e.g., snowmelt) when fish ducement for reservoir use in both areas was the are less visible. presence of carrion (or moribund) fish, mainly yel- Underlying the diverse and variable diet of nest- low bass (Saguaro), black crappie (Bartlett), and ing eagles were the ordering of gross habitat fea- largemouth bass (both reservoirs). tures within the landscape (e.g., reservoirs, rivers, Free-flowing river and reservoir. The Horseshoe and tributaries), the variety of aquatic habitats within Pinal breeding territories both contained a free- them (e.g., riffles, runs, pools, reservoir inflows), flowing river section that entered a reservoir. The the changing factors that influenced the timing of ,

254 Hunt et at. VoL. 36, No. 4

prey availability (e.g., flow, temperature, and tur- as late as the early 1900s, fish were so common in bidity) and the diverse natural history of each prey the Salt rivers they , lower and Gila that were sold species (e.g., spawning cycles, foraging behavior). as feed for domestic animals and as fertilizer Our radio-tracking data and observations of prey (Minckley 1973). Now, the Colorado pikeminnow, deliveries at the intensively studied territories sug- the razorback sucker, and the bonytail chub are gested that prey sources for nesting eagles rarely federally listed as endangered. remained constant throughout the reproductive Although we cannot be certain if the commu- cycle. nities of native fishes occurring in the pristine riv- support that prey habitat di- Our findings and ers supported nesting eagles, it is quite possible versity are important to many Bald Eagle pairs in that the four species of suckers, augmented by wa- Arizona, allowing for continuous food availability terfowl and spawning runs of pikeminnow and pos- through a lengthy breeding season. Thus, it would sibly others, formed a complete prey base. Because seem that dams may benefit Bald Eagles to the ex- suckers feed and spawn in shallow water, they are tent of creating water temperature discontinuities ideal prey for eagles. Our study suggests that eagles and additional aquatic habitats, some with large would have benehted if the native fishes were to populations of fish. However, environments modi- have spawned at different times. Such would be fied by dams were not necessarily better for Bald expected, considering that any coevolved commu- Eagles than those on free-flowing river reaches, nity of fishes would tend toward spawning differ- given that reproduction in the two settings was entials in time and space (some ascending tribu- nearly identical. Eagles do appear to benefit from taries) because of niche similarity and competition the presence of exotic fish which form major com- among fry. ponents of the eagles’ diet in both regulated and unregulated environments. ACKN OWI.EDGMENTS Even so, current conditions are not necessarily The U.S. Bureau of Reclamation (USBR) funded this more supportive of Bald Eagles than were those in work. We acknowledge the cooperation of the Arizona the pristine (pre-livestock) landscape when more Game and Fish Department (AGFD), U.S. Fish and Wild- robust, infiltrated soils likely slowed the transport life Service (USFWS), Arizona Bald Eagle Nest Watch of water to rivers which thereby maintained more Program, Salt River Project (SRP), U.S. Forest Service consistent flows over the yearly cycle of rainfall (USFS), Bureau of Land Management (BUM), Bureau of (Olmstead 1919, Hastings 1959, Hastings and Indian Affairs, and the San Carlos Apache, White Moun- tain Apache, Fort McDowell, and Salt River Pima-Mari- Turner 1965, Hayden 1965). Moreover, some copa tribes. We are grateful to D. Busch, T. Gatz, M. Jakle, stream courses, now seasonally dry, were perennial and FI. Messing (USBR) who provided direction and as- in past centuries and doubtless supported fish pop- sistance throughout the project. We also thank R. Glinski, ulations. Since the 1980s, at least nine pairs of Bald T. Tibbitts, J. Janish (AGFD), R. Hall (BLM), D. Reigle Eagles have fledged young on free-flowing reaches (SRP), and A. Harmata for help and guidance. Special and tributaries that are probably now more turbid thanks are extended to R. Mesta (USFWS) for help with data collection. G. Harris, Rassi, M. Greenburg, and D. than they would have been before the grazing era. J. Blakely (SRP) negotiated SRP helicopter assistance for Today, Bald Eagles nesting upstream of reser- nest climbs. D. Stewart, T. Noble, M. Ross, R. Kvale, D. voirs feed primarily on four fish species: Sonora Pollock, and D. MacPhee (USFS) provided logistical sup- suckers, desert suckers, carp, and channel catfish. port. For radio-tracking, observation, and fisheries work, Of these, only the suckers are native to Arizona. we thank BioSystems Analysis, Inc. employees G. Ahl- born, Beatty, P. Becker, V. B. Bock, P. Carroll, However, five other species of hsh of appropriate G. Behn, M. Cashman, D. CIcndenon, M. Cross, Driscoll, F. Fioc- size categories were once present: Colorado pike- J. chi, A. Gertstell, J. Gilardi, F. Hein, C. Himmelwright, A. minnow {Ptychocheilus lucius) razorback sucker {Xy- Klatzker, P. fang, F. Lapsansky, M. Larscheid, C. I.enihan, rauchen texanus), flannelmouth sucker { Caloslomus Ledig, Linthicum, S. Marlatt, Meyers, D. J. J. D. Monda, latipinnis), roundtail chub (still fairly common), N. Nahstoll, C. Page, R. Spaulding, D. Stahlecker, K. and bonytail chub {Gila elegans) (Minckley 1973). Thompson, L. Thompson, R. Thorstrorn, D. VonGonten, and K. VonKugelgen. For help with identification of prey Several reports attest to the early abundance of na- remains, we thank R. Cole, R. Miller, G. Smith, Y Petry- tive fishes (Rostlund 1952, Minckley and Alger szyn, P. Krausman, and C. Schwalbe. We thank P. Law for 1968, Haase 1972). Native Americans used them help with statistics and J. linthicum, T. Hunt, A. Har- extensively for food, as did the settlers that came mata, R. Steidl, and T. Grubb for comments on the man- to the region in the mid-1800s (Davis 1982). Even uscript. December 2002 Bald Eagle Foraging Ecology 255

Literature Cited kins. 1993. A modified floating-fish snare for capture of inland Bald Eagles. N. Am. Bird Bander 18:98-101 Becker, G.C. 1983. Fishes of Wisconsin. Univ. of Wiscon- , W.G. Hunt, D.E. Driscoli., and F. Labsansky. sin Press, Madison, WI U.S.A. 1994. Refinements to selective capture techniques for 10- Brown, D.E. 1998. Habitats of Arizona raptors. Pages Bald and Golden Eagles. / Raptor Res. 28:268-273. 17 in R.L. Glinski [Ed.], The raptors of Arizona, Univ. , W.G. Hunt, J.M. Jenkins, and PJ. Detrich. 1999 of Arizona Press, Tucson, AZ U.S.A. Prey of nesting Bald Eagles in northern California / Carlander, K.D. 1969. Handbook of freshwater hshery Raptor Res. 33:87-96.

biology. Vol. I. Iowa State Univ. Press, Ames, lA U.S.A. Jamieson, L, N.R. Seymour, and R.P. Bancroit. 1982.

. 1977. Handbook of freshwater fishery biology. Use of two habitats related to changes in prey avail-

Vol. II. Iowa State Univ. Press, Ames, lA U.S.A. ability in a population of Ospreys in northeastern Davis, G.P. 1982. Man and wildlife in Arizona: the Amer- Nova Scotia. Wilson Bull. 94:557-564. ican exploration period, 1824-1865. Arizona Game Kenward, R.E. 2001. A manual for wildlife radio tagging. and Fish Department, Phoenix, AZ U.S.A. Academic Press, London, U.K. Lowe, C.H. (Ed.). 1964. The vertebrates of Arizona. Univ Driscoll, D.E., R.E. Jackman, W.G. Hunt, G.L. Beatty, of Arizona Press, Tucson, AZ U.S.A. J.T Driscoll, R.L. Glinski, T.A. Gatz, and R.I. Mes- McClelland, B.R., L.S. Young, P.T. McClelland, J G. TA. 1999. Status of nesting Bald Eagles in Arizona. J. Crenshaw, H.L. Allen, and D.S. Shea. 1994. Migra- Raptor Res. 33:218-226. tion ecology of Bald Eagles from autumn concentra- Edwards, T.C., Jr. 1988. Temporal variation in prey pref- tions in Glacier National Park, Montana. Wildl. Mon- erence patterns of adult Ospreys. Auk 105:244-251. ogr. 125:1-61. Grubb, T. 1995. Food habits of Bald Eagles breeding in Minckley, W.L. 1973, Fishes of Arizona. Arizona Game the Arizona desert. Wilson Bull. 107:258-274. and Fish Department, Phoenix, AZ U.S.A. Haase, E.F. 1972- Survey of floodplain vegetation along AND N.T. Alger. 1968. Fish remains from an ar- the lower Gila River in southwestern Arizona. Ariz. J. chaeological site along the Verde River, Yavapai Coun-

Acad. Sci. 7:75-81. ty, Arizona. Plateau 40:91-97. Hastings, J.R. 1959. Vegetation change and arroyo cut- Olmstead, F.H. 1919. A report on flood control of the ting in southeastern Arizona./. Ariz. Acad. Sci. 1:60— Gila River in Graham County, Arizona. U.S. Gov. 67. Printing Office, Washington, DC U.S.A. and R.M. Turner. 1965. The changing mile. Rostlund, E. 1952. Freshwater fish and fishing in native Univ. of Arizona Press, Tucson, AZ U.S.A. North America. Univ. Calif. Publ. Geogr. 9:1-313. Hayden, C. 1965. A history of the Pima Indians and the Royama, T. 1970. Factors governing the hunting behav- San Carlos irrigation project. U.S. Gov. Printing Of- iour and selection of food by the Great Tit {Parus major). Anim. Ecol. 39:619-668. fice, Washington, DC U.S.A. J. C.S., R.B. Haywood, D.D. and R.D. Ohmart. 1986. Utilization of Todd, L.S. Young, Owen, Jr., and FJ. Gram- LICH. 1982. Food habits of Bald Eagles in Maine benthic-feeding fish by inland breeding Bald Eagles. / Wildl. Manage. 46:636-645. Condor 88:35-42. Van Daele, L.J. and H.A. Van Daele. 1982. Factors af- Hunt, W.G., J.M. Jenkins, R.E. Jackman, C.G. Thelan- fecting the productivity of Ospreys nesting in west- der, and A.T. Gerstell. 1992. Foraging ecology of central Idaho. Condor 84:292-299. Bald Eagles on a regulated river./. Raptor Res. 26:243- Vannote, R.L., G.W. Minshaiu, K.W. Cummins, J.R. Se- 256. DELL, and C.E. Cushing. 1980. The river continuum AND P.R. Law. 2000. Site-dependent regulation of Sci. concept. Can. f. Fish Aquatic 37:130-137. population size: comment. Ecology 81:1162-1165. Jackman, R.E., W.G. Hunt, D.E. Driscoll, and J.M. Jen- Received 26 March 2001; accepted 6 September 2002 J. Raptor Res. 36(4) :256-264 © 2002 The Raptor Research Foundation, Inc.

VERNAL MIGRATION OF BALD EAGLES FROM A SOUTHERN COLORADO WINTERING AREA

Alan R. Harmata^ Fish & Wildlife Program, Department of Ecology, Montana State University, Bozeman, MT 59717 US. A.

Abstract.—^Adult Bald Eagles {Haliaeetus leucocephalus) {N =15) wintering in the San Luis Valley (SLV),

Colorado were radio-tagged with conventional tail-mounted transmitters between 1 January-18 March 1980 and 1981 to determine migration patterns and breeding areas. Migrating eagles were followed primarily in a single vehicle with two trackers. In 1980, radio-tagged eagles (N = 4) left the wintering

grounds within a 15-d span in March but departures in 1981 (N = 7) ranged from mid-February to early April. Eagles initiated migration on days with higher temperature ranges, more clouds, and higher winds than other days during winter or spring. Subsequent travel paralleled the northward movement of the 2°C isotherm both temporally and spatially. Locations and pathways of migrating eagles were similar in both 1980 and 1981. All four eagles located on their summer range were within 102 km of each other in northeastern Saskatchewan and northwestern Manitoba. Mean distance from the SLV wintering area to breeding or summer areas of Bald Eagles was 2019 km. Adult Bald Eagles apparently migrated alone in spring with mated males leaving first. Migration flights began between 1015-1045 H MST and ended between 1715-1745 H. Mean daily movement was 180 km. Migration flight speeds averaged about 50 km/hr. Altitude of flight ranged from 30-4572 m above ground level (AGL), but most often was between 1500-3050 m.

Key Words: Bald Eagle; Haliaeetus leucocephalus; Colorado; radio-tracking, Saskatchewan; vernal migration; wintering.

MIGRACION PRIMAVERAL DE LAS AGUILAS CALVAS DESDE UN AreA DE INVERNACION AL SUR DE COLORADO

Resumen.—Individuos adultos de aguila calva {Haliaeetus leucocephalus) {N = 15) invernando en el valle de San Luis (VSL) Colorado, fueron provistos con radios transmisores convencionales montadc^s en la

cola, entre el 1 de enero-18 de marzo de 1980 y 1981 para determinar los patrones de migracion y las areas de reproduccion. Las aguilas en migracion fueron seguidas en primera instancia en un vehiculo sencillo con dos rastreadores. En 1980, las aguilas con radios {N = 4) abandonaron los campos de invernacion en un intervalo de 15 dias en marzo, pero las partidas en 1981 {N = 7) fueron entre mediados de febrero y principios de abril. Las aguilas iniciaron la migracion en dias con ranges de temperaturas mas altos, mas nubes, y vientos mas altos que otros dias durante el invierno o primavera. El subsiguiente vuelo fue paralelo al movimiento hacia el norte de la isoterma 2°C tanto temporal como espacialmente. Las localizaciones y vias de paso de las aguilas migratorias fueron similares en 1980 y 1981. Las cuatro aguilas localizadas en su rango de verano estuvieron dentro de 102 km una de otra

en el nororiente de Saskatchewan y noroccidente de Manitoba. La distancia media desde el area de invernacion del VSL a las areas de reproduccion o de verano de las aguilas calvas fue de 2019 km. Las

aguilas calvas adultas aparentemente migraron solas en primavera mientras que sus machos pareja sal- ieron primero. Los vuelos de migracion comenzaron entre 1015-1045 H MST y terminaron entre 1715- 1745 H. El movimiento medio diario fue 180 km. Las velocidades de los vuelos durante la migracion tuvieron un promedio de 50 km/h. La altitud de vuelo tuvo un rango entre 30-4572 m.s.n.m. pero la mayoria a menudo estuvo entre 1500—3050 m. [Traduccion de Cesar Marquez]

Relatively stable wintering populations of Bald out the DDT era (Ryder 1965, Alamosa National Eagles {Haliaeetus leucocephalus) existed in the San Wildlife Refuge reports 1954-83). In the 1970s, a Luis Valley (SLV) of southern Colorado through- mean of 185 (SD = 66.6) Bald Eagles was counted

in the SLV annually (V= 5; Craig 1981). However, origins of eagles wintering in the SLV were un- ^ E-mail address: [email protected] known.

256 December 2002 Bai d Eagle Vernal Migration 257

Between December—April 1977 and 1978, win- Between 7 January-18 March 1980 and 1981, 15 adult Bald Eagles were captured and radio-tagged in the SLV tering Bald Eagles (N = 36) in the SLV were All were captured by a modified “Lockhart” method marked with yellow patagial wing markers to de- (Miner 1975) with and without live Bald Eagle and Gold- termine their geographic origins or breeding areas en Eagle {Aquila chrysaetos) lure birds. Trap sites were (Harmata and Stahlecker 1993). Colormarking re- chosen on the basis of frequency and duration of the presence of two adult Bald Eagles of distinctly vealed fidelity of individual Bald Eagles to this win- dissimilar size, presumably mated, within 1.6 km. In 1981, I esti- tering area was high, but by January 1981 only mated the SIV winter population at 170 Bald Eagles three sightings of yellow-marked eagles occurred (Harmata 1984). outside the SLV and none were in a documented Gender of radio-tagged eagles was assigned by methods nesting area or during summer (Harmata and presented by Garcelon et al. (1985). Three were confirmed by behavior during copulation. All Bald Eagles Stahlecker 1993). The primary objective of the were radio-tagged with two-stage radio transmitters marking program had not been realized. Clearly, mounted proximo-ventrally on the tail. Transmitter fre- other methods were required to achieve objectives quencies were between 148.500 and 148.950 mHz. Unit in a timely and cost-efficient manner. life expectancy was ^5 mo. Transmitter, antenna, and Prior to the 1980s, technology for remotely mounting tab weighed 50-57 g. Telemetry receiving equipment included fixed channel and programmable tracking long-range movements of individual birds receivers. (i.e., satellite platform transmitter terminals or Mated status of radio-tagged Bald Eagles was deter- PTTs) was not available. However, on 28 February mined by frequency and duration of time spent in the 1978, after being tracked locally for nearly six presence of another adult eagle of distinctly dissimilar = weeks, an adult Bald Eagle wearing a conventional, size, observed copulation {N 3) in the SLV, or association with a nest site on the breeding grounds {N = 2). tail-mounted transmitter left her SLV wintering Eagles were considered unmated if diurnal movements area. She was tracked for two days over 300 km in the SLV were clearly independent of other eagles and through the most rugged portion of the Rocky they were not observed to roost away from communal Mountains, being lost only due to lack of logistical roosts with just one other eagle, as mated birds often did Climatological data associated with days that Bald Ea- planning, not our ability to maintain contact. This gles left the SLV were analyzed by stepwise discriminate serendipitous event revealed the potential of de- analysis (Dixon 1981) to investigate meteorological con- termining migration routes and breeding areas of ditions associated with initiation of vernal migration. Cli- Bald Eagles using conventional radio-tracking. This matological data recorded near the geographical center paper discusses results of subsequent long-range of the SLV (Alamosa, Colorado) were obtained from Na- tional Oceanographic and Atmospheric tracking of Bald Eagles with conventional teleme- Administration, Asheville, North Carolina Monthly Summary Sheets. Data try from one seasonal range to another prior to for days that eagles left the SLV were compared to data use of eagles (e.g., et widespread PTTs on Grubb for days randomly selected between 1 January-15 April al. 1994, Brodeur et al. 1996, Meyburg et al. 2001). 1980 and 1981 that they did not. Variables selected for comparisons among days were maximum, mean, and Objectives of this study were: (1) to determine range of temperature, percent of clear sky and mean breeding areas of adult Bald Eagles wintering in wind speed. southern Colorado and to gather information (2) Migrating eagles were followed primarily from a single regarding factors associated with initiation of ver- 4X4 vehicle with two human trackers and a dog. An nal migration, routes, duration, stopover habitats omnidirectional antenna and two element “H” yagi re- used, and other factors affecting the successful ceiving antenna were mounted on the roof of the chase vehicle. The yagi was attached to a 360° traversing mount, completion of migration. allowing for directional tracking while the vehicle was moving. Manpower and logistic limitations plus variability Study Area and Methods in departure dates, routes, and travel speeds of Bald Ea- The SLV is the largest and most southern of four large gles prevented ground tracking of more than one eagle intermountain basins in Colorado. Encompassing 6475 at a time. One tracker drove while the other operated km^, the SLV is approximately the size of the state of the receiving equipment. Both shared navigational du- Delaware. Mean elevation of the nearly-level valley floor ties. Due to often high chase speeds (up to 150 km/hr) IS 2286 masl. High (>3050 m) mountain ranges border and off-road “adventures,” visual contact with migrating the valley on east and west, merging at the northern end. eagles could not be maintained, so migration behavior The Rio Grande and Conejos rivers flow through the SLV often could not be recorded continuously, accurately, or and numerous natural warm springs and wetlands that safely. Route, direction, and speed of the chase vehicle, seldom freeze have made the SLV attractive to waterfowl therefore, often was selected primarily to maintain max- and Bald Eagles, probably for millennia. Water develop- imum audio signal strength. When contact with a mi- ments and agriculture in the 20th century have probably grating eagle was lost, an aerial search was implemented improved the attractiveness. using local air services, A two or three element yagi an- 258 Harmata VoL. 36, No. 4

FEMALES O O O • •

MALES O o

-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15

DAYS FROM VERNAL EQUINOX

Figure 1. Days from vernal equinox that radio-tagged Bald Eagles departed {N= 12) their San Luis Valley, Colorado, winter ranges to initiate vernal migration, 1978 {N = 1), 1980 (N = 4), 1981 {N = 7). Open circles indicate eagles determined to be unmated, closed circles indicate eagles that were mated (see text), and square indicates eagle of undetermined mated status.

tenna was taped to the wing strut (high wing) or step Results and Discussion (low wing) of light aircraft and the area surveyed in transect style with intermittent, “lazy” circles at high altitude. Initiation of Migration. Over half (58%) of ra- Frequencies were scanned to search for the target eagle dio-tagged Bald Eagles with known departure dates and other potential migrating birds. When contact was (N = initiated vernal migration within one reestablished and eagle’s status discerned as stationary, 12), vehicle tracking resumed. Flight altitudes were estimated week after the vernal equinox (Fig. 1). In 1980, based on eagle’s position relative to the search aircraft radio-tagged eagles {N — 4) all left the wintering and trees, geography, and structures such as buildings grounds within a 15-d span in March (Table 1). and radio towers while ground tracking. Eagles were of departure — monitored in their summering grounds with Beaver air- Range known dates {N 8) spanned craft, snow machines, and snow shoes. 50 d in 1981, with the first confirmed departure of

Table 1. Residency and mated status of radio-tagged adult Bald Eagles with known departure dates from winter ranges in the San Luis Valley (SLV), Colorado.

Minimum Residency Date Eagle Mated in SLV Designation Sex Captured Departed SLV Status'* (davs)

378 F 21 Jan. 1978 28 Feb. 1978 U 39 180 F 18 Jan. 1980 21 Mar. 1980 M 63 280 M 23 Jan. 1980 24 Mar. 1980'^ M 61 380 M 23 Jan. 1980 21 Mar. 1980 M 58 480 M 27 Jan. 1980 8 Mar. 1980 U 41 181 F 7 Jan. 1981 11 Feb. 1981 u 36 281 M 9 Jan. 1981 20 Feb. 1981 u 43 381 F 9 Jan. 1981 27 Mar. 1981 M 78 481 M 11 Jan. 1981 27 Mar. 1981 M 76 581 F 15 Jan. 1981 25 Mar. 1981 U 70 881 M 15 Mar. 1981 21 Mar. 1981 ?*' 7 981 F 18 Mar. 1981 1 Apr. 1981 M 15

M = mated, U = unmated (see text). First departed on 22 March 1980, but eagle encountered a winter storm and returned to winter range. Undetermined. .

December 2002 Bald Eagle Vernal Migration 259

Table 2. Mean climatological values (±99% confidence southerly winds; similar to conditions noted by interval) which discriminated {P ^ 0.01) between days Bagg et al. (1950) for other birds. radio-tagged Bald Eagles initiated northward migration Although Bald Eagles are apparently sensitive to from their San Luis Valley, Colorado wintering area (De- local conditions when migration is initiated, they part) and days they did not (Remain). appear to be cognizant of little beyond their im- mediate environs. Eagle 280 departed the SLV on Tempera- 22 March 1980 and traveled 145 km north before TURE Percent Wind being stopped by severe snow squalls. He spent the Range Sky Speed night on a mountain pass and as the storm per- (°C) Clear (km/hr) sisted to the north the next day, he returned to his Depart {N = 11) 24 (5) 50 (26) 22 (5) winter range in the valley. He spent the remainder = 21)=* Remain {N 19 (4) 56 (20) 16 (5) of that day and part of the next in close association Randomly selected. with a female (distinctly larger eagle) and was observed to copulate during this period. He initiated migration again on 24 March, leaving the SLV for a radio-tagged eagle occurring in mid-February the season. and the last in early April (Table 1). Number of Migration Routes, Destination, and Navigation. days from the equinox that eagles departed was not In 1980, a relatively narrow migration corridor different between genders (Mann-Whitney U = through Colorado, Wyoming, and Montana was 16.50, P — 0.81). However, mated eagles departed used by three radio-tagged eagles (Fig. 2). Eagle the SLV closer to the equinox and later than un- 380 became sedentary in north-central Saskatche- mated eagles (Mann-Whitney U = 3.00, P = 0.03; wan after 15 d of migration, six of which were

Fig. 1). spent sitting out bad weather. After four days of Three climatological variables discriminated be- almost continual solitary soaring, he was found tween days that radio-tagged Bald Eagles left the perched close to a larger eagle where he remained SLV on migration and those they did not (Table for several hours. The next day the pair began con- 2). Eagles initiated migration on days with much struction of a new nest on Chachukew Lake, north larger range of temperatures, more clouds, and of Pelican Narrows, Saskatchewan. They eventually with higher winds than other days over the winter- fledged one young in August 1980. spring period. Migration tended to be initiated In 1981, eagle 281 left the SLV on 20 February, about 5 hr after sunrise regardless of the immedi- and was followed for two days over 302 km through ate meteorological condition. the mountains of western Colorado (Fig. 3) . Direc-

Photoperiodism is considered to be the ultimate tion was primarily northwest and 281 was the only stimulus for the onset of migration in birds (King eagle tracked that crossed the Continental Divide. and Earner 1963). All radio-tagged Bald Eagles de- Subsequent tracking of 281 was interrupted be- termined to be mated left the SLV within 12 days cause a radio of the same frequency and pulse rate of the vernal equinox, indicating breeding adults as 281 was tracked for a day before I discovered it may be sensitive to equal periods of light and dark. was a transmitter on a collar of a bighorn sheep

Unmated, nonbreeding, or immature eagles may ( Ovis canadensis) be equally sensitive but may not be driven by pres- Eagle 981 left the SLV on 1 April and was fol- sure to procreate. In fact, first observations of sub- lowed to about 65 km north of Casper, Wyoming, adult eagles in northern ranges both years were where she was lost in a snow storm because roads not until at least two weeks subsequent to the ar- became impassable. Eagle 481 was detected ap- rival of the first radio-tagged adults. Migrational proaching Fort Peck Reservoir in east-central Mon- movement also paralleled the northward move- tana on 5 April. After leaving Fort Peck Reservoir, ment of the 2°C isotherm (Lincoln 1979) both 481 flew due north about 35 km then gradually temporally and spatially, hinting that thermal cues shifted to a northwest course. This route took him may also be involved in the initiation of migration. directly to the Missouri Coteau, a ridge line run-

Once the urge is kindled, proximate affectors of ning longitudinally for over 150 km in southwest- Bald Eagle migration appear to be coincident with ern Saskatchewan. He continued north along the incoming low pressure systems, associated wide Coteau for about 100 km. Approaching the Cana- range of temperatures, cyclonic air flows, and dian Shield, 481 made a sudden change in course 260 Harmata VoL. 36, No. 4

Figure 3. Partial migration routes of radio-tagged adult Figure 2. Partial migration routes of radio-tagged adult Bald Eagles from winter ranges in the San Luis Valley Bald Eagles from winter ranges in the San Luis Valley, (SLV), Colorado in 1981. Numbers indicate eagle desig- Colorado in 1978 and 1980. Numbers indicate eagle des- nation (Table 1). Summering areas are indicated by ignation and year (Table 1). Summering area of eagle 0 (nest locations). Respective 1981 and 1982 recovery lo- 380 is indicated by 0 (confirmed nest location). cations of Bald Eagles banded in the SLV (January 1977)

are indicated by (x). Tbe October 1981 recovery location of a Bald Eagle radio-tagged in the SLV in March 1981 from north to northeast, paralleling the direction is indicated by 781. of many elongated lakes and rivers in the Canadian Shield country. Eagle 481 was subsequently followed to Reindeer Lake, Saskatchewan, arriving on malfunction, a dead eagle, or a bird in incubation 10 April. On 22 April, 481 was found by air asso- posture. Lack of contact with other SLV eagles may ciated with a nest site on Ramuchawie Lake in west- have been a function of transmitter failure (one ern Manitoba near the Saskatchewan border (Fig. was known to fail in the SLV) premature shedding , 3). of the transmitter (one transmitter was found still Aerial surveys covering ca. 210000 km^ of north- attached to broken tail feathers below a perch tree signals in mortality, incomplete survey coverage, ern Saskatchewan were conducted to detect the SLV) , of other SLV Bald Eagles in mid- to late April in or summering areas were located outside of north- both 1980 and 1981. During aerial surveys, eagle ern Saskatchewan. However, the fact that 31% of 181 was located on the Pagato River, south of Rein- potentially-detectable eagles (N= 13) were located deer Lake, Saskatchewan, and eagle 581 was de- within an area roughly the size of Yellowstone Na- tected briefly in the area of Trade Lake, south of tional Park (ca. 9300 km^) suggests that most adult the Churchill River (Fig. 3). The signal was weak Bald Eagles wintering in the SLV originated from and intermittent, which indicated either a radio this area of Canada. .

December 2002 Bald Eagle Vernal Migration 261

Mean distance (as the eagle flies) from the SLV the remainder of migration clearly compensated wintering area to breeding or summer areas of for the one day blown off course (Fig. 2). Unless

Bald Eagles was 2019 km {N - 4, SD = 50). All tbe eagle had been exposed to the area on previ- eagles located on their summer ranges were within ous migrations, true navigation is indicated. How-

102 km of each other in northeastern Saskatche- ever, it is not unreasonable to assume that an adult wan or northwestern Manitoba (Figs. 2 and 3). Du- eagle over five years old, may indeed be familiar ration of travel between winter and summer range with a great portion of western North America as for SLV Bald Eagles with known departure and ar- a result of vagaries of previous migrations. Regard- rival dates {N = 2) was 15 d. Although SLV Bald less, redundancy in navigational systems has been Eagles traveled about Vs the distance to their sum- illustrated for homing pigeons (Columba livia) mer ranges compared to one Bald Eagle tracked (Able 1980) and in all probability, several backup by satellite from Arizona to the Northwest Terri- navigational systems are available to Bald Eagles, tories (3032 km, Grubb et al. 1994), they complet- especially experienced adults. ed the journey in only about 40% of the time. Migration Behavior. Mated adult Bald Eagles ap- However, the Arizona eagle was a subadult (3rd yr) parently migrated alone in the spring. Eagle 380 and presumably was not driven by the impetus to was seen roosting solitarily at all but one stopover nest, as were adult SLV eagles tracked. location (six other eagles on the Yellowstone River Geography, celestial cues, and weather may all near Hysham, Montana). Eagle 481 did not mi- play a role during migration of Bald Eagles. Prom- grate with a mate, but often moved northward with inent physiographic features such as deep canyons, other adult eagles. He roosted with other eagles rivers, and north-south oriented topography three times, but two sites obviously were not com- seemed to assist in visual navigation during flight munal or traditional because of lack of similarity (Griffin 1943). These features could have been im- to typical Bald Eagle roost sites (Kiester and An- printed in the memory of eagles during their ini- thony 1983). Paired roosting was probably a result tial migrations and experience dictated direction of facilitatory behavior influenced by poor weather during subsequent flights (kinesis theory; Mat- and lack of daylight remaining. Subsequent obser- thews 1963). Imprinting of migration routes from vations of migration flight confirmed he moved wintering areas, which compliment survival during alone. Once in the boreal forest of the Canadian the first year, would be more adaptive than im- Shield country, local eagles appeared to “meet” printing during first southward migration. him in flight and escort him through their terri- Eagles did not migrate on days of total overcast, tories, but no overt agonistic encounters were ob- a phenomenon also noted by Gerrard and Gerrard served. Occasional associations with other eagles (1982). The altitude of the cloud layer may have appeared incidental for all radio-tagged eagles and an effect, but overcast layers over 90 m were not were of short duration. Solitary migration behavior experienced during tracking. Sun compass orien- in established pairs would reduce the possibility of tation (Kramer 1952, 1957) with time compensa- both members being lost in a local catastrophe. tion, commonly referred to as sun-azimuth orien- Daily migration flights consistently began be- tation (Welty 1982) may, therefore, be important tween 1015-1045 H MST and ended between for orientation of adult Bald Eagles during migra- 1715-1745 H. Mean daily movement was 180 km, tion. but ranged from 144-435 km {N = 5) in 1980 and True navigation (selection of a compass direc- 33-248 km (A = 5) in 1981. Speed of migration tion toward a known goal in unfamiliar territory; flights recorded averaged 50 km/hr (A = 7, 22- Able 1980) may also be a component of Bald Eagle 144 km/hr in 1980; A = 9, 20-105 km/hr in 1981) migration. Migrating eagles appear to avoid strong Altitude of flights recorded ranged from 30-4572 winds during migration because strong winds ap- m AGL, but most often was between 1500-3050 m. parently influence direction of flight. Eagles did Total distances, speed, and daily duration of mi- not move, except locally, during days when winds gratory flights indicate that under optimal weather in excess of 35 km/hr occurred prior to 0900 H. conditions. Bald Eagles can reach their breeding East winds of 60—80 km/hr began about two hours grounds within 6 d after leaving the SLV. Penny- after initiation of eagle 380’s flight on one migra- cuick (1975) indicated a 2000 km migration for a tion day and his flight path deviated well west of bird the size of a Bald Eagle would be near maxi- direct line to the eventual goal. Flight direction for mum attainable without eating, assuming a 25% .

262 Harmata VoL. 36, No. 4

mass loss. During this study, no radio-tagged eagles Stopover areas used during vernal migration of were observed feeding during migration and mean SLV Bald Eagles were generally widely distributed. migration distance was 2020 km. Captive eagles A tree of adequate size, secure from human dis- commonly fast more than two weeks with no ap- turbance in any type habitat, was all that seemed parent deleterious effects (Brown and Amadon necessary for roosting. In late March 1982, Swen- 1968, pers. observ.) and wild raptors can lose up son (1983) counted 232 Bald Eagles along the Yel- to 30% of body mass without problems (Newton lowstone River between the mouth of the Bighorn 1979). These compensatory capacities undoubted- River and Miles City, Montana. A site where eagle ly allowed adult Bald Eagles to reach their breed- 380 roosted is in the middle of this stretch and ing grounds with sufficient energy reserve for within an area where the river seldom freezes, con- breeding. tained the most highly braided portion of channel, All radio-tagged eagles arrived in their summer most heavily wooded islands, and highest Canada range at a time when lakes and most stretches of goose {Branta canadensis) populations of three sec- rivers were still frozen. The only areas of open wa- tions of river studied by Hinz (1974). Use of this ter were rapids or narrows on rivers or between section of the Yellowstone River by adults may be lakes. Radio-tagged eagles spent most of their time dictated primarily by tradition and availability of there, presumably foraging for fish. Other eagles water, because migrating adults were not known to observed during aerial surveys were associated with feed during this study. ubiquitous holes in lake ice and viscera piles of fish Areas in eastern Montana may be equally im- left by native commercial fishing operations. For- portant to as many or more migrating eagles as the aging eagles were also seen on or near caribou more highly-publicized areas, where ephemeral {Rangifer tarandus) and moose {Alces alces) carcass- concentrations of eagles occur in western Mon- es killed by natives or wolves ( Canis lupus) A few tana. Leighton et al. (1979) estimated a population eagles were seen with snowshoe hare {Lepus amer- of 14 000 Bald Eagles in Saskatchewan. Some ea- tcanus) remains. gles from north-central Saskatchewan were cap-

Regional Relationships. McClelland et al. (1994) tured in autumn at Hauser Lake (Restani et al. noted that Bald Eagles radio-tagged in Glacier Na- 2000) and Glacier National Park (McClelland et al. tional Park, Montana, in autumn wintered west of 1982), while others passed through eastern Mon- the Continental Divide and summered in the tana during migration (Gerrard et al. 1978, Har- MacKenzie River watershed of northern Alberta, mata et al. 1985). Both Hauser Lake and Glacier northwest Saskatchewan, and Northwest Territo- National Park Bald Eagle concentrations are now ries. The summer range of a Bald Eagle that win- defunct due to a collapsed, exotic food base (ko- tered in Arizona (west of the Divide) also was in kanee salmon, Oncorhynchus nerko), but eastern the MacKenzie River watershed (Grubb et al. Montana habitats still support large numbers of na-

1994). McClelland et al. (1994) suggested that win- tive prey (lagomorphs, ungulates, waterfowl). How- tering areas may be related to the watershed of ever, lack of a concentrated food base, diffusion of origin and Bald Eagles be managed by application roost sites, solitary habits of migrating eagles, plus of a “Migration Flyway Concept.” Adult Bald Ea- dispersion of departure dates from winter (this gles radio-tagged and banded in the SLV wintering study) and summer ranges (Harmata et al. 1985), area (east of the Divide) were tracked to breeding prohibit any accurate estimate of numbers of Bald areas in Saskatchewan and Manitoba, all in the Eagles passing through eastern Montana. Relatively

Churchill River watershed. Jenkins et al. (1982) follow numbers of eagles present at any particular lowed two adult Bald Eagles radio-tagged in Wyo- time at some stopover areas in eastern Montana ming during winter. One trapped on the west side may belie the true importance of these areas to of the Continental Divide was followed to the migrating eagles. Turnover of individuals appeared MacKenzie River watershed, while one trapped on to be daily, over months. Therefore, western prai- the east side of the Divide was followed to the rie states may provide important migratory habitat Churchill River watershed, similar to those from for a large proportion of the continental popula- the SLV. These data suggest a “Churchill-East tion of Bald Eagles over long periods. Slope” Migration Flyway exists, distinct from the Acknowledgments “Mackenzie-Intermountain” Flyway proposed by J. Stoddart initially suggested Bald Eagle research in McClelland et al. (1994). the SLV. Dale Stahlecker served as co-investigator during December 2002 Bai.d EACiLE Vernai, Migration 263

preliminary marking studies. P. Harmata (then age 5) Bald Eagles Haliaeelus leucocephalus from Arizona and helped track the first migrating Bald Eagle in 1978. G. Michigan with satellite telemetry. Pages 347-358 m Montopoli was instrumental for successful completion of B.-U. Meyburg and R.D. Chancellor [Eds.], Raptor the first year’s migration tracking. M. Lockhart provided conservation today. World Working Group on Birds details of eagle capture techniques and field assistance. of Prey. Pica Press, London, U.K. S. Werner and E. Spettigue participated in winter and Harmata, A.R. 1984. Bald Eagles of the San laris Valley, migration tracking. L. Stevenson of Pelican Narrows, Sas- katchewan, donated flight expertise and air time. Finan- Colorado; their winter ecology and spring migration. cial assistance was provided by R. Koteen; Fred Jense, Ph.D. dissertation, Montana State University, Boze-

Dept, of Veteran’s Affairs; J. Lincer and W. Clark of the man, MT U.S.A. National Wildlife Federation; R. Plunkett of the National , J.E. Toepfer, and J.M. Gerrard. 1985. Fall mi- Audubon Society; D. Flath of Montana Fish, Wildlife, and gration of Bald Eagles produced in northern Sas- Parks; 1.. Jahn of the Wildlife Management Institute and katchewan. Blue Jay 43:56-62. American Petroleum Institute; T. Ingram of Eagle Valley AND D.W. Stahlecker. 1993. Fidelity of Bald Environmentalists; S. Rainey and C. Merrit of American Eagles to wintering grounds in southern Colorado Wilderness Alliance; M. Malone, Montana State Univer- and northern New Mexico. /. Field Ornithol. 64:129- sity (MSU) Research Creativity Program; R. Eng, MSU Agricultural Experiment Station; and R. Moore, MSU Bi- 134. ology Department. T. Crubb, M. Ratine, M. Restani, and Hinz, T.C. 1974. Seasonal activity, numbers and distri- D. Stahlecker made helpful comments on earlier drafts bution of Canada Geese {Branta canadensis) in the of the manuscript. “Sarge” was the dog, a great compan- lower Yellowstone Valley, Montana. M.S. thesis, Mon- ion and a loyal friend. tana State University, Bozeman, MT U.S.A.

Jenkins, M.A., T.P. McEneaney, I.. Hanebury, and J.R Literature Cited Squires. 1982. Bald Eagle (Ffaliaeetus leucocephalus) es-

Able, K.P. 1980. Mechanisms of orientation, navigation sential habitat on and near Bureau of Land Manage- lands Draft final and homing. Pages 284-373 in S.A. Gauthreaux, Jr. ment in Wyoming. report—FY 1981 [Ed.], Animal migration, orientation and navigation. & 1982. Wintering Bald Eagles. U.S. Dept, of Interior, Academic Press, New York, NY U.S.A. Fish & Wildl. Service, Denver, CO U.S.A.

Bagg, A.M., W.W.EI. Gunn, D.S. Miller, J.T. Nichols, W. Kiesier, G.P., Jr. and R.G. Anthony. 1983. Characteris- Smith, and F.P. Wolforth. 1950. Barometric pres- tics of Bald Eagle communal roosts in the Klamath Basin, Oregon and California. Wildl. Manage. 47 sure—patterns and spring bird migration. Wilson Bull. J. 62:5-19. 1072-1079.

Brodeur, S., R. Deecarie, D.M. Bird, and M. Fuller. King, J.R. and D.S. Earner. 1963. The relationship of fat 1996. Complete migration cycle of Golden Eagles deposition to Zugunruhe. Condor 65:200—223. breeding in northern Quebec. Contfor 98:29.3-299. Kramer, G. 1952. Experiments on bird orientation. Ibis Brown, L.H. and D. Amadon. 1968. Eagles, hawks, and 94:265-285.

falcons of the world. Vol. 2. McGraw-Hill Book Co., . 1957. Experiments on bird orientation and their New York, NY U.S.A. interpretation. Ibis 99:196-227. Craig, J.R. 1981. Bald and Golden Eagle winter popula- Leighton, F.A., J.M. Gerrard, P. Gerrard, D.W.A. Whit- tion surveys. Wildlife Research Report: Part I. Federal field, and W.J. Maher. 1979. An aerial census of Bald Aid Job Final Report. Colorado Division of Wildlife, Eagles in Saskatchewan./. Wildl. Manage. 43:61-69. Denver, CO U.S.A. Linc:oln, F.C. 1979. Migration of birds. In S.R. Peterson Dixon, W.J. 1981. BMDP. Statistical Software. Univ. of and P.A. Anastasi [E.DS.], Fish & Wildlife Service Cir- California Press, Berkeley, CA U.S.A. cular 1 6. U.S. Dept, of Interior, Washington, DC Garcei.on, D.K., M.S. Martell, P.T. Redig, and L.C. U.S.A. Buoen. 1985. Morphometric, karyotypic, and laparo- Matthews, G.V.T. 1963. The orientation of pigeons as scopic techniques for determining sex in Bald Eagles. affected by the learning of landmarks and by the distance of displacement. Anim. Behav. 11:310—317. J. Wildl. Manage. 49:595-599. Gerrard, J.M., D.W.A. Whitfield, P. Gerrard, P.N. Ger- McCleeland, B.R., L.S. Young, D.S. Shea, P.T. Mc- RARD, AND WJ. Maher. 1978. Migratory movements Cleliand, H.L. Ai.len, and E.B. Spettigue. 1982. The and plumage of subadult Saskatchewan Bald Eagles. Bald Eagle concentration in Glacier National Park, Can. Field-Nat. 92:37.5-382. Montana: origin, growth and variation in numbers. and P.N. Gerrard. 1982. The spring migration of Living Bird 19:133—15.5.

Bald Eagles in the vicinity of Saskatoon. Blue Jay 40: , L.S. Young, P.T. McClelland, J.G. Crenshaw, 56-60. H.I.. Allen, and D.S. Shea. 1994. Migration ecology Griffin, D.R. 1943. Homing experiments with Herring of Bald Eagles from autumn concentrations in Glacier Gulls and Common Terns. Bird-banding 14:7-23. National Park, Montana. Wildl. Monogr. 125. Grubb, T.G., W.W. Bowerman, and P.W. Howey. 1994. Meyburg, B-U., D.H. Ellis, C. Meyburg, J.M, Mendel-

Tracking local and seasonal movements of wintering son, and W. Scheller. 2001 . Satellite tracking of two 264 Harmata VoL. 36, No. 4

Lesser Spotted Eagles, Aquila pomarina, migrating gles exploiting a seasonally concentrated food source. from Namibia. Ostrich 72:35-40. Wilson Bull. 102:561-568. Miner, N.R. 1975. Montana Golden Eagle removal and Ryder, R.A. 1965. A checklist of the birds of the Rio translocation project. Pages 155-162 in Proc. of the Grande drainage of southern Colorado. Colorado Second Great Plains Wildlife Damage Control Work- State Univ. Press, Ft. Collins, CO U.S.A. Swenson, 1983. Is the northern interior Bald Eagle shop. U.S. Fish & Wildlife Service, Denver, CO U.S.A. J.E. population in North America increasing? Pages 23- Newton, I. 1979. Population ecology of raptors. Buteo 34 in D.M. Bird, Biology and management of Bald Books, Vermillion, SD U.S.A. Eagles and Ospreys. Harpell Press, Ste. Anne de Belle- Pfnnycuick, C.J. 1975. Mechanics of flight. Pages 1-75 in vue, Quebec, Canada. D.S. Earner and J.R. Bang [Eds.], Avian biology. Vol. Welty, J.C. 1982- The life of birds, 3rd Ed. W.B. Saunders V. Academic Press, New York, NY U.S.A. Co., Philadelphia, PA U.S.A. Restani, M., A.R. Harmata, and E.M. Madden. 2000. Nu- merical and functional responses of migrant Bald Ea- Received 21 December 2001; accepted 6 July 2002 —

Sean P. Finn^ Biology Department, Boise State University, 1910 University Drive, Boise, ID 83725 US.A.

Daniel E. Varland^ Rayonier, 3033 Ingram Street, Hoquiam, WA 98550 US. A.

John M. Marzluff College ofForest Resources, University of Washington, Box 352100, Seattle, WA 98195 US.A.

Abstract.—To determine stand-level habitat relationships of Northern Goshawks (Accipiter gentilis) on Washington’s Olympic Peninsula, we surveyed all known historically-occupied sites {N = 30) for occupancy. We measured 45 forest-stand attributes at these sites and found, using stepwise logistic regression, that goshawks were most likely to occupy historical nest sites with high overstory depth (maximum overstory height-minimum overstory height) and low shrub cover. Forest managers can manage for high overstory depth (>25 m) and low shrub cover (<20%) by conducting a single, moderate-level thinning (leaving 345-445 trees/ha) in young, even-aged 30-35-yr-old stands. Overstory canopy and shrub cover conditions should improve over a 5—10 yr period following thinning. Values for some habitat

features (i.e., percent shrub cover, percent canopy closure, and total snags/ha) in our study were near or within the range of values reported for Spotted Owls {Strix occidentalis) in young forests on the Olympic Peninsula. Thus, forest management recommendations described herein may also benefit Spotted Owls.

Key Words: Northern Goshawk, Accipiter gentilis; logistic regression-, overstory depth, shrub cover, Washington-, wildlife habitat relationships, silviculture, thinning, forestry.

VARIA LA OCUPACION REPRODUCTIVA DEL AZOR CON LAS CARACTERISTICAS DEL SITIO— NIDO EN LA PENINSULA OLYMPIC, WASHINGTON?

Resumen. Para determinar las interrelaciones del habitat a nivel del sitio-nido para el Azor {Accipiter gentilis) en la peninsula Olympic de Washington, estudiamos todos los sitios ocupados conocidos his-

toricamente {N = 30) . Medimos 45 atributos de los sitios en bosques y encontramos, usando regresion logistica paso a paso, que estos azores probablemente ocuparon historicamente sitios nido con cubierta densa (maxima altura de la cubierta-minima altura de la cubierta) y baja cobertura arbustiva. Los administradores de bosques puedan manejar cubiertas densamente altas (^25 m) y baja cobertura arbustiva (<20%) llevando un simple, y moderado nivel de entresaca (dejando 345—445 arboles/ha) en plataformas jovenes, o incluso de edades entre 30-35 ahos. La cubierta del dosel y las condiciones de la cobertura arbustiva deben mejorar en un periodo de 5-10 ahos despues de la entresaca. Los valores para algunas caracteristicas de habitat (v.gr. Porcentaje de cobertura arbustiva, porcentaje de cerra- miento del dosel, y total de tocones/ha) en nuestro estudio estuvieron cerca o dentro del rango de los valores reportados para Strix occidentalis en bosques jovenes de la peninsula Olympic. De esta manera las recomendaciones para el manejo de los bosques que se dan aqui, pueden beneficiar ademas a los buhos. [Traduccion de Cesar Marquez]

Of critical importance to the success of an or- tion among available resources may be especially ganism is its selection and use of resources. Selec- important in large mobile organisms that rapidly move through extensive areas and sample available ^ Current address: USGS, Forest and Rangeland Ecosys- resources at a relatively coarse grain (Stern 1998). tem Science Center, Snake River Field Station, 970 Lusk Large mobile organisms living in structurally-com- Street, Boise, ID 83706 U.S.A. particularly ^ Corresponding author’s e-mail address: daniel.varland® plex habitats may be responsive to rayonier.com changing conditions because the various compo-

265 . ,

266 Finn et al. VoL. 36, No. 4 nents of their habitat may singly or interactively SruDY Area affect their preferred breeding sites, thermal en- The peninsula is composed of a central core of rugged mountains by level, forested vironment, prey abundance and distribution, vul- surrounded more lowlands. Elevation ranges from 0-2420 m, although all known gos- nerability to predators, or their competitive status hawk nests were restricted to elevations ranging from ca. (Hilden 1965, Patton 1997). The Northern Gos- 150-810 m. Mixed coniferous forest is the dominant veg- hawk {Accipiter gentilis; hereafter known as gos- etation over most of the peninsula although tree species, hawk) is an excellent example of such an organ- age, and composition vary along a west-east moisture gradient and from natural and anthropogenic disturbances ism. Goshawks inhabit boreal and temperate (Franklin and Dyrness 1988, Agee 1993). Western slopes forests within the Holarctic region (Squires and are dominated by Sitka spruce {Picea sitchensis) western Reynolds 1997). Because they are highly mobile, hemlock ( Tsuga heterophylla) , and western redcedar ( Thu- long-lived, and can take a broad assortment of prey ja plicata) whereas the central and eastern portions contain pure or mixed stands of western hemlock and Doug- (Squires and Reynolds 1997, Watson et al. 1998), las-fir (Pseudotsuga menziesii) along with western redcedar they are able to select among many different avail- , and Pacific silver fir {Abies amabilis). Riparian and re- able habitats for breeding, roosting, foraging, and cently-disturbed areas usually contain stands of red alder other activities. {Alnus rubra), which may also grow in the understory or Much research has focused on goshawk habitat in tree gaps on older upland sites. Understory and shrub- layer densities vary widely and contain western hemlock, use and requirements (Block et al. 1994, Squires red alder, Pacific rhododendron {Rhododendron macro- and Reynolds primarily in response to con- 1997), phyllum), sword fern {Polystichum munitum), and salal cerns over habitat alteration (DeStefano 1998) and ( Gaullheria shallon) potential population declines (Crocker-Bedford Vegetation on the Olympic Peninsula is influenced greatly by the management strategies of the four princi- 1998). Goshawks are described as forest generalists pal landowners, resulting in a mixture of forest stands of at large spatial scales, but are a species with nar- varied serai stages. The Olympic National Park (ONP, habitat nest sites rower requirements at (Squires 365 000 ha, Holthausen et al. 1995) does not engage in and Reynolds 1997). At the nest-stand scale, re- commercial timber harvest. Under the Northwest Forest search has shown that goshawks select stands with Plan, the ONP is classified as Congressionally Withdrawn (USDA and USDI 1994). The oiympic National Forest large-diameter trees and high canopy closure, re- (ONF, 254 000 ha) is managed under the Northwest For- gardless of forest type or region (DeStefano 1998). est Plan for multiple uses (USDA and USDI 1994) in To evaluate relationships between extant habitat which forest management now occurs at low levels in lim- and goshawk site-occupancy, we measured 45 forest ited areas. Forest management on lands managed by the Washington Department of Natural Resources (DNR, characteristics in nest stands at 30 historical sites 164 000 ha) is guided to a significant extent by a Habitat (Table 1); 29 sites were on the Olympic Peninsula Conservation Plan (Washington State Department of and one was just south of this location (Fig. 1). Natural Resources 1997). However, the focus on these Hereafter, because of the proximity of this site to lands and on private forest lands (347 000 ha) is on com-

the peninsula, all sites are referred to as Olympic mercial timber production and forest management. For- est cover conditions on the ca. 1.2 million ha of the Peninsula sites. Olympic Peninsula may be summarized by the percent objectives were to: estimate current oc- Our (1) of total area of each ownership class in nesting, roosting cupancy and breeding rates at all historically oc- or foraging habitat for the Spotted Owl {Strix occidentalis) cupied goshawk nest sites on the Olympic Penin- as defined by Holthausen et al. 1995: ONP—46%, ONF = 38%, DNR = 20%, and private/other non-federal = sula, (2) describe the relationship between 7%. goshawk nest-stand occupancy and nest habitat attributes (see Finn et al. 2002 for descriptions at MRtJIODS scales), larger spatial and (3) offer management Occupancy at historical nest sites is an important mea- recommendations based on our findings. We hy- sure of habitat suitability because goshawks usually exhib- pothesized that the 30 historical nest sites we iden- it high site fidelity (Crocker-Bedford 1990, Woodbridge and Detrich 1994, Squires and Reynolds 1997). We mea- tified for study would still be occupied during our sured stand attributes at historical nest sites and avoided study if forest conditions at these sites had not measures at random locations to eliminate the inherent been degraded since they were first discovered. We bias of most use-availability studies that statistically test reasoned that habitat degradation at nest sites what is already known; that animals are nonrandomly distributed in the environment (Cherry would result in sites being unoccupied and that 1998, Johnson 1999). sites we found to be occupied would more closely Occupancy Surveys. We defined 30 goshawk location resemble forest conditions at historical sites when records as historical nest sites after reviewing all sight re- they were used by goshawks. cords in state and federal databases. All historical nest 6 1 2

December 2002 Goshawk Nest-stand Habitat 267

Table 1. Northern Goshawk survey effort at 30 historical nest sites (170 or 314 ha) on the Olympic Peninsula, Washington, 1996-98. In 1996, a 170 ha area was surveyed around each site and in 1997-98, a 314 ha area was surveyed.

1996 1997 1998 No. OF Visits No. OF Visits No. of Visits

Site Name/ Sta- Court- Nest- Fledg- To- Court- Nest- Fledg- To- Court- Nest- Fledg- To- Number® TUS SHIP ling ling tal^ ship ling ling tal^ ship ling ling tal’’

Calawah/ Sitkum/ 1 O 2 2 1 5 2 2 1 5 3 1 4 Raney Creek/29 O 1 2 1 4 1 1 2 1 3 2 6

Dungeoness/16 1 1 1 1 1 3 1 1 2 Burnt Mountain/2 O 3 7 1 11 3 2 1 6 1 1 2 The Hole/30 O 1 6 1 8 3 3 1 7 1 1 2 Donkey Creek/26 O 1 6 1 8 3 2 2 7 1 2 1 4 Snow Creek/ 18 U 2 2 4 3 1 4 1 2 1 4 Morganroth Flat/20 u 1 2 1 4 1 3 1 5 2 2 4 Swede Road/4 u 1 3 1 5 3 1 4 3 1 4 Bear Creek/3 u 2 1 1 4 3 1 4 1 2 1 4 N Fork Solduc/7 o 1 1 2 Mount Zion/ 14 o 1 1 2 Wolf Creek/ 11 o 2 2 4 West Twin River/ u 3 1 4 Dosewallips/24 u 3 1 4 Cook Reload/28 u 3 1 4 Wildcat Mountain/5 u 3 1 4 Bear Mountain/ 13 u 2 2 4 Boulder Creek/9 u 3 1 4 Iverson/ u 2 2 4 Bowman Creek/ 19 o 2 2 4 Antelope Creek/ 15 o 2 2 4 Lillian River/ 17 o 1 1 2 Snahapish River/ 25 u 1 2 1 4 Big Canyon/23 u 2 2 4 Palo Alto/ 10 u 2 2 4 Bingham Creek/27 u 2 2 4 Caraco Creek/8 u 2 2 4 Dry Creek/21 u 1 1 2 4 Minnie Peterson/22 u 2 2 4

“ See Fig. 1 for location by site number.

’’ Minimum of four visits required to meet protocol. Where <4 visits shown, occupancy was determined before protocol was met In 1996, occupancy determination was made early in nesting season by Watson (Watson et al. 1998).

sites: (1) were in the Washington Heritage Database, first the UTM coordinates on record for that nest site. Be- located between 1976-94; (2) were occupied by at least cause goshawks are highly mobile and tend to be secre- one goshawk when reported; and (3) contained a large tive, we considered a historical nest site to be occupied stick nest at the time of the goshawk sighting. Annual if at least one goshawk was visually detected within 1 km data on goshawk occupancy were unavailable for all of of a nest during >1 survey visit (Finn 2000). these sites, so no historical analyses were possible. We The protocol survey involved 4-1 1 survey vi.sits where surveyed each historical nest site for goshawk occupancy calls were broadcast from each station once during nest- using standardized aural broadcast surveys (Kennedy and ing, with 1-2 of these survey visits during the fledgling Stahlecker 1993, Joy et al. 1994, Finn et al. 2002). We stage (Table 1). Call stations were 300 m apart along tran- surveyed a minimum of a 1 70-ha circle surrounding 10 sects that were 260 m apart. Call stations on adjacent historical nest sites in 1996 and a 314-ha circle (1 km transects were offset by 130 m. If occupancy was deter- radius) surrounding 20 historical nest sites in 1997-98. mined during a survey visit, protocol surveys were dis- The survey area was centered on the most recently used continued but one additional site visit was made during nest structure or, when no nest structure was found, on the fledgling stage to count the number of young 268 Finn et al. VoL. 36, No. 4

* JO • ^9 20 * 1 « ^'2 23^ 26^ 18 ^ Olympic 24 ,28 3^ ^21 A 7 * 22 8 17 Olympic Nation^ 29 30

National IS

14 Park 16

Pacific Forest Ocean

* 6 2S

Nest Survey Years

1996 - 1998

• 1997

^ 1998

•••*

i ‘i 0 ^3

Figure 1. Location of 30 historical goshawk nest sites (170 or 314 ha) on the Olympic Peninsula, Washington. Goshawk sites outside Olympic National Park and Olympic National Forest were located on land managed by the Washington Department of Natural Resources or owned by industrial timber companies. Numbers shown are historical nest site numbers; these correspond to those identified by site name in Table 1. All historical sites were first discovered by happenstance, 1976-94. Each site was surveyed for goshawk occupancy in 1996-98, with 10 sites receiving 3 yr of surveys and 20 receiving 1 yr. .

December 2002 Goshawk Nest-stand Habitat 269 fledged. With one exception, where another research size classes. We also recorded species, DBH, total height, group checked on nest status (Dungeoness site in 1996; crown ratio, crown class, and level of mistletoe infection Table 1), all known nests were checked for signs of oc- for each tree. Quadratic mean diameter at breast height cupancy on 2-6 occasions (dependent on nest condition) (QDBH) was calculated as ((S DBH'^)/n)*^ We used a during the nesting season. clinometer to estimate tree heights. Crown ratio, crown Because goshawk occupation of historical sites can vary class, and mistletoe abundance were estimated visually over time (DeStefano et al. 1994, Keane and Morrison for eacb tree in the variable plot and then averaged for 1994), we surveyed 10 historical nest sites all three years. the plot. A sample of 1-3 trees of each species on each This provided an assessment of among-year site occupan- plot was cored for age and 10-yr radial growth rate. Over- cy. Seventy percent of the sites maintained the same oc- story and understory canopy characteristics (i.e., oversto- cupancy status among any pairing of years, indicating ry canopy closure, and maximum and minimum oversto- that goshawk occupancy was consistent among years sam- ry heights) were estimated by averaging four pled (Finn et al. 2002; Table 1). Therefore, we classified measurements recorded while facing the cardinal direc- all known historical nest sites on the peninsula as occu- tions. Overstory and understory canopy closure were e.s- pied if they were occupied Sil yr (N = 12) or not-occu- timated using a moosehorn (Robinson 1947). Overstory pied if they were not found occupied during any of the and understory height and depth were the mean of four three survey years {N = 18). ocular estimates of the height of live branching in the Classifying sites as “occupied” or “not-occupied” two canopy layers. We used field data to calculate stand based on one year of surveys leaves room for misclassifi- density index (SDI, Reineke 1933) and stem density of cation. Sites not occupied during the year of survey may overstory (38.2-150 cm DBH) and understory (2.5-38.1 in fact have been occupied earlier or later when no sur- cm DBH) trees for each nest stand. All variables were veys occurred. To address this problem we set a = 0.10 averaged per plot, then per stand. as the upper limit for significant differences between oc- Seedling and sapling densities were measured on a cupied and not-occupied sites to counter the possibility fixed-radius plot where all trees <12.7 cm in diameter that variances were higher in our not-occupied group of were tallied and grouped by 2.5-cm diameter class. Mean stands because of misclassification. In addition, the man- values of height, crown ratio, crown class, and mistletoe agement recommendations we provide focus on the at- infection were calculated for each diameter class. We es- tributes of occupied sites rather than on differences be- timated density and height of shrub and herb layers, and tween occupied and not-occupied sites. coarse woody debris (CWD) characteristics on eight 1-m^ Habitat Analysis. To assess nest-stand habitat we mea- (Daubenmire 1959), nested plots. Plant association was sured vegetation characteristics at 30 historical nest sites. assigned to all vegetation plots following Henderson et We defined the nest stand as the homogeneous forest al. (1989). patch surrounding a goshawk nest and delineated stands Statistical Analysis. In our study, the number of pre- by scribing boundaries along ecotones and topographic dictor variables, 45, exceeded the experimental units, 30 features surrounding the nest after examining 1:12 000 Therefore, we first examined the relative differences between occupied not-occupied nest sites for var- orthophotographs, 1:16 000 aerial photographs, and 1: and each 24 000 topographic maps. Boundaries were ground- iable using box-and-whisker plots (Johnson 1999). We used this approach because simultaneous univariate tests truthed in the field. Historical nest stands averaged 51,4 increase the Type I error rate (Rice ha in size (range = 9-146 ha). Areas within historical 1989) and because the in nest stands where habitat alteration occurred, after gos- extensive hypothesis testing inherent multiple univariate tests is inappropriate for exploratory analyses such hawk occupancy and before our study, were included in as undertook (Cherry 1999). eval- our measurements of nest-stand characteristics. Thus, we 1998, Johnson We uated the box-and-whisker plots and identified variables our habitat measurements reflect stand conditions at the with central tendencies that varied with occupancy. time of our surveys, not conditions when the historical We selected a subset of variables that: showed differences nest site was originally determined to be occupied by gos- (1) in central not-occupied hawks. tendency between occupied and sites, (2) had statistical integrity (approximate normal We measured 45 forest characteristics (Appendix 1) in distribution, low multicolinearity), had biological in- 9—13 0.04-ha, systematically placed, circular plots (x = (3) tegrity (accuracy of measurement, relevance to gos- 10.5 plots/stand, SE = 0.26) in each nest stand using a hawks), and forest managers could effectively man- modified USFS Region 6 Timber Stand Exam (USDA (4) age (i.e., overstory canopy closure can be managed, but Forest Service 1989) and methods described by Husch et percent slope cannot). The variables chosen were then al. (1972) and Avery and Burkhart (1983). From plot evaluated as predictors of goshawk historical nest site oc- center, two concentric plots were established: a variable- cupancy using stepwise logistic regression models (Hos- radius plot to sample trees >12.7 cm DBH (Diameter mer and Lemeshow 1989, PROC Logistic, SAS Inst. 1998) Breast Height, poletimber and sawtimber) and a fixed- to explain variation in the binomial-response variable radius plot to sample trees ^12.7 cm DBH (saplings and (occupied vs. not-occupied, a < 0.10). We compared a seedlings) main-effect model to models that included selected in- We estimated basal area, total stem density, and stem teraction terms to assess their significance. and snag density in six size classes (12.8-38.1, 38.2-63.5, 63.6-88.9, 90.0-114.3, 114.4-139.7, and >139.8 cm) from Results variable radius plots (sampled using a 40 basal area factor prism). We grouped snags into a single size class (^15.2 We surveyed 10 historical sites all 3 yr (1996-98) cm) because of the low number of snags in individual and 20 sites during 1 yr (N = 50 annual site-sur- 270 Finn et al. VoL, 36, No. 4

Stem Density Decadence

Figure 2. Habitat characteristics of goshawk nest stands (9—146 ha) at 30 historical nest sites on the Olympic Pen- insula, Washington. The historical sites associated with these stands were either not-occupied {N = 18, dark boxes) or occupied {N= 12, white boxes) by goshawks, 1996-98. Boxes depict the median score and 25% and 75% quartiles. Whiskers represent the 10th and 90th percentiles and black dots represent the 5th and 95th percentiles.

veys; Table 1 ) . We confirmed presence of goshawks western hemlock trees, usually in association with during 20 of these 50 site-surveys (40% occupancy other conifers and occasionally with a few red al- rate). At the 20 site-surveys where we observed gos- ders. hawks, we saw birds during >2 survey visits 75% {N Compared to not-occupied nest stands, occupied = 15) of the time. During the other five site-sur- nest stands tended to have deeper canopies (oc- veys that revealed occupancy, we observed an adult cupied median overstory depth = 28.9 m, not-oc- goshawk during one visit. In all five cases, the cupied median = 21.6 m; Fig. 2) and higher can- bird’s behavior suggested it occupied the area (i.e., opy closure (occupied median overstory canopy alarm vocalization or site tenacity during the ob- closure = 77.7%, not-occupied median = 71.3%; servation). We determined that 12 of the 30 his- Fig. 2). Occupied goshawk nest stands had more torical nest sites were occupied (Table 1 ) . All gos- large-diameter trees than did not-occupied nest hawk responses were detected <300 m from a stands (i.e., occupied overstory stem density me- historical nest site location. dian = 191.9/ha, not-occupied median = 121.5/ Stand size at historical nest sites was 9-146 ha (x ha; Fig. 2). Occupied nest stands generally con-

= 51.4, SE = 6.4). Occupied nest stands were tained more timber (i.e., occupied SDI median = smaller in size {x = 32.6 ha, SE = 5.5, range = 2204.8, not-occupied median = 1184.2; Fig. 2) and 11.6-69.3) than not-occupied nest stands {x = 63.9 had less shrub cover than did not-occupied stands ha, SE = 10.9, range = 8.7—146.2). Historical nest (occupied median == 15.6%, not-occupied median stands (N = 30) were composed of large {x = 57.3 = 36.9%; Fig. 2). cm DBH, SE = 2.4; x height = 40.8 m, SE = 1.0), Overstory canopy closure, overstory canopy mature (x= 120-yr-old, SE = 12.5) Douglas-fir and depth, overstory stem density, SDI, and percent December 2002 Goshawk Nest-stand Habitat 271

Canopy Characteristics Misc.

E 25

W 2

1 3 0 KS

• 15.0

T *5 12.5 5 r ^ 10.0 ;

7.5 tj zn 1 5.0 2.5 1 • £ 0.0

Unoccupied Occupied

Figure 2. Continued.

shrub cover met our variable selection criteria and 1996, Desimone 1997, McGrath 1997, Patla 1997). were tested as predictors of goshawk nest stand oc- These authors reported on the significance of over- cupancy. Two of these, overstory canopy depth and story canopy closure in the nest stand but we found percent shrub cover, were useful in distinguishing stand-wide overstory depth (maximum overstory between occupied and not-occupied nest stands. height-minimum overstory height) more valuable We found that the equation logit {occupancy) — in predicting goshawk nest-stand occupancy. Deep, — 2.91 + 0.163 {overstory depth) — 0.063 {percent dense forest canopy {x = 28.7 m, 95% GI = 24.8- shrub cover) significantly described (overstory 32.6) may provide thermal cover (Newton 1979), depth: Wald — 2.97, P = 0.043; percent shrub protection from rain, or cover protection from cover: Wald — 4.13, P = 0.039) and was an ad- predators (e.g.. Great Horned Owls {Bubo vir^ni- equate fit (Hosmer and Lemeshow’s goodness of anus\, Reynolds et al. 1982, Squires and Reynolds fit = 4.087, df = 8, P = 0.850) to the data on 1997). goshawk occupancy of historical stands (Fig. 3). On the Olympic Peninsula, occupied nest stands This model including only main effects fit the data typically had about 50% the shrub cover of not- better than did any main effects plus interaction occupied nest stands (Fig. 2). The odds of goshawk models appraised with log-likelihood ratio criteri- occupancy decreased by 47% for each 10% in- on. crease in percent shrub cover (based on the odds ratio from the logistic regression analysis). Fur- Discussion thermore, productive goshawk nest stands had Our research indicates that occupancy of gos- about half the shrub cover of occupied (10.6% vs. hawk nest stands does vary with nest-stand charac- 19.0%; Table 2). teristics. Our results agree with most other studies Most other goshawk habitat studies have not re- that report overstory canopy as an important fea- ported shrub density (Speiser and Bosakowski ture of goshawk habitat (Squires and Ruggiero 1987, Crocker-Bedford and Chaney 1988, Kennedy 272 Finn et al. VoL. 36, No. 4

Tree Girth Ground Cover

Figure 2. Continued.

1988, Siders and Kennedy 1996, Desimone 1997, McGrath 1997, Penteriani and Faivre 1997) or have

reported it as non-important in contributing to goshawk site occupancy (Hayward and Escano 1989, Squires and Ruggiero 1996, Patla 1997). DeStefano and McCloskey (1997), however, con- tend that the relative absence of goshawks from the

Oregon Coast Range is due to the dense understory conditions there, which, in turn, limit prey availability. Goshawks rarely forage near their nests (Beier and Drennan 1997), so the lack of shrub cover we found in nest stands may be unrelated to prey availability. We did not measure shrub cover beyond the nest stand scale, however. At landscape scales (177-ha post-fledging area, 1886-ha home range), goshawk nest stand occupancy was predicted by a high proportion (60-75%) of late serai forest (>70% canopy closure of conifer species with >10% of the canopy in trees >53 cm DBH) and Figure 3. The probability (p) of goshawks occupying a reduced landscape heterogeneity (Finn et al. historical nest site on the Olympic Peninsula, Washing- ton, increases with increasing overstory depth and de- 2002 ). creasing percent shrub cover at the nest stand scale (9— Our study may have bias because all nest sites 146 ha). were located opportunistically instead of as a result 1

December 2002 Goshawk Nest-stand Habitat 273

= = Table 2. Nest stand (9-146 ha) habitat characteristics of occupied {N 12) and productive {N 8) historical nest sites of the Northern Goshawk on the Olympic Peninsula, Washington, 1996-98.

Occupieda Productive'^

Variable‘s Mean SE 95% Cl Mean SE 95% Cl

Mean DBH (cm) 58.8 3.7 50.6-67.0 58.2 5.4 45.5-71.0 Quadratic mean DBH (cm) 64.0 4.3 54.5-73.5 63.6 6.3 48.7-78.6 Maximum DBH (cm) 134.2 14.7 102.0-166.4 139.4 21.9 87.7-191.2 Minimum DBH (cm) 17.4 1.1 15.1-19.7 18.0 1.5 14.4-21.6 Mean tree height (m) 43.0 1.7 39.2-46.8 43.1 2.2 37.8-48.3 Crown ratio (index) 5.1 0.2 4.6-5.6 5.0 0.3 4.2-5.7 Crown class (index) 3.1 0.1 3.0-3.2 3.0 0.1 2.9-3.2 Mistletoe (index) 2.5 0.6 1. 2-3.8 1.8 0.6 0.5-3. Radial growth (cm) 1.7 0.3 1.2-2.3 1.9 0.3 1. 1-2.6 Mean tree age (yr) 147.4 22.8 97.2-197.6 128.9 25.4 68.7-189.0 Maximum tree age (yr) 247.6 .33.0 175.1-320.1 229.2 37.0 141.7-316.7 Mean sapling DBH (cm) 5.3 0.7 3.9-6.7 5.1 1.0 2.7-7.4 Mean sapling height (m) 5.7 0.6 4.4-7.0 5.7 0.8 3.8-7.5 Overstory canopy closure (%) 78.4 2.9 72.1-84.7 79.0 4.1 69.3-88.8 Minimum overstory height (m) 18.6 0.9 16.6-20.6 19.9 1.0 17.6-22.2 Maximum overstory height (m) 47.3 2.0 42.9-51.7 47.0 2.7 40.6-53.4 Overstory depth (m) 28.7 1.8 24.8-32.6 27.1 2.3 21.7-32.4 Understory canopy closure (%) 13.7 3.7 5.6-21.8 13.9 5.1 1.8-26.0 Min. understory height (m) 4.6 0.9 2.7-6.5 5.8 1.0 3.2-S.3 Maxi, understory height (m) 16.5 1.1 14.1-18.9 16.6 1.5 13.1-20.2 Understory depth (m) 11.9 0.9 9.9-13.9 10.9 0.7 9.1-12.6 Percent shrub cover (%) 19.0 4.2 9.7-28.3 10.6 2.5 4.8-16.4 Mean shrub height (cm) 41.9 4.7 31.7-52.1 39.9 4.2 29.9-49.9 Percent herb cover (%) 36.5 3.2 29.5-43.5 5.0 4.2 25.1-44.9 Mean herb height (cm) 3.6 0.2 3.1-4.1 3.4 0.2 3.1-3.8 CWD cover (%) 11.0 1.3 8.1-13.9 12.7 1.5 9.0-16.3 CWD height (cm) 42.1 4.8 31.6-52.6 45.0 5.6 31.9-58.2 CWD length (m) 11.0 0.9 9.0-13.0 11.5 1.3 8.3-14.6 CWD DBH (cm) 40.6 3.6 32.7-48.5 41.2 5.1 29.2-53.2 Slope (%) 40.5 5.0 29.5-51.5 42.5 5.7 28.9-56.0 Aspect (degrees) 269.9 26.3 218.4-321.3 294.5 63.5 170.1-58.9 Basal area (m^/ha) 71.4 5.9 58.5-84.3 68.5 5.7 55.0-81.9 Sapling den. (No. /ha) 797.3 180.8 399.4-1195.2 831.3 259.3 218.1-1444.6 Small stem density (No. /ha) 286.6 41.9 194.4-378.8 297.2 63.8 146.3-448.1 Med. stem density (No. /ha) 151.0 22.5 101.6-200.4 146.4 23.4 91.2-201.7 Large stem density (No. /ha) 39.1 7.7 22.2-56.0 32.5 8.1 13.3-51.8 Ex.-large stem den. (No. /ha) 2.3 1.4 0.0-5.3 2.4 2.0 0.0-7.0 Understory stem den. (No./ha) 1083.9 219.8 600.0-1567.8 1128.5 320.9 369.6-1887.4 Overstory stem den. (No./ha) 192.5 21.9 144.2-240.8 181.3 22.6 127.9-234.8 Live stem density (No. /ha) 485.4 47.4 381.0-589.8 488.0 67.9 327.4-648.6 Stand density index 2136.0 223.1 1644.9-2627.1 2107.1 317.6 1355.9-2858.3 Tree species richness (No.) 3.2 0.4 2.2-4.2 3.1 0.5 1.9-4.3 Percent hardwood (%) 1.9 1.2 0.0-4.4 1.2 0.6 0.0-2.7 Snag density (No. /ha) 35.8 6.0 22.6-49.0 40.0 6.7 24.2-55.8 Seedling (No. /ha) 2031.0 657.8 583.3-3478.7 2671.5 911.8 515.1-4827.9

‘‘12 sites: eight productive (where ^1 young fledged) and four occupied with no productivity. Eight productive sites.

= See Appendix 1 for descriptions of habitat variables. 2

274 Finn et ai.. VoL. 36, No. 4

of systematic searches of the full range of goshawk to address nest stand level habitat needs tailor habitat (Squires and Reynolds 1997, Daw et al. stand size after the ranges reported here.

1998) . Our sample included all of the nests reliably Our research indicates that goshawk nest-stand reported on the Olympic Peninsula over an 18-yr habitat may be provided on the Olympic Peninsula period, 1976-94. Thus, though our sample is small, by managing stands to create deep overstory can- it IS likely adequate to represent goshawk habitat opies and low shrub cover (Table 2, Figs. 2 and 3). use by goshawks on the Olympic Peninsula. Fur- Long et al. (1983) and Bailey (1996) report that thermore, Daw et al. (1998) compared goshawk large crowns can be created in dominant and co- nest stand habitat in stands found opportunistically dominant trees by thinning stands at 20-50 yr of with those found by systematic searches in Oregon age. Thinning reduces crown competition, thereby and found no differences in two key habitat vari- enhancing crown development and tree diameter ables, large tree density and canopy cover. Their growth. Thinning, however, allows more light to sample of opportunistically-located nests included reach the forest floor which also promotes under- nests found by individuals searching for goshawk story growth (Hayes et al. 1997, Thysell and Carey nests with a preconceived notion of goshawk hab- 2000). Hayes et al. (1997) indicated that thinning itat preferences (i.e., searching likely habitat). to moderate densities facilitates crown develop- Nests in our study, however, were found by individ- ment but limits development of understory be- uals whose reasons for being in the held varied cause the canopy closes rapidly. greatly (i.e., hikers, Marbled Murrelet {Brachyram- To accelerate the development of deep overstory phus marmoratus) surveyors, foresters conducting canopies in young even-aged stands, we recom- timber cruises) and who, in nearly all cases, were mend that a single moderate-level thinning take focused on activities other than hnding goshawk place in stands 30-35 yr of age. On the Olympic nests. The Daw et al. (1998) study provides empir- Peninsula and elsewhere in western Washington ical evidence that the method we employed for and Oregon, moderate-level thinning would result identifying historic nest sites was adequate. in retention of 345—445 trees/ha where heavy thin- While we provide useful information on the ning would result in retention of 148—247 trees/ha characteristics distinguishing between occupied (L. Raynes pers. comm.). versus not-occupied nest stands, we recognize that To promote deep overstory canopies at the onset site occupancy is not necessarily indicative of qual- of stand initiation, planting a mixture of shade tol- ity habitat (Van Horne 1983, Vickery et al. 1992). erant (i.e., western hemlock) and intolerant (i.e., We believe our occupancy surveys are good indi- Douglas-fir) tree species at 3-4 m spacing is rec- cators of habitat quality for goshawks because, in ommended (ca. 1000 trees/ha, L. Raynes pers. our study, nest-stand occupancy and reproduction comm.). Spacing trees farther apart will reduce were closely correlated (Finn 2000, Finn et al. crown competition and may result in excessive can- 2002) . Young successfully fledged from eight of 1 opy depth (L. Raynes pers. comm.), therein cre- occupied sites. Moreover, only one of the 10 sites ating inadequate flight space for goshawks. A sin- we surveyed every year was consistently occupied, gle, moderate-level thinning of the trees remaining but never produced fledglings. in the stand (there will be some mortality) at 30- Small-scale (e.g., nest tree, nest vicinity) habitat 35-yr-old range classes, as influences on occupancy of goshawk nest stands across the of diameter opposed to thinning a specific diameter class, were not identihed in our study (Finn 2000). Thus, would promote deeper forest canopies as the stand forest managers should focus on stand scale (this develops; this is because more growing space is paper) and landscape scale (Finn et al. 2002) habitat management for goshawks. available, particularly for the larger trees (L. Ray- nes pers. comm.). Management Impi.igaiions Once thinning has occurred, overstory canopy Goshawk nest stand size in our study averaged development and a concomitant reduction in 32.6 ha in occupied historical sites and 63.9 ha in shrub cover would occur over a 5-10 yr period. not-occupied historical sites, which is within the After this, stands would likely be suitable for gos- range of 10—100 ha reported by Squires and Reyn- hawk nesting for as long as they were retained. olds (1997) for goshawk nest stands across North Mean tree age of occupied nest stands in our study America. We recommend that managers who seek was 147 yr (A = 12, SD = 71.3, range - 51-275). December 2002 Goshawk Nest-stand Habitat 275

The four youngest occupied stands were 50-70-yr- by L. Bond, M. Cowing, S. Gossett, B. Lehman, J. Munger, S. Novak, K. Steenhof, and T. Zarriello. Special thanks to old while the four oldest were 200-275-yr-old. D. Yonkin for his outstanding help in the field, his ded- suggest that it is not stand age per se that is We ication to the project, and his spirit. Superior assistance important to goshawk nesting, instead it is the hab- in the field was provided by B. Griffith, H. Tall, K. Bees- itat elements associated with older stands (this ley, B. Davies, T. Bloxton, J. Delap, J. Swingle, J. Wagen- knecht, and L. Vandernoot. Thanks also to M. Fuller, S study: deep overstory canopy, low shrub cover, Knick, Munger, K. Titus, C. Crocker-Bedford, R. Man- Squires and Reynolds 1997, DeStefano 1998: large J. nan, and M. Restani who reviewed and greatly improved trees with high canopy closure). The extent to this manuscript. which these features can be created in younger- Literature Cited aged stands will make forest management for goshawks more economically practicable. Other silvi- Agee, J.K. 1993. Fire ecology of Pacific northwest forests. cultural prescriptions may work as well as those we Island Press, Washington, DC U.S.A. suggest or may be more appropriate, depending Avery, T.E. and H.E. Burkhart. 1983. Forest measure- on site conditions. Currently, most stands on the ments. McGraw-Hill, New York, NYU.S.A. Baiity, 1996. Effects of stand density reduction Olympic Peninsula are managed on a 40-50 yr ro- J.D. on structural development in western Oregon Douglas- tation (L. Raynes pers. comm.), due primarily to a fir forests—a reconstruction study. Ph.D. dissertation, re-tooling of local sawmills to handle smaller-di- Oregon State University, Corvallis, OR U.S.A. ameter logs. Beier, P. and J.E. Drennan. 1997. Forest structure and importance of old forest attributes to the The prey abundance in foraging areas of Northern Gos- Northern Spotted Owl, which also inhabits western hawks. Ecol. Applic. 7:564-571. Washington forests and is sensitive to habitat loss, Block, W.M., M.L. Morrison, and M.H. Reiser (Eds ) is well known (Gutierrez et al. 1995, Horton 1996, 1994. The Northern Goshawk: ecology and management. Stud. Avian Biol. 16. Irwin et al. 2000) . Goshawks, however, use a broader range of forest structural stages than do North- Bosakowski, T, B. McCullough, F.J. Lapsansky, and M.E. Vaughn. 1999. Northern Goshawks nesting on a ern Spotted Owls (DeStefano 1998). We found gos- private industrial forest in western Washington./. Rap- hawks nesting in stands as young as 51 yr, and tor Res. 33:240-244. Bosakowski et al. (1999) report on goshawks nest- Buchanan, J.B., J.C. Lewis, D.J. Pierce, E.D. Forsman, ing in 40-54-yr-old managed stands in western and B.L, Biswell. 1999. Characteristics of young for- Washington. ests used by Spotted Owls on the western Olympic

In research on Northern Spotted Owl use of Peninsula. Northivest Sci. 73:255-263. young forest habitat on the Olympic Peninsula, Cherry, S. 1998. Statistical tests in publications of the Buchanan et al. (1999) report values for some hab- Wildlife Society. Wildl. Soc. Bull. 26:947-953. itat features important to Northern Spotted Owls Crocker-Bedford, D.C. 1990. Goshawk reproduction and forest management. Wildl. Soc. Bull. 18:262—269 (i.e., total snags/ha, percent shrub cover, percent

. 1998. The value of demographic and habitat canopy closure, and coarse woody debris cover) studies in determining the status of Northern Gos- that are near or within the range of values we hawks (Accipiler gentilis atricapillus) with special refer- found for these same features for goshawks (Table ence to Crocker-Bedford (1990) and Kennedy (1997)

2) . Thus, forest management as described herein J. Raptor Res. 32:329-336. may also benefit Northern Spotted Owls. AND B. Chaney. 1988. Characteristics of goshawk nest stands. Pages 210—216 in R.L. Glinski, B. Giron Acknowledgments Pendleton, M.B. Moss, M.N. LeFrank, Jr., B.A. Millsap, We want to thank those from private companies and and S.W. Hoffman [Eds.], Southwest raptor manage- public agencies that offered their assistance. The Wash- ment symposium and workshop. Natl. Wildl. Fed., ington Department of Natural Resources, Rayonier, Port Washington, DC U.S.A. Blakely Tree Farms, Champion Pacific, and the University Daubenmire, R.F. 1959. A canopy-coverage method of of Washington provided funding and logistical support. vegetational analysis. Northwest Sci. 33:43-64. Additional support, equipment, and in-kind aid was pro- Daw, S.K., S. DeStefano, and R.J. Steidl. 1998. Does sur- vided by Weyerhaeuser, the Washington Department of vey method bias the description of Northern Goshawk Fish and Wildlife, Olympic National Park, and Olympic nest-site structure? Wildl. Manage. 62:1379-1384. National Forest. We thank R. Meier, L. Raynes, S. Katzer, J. rates T. Desimone, S.M. 1997. Occupancy and habitat rela- N. Wilkins, McBride, J. Eskow, D. Runde, L. Hicks, S. Horton, P. Harrison, D. Hays, S. Desimone, E. Seaman, tionships of Northern Goshawks in historic nesting S Lemioux, and L. Young for their helpful input. Tech- areas in Oregon. MS thesis, Oregon State University, nical and analytical advice was provided with enthusiasm Corvallis, OR U.S.A. 276 Finn et al. VoL. 36, No. 4

DeStefano, S. 1998. Determining the status of Northern mensuration, 2nd Ed. The Ronald Press Company,

Goshawks in the west: is our conceptual model cor- New York, NY U.S.A. Irwin, L.L., D.F. Rock, and G.P. Miller. 2000. Stand rect? J. Raptor Res. 32:342-348.

, S.K. Daw, S.M. Desimone, and E.C. Meslow. structures used by northern Spotted Owls in managed

1994. Density and productivity of Northern Goshawks: forests, y. Raptor Res. 34:175-186. implications for monitoring and management. Stud. Johnson, D.H. 1999. The insignificance of statistical sig- Avian Biol. 16:88—91. nificance testing./. Wildl. Manage. 63:763-772. Joy, S.M., R.T. Reynolds, and D.G. Leslie. 1994. North- AND J. McCloskey. 1997. Does vegetation structure limit the distribution of Northern Goshawks in ern Goshawk broadcast surveys: hawk response variables and survey cost. Avian Biol. 16:24-30. the Oregon coast ranges? J. Raptor Res. 31:34—39. Finn, S.P. 2000. Multi-scale habitat influences on North- Keane, JJ- AND M.L. Morrison. 1994. Northern Goshawk ern Goshawk occupancy and reproduction on Wash- ecology: effects of scale and levels of biological orga- 16:3-11. ington’s Olympic Peninsula. M.S. thesis, Boise State nization. Stud. Avian Biol. University, Boise, ID U.S.A. Kennedy, P.L, 1988. Habitat characteristics of Cooper’s Hawks and Northern Goshawks nesting in New Mex- , J.M. Marzluff, and D.E. Varland. 2002. Effects ico. Pages 218-227 in R.L, Glinski, B. Giron Pendle- of landscape and local habitat attributes on Northern ton, M.B. Moss, M.N. LeFrank, B.A. Millsap, and Goshawk site occupancy in western Washington. For. Jr., S.W. Hoffman [Eds.], Southwest raptor management Sci. 48:427-436. symposium and workshop. Natl. Wildl. Fed., Washing- Franklin, J.F. and C.T. Dyrness. 1988. Natural vegetation ton, DC U.S.A. of Oregon and Washington. Oregon State Univ. Press, and D.W. Stahlecker. 1993. Responsiveness of Corvallis, OR U.S.A. nesting Northern Goshawks to taped broadcasts of Gutierrez, R.J., A.B. Franklin, and W.S. LaHaye. 1995. three conspecific calls. /. Wildl. Manage. 57:2249-2257. Spotted Owl (Strix occidentalis) . In A. Poole and F. Gill Long, J.N., J.B. McCarter, and S.B. Jack. 1983. A mod- [Eds.], The birds of North America, No. 179. The ified density diagram for coastal Douglas-flr. West. Academy of Natural Sciences, Philadelphia, PA and J Appl. For. 3:88-89. The American Ornithologists’ Union, Washington, McGrath, M.T. 1997. Northern Goshawk habitat analysis DC U.S.A. in managed forest landscapes. M.S. thesis, Oregon Hayes, J.P., S.S. Chan, W.H. Emmingham, J.C. Tappeiner, State University, Corvallis, OR U.S.A. L.D. Kellogg, and J.D. Bailey, 1997. Wildlife re- Newton, I. 1979. Population ecology of raptors. Buteo sponse to thinning young forests in the Pacific North- Books, Vermillion, SD U.S.A. west. /. For. 95:28-33. Oliver, C. D. and B. C. Larson. 1990. Forest stand dy- Hayward, G.D. and R.E. Escano. 1989. Goshawk nest-site namics. McGraw-Hill, New York, NY U.S.A. characteristics in western Montana and northern Ida- Patla, S.M. 1997. Nesting ecology and habitat of the ho. Gowrfor 91:476-479. Northern Goshawk in undisturbed and timber harvest Henderson, D.H. Peter, R.D. Lesher, and D.C. J.A., areas on the Targhee National Forest, Greater Yellow- Shaw. 1989. Forested plant associations of the Olym- stone Ecosystem. M.S. thesis, Idaho State University, pic National Forest. U.S. For. Serv. Gen. Tech. Rep. Idaho Falls, ID U.S.A. RG-ECOL-TP 001-88, Portland, U.S.A. OR Patton, D.R. 1997. Wildlife habitat relationships in for- Habitat selection birds. Zool. Hidden, O. 1965. in Ann. ested ecosystems, Revised Ed. Timber Press, Portland, Fenn. 2:53—75. OR U.S.A. R.S., E.D. Hoi.thausen, M.G. Raphael, K.S. McKelvey, Penteriani, V. AND B. Faivre. 1997. Breeding density and Forsman, E.E. D.E. Seaman. 1995. Siarkey, and The nest-site selection in a goshawk Accipiter gentilis popu- federal habitat contribution of and non-federal to lation of the Central Apennines (Abruzzo, Italy). Bird persistence of the northern Spotted Owl on the Olym- Stud. 44:136-145. pic Peninsula, Washington: report of the reanalysis Reineke, L.H. 1933. Perfecting a stand-density index for team. U.S. For. Serv. Gen. Tech. Rep. PNW-GTR-352, even aged forests. J. Agric. Res. 46:627-637. Portland, OR U.S.A. Reynolds, R.T., E.C. Meslow, and H.M. Wight. 1982 Horton, S.P. 1996. Spotted Owls in managed forests of Nesting habitat of coexisting accipiters in Oregon./ western Oregon and Washington. Pages 215-231 in Wildl. Manage. 46:124-138. Bird, [Eds.], D.M. D.E. Varland, and J.J. Negro Rap- Rice, W.R. 1989. Analyzing tables of statistical tests. Evo- tors in human landscapes: adaptations to built and lution 43:223-225. cultivated environments. Academic Press Ltd., Lon- Robinson, M.W. 1947. An instrument to measure forest don, U.K. crown cover. For. Chron. 23:222-225. Hosmer, D.W. and S. Lemeshow. 1989. Applied logistic SAS Institute, Inc. 1998. SAS/STAT user’s guide. Re- regression. John Wiley and Sons, New York, NYU.S.A. lease 6.03. SAS Inst., Cary, NC U.S.A. Husch, B., C.I. Miller, and T.W. Beers. 1972. Forest Siders, M.S. and P.L. Kennedy. 1996. Forest structural December 2002 Goshawk Nest-stand Habu a i 277

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allometric relationship? Conrfor 98:123-1 32- agement. 1 994. Record of decision for amcndmcnls Spf.tser, R. and T, Bosakowski. 1987. Nest site selection to Forest Service and Bureau cjf Land Management by Northern Goshawks in northern New Jersey and planning documents within the range of the northern southeastern New York. Condor 89:387-394. Spotted Owl. Standards and guidelines for manage- Squires, J.R. and L.F. Ruggiero. 1996. Nest-site prefer- ment of habitat for late-successional and old-growth ence of Northern Goshawks in south-central Wyo- forest related species within the range of the northern

ming. /. Wildl. Manage. 60:170-177. Spotted Owl. Washington, DC U.S.A. B. AND R.T. Rit'VNOl.DS. 1997. Northern Goshawk {Ac- Van Horne, 1983. Density as a misleading indicator

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278 Finn et al. VoL. 36, No. 4

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SUBORDINATE MALES SIRE OFESPRING IN MADAGASCAR EISH-EAGLE {HALIAEETUS VOCIFEROIDES) POLYANDROUS BREEDING GROUPS

Ruth E. Tingay* School of Geography, University of Nottingham, Nottingham, NG7 2RD ILK. and the Peregrine Fund, 5668 Flying Hawk Lane, Boise, ID 83709 U.S.A.

Meianie Culver, Eric M. Haiuerman, and James D. Fraser Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 U.S.A.

Richard T. Watson The Peregrine Fund, 5668 Flying Hawk Lane, Boise, ID 83709 U.S.A.

Abstract.—The island endemic Madagascar Fish-Eagle (Haliaeetus vociferoides) is one of the most endangered birds of prey. Certain populations in west-central Madagascar sometimes exhibit a third, and sometimes a fourth, adult involved in breeding activities at a nest. We applied DNA fingerprinting to assess relatedness among 17 individuals at four nests. In all nests with young, a subordinate rather than the dominant male sired the offspring. Within-nest relatedness comparisons showed that some dominant males had an apparent hrst-order relationship with the female. Between-nest relatedness comparisons showed that some adults had an apparent hrst-order relative at another nest in the study area. Findings that subordinate males contribute to breeding, and that adults in an area may be related, may require conservation measures such as translocation to assure the species’ survival.

Keywords: Madagascar Fish-Eagle, Haliaeetus vociferoides; DNA fingerprinting, mating system; nest helper, polyandry.

MACHOS subordinados engendran descendencia en grupos de reproduccion po- LIAnDRICA en AGUIIAS PESCADORAS DE MADAGASCAR {HALIAEETUS VOCIFEROIDES)

Resumen.—El aguila pescadora endemica de la isla de Madagascar {Haliaeetus vociferoides) es una de las aves rapaces mas amenazadas de extincion. Algunas poblaciones en el occidente-centro de Madagascar exhiben algunas veces un tercero y a veces un cuarto adulto involucrado en las actividades reproductivas en un solo nido, Aplicamos un analisis de ADN para evaluar el parentesco entre 17 individuos de cuatro nidos. En todos los nidos con juveniles, un macho subordinado mas que el dominante engendro la prole. Las comparaciones de parentesco dentro de los nidos mostro que algunos machos dominantes tenian aparentemente una relacion de primer orden con la hembra. Las comparaciones entre nidos mostraron que algunos adultos tuvieron un pariente de primer orden en otro nido dentro del area de

estudio. El hallazgo de que los machos subordinados contribuyen a la reproduccion, y que los adultos en un area pueden estar relacionados entre si, pueden hacer necesarias medidas de conservacion tales como traslados para asegurar la supcrvivencia de la especie. [Traduccion de Cesar Marquez]

The island endemic Madagascar Fish-Eagle {Hal- gered (Collar et al. 1994) . With 63 known breeding

laeetus vociferoides) is considered critically endan- pairs, and an estimated total breeding population

of 100-120 pairs (Rabarisoa et al. 1997), it is among the most endangered birds of prey in the '' These two authors contributed equally to this manu- world (Langrand and Meyburg 1989, Watson et al. script. 1993, 1996). Madagascar Fish-Eagles exhibit an un- ' Present address of corresponding author: Wildlife and Fisheries Science, University of Arizona, Tucson, AZ usual dispersal and breeding strategy, possibly re- 85721 U.S.A.; e-mail address: [email protected] stricting the species’ distribution and abundance

280 December 2002 Relaxedness of Madagascar Fish-Eagles 281

through limited dispersal or occurrence of in- briefly removed from the nest at ca. 7 wk of age and banded. Blood (0.1-0.25 ml) was taken from the brachial breeding. Breeding was believed to be monoga- vein (Tingay 2000), immediately placed in 4.5 ml of lysis mous, but at 46% of known nests, a third, and buffer (100 mM, pH 8.0, 100 rriM EDTA, 10 niM NaCil, sometimes a fourth adult is involved with the 0.5% SDS) in a polypropylene tube, labeled, and stored breeding activities of the primary pair (Watson et at ambient temperature. DNA Purification. Approximately 200 |xl of blood/ al. 1999). Based on banding studies at several nests buffer solution was placed in 800 fxl lysis buffer for 10 (Watson et al. 1999), extra-pair birds were believed min. Protein digestion was performed with 500 (xl of su- to be progeny (possibly only male) from previous pernatant from the first step, 500 |xl of fresh lysis buffer, years. Such delayed dispersal can result in forma- and 0.5 mg/ml proteinase K, with incubation at 37°C tion of cooperative breeding groups, a relatively overnight. Extractions were performed in 1:1 phenol

chloroform, and 24:1 chloroform : isoamyl alcohol. DNA rare breeding system among birds (Stacey and Ko- was precipitated using cold 95% ethanol and 5% sample enig 1990, Ligon 1999), especially among raptors volume of 5M (0.082M final) ammonium acetate. DNA (Simmons 2000, and references therein). Ecologi- was resuspended in 25 |xl deionized water and stored at cal or behavioral factors may influence evolution -20°C. Fingerprinting. samples were sep- of cooperative breeding strategies (Newton 1979, DNA DNA digested arately with Hinfl, Rsal, and Haelll. Digests were loaded Oring 1986, Faaborg and Bednarz 1990, Stacey and onto 1% TBE agarose gels (20 cm X 24 cm), and sub- Koenig 1990, Sherman 1995), and contribute to jected to electrophoresis (Sambrook et al. 1989) at 32 V attendance of additional adults at Madagascar Fish- for 25 hr. Identity Sizing Standard (Lifecodes Corpora- Eagle nests. Understanding dispersal and repro- tion, Stamford, CT) was placed in several lanes of the gel to provide molecular weight markers. DNA in the gel was ductive strategies is critical for developing a man- stained using ethidium bromide, photographed using fW agement plan to ensure the species’ survival. luminescence, and transferred (Southern 1975) onto a DNA markers have been applied to a variety of MagnaCharge 0.45 micron nylon membrane (Micron Separations Inc., Westborough, MA) Jeffreys et al questions regarding conservation of birds (Haig . (1985) and Jeffreys (1987) minisatellite probe 33.15 was and Avise 1996) . DNA fingerprinting proved useful hybridized using the NICE hybridization solution (Life- to assess relatedness at the nest (Westneat 1990, codes Corporation, Stamford, CT) onto digested, im- Wetton et al. 1992, Haig et al. 1993, 1994a, 1994b) mobilized DNA. Both the 33.15 probe and Identity Sizing and population (Triggs et al. 1992, Fleischer et al. Standard were labeled with NICE chemiluminescence Unhybridized probe and size standard were washed from 1994) levels, to infer species-level population ge- the membrane using Quick-Light wash solutions (Life- netic structure (Longmire et al. 1991), and to es- codes Corporation) . The hybridized probe was illuminat- timate relatedness in captive stocks (Kirby 1990: ed with Lumi-Phos 480 (I.ifecodes Corporation) and vi- 239). We used DNA fingerprinting to determine sualized by exposure to Kodak XAR5 X-omat film. Fingerprinting Analysis. Gels were arrayed with paternity among Madagascar Fish-Eagle adults at- DNA samples from individuals attending a nest adjacent to one tending a nest, and to examine the level of relat- another. If all hybridization bands observed for nestlings edness among adults within and between nests. could have been inherited from the primary pair, we con-

cluded that the primary pair was the parents. If, however, Methods a hybridization band could be accounted for only by parentage by a nest attendant, we concluded that an extra- Samples. We studied three trios and one quartet of pair mating had occurred. There was only one adult fe- fish-eagles at a site in west-central Madagascar (19°S, male at each nest. The male that was most dominant and 44°30'E) on a daily basis during one breeding season exhibited the greatest paternal investment (Tingay 2000) from 24 June-5 October 1999. The area is tropical decid- was considered the male of the primary pair. uous dry forest containing several lakes (3.09-4.86 km^) DNA band-sharing (Bruford et al. 1992) was calculated and supports 11 fish-eagle territories (Rabarisoa et al. as S = 2n^y/ (n^ + riy), where = the number of bands 1997). Eagles were marked and are referred to by num- shared by both individuals, = the total number of ber. Nest sites are referred to by location and nest num- bands exhibited by individual x, and = the total number (Ankerika 4, Befotaka 2, Befotaka 3, and Soamalipo ber of bands exhibited by individual y. Band-sharing was 2). A dominance hierarchy was observed at each nest estimated for all combinations of individuals in this study based on aggressive interactions between adults. Aerial The range of S for known parent-offspring combinations pursuits (chasing) and physical displacements from ei- provided a quantitative expectation of how many bands ther the nest or from perches within 200 m of the nest must be shared before a hypothesis of familial related- tree, often accompanied by a distinctive ‘displacement’ ness was supported. call, were observed throughout the breeding period and were interpreted as signs of aggression (Tingay 2000). Results Males are referred to as either dominant (a), or subor- Parentage Assessment of Nestlings and dinate ((3 or y). We were unable to establish the domi- Juve- nance hierarchy at nest site Befotaka 3. Nestlings were niles. DNA fingerprinting techniques were used to 282 Tingay et al. VoL. 36, No. 4

assess relatedness of 17 eagles at four nests. Two Ankerika 4. Band-sharing values suggested a po- enzymes {HaAll and RscH) produced clearly inter- tential first-order relationship between female 113 pretable results yielding a total of 34 bands scored, and a male 31, but not between the female 113 24 of which were variable and 10 invariant (Table and P male 34. Band-sharing suggested that the 1). Of the 24 variable bands, six were informative males were unrelated. in determining one or more possible parents for Befotaka 2. Band-sharing values did not support the two nestlings at Soamalipo 2; three for the ju- a first-order relationship between the female and venile at Befotaka 3; and seven for the nestling at either male, nor between males. P male 8 had two Befotaka 2. Blood samples were available only for bands not shared with any individual within the adults at Ankerika 4. A nest-by-nest assessment of study population; trapping records indicate that p parentage is presented below. male 8 fledged from the Befotaka 3 nest in 1993. Befotaka 2. Female 121, a male 118, and P male Befotaka 3. Band-sharing values indicated a po- 8 attended the nest. Nestling 47 shared three var- tential first-order relationship between female 6 iant /facIII and one variant Bsdi hybridization and male 150, but not between female 6 and male bands with adult female 121 and two variant 7/fldlI 48. Band-sharing suggested that the males were , un- and one variant hybridization bands with p related. male suggesting subordinate 2. 8 , that P male 8 was Soamalipo Band-sharing values indicated a po- the father of the nestling 47, and not a male 118. tential first-order relationship between female 103 Befotaka 3. Female 6 potential a male and and a male but not between female 103 and the , 48, 5, potential a male 150 attended this nest. Juvenile two subordinate males (P 136 and 7 30). Band- 128 shared one HadW band and one Rsa\ band sharing between a male 5 and 7 male 30 indicated with adult female 6 . Banding records show that ju- a potential first-order relationship. venile 128 fledged from this nest in 1998. Although Relatedness estimates between nests. Comparing band sharing showed it unlikely that either adult among nests, we observed high band-sharing val- male at the nest in 1999 (48 and 150) was the fa- ues between female 121 (Befotaka 2) and female ther, it is highly probable that the adult female at 103 (Soamalipo 2), male 5 (Soamalipo 2) and male the nest is the mother {S — 0.95 is the highest 48 (Befotaka 3), and between male 34 (Ankerika value in the study, female 6 has been recorded at and female 6 (Befotaka suggesting potential 4) 3) , this nest site every year since 1993, and no other first-order relatedness between these pairs of female has been recorded at this nest). adults.

Soamalipo 2. Female 103, a male 5, p male 136, Discussion and 7 male 30 attended this nest. Nestling 68 shared one HaeWl band with adult female 103 and Subordinate males may have fathered all nest- two bands with 7 male 30. Nestling 00 shared lings in this study. At Soamalipo 2, one subordinate one HadW and one Rsoi band with adult female male appeared to have fathered both nestlings, 103 and one HaeWl and three Rsai bands with 7 however, because a male 5 and 7 male 30 are close male 30. The apparent father of both nestlings is relatives, and because of missing data for a male subordinate 7 male 30. 5, we cannot exclude a male 5 as a possible father Relatedness Estimates of All Adults Within and of one or both nestlings. At all nests, paternity by Between Nests. Among 136 pairwise comparisons, subordinates could have occurred by chance, as all band-sharing among individuals ranged from 0.58- attending males copulated with the female (Tingay 0.95, with a mean value of 0.79. Partitioning pair- 2000). Paternity by subordinates was surprising giv- wise band-sharing into within- and between-nest en that dominant males invested more energy to components showed no difference (mean S — 0.80 the nesting attempt than subordinate males (Tin- within nests and 0.79 between nests). After ac- gay 2000). This level of dominant male investment counting for eight known first-order relative pairs may be explained by the apparent first-order relat- (parent-offspring, full-sibling), band-sharing was edness of the female and the dominant male at higher among first-order relatives (v = 0.87, range three of four nests (Ankerika 4, Befotaka 3, and = 0.82-0.95) than overall (x = 0.79; Table 2). Us- Soamalipo 2). Because 50% of alleles are shared ing these findings, relatedness among adults at- with a first-order relative, and 25% with an off- tending nests (male-male, male-female) was deter- spring of a first-order relative, then shared alleles mined (Table 2). are transmitted to the next generation if a first- December 2002 Reiatedness of Madagascar Flsh-Eagles 283

Table 1. DNA fingerprinting hybridization bands (Jeffreys 33.15 probe) observed for individual Madagascar Fish- Eagles. Bands are designated by enzyme used (H = Hae\\\ or R = Rsai) and molecular weight of bands in kilobase pairs. Sex and rank for individuals is indicated (F = female, aM = alpha male, pM = beta male, yM = gamma male, NSL = nestling, JUV = juvenile).

Ankerika 4^ Befotaka 2'’ Befotaka 3'= Soamalipo 2^

F aM (3M F aM (3M ;NSL F aM? aM? JUV F aM PM yM NSL NSL Individual 113 31 34 121 118 8 47 6 150 48 128 103 5 136 30 68 00

Bands H 16.0 + + + + + + + + + + 4 4 4 4 4 4 4 H 10.7 -F + + 4 4 H 8.5 + + + + + + + + + 4 4 4 4 4 4 4 4 H 7.3 + + + + + + + 4 4 4 4 4 4 H 6.5 + + + + 4 H 6.0 -F -F -F 4 4 H 5.7 + + + + 4 4 H 5.6 + + 4 H 5.2 + 4 H 4.9 -F -F 4 4 H 4.7 + H 4.5 + + + + + + + 4 4 4 4 4 4 4 H 3.9 + + + + + + + + + 4 4 4 4 4 4 H 3.6 -F -F -F + + 4 4 4 H 3.2 + + + + + + + + 4 4 4 H 2.9 + + + + + + + + + 4 4 4 4 4 4 4 4 H 2.7 + -F + + + + + + 4 4 4 4 4 4 4 4 H 2.6 + + + + -F -F -F -F -F 4 4 4 4 4 4 4 4 H 2.2 + + + + + + -F + + 4 4 4 4 4 4 4 4 H 1.5 + + + + + + + + + 4 4 4 4 4 4 4 4 H 1.4 -F -F -F + -F -F + + + 4 4 4 4 4 4 4 4 H 1.0 + + + + 4 4 4 4 4 4 4 H 0.9 + + + + + + + 4 4 4 4 4 R 12.0 + + + + + + + + + 4 4 4 ? 4 4 4 4 R 5.2 -F -F -F -F ? R 5.0 + + + + + + 4 ? 4 4 4 R 4.7 + + 4 ? 4 4 4 R 4.5 + ? R 4.4 + -F -F -F -F 4 ? 4 R 4.2 + ? 4 4 R 3.3 + + + + + + + + 4 4 4 ? 4 4 4 4 R 1.5 + + + 4 4 ? 4 4 4 4 R 1.4 + + + -F -F -F -F 4 4 ? 4 4 4 R 1.2 4 + + + + + + + + 4 4 4 ? 4 4 4 4

Total No. bands per individual 21 21 22 20 20 22 26 21 21 20 19 21 14 19 21 20 23

^Fifteen bands are variable at Ankerika 4 (H 7.3, H 6.5, H 6.0, H 5.7, H 5.6, H 4.9, H 3.6, H 1.0, H 0.9, R 5.2, R 5.0, R 4.7, R 4 4, R 1.5, R 1.4). All other bands are invariant.

Of the variable bands at Befotaka 2, six are shared between the nestling and the female (H 10.7, H 4.5, H 3.6, H 1.0, R 5.0, R 1 5), six are shared between the nestling and the beta male (H 6.5, H 6.0, H 0.9, R 5.2, R 4.4, R 1.4); one is shared between the nestling, female, and beta male (H 3.2); and four are variable but are not observed in tbe nestling (H 5.7, H 5.2, H 4.7, R 4.5). All other bands are invariant.

Of the variable bands at Befotaka 3, four are shared between the juvenile and the female (H 7.3, H 6.5, H 3.6, R 4.7); and ten are variable but are not observed in the juvenile (H 10.7, H 6.0, H 5.7, H 5.6, H 4.9, H 3.2, H 1.0, R 5.0, R 4.2, R 1.5). All other bands are invariant.

Of the variable bands at Soamalipo 2, four are shared between nestling 68 and the female (H 7.3, H 3.9, H 3.2, R 5.0); two are

shared between nestling 68 and the gamma male (R 4.7, R 1.4); and one is shared between nestling 68, the female, and the gamma male (H 4.5). Five bands are shared between nestling 00 and the female (H 3.9, H 3.6, H 3.2, R 5.0, R 4.4); four are shared between

nestling 00 and the gamma male (H 0.9, R 4.7, R 4.2, R 1.4); and one is shared between nestling 00, the female, and the gamma male (H 4.5). Five are variable but are not observed in either nestling (H 10.7, H 6.0, H 5.7, H 5.2, H 4.9); and all other bands are invariant. < H H H —

284 Tingay et al. VoL. 36, No. 4

be 2 G O J ^ C/D O S 2 2 be cu ^ g o 1) S II fl ^ 0.88 d 2 . C/!) ^ 2; a QO o cvr cn " u CO S o QO 0.82 2 V O GO 2 u ^ d s 9 d Cl O I> a o GO QO J> 0.67 ’J} >•-. 0 GO. d d tu - c/) ,!-i i ^ be ^ I, C ^ XI oc I> 00 00 0.86 a G d d d >- ^ X c VS 0 a; i.1 1— V d GO CO O I X a r“H 1 o 00 00 i> 00 0.86 G d d d d 1-H B X CO G ’G CO ? G > 00 xO X GO 0 CM X X !>• 00 X X X 0.81 2 2i d d d d d 2 II G O ' GO 0 M GO 0 —J GCL w CO i> C3D J> 00 00 0.79 be „ 2 ri d d d d d .a 2 ce

^ l=i a o 2 o X 0 T~( 0 10 X X x> 00 0.77 G u 2 »-o X X 0 r- X X •J-i d d d d d d d vs OJ 2 a -G 00 in X 10 X 0.91 G II 00 i> O) X X X GO 00 rt d d d d d d d d S aS G a jS X ^ »oi>eoo mXi-Hi>GO X X oqi^oooo cc cc CO 0.86 s 2 ^ dddd ddddd vs a •i— a; X d G 'd CO CJD X X 0 CO 03 in a II 2 G ac 00 tr^ j> i> i> 00 in X I> 0.71 cu. V X !i d d d d d d d d d d be 0 !=! TJ a; 0 2 cc X X GO X 0 cvr X 03 i> CO m i> X X 00 i> 0.79 u G ^ d d d d d d d d d d d T3 Q G d Cfi '' '' V X m 1 1 CO X 0 i> CO CO (M X 0 u cu 0.84 G |b-i CM X 00 QO X 03 X X i> 03 tj c u • O I-^ d d d d d d d d d d d d cu d * vs G H t3 OJ 0 1 —1 u X — QO X Tf CO 03 X X 0 1 > X" X X'' X X X X X l'^ X X X'- X 0.89 2 OJ GO 0 CD. d d d d d d d d d d d d d d 2 _G d vs t/2 •w o; 0 vs m CO X rH X m X 0 0 X GO XJ OJ ,0 00 X^ 00 i> 0.73 c 2 X X (X X X X x^ 00 "d 1 d d d d d d d d d d d d d d > OJ c u T! OJ a c OJ c cn X 03 X X 03 X X CO m 1-H 0 rH CO 00 t> X-; 00 00 00 i> 00 QO x> 00 00 0.86 d d d d d 0 d d d d 0 d d d d S G c/s vs T3 X G T— 0 G OJ T3 O OC X 0 CC 00 GO 1-0 X 0 X CM i—H 1-0 CM G C/D D QO X 0 QO QO X T— ! X) o 2 T“^ 1— H . Q Cfl V £ CG n. 1 vs a hJ HH bo G X C/D NSL ? s S S d /C a cn Ph a ca 2 Ph a a a (TL 5-h W 2 I Ph M VS CM CO 0 d d d CG CM u a 24 M X d ’E d d G be -uj -(-J u OJ vs G a rO d d 2 2 G be G OJ u 0 d CQ PQ X ,

Deciembkr 2002 REIATEDNESS of MADACiASCAR FiSH-EAGI.ES 285

order relative reproduces successfully. At Soamali- some of those specific individuals as likely candi- po 2, the dominant male gained an additional ge- dates for translocation, in order to reduce the netic advantage by having two potential hrst-order probability of further inbreeding and to create an relatives at the nest (the female and the y male). opportunity for outbreeding with other, genetically It would be advantageous to be a male at the same dissimilar, individuals. nest as a brother, because if either mated success- Acknowledgments fully, then shared genes are transmitted to the next generation. Although a strategy of assisting repro- We conducted this study under The Peregrine Fund’s Madagascar Fish-Eagle and Wetland Conservation Pro- ductive efforts of close relatives may be advanta- ject. We thank the Madagascar Direction des Eaux et For- geous for some Madagascar Fish-Eagles, apparently ets, Tripartite Commission, Association Nationale pour la it is not the only strategy in use. At Befotaka 2, the Gestion des Aires Protogees and United Nations Educa- dominant male was not the father, and nor was he tional, Scientific, and Cultural Organization for collaboration. This was funded in part by grants from the a first-order relative of either the female or the sub- work Liz Claiborne and Art Ortenberg Foundation, Environ- ordinate male. ment Now, the John D. and Catherine T. MacArthur At Befotaka 3, a juvenile female did not disperse. Foundation, Biodiversity Support Program, Hawk Moun- This is the hrst observed instance of a female nest- tain/Zeiss Optics 1999 Research Award, Jim Brett Global ling from a previous year remaining at a nest (Ra- Conservation Fund and University of Nottingham. We are grateful to Professor David Parkin for technical assis- fanomezantsoa 1997). Flere, delayed dispersal was tance with DNA purification, to Jim Berkelman and two not associated with helping activity, yet observed anonymous referees for their thoughtful comments on the female juvenile was tolerated at the nest. Al- an earlier draft of this paper, and to Peregrine Fund Field though inconclusive, our findings do not exclude Manager Loukman Kalavah for expertise in the field the delayed dispersal hypothesis. Literahjre Cited Between-nest relatedness comparisons revealed that some adults had a potential close relative (par- Bruford, M.W., O. Hanotte, J.F.Y. Brookfield, and T Burke. multilocus finger- ent-offspring or full-sibling) at another nest within 1992. Single-locus and DNA printing. Pages 225-269 ire A.R. Hoelzel [Ed.], Molec- the study area. This suggests that hrst-order rela- ular genetic analysis of populations: a practical ap- tives (excluding nestlings) are as likely to be found proach. IRE Press, Oxford, U.K. among nests as within a nest. Coliar, N.J., M.J. Crosby, and A.J. Stattersfield. 1994 We are currently investigating the full range of Birds to watch 2: the world list of threatened birds breeding strategies in the Madagascar Eish-Eagle. BirdUife International, Cambridge, U.K. We intend to determine whether this species ex- Faaborg, J. and J.C. Bednarz. 1990. Galapagos and Har- hibits genetic monogamy or polyandry by extend- ris’ Hawks: divergent causes of sociality in two raptors ing our sample size and duration of study. Studies Pages 359-383 in P.B. Stacey and K.W. Koenig [Eds ] of another cooperative polyandrous raptor species, Co-operative breeding in birds: long term studies of ecology and behaviour. Cambridge Univ. Press, the Galapagos Hawk {Buteo galapagoensis) has re- Cam- bridge, U.K. vealed mixed paternity at nests over two consecu- , P.G. Parker, U. Df.Uay, TJ. deVries, J.C. Bednarz, tive breeding seasons (Faaborg et al. 1995). How- S. Maria Paz, J. Naranjo, and TA. Waite. 1995. Con- ever, the dominance hierarchy we have observed firmation of co-operative polyandry in the Galapagos among cooperative hsh-eagles has not been docu- Hawk (Buteo galapagoensis). Behav. Ecol. Sociohiol. 36: mented among Galapagos Hawks, which may or 83-90. may not influence the occurrence of genetic mo- Fieischer, R.C., C.L. Tarr, and T.K. Pratt. 1994. Ge- nogamy within polyandrous groups of Madagascar netic structure and mating system in the Palila, an

Fish-Eagles. If delayed dispersal is obligatory in this endangered Hawaiian honeycreeper, as assessed by species, recolonization of unoccupied habitats may DNA fingerprinting. Mol. Ecol. 3:383-392. FIaig, S.M., Belthoff, D.H. Ailen. 1993. have to be promoted by active conservation mea- J.R. and Ex- amination of population structure in Red-cockaded sures, such as the translocation of individuals from Woodpeckers using DNA profiles. Evolution 47:185- other areas. Additionally, copulation by closely-re- 194. lated pairs, as observed in this study, suggests that ? J-b- Ballou, and NJ. Casna. 1994a. Identifica- the effects of inbreeding may have to be consid- tion of kin structure among Guam rail founders a ered in conservation planning. For example, if comparison of pedigrees and DNA profiles. Mol. Ecol hrst-order relatives are found to be producing off- 4:109-119. spring, conservation managers may wish to target , J.R. Wai.ters, andJ.H. Plissner. 1994b. Genetic . 1

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evidence for monogamy in the Red-cockaded Wood- Sambrook, J., E.F Fritsch, and T. Maniatis. 1989. Mo- pecker, a cooperative breeder. Behav. Ecol. Sociobiol. 23: lecular cloning: a laboratory manual, 2nd Ed. Cold 295-303. Spring Harbor Press, New York, NY U.S.A.

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tion project, progress report 3, 1995-1996. The Per- egrine Fund, Boise, ID U.S.A. Received 26 November 2001; accepted 23 July 2002 ——

NESTING AND PERCHING HABITAT USE OE THE MADAGASCAR FISH-EAGLE

James Berkelman^ and James D. Fraser Department of Fisheries and Wildlife Sciences, Virginia Polytechnical Institute and State University, Blacksburg, VA 24061-0321 U.S.A.

Richard T. Watson The Peregrine Fund, 5668 West Flying Hawk Lane Boise, ID 83709 U.S.A.

Abstract. We documented Madagascar Eish-Eagle (Haliaeetus vociferoides) nest and perch use on lakes and rivers and compared parameters of used trees to unused reference trees. Nest and perch trees were broader and taller, had more unobstructed branches, and were less obstructed by adjacent trees compared to reference trees. Perch trees also were more often deciduous than reference trees. Nest sites

had more shoreline perch trees than reference sites. Logistic regression models with tree height as the independent variable distinguished nest and perch trees from randomly selected reference trees. Models with number of perch trees along a 1.25 ha (50 m width) shoreline section distinguished nest sites from reference sites. These models suggest that the presence of trees >15 m tall within 50 m of the shoreline

is a good predictor of Madagascar Eish-Eagle habitat use.

Key Words; Madagascar Fish-Eagle, Haliaeetus vociferoides; habitat; Madagascar, nest tree, perch tree, shore-

line.

USO DE HABITAT DE ANIDACION Y PERCHA DEL AGUILA PESCADORA DE MADAGASCAR

Resumen. -Documentamos el uso de nidos y perchas para el aguila pescadora de Madagascar {Haliaeetus vociferoides) en lagos y rios y comparamos parametros de arboles usados con arboles no usados de referenda. Los nidos y arboles percha fueron mas anchos y mas altos, tenian mas ramas despejadas, y estaban menos obstruidos por arboles adyacentes en comparacion con los arboles referenda. Los arboles percha fueron ademas algunas veces mas deciduos que los arboles control. Los sitios nido disponian de mas arboles percha costeros que los sitios de referencia. Los modelos de regresion logistica con la altura de los arboles como variable independiente distinguieron los nidos y arboles percha de arboles control seleccionados aleatoreamente. Los modelos con numeros de arboles percha cerca a 1.25 ha (50 m de ancho) de la seccion de costa distinguieron los sitios nido de los sitios referencia. Estos modelos sugieren que la presencia de arboles >15 m de alto dentro de 50 m de la linea costera es un buen pronosticador del uso de habitat del aguila pescadora de Madagascar. [Traduccion de Cesar Marquez]

With a population estimate of 99 breeding pairs ies of Madagascar Fish-Eagle nesting or perching

(Rabarisoa et al. 1997), the Madagascar Fish-Eagle habitat use.

{Haliaeetus vociferoides) is one of the rarest birds of Nelson and Horning (1993) estimated from sat- prey in the world (Meyburg 1986). Until recently, ellite data that Madagascar’s forest cover had been little was known about the species’ ecology and sta- reduced to 10.4% of the island by 1990. Nest-site tus. Langrand and Meyburg (1989) noted that the availability is a key limiting factor for raptor pop- Madagascar Fish-Eagle used tall trees near water ulations (Newton 1979). Also perch-tree distribu- for nests and foraging perches, but prior to this tion is a reliable predictor of Bald Eagle {Haliaeetus study, there had been no detailed quantitative stud- leucocephalus) distribution on the Chesapeake Bay (Chandler et al. 1995). Thus, we focused our study both nest perch trees, with the sur- ' Present address: Department of Wildlife Ecology, Uni- on and along versity of Wisconsin, 218 Russell Labs, 1630 Linden Dr., rounding habitat conditions. The objectives of this Madison, W1 53706-1598; e-mail address: jberkelman® study were to determine characteristics of nest facstaff.wisc.edu trees, nest sites, and perch trees used by Madagas-

287 288 Berkelman et al. VoL. 36, No. 4

Table 1. Sites where Madagascar Fish-Eagle nests and perches were investigated in the region of Antsalova, Mada- gascar, 1994. Site names are lakes unless otherwise indicated.

Number oe Site Latitude, Longitude Eagle Pairs

Masiadolo 18°41'S, 44°28'E H

Besara 18°41'S, 44°16'E 1 Soahanina River 18°46'-48'S, 44°16'~19'E 3^ Antsahafa 18°48'S, 44°29'E P Masama 18°50'-5TS, 44“28'-29'E 2

Tsiandrora 18°58'S, 44°38'E 1 1'’ Andranolava 19°0'S, 44°2TE 1 Befotaka 19°1'-2'S, 44°24'-25'E 3 Soamalipo 18°59'-19°2'S, 44°26'-27'E 3^ Ankerika 19°T-2'S, 44'^27'-44°28'E 4

Andranovorimirafy 19°3'S, 44°27'E 1 2'^ Andranolava 19°4'S, 44°25'E 1 Antsakotsako 19°6'S, 44°33'E 1^

Ampozabe 19°9'S, 44°40'E 1

Bevoay 19°9'S, 44°25'E 1 Manambolo River 19°8'-9'S, 44°44'-49'S 2

Maromahia 19°11'-12'S, 44°37'-38'E 1

Bejijo 19°12'-14'S, 44°32 -33'E 1

No nest was found for one of the fish-eagle pairs at five of the sites. Two of the lakes in the study had the same name.

car Fish-Eagles and to develop predictive models (>20 cm diameter at breast height [DBH]) near the same bodies of water. To compare nest to identify fish-eagle nesting and perching habitat. and perch trees to available large trees, we randomly selected a reference SiUDY Area and Methods tree for each nest or perch tree. We selected trees at the same distance from the water as the nest or perch tree We conducted the study during the first half of the To do this, we measured with a hip chain the distance Madagascar Fish-Eagle breeding season from 21 May-14 from the nest tree to the nearest water (nest-water dis- August 1994. We investigated fish-eagle nesting and tance), from perch tree to nearest water (perch-water dis- peiching habitat in a 3000 km^ area in the Antsalova re- tance), and the distance along the shore between the gion of western Madagascar (18°40'-19°15'S, 44^15'- nest and perch trees (nest-perch distance). We then ran- 44°50'E) that included the drainages of the Manambolo, domly selected a shoreline reference point on the same Beboka, and Soahanina rivers west of the Bemaraha Pla- body of water as the nest tree that we had measured teau. Topography consisted of coastal plains and low roll- (within 1 .5 km along the banks for nest trees rivers) ing hills with elevations ranging from sea level to 126 m. on To select each nest reference tree, Soils were shallow and sandy, and the vegetation was a we went to the shoreline reference patchwork of dry deciduous forest, savanna, wetlands, point and moved inland a distance equal to the mangrove swamps, and rice paddies. The climate was sub- nest-water distance and selected the nearest humid and tropical with a dry season from April-Octo- tree >20 cm in DBH as our nest reference tree. We used ber and a wet season from November-March. Mean an- the same shoreline reference point to select a perch ref- nual rainfall in the region ranged from 1000-1500 mm erence tree by moving the nest-perch distance in the (Donque 1972). same direction (left or right) along the shoreline as that We defined a nest tree as any tree in which we ob- between the used nest and perch trees. We then moved served nest construction, incubation, or brood rearing. inland the perch-water distance and selected the nearest A nest site was the area within 300 m of the nest tree. A tree >20 cm in DBH as our perch reference tree. We peich tree was any tree in which we observed adult fish- used 20-cm DBH as a minimum size for reference trees eagles perching. We measured nest and perch trees of based on the minimum size of Bald Eagle perch trees on every known Madagascar Fish-Eagle pair in the study area the Chesapeake Bay (Buehler et al. 1992). (Table 1). Our perch-tree sample {N = 29) was larger We measured DBH of nest trees to the nearest cm and than our nest-tree sample (N = 24) because we did not used a clinometer to measure height to the nearest me- find a nest for five of the fish-eagle pairs. ter. We counted branches in the tree canopy that we es- We measured characteristics of fish-eagle nest trees timated to be >5 cm in diameter and unobstructed for and randomly selected reference trees to determine if 1 m above and below. We recorded arc of accessibility by trees used by fish-eagles differed from average large trees standing at the base of the tree and using a compass to December 2002 Mada(;asc]AR Fish-Eagle Nests 289

measure the total arc (0°-360°) that was unobstructed by probability of fish-eagle use of trees and sites based on other trees for an estimated distance of 10 m from the the measured habitat variables using stepwise analysis trunk and 3 m below the tree’s crown (Buehler et al. Our significance level for variables to both enter and exit 1992). We recorded nest-tree species and classified models was P = 0.05. We used dummy variables for growth form following Keister and Anthony (1983). Our growth form categories in the logistic regression (Hos- classification was based on the location of the lowest fork mer and Lemeshow 1989). We constructed classification in the trunk, and whether the tree was dead. We classi- tables for each logistic regression model by using the es- fied growth form as large if the lowest fork was in the timated logistic probabilities for each tree or site to pre- lower third of the trunk, medium if the lowest fork was dict fish-eagle use (Hosmer and Lemeshow 1989). We in the middle third of the trunk, and small if the lowest considered trees or sites as correctly classified as used hy fork was in the upper third of the trunk. We recorded fish-eagles if the predicted probabilities were ^0.5. growth form as dead top if the top third of the crown was dead and as snag if the entire tree was dead and Resui.ts leafless, regardless of the location of the lowest fork in the trunk. Nest-tree Characteristics. Nest construction, in- We measured minimum distance of each nest tree to cubation, or brood rearing was observed at 21 water with a hip chain and minimum distance to human (87.5%) of the 24 measured nest trees in 1994. disturbance, building, road, and fish-eagle nest from The remaining three nest trees were used in 1993, maps and aerial photos. Human disturbances included agricultural clearings, rice paddies, villages, tombs, and but not in 1994. Nest trees were taller, had more fishermen’s camps. Temporary, seasonal shelters that unobstructed branches, and a greater arc of acces- were not used during the fish-eagle breeding season were sibility than reference trees (Table 2). Mean nest- not considered buildings. There were no paved roads tree DBH was more than twice that of reference and few motor vehicles in the area, and the most traveled roads were traversed by less than one motor vehicle per trees. Twenty-two of 24 (91.7%) nest trees versus day, even in the dry season. Oxcarts frequently were used only 14 of 24 (58.3%) reference trees had a >270° to transport materials, so we recorded any oxcart track arc of accessibility. as a road. Nest-tree species included Tamarindus indica {N We considered trees ^6.1 m high and with ^30° ac- = = cessibility from the shoreline to be potential perch trees 7), Cordyla madagascariensis {N 4), Adansonia based on the smallest recorded perch tree used by Bald sp. {N — 2), Colvillea racemosa {N — 2), Neobeguea

Eagles on the Chesapeake Bay (Buehler et al. 1992). We mahafaliensis {N = 2), Acacia sp. {N = 1), Albizia counted perch trees within 50 m of the water along a 250 greveana {N = 1), Alleanthus greveanus {N =1), Foe- m shoreline section centered on the nest tree or refer- tidia sp. {N = 1), Pandanus sp. {N = 1), and un- ence tree (Chandler et al. 1995). We classified mean surrounding canopy height to 5-m intervals ranging from 0- identified {N = 2). T indica was, the most frequent- 25 m based on visual observation. ly recorded species of nest reference tree {N = 6). We measured the perch tree that we saw fish-eagles use Its proportion among nest trees (29.2%) was not most frequently for foraging for each of the 29 fish-eagle different from its proportion among reference pairs in the study area. Eleven (37.9%) of the pairs were - = observed for at least 6 hr, at least once per week during trees (20.8%) (x^ 0.44, df = I, P 0.51). Pro- the breeding season (May-October) in 1992, 1993, and portions of nest trees and reference trees in each 1994 as part of a related study (Watson et al. 1999). The growth form class were similar (x^ — 4.58, df — 4, remaining 18 (62.1%) pairs were observed for at least 6 P — 0.33). Eight of the nest trees (33.3%) and hr, at least three times per breeding season from 1992- three of the reference trees were decidu- 94. We measured the same tree characteristics for perch (12.5%) trees that we measured for nest trees. ous (x^ = 2.95, df = I, P= 0.09). We tested the null hypothesis of no difference between Eish-eagle nest-tree use was positively associated trees or sites used by breeding Madagascar Fish-Eagles with tree height, producing a logistic regression and reference trees or sites for each of the numerical model of variables using the Wilcoxon signed-ranks test. We paired each fish-eagle nest or perch tree with the randomly selected reference tree on the same water body. We did not = test for differences in distance to water because this was 0 1/1+ exp 5.52 - X 0-38x, a criterion for selecting reference trees. We used the chi- square test of equal proportions to determine if fish-eagle habitat use was different from expected use for the fol- where 0 is the probability of fish-eagle use and x, lowing categorical variables: tree species, deciduous ver- is the height of tree i. This model correctly classi- sus evergreen trees, growth form, and surrounding can- fied 83.3% of 48 trees measured. opy height. If >20% of expected values were <5, we used Nest-site Characteristics. Number of shoreline the likelihood ratio chi-square test statistic (Agresti 1990). perch trees was greater at nest sites than at random We developed logistic regression models to predict the sites (Table 3). There was a positive relationship 290 Berkelman et al. VoL. 36, No. 4

Table 2. Characteristics of Madagascar Fish-Eagle nest trees, perch trees, and paired reference trees in the region of Antsalova, Madagascar in 1994.

Paired Paired Reference Reference Nest Trees Trees Perch Trees Trees (V = 24) (N = 24) {N= 29) (N = 29) X ± SE X ± SE X ± SE X ± SE Variable (Range) (Range) pa (Range) (Range) pa

DBH (cm) 87.8 ± 11.8 38.4 ± 4.2 <0.001 65.3 ± 7.2 36.9 ± 3.3 <0.001 (29-245) (22-114) (27-270) (21-120) Height (m) 18.7 ± 0.8 10.5 ± 0.9 <0.001 16.7 ± 0.8 9.8 ± 0.4 <0.001 (10.7-25.9) (5.0-23.3) (9.4-30.3) (4.9-15.8) No. of branches’^ 5.5 ± 0.7 3.2 ± 0.8 0.021 7.9 ± 1.2 1.8 ± 0.4 <0.001 (1-14) (0-19) (2-39) (0-15) Arc of accessibility 346.7 ± 5.4 260.2 ± 25.0 <0.001 336.7 ± 7.1 231.4 ± 21.4 <0.001 (265-360) (0-360) (190-360) (0-360)

* Wilcoxon signed-ranks test significance level. Number of branches in the tree canopy >5 cm in diameter and unobstructed for 1 m above and below. Arc (0°-360°) that was unobstructed by other trees ^10 m of the trunk and ^3 m below the crown (Buehler et al. 1992).

between fish-eagle nest-site use and the number of 1), Adansonia sp. (N = 1), Cedrelopsis grevei {N ~ shoreline perch trees. The model was 1), Pandanus sp. (N — 1), Raphia sp. {N = 1), and unidentified {N — A). T. indica was the most frequently recorded perch reference tree species {N 9 = 1 1 + exp 3.49 - 2 = 10). Its proportion among perch trees (10.3%) was smaller than among reference trees (48.3%) where 0 is the probability of fish-eagle use and (x2 = 5.96, df = 1, P = 0.02). is the number of perch trees within a 1.25 ha (50 Perch trees and reference trees had similar m wide) shoreline section centered on the point growth forms (x^ = 8.04, df = 4, P = 0.09). Pro- on the shoreline nearest nest tree i. Correct clas- portion of deciduous trees among perch trees sification of fish-eagle use for this model was 72.9% (34.5%) was greater than among reference trees of 48 sites. Minimum distance to human distur- (10.3%) (x^ = 4.86, df = 1, P = 0.03). bance, minimum distance to nearest road, mini- There was a positive association between fish-ea- mum distance to nearest building, and minimum gle perch-tree use and tree height, producing a lo- distance to nearest fish-eagle nest did not differ gistic regression model of between nest sites and random sites (Table 3) . The proportion of nest sites in each 5 m canopy height interval did not differ between nest sites and ran- 0 = 1 1 + exp 8.68 2 dom sites (x^ = 4.93, df = 4, P = 0.30). Mean = distance to water of nest trees was 70.8 m (SE where 0 is the probability of fish-eagle use and

12 6, range = 6.8-199.2 m). is the height of tree i. This model correctly classi- Perch-tree Characteristics. Perch trees were larg- fied 84.5% of 58 trees measured. er (DBH and height), had more unobstructed Disclissicjn branches, and had a greater arc of accessibility than reference trees (Table 2). Twenty-six of 29 Nest-tree Use. Madagascar Fish-Eagles used nest (89.7%) nest trees versus only 16 of 29 (55.2%) trees that were taller and had a greater DBH, more reference trees had a >270° arc of accessibility. unobstructed branches, and a greater arc of acces- Perch-tree species included Colvillea racemosa (N sibility than reference trees. The suhstantial differ- — 5), Ficus cocculifolia (N = 4), Neobeguea mahafal- ence between nest trees and reference trees in lensis (N = 3), Tamarindus indica (N = 3), Albizia mean height and DBH suggests that the fish-eagle lebbeck (N — 2), Borassus madagascariensis {N —2), selects nest trees from among the largest trees Cordyla madagascariensis (N = 2), Acacia sp. {N ~ available near water. By placing its nests in the tops December 2002 Madagascar Fish-Eagi.e Nests 291

Table 3. Characteristics of Madagascar Fish-Eagle nest sites {N = 24) and paired reference sites (N — 24) in the region of Antsalova, Madagascar in 1994.

Nest Sites Paired Random Sites x± SE X ± SE Variable (Range) (Range) pa

Minimum distance to human disturbance'^ (km) 0.8 ± 0.2 0.9 ± 0.1 0.742 (0-2.8) (0-2.8) Minimum distance to building (km) 1.8 ± 0.4 1.8 ± 0.3 0.814 (0.1-7.7) (0-5.6) Minimum distance to road (km) 1.7 ± 0.4 1.3 ± 0.3 0.055 (0-8.4) (0-5.4) Minimum distance to fish-eagle nest (km) 4.8 ± 0.9 4.3 ± 0.9 0.104 (1.3-20.3) (0.4-20.1) Number of perch trees'^ 30.8 ± 2.3 16.6 ± 1.9 <0.001 (10-53) (0-33)

Wilcoxon signed-ranks test significance level. '’Human disturbances included agricultural clearings, rice paddies, villages, tombs, and fishermen’s camps. Number of perch trees within a 1.25 ha (50 m wide) shoreline section centered on the point on the shoreline nearest the nest tree We considered trees that we estimated to have a height ^6.1 m and >30° accessibility from the shoreline to be perch trees.

of these trees, it maximizes accessibility and visibil- of the species’ range (Rabarisoa et al. 1997). Al- ity for foraging and territorial defense. These re- though our sample size was limited, the 29 breed- sults were consistent with those reported for other ing sites sampled represent 29.3%, of the 99 known nesting Haliaeetus species (McEwan and Hirth remaining Madagascar Fish-Eagle breeding sites 1979, Andrew and Mosher 1982, Anthony and (Rabarisoa et al. 1997). Bald Eagle management Isaacs 1989, Shiraki 1994). guidelines recommend conserving mature forest Nest-site Use. Number of shoreline perch trees around existing and potential nest sites (Anthony was the only variable that differed between nest et al. 1982, Wood et al. 1989). We offer guidelines sites and random sites. This suggests that the Mad- that are more specific to the range of tree sizes and agascar Fish-Eagle, like the Bald Eagle (Chandler densities found in the tropical dry forest and sa- et al. 1995), may avoid areas without a sufficient vanna habitats that surround the lakes where Mad- number of foraging perches. agascar Fish-Eagles occur. Perch-tree Use. Perch trees were larger in height We recommend that areas with a >32 /ha density and DBH, and had more unobstructed branches, of trees >15 m tall should receive high priority for and had a greater arc of accessibility than refer- Madagascar Fish-Eagle conservation. Probability ence trees. Such trees probably have greater access that a shoreline tree would be used by Madagascar and provide better visibility over water than other Eish-Eagles for nesting or perching can be calcu- trees. This is consistent with Bald Eagle perch-tree lated by inserting tree height into the correspond- use (Stalmaster and Newman 1979, Steenhof et al. ing logistic equation (Fig. 1 ) . Similarly, number of 1980, Buehler et al. 1992). Madagascar Fish-Eagle perch trees along a 1.25 ha (250 X 50 m) shoreline perch trees were more often deciduous than ref- section can be used to estimate the probability that erence trees. In contrast with the nest-tree results, Madagascar Fish-Eagles will use the shoreline sec- the fish-eagles in this study appeared to avoid T. tion for nesting (Eig. 1). These models are best indica for perching. T. indica is evergreen and often used under the conditions that were present dur- has a dense crown; therefore fish-eagles may use ing this study (e.g., same eagle population density, this species less often for perching than leafless same time of year) and apply to eagles nesting on trees or snags. lakes, rivers, and estuaries.

Model Applications. The models we developed Presence of tall trees close to shoreline is the may be used to identify Madagascar Fish-Eagle best predictor of Madagascar Eish-Eagle nest-site nesting and perching habitat along lakes, rivers, use. The eagles often used the tallest trees near and estuaries in western Madagascar. They do not water both for nesting and for foraging perches. apply to a sub-population of at least 16 fish-eagle Rabarisoa et al. (1997) conducted Madagascar pairs that nest on offshore islands at the north end Fish-Eagle surveys from 1991-95, and found areas 292 Berkelman et al. VOE. 36, No. 4

Use Nest-tree Height (m) of

Probability

Perch-tree Height (m)

0 S 10 15 20 25 30 35 40 45 50

No. of Perch Trees

Figure 1. Probability of Madagascar Fi.sb-Eagle use of iiesl trees, perch trees, and nest sites as a I’unclion of nest- tree height (A), perch-tree height (B), and number of shoreline perch trees (C), in the region ol Antsalova Mada- gascar, 1994. Probabilities were calculated by inserting dilferent values of the explanatory variable (tree height or number of perch trees) into the equation resulting from stepwise logistic regression analysis. Dec.ember 2002 Madagascar Fish-Eagle Nests 293 with dense forest adjacent to water that were un- perch habitat on the northern Chesapeake Bay. Wil- son Bull. 104:540-545. occupied by fish-eagles. Watson et al. (1996) are Chandler, S.K., Fraser, D.A. Buehler, developing means to augment the hsh-eagle pop- J.D. andJ.KD. Si:egar. 1995. Perch trees and shoreline development ulation and seek areas of unoccupied fish-eagle as predictors of Bald Eagle distribution on Chesa- habitat where young eagles may be released. Our peake Bay. y. Wildl. Manage. 59:325-332. models may be used both to identify areas of suit- Donque, G. 1972. The climatology of Madagascar. Pages able, but unoccupied, fish-eagle habitat and high 87-144 in R. Battistini and G. Richard-Vindard [Eds ], conservation priority areas of occupied habitat. Biogeography and ecology of Madagascar. Dr. W.Junk The Tsimembo Forest surrounding Lakes Befo- B.V., The Hague, Netherlands. Hosmer, D.W., and S. Lemeshow. 1989. Applied lo- taka, Soamalipo, and Ankerika, where the highest Jr. gistic regression. John Wiley and Sons, New York, NY density of fish-eagles is found (Rabarisoa et al. U.S.A. 1997), should receive highest conservation priority. Keister, G.P., Jr. and R.G. Anthony. 1983. Characteris- The human population density around the lakes tics of Bald Eagle communal roosts in the Klamath low until years large was recent when numbers of Basin, Oregon and California. J. Wildl. Manasce. 47 fishermen began to migrate to the region (Watson 1072-1079. and Rabarisoa 2000). Increased harvesting of tall Langrand, O. and B.-U. Meyburg. 1989. Range, status, and biology of the Madagascar Sea-Eagle Haliaeetus shoreline trees by migrant fishermen will have a vociferoides. Pages 269-277 in B.-U. Meyburg and R.D. negative impact on the fish-eagles. People use the Chancellor [Eds.], Raptors in the modern world. tallest trees available for dugout canoes and build- WWGBP, Berlin, Germany. ing materials (Watson and Rabarisoa 2000) and McEwan, L.C. and D.H. Hirth. 1979. Southern Bald Ea- may prevent regeneration of tall trees by harvest- gle productivity and nest site selection. J. Wildl. Man- ing large amounts of fuel wood to preserve fish by age. 43:585-594. smoke drying. Deforestation probably has already Meyburg, B.-U. 1986. Threatened and near-threatened substantially reduced the amount of fish-eagle hab- birds of prey of the world. Birds Prey Bull. 3:1-12. Nelson, R. and N. Horning. 1993. AVHRR-LAC esti- itat available, and as the human population contin- mates of forest area in Madagascar, 1990. Int.J. Remote ues to increase, available habitat will continue to Sens. 14:1463—1475. decrease unless steps are taken to conserve fish- Newton, I. 1979. Population ecology of raptors. Buteo eagle habitat. Books, Vermillion, SD U.S.A.

Rabarisoa, R., R.T. Watson, R. Thorstrom, and J. Ber- At^KNOWI TDGMENTS kelman. 1997. Status of the Madagascar Fish-Eagle Haliaeetus vociferoides in 1995. OVncA 68:8-12. The Peregrine Fund provided financial and logistical Shiraki, S. 1994. Characteristics of White-tailed Sea-Eagle support for this research. We thank C. Razafimahatratra, nest sites in Hokkaido, Japan. Condor 96:1003-1008 G. Raoelison, J. Mampiandra, and L. Kalavah for help Stalmaster, M.V. and J.R. Newman. 1979. Perch-site pref- with data collection. Thanks to Rajesy, R. Rabarisoa, R. J. erences of wintering Bald Eagles in northwest Wash- I.ewis, P. Ravonjiarisoa, and M. Razafindrakoto for ad- ington./. Wildl. Manage. 43:221-224. ministrative and logistical support in Antananarivo and Steenhof, K., S.S. Berunger, and L.H. Fredrickson. in the field. We thank C.A. Haas, Ney, R.G. Oderwald, J.J. 1980. Habitat use by wintering Bald Eagles in South D.F. Stauffer, R. Thorstrom, R. Tingay, and A.R. Harmata Dakota. J. Wildl. Manage. 44:798-805. for comments on the manuscript. Watson, R.T. and R. Rabarisoa. 2000. Sakalava fishermen and Madagascar Fish-Eagles: enhancing tradi- f ar ERA i t] RE Cited tional conservation rules to control resource abuse that threatens a key breeding area for an endangered AciRESTi, A. 1990. Categorical data analysis. John Wiley eagle. Ostrich 71:2-10. and Sons, New York, NY U.S.A. , S. Razaeindramanana, R. Thorstrom, and S. Ra- Andrew, J.M. and J.A. Mosher. 1982. Bald Eagle nest site FANOMEZANTSOA. 1999. Breeding biology, extra-pair selection and nesting habitat in Maryland. J. Wildl. birds, productivity, siblicide, and conservation of the Manage. 46:383-390. Madagascar Fish-Eagle. Ostrich 70:105-111. Anthony, R.G. and F.B. Isaacs. 1989. Characteristics of , S. Tiiomsett, D. O’Daniel, and R. Lewis. 1996 Bald Eagle nest sites in Oregon. Wildl. Manage. 53: J. Breeding, growth, development, and management of 148-159. the Madagascar Fish-Eagle {Haliaeetus vociferoides) J , R.L. Knight, G.T. Ai.ien, B.R. McClelland, and Raptor Rei 30:21-27. J.I. Hodges. 1982. Habitat use by nesting and roosting Wood, P.B., T.C. Edwards, Jr., and M.W. Collopy. 1989. Bald Eagles in the Pacific Northwest. Trans. N. Am. Characteristics of Bald Eagle nesting habitat in Flori- Wildl. Nat. Resour. Conf. 47:382-390. da. /. Wildl. Manage. 53:441-449. Buehler, D.A., S.K. Chandler, T.J. Meicsmann, J.D. Fras- er, AND J.K.D. Seegar. 1992. Nonbreeding Bald Eagle Received 30 November 2001; accepted 9 July 2002 J. Raptor Res. 36(4);294-299 © 2002 The Raptor Research Foundation, Inc.

USE OF VEGETATIVE STRUCTURE BY POWERFUL OWLS IN OUTER URBAN MELBOURNE, VICTORIA, AUSTRALIA— IMPLICATIONS FOR MANAGEMENT

Raylene Cooke and Robert Wallis^ School of Ecology and Environment, Deakin University, Warrnambool Campus, Warrnambool, 3280 Australia

John White School of Ecology and Environment, Deakin University, Melbourne Campus, Burwood, 3125 Australia

Abstract.—The Powerful Owl (Ninox strenua) is Australia’s largest owl and is considered of least concern nationally. Although a number of studies have reported on the ecology of Powerful Owls inhabiting forests, few have focused on these owls living in urban areas. We report on the characteristics of different roost trees used by Powerful Owls in a continuum of habitats from urban Melbourne to the more forested outskirts. Records of weather conditions and daily temperatures were also analyzed to determine whether the owls were selecting particular roost trees for specific climatic conditions. We found that roost-tree height and perch height was highly correlated, with the owls always roosting in the top one-third of the tree, regardless of the tree height. As ambient temperatnre increased perch height decreased, and vice-versa, but owls always roosted in the top one-third of the roost tree. Powerful Owls did not simply move up and down the one tree, but moved to more suitable trees according to the weather conditions. Hence, the species requires a structurally heterogeneous habitat to provide roost trees for different temperatures. Eurtherraore, successful management of this species in the future will require the protection of structurally diverse vegetation.

Key Words: Powerful Owl, Ninox strenua; disturbance, management, temperature, urbanization-, vegetation struc-

ture.

USO DE LA ESTRUCTURA VEGETATIVA POR NINOX STRENUA EN EXTERIORES URBANOS DE MELBOURNE, VICTORIA, AUSTRALIA—IMPLICACIONES PARA EL MANEJO

Resumen.—Ninox strenua es el biiho mas grande de Australia y es considerado nacionalmente de rnenor interes. Aunque un numero de estudios se han concentrado en su ecologia en bosques, pocos se han enfocado sobre los que habitan en areas urbanas. Reportamos las caracterlsticas del uso de diferentes arboles percha utilizados por Ninox strenua en un continuum de habitats desde el Melbourne urbano hasta los alrededores mas boscosos. Adicionalmente se analizaron los registros de condiciones climaticas

y temperaturas diarias para determinar si los buhos estaban seleccionando arboles percha particulares debido a condiciones climaticas especificas. Encontramos que la altura de los arboles percha y la altura de la percha utilizada estaba altamente correlacionados con el uso del tercio mas alto del arbol, sin tener en cuenta la altura del arbol. Cuando la temperatura ambiente incrementaba la altura de la percha

decrecia, y viceversa, pero los buhos siempre percharon en el tercio mas alto del arbol percha. Los buhos no se movieron simplemente hacia arriba y ab:qo del arbol, sino que se movieron a arboles mas adecuados de acuerdo a las condiciones climaticas. Por lo tanto, la espccie requierc un habitat estructuralmente heterogeneo que provea arboles perchas para diferentes temperaturas. Ademas de esto, el manejo exitoso de esta especie en el futuro requiere de la proteccion de vegetacion estructuralmente diversa. [Traduccion de Cesar Marquez]

The Powerful Owl {Ninox strenua) is the largest of up to 1700 g (Higgins 1999). The Powerful Owl Australian owl. The male is slightly larger than the is a nocturnal predator, with a diet consisting al- female, growing to a length of 65 cm with a mass most exclusively of medium-sized, arboreal, mar-

supial prey (Webster et al. 1999, Cooke et al. 2002).

^ E-mail address: [email protected] The Powerful Owl is classified nationally as of

294 ,

December 2002 The Powfrfue Owe in Urban Environments 295

“least concern” (rated nationally of conservation Yarra Valley Metropolitan Park (100 ha) and Warrandyte State Park (586 ha), which were urban parklands man- significance, but at the lowest level, Garnett and aged for public recreation and 18 km and 24 km north- Crowley 2000) occurring at low densities in south- , east of central Melbourne, respectively. Both parks have eastern continental Australia. Within the state of been extensively modified in the past and now consist ot Victoria the species is listed as endangered (De- riparian areas and the occasional patch of remnant trees partment of Natural Resources and Environment, surrounded fry a matrix of revegetated woodlands. The next three sites along the continuum were One Victoria 1999) and threatened within the Greater Tree Hill Reserve (143 ha), Smiths Gully (2.4 ha), and Melbourne Area (Mansergh et al. 1989). Estimates Steels Creek (21600 ha). One Tree Hill Reserve and of population numbers in the state of Victoria are Smiths Gully are both located 35 km from central Mel- less than 500 pairs across the state (Garnett and bourne while Steels Creek is located 65 km from Mel- Crowley 2000). bourne. These three sites are all dry, open forests and consist primarily of different Eucalyptus spp. as upper can- The Powerful Owl was once considered to be a opy trees with Acacia spp. dominating the middle story. specialist in ecological terms because of its appar- These three sites are also regularly visited by people and ently restricted habitat and dietary requirements also show signs of disturbance. (Fleay 1968, Seebeck 1976, Roberts 1977), indicat- The sixth site along our continuum was Toolangi State Forest is located northeast of ing that it is vulnerable to habitat modihcation and (35 000 ha), which 80 km Melbourne. This forest is a relatively undisturbed wet that it has specific conservation needs. Recent sclerophyll forest dominated by mountain ash {Eucalyptwi studies, however, have contested these earlier find- regnans). Middle story species are less common in this ings and consequently have questioned the degree area; however, the understory is dominated by various to which the Powerful Owl is vulnerable to habitat ferns and bracken. modification and disturbance (Debus and Chafer Methods 1994, Kavanagh and Bamkin 1994, Pavey et al.

1994, Cooke et al. 1997, Cooke et al. 2002). A total of 1300 day visits were made to the six study Urban and suburban areas surrounding Mel- sites between 1996-99. During these visits the roost tree in which the Powerful Owl was located was recorded bourne have been mostly cleared throughout the Roost trees were those in which Powerful Owls spent time past 100 years, with only small patches of remnant during the daylight hours. vegetation remaining. Surprisingly, Powerful Owls Here, we examined the different roost trees used by still remain in some urban areas, with one known the Powerful Owl at each of the study sites and the characteristics of each tree These included the species breeding pair located only 18 km from central Mel- used. of tree, tree height, and the diameter at breast height bourne. Powerful Owls have also been recorded (DBH). Records of weather conditions and daily temper- living in close proximity to other Australian cities, atures were also analyzed to determine whether the owls including Brisbane (Pavey et al. 1994, Pavey 1995) are selecting particular roost trees for specific climatic and Sydney (Rose 1993). Tittle research has been conditions. Each study site was visited at least once weekly over a undertaken to determine the resources these owls 4-yr period and each roost tree was examined for the require for long-term survival in urban environ- presence of the Powerful Owl or evidence that an owl ments. Here, we describe roost tree characteristics had used the tree recently. Evidence of usage included and features of roosts used in urban and suburban fresh whitewash (excreta) or regurgitated food pellets areas by Powerful Owls. Results from this study are Temperature and weather conditions were noted, regurgitated food pellets were collected and, in situations then used to identify management options for Pow- where the Powerful Owl was using the roost tree, the erful Owls in urban areas. The results of this study perch height was measured using a clinometer. may also provide valuable information for the future management of other top-order raptors with Resutts similar ecological attributes in urban areas. The Powerful Owls used 179 individual roost Study Areas trees at the six study sites. Twenty different tree species were used as roost trees. The main trees During this study, we examined how Powerful Owls used the structure of vegetation in a continuum of en- used for roosting were Eucalyptus spp. (54%), Aca- vironments ranging from urban Melbourne (two sites), cia spp. (18%), and Leptospermum spp. (15%). Oth- through the urban fringe (three sites), and into more er roost trees were hazel pomaderris {Pomaderns forested areas (one site). Each site was selected on the aspera), the introduced Monterey pine {Pinus ra- basis that it had a confirmed breeding pair of owls pres- diata) cherry ballart (Exocarpos cupressiformis ent for several years. , ) The two sites located closest to Melbourne were the Christmas bush {Prostanthera lasianthos), the non- 296 Cooke et al. VoL. 36, No. 4

Table 1. Roost-tree characteristics at each of the six study sites. Values represent mean ± 1.96 SE.

Tree Height Perch Height Site N m) DBH (cm) m) ( (

Yarra Valley Metropolitan Park 22 15.7 ± 2.2 55.0 ± 12.2 10.2 ± 1.9 Warrandyte 29 13.3 ± 2.3 40.3 ± 11.3 9.6 ± 2.0 One Tree Hill 22 16.2 ± 1.9 48.8 ± 10.0 12.2 ± 1.9 Smiths Gully 24 12,7 ± 1.8 37.1 ± 9.7 8.1 ± 1.1 Steels Creek 23 16.1 ± 2.2 38.5 ± 5.0 10.3 ± 1.9 Toolangi 59 13.0 ± 2.1 49.7 ± 9.6 11.2 ± 1.8

Pooled data 179 14.4 ± 0.9 45.6 ± 4.4 10.4 ± 0.8

indigenous sweet pittosporum (Pittosporum undu- Given the variety of tree species used by the owls latum), and swamp paperbark {Melaleuca ericifolia). for roosting, we decided to determine whether the To determine whether the dimensions of roost roost trees were being used in a similar fashion trees varied between sites we compared the tree among sites. Specifically, the relationship between height, roost height, and DBH of roost trees at perch height and tree height was examined. Over- each site (Table 1). Roost tree heights were not all, perch height was positively correlated with tree different among the six study sites (T5 173 = 1.856, height (r = 0.91, P < 0.001, N = 179). Hence, P = 0.104), with the mean height of roost trees although the species of roost tree varied, the owls being 14.4 m ± 0.9 m (±1.96 SE). Perch heights tended to perch toward the top of the selected between the six study sites also did not differ sig- roost tree. The perch height as a proportion of nificantly (fy = 173 = 1.643, P 0.15), with the mean tree height varied significantly between sites (E5 173 perch height being 10.4 m ± 0.8 m (±1.96 SE). = 17.76, P < 0.001). Perch heights at the Yarra There was also no significant difference in the Valley Metropolitan Park, Warrandyte State Park, DBH of the roost trees between the six study sites Smiths Gully, and Steels Creek were lower within “ — (^5 ,i 7 s 1.52, P 0.186). Overall, the mean DBH the roost trees than those in Toolangi State Forest was 45.6 cm ± 4.4 cm (mean ± 1.96 SE). These (Student Newman-Keuls test, P < 0.05; Fig. 1). results suggest that the trees used for roosting have Although the mean perch height as a proportion similar physical dimensions at each site even of the tree height varied among sites, roost tree though the tree species may differ between sites. height was a predictor of perch height within each

site (Fig. 2). High values at all sites (except Smiths Gully) suggest that there was a strong and 0.90 consistent relationship between perch height and 01 0.85 '5 tree height (Table 2). z $ 0.80 To further understand this relationship, a com-

o 0.75 parison was made between perch height and different temperature and weather conditions. When % 0.70 Q. there was no precipitation a strong negative asso- & 0. 0.65 n ciation between temperature and perch height was " 0.60 found (Table 3), with the owls at all sites choosing lower perch heights as the temperature increased. i 0.55 £ On days where rainfall occurred this trend was less ® 0.50 0. YVMP One Tree Hill Steels Creek evident, with the owls at most sites showing no con- Warrandyte Smiths Gully Toolangi sistent association between perch height and tem- Site perature (Table 3). Figure 1. Perch heights as a proportion of tree heights

1 1.96 SE) at each the six study sites. (mean ± and of Discussion Plots with the same letters indicate homogeneous groups as revealed by the Student Newman-Keuls (P < 0.05). The Powerful Owls inhabiting the six study sites YVMP = Yarra Valley Metropolitan Park. used 179 roost trees. Of these, 87% were from only December 2002 The Powereul Owl in Urban Environments 297

Yarra Valley Metropolitan Park Warrandyte State Park Perch height = -1.78 + 0.76 * tree height Perch height = -1.05 + 0.80 * tree height

(m)

Height

Perch

One T ree Hill Reserve Smiths Gully Perch height » -2.48 + 0.90 * tree height Perch height = 2.51 + 0.44 * tree height

(m)

Height

Perch

Tree Height (m)

Steels Creek Toolangi State Forest Perch height = -1.66 + 0.74 * tree height Perch height = -0.38 + 0.89 * tree height

(m)

Height

Perch

Figure 2. The relationship between perch height and tree height at each of the six study sites. Lines indicate the regression lines with 95% confidence limits. 298 Cooke ei ai.. VoL. 36, No. 4

Table 2. Regression results of the relationship between eralists in terms of the tree species in which they perch height and tree height at all sites. will roost. The fact that the roost tree characteris-

tics (e.g., perch height, DBH) were similar at all Site B? df F P sites suggested that there was some degree of selection of individual trees that offer optimal roost Yarra Valley characteristics. This was particularly highlighted Metropolitan Park 0.844 1, 20 114.71 <0.001* by Warrandyte 0.859 1,27 171.34 <0.001* the relatively small number of roost trees used at

One Tree Hill 0.825 1, 20 100.33 <0.001* each site compared with the number of trees avail- Smiths Gully 0.463 1, 22 20.84 <0.001* able. Steels Creek 0.718 1, 21 56.89 <0.001* When temperature and weather conditions were Toolangi 0.980 57 2792.09 <0.001* 1, considered in relation to roost tree usage, the re- * Represents a significant relationship between perch height and sults suggested that as temperature increased tree height. perch height decreased, and vice-versa. On hot days. Powerful Owls were roosting lower in shadier sites and on cooler days they roost at higher levels, three different genera, Eucalyptus (54%), Acacia possibly to absorb sunlight. However, independent (18%), and Leplospermum (15%). The other 13% of the height of the roost tree the Powerful Owls of roost trees consisted of a variety of genera that still roosted in the top one-third of the roost tree. were infrequently used by Powerful Owls. Overall, This result suggests that they require habitats with Powerful Owls roosted in 20 different tree species a large degree of structural variation to provide at the six study sites and in most cases the roost roost trees for different temperatures. trees used were the most common species at the The choice of roost trees used by the Powerful specific study site. This indicates that the Powerful Owls in clear and rainy conditions was also exam- Owls in the Yarra Valley corridor are probably us- ined. that signif- ing abundant and available tree species rather than The results showed there was no icant difference in the perch height used by the selecting less common species. Roost tree characteristics such as height, perch Powerful Owls at five of the six sites on wet days. pattern. height, and DBH did not differ between the six Steels Creek was the only exception to this slightly sites. Roost tree height and perch height, however, At most sites, Powerful Owls roosted in low- were highly correlated, indicating a direct relation- er trees on rainy days. However, at Steels Creek the ship between the height of the roost tree and the Powerful Owls actually roosted in taller, canopy perch height. Powerful Owls observed at all six trees on precipitation days. Thus, it would appear sites generally roosted in the top one-third of the that the height at which Powerful Owls roost in roost tree, regardless of the tree height. different weather conditions was not as important Overall, these results suggested that Powerful as the amount of canopy cover provided by the Owls roosted in a number of tree species and they specific roost tree. were most likely found in the most common tree Results from this study also suggest that the species. It is probable that Powerful Owls are gen- structural diversity within a site is important, given

Table 3. Correlation rc.sults from comparisons of perch height and temperature on days with and without precipitation.

No PrECIEI J AI ION PRKCtEITAlION

Site r-VAt.t.iE P-VAITIE r-VAt.UE P-VAl.UE

Yarra Valley Metropolitan Park -0.80 <0.001* -0.03 0.875 Warrandyte -0.27 0.021* 0.06 0.714 One Tree Hill -0.87 <0.001* -0.06 0.065 Smiths Gully -0.68 <0.001* -0.39 0.006* Steels Greek -0.45 <0.001* 0.62 <0.001* Toolangi -0.59 <0.001* -0.18 0.112

* Represents a significant relationship between perch height and temperature. .

December 2002 The Powerful Owl in Urban Environments 299 that the Powerful Owls may use trees of different er Melbourne, Victoria. Pages 100-106 in I. Newton, R. Kavanagh, Olsen, and I. Taylor [Eds.], Ecology heights to regulate their temperature in relation to J. and conservation of owls. CSIRO Publishing, Mel- climatic conditions. Unfortunately environmental bourne, Australia. change accompanying urbanization often results in Debus, S.J.S. and C.J. Chafer. 1994. The Powerful Owl less structural diversity in vegetation, which can Ninox strenua in New South Wales. Aust. Birds (Sup- Powerful Owls have less choice in suit- mean that plement) 28:20-38. able thermal environments. What effect loss of Department of Natural Resources and Environment, structure will have on survival and reproduction is Victoria, 1999. Powerful Owl Ninox strenua. Flora and largely unknown, but it may in part explain why fauna guarantee act. Department of Natural Resourc- the Powerful Owl is rarely found in highly-urban- es and Environment, Melbourne, Australia. ized areas. Fleay, D. 1968. Nightwatchmen of bush and plain. Jaca- randa Press, Brisbane, Australia. This information is important for future man- Garnett, S.T and G.M. Crowity. 2000. The action plan agement of the Powerful Owl because it suggests for Australian birds. Canberra: Environment Austra- that this species does not simply move to higher or lia, Australian Government. Canberra, Australia. lower branches in the one tree; rather, it moves to Higgins, PJ- 1999. Handbook of Australian, New Zealand an alternative roost tree with more suitable struc- and Antarctic birds. Vol. 4. Oxford Univ. Press, Mel- tural characteristics when it changes heights. bourne, Australia. Therefore, management of the vegetation in the Kavanagh, R.P. and K.L. Bamkin. 1994. Distribution of urban areas must ensure that there is structural nocturnal forest birds and mammals in relation to the diversity in the vegetation. Currently, the focus of logging mosaic in south-eastern New South Wales vegetation management for the Powerful Owl has Biol. Conserv. 71:41-53. S. Bennett, R. Brereton, been on maintaining old eucalypts (canopy layer) Mansergh, I.C., C. Beardsell, K. O’Conner, K. Sandiford, and M. Schulz. 1989. However, this may not provide for the structural Report on the sites of zoological significance in the resource requirements of this species. Vegetation Upper Yarra Valley (western section) and Dandenong management for the Powerful Owls should, there- Ranges. Arthur Rylah Institute for Environmental Re- fore, be expanded to include the obviously impor- search, Tech. Rep. Ser. No. 90, Melbourne, Australia tant mid-story species such as Acacia and Leptosper- Pavey, C.R. 1995. Food of the Powerful Owl Ninox strenua mum. in suburban Brisbane, Queensland. Emu 95:231-232.

, A.K. Smyth, and Mathieson. 1994. The breed- Acknowledgments J. ing season diet of the Powerful Owl Ninox strenua at We thank Alan Webster for his on-site help, particularly Brisbane, Queensland. Emu 94:278-284. for providing historical records, and for continual sup- Roberts, G.J. 1977. Birds and conservation in Queens- port and other assistance. We also thank the Holsworth land. Sunbird 8:73—82. Wildlife Research Fund, the M.A. Ingram Trust, Birds Rose, A.B. 1993. Notes on the Powerful Owl Ninox strenua Australia, and Deakin University for providing financial South Wales. Aust. Birds 26:134—136. support. We also wish to acknowledge the constructive in New suggestions provided by referees of this manuscript. Seebeck, J.H. 1976. The diet of the Powerful Owl Ninox strenua in western Victoria. Emu 76:167-170. Literature cited Webster, A., R. Cooke, G. Jameson, and R. Wallis. 1999 Diet, roosts, and breeding of Powerful Owls Ninox Cooke, R., R. Wallis, A. Webster, and J. Wilson. 1997. Diet of a family of Powerful Owls Ninox strenua from strenua in a disturbed, urban environment: a case for Warrandyte, Victoria. Proc. R. Soc. Vic. 107:1—6. cannibalism? Or a case for infanticide? Emu 99:80—83.

, R. Wallis, and A. Webster. 2002. Urbanization and the ecology of Powerful Owls Ninox strenua in out- Received 31 December 2001; accepted 7 August 2002 / Raptor Res. 36(4) :300-308 © 2002 The Raptor Research Foundation, Inc.

NEST-SITE SELECTION OF THE CROWNED HAWK-EAGLE IN THE FORESTS OF KWAZULU-NATAL, SOUTH AFRICA, AND TAI, IVORY COAST Gerard Malan^ School of Life and Environmental Sciences, University of Durban-Westville, PB X5400f Durban 4000, South Africa SusANNE Shultz Population and Evolutionary Biology Research Group, School of Biology, Nicholson Building, University of Liverpool, Liverpool L69 3 GS, United Kingdom

Abstract.—Structural characteristics of Crowned Hawk-Eagle {Stephanoaetus coronatus) nest sites were compared between forests in KwaZulu-Natal province, South Africa, and the Tai National Park, Ivory Coast, and key features of nesting trees and nest-placement sites were identified. Nest-tree heights and nest heights differed appreciably between three tree groups with the highest being indigenous Tai trees (x tree height = 52 m and x nest height = 36 m, N = 8 nests), followed by exotic eucalyptus (x = 44 and 22 m respectively, N = 10) and indigenous trees (x = 24 and 14 m respectively, N = 17) from KwaZulu-Natal. All the nest trees in Tai were eraergents, whereas 11 of 17 indigenous nest trees and only two of 10 eucalyptus were so in KwaZulu-Natal. Non-emergent eucalyptus nest trees were predominantly edge trees that may have provided easier access for flying eagles. Overall, nest forks were more accessible for flying eagles than random forks, although access did not differ between nests located in emergent and non-emergent trees. Crowned Hawk-Eagles transport long sticks and heavy prey items to their nests and access was probably the most critical feature of both the nest tree and placement of the nest. Wildlife managers must, therefore, ensure that lone-standing or emergent trees are cultivated and conserved, and flight paths to nests are kept open to allow Crowned Hawk-Eagles continued and easy access to their nests.

Key Words: Crowned Hawk-Eagle, Stephanoaetus coronatus; nest access; emergent trees; nest-site selection; wildlife management.

SELECCION DEL SITIO NIDO DEL AGUILA CORONADA EN LOS BOSQUES DE KWAZULU-NATAL, SUR AFRICA, Y TAI, COSTA DE MARFIL

Resumen.—Las caracteristicas estructurales de los sitios nido de las aguilas coronadas {Stephanoaetus coronatus) fueron comparadas entre los bosques de la provincia KwaZulu-Natal, Sur Africa, y el parque nacional Tai, Costa de Marfil, y se identilicaron los rasgos claves de los arboles nido y de los sitios de ubicacidn de los nidos. Las alturas de los arboles nido y las alturas de los nidos difirieron apreciable- = mente entre arbol y grupo de arboles siendo los mas altos los nativos Tai (x altura del arbol 52 m y X altura del nido = 36 m, N = 8 nidos), seguido por eucaliptos exoticos (x = 44 y 22 m respectivamente, ~ = N 10) y arboles nativos (x = 24 y 14 m respectivamente, N 17) de KwaZulu-Natal. Los arboles nido de eucaliptos no emergen tes fueron predominantemente arbcdes de borde que podian proveer mas facil acceso a las aguilas en vuelo. En conjunto, las horquelas en nidos fueron mas accesibles para las aguilas que horquetas colocadas al azar, aunque el acceso no dilirio entre los nidos colocados en arboles

emergentes y no emergentes. Las aguilas coronadas transportan grandes ramas y presas pesadas a sus nidos y probablementc el acceso fue el rasgo mas critico tanto para la seleccion del arbol nido como para la ubicacion del nido. Los manejadores de vida silvestre deben, por lo tanto, asegurar que arboles aislados o emergentes son cultivados y conservados, y que las vias de vuelo a esos nidos permaneceran abiertas para permitir a las aguilas coronadas continuo y facil acceso a sus nidos. [Traduccion de (iesar Marquez]

Tree-nesting raptors select nesting trees and nest hide the nest from potential predators, insulate the sites on the basis of certain structural features that nest against adverse weather conditions, place the birds close to their hunting habitats and allow them easy access to the nest (Moore and Henny ^ Present address: Department of Nature Conservation, Pretoria Technikon, P.B. X680, Pretoria 0001, South Af- 1983, Speiser and Bosakowski 1987, Lilieholm et rica; e-mail address: [email protected] al. 1993, Burton et al. 1994, Selas 1996, Malan and

300 December 2002 Nest-seee Selection oe the Crowned Hawk-Eagle 301

Robinson 2001). Larger raptors often nest in an in addition to indigenous trees, consisting of most- exposed position that allows easy access to and ly White Stinkwoods ( Celtis africana) (Tarboton and from the nest to deliver long sticks and heavy prey Allan 1984, Boshoff 1988).

(Speiser and Bosakowski 1987, Burton et al. 1994). The objective of this study was to compare To further facilitate access, large raptors nest in tall Crowned Hawk-Eagle nesting sites in three tree emergent trees or large trees with open branch groups and to use this information to provide re- structures that respectively allow them access to the source managers with silvicultural guidelines for nest both above and within the canopy (Moore and providing nest-placement sites and stands for

Henny 1983, Burton et al. 1994, Malan and Rob- Crowned Hawk-Eagles. As the forests in the inson 2001). Unfortunately, these preferences KwaZulu-Natal province. South Africa, are relative- bring large eagles in direct conflict with man as ly small in size and patehy in distribution (Boshoff large trees often are selectively harvested for com- 1997, Midgley et al. 1997), nest site characteristics mercial and subsistence purposes (Bijleveld 1974, of these forests were compared with those from the Watson and Rabarisoa 2000). extensive and continuous, indigenous forest of the In the predominantly arid South Africa, the de- Tai National Park, Ivory Coast. These comparisons pletion of indigenous forest habitats and the arriv- clarify which structural features are most important al of commercial exotic Eucalyptus, Pinus, Acacia, when selecting a nest site, and how flexible and Populus trees have had a mixed impact on the Crowned Hawk-Eagles are with regard to these abundance and distribution of tree-nesting forest characteristics. Second, for KwaZulu-Natal, we ex- birds (Low and Rebelo 1996, Allan et al. 1997). amine stand size to determine the minimal habitat Although by 1997 the area under commercial pulp- requirements and compare topographical features wood and sawlog plantations (15 186 km^) was four with randomly-selected sites to determine the ea- times larger than the existing natural forests (Van gle’s selectivity for these features. der Zel Anon. the very short rotation 1996, 1998), Study Areas intervals of plantations (8-16 yr) do not allow the In South Africa, Crowned Hawk-Eagle nest sites were trees to attain the size necessary to support large located for study during forest surveys in the KwaZulu- stick nests. However, isolated, non-commercial Natal (29°S, 31°E). Indigenous tree stands were surveyed stands of large exotic trees are used for nesting by in forests characterized by a 10-25 m high canopy, distinct vegetation strata and numerous dominant tree spe- indigenous birds, including raptors (Steyn 1977, cies (Low and Rebelo 1996, Midgley et al. 1997). The Macdonald 1986, Malan and Robinson 2001). In mean annual rainfall in these forests range from 900- indigenous forests, the processes of deforestation, 1500 mm. Indigenous nest trees were sampled in the Or- forest fragmentation, and the selective removal of ibi Gorge, Vernon Crookes, Krantzkloof, Harold John- son, and Dlinza Eorest nature reserves, Ithala Game big trees from remnant patches alter the size, struc- Reserve, Hluhluwe-Umfolozi Park, all areas managed by ture, and availability of indigenous trees for nest- the KwaZulu-Natal Wildlife, and the Umgeni Valley Na- ing (Tarboton and Allan 1984, Allan and Tarboton ture Reserve and Tanglewood Natural Heritage Site. Ex- 1985, Seydack 1995, Vermeulen 1999). otic eucalyptus were surveyed in abandoned plantations, self-sown stands, and planted trees in large domestic gar- In South Africa, the Crowned Hawk-Eagle {Ste- dens, but none were known from commercial sawlog or coronatus) recently of for- phanoaetus has become pulpwood plantations. mal conservation concern and the status of the In the Ivory Coast, all nest sites were located within a species has changed to near threatened due to the 50 km^ area around the Station de la Recherche en Ecol- ogie Tropicale (SRET, 7°00'N, 5°50'W) near the western loss of its previously suitable, indigenous nesting edge of the park. The Tai National Park is the largest habitat to short rotation, exotic plantations continuous lowland forest in West Africa (454 000 ha)

(Barnes 2000) . Throughout much of its range, the and contains the last sizeable protected habitat for a Crowned Hawk-Eagle breeds in tall evergreen for- number of Upper Guinea Forest endemics (Gartshore et al. annual rainfall at the research sta- ests but can also nest in deciduous forests and 1995). The mean tion is 1800 mm. The forest was selectively logged in the woodland-forest mosaics (Tarboton and Allan early 1970s, but the structure is essentially indistinguish- forest trees for 1984). These birds prefer large able from a primary forest. The main forest canopy is nesting and the nest is usually situated in a major 30-40 m in height, with emergent trees reaching to over fork, 8-30 m above ground but can be as high as 60 m (Guillaumet 1994). 46 m (Steyn 1982, Tarboton and Allan 1984, Brown Methods and Amadon 1989). In South Africa, Crowned The authors and conservation ofhcers located 27 Hawk-Eagles nest in exotic eucalyptus and pines, Growned Hawk-Eagle nests in KwaZulu-Natal and eight 302 Malan and Shultz VoL. 36, No. 4

m Tai. Of the nests in KwaZulu-Natal, 19 were found by graph with 50 m contour lines) to calculate stand size listening for the loud queee-queee soliciting calls of nest- and shape. From this photo, the maximum length (A) lings or by spotting large nests (Steyn 1982). Although and maximum width (B; perpendicular to the maximum this non-systematic search method may bias the sample length axis) of the nest stand was measured. All mea- toward accessible and conspicuous nests (Daw et al. surements from 1:10 000 orthophotos were rounded to 1998), the nest-site data include nests from a wide selec- 10 m to allow for a 1 mm measurement error. Stand tion of forest and nest-tree types. Sampled nest trees were shape (S) was defined as the maximum stand width di- located in indigenous forests, exotic monocultures, and vided by the maximum length, with values ranging from mixed forests, and nest tree species were grouped into one (square shape) to zero (elongated shape). Nest stand either indigenous or eucalyptus stands. shapes were grouped into square (Shape ^0.5) or elon- The following nest-tree characteristics were recorded gated (Shape <0.5). The surface area of planted forests from each nest site: the tree diameter at breast height was calculated from orthophotos by measuring the stand (14 m, DBH) of all stems >22 cm in diameter; tree lengths and widths. The surface area of indigenous forest height (T), nest height (N), height of the first foliage, stands could not be calculated from orthophotos because and the height of the first side branch (R, irrespective if the edges of indigenous forests were not defined clearly

It was dead or alive) . All height measurements were taken and the surface area was, therefore, estimated as S = (A/ with a clinometer. For trees with buttresses {N = 3), the 2)(B/2)(tt). From the orthophotos, the nest trees were circumference of the tree, including the buttresses, was also categorized as being located on the edge of the stand measured at breast height, a diameter calculated and di- (i.e., the first tree encountered on the edge of a forest vided by two as to provide a conservative estimate of stand). Lastly, distances to water, road, and nearest hu- DBH. The percent nest height was the proportional dis- man habitation were measured from the nest tree and tance the nest was placed from the top of the tree ((N/ one random tree selected from each nest stand. T)100) and the percent first branch height was the pro- All data were subjected to the Kolmogorov-Smirnov portional height the first branch was placed from the top one-sample test of normality. If the distribution of the of the tree ((R/T)100). data was found to be non-normal, the non-parametric Nests were classified as being placed within or below Kruskal-Wallis test or Mann-Whitney Latest was employed the foliage. Each nest was scored as either being posi- The Tukey honest significant difference test for unequal tioned in a main fork, against the main branch (i.e., pri- sample sizes was employed to determine which groups mary axis, mainly vertical), or on a side branch (i.e., sec- are particularly different from each other after a signifi- ondary axes, mainly horizontal). The number of cant Kruskal-Wallis test was obtained from the Analysis of branches supporting the nest was also counted. Lastly, Variance. The Pearson’s Chi-square test was used to test the nest tree was classified as emergent if the branch and for patterns with categorical variables. All data were an- foliage structure protruded above the surrounding for- alyzed using the Statistica software package (StatSoft est. 1995) and probability levels were set at a = 0.05. For each nest tree, we identified large and open forks, excluding the nest fork, which could possibly support a Results Crowned Hawk-Eagle nest that was 2 m wide and 2.5 m Of the 35 Crowned Hawk-Eagle nests analyzed, deep (Steyn 1982). Each of these forks was categorized as being positioned in a central fork or crotch (i.e., be- 10 were located in eucalyptus and 17 in indigenous tween main branches), as against the main branch, or on trees in KwaZulu-Natal, and eight in indigenous a side branch, and numbered from tree bottom to top. trees in Tai. Indigenous nest trees identified in A random fork was selected from the category of the fork KwaZulu-Natal included Ficus spp. (7), Chrysophyl- that supported the nest (i.e., if the nest was against a lum viridifolium Syzygium cordatum Cussonia main branch, the random fork was selected from similar (3), (2), forks). If the random fork was not available from the spicala, Scholia brachypetala, and Celtis africana. The category that supported the nest, it was selected from a exotic nest trees were all eucalyptus. Nest trees combined sample of the remaining two positions. identified in Tai included Lofira alata, Klainodoxa For each cardinal direction (N, E, S, and W), accessi- gabonesis, Ceiba pentandra, and Alstonia boonei. bility of the nests and random forks were determined by All tree characteristics differed whether the flying eagle would have a 30 m unobstructed measured among approach on a horizontal plane. For a flying eagle, a the three tree groups (Table 1). Tai and eucalyptus flight path to the nest obstructed by foliage and/or nest trees were taller than KwaZulu-Natal’s indige- branches thus qualified inaccessibility. nous trees. Tai nest trees were larger in diameter, We sampled characteristics of the three trees closest to and had higher first foliage, side branches and per- the nest tree. The distance from the nest tree to each surrounding tree was measured. We calculated the mean cent first side branch heights than trees from area occupied by the trees by squaring the mean distance KwaZulu-Natal. Nest heights differed among all of the three trees from the nest tree. We then converted three tree groups, and the percent nest heights the result to the number of trees per hectare and cal- were lower in eucalyptus than Tai nests (Table 1). culated a tree density estimate at the nest tree (Phillips The number of branches that supported nests 1959). For KwaZulu-Natal nest trees, each nest was plotted on did not differ among tree groups (Kruskal-Wallis a 1:10 000 orthophoto (black and white aerial photo- ^2,35 ~ 1.7, P = 0.41), and the eagles used on av- .

December 2002 Nest-site Sei.ection c:>f i he Crowned Hawk-Eagee 303

Table 1. Crowned Hawk-Eagle nest-tree characteristics of eucalyptus and indigenous tree groups in KwaZulu-Natal and Tai. Means ± one standard deviation and range in parenthesis. Values with the same superscripts indicate values that differed significantly from each other in the three-way comparison.

Indigenous Eucai.yptus Indigenous Kruskal- Species Ciass KwaZui.u-Natal RWAZuriJ-NAIAL Tai N Wallis H

DBH (cm) 93^' ± 29 126*> ± 32 234^'^ ± 66 35 21.6** (40-151) (83-206) (167-344) Tree height (m) 24ab + 5 44a + g 52'^ ± 14 35 25.7** (T5-34) (34-54) (33-67) Height of hrst 9“’ ± 6 12*’ ± 9 33^>'> ± 7 35 17.8** foliage (m) (1-19) (6-27) (26-42) Height of first side 9“ ± 6 15'’ ± 7 34’’ ± 9 35 17.8** branch (m) (1-20) (6-25) (25-47) Nest height (m) ]4ab + 3 22a<: + 7 ± 10 35 23.4** (7-21) (13-35) (2.5-49) Percent nest height 58 ± 14 52^' ± 13 71" ± 13 35 7.6* (43-93) (36-67) (44-90) 32b Percent first side 36^' ± 21 2: 12 66"’’ ± 13 35 branch height (4-62) (16-47) (44-78)

^ihc = p <; 0.05, I'ukey tests. * P < 0.05. P < 0.001.

erage 3 ± 1 branches (A ± SD, N = 35 trees) to were from trees where this fork type was not the nest on. Twenty-seven of 32 nests (84%) were most abundant (x^ = 6.3; P < 0.001). Overall, 22 placed within the foliage (as opposed to under the (63%) of the 35 nests were not placed in the most foliage), and placement of nests in relation to the abundant fork category and nest placement could foliage was not associated with tree groups (x^ not be associated with the most abundant fork cat- = = = 0.7, P 0.70). In Tai, 63% of the nests {N 8) egory of the different tree groups (x'^ 1.0; P were placed on the lowest side branch, more fre- 0.59). quently than nests in indigenous (13%, N — \1) The number of forks per nest tree did not differ and eucalyptus trees in KwaZulu-Natal (10%, N = among the tree groups (1 1 ± 6 forks in indigenous 10, = 9.3, P< 0.01). KwaZulu-Natal trees, 14 ± 8 in eucalyptus, and 7 Of the 35 nests sampled, 20 (57%) were placed ± 3 in Tai nest trees; Kruskal-Wallis ~ ^-4? P m a central fork, nine (26%) on a side branch, and = 0.16). Whereas the number of central forks per six (17%) against the main branch; nest placement tree did not differ among tree groups (1 ± 1, Krus- tree = — was not associated with groups (x^ 6.3; P kal-Wallis 772,35 = 3.2, P = 0.21), the number of 0.17). Whereas seven (78%) of the nine side- side forks did (indigenous KwaZulu-Natal 5 ± 4 branch nests and four (67%) of the six main- forks, eucalyptus 2 ± 2, and indigenous Tai 3 ± 3; branch nests were from the most abundant fork Kruskal-Wallis 772 35 = 6.2, P< 0.05), although the category, 18 (90%) of the 20 central-crotch nests classes were not significantly different from each other (Tukey tests, all P > 0.05). Eucalyptus had more forks against the main branch (11 ± 8) than Table 2. The emergence of Crowned Hawk-Eagle nest indigenous trees in KwaZulu-Natal (4 ± 3) and Tai trees above the surrounding forest. = (3 ± 1; Kruskal-Wallis 9.6, P< 0.01; Tukey tests, all P < 0.05) Emergent Nest Trees Yes No Totai. All the nest trees in Tai and 11 of 17 indigenous Indigenous—KwaZulu-Natal 11 6 17 nest trees in KwaZulu-Natal were emergents, Eucalyptus—KwaZulu-Natal 2 8 10 whereas only two of 10 eucalyptus protruded above Indigenous—Tai 8 0 8 the forest canopy (x^ = 12.2, P < 0.05; Table 2). Total (Percent) 21 14 35 (60) (40) Overall, nests were more accessible to flying eagles 304 Malan and Shultz VoL. 36, No. 4

Table 3. The number of Crowned Hawk-Eagle nest Table 4. The number of flight path.s per Crowned trees, with flight paths sampled in four cardinal direc- Hawk-Eagle nest tree, sampled in four directions, which tions, which allowed access to nest and random forks for allowed access to nest forks in emergent and non-emer- 17 indigenous and 10 eucalyptus trees in KwaZulu-Natal, gent trees. and eight indigenous trees in the Tai Forest. Number of Number of Flight Paths None One Two Three Four Total Flight Paths None One Two Three Four x^ Emergent 0 0 5 7 9 21 Nest fork 0 1 12 12 10 Non-emergent 0 1 5 3 5 14 2.4 Random fork 4 12 8 4 7 18.6**

** p< 0.001. Nest and random tree distances to topographical

features were not different for all variables when than were random forks (Table 3) . Access to nests comparing means (Table 6) and Crowned Hawk- could not be associated with their placement above Eagles were, therefore, non-selective regarding (as emergents) or within the forest canopy (Table these topographical features. One tree selected for

4) . In KwaZulu-Natal, seven of the eight non-emer- nesting was 20 m from an inhabited brick house gent eucalyptus were located on the edge of the and another 10 m from a used bitumen road. nest stand, whereas, all the non-emergent indige- Discussion nous trees were located inside the nest stands (x^ = 7.3, P< 0.01). Nest-site Selection. Tree-nesting raptors assess The mean distance from the nest tree to the variables such as vulnerability to predators, protec- nearest three trees did not differ among tree tion against adverse weather conditions, the cost of groups (indigenous KwaZulu-Natal 11 ± 6 m, eu- nest building, structural features of the nest tree, calyptus 12 ± 8 m, and indigenous Tai' 13 ± 5 m; and access to the nest when selecting a site to build

Kruskal-Wallis 7^2,34 ~ 1-0, P = 0.62). The density their nest (Newton 1979, Moore and Henny 1983, of trees at nest sites also did not differ among tree Bosakowski and Speiser 1994, Burton et al. 1994). groups (all trees 156 ± 175 trees/ha, indigenous Whilst smaller raptors regularly conceal their nests KwaZulu-Natal 172 ± 183 trees/ha, eucalyptus 189 to avoid predation, larger raptors are less secretive ±219 trees/ha, and indigenous Tai 85 ± 62 trees/ and customarily put their nests in exposed posi- ha; Kruskal-Wallis 7^2,34 ^ 1-0, P = 0.62). tions (Speiser and Bosakowski 1987, Selas 1996). The areas of 1 3 Crowned Hawk-Eagle nest stands The large, 2-2.5 m wide and 2.5-3 m deep nests in KwaZulu-Natal were not normally distributed of the Crowned Hawk-Eagle (Steyn 1982) are very and were predominantly less than 50 ha in size (Ta- conspicuous. ble 5). Nest stands were primarily small (20 m in Although large raptors generally do not hide width and 30-50 m in length) and elongated in their nests as they can defend their nestling against shape (shape-index <0.5; Table 5). Sbape-index predators (Moore and Henny 1983), Crowned values could not be associated with eucalyptus and Hawk-Eagles do suffer some nest predation from = indigenous tree stands (x^ = 0.12, P 0.73). primates, especially if the nest tree can be accessed

Table 5. Statistical distribution of KwaZulu-Natal Crowned Hawk-Eagle nest-stand variables and shape index with the Kolmogorov-Smirnov distribution test (K-S d) for normality.

Dominant Cafegory

(Percent) Mean ± 1 SD Range N K-S d

Surface area (ha) 0-50 (77) 35.4 ± 73.7 0.05-250.15 13 0.42* Maximum width (m) 20 (69) 253 ± 363 20-1090 13 0.34 Maximum length (m) 30-50 (69) 759 ± 987 30-3520 13 0.32 Shape (0. 0-1.0) 0.2-0.3 (23) 0.39 ± 0.22 0.04-0.80 13 0.16

* P < 0.0.5. December 2002 Nest-site Selection of the Crowned Hawk-Eagle 305

Table 6. Topographical characteristics measured from Crowned Hawk-Eagle nest and random trees in KwaZulu- Natal {N = 13 nests).

Variables Nest Tree Random Tree

Distance to water (m) 83 ± 147 (10-550)^^ 159 ± 199 (10-520) 0.86 Distance to house (m) 859 ± 1661 (20-6250) 906 ± 1738 (20-6550) 0.24 Distance to road (m) 282 ± 277 (10-810) 285 ± 341 (30-1010) 0.11

* Mann-Whitney fTtest.

^ Mean ± 1 SD (range).

from nearby trees (Tuer and Tuer 1974, Kalina and 3-4 times their body mass, such as bushbuck ( Tra-

Butynski 1994) . This may be a reason why Crowned gelaphus scriptus; Daneel 1979), which they dismem- Hawk-Eagles often select emergents for nest sites, ber and carry in parts to the nest. Brown (1966) especially in Tai where eight diurnal monkey spe- noted that, in the Karen Forest in Kenya, these ap- cies are found at very high densities (McGraw proach flights were always above the canopy, very 1998). In Tai, the tall nest trees with their wide laborious and broken into short 91-137 m stints so bases and high, first side branches (mean = 34 m as to rest between flights. Under these conditions, from the ground) may be extremely difficult, if not access to the nest would be critical in order to de- impossible, for monkeys to climb (T. Struhsaker liver nesting material and prey to the nest. Nesting pers. comm.). In KwaZulu-Natal, the presence of above the forest canopy in an emergent tree en- fewer primate species (three at the most; Smithers hances accessibility. 1983) may have resulted in reduced predation risk The large indigenous nest trees were simple in for nestlings and might have allowed for the use structure and provided, on average, one central of lower and non-emergent trees. fork, 3-4 forks against the main branch and 3-5 Sites may also be selected for nesting because forks on side branches for the eagles to place their the foliage protects the nest against adverse weath- nest. Notwithstanding, only 2-4 branches were er conditions (Moore and Henny 1983, Bosakowski used on which to build these large nests, indicating and Speiser 1994). Crowned Hawk-Eagle nests are that big, primary and secondary forks were select- usually situated within the leafy canopy, but the ed and not the smaller, multi-stemmed forks from birds also nest in exposed positions in partially col- within the canopy structure. Large raptors require lapsed or dead trees (Steyn 1982, Tarboton and a large tree-fork (crotch) to place the nest in and Allan 1984, Kalina and Butynski 1994). In this the more open branch structure may facilitate ac- study, 32 nests were located in or below the foliage cess (Newton 1979). The exotic eucalyptus differed and therefore sheltered, whereas the remaining from the indigenous nest trees in that they provid- three nests, two of which produced young during ed, on average, 1 1 more forks. This was largely due the study, were located in exposed positions in to the single main-stem growth form of these com- dead trees. Hence, although there was a trend for mercially-cultivated trees. Trees from these stands the birds to nest in a sheltered position, other fac- were also largely of similar height, probably be- tors, such as the availability of suitable nesting sites cause trees in these single species stands were and the cost of building a new nest, probably in- planted simultaneously. As seven of eight non- fluenced the continued occupation of a nest in a emergent, eucalyptus nest trees were located on dying or dead tree. the edge of the nest stand, the eagles may circum- Lastly, tree-nesting forest raptors may select trees vent the scarcity of emergent eucalyptus by select- for their size and structural features, such as a tall ing edge trees that have greater access to the nest. and open canopy, that allow unobstructed access In conclusion, because nests located within and to the nest (Speiser and Bosakowski 1987, Cerasoli above the canopy were equally accessible, access and Penteriani 1996). The Crowned Hawk-Eagle seemed to be the most critical feature identifying may require a nest that is easily accessible as it a Crowned Hawk-Eagle nesting tree and site. The needs to fly to the nest carrying sticks up to 1.2 m findings that indigenous nest trees in KwaZulu-Na- long and 8 cm thick (Steyn 1982). In addition. tal did not differ from eucalyptus or indigenous Crowned Hawk-Eagles are capable of killing prey trees from Tai Forest in terms of tree density and 306 Mai AN AND Shui.tz VoL. 36, No. 4

central and side fork availability, may indicate that able nest trees and nest-placement sites. Our rec- indigenous trees with their multiple main stems ommendations should therefore be treated with and open branch structure may be as accessible for some caution, as nests included in this study might flying eagles as emergent or edge trees. have been found unsuitable on the long term be- This study did not quantify the ‘openness’ and cause certain deficient nest features may have lim- accessibility of indigenous nest trees in KwaZulu- ited successful reproduction. Natal, particularly with regard to tree canopy di- Nonetheless, the nest trees must have open- ameter and volume, branch spacing and diameter, branch structures and large tree-forks. As nest trees and branch angle as nests were often placed on are typically emergents or edge trees, these trees near horizontal branches. Also, we did not exam- can be cultivated by felling surrounding trees or ine the inter-relationship between the largest-di- leaving the tall trees standing (Seydack 1995). In ameter side branches (required to support the this study more than half of the Crowned Hawk- large nests) and the position of the primary and Eagle nests were positioned in a central fork, there- secondary forks below or just inside the foliage, fore, the techniques of coppice-reduction or selec- related to openness and improved access. We also tive pruning could be employed to cultivate a tree did not take into account the slope at the nest site with the preferred 2-4 main branches. As Brown and aspect of the nest, as nests located on the (1966) demonstrated, suitable nest trees can be downhill side of the tree may have been more ac- identified a priori, and managers can therefore im- cessible to flying eagles. Given the floristic differ- plement these techniques to ensure a continued ences between forests in Tai and KwaZulu-Natal, a supply of suitable nest trees. comparison of nest sites Avith randomly selected To qualify as a nest tree, commercial eucalyptus sites, conducted at each nest stand, would have fur- should be managed to reach a minimum height of ther contributed toward the understanding of what 34 m and DBH of 83 cm (i.e., minimum size se- constitutes a suitable nest tree. Lastly, data on how lected for nesting) . Indigenous trees selected must easy arboreal primates can climb nest trees, partic- attain a minimum height of 15 m and diameter of ularly from the base, would have added to our un- 35 cm. The mean stand density of 156 trees/ha can derstanding of how successful Crowned Hawk-Ea- be employed as a guideline for Crowned Hawk-Ea- gles are in eliminating the predation risk by gle nesting habitat. Although exotic stands must be nesting in tall, emergent trees. managed to a minimum size so as not to encroach

Recommendations. Wildlife managers need to onto indigenous vegetation, nest-tree stand size it- manage forests by balancing timber harvesting self is nonessential. Furthermore, in plantations, with maintaining wildlife habitat and must employ nest stands cannot be placed at random as raptors multi-resource plans to do so (Lilieholm et al. often require nest trees to be located away from 1993, Vermeulen 1999, Malan and Robinson certain topographical features (Andrew and Mosh- 2001). These plans should incorporate both prac- er 1982, Malan and Robinson 1999). However, with tical and proactive management objectives to con- regard to the proximity of nests to human dwell- serve nesting habitat for large eagles in exotic and ings, water bodies, and public roads, the Crowned indigenous forests. Apart from silvicultural guide- Hawk-Eagles of KwaZulu-Natal were remarkably lines, other considerations must include the prox- non-selective and tolerant. In fact, the city of Dur- imity of nests to hunting habitat, their temporal ban, located in this province, harbors 12 active and spatial distribution, and tbe effects of human nests within its metropolitan boundaries. Inter- disturbance on nesting eagles (Lilieholm et al. stand distances were not recorded in this study, but 1993). Crowned Hawk-Eagles are known to nest 1.8—4.0 In this study, because we could not obtain reli- km apart and, thus, require only a relatively small able data on the age of the nests and how many patch of suitable hunting habitat (Tarboton and young were fledged from each nest over time, we Allan 1984, Allan et al. 1996, Mitani et al. 2001, did not compare the structural features of produc- Shultz 2002). Given the size of some of the prey tive between unproductive nests. Although other these eagles hunt, nest stands must preferentially factors also influence productivity, e.g., experience be located near the hunting habitat so as to sbort- of breeders, prey abundance, and persecution en flight distances to the nest. rates, the productivity analysis may have highlight- Because Crowned Hawk-Eagles use the same ed subtle differences between suitable and unsuit- nest for 10 years or longer, often until the tree col- December 2002 Nest-site Seitctton of the Crowned Hawk-Eagle 307 lapses (Brown 1966, Steyn 1982), suitable trees dation, Inc., Leslie Brown Memorial Award, the Pere- grine Foundation, a Wildlife Conservation Society Re- should not be felled. If the nest stand or tree must search Fellowship, and the Leakey Foundation. be harvested, the felling should be done outside the birds’ breeding season (August-March) and 6- Literature Cited 12 months after the nestlings have fledged to allow At j an, D. and W.R. Tarboton. 1985. Sparrowhawks and sufficient time for the young bird to become in- plantations. Pages 167-177 mL.J. Bunning [Ed.], Pro- (Steyn Tarboton and Allan 1984). dependent 1982, ceedings of the symposium on birds and man. Wits Given that a nest takes 4-5 mo to build (Brown Bird Club, Johannesburg, South Africa. nest trees, located in the vicin- 1966), replacement , D. Johnson, and T. Snyman. 1996. The crowned ity of the nest tree in use, should be cultivated long eagles of Durban and Pietermaritzburg. Afr. Birds Bird- in advance to provide a suitable alternative nest. ing 1:2-13.

The Crowned Hawk-Eagle in South Africa has , J.A. Harrison, R.A. Navarro, B.W. Van Wilgen, 1997. of been classified as near threatened because of past AND M.W. Thompson. The impact commercial afforestation on bird populations in Mpumalanga exploitation of nest trees and the likely destruction Province, South Africa—insights from bird atlas data. of nesting habitat in the near future (Boshoff et al. Biol. Conserv. 79:173-185. 1983, Barnes 2000). Occupied nests should be Andrew, J.M. and J.A. Mosher. 1982. Bald Eagle nest-site closely monitored to assess the status of this species selection and nesting habitat in Maryland. J. Wildl and to collect data on what constitutes productive Manage. 46:383-390. nests. Large tree-nesting forest raptors will always Anonymous. 1998. Commercial timber resources and have few suitable trees to nest in as large trees and roundwood processing in South Africa 1996/1997. forks are less abundant than smaller ones (Newton Dept, of Water Affairs and Forestry, Pretoria, South 1979). When nesting in large trees, eagles also Africa. compete directly with humans for this scarce re- Barnes, K.N. 2000. The eskom red data book of birds of South Africa, Lesotho, and Swaziland. BirdLife South source (Boshoff et al. 1983, Watson and Rabarisoa Africa, Johannesburg, South Africa. 2000). It is, therefore, no longer adequate simply Bijleveld, M. 1974. Birds of prey of Europe. Macmillan to protect forests for birds of conservation con- Press, London, UK. cern, but specific efforts must be made to satisfy Bosakowski, T. and R. Speiser. 1994. Macrohabitat selec- the nesting requirements of the Crowned Hawk- tion by nesting Northern Goshawks: implications for Eagle and other tree-nesting forest raptors; e.g., in managing eastern forests. Pages 46—49 in W.M. Block, South Africa the Bat Hawk {Macheiramphus alci- M.L. Morrison, and M.H. Reiser [Eds.], The North- nus), Ayres’s Hawk-Eagle (Hieraaetus ayresii), and ern Goshawk: ecology and management. Studies in Fasciated Snake-Eagle {Circaetus fasciolatus) avian biology No. 16. Cooper Ornithological Society, Sacramento, U.S.A. (Barnes 2000, Malan and Marais in press). Ulti- CA Boshoff, A.F. 1988. The spacing and breeding periodic- mately, a species-specific management plan should ity of Crowned Eagles in the southern Cape Province. be developed for these and other tree-nesting for- Bontebok 6:34—36. est birds and the maintenance of nest-tree struc- . 1997. Crowned Eagle Stephanoaetus coronatus. Pag- tural and topographical features incorporated into es 194—195 m J.A. Harrison, D.G. Allan, L.G. Under- management decisions. hill, M. Herremanns, A.J. Tree, V. Parker, and C.J. Brown [Eds.], The atlas of southern African birds Acknowledgments Vol. 1. BirdLife, Johannesburg, South Africa. We want to thank Natal Portland Cement and the , C.J. Vernon, and R.K. Brooke. 1983. Historical KwaZulu-Natal Ornithological Trust for sponsoring this atlas of the diurnal raptors of the Cape Province project. We also thank KwaZulu-Natal Wildlife for allow-

. Prov. Hist ing us to work in their reserves and park. Bill Howells (aves: falconiformes) Ann. Cape Mus. Nat. and David Johnson were particularly helpful in locating 14:173-297. nest sites. Guy Tedder, Denise James, Martin Buchler, Brown, L.H. 1966. Observations on some Kenya eagles. Gavin Lorry, and Bill Walker also informed us of nesting Ibis 108:531-572. localities. In Tai, we thank Professor Ronald Noe for host- and D. Amadon. 1989. Eagles, hawks, and falcons ing the Crowned Hawk-Eagle project, the Centre Suisse of the world. Wellfleet Press, New York, NY U.S.A. des Recherches Scientifiques, Centre de Recherche en Burton, A.M., R.A. t\lford, and J. Young. 1994. Repro- Ecologie, the Project Autonome pour la Conservation du ductive parameters of the Grey Goshawk {Accipiter no- Parc National de Tai for logistical support, the Minstere vaehollandiae) {Accipiterfasciatus) de la Recherche and the Direction de la Protection de la and Brown Goshawk Nature for permission to conduct the study. Funding (for at Abergowrie, northern Queensland, Australia J S. Shultz) was provided by the Raptor Research Foun- Zool. Land. 232:347—363. 308 Malan and Shuitz VoL. 36, No. 4

Cerasoli, M. and V. Penteriani, 1996. Nest-site and ae- Eagles {Stephanoaetus coronatus) in Bibale National rial point selection by Common Buzzards {Buteo buteo) Park, Uganda. Behav. Ecol. Sociobiol. 49:187-195. in Central Italy. / Raptor Res. 30:130-135. Moore, K.R. and CJ. Henny. 1983. Nest-site character- Daneel, A.B.C. 1979. Prey size and hunting methods of istics of three coexisting accipiter hawks in northeast- the Crowned Eagle. Ostrich 50:120—121. ern Oregon. Raptor Res. 17:65-76.

Newton, I. 1979. Population ecology of raptors. T. Daw, S.K., S. DeStefano, and R.J. Steidl. 1998. Does sur- & A.D vey method bias the description of Northern Goshawk Poyser, Berkhamsted, U.K. Phillips, E.A. 1959. Methods of vegetation study. Holt, nest-site structure? J. Wildl. Manage. 62:1379-1384. Rinehart & Winston, Inc., New York, NY U.S.A. Gartshore, M.E., P.D. Tayi or, and I.S. Erancis. 1995. Selas, V. 1996. Selection and reuse of nest stands by spar- Forest birds in the Cote d’Ivoire: a survey of Tai Na- rowhawks {Accipiter nisus) in relation to natural and tional Park and other forest and forestry plantations. manipulated variation in tree density, f. Avian Biol. 27. BirdLife Int. Stud. Rep. No. 58. BirdLife Internation- 56-62. al, Cambridge, U.K. Sfydacr, A.H.W. 1995. An unconventional approach to Guillaumet, J.L. 1994, La flore. Pages 66-71 m E.P. Rie- timber yield regulation for multi-aged, multispecies zebos, A.P. Vooren, and J.L. Guillaumet [Eds.], Le forests. Fundamental consideration. For. Ecol. Manage Parc National de Tai, Cote d’Ivoire. Synthese des con- 77:139-153. naissances. Fondation Tropenbos, Wageningen, Neth- Shuitz, S, 2002. Population den.sity, breeding chronolo- erlands. gy and diet of Crowned Eagles Stephanoaetus coronatus Kalina, J. and T.M. Butynski. 1994. Natural deaths of two in Tai National Park, Ivory Coast. Ibis 144:135-138. Crowned Eagles in Uganda. Gator 9:28-31. Smithers, R.H.N. 1983. The mammals of the southern

Lilieholm, R.J., W.B. Kessler, and K. Merrill. 1993. African sub-region. University of Pretoria, Pretoria, Stand density index applied in timber and goshawk South Africa. habitat objectives in Douglas-Fir. Environ. Manage. 17: Spelser, R. and T. Bosakowski. 1987. Nest-site selection 773-779. by Northern Goshawks in northern New jersey and Low, A.B. and A.G. Rebei.o. 1996. Vegetation of South southeastern New York. Cowiior 89:387-394. StatSoft. 1995. Statistica for Windows. StatSoft, Inc Africa, Lesotho, and Swaziland. Dept, of Environmen- , 2300 East 14th Street, Tulsa, U.S.A. tal Affairs and Tourism, Pretoria, South Africa. OK Steyn, 1977. Occupation and the use of the eucalyp- Macdonaid, I.A.W. 1986. Do redbreasted sparrowhawks D.J, tus plantations in Tzaneen area by indigenous birds belong in the Karoo? Bokmakierie 38:3-4. N A/l For /. 100:56-60. Malan, G. and E.R. Robinson. 1999. The diet of the Steyn, P. 1982. Birds of prey of southern Africa. David Black Sparrowhawk: hunting columbids in man-al- Philip Publishers, Cape Town, South Africa. tered environments. Durban Mus. Novit. 24:43-47. Tarboton, W.R. and D.G. Allan. 1984. The status and and E.R. Robinson. 2001. Nest-site selection by conservation of birds of prey in the Transvaal. Trans- Black Sparrowhawks Accipiter nielanoleucus: implica- vaal Mus. Monogr. No. 3. Transvaal Museum, Pretoria, tions for managing exotic pulpwood and sawlog for- South Africa. ests in South Africa. Environ. Manage. 28:195-205. Tler, V. and J. Tuer. 1974. (browned Eagles of the Ma- AND A.V.N. Marais. 2002. Guidelines for the de- topos. Honeyguide 80:32-41. sign and management of artificial raptor perches and Van der Zel, D.W. 1996. South African national forestry

exotic nest-tree sites on forestry estates. S. Afr. For. /.: action plan. Dept, of Water Affairs and Forestry, Pre- in press. toria, South Africa. McGraw, W.S. 1998. Comparative locomotion and habi- Vermeulen, C. 1999. The multiple-use management of tat use of six monkeys in the Tai Forest, Ivory Coast. the indigenous evergreen high forests of the southern Cape and Tsitsikamma. Dept, of Water Affairs Am. ]. Phys. Anthropol. 105:493-510. and E'orestry, Knysna, South Africa. Midgley, J.J., R.M. Cowling, A.H.W Seydack, and (i.E Watson, R.T. and R. Rabarisoa. 2000. Sakalava fisher- van Wyk. 1997. Forest. Pages 278-299 in R.M. C'.owl- man and Madagascar Fish-F.agles: enhancing tradi- ing, D.M. Richardson, and S.M. Pierce [Eds.], Vtygc- tional conservation rules to control resource abuse tation of southern Africa. Cambridge Univ. Press, that threatens a key breeding area for an endangered Cambridge, U.K. eagle. Ostrich 71:2-10. Mitani, J.C., WJ. Sanders, J.S. Lwanga, and T.K.L. Wind- eelder. 2001. Predatory behaviour of Crowned Hawk- Received 5 November 2001; accepted 2 August 2002 Short Communications

Juvenile Dispersal of Madagascar Fish-Eagles Tracked by Satellite Telemetry

Simon Rafanomezantsoa The Peregrine Fund, P.O. Box 4113, Antananarivo 101, Madagascar

Richard T. Watson ^ and Russell Thorstrom The Peregrine Fund, 5668 West Flying Hawk Lane, Boise, ID 83709 U.S.A.

Key Words: Madagascar Fish-Eagle, Haliaeetus vocifer- Methods oides; dispersal] satellite telemetry. This study occurred in coastal floodplain wetlands of western Madagascar between the Manambolo River The Madagascar Fish-Eagle {Haliaeetus vociferoides) is (19°15'S, 44°30'E) and Soahany River (18°40'S, 44°30’E), critically endangered (Stattersfield and Capper 2000) about 300 km west of the capital, Antananarivo. This area with a small population limited to wetland habitats on lies within the Western Malagasy phytogeographical region (Humbert which is characterized by annual Madagascar’s western seaboard (Rabarisoa et al. 1997). 1954), rainfall from 1000-2000 mm, monthly mean tempera- Observations of extra-pair adults at the nest and juveniles tures above 20°C, and elevations less than 800 m. The m the territories of breeding pairs (Watson et al. 1996, wet season begins in October or November and lasts 1999) suggest unusual behaviors that may occur as a re- through March. The dry season begins in May and lasts sult of overcrowding in limited suitable habitat, or if in- through September or October. The climax vegetation is the species’ ability to disperse into un- nate, may reduce tropical dry deciduous forest, but savanna grasslands, occupied habitat. In addition to the behavioral and maintained by burning, dominate the landscape (Gml- evolutionary significance of understanding these obser- laumet 1984). Most lakes in the region are floodplain vations, the cause and consequence of this behavior may lakes whose surface area varies considerably between wet affect conservation interventions intended to prevent the and dry seasons (Kiener and Richard-Vindard 1972). species’ extinction. We report the results of a pilot study During the 1997 breeding season (May-December), to measure the movements and habitat use of fledglings Platform Transmitter Terminals (PTTIOO Series®; Micro- wave Telemetry 2000, Inc., Columbia MD) with antennas after they left parental territories to better understand hxed at 45*^, were mounted with a backpack style harness post-fledging dispersal (Rafanomezantsoa 1998) and the on two fledgling fish-eagles. One transmitter (PTT No occurrence of extra birds at the nest, and to assess the 3482) was mounted on a female that was rescued from effect on dispersal of release of captive-raised birds (Wat- an aggressive sibling, raised in captivity, and released at son et al. 1996, 1999, Rafanomezantsoa and Kalavaha fledging age (Watson et al. 1996, 1999). This bird was 1999). released by hacking (a falconry term for the process of The movements of raptors have been investigated for release to the wild; Cade 2000) into unoccupied, suitable decades mainly by banding, direct observation in limited habitat at Lake Mangily (18°30'S, 44°34'E). The second areas, or tracking using VHF radios (Meyburg and Mey- PTT (No. 3480) was put on a male that fledged naturally burg 1999). Recently, satellite telemetry has provided a from a fish-eagle pair on Lake Ankerika (19°03'S, method that makes possible the global location of birds 44°27'E), about 65 km south of the first. PTTs were pro- over an extended period. Satellite telemetry was consid- grammed for 8 hr on, 24 hr off for six cycles; 8 hr on, for cycles; 8 on, hr off for the ered the method of choice to study juvenile dispersal in 96 hr off 84 and hr 240 remaining life of the transmitter, to gain more frequent Madagascar Fish-Eagles which may reach maturity at 3-4 locations of movements made in the first year, followed yr of age. In addition to the extended study period, ju- by less frequent locations for the remaining life of the veniles were expected to move distances greater than we PTT, which we expected to be at least 4 yr. could follow with conventional VHE-radio telemetry be- Satellite telemetry uses the ARGOS Data Collection cause much of their range is inaccessible, especially dur- and Location System (Meyburg et al. 1995). ARGOS as- flood ing Madagascar’s wet season when lowlands may signs PTT locations a grade according to calculated pre- (Rafanomezantsoa 1997). cision. We used only locations graded as within 1000 m of actual position. ARGOS reports two locations, one being a spurious mirror of the true location. We deduced

’ Corresponding author’s e-mail address: rwatson® the true location using either concurrent visual obser- peregrinefund.org vations, likelihood of sequential locations, or known hab-

309 310 Short Communications VoL. 36, No. 4

itat at each location. Locations were plotted in chrono- MCP range where human disturbance was high, such as logical order on a topographical 1:100 000 map. The pro- Lakes Bemamba and Antsohaly. gram Ranges IV® (Kenward 1990) was used to calculate The released female’s range during the wet season, as distances moved and range areas based on minimum water flooded the surrounding lowland areas, included convex polygons (MCP) around locations. Lakes Mangily and Sarny, other small lakes, and a portion Results of the Miharana River. Compared to the male, the female made only very short movements around the release site

PTT No. 3480 on the male operated for 282 d, from While it is possible that the low number of usable loca- 1 Decemher 1997-8 September 1998, providing 70 us- tions influenced her measured range area, results were able locations. From these locations, the total MCP range spread throughout a similar period to those of the male of the male was 1040 km^ (Fig. 1). Between the fledging and observations by our field team confirmed her loca- date on 13 October 1997 and 17 April 1998 (186 d), the tions during much of the study period. male moved in a relatively small area around its nest site. The differences in movement patterns of the male and During the wet season, from December-March, the male female are interesting. They may be related to sexual dif- visited small lakes and flooded lowlands to the south and ferences in behavior, but there are a number of other southeast of its nest site along the Manambolomaty River factors that could influence dispersal. For example, nat- and Lakes Kakobo and Antsohaly, covering an area of urally-raised and fledged compared with captive-raised 156.4 km^. By 24 April 1998, the male had moved north- and released by hacking might affect their behavior. So- northwest with one location near Lake Mangily (the fe- cial interactions with neighboring conspecifics, the nat- male’s release site) on the way. For 76 d at the beginning urally fledged male had at least 10 territorial pairs near- of the dry season, from 13 May 1998-28 July 1998, the by; whereas, the female had only one resident pair within male was located in the vicinity of the Soahanina River 5 km, which could have caused a difference in dispersal estuary, and associated ponds and mangroves, ranging behavior. Also, distribution of food during the wet-season over an area of 540.5 km^. The maximum distance re- floods might influence movements. corded from its nest was 51 km. By 5 August 1998 and Habitats visited by both eagles were lakes, rivers, man- through 8 September 1998, when the last usable trans- groves, and lowlands temporarily flooded during the wet mission was received, the male was located again in the season. We assume that movements of fledglings were vicinity of the nest where his parents were raising a nest- made in exploration of suitable foraging habitat because ling. there was no seasonal pattern to the movements, and The PTT on the female operated for 348 d, from 15 they were of short distance and duration relative to the October 1997-28 September 1998, providing 40 usable species’ capacity for flight. locations (Fig. 2). We received 21 usable locations from Despite the potential of satellite telemetry to track 15 October 1997-22 November 1997 when the PTT birds for up to 4 yr, because no signal was detected from ceased transmitting for unknown reasons. It then re-start- the PTTs after about 18 mo, we were unable to learn ed 80 d later on 11 February 1998 and we received an- more about the occurrence of extra birds at the nest be- other 19 usable locations through 28 September 1998. yond the observation that the male returned to its par- About 95% of usable fixes were <5 km from the release ent’s territory about 10 mo after fledging and remained site. Direct observation conhrmed that the bird moved there at least a month while the adults were caring for a around Lakes Mangily and Sarny until held observations nestling. Since this study, direct observation of banded ended 13 March 1998 due to inaccessibility from flood- birds, and molecular studies of their genetic relatedness, ing. The maximum distance recorded from the release have revealed far more information (Tingay 2000, Tingay site was 8.2 the distance 2.6 km and mean was km. The et al. 2002). range female’s MCP was 45 km^. Tracking additional birds to increase sample size needed to compare dispersal between naturally-fledged and Discussion captive-reared and released juveniles, and document hab-

Usable locations for the male were sufficient to deter- itat use during dispersal, has not been attempted. The mine several aspects of the bird’s movement. Locations practical difficulties and cost of captive rearing in Mad- were usually received 10 or more days apart, which lim- agascar, and the cost of satellite telemetry, precluded fur- ited the amount of detail that could be gained from ther study. Few studies have been done on post-fledging them, Initial movements of the naturally fledged male dispersal in raptors (e.g., Walls and Kenward 1994) or were distances of 5-18 km to sites that may be visible to comparison between captive-raised and naturally-fledged a soaring bird from its natal site. The male made one birds (e.g., Amar et al. 2000) probably for similar reasons. large movement of short duration 51 km to the north- As satellite telemetry becomes more efficient and afford- west, where he remained for 76 d, making successive able, these areas of study may benefit. short movements, until returning to his natal site. All ar- Satellite telemetry provided us with a level of coverage eas visited were without territorial, breeding pairs. The and continuity, especially for long-distance movements, male did not visit prominent wetland areas within his that we could not have achieved for the male using con- E

December 2002 Short Communications 311

44° 30’

Figure 1 . Chronological movements and minimum convex polygon range of the male Madagascar Fish-Eagle fledged from a nest on Lake Ankerika. 312 Short Communications VoL. 36, No. 4

Figure 2. Minimum convex polygon range of the captive-reared female Madagascar Fish-Eagle released by hacking at Lake Mangily. —

December 2002 Short Communications 313

ventional VHF radios and tracking from the ground. We Sugerimos que los movimientos de los volantones se hi- may have achieved similar results by VHF-radio tracking cieron para explorar habitats de forrajeo adecuados, ya from an aircraft, but lack of landing fields and fuel in que no hay un patron estacional para los movimientos, y the study area precluded this approach. The pro- fueron relativamente de corta distancia y duracion con grammed on-off cycle of the transmitters provided fewer respecto a la capacidad de vuelo de la e.specie. useful locations than we expected. A longer (e.g., 12-24 [Traduccion de Cesar Marquez] hr) on-cycle might have generated more usable locations m these birds that were more sedentary than migrating ACKNOWLTDCiMEN'rS raptors. For example, two migrating Bald Eagles {Hal- This study was conducted by The Peregrine Fund’s iaeetus leucocephalus) with PTTs programmed for 8 hr on, Madagascar Project with funding provided, in part, by 16 hr off, and 4 hr on, 44 hr off cycles generated 205 Environment Now, the Liz Claiborne and Art Ortenberg fixes in 136 d and 27 fixes in 119 d, respectively (Grubb Foundation, the John D, and Catherine T. MacArthur et al. 1994). A migrating Wahlberg’s Eagle {Aquila wahl- Foundation, the Walt Disney Company Foundation, the bergi) with a PTT programmed for 8 hr on, 134 hr off Little Family Foundation and other important contributors. The project received in-kind support from the Na- generated 104 locations in 234 d (Meyburg et al. 1995). tional Aeronautics and Space Administration, United A 12-24 hr on-cycle would increase the chance of satel- States Fish and Wildlife Service, and other partners. We lites passing over an eagle in optimum position (such as especially thank David H. Ellis, Jon W. Robinson, and m flight) to receive the transmitter’s signal. Transmission Paul Howey for their cooperation and support during of usable locations ceased for unknown reasons well be- this project, and the constructive reviews of this manu- fore their anticipated 4-yr lifespan. periods Unexplained script by James Berkelman, Mark Puller, and Robert Leh- of no data received added to our uncertainty of the birds’ man. movements.

We believe satellite telemetry is valuable for tracking Literature Cited the movement of large birds of prey; however, there are Amar, a., B.E. Arroyo, and V. Bretagnotle. 2000. Post- several limitations. The accuracy of locations within the fledgling dependence and dispersal in hacked and PTT’s operational period varied from day to day. The wild Montagu’s Warriers Circus pygargus. Ibis 142:21 precision of the location is known to be affected by sev- 28. eral satellite parameters and by the orientation, location, Cade, 2000. Progress in tran.slocation of diurnal rap- and movement of the transmitter. PTTs are at present T.J. tors. Pages 343—372 in R.D. Chancellor and B.-U. Mey- larger and less streamlined than conventional VHF trans- burg [Eds.], Raptors at risk. Hancock House/ mitters, and require antennas that protrude at a 45° an- WWGBP, Berlin, Germany. gle rather than contour down the back and the tail of Grubb T.G., Bowerman, P.H. the bird. Also, PTTs are .substantially more expensive, W.W. and Howey. 1994 local though this cost may compare favorably with the cost of Tracking and seasonal movements of wintering data collection from VHF radios which require personnel Bald Eagles Haliaeetus leucocephalus from Arizona and in the field and logistical support, Michigan with satellite telemetry. Pages 347—358 in B.-U. Meyburg and R.D. Chancellor [Eds.], Raptor conservation today. The Pica Press/WWGBP, Berlin, Resumen.—En 1997, colocamos radio transmisores a dos Germany. polluelos de aguilas pescadoras de Madagascar (Haliaee- Guiliaumet, J.-L. 1984. The vegetation: an extraordinary tus vociferoides) para estudiar sus movimientos y uso de 27-54 habitat durante la dispersion post emplumamiento. El diversity. Pages in A. Jolly, P. Oberle, and R macho partio naturalmente del nido de sus padres dur- Albignac [Eds.], Key environments: Madagascar. Per- gamon Press, Oxford, U.K. ante Octubre y nosotros liberamos la hembra criada en cautiverio el 15 de Octubre. El rango del aguila macho Humbert, H. 1954. Les territoires phytogeographiques de Madagascar, leur cartographic. Pages 195-204 in fue 1040 km^ entre el 1 de noviembre de 1997 y el 8 de Les divisions ecologiques du monde. Centre Nation- septiembre de 1998 (70 localizaciones) y se movio una distancia maxima de 51 km desde su area natal, al norte ale de la Recherche Scientifique, Paris, France. del rio Soahanina, El comenzo moviendose largas distan- Kenward, R.E. 1990. Ranges TV. Institute of Terrestrial cias (>5 km) el 16 de Diciembre de 1997, permanecio Ecology, Wareham, England. en la vecindad del estuario del rio Soahanina por 76 dias, Kiener, a. and G. Richard-Vindard. 1972. Fishes of the entonces retorn o a la vecindad del nido (<5 km) el 5 de continental waters of Madagascar. Pages 477-499 in Agosto de 1998. El rango de la Hembra fue 45 km^ entre R. Battistini and G. Richard-Vindard [Eds.], Bioge- el 15 de Octubre de 1997 y el 28 de Septiembre de 1998 ography and ecology of Madagascar, Dr. W. Junk B V (40 localizaciones) y se movio una distancia maxima de Publishers, The Hague, Netherlands. 8.2 km desde el sitio de liberacion. Los rios, lagos, mang- Meyburg, B.-U. and C. Meyburg. 1999. The study of rap- lares y zonas bajas temporalmente inundadas durante la tor migration in the old world using satellite teleme- temporada humeda fueron visitados por ambas aguilas. try. Pages 2992-3006 in N.J. Adams and R.H. Slotow 314 Short Communications VoL. 36, No. 4

[Eds.], Proc. 22nd Int, Ornithol. Congr. BirdLife 1997-1998. The Peregrine Fund, Antananarivo, Mad- South Africa, Johannesburg, South Africa. agascar. Meyburg, B.-U., J.M. Mendelsohn, D.H. Ellis, D.G. Statterseield, AJ. and D.R. Capper. 2000. Threatened Smith, C. Meyburg, and A.C. Kemp. 1995. Year-round birds of the world. Lynx Edicions, Barcelona, Spain. movements of a Wahlberg’s Eagle Aquila wahlbergi Tingay, R.E. 2000. Sex, lies, and dominance: paternity tracked by satellite. Ostrich 66:135-140, and behaviour of extra-pair Madagascar Fish-Eagles. M.S. thesis. University of Nottingham, U.K. Rabarisoa, R., R.T. Watson, R. Thorstrom, and J. Ber- kelman. 1997. The status of the Madagascar Fish-Ea- , M. CuLATR, E.M. Hallerman, R.T. Watson, and Fraser. gle Haliaeetus vociferoides in 1995. Ostrich 68:8-12. J.D. 2002. Subordinate males sire offspring in Madagascar Fish-Eagle {Haliaeetus vociferoides) polyan- Rafanomezantsoa, S.A. 1997. Behavior and natal dis- drous breeding groups. Raptor Res. 36:280-286. persal of fledgling Madagascar Fish-Eagles. Pages /. Wau.s, S.S. and R.E. Kenward. 1994. Movements of ra- 403-412 in R.T. Watson [Ed.], Madagascar wetlands dio-tagged Common Buzzards Buteo buteo in their first conservation project. Progress report III, The Pere- year. lUs 137:177-182. grine Fund, Boise, ID U.S.A. Watson, R.T, S. Thomsett, D. O’Daniel, and R. Lewis. . 1998. Contribution a 1’ etude des comportements 1996. Breeding, growth, development, and manage- et de la dispersion des jeunes pygargues de Madagas- ment of the Madagascar Fish-Eagle {Haliaeetus vocifer- car Haliaeetus vociferoides (Desmurs 1845) dans le com- oides). J. Raptor. Res. 30:21-27. plexe des 3 lacs d’Antsalova. Memoire de D.E.A. Univ- , S. Razaeindramanana, R. Thorstrom, and S. Ra- ersite d’Antananarivo, Madagascar. fanomezantsoa, 1999. Breeding biology, extra-pair and L. Kalavaha. 1999. Transfert de jeunes Py- birds, productivity, siblicide and conservation of the gargues de Madagascar. 115-123 in A. Andri- Pages Madagascar Fish-Eagle. Ostrich 70:105-111. anarimisa [Ed.]. Projet de conservation des zones humides de Madagascar. Rapport d’avancement V, Received 9 July 2001; accepted 28 June 2002 .

Prey of the Peregrine Falcon {Falco peregrinus cassini) in Southern Argentina and Chile

David H. Ellis^ USGS Patuxent Wildlife Research Center, HC 1 Box 4420, Oracle, AZ 85623 U.S.A.

Beth Ann Sabo Wildlife Forensics Services, P.O. Box 142613, Irving, TX 75014-2613 U.S.A.

James K. Fackler 590 Davidson Road, Bow, WA 98232 U.S.A.

Brian A. Millsap Fish and Wildlife Conservation Commission, 620 S. Meridian Street, Tallahassee, FL 32399 U.S.A.

Keywords; Peregrine Falcon; Falco peregrinus; Argentina; tached) but discarded those bones that were so bleached

Chile, Pallid Falcon; prey. that they may be attributed to former occupants of the eyrie. Most of the prey were identified from whole feathers. No pellets were used in this anaylsis. We included The Peregrine Falcon {Falco peregrinus cassini) in Pata- some feathers from the base of the eyrie cliffs, but ex- gonia attracted wide interest two decades ago (Anderson cluded those that were likely molted by other occupants and Ellis 1981, McNutt 1984) when there was a focus on of the cliff. For example, several of our eyries were in old determining the taxonomic position of the Pallid Falcon Black-faced (formerly buff-necked) Ibis {Tkeristicus cau- (also called Kleinschmidt’s falcon and Tierra del Fuego datus) nests within active ibis colonies. Although ibis falcon; formerly named Falco kreyenborgi) In 1981, how- feathers were frequently found near these eyries and ever, the pallid falcon was confirmed to be a pale color even though we occasionally observed peregrines pursu- ing ibis, we viewed these attacks near eyries as displace- morph of the peregrine (Ellis et al. 1981, Ellis and Peres ment activities. Only once did we include an ibis as prey 1983), and since that time, little work has been conduct- and this was after finding four fresh feathers within an ed on this color morph. Continent-wide research has eyrie which was neither beneath an ibis roost nor near continued and has yielded a fair understanding of the an ibis nest. McNutt (1981) observed peregrines killing breeding distribution of the Peregrine Falcon in South nestling ibis. (Anderson et al. et al. Rise- America 1988, McNutt 1988, No food habits study based on prey remains is without brough et al. 1990). Also, two preliminary food habits bias (Marti 1987, Bielefeldt et al. 1992). For peregrines, studies on the peregrine have been completed in Pata- bias derives from the fact that many prey individuals are gonia (McNutt 1981, Peres and Peres 1985). Together missed because prey are normally plucked before arrival those papers provided a list of 23 species observed as at the eyrie and many defleshed carcasses are removed by the adults elsewhere. several prey, and McNutt (1981) listed another eight species and deposited Also, cast- ings sometimes represent a single prey item. seen pursued (but not captured) by peregrines. Common prey are normally under represented in peregrine prey The purpose of this paper is to assemble all that has tallies, including our sample, because of the difficulty of been published on peregrine food habits for Patagonia totaling individuals. Our method was to derive a mini- and Tierra del Fuego and to add to that list from our mum count from feet, bills, remiges, and rectrices. For 1980 and 1981 expeditions. example, a sample of 300 feathers and assorted other remains from one species, and probably representing Methods dozens of individuals, may yield a much smaller mini- In November-December of 1980 and 1981, we traveled mum count. Conversely, rare prey are likely to be over by motor vehicle searching for eyries in Chubut, Santa estimated in most studies including this one, because a Cruz, and Rio Negro provinces of Argentina and in Ma- single feather, bill, or foot can document prey that was gallanes, Chile. Although we accessed 16 eyries, some accrued only once. were empty (prey remains sometimes scatter in the Prey were placed in plastic bags and air dried by open- wind), so our totals included prey from only 11 eyries. ing the bags in a windless situation on sunlit days and We accessed eyries (normally by rope) and recovered re- fumigated prior to identification at the U.S. National Mu- cent prey (feathers, feet, and bones with tendons at- seum (USNM: Smithsonian Institute). At USNM, we as- sembled a synoptic series including all known and most of the likely prey species. Because USNM does not have ^ E-mail address: [email protected] or dcellis® examples for all plumages of all Patagonian birds, we theriver.com could not determine species on nine individuals.

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Table 1. Avian prey of the Peregrine Falcon in southern Patagonia and Tierra del Fuego.^’^ Numbers refer to minimum number of items represented in remains. A plus ( + ) indicates that a taxa was documented, but the number of Items was not reported. Nomenclature follows Sibley and Monroe (1990).

Peres and McNutt Peres This Family Scientific Name Common Name 198L^ 19853 Study

Rheidae Rhea pennata Lesser Rhea + * 1* Tmamidae Eudromia elegans Elegant Crested-Tinamou 2

Podicipedidae Podiceps major Great Grebe 1 Procellariidae Halobaena caerulea Blue Petrel +

Pachyptila belcheri Slender-billed Prion -t-

Pelecanoididae Pelecanoides magellani Magellanic Diving-Petrel -f

Pelecanoides sp. 3

Ardeidae Nycticorax nycticorax Black-crowned Night-Heron 1

Threskiornithidae Theristicus caudatus Buff-necked Ibis *7*4 1 Anatidae Chloephaga picta Upland Goose

Anas sp. 1

Anas flavirostris Speckled Teal 2 1

Anas platalea Red Shoveler 1 Falconidae Falco sparverius American Kestrel 2 Phasianidae Callus gallus domesticus Domestic Chicken 1*

Rallidae Fulica leucoptera White-winged Coot 1

Charadriidae Vanellus chilensis Southern Lapwing 1 -t- 3 & 2*

Charadrius falklandicus Two-banded Plover -f

Charadrius modestus Rufous-chested Plover -h

Oreopholus ruficollis Tawny-throated Dotterel 1 -f 7 & 1*

Scolopacidae Fimosa haemastica Hudsonian Godwit -f

Gallinago stricklandii Fuegian Snipe 1

Thmocoridae Thinocorus orbignyianus Gray-breasted Seedsnipe 2 -f 4 Thinocorus rumicovorus Least Seedsnipe 17 + 5 Laridae Sterna sp. 2 Sterna hirundinacea South American Tern + Columbidae Zenaida auriculata Eared Dove 16

Metriopelia melanoptera Black-winged Ground-dove 1

Columba livia Rock Dove -f Psittacidae Cyanoliseus patagonus Burrowing Parakeet 2

Enicognathus ferrugineus Austral Parakeet 4 1

Caprimulgidae Caprimulgus longirostris Band-winged Nightjar 1 Furnariidae Geositta cunicularia Common Miner 3 Upucerthia dumetaria Scale-throated Earthcreeper 2 Eremobius phoenicurus Band-tailed Earthcreeper 2

Cinclodes fuscus Bar-winged Cinclodes 1 Cinclodes patagonicus Dark-bellied Cinclodes 4

Feptasthenura aegithaloides Plain-mantled Tit-Spinetail 1

Tyrannidae Neoxolmis rufiventris Chocolate-vented Tyrant 1 + 2

Muscisaxicola macloviana Dark-faced Ground-Tyrant 1

Fessonia rufa Patagonian Negrito 1 Hirundinidae TachyrAneta nieyeni Chilean Swallow 2 Notiochelidon cyanoleuca Blue-and-white Swallow 2 Troglodytidae Troglodytes musculus Tropical House-Wren +

Sturnidae Mimus patagonicus Patagonian Mockingbird 1 Muscicapidae Turdus falcklandii Austral Thrush 2 -1- 2 )

December 2002 Short Communications 317

Table 1. Continued.

Peres and McNutt Peres This Family Scientific Name Common Name 198U 19853 Study3

Montacillidae Anthus correndera Correndera Pipit 1

Fringillidae Agelaius thilius Yellow-winged Blackbird 1 Sturnella militaris Pampas Meadowlark +

Sturnella loyca Long-tailed Meadowlark 1

Molothrus bonariensis Shiny Cowbird 1

Phyrgilus gayi Grey-hooded Sierra-Finch 1

Phyrgilus fruticeti Mourning Sierra-Finch 3

Phrygilus unicolor Plumbeous Sierra-Finch 1

Melanodera melanodera Canary-winged Finch 1 Diuca diuca Common Diuca-Finch 3 Sicalis luteola Grassland Yellow-Finch 3

Carduelis barbata Black-chinned Siskin 1 Unknown 8 0 9

Total individuals 53+ unknown 102 Total identified individuals 45 unknown 93 Minimum no. species 13 17 42

^ Not listed is a Kelp Gull (Larus dominicanus) observed as prey of a juvenile Pallid Falcon on 10 March 1979 (Ellis and Glinski 1980) ^ Nonavian prey include only a lizard {Liolaemus sp.) and a small rodent.

^ An asterisk (*) in these columns identifies prey that had not achieved adult size.

It is not certain that all 7 ibis were nestlings when taken.

We identified feathers by placing materials from one Results eyrie in a shallow white box and from prior experience sorted the feathers into piles tentatively assigned to a like- From this and the previous two studies (McNutt 1981, ly taxon. A representative feather was grasped by forceps Peres and Peres 1985), we have documented a fair variety then compared to specimens of likely donor species. of the prey taken by the peregrine in Patagonia. McNutt Once a good match for size, color, and pattern was (1981) identified 13 prey species and two other genera. found, the pile of feathers was sorted to remove any that Peres and Peres (1985) noted 17 species, of which 10 did not represent this species and morph. Then the pro- were new (i.e., not previously noted by McNutt [1981]) cess was commenced anew. After one of us completed an The list from our study (Table 1) includes 42 species of identification for feathers without unique color patterns which 32 were not previously recorded. In summary, at (and most passerine primaries do not have bold color least prey species in 26 families are known to be taken patterns), a second person evaluated the feathers and 55 in Patagonia. this the confirmed or rejected the identification. The most diffi- by peregrines To can be added cult materials often required an evaluation extending an Kelp Gull {Larus dominicanus) recorded as prey of a ju- hour or more before a certain match was found. Occa- venile Pallid Falcon seen on 10 March 1979 (Ellis and sionally, a feather had to be washed and blow dried be- Glinski 1980). fore comparisons could be made. All identified materials were bagged separately and archived. Discussion In comparing feathers, it was often necessary to fan the wing or tail on the museum skin; to do so without Our list does not represent the full range of prey taken tearing the skin required holding the appendage in by the Peregrine Falcon in South America, because first alignment with the body while deflecting the tip of the of all, our study included only the southern fifth of the feather with forceps. To aid in this process, we prepared distribution of this race. Second, other prey species are flat skins with tail and one wing fanned for about 50 spe- known to be taken by this falcon in the Falkland Islands cies while in Argentina. For some other species, we mere- (Cawkell and Hamilton 1961) and in more northerly re- ly placed wings, tail, feet, beak, and feathers representing gions of South America (Hilgert 1988). Third, the low all body areas in a plastic bag. All specimens were deliv- numbers of individuals taken for common and likely prey ered to the Argentine Museum of Natural Sciences, Buenos Aires, Argentina, where the most valuable were species (e.g., only two Austral Thrushes [Turdus falcklan- retained. The remainder were released for export and dii\ and one Patagonian Mockingbird {Mimus patagoni- shipped to the U.S.A. cus) suggest that much more variety will come from con- 318 Short Communications VoT. 36, No. 4

tmued sampling. The relationship between diversity (i.e., sugiere que la diversidad de aves tomadas fue mucho mas the number of species detected) and sample size can be grande que la que se describe aqui. Esta alta diversidad, characterized as beginning with a 1:1 relationship but en parte, resulta de variedades palidas y de color normal with the plot soon leveling off and finally approaching que ocupan nichos de forrajeo un tanto diferentes. an upper asymptote (the true maximum in the number [Traduccion de Cesar Marquez] of species taken) only after several hundred prey are tal- Acknowledgments lied (Heck et al. 1975, Marti 1987). At present, the total for all three studies is less than 200 individuals. Further, In 1980, the U.S. Air Force funded much of our travel the two most commonly taken species in Table 1 were Our 1981 work was largely funded by the National Geo- represented by only ca. 23 and 16 individuals; before the graphic Society and an anonymous philanthropist. We thank Peter Simpson, manager of Estancia Chacabuco, upper asymptote is reached, we expect that the number Rio Negro, Argentina, for logistical support. Phil Angle of individuals of the most commonly-taken prey will ex- identified the lizard. Jamie Jimenez, Clayton White, and ceed 100. David Whitacre reviewed and improved the manuscript The list of species taken (Table suggests that the 1) Our thanks to staff at the USNM for allowing space for peregrine is prone to capture some prey on the ground. our synoptic series and patience during the extended The gosling was observed being taken on a gravel bar. time devoted to identifying prey. Surely, the young rheas, perhaps the tinamou, and likely Literature Cited some of the other young birds in Table 1 were taken on the ground. In addition to the avian prey tallied, we also Anderson, C.M. and D.H. Ellis. 1981. Falco kreyenborgi— recorded one lizard {Liolaemus sp.) and a small mammal a current review. Raptor Res. 15:33-41. (Rodentia ca. 40 both of these would likely have been g); , T.L. Maechtle, and W.G. Vasina. 1988. The taken on the ground (or kleptoparasitized) . In South southern breeding limit of the Peregrine Falcon. Pag- America there is no competing large falcon that hunts es 251-253 mT.J. Cade,J.H. Enderson, C.G. Thelan- terrestrial prey (i.e., like the Prairie Falcon [A mexicanus] der, and C.M. White [Eds.], Peregrine Falcon popu- m North America and the Saker Falcon [A cherrug] in lations: their management and recovery. The Europe and Asia) that may constrain the Peregrine Fal- Peregrine Fund, Boise, ID U.S.A. con to an aerial foraging niche, so it was to be expected Bielefeldt, J., R.N. Rosenfield, andJ.M. Papp. 1992. Un- that the peregrine in Patagonia would take quarry on the founded assumptions about diet of the Cooper’s ground more frequently than do some other races. Hawk. Condor 94:427-436. It is obvious from the variety of oceanic species on the Cawkell, E.M. and J.E. Hamilton. 1961. The birds of Peres list (Peres and Peres 1985; Table 1) that their study the Falkland Islands. Ibis 103:1-27. emphasized coastal areas. Their sample was also from an Ellis, D.H. and R.L. Glinskj. 1980. Some unusual re- area where the pallid morph is relatively common (C. cords for the Peregrine and Pallid Falcons in South Peres pers. comm.). Their results, in comparison with America. Condor 82:350-351. our list for inland eyries, where the pallid morph is rare, and C. Peres. 1983. The Pallid Falcon Falco krey- suggest that pallid dark different and peregrines hunt enborgi is a color phase of the Austral Peregrine Falcon prey. To document this potential difference (i.e., to com- {Falco peregrinus cassini). Auk 100:269-271. pare the foraging niches of two sympatric color morphs) , C.M. Anderson, and T.B. Roundy. 1981. Falco will surely be an interesting ecological study. Pallid and kreyenborgi: more pieces for the puzzle. Raptor Res. 15. normal birds appear very different in the field. Pallid 42-45. birds are less conspicuous and gull-like when seen be- Heck, K.L., Jr., G. van Belle, and D. Simberloff. 1975 neath gray, overcast skies. We propose that the pallid Explicit calculation of the rarefaction diversity mea- morph may have evolved when conditions were right for surement and the determination of sufficient sample a population of pale peregrines to live in isolation from size. Ecology 56:1459-1461. the population of normal peregrines further north on Hii.gert, N. 1988. Aspects of breeding and feeding be- mainland South America. havior of Peregrine Falcons in Guayllabamba, Ecua-

dor. Pages 749-755 in T.J. Cade, J.H. Enderson, C.G Resumen.—^A partir de publicaciones previas, conocemos Thelander, and C.M. White [Eds.], Peregrine Falcon menos de 100 item presa que representan poco menos populations; their management and recovery. The de 25 especies de aves para el halcon peregrine de la Peregrine Fund, Boise, ID U.S.A. Patagonia {Falco peregrinus cassini). Este estudio, incluye Marti, C.D. 1987. Raptor food habits studies. Pages 67- presas de 11 nidos, anade 93 presas identificadas repre- 80 in B.A.Giron Pendleton, B.A. Millsap, K.W. Cline, sentando 42 especies de aves (32 no reportadas previa- and D.M. Bird [Eds.], Raptor management tech- mente), un lagarto, y un mamifero pequeno. Aunque do- niques manual. Natl. Wildl. Fed. Sci. Tech. Ser. No cumentamos una considerable variedad de presas para el 10 . halcon peregrine en esta region, la frecuencia con la cual McNutt, J.W. 1981. Seleccion de presa y comportamien- nuevas presas fueron encontradas en cada nido visitado, to de caza del Halcon Peregrino {Falco peregrinus) en December 2002 Short Communications 319

Magallanes y Tierra del Fuego. An. Inst. Patagonia 12: Risebrough, R.W., A.M. Springer, S.A. Temple, C.M. 221-228. White, J.L.B. Albuquerque, P.H. Bloom, R.W. Fyfe,

. 1984. A Peregrine Falcon polymorph: observa- M.N. Kirven, B.A. Luscombe, D.G. Roseneau, M. tions of the reproductive behavior of Falco kreyenborgi. Sander, N.J. Schmitt, C.G. Thelander, W.G. Vasina, Condor 86:378—382. AND W. Walker, II. 1990. Observaciones del halcon

, D.H. Ellis, C. Peres, T.B. Roundy, W.G. Vasina, peregrino, Falco peregrinus subspecies, en America del AND C.M. White. 1988. Distribution and status of the Sur. Rev. Bras. Biol. 50:563-574. Peregrine Falcon in South America. Pages 237-249 in Sibley, C.G. and B.L. Monroe, Jr. 1990. Distribution and T.J. Cade, J.H. Enderson, C.G. Thelander, and C.M. of birds of the world. Yale Univ. Press, White [Eds.], Peregrine Ealcon populations: their taxonomy New management and recovery. Peregrine Fund, Boise, Haven, CT U.S.A. ID U.S.A. Peres, M. and C. Peres. 1985. Peregrine project, Argen- tina (activities 1982). Bull. WWGBP 2:109-110. Received 7 January 2001; accepted 10 July 2002 ,

An Elevated Net Assembly to Capture Nesting Raptors

Eugene A. Jacobs^ Linwood Springs Research Station, 1601 Brown Deer Lane, Stevens Point, WI 54481 U.S.A.

Glenn A. Proudfoot^ Caesar Kleberg Wildlife Research Institute, Mail Stop 218, Texas A&M University-Kingsville, Kingsville, TX 78363-8202 U.S.A.

Key Words: capture techniques-, dho-gaza; drop net, elevated tubing 3 cm diameter at the center of the cross bar to a goal net, mechanical owl", mist net. form “T” that resembled the posts of most Amer- ican football fields. The “T” formation provided a stable base for the net assembly and the diameter of the base The use of a Great Horned Owl {Bubo virginianus) to of the “T” allowed for quick insertion of the cross bar induce mobbing behavior, in combination with a net sys- to a telescoping pole. Two 2.2-m sections of conduit tub- the technique choice for capturing tem, has become of ing 1,8 cm in diameter were inserted into the upturned many species of nesting raptors (Hamerstrom 1963, ends of the cross bar to form the uprights that supported Bloom 1987, Bloom et al. 1992, Steenhof et al. 1994, Ja- the net. We used four tethered leads about 12 cm in cobs 1996, McCloskey and Dewey 1999). However, some length, four metal rings (shower curtain rings) about 5 species, and some individuals trapped previously, may be cm in diameter, and either wooden clothespins or mag- reluctant to stoop at the owl when conventional tech- nets to attach the four corners of the net to the tops and bottoms of uprights. When clothespins were used, the niques (i.e., placing owl and nets near ground level) are free ends of the tethered leads were held by clothespins followed (Rosenfield and Bielefeldt 1993). In testing a taped to the top two ends of the uprights. When magnets mounted and live Great Horned Owl to induce mobbing were used, a metal washer tied to the free end of the behavior in American Kestrels {Falco sparverius) Card et tethered leads provided support for the top two corners al. that the closer owl decoy was placed (1989) found an of the net. The bottom two leads were attached to the to the nest the more aggressive the kestrels became. A bottom of the uprights and remained stationary. Two decoy (mounted or live) placed near the nest of “trap metal rings were placed on each side of the net, one in shy” Cooper’s Hawks {Accipiter cooperii) was more effective the top corner and one at the half-way point. The rings than conventional techniques, but this method required attached the net to the uprights allowing the net to re- climbing tree(s) and was found to be time consuming main open during set-up, The rings also allow the net to freely to the cross a bird contact (Rosenfield and Bielefeldt 1993). Here we describe an drop bar when made Once contact is made with the net, the net slides down elevated net assembly that, in combination with an owl the uprights and creates a pocket entrapping the bird. decoy, proved successful for trapping five species of rap- We inserted a 10-cm section of tubing (vertical, 1.1 cm tors. in diameter) into the bottom of the owl’s perch and attached a corresponding 30-cm section of tubing (0.9 cm MATERIAI.S AND METHODS diameter) to the “T.” This was positioned so that about The system consisted of an aluminum telescoping pole, 15 cm of the tubing extended above the center of the a horizontal cross bar, two vertical upright poles, a dho- cross bar to support the owl’s perch. gaza type net (Clark 1981), and a mechanical owl The 2-8 m telescoping pole allowed us to adjust the (equipped with two radio controlled servos that provided height of the net assembly to suit the nest site. Three guy movement to the owl’s head and perch) as described by lines attached to the base of the “T” bracket stabilized Jacobs (1996; Fig. 1). The cross bar that supported the the net assembly when the telescoping pole was extended net assembly was a 3-m section of conduit tubing 2.5 cm to a height greater than 3 m. We used a 1-m section of in diameter. used a commercially available conduit- We 1 .3 cm diameter conduit tubing, hammered flat at one 90° bending tool to form angles 25 cm from each end of end and cut to form a point, as support stakes for the the tubing, resulting in a “U ’’-shaped cross bar. A section telescoping pole and 0.5 m stakes (fashioned the same X of sheet metal (45 cm 45 cm) was then bent around way) for the guy lines. Total cost of materials was ca. $250 the cross bar to form a triangular bracket that enveloped (U.S.); telescoping pole ($180), net (.$20), cross bar the cross bar. Using sheet metal screws, this sheet metal ($10), uprights ($10), anchor stake for telescoping pole envelope was attached to a 25-cm section of aluminum ($10), guy lines and support stakes (.$10), and miscella- neous material ($10). Because vegetation structure varied among nest sites, ‘ E-mail address: [email protected] we elevated the net assembly to the maximum length of 2 Present address: Department of Wildlife and Fisheries the support pole (8 m) or to the highest feasible level Sciences, Room 210, Nagle Hall, Texas A&M University, where tree branches blocked a greater extension. The College Station, TX 77843-2258 U.S.A. net assembly was placed within 50 m of the nest tree, in

320 ,

December 2002 Short Communications 321

Figure 1. Elevated dho-gaza net assembly used to trap small- and medium-sized raptors near their nests.

view of the nest and with a clear flight path around the net assembly (cross bar and uprights) to 2 m X 1 m, net. Great Horned Owl vocalizations and conspecific calls replacing the dho-gaza with a shortened 2-shelf mist net, were utilized to lure nesting raptors to the net system and replacing the mechanical owl with a conspecific (Bloom et al. 1992). A concealed observer was positioned mounted decoy. This modified setup was used as de- nearby (<100 m) to operate the radio controls to the scribed above (using lure to induce mobbing behavior mechanical owl and record the sex of the adults when from nesting owls), or simply placed in front of the nest they were detected in the nest area (<50 m of nest). The cavity entrance to capture the adults as they entered the observer (s) was able to sex all American Kestrels and cavity to feed nestlings. The elevated mist net was placed Sharp-shinned Hawks (A. striatus) from plumage char- about 1.5 m from the nest cavity’s entrance. acteristics or relative size compared to their mates (Clark and Wheeler 1987). We reported trapping success by us- Results and Discussion ing the number of birds trapped, divided by the number During the breeding seasons this of birds “tested” (birds detected within 50 m of the nest) (1994-2001) tech- multiplied by 100. nique was “tested” on five species of small to medium When trapping Ferruginous Pygmy-Owls {Glaucidium sized raptors. Overall, we successfully captured 73% (113 brasilianum) we modified this system by downsizing the of 154) of the individuals “tested.” Our trapping success .

322 Short Communications VoL. 36, No. 4

Table 1. Comparison of capture rates of elevated net with a mechanical owl, normal net with a mechanical owl, and normal net with a live owl as a trapping technique for raptors.

Elevated Net with Ground-level with Mechanical Owl Mechanical Owl Ground-level (This Study) (Jacobs 1996) with Live Owl

Red-shouldered Hawk 65% (30 of 46) 54% (15 of 28) 75% (199 of 264)1 Sharp-shinned Hawk 81% (34 of 42) 77% (48 of 62) — American Kestrel 70% (21 of 30) — 71% (15 of 21)2 97% (115 of 118)1 Cooper’s Hawk 67% (2 of 3) 60% (3 of 5) 52% (32 of 62)1 Ferruginous Pygmy-Owl 79% (26 of 33) — —

' Data from Bloom et al. 1992.

^ Data from Steenhof et al. 1994.

was generally similar or slightly lower than studies using ple locations with a minimal amount of setup time (ca. a ground-level net set (height ^2.5 m) and live owl 15 min).

(Bloom et al. 1992, Steenhof et al. 1994) and slightly Even though we conducted 113 captures without any better than Jacobs (1996) found when using a normal visible injury, there is the potential for serious injury to net set and a mechanical owl (Table 1 ) species that “stoop” at higher speeds and are of greater

Bloom (1987) occasionally found it was difficult or mass than the Red-shouldered Hawk. A net that com- time consuming to capture both sexes of Northern Gos- pletely releases from the uprights (Bloom 1987) as well hawks (A. gentilis). Females were usually caught within 15 as other modifications may be necessary to accommodate min, but males were often not captured. He speculated the force of a larger raptor hitting the net. Alternatively,

that the male is less aggressive toward the owl during the because the “cut-down” mist net was successful in cap-

post-fledging period or is away from the nest (hunting) turing Ferruginous Pygmy-Owls as they approached or

and is unaware of the owl’s presence. With Sharp- exited the entrance to their nest cavity, this technique shinned Hawks and American Kestrels, we found of the should be effective for trapping most small cavity-nesting birds that were present (assumed to have seen the owl), birds without modification. females responded more aggressively toward the owl mount than did males. Trapping success for female Resumen.—Debido a su alta tasa de exito, el uso de una Sharp-shinned Hawks and female American Kestrels were red de niebla en combinacion con un senuelo de Bubo 91% (21 of 23) and 79% (11 of 14), respectively. Males virginianus, es una de las tecnicas populaces mas usadas of both species occasionally showed a reluctance to para capturar rapaces durante su anidacion. Sin embar- “stoop” at the owl, resulting in a trapping success of 68% go, el protocolo estandar para esta tecnica limita su efec-

(13 of 19) for male Sharp-shinned Hawks and 63% (10 tividad a aves que tiene la habilidad de volar cerca al nivel of 16) for male American Kestrels. The escape rate (per- del suelo (<3 m) para atropellar al senuelo. Con el fin centage of birds that hit the dho-gaza net, but were not de proveer una tecnica alternativa que pueda mejorar la captured) was 1.8% (2 of 113). tasa de captura en algunas situaciones, construimos y Benefits of this technique include: (1) a high response probamos un ensamblaje de redes elevado consistente de rate; (2) a low escape rate; (3) the ability to readily adjust un poste telescopico de aluminio, una barra cruzada hor- net height; (4) minimal space (especially when com- izontal, dos postes verticales rectos, una red de niebla, y pared to a 12-m mist net) is required for setup; (5) this un buho raecanico. Desde 1994-2001, el exito en la cap- technique kept the net off the ground, and hence, re- tura de cinco especies de rapaces de talla pequena a me- quired less preparation time to reset the net after a cap- diana fue 73% (113/154 intentos). Debido a su adapta- ture when compared to a ground-level dho-gaza net. bilidad, el alto exito de captura y el bajo costo, este Albanese and Piaskowski (1999) and Stokes et al. sistema puede ser una herramienta beneficiosa para la (2000) have described similar techniques that use elevat- investigadon de las aves. ed mist nets to study birds that spend the majority of [Traduccion de Cesar Marquez] their time in woodland canopies. However, those studies used conventional mist nets in a manner designed for Acknowledgments continuous use at one location. Our technique was de- We thank D. Haessly and R. Rosenfield for providing signed to capture specific birds near their nest sites with information on the effectiveness of our system on Amer- a mobile apparatus that allows researchers to visit multi- ican Kestrels and Cooper’s Hawks, respectively. J. Runke December 2002 Short Communications 323

provided the drawing in Figure 1. J. Bielefeldt, P. Bloom, Card, N.W., D.M. Bird, R. Densmore, and M. Hamel J Marks, M. McMillian, and B. Woodbridge provided 1989. Responses of breeding American Kestrels to live helpful suggestions for improving this manuscript. and mounted Great Horned Owls. J. Raptor Res. 23 99-102. Literature Cited Hamerstrom, F. 1963. The use of Great Horned Owls in Albanese, G. and V.D. Piaskowski. 1999. An inexpensive catching marsh hawks. Proc. XIII Int. Ornithol. Congr elevated mist net apparatus. N. Am. Bird Bander 24: 13:866-869. 129-134. Jacobs, E.A. 1996. A mechanical owl as a trapping lure Bloom, P.H. 1987. Capturing and handling raptors. Pag- for raptors. / Raptor Res. 30:31-32. Millsap, es 99-123 in B.A. K.W. Cline, B.G. Pendleton, McCloskey, J.T. and S.R. Dewey. 1999. Improving the and D.A. Bird [Eds.] Raptor techniques , management success of a mounted Great Horned Owl lure for trap- manual. Natl. Wildl. Fed., Washington, DC U.S.A ping Northern Goshawks./. Raptor Res. 33:168-169

, J.L. Henckel, E.H. Henckel, J.K. Schmutz, B. Roseneield, R.N. and j. Bielefeldt. 1993. Trapping tech- Woodbridge, J.R. Bryan, R.L. Anderson, P.J. De- niques for breeding Cooper’s Hawks; two modifica-

TRicH, T.L. Maechtke, J.O. McKinley, M.D. McCrary, tions. /. Raptor Res. 27:171-172. K. Titus, and P.F. Schempf. 1992. The dho-gaza with Steenhof, K., G.P. Carpenter, and J.C. Bednarz. 1994 Great Horned Owl lure: an analysis of its effectiveness Use of mist nets and a live Great Horned Owl to cap- in capturing raptors./. Raptor Res. 26:167—178. ture breeding American Kestrels. J. Raptor Res. 28. Clark, W.S. 1981. A modified dho-gaza trap for use at a 194-196.

raptor banding station. J. Wildl. Manage. 45:1043- Stokes, A.E., B.B. Schultz, R.M. Degraaf, and C.R 1044. Griffin. 2000. Setting mist nets from platforms in the and B.K. Wheeler. 1987. A field guide to hawks forest./. Field Ornithol. 71:57-65. in North America. Houghton Mifflin Co., Boston, MA U.S.A. Received 31 December 2001; accepted 13 July 2002 ,

Florida Bald Eagle (Haliaeetus leucocephalus) Egg Characteristics

M. Alan Jenkins, 1 Steve K. Sherrod, David A. Wiedenfeld, and Donald H. Wolfe, Jr. George Miksch Sutton Avian Research Center, RO. Box 2007, Bartlesville, OK 74005 U.S.A.

Key Words: Bald Eagle, Haliaeetus leucocephalus; eggs\ piece was equipped with a micrometer calibrated with a eggshell characteristics', pesticides. stage micrometer. Each shell sample was viewed with the microscope on its edge, the number of calibrations span- ning the fragment recorded, and the thickness calculated The Bald Eagle {Haliaeetus leucocephalus) south of the using a constant conversion factor obtained from the cal- 40th parallel, was declared endangered by the U.S. Fish ibration (Enderson et al. 1982). The three thickness mea- Wildlife Service in 1967 owing to an observed pop- and surements of each egg were averaged. ulation decline in the 48 contiguous states, which was Shell membranes of hatched eggs usually shrank, be- hrst noticed in Florida. A population of eagles in western coming detached from the shell and so they could not peninsular Florida showed a sharp decline by 1957-58 be measured as part of the shell’s thickness. Shell mem- (Broley 1958), and in eastern-central Florida the species branes from unhatched eggs sometimes remained at- declined by two-thirds between 1951-61 (Howell 1963). tached after drying and, where possible, shells were measured with attached then the membranes Those declines were later attributed to poisoning or the membranes, removed and shell thickness re-measured. This gave shell weakening effects on eggshells caused by chlorinated hy- thicknesses with and without membranes for 37 eggs. drocarbon pesticide residues, notably DDE (Nisbet This allowed us to correct for loss of shell thickness 1989). Eggs with shells thinned by DDE broke before caused when shell membranes become detached. De- hatching, destroying the egg and resulting in lowered tachment of the shell membranes after drying slightly productivity. From 1984—91 biologists with the George reduces the measured total shell thickness because the Miksch Sutton Avian Research Center collected entire mammillary tips from the shell come away attached to clutches of Bald Eagle eggs from Florida nests as part of the outer shell membrane during detachment (Terepka a project to restore nesting populations of this species to 1963). Calculated egg volumes presented here include the the southeastern U.S. (Sherrod et al. 1989). The eggs shell volume, a method preferable to trying to determine were incubated and hatchlings were reared in Oklahoma, inside volume (Stickel et al. 1973). The calculated vol- and the young were released by hacking in eight south- ume formula was determined to be within —8 to +7 per- eastern states. This paper describes the physical charac- cent of measured volumes for this species (Stickel et al teristics of 395 Bald Eagle eggs and the analysis of pesti- 1973). Shell thicknesses may decrease during embryo de- cide residues in 15 unhatched eggs collected during that velopment as the embryo uses calcium from the shell for project. We report the results of testing for correlations bone formation (Romanoff and Romanoff 1949). How- between egg characteristics, location of collection, year, ever, most of the decrease apparently occurs in the mam- sex of the eagle hatched, and information on organo- millae core (Bond et al. 1988) and does not contribute significantly to shell thinning et al. Cal- chlorine pesticides and eggshell thickness. (Bunck 1985). culated egg volume (V) was estimated using the formula Study Area and Methods V = 0.508LB^ (Stickel et al. 1973), where L = length of

egg (cm) and B = breadth of egg (cm) . Calculated fresh Eggs were collected from nine counties in north-cen- egg mass (M) was estimated as M = 0.56227LB^. The tral Florida (Fig. 1). At collection, each egg was marked coefficient of 0.56227 yielded the best estimate of hatch- with a unique number, measured for length and breadth ing date, assuming a period from the beginning of in- with a caliper to the nearest 0.01 mm, and weighed to cubation to pip of 33.5 d. the nearest 0.1 g (balance) or 0.01 g (electronic scale). Unhatched eggs were considered fertile if they showed After incubation, the shells of hatched eggs were air- any sign of embryonic development upon dissection dned and their thickness measured. Unhatched eggs Hatch order within clutches was recorded based on pip- were frozen for as long as a year, a method of preserva- ping date and time. Hatch order was assumed to be iden- tion which does not change the level of pesticide con- tical with laying order because female eagles lay eggs a centrations even if thawing and microbial degradation few days apart and begin incubation with the first eggs, occur (Stickel et al. 1984). Unhatched eggs were opened, making hatching within a clutch asynchronous (Gerrard the contents removed, the shells were air-dried, and the Bortolotti 1988). However, time of pipping was only shell thickness measured. and Thickness measurements were made on fragments of accurate within ca. 12 hr because eggs were checked twice daily for pipping. shell from three evenly spaced places near the equator. fledgling-age Fragments were clamped in a hemostat and viewed with Sex of eagles was determined from mea- bill following the a binocular microscope at lOOX. One microscope eye- surements of depth and toepad length methods of Walborn (1991). Egg length, breadth, volume, length/breadth ratio, cal-

1 E-mail address: [email protected] culated fresh mass, and shell thickness were checked for

324 December 2002 Short Communications 325

Key to Counties A = Alachua O = Osceola H = Highlands Po = Polk La = Lake Pu = Putnam

Le = Levy S - Seminole M = Marion V = Volusia

Figure 1. Florida Bald Eagle study area and counties of egg collections.

correlations with year and the latitude of the Florida ed fresh mass, and shell thickness and the year of collec- county where collected to determine any latitude trend. tion or the latitude of the Florida county where collected Analysis of variance was used to compare shell thickness, (Table 1). There was a significant increase of eggshell volume, and hatch order by sex; volume and shell thick- thickness from 1984-91 (T - 0.073, df = 392, P < 0.05) ness (for all and for both sexes) by hatch order; and However, the increase was not signihcant if data for 1984 volume and shell thickness with fertility. Statistical tests were made using Systat statistical package, version 7.0. were excluded. The 1984 sample size {N = 18) is biased Organochlorine and polychlorinated biphenyl pesti- by the inclusion of an unusually thin-shelled two-egg cide residues of the contents of 15 unhatched eggs were clutch with very high pesticide residues. One of these two analyzed by Hazleton Labs using Food and Drug Admin- eggs was found broken in the nest; the other failed to istration (1973) methods. The reported residues are develop. The eggshells we collected were 4.5% thinner based on calculated fresh egg masses. than the pre-1947 Florida sample {N = 211) measured Results by Anderson and Hickey (1972). No significant correlations were found between egg Residue analysis results for 23 chlorinated hydrocar- length, breadth, volume, length/breadth ratio, calculat- bons, percent moisture and percent lipids for 15 un-

Table 1 . Summary of Florida Bald Eagle egg characteristics.

Shell Thickness Length Breadth Calculated Calcuiated Without (L) (B) Volume Fresh Mass Membranes

(mm) (mm) (mm^) L/B Ratio ( g) (mm) N 392 392 392 392 392 395 Minimum 64.38 48.34 82.30 1.166 90.92 0.312 Maximum 79.50 59.88 140.20 1.517 154.92 0.553 Mean 71.04 55.37 111.08 1.284 122.71 0.453 Standard Deviation 2.732 1.690 9.233 0.051 10.20 0.035 326 Short Communications VoL. 36, No. 4

Table 2. Summary of chlorinated hydrocarbon pesti- (Fyfe et al. 1988, Nisbet 1989, Risebrough 1989). Mean cide residues in 15 unhatched Florida Bald Eagle eggs, productivity of Florida Bald Eagles during the years of 1984-91. Data are corrected to calculated fresh egg mass- egg collection was 1.10 young/occupied territory (Nes- es bitt et al. 1998), and above the minimum of 1.0 young/

occupied territory that Wiemeyer et al. (1993) considered as representing a healthy population. Based on Stan- these data, we believe that by 1984 the population of nest- Maxi- Mini- dard ing Bald Eagles in the areas of Florida from which we Mean mum mum Devia- collected eggs were reproducing at a rate that met the (ppm) (ppm) (ppm) tion criteria suggested by Wiemeyer et al. (1993). This pop- DDE 2.47 10.10 0.66 2.35 ulation was relatively free of pesticide contamination and DDD 0.05 0.58 0.0 0.14 that eggshell thinning was no longer a problem. DDT 0.24 3.89 0.0 0.94 HCB ND* Resumen.—Las medidas y calculos de las medidas de 395 Alpha-BHC ND huevos de aguilas calvas {Haliaeetus leucocephalus) colec- Gamma-BHC (lindane) ND tados en Florida desde 1985-91 fueron evaluadas por me-

Beta-BHC ND dio de relacion estadistica para el ano de coleccion, la- Heptachlor ND titud del condado donde fueron colectados, sexo del Aldrin ND polluelo y orden de salida del huevo. No se encontraron Octachlorostyrene ND correlaciones significantes. Se hicieron analisis de resi- Heptachlor epoxide 0.01 0.07 0.00 0.02 duos de pesticidas organoclorados y bifenil policlorina- Oxychlordane 0.06 0.26 0.00 0.06 dos en 15 huevos sin empollar. Con excepcion de una Gamma-chlordane 0.04 0.15 0.00 0.04 nidada, los residues organoclorados fueron bajos. Alpha-chlordane ND [Traduccion de Cesar Marquez] Transnonachlor 0.29 1.06 0.00 0.25 Mirex ND Acknowledgments Dieldrin 0.10 0.66 0.00 0.15 Cooperation for this project was given by the Florida Endrin ND Game and Fresh Water Fish Commission, in particular Methoxychlor ND Don Woods and Steve Nesbitt; The University of Florida, Toxaphene ND especially Michael Collopy, Petra Bohall Wood, and Rob- PCB 1260 5.13 15.47 0.00 5.50 ert Rosen; and the U.S. Fish and Wildlife Service’s En- PCB 1248 0.02 0.24 0.00 0.06 dangered Species Program and Regions 2 and 4. Grateful thanks are due to our funders and the Sutton PCB 1254 5.82 28.15 0.00 8.03 numerous Board of Directors. Many Sutton employees worked tire- Percent moisture 80.78 83.60 76.00 2.04 lessly to make the restoration project successful, Alan Be- Percent lipids 5.15 12.00 2.20 2.19 ske, Gwyn McKee, and Sheryl Tatora in particular. James ND = None detected above detection limit of 0.1 ppm or lower. Enderson loaned eggshell measuring equipment. The manuscript was greatly improved by comments from Stanley N. Wiemeyer, James C. Bednarz, Sally Jenkins, hatched eggs are presented in Table 2 as benchmark data and two anonymous reviewers. for possible future information on this population. Literature Cited Discussion Anderson, D.W. and J.J. Hickey. 1972. Eggshell changes Bald Eagle body size is known to increase with increas- in certain North American birds. Pages 514-540 in ing latitude (Stalmaster 1987), but we found no correla- K.H. Voous [Ed.], Proc. XV Int. Ornithol. Congr. Leiden, tion of egg size characteristics with the small latitude span Germany. we sampled. We speculated that eggs laid later in a clutch Bond, G.M., R.G. Board, and V.D. Scott. 1988. A com- might be smaller than the first, but our data failed to parative study of changes in the fine structure of avian detect such a trend. Likewise, sex of the eagles hatched eggshells during incubation. Zool.J Linn. Soc. 92:105- did not correlate with size of the egg or hatch order. 113. We expected an increase in eggshell thicknesses and Broley, C.L. 1958. The plight of the American Bald Ea- lessening of chlorinated hydrocarbon residues during the gle. Audubon 60:162-163, 171. years of our study because most uses of DDT in the U.S.A. Bunck, M.M., J.W. Spann, O.H. Patee, and W.J. Fleming have been banned; however, our thickness data did not 1985. Changes in eggshell thickness during incuba- show a change over time during the period of our study. tion: implications of evaluating the impact of organ- The residues for our eggs, except one egg with high DDE ochlorine contaminants on productivity. Bull. Environ residues, are below the threshold levels indicated by Contam. Toxicol. 35:173-182. some authors as sufficient to affect raptor productivity Enderson, J.H., G.R. Craig, W.A. Burnham, and D.D. December 2002 Short Communications 32V

Berger. 1982. Eggshell thinning and organochlorine B.-U. Meyburg and R.D. Chancellor [Eds.], Raptors residues in Rocky Mountain peregrines, Falco peregti- in the modern world. WWGBP, Berlin, Germany. nus, and their prey. Can. Field-Nat. 96:255-264. Romanoff, A.L. and AJ. Romanoff. 1949. The avian egg. Food and Drug Administration. 1973. Pesticide analyt- John Wiley and Sons, Inc., New York, NY U.S.A. Sherrod, S.K., M.A. Jenkins, G. McKee, D.H. Wolfe, ical manual. Vol. 1, Washington, DC U.S.A. Jr , and S. Tatom. 1989. Restoring nesting Bald Eagle Fyfe, R.W., R.W. Risebrough, J.G. Monk, W.M. Jarman, Haliaeetus leucocephalus populations to the southeast- D.W. Anderson, L.F. Kief, J.L. Linger, I.C.T. Nisbet, ern United States. Pages 353-357 in B.-U. Meyburg W. Walker, II, and BJ. Walton. 1988. DDE, produc- and R.D. Chancellor [Eds.], Raptors in the modern tivity, and eggshell thickness relationships in the ge- world. WWGBP, Berlin, Germany. nus Falco. Pages 319—335 in T.J. Cade, J.H. Enderson, Stalmaster, M.V. 1987. The Bald Eagle. Universe Books, C.G. Thelander, and C.M. White [Eds.], Peregrine New York, NY, U.S.A. Falcon populations: their management and recovery. Stickel, L.F., S.N. Wiemeyer, and LJ. Blus. 1973. Pesti- The Peregrine Fund, Boise, ID U.S.A. cide residues in eggs of wild birds: adjustment for loss Gerrard, J.M, and G.R. Bortolotti. 1988. The Bald Ea- of moisture and lipid. Bull. Environ. Contam. Toxicol 9 gle. Smithsonian Institution, Washington, DC U.S.A. 193-196. Howell, 1963. 1961 census of Bald Eagle J.C. The some Stickel, W.H., L.F. Stickel, R.A. Dyrland, and D.H. nests in east-central Florida. Auk 79:716-718. Hughes. 1984. Comparison of methods of preserving Nesbitt, S.A., M.A. Jenkins, S.K. Sherrod, D.A. Wood, tissues for pesticide analysis. Environ. Monit. Assess. 4- A. Beske, J.H. White, P.A. Schulz, and S.T. Schwik- 113-118. ert. 1998. Recent status of Florida’s Bald Eagle pop- Terepka, A.R. 1963. Organic-inorganic interrelationships

ulation and its role in eagle reestablishment efforts in in avian egg shell. Exp. Cell Res. 30:183-192. the southeastern United States. Proc. Annu. Conf. Walborn, E.B. 1991. Use of morphometric measure- Southeast. A.ssoc. Fish Wildl. Agencies 52:377-383. ments in determining sex of southern Bald Eagles. Nisbet, I.C.T. 1989. Organochlorines, reproductive im- M.S. thesis, Oklahoma State University, Stillwater, OK U.S.A. pairment, and declines in Bald Eagle (Haliaeetus leu- Wiemeyer, S.N., C.M. Bunck, and Stafford. 1993. cocephalus) populations: mechanisms and dose-re- C.J. Environmental contaminants in Bald Eagle eggs sponse relationships. Pages 483-489 in B.-U. Meyburg (1980-1984) and further interpretations of relation- and R.D. Chancellor [Eds.], Raptors in the modern ships to productivity and shell thickness. Arch. Environ. world. WWGBP, Berlin, Germany. Contam. Toxicol. 24:213—227. Risebrough, R.W. 1989. Toxic chemicals and birds of prey: discussion at Eilat in 1987. Pages 515-525 in Received 7 January 2002; accepted 25 July 2002 J Raptor Res. 36(4):328-331 © 2002 The Raptor Research Foundation, Inc.

Osprey Ecology in the Mangroves of Southeastern Brazil

Robson Silva e Silva^ Rua Sdo Jose 48/31, 11040-200, Santos, SP, Brazil

Fabio Olmos Largo do Paissandu 100/4C, 01034-010, Sdo Paulo, SP, Brazil

Key Words: Osprey; Pandion haliaetus; Brazil; diet; man- Winter is the driest season, the lowest rainfall occurring grove, wintering ecology. in July-August, the highest values occurring between Sep- tember-March (Olmos and Silva e Silva 2001). For a general description of the area’s geography and environ- The Osprey {Pandion haliaetus) is a widely distributed ment, see CETESB (1991) and Olmos and Silva e Silva raptor found in every continent but Antarctica. The Eur- ( 2001 ). asian nominate and North American subspecies {P. h. car- The main feature in the study area is a channel (Pia- ohnensis) extensive migrations, the latter being a make gaguera channel) bisecting it and connecting Santos Bay trans-equatorial migrant wintering in United States (Flor- to the estuarine area inland. This broad (ca. 1 km wide) ida), Mexico, Central America and South America from channel is mostly man-made and regularly dredged to Colombia to Argentina and Chile (Poole 1989, del Hoyo allow for the passage of cargo ships serving the local steel fertilizer et al. 1994, Martell et al. 2001). and plants. Because of dredging and silting, there are large mudflats along the channel. naviga- In Brazil, Ospreys have been recorded in almost every Ten tion buoys and six concrete towers dot the entire length state and month, but most records were made between of the channel and are used as perches by feeding Os- September and April (Sick 1997). The Amazon basin, preys. Prey remains accumulate on top of these buoys where reports are most seems to be the main common, and towers, making collecting the collection of dietary wintering area for Ospreys in the country, but there are data simple. Three rivers (Quilombo, Casqueiro, and Cu- also clusters of records in coastal localities (Sick 1997, batao) empty into the channel. Olmos and Silva e Silva 2001). Band recoveries made in Diet and behavioral data were collected as part of a Brazil show the birds come from the Mid-Atlantic and broader study of the mangrove avifauna conducted from northeastern USA (Poole and Agler 1987). March 199T-July 2000 during 231 field-days (Olmos and Silva e Silva 2001). Data on Osprey abundance through- Despite being a well-known species in its breeding out the year and habitat use were gathered between Au- grounds (del Hoyo et al. 1994), there is little information gust 1995-November 1996, when we made 36 standard- on the wintering ecology of Ospreys in South America ized bird censuses by boat along a 19.25 km transect (Saggese et al. 1996), although detailed studies have covering all habitats present (Olmos and Silva e Silva been made in Africa (Prevost 1982, Boshoff and Palmer 2001 ). 1983). Ospreys spend most of the year (six or more Habitat classification was adapted from the mapping months) in their wintering grounds, so information on made by Sao Paulo state’s environmental agency (CE- their ecology during this period is critical for a clearer TESB 1991) and represents a gradient of mangrove tree understanding of their life-histories and the pressures cover. Habitat categories sampled were: mangrove forest with touching and cover, de- laced by the birds outside the breeding season. Here, we mostly canopies complete graded mangrove with many gaps between trees making provide an account of the ecology of Ospreys using a a patchwork of clearings, mangrove degraded by pollu- mangrove eco.system in southeastern Brazil, the first such tion, groups of mangrove trees, and large areas of her- study in South America. baceous growth dotted by dwarfed mangroves, a mosaic of mudflats (with scattered mangrove trees), and ex- SruDY Area AND Methods posed mudflats without any tree cover. For a detailed de- The study was conducted in the mangrove ecosystem scription of habitats see Olmos and Silva e Silva (2001) that covers the estuarine area between Sao Vicente Island Feeding Ospreys were observed opportunistically with and the mainland, in the coast of Sao Paulo state, south- the help of spotting scopes and binoculars with the aim eastern Brazil (ca. 23°53'S, 46°23'W). This area, belong- of identifying the captured prey. Prey remains accumu- ing to the Santos and Cubatao counties, is part of the lated on buoys and towers were recovered during regular major mangrove ecosystem located in the region known checks and identified to the lowest possible taxonomic as Baixada Santista, covering 120 km^, and located in one level by comparison to reference material. of the most populated and developed areas in Brazil (Lamparelli 1999). The local climate is hot and humid, Results with annual rainfall ranging from 2000 to over 2500 mm. Ospreys were first recorded along the Piagaguera channel in 1986 (Olmos 1989). Interestingly, the species was

^ E-mail address: [email protected] not found there earlier in the 20th century (Luederwaldt

328 December 2002 Short Communications 329

Figure L Monthly numbers of Ospreys censused in the Santos-Cubatao mangroves, southeastern Brazil, between August 1995-November 1996.

1919). It is almost impossible to tell adult birds from From year-round census data. Ospreys had higher lin- young ones under field conditions (Boshoff and Palmer ear densities along rivers bordered by mangrove forest (x 1983), but we never observed newly-fledged Ospreys, = 0.71 birds/km) and mangroves degraded by pollution with their characteristic speckled plumage. (0.70 birds/km) compared to mudflats (0.2 birds/km) Ospreys are recorded in Santos-Cubatao throughorxt and degraded mangrove (0.01 birds/km, Fij 440 = 14 09, the year. Census data show a peak during the austral sum- P < 0.0001). Densities in mangrove forest and mangrove mer and a minimum of three birds during the winter degraded by pollution were not different, as well as dif- (Fig. 1). Most (47%) records made during the censuses ferences in densities between mudflats and degraded were along the Cascalho River, where channel margins mangroves (Tukey HSD test, both P < 0.001). are dominated by mangroves degraded by pollution (Ol- Most fish seem to be captured alive, but in November e Silva mos and Silva 2001). 1996, we did record an Osprey taking a dead fish floating on the surface. The most important prey were mullets (Mugil spp.) (76.7%) and rhomboid mojarra {Diapterus Table 1. Prey items of wintering Ospreys in the man- rhomheus) (17.8%; Table 1). Only two freshwater fish, groves of Santos and Cubatao, Brazil. Unidentified fish common trahita {Hoplias malabaricus) and Brazil geopha- were excluded. gus {Geophagus brasiliensis) were recorded. One mullet

{Mugil platanus) left whole on a tower was 41. .5 cm TL

Species N Percent and weighed 590 g, while a Diapterus rhombeus found m

the same circumstances was 30 cm and 490 g. Based on Mullets prey remains and observations, fish smaller than 20 cm Mugil sp. 69 76.7 TL seem to be rare in the diet of Ospreys in southeastern Rhomboid mojarra Brazil. Diapterus rhombeus 16 17.8 We rarely observed Ospreys hovering or flying low over Snooks the water before capturing a fish. Once, an Osprey Centropomus sp. 2 2.2 caught a dying fish on the surface while “hovering.” In Common trahita most instances, the birds would soar over the water and Hoplias malabaricus 1 1.1 plunge dive rapidly after locating a fish. It was Brazilian mojarra common for the birds to abort several dives (up to nine in a row) Eugerres brasilianus 1 1.1 Brazil geophagus before actually touching the water. Ten out of plunge dives by different birds were suc- Geophagus brasiliensis 1 1,9 14 cessful (71%), with nine fish carried away and one falling Total 90 100 back to the water. After taking a fish, the birds would fly 330 Short Communications VoL. 36, No. 4

to one of the available towers, buoys, trees, or when the and Tarboton 1983). The presence of Ospreys in Brazil prey was too heavy, even a mudflat. All hsh were eaten during April-August show non-breeders, juveniles, stay in head first, discarding opercula and gills. Mullet viscera their wintering range. were also discarded. Usually only the tail would remain Although Sick (1997) attested, without details, that Os- but, sometimes, we would find the posterior half of a preys sometimes take mammals and birds when winter- large mullet. After feeding, the bird would fly dragging ing, the only documented food items of Ospreys in Brazil its feet in the water for over TO m. Sometimes up to three were fish, making the diet seem less diverse compared to birds were seen fishing in the same small area. When one breeding areas (Wiley and Lohrer 1973). Mullets are de- was successful the others would chase it amid much call- tritus-eating fish abundant in Brazilian estuaries, where ing, trying to steal its fish. they gather in shoals year-round (Menezes 1983). Their A curious behavior was observed on 22 August 1997, abundance, size, and the habit of sunning close to the at the Pia^aguera channel. One Osprey, while holding a surface make them ideal prey for a plunge diver like the tree branch, was seen flying and calling after another in- Osprey. In fact, the only former report of a prey taken dividual. The second bird would perch, also calling. The by an Osprey in Brazil refers to a mullet (Mugil incilis) first bird flew out of sight but came back quickly, always (Martuscelli 1992), also taken in a mangrove area in calling, without the branch. Both birds then began to southern Sao Paulo state. Mullet was also the main prey soar, always calling, making several aborted dives. After taken by wintering Ospreys in mangroves and estuaries one Osprey finally captured an unidentified fish, it flew in Senegal (Prevost 1982) and South Africa (Boshoff and away being followed by the other bird. An Osprey flying Palmer 1983). The availability of mullet may probably ex- while holding a tree branch was also seen on 18 July plain why Ospreys seem to be the most common in coast- 2000; this bird was chasing a Crested Caracara (Polyborus al areas, especially estuaries and mangroves (Haver- plancus) but we soon lost sight of them. schmidt and Mees 1994). Fish were also the only prey , Contrary to the behavior reported in some wintering recorded as taken by Ospreys in freshwater habitats in

areas (Boshoff and Palmer 1983), Ospreys were very vo- Peru (Willard 1985) and Argentina (Saggese et al. 1996), cal in Santos-Cubatao throughout the year, especially the detritus-eating Prochilodus sp. being reported by both when two birds came close to each other. It was common studies. We observed a high capture success (71%) for a to see two Ospreys soaring together with Black Vultures limited number of foraging attempts on fish, but not out-

( Coragyps atratus) while calling. They would also call when side the 40-70% range reported by studies elsewhere we approached the perch of a feeding bird, which caused (Poole 1989, del Hoyo et al. 1994).

It to fly with its prey. There is no direct or intensive persecution of Ospreys Yellow-headed Caracaras {Milvago chimachima) benefit in southeast Brazil. Nevertheless, their reliance on detri- from Ospreys by scavenging fish remains from the feed- tus-eating fish might be problematical. The Santos-Cu- ing perches, sometimes waiting beside a feeding Osprey. batao estuary receives the discharges of one of the major

Crested Caracaras are more aggressive and actively try to industrial areas in Brazil, well-known in the 1980s for its steal fish from the Ospreys; sometimes up to four cara- high pollution levels (Gutberlet 1996). Despite improve-

caras may join in a chase after an Osprey carrying a fish, ments, the sediments still hold high levels of heavy metals but we never saw them being successful. Interestingly, and organochlorines such as Hexachlorobenzene (HCB) Great Egrets {Casmerodius alhus) would expel Ospreys and Polycyclic aromatic hydrocarbons (PAHs). For ex- Irom their feeding perches, while Kelp Gulls {Larus dom- ample, sediments from the Piagaguera channel hold imcanus), known to steal Ospreys’ food in South Al'rica 109.200 to 733.700 [xg/kg of benzopyrene, some of the (Boshoff and Palmer 1983), ignore them in Brazil. largest concentrations in the world (CETESB 2001). Ospreys did not seem to be actively persecuted by local These contaminants may be ingested by fish like mullet, people and the many fishermen using the mangroves. feeding on detritus and benthic algae, and accumulated Nevertheless, on 26 December 1996, a female was found and transferred to piscivores like Ospreys. Thankfully, with a wounded wing, perhaps the result of being shot. most contaminants seem to be trapped in the sediment

This bird is now in the ornithological collection of the and mullet samples generally have small concentrations Museu de Zoologia da Universidade de Sao Paulo (CETESB 2001), although this situation may change if (MZUSP 74346). dredging makes the compounds available again in the water column. Discussion

The lack of records of newly-fledged Ospreys with their RF..SUMEN.—Las aguilas pescadoras {Pandion haliaetus) son characteristic speckled plumage suggests only birds over registradas todo el ano en los manglares de Santos-Cu-

1 yr-old migrate to the study area. The year-round pres- batao al suroriente del Brasil, con un pico de abundancia ence of Osprey in Brazil raises the possibility the birds entre diciembre y marzo. Las aves usan todos los habitat might breed in South America, but no evidence has been del manglar pero las densidades lineares mas altas ocur- found so far (Sick 1997). Nevertheless, nesting in a win- ren a lo largo de rios bordeados por bosques de manglar = tering area has been documented in South Africa (Dean {x 0.71 aves/km) y manglares degradados por polu- December 2002 Short Communications 331

cion (x = 0.70 aves/km). Las ^uilas pescadoras fueron Haverschmidt, E. and G.F. Mees. 1994. Birds of Surina- registradas comiendo unicanaente pescado y mostraron me. Vaco Press, Paramaribo, Suriname. una alta tasa de exito (71% de los intentos). Los salmo- IuAMPARELLI, C.C. 1999. Mapeamento dos ecossistemas netes {Mugil spp.) fueron el item de comida mas comun costeiros do estado de Sao Paulo. Secretaria do Meio (77%), seguido por las mojarras romboides {Diapterus Ambiente/CETESB, Sao Paulo, Brazil. rhombeus) (18%). A pesar de la historia de alta polucion Luederwaldt, H. 1919. Os manguesaes de Santos. Rev industrial del area, los niveles de contaminantes en las Mus. Paulista 11:310-409. especies presa consumidos por el aguila pescadora fu- Martell, M.S., C.H. Henny, RE. Nye, and M.J. Soi.ensky eron bajos, y la especie no fue perseguida por los pob- 2001. Fall migration routes, timing, and wintering ladores locales. sites of North American Ospreys as determined by sat- [Traduccion de Cesar Marquez] ellite telemetry. Condor 103:715-724. Martuscelli, P. 1992. Notas sobre aves pouco conheci- ACKNOWr .EDGMENTS das do estado de Sao Paulo. Pages 82-83 in Anais do

This work was possible through grants received from VI Encontro Nacional de Anilhadores de Aves, EDU- Funda^ao O Boticario de Protegao a Natureza, MacAr- CAT, Pelotas, Brazil. thur Foundation and Ultrafertil S.A. to both authors. We Menezes, N.A. 1983. Guia pratico para conhecimento e are very grateful for their timely support over the years. identificayao das tainhas e paratis (Pisces, Mugilidae) We also thank Maria do Carmo Amaral (Cubatao Zoo, do litoral Brasileiro. Rev. Brasil. Zool. 2:1-12. Cotia-Para Ecological Park) for saving the Osprey speci- Olmos, E. 1989. A avifauna da baixada do polo industrial men now in the MZUSP. Escobar and the personnel Joel de Cubatao. Rev. Bras. Biol. 49:373-379. at Nautica da Ilha provided invaluable support when we and R. Silva e Silva. 2001. The avifauna of a needed to deal with boats and outboard motors. We wish southeastern Brazilian mangrove swamp. Int. J. Orm- to thank Mark Martell, Alan E. Poole, and Richard O. thol. 4:137-207. Bierregaard, Jr. for comments and suggestions on improving the manuscript. Poole, A.F. 1989. Ospreys: a natural and unnatural history. Cambridge Univ. Press, Cambridge, U.K. Lu erature Cited AND B. Agler. 1987. Recoveries of Ospreys band-

ed in the United States, 1914-84. y. Wildl. Manage. 51. Boshoff, A.E. N.G. Palmer. 1983. Aspects bi- and of the 148-155. ology and ecology of the osprey in the Cape Province, Prevost, Y.A. 1982. The wintering ecology of Ospreys in South Africa. Ostrich 54:189-204. Senegambia. Ph.D. dissertation, University of Edin- Companhia Estadual de Tecnologia e Saneamento Am- burgh, Scotland. biental. 1991. Avaliayao do estado de degradagao dos Saggese, M.D., E.R. De Lucca, S.F. Krapovickas, and ecossistemas da Baixada Santista. Sao Paulo, Brazil. E.H. Haene. 1996. Presencia del aguila pescadora

. 2001. Levantamento da contaminagao ambiental {Pandion haliaetus) en Argentina y Uruguay. Hornero do sistema estuarino Santos/Sao Vicente. CETESB, 14:44-49. Sao Paulo, Brazil. Sick, H. 1997. Ornitologia Brasileira. Editora Nova Eron- Dean, and W.R. Tarboton. 1983. Ospreys breed- W.R.J. teira, Rio de Janeiro, Brazil. ing records in South Africa. Ostrich 54:238-239. Wiley, J.W. and F.E. Lohrer. 1973. Additional records of Gutberlet, 1996. Cubatao: desenvolvimento, exclusao J. non-fish prey taken by Ospreys. Wilson Bull. 85:468- social, degrada^ao ambiental. Edusp/Fapesp, Sao 470. Paulo, Brazil. WiLlARD, D.E. 1985. Comparative feeding ecology of a. 1994. del FIoyo, J., Elliott, and J. Sargatal (Eds.). twenty-two tropical piscivores. Ornithol. Monogr. 36. Handbook of the birds of the world. Vol. 2. New world 788-797. vultures to guineafowl. Lynx Edicions, Barcelona, Spain. Received 8 February 2002; accepted 3 July 2002 / RapiorRes. 36(4) :332-334 © 2002 The Raptor Research Foundation, Tnc.

Diet of Breeding Tropical Screech-Owls (Otus choliba) in Southeastern Brazil

Jose Carlos MottaJunior' Departamento de Ecologia, Instituto de Biociencias da Universidade de Sdo Paulo, 05508-900, Sdo Paulo, SP, Brazil

Key Words: Tropical Screech-Owl; Otus choliba; breeding in the pellets. Both prey remains and the reference col- dieL; prey biomass; Brazil. lection were deposited at the Departamento de Ecologia, Universidade de Sao Paulo, Brazil.

The Tropical Screech-Owl {Otus choliba) occurs east of Results and Discussion the Andes Mountains from Costa Rica to Uruguay and All three nests were in cavities located at a height of northern Argentina, and is also found throughout much 1.0-1. 5 in sp. tree ol Brazil (Meyer de Schauensee 1966, Burton 1992, Sick m dead Eucalyptus trunks, presumably made by woodpeckers originally. Smith pointed 1993). It is one of the most common and widespread (1983) neotropical owl species inhabiting forest edges, open out that Tropical Screech-Owl nests are typically located in cavities. In spite field excursions woodlands, savannas, and other habitats with some ar- tree of the monthly boreal cover, including urban areas (Sick 1993, del Hoyo to the study area during 1992-93, nests were only found on 25 November 1992 (Nest 1 with one female and three et al. 1999). Despite its commonness and widespread dis- , owlets), 28 October 1993 (Nest with one female and tribution, little ecological information is available on this 2, owlets), 6 fe- species, except for some data concerning natural history two and November 1993 (Nest 3, with one three owlets). three adult inside and breeding (Thomas 1977, Smith 1983). Food habits male and The females cavities were captured by and weighed with a spring have been described only qualitatively (e.g., Thomas hand scale. The mean and standard deviation of body mass was 1977, Smith 1983, Gallardo and Gallardo 1984). Here, I the back provide more detailed information about the diets of 128.3 ± 11.7 g. Subsequently, adults were placed nestling and adult Tropical Screech-Owls during the into the cavities. Prey remains were collected the first breeding season. Data on nest locations and the timing time the nest was found and shortly after owlets fledged. of reproduction in southeastern Brazil are also present- Analysis of pellets and pellet debris revealed at least 34 ed species of prey consumed. Invertebrates, mostly orthop- terans such as Lutosa brasiliensis, were most frequent in

Study Area and Methods the diet (Table 1). Spiders (Lycosidea) and ants (For- The study was conducted at Chacara Mattos/Faber-Cas- micidea) were also important numerically. In terms of tell (21°59'S, 47°56'W), located 1 km west of the city of biomass, invertebrates also prevail, however, the few ver- Sao Carlos, Sao Paulo State, Brazil. The 90 ha study area tebrates found, represented a third of the consumed bio- consists spp. plantations sec- primarily of Pinus with some mass (Table 1). ondary-grassland savanna. small patch ha) of dis- A (3 The mean body mass of prey consumed by Tropical turbed gallery forest also occurs in this area. The land- Screech-Owls was 0.93 ± 2.35 g, ranging from 0.02-28.80 scape surrounding the study area is sugar cane {N = 309 prey items). Most prey (73.5%) weighed be- plantations and the outskirts of the city of Sao Carlos, g tween 0. 1-1.0 g. fhe climate is a transition between Koppens’s Cwai and Awi, or rainy tropical with a wet (October-March) and a Tropical Screech-Owls only were observed foraging at dry (April-September) season (Tolentino 1967). night. On two occasions, an individual was observed leav- Four samples of pellet debris (representing ca. 30 pel- ing a perch on a tree and, in flight, capturing insects on lets) and six complete pellets were collected from three the leaves of another tree. On another occasion, an in- occupied nest cavities. This material was washed through dividual left a perch on a bush and captured an uniden- a line mesh screen (0.2 mm) and oven-dried (5(LC) for tified invertebrate on the ground. Gallardo and Gallardo 24 hr for storage arid analysis. Prey remains were identi- (1984) reported a similar behavior in Tropical Screech- hed by comparison with a reference collection made Owls. 1 have observed these screech-owls catching insects from material from the study. I also measured the mass in flight, particularly in the vicinity of artificial light ol prey items collected from the study area. Individuals m the prey remains were counted by pairing mandibles, sources, which was also reported by Smith (1983) and with the exception of beetles and ants, which were count- Sick (1993). During the period of activity (1800-0600 H) ed by the number of heads, and scorpions by the number owls were observed on perches waiting for potential prey; of stings. The analyzed prey remains presumably were therefore, this species probably should be classified as a from owlets possibly adults. I also assumed that ver- and “sit-and-wait” forager, which is typical for the genus Otus tebrate prey were entirely ingested like invertebrates, be- (Jaksic and Carothers 1985). cause crania and other body bones were always present The qualitative studies of Thomas (1977) and Smith (1983) indicated that the diet of Tropical Screech-Owls

' E-mail address: [email protected] consisted mostly of insects in Costa Rica and both insects

332 December 2002 Short Communications 333

Table 1. Prey items found in pellets and pellet debris of Tropical Screech-Owls in southeastern Brazil, with their percentages in relation to total number and estimated biomass (g). Activity periods and sites of prey were determined based on field observations and information provided by Manoel M. Dias (pers. comm.).

Pfrcfne PFRt:FNT Prey Items Aciivn Y Period Activity Site Number Biomass

Rodents Bolomys lasiurus Nocturnal/ crepuscular, Ground 0.3 10.1 Diurnal Calomys tener Nocturnal/crepuscular Ground 0.3 3.6 Oligoryzomys nigripes Nocturnal/ crepuscular Foliage/branches, 0.3 6.0 Ground Opossums

Gracilinanus sp. Nocturnal/ crepuscular Foliage/branches, 0.3 5.7 Ground

Snakes

Unidentified small sp. p ? 0.3 3.3 Amphibians

Hylidae (unidentified sp.) Nocturnal/crepuscular Foliage/branches 0.3 5.3

SUBTOTAL VERTEBRATES — — 1.9 34.1

Scorpions Bothriurus spp. Nocturnal/crepuscular Ground 3.6 1.0 Tityius bahiensis Nocturnal/ crepuscnlar Ground 0.3 0.1

Spiders

Lycosidae (unidentified sp.) Nocturnal/ crepuscular Ground 11.3 5.9 Unidentified spp. p ? 1.3 0.8 Harvestmen

Opiliones (unidentified sp.) p p 0.3 0.1

Insects

Blattidae {Parahormetica sp.) Nocturnal/crepuscular Ground 1.6 3.2 Blattidae (unidentified sp.) ? ? 0.3 0.2 Termitidae (workers) Nocturnal/crepuscular, Ground 2.6 0.2 Diurnal Acrididae spp. Diurnal Foliage/branches 2.9 1.4 Tettigoniidae (Copiphorinae) Nocturnal/crepuscular Fo liage / branch e s 5.8 6.0 Tettigoniidae (Conocephalinae) Nocturnal/crepuscular Foliage/branches 0.6 0.2 Gryllacrididae {Lutosa brasiliensis) Nocturnal/crepuscular Ground 41.1 34.2 Gryllidae Nocturnal/crepuscular Ground 1.6 1.6

Unidentified Orthoptera ? ? 0.6 0.3 Mantidae Nocturnal/crepuscular Foliage/branches 4.2 2.8 Carabidae (small unidentified spp.) Nocturnal/crepuscular Ground 1.0 0.1 Scarabaeidae (Rutelinae) Nocturnal/crepuscular Foliage/branches 0.3 0.3 Scarabaeidae (Dynastinae) Nocturnal/crepuscular Ground 2.6 3.1 Cerambycidae Nocturnal/crepuscular Tree trunks 1.6 2.4

Unidentified adult Coleoptera ? p 1.0 0 4 Unidentified larvae Coleoptera p ? 1.0 0.4

Lepidoptera (unidentified small moth) ? p 0.3 0 1

Lepidoptera (unidentified caterpillar) ? Foliage/branches 1.0 0 3 Formicidae {Atta sexdens queen) Nocturnal/ crepuscular, Ground 0.3 0.2 Diurnal Formicidae {Camponotus Nocturnal/crepuscular, Tree trunks, 5.2 0.1 Diurnal Ground Formicidae (Dorylinae) Nocturnal/ crepuscular, Ground 1.9 0 1 Diurnal

Formicidae (unidentified spp.) ? p 3.2 0 1

Other unidentified Insecta ? ? 0.3 02 SUBTOTAF INVERTEBRATES — — 98.1 65 9 .

334 Short Communications VoL. 36, No. 4

and vertebrates in Venezuela, respectively. Prey taken by revised the Spanish text. This work was a small part of a these owls include katydids, beetles, cockroaches, small Ph.D. dissertation sponsored by Coordenacao De Aper- feigoamento Ce Pessoal De Nivel Superior and World snakes, and rodents (Thomas 1977, Smith 1983, this Wildlife Fund/Brazil. study). Larger species like Otus asio and O. kennicottii seem to include proportionally more vertebrates in their Literature Cited diets (e.g., Ritchison and Cavanagh 1992, del Hoyo et al. Burton, J.A. (Ed.). 1992. Owls of the world: their evo- 1999). On the other hand, smaller species such as O. lution, structure, and ecology, 3rd Ed. Peter Lowe, tnchopsis, O. flammeolus, and O. choliba appear to be mostly Wallingford, U.K. insectivorous (Ross 1969, del Hoyo et al. 1999, this DEL Hoyo, A. Elliott, and Sargatai.. 1999. Hand- study) J., J. book of the birds of the world. Barn Owls to hum- The frequent consumption of the terrestrial arthro- mingbirds. Vol. 5. Lynx Edicions, Barcelona, Spain, pods, Lutosa brasiliensis (Lycosidae) and others (68.5% by Gai.iardo, L.A. AND J.M. Gallardo. 1984. Observaciones number and 63.3% by biomass) suggests that prey are realizadas sobre el comportamiento de Otus choliba en often captured on the ground (Table 1). A similar pat- liberdad. Comun. Mus. Argent. Cienc. Nat. Bernardino tern in the prey data supports that the Tropical Screech- Rivadavia Zool. 4:109-114. Owls were essentially nocturnal; the diet consists mainly JAKSIC, F.M. AND J.H. Carothers. 1985. Ecological, mor- of night prey (76.8% by number and 81.5% by biomass; phological, and bioenergetic correlates of hunting Table 1). mode in hawks and owls. Ornis Scand. 16:165-172. Meyer de Schauensee, R. 1966. The species of birds of Resumen.—Se estudio la dieta del Autillo Choliba {Otus South America and their distribution. Livingston, Nar- choliba) durante el periodo reproductivo, entre los meses berth, PA U.S.A. de octubre y diciembre de 1992 y 1993, en nna localidad Ritchison, G. and P.M. Cavanagh. 1992. Prey use by del Sudeste de Brasil. Se identificaron por lo menos 34 Eastern Screech-Owls: seasonal variation in central especies de presas a partir de egagropilas, directamente Kentucky and a review of previous studies. Raptor colectadas en tres nidos ubicados en cavidades de troncos J. Res. 26:66-73. muertos a 1.0-1. 5 m del suelo. Insectos, en especial Lu- Ross, A. 1969. Ecological aspects of the food habits of tosa brasiliensis (Gryllacrididae) y otros ortopteros, arahas insectivorous screech-owls. Proc. West. Found. Vertebr. y escorpiones forraaron la base de la dieta. Aunque los Zool 1:301-344. mvertebrados fueron los mas importantes numerica- Sick, H. 1993. Birds in Brazil. A natural history. Princeton mente (98.1% del total de 309 individuos), los vertebra- Univ. Press, Princeton, NJ U.S.A. dos tuvieron representacion significativa en terminos de Smith, S.M. 1983. Otus choliba. Pages 592-593 in D.H biomasa consumida estimada (34.1% del total de 286.0 Janzen [Ed.], Costa Rican natural history, Univ. of g) La inayoria de las presas eran nocturnas y terricolas, Chicago Press, Chicago, IL U.S.A. mdicando los habitos de caza de esta lechuza. Thomas, B.T 1977. Tropical Screech-Owl nest defense [Traduccion del autor] and nestling growth rate. Wilson Bull 89:609-612. Acknowledgments Tolentino, M. 1967. Estudo critico sobre o clima da re- giao de Sao Carlos. Concurso de Monograhas Muni- 1 thank A.W. Faber-Castell S/A for facilities in the study cipals, Sao Carlos, Brazil. site. The entomologists Manoel M. Dias and Alejo M. Lar- rambebere helped with invertebrate identihcation. Mar- tha Desmond, F.R. Gehlbach, Gary Ritchison, and Clint Received 17 September 2001; accepted 5 July 2002 W Boal made valuable comments. Diego Queirolo kindly Associate Editor: Clint W. Boal Letters

Comments on the First Nesting Record of the Nest of a Slaty-backed Forest-Falcon {Micrastur mirandollei) in the Ecuadorian Amazon

De Vries and Melo (2000,/. Raptor Res. 34:148-150) recently reported the first documented nest of a Slaty-backed Forest-Falcon {Micrastur mirandollei), based on their studies in Yasuni National Park, Ecuadorian Amazon. Certain details they reported differ markedly from the nesting habits and behavior that my colleagues and I observed for the

Barred Forest-Falcon (M. ruficollis) (Thorstrom et al. 2000a, Auk 117:781-786) and Collared Forest-Falcon (M. semitorquatus) (Thorstrom et al. 2000b, Ornithol. Neotrop. 11:1-12) in northern Central America, from 1988-96. These differences are profound enough to suggest that the raptor species was possibly misidentified as a forest-falcon, or that the Slaty-backed Forest-Falcon displays some rather uncommon behavior within the genus of Micrastur. De Vries and Melo (2000) reported on 14 September, and again on 23 October 1997, that the nesting forest- falcons had a changeover, implying an incubation and a brooding switch, respectively. I never recorded an incubation or brooding switch during 8 breeding seasons of nest observations of Barred {N = 70 nesting attempts) and Collared Forest-Falcons {N = 9 nesting attempts). For these two forest-falcons, the males’ role was providing food to the incubating and brooding female and nestlings. During incubation, the male contact-called to the female upon his arrival to the nest vicinity with prey, and the female exited the nest to receive the prey item where she ate it. On rare occasions, the male entered the cavity while the female ate. The male stayed inside for several minutes either incubating, attempting to incubate or to look at the nest contents, and then he exited the cavity prior to the female’s return (Thorstrom 1993, M.S. thesis, Boise State University, Boise, ID U.S.A., Thorstrom et al. 2000a, Thorstrom et al. 2000b). De Vries and Melo (2000) suspected also that the female fed herself away from the nest and returned to take over incubation or brooding from the male. This does not agree with my observations (Thorstrom et al. 2000a, Thorstrom et al. 2000b) and those of Baker et al. (2000, Ornithol. Neotrop. 11:81-82). Only on very rare occasions did the female leave the nest during incubation to feed herself when the male was late with a prey delivery and hunger brought her off the nest (Thorstrom 1993). De Vries and Melo (2000) describe an open nest constructed of small sticks and deep enough to hide the head of the incubating Slaty-backed Forest-Falcon. In contrast, all described nests for the genus Micrastur have been m cavities (Mader 1979, Condor 81:320) and all nesting attempts by both Barred Forest-Falcons and Collared Forest-

Falcons observed by my colleagues and me in Central America were in tree cavities (Thorstrom et al. 1990, Condor

90:237—239, Thorstrom et al. 2000a, Thorstrom et al. 2000b) except the observation by Baker et al. (2000) of a pair of M. ruficollis nesting in a cliff pothole below canopy level. There is also a record of a Collared Forest-Falcon nesting in a ruined building (Cobb 1990, cited by Howell and Webb 1995, The birds of Mexico and Central America, Oxford

Univ. Press, New York, NYU.S.A.). There is one mention of stick nesting by the Lined Forest-Falcon (M. gilvicollis) in del Hoyo et al. (1994, Handbook of the birds of the world, Lynx Edicions, Barcelona, Spain), but no details were provided. Forest-falcons do appear to have some flexibility in their choice of nest sites, but they seem to prefer a site that simulates a cavity; i.e., trees or cliff potholes surrounded by forests.

The Slaty-backed Forest-Falcon has several described calls: one is a 10-14 nasal aah syllables and another a two part series '‘ah, ow, ow, ow, ow, ow, ow, uah, uah, uah, uah, uaK' (Ridgely and Gwynne 1989, A guide to the birds of Panama, Princeton Univ, Press, Princeton, NJ U.S.A.), a chanting series 8-13 nasal, thus contrasting with the 6 calls “kui kui kui kui kui kui' reported by de Vries and Melo (2000). The authors’ example of the Monk Parakeet {Myiopsitta monachus), a cavity nester that builds a stick nest, does not support their suggestion that the Slaty-backed Forest-Falcon is normally a stick nest builder. Also, their basis for suspecting the forest-falcons built the nest is somewhat vague, i.e., “We did not see the nest being built so we did not know if the falcons had taken an old nest made by another species, but we felt that this was unlikely because we did not see the nest on our regular censuses” (de Vries and Melo 2000). In Central America, forest-falcons were never observed constructing nests out of sticks or carrying nesting material (Thorstrom et al. 2000a, Thorstrom et al. 2000b). However, it is quite possible that forest-falcons can occupy a previously-built nest in a situation that replicates a cavity. There are six known species of Micrastur, and the Lined Forest-Falcon may represent two separate species (A. Whittaker pers. comm.), which would make seven. Among these, two (M. ruficollis, M. semitorquatus) are

335 336 Letters VoL. 36, No. 4

known cavity nesters, three (M. plumbeus, M. gilvicollis, and the proposed new species) are suspected cavity nesters, and for one nesting details are unknown (M. huxkl£yi). Thus, the report by de Vries and Melo (2000), stating that M mirandollei is a stick builder and nester, contrasts sharply with the large body of evidence from its congeners. De Vries and Melo (2000) seemed uncertain about their identification of the species they were observing on the nest. They came to the conclusion that the birds they had observed were not Gray-bellied Goshawks {Accipiter polio- gastei) because of the white belly and yellow facial area of the supposed female, and the other bird, the supposed male, had buff below with both birds having long legs and three narrow, dirty white tail bands (de Vries and Melo

2000). I suggest that the characteristics that de Vries and Melo used to identify this nesting pair of raptors were not conclusive and that they have misidentified this species. The Grey-bellied Goshawk has dark back and crown, long yellow legs, white to gray belly and female larger than male (del Hoyo et al. 1994). Accipiters have long legs, faint tail bands, and females are larger than males. The size dimorphism was commented on by the authors “the first falcon was smaller and probably the male of the pair.” Sexual size dimorphism of forest-falcons was very difficult to distinguish in the field (pers. observ.) because they are only slightly to moderately dimorphic (Thorstrom 1993). Size dimorphism is also a characteristic described for the Grey-bellied Goshawk and Bicolored Hawk {Accipiter bicolor) (del Hoyo et al, 1994). The authors did not give any further detailed characteristics of the color of the legs, back, eyes, and crown of the nesting raptors. The nesting behavior and habitat, vocalization, and plumage characteristics suggest lhat the nesting birds described by de Vries and Melo (2000) were possibly accipiters, either the Crrey-bellied Goshawk or Bicolored Hawk.

I thank The Peregrine Fund for support and L. Kiff, R. Bierregaard, J. Bednarz, and one anonymous reviewer for their comments on this manuscript.—Russell Thorstrom, The Peregrine Fund, 5668 West Flying Hawk Lane, Boise, ID 83709 U.S.A.; E-mail address: [email protected]

Received 21 August 2001; accepted 19 June 2002 —

Micrastur or Accipiter, That is the Question

. . the more you look the more you see” (Peter Grant 1986, Ecology and evolution of Darwin’s finches. Princeton Univ. Press, Princeton, NJ U.S.A.).

The main point made by Thorstrorn (2002, J. Raptor Res. 36:335-336) concerns the behavior of our birds, which he claims is not the behavior of Micrastur (he should perhaps say the behavior of M. ruficollis and M. semilorquatus,

as the behavior of the other four species is still unknown) . We can report that the Slaty-backed Forest-Falcon {Micrastur mirandolld) was present in the area of its now defunct 1997 stick nest (de Vries and Melo 2000,/ Raptor Res. 34:148-

150) in March of 1998. Although we cannot be sure that it is the same bird we saw previously at and around the nest, it responded (vocalized, but did not come out into the open) to the species’ call as recorded by John Mooie m his series of bird sounds of eastern Ecuador. So far, we have been unable to locate its new nesting site. The Grey-bellied Goshawk {Accipiter poliogaster) was present at some 5 km distance from the MicrasturncA site in both 1997 and 1998. We observed this species in the more open and bare branches of the canopy, rather than the densely-vegetated, middle canopy layer, where we noted Micrastur mirandollei. We hope that the comment by R. Thorstrorn (2002) stimulates more observations on Micrastur, which are badly needed. In addition, further study on why some avian raptors are so similar in plumage patterns, as is the case with M. mirandollei and Accipiter poliogastca; would be valuable in understanding the potential adaptive benefits of such

“mimicry.” In our field experience, the “capped” appearance and tail banding oi Accipiter 'Are diagnostic, as are the round grey head and yellow face that Micrastur features. Tjitte de Vries and Cristian Melo, Departamento de Biol- ogia, Pontificia Universidad Catolica del Ecuador, Apartado 17-01-2184, Quito, Ecuador; E-mail address: tdevries@ puceuio.puce.edu.ee

Received 8 November 2001; accepted 27 June 2002

337 —

BOOK REVIEWS

J Raptor Rf,s. 36(4) :338 content. The late David Peakall’s contribution re- Inc. © 2002 The Raptor Research Foundation, garding poisonings in free-living raptors is an in- clusive general overview of chemical toxicity on a worldwide scale. Birds of Prey; Health 8c Disease. By John E. This is an intensely personal work. Cooper states Cooper. 2002. 3rd edition. Blackwell, Oxford, emphatically that he has laced the writing with U.K. xvii + 345 pp., 13 tables, 56 figures, 28 color opinions, personal experiences, and other subjec- plates, 11 appendices. ISBN 0-632-05115-9. Hard- tive matter. One of the most difficult challenges in back, £59.50.—The study of raptors is unquestion- reviewing this work is to assign it to a category for ably enhanced by the diversity of perspectives from the reader. The book is not a clinical manual, nor which it derives, i.e., from biologists, falconers, a biology text, nor a handbook for falconers. It medical practitioners, and others. Each of these does, however, contain elements of each along with disciplines provides data and references that ad- personal reflections on the experiences and opin- dress birds of prey in unique and relevant terms. ions of the principal author. Although resisting In updating his earlier pioneering work, Vetmnary classification. Birds of Prey: Health & Disease fills a Aspects of Captive Birds of Prey, now entitled Birds of useful and interesting niche in raptor literature for Prey: Health & Disease, John Cooper continues his all those involved in the field. James D. Elliott, intentionally eclectic collection of information and South Carolina Center for Birds of Prey, P.O. Box points-of-view. The new work is organized identi- 1247, Charleston, SC 29402 U.S.A. cally to the former but for the addition of three new chapters from contributing authors. Roughly one-third of the information in the new book is repeated verbatim from the earlier one, one-third includes previous information updated by a brief summary of advancements and a list of references for further study, and the remainder is an expan- sion that reflects work that has appeared since the J. Raptor Res. 36(4):338-339 earlier volume. © 2002 The Raptor Research Foundation, Inc. Cooper has long advocated collaboration among all who deal with birds of prey, which is borne out by his approach to the new addition. Cooper is at Owls. By Floyd Scholz. 2001. Stackpole Books, once observer, historian, and medical practitioner Mechanicsburg, PA. xiii + 379 pp., more than 700 in discussing the various topics. He makes no at- color photographs. ISBN 0-8117-102T1. Cloth, tempt to cover the subjects in depth, but rather $80.00.—In 1993, Floyd Scholz published Birds of provides context and references for the reader’s Prey, which was a collection of detailed color pho- use. The diverse array of topics, and the somewhat tographs of 17 species of North American falconi- lack of in-depth coverage, may serve as a disap- forms (see /. Raptor Res. 28:278—279, 1994). Team- pointment to some but will be acceptable to others ing up once more with photographer Tad Merrick, as an interesting and general guide. The value of Scholz has expanded his domain to include the the book will certainly be defined by the expecta- strigiforms. The result is an extensive series of col- tions of those who use it. or photographs of 17 of the 19 species of owls The contributed chapters vary considerably in (Western Screech-Owl \_Otus kennicottii] and Whis- scope and detail. Paolo Zucca’s chapter on anato- kered Screech-Owl [O. trichopsis] omitted) that my is generalized with varying degrees of detail. breed in the United States and Canada.

Once again, subjectivity is a factor in some conclu- Floyd Scholz is an extraordinary carver and sions. Ian Newton’s discussion of parasitic diseases painter of birds, and the main purpose of Owls is

IS, by nature, broad, yet is thorough and sound in to serve as a reference guide for artists. An intro-

338 , —

December 2002 Book Reviews 339

ductory chapter, “What is an Owl?” presents infor- mentioning. First, the Great Horned Owl {Bubo vir- mation on the various morphological adaptations ginianus) shown in many of the photos can be of owls; the treatment enhances the text and is ba- readily described by two words: pissed off. Tm not sically the same as that found in any coffee table sure why an artist would need photos of an owl in book or general ornithology text that deals with this state, nor why someone would continue to owls. The species accounts make up the heart of bother a bird that so obviously detested whatever the book. Each includes a page of information on treatment it was receiving. In fairness to the author morphology and behavior of the species in ques- and photographer, this same attitude is displayed tion, details on the size of various body parts (in- by a wild female Great Horned Owl depicted on cluding line drawings of the species from the back the cover of the Birds of North America species ac- and side), and numerous color photographs (typ- count. Second, I was surprised that none of the 32 ically 30-40 per species). The photos are taken photos of the two species of pygmy-owls contained from nearly every conceivable angle to provide de- a decent view of the so-called “false eyes” on the tails on plumage, talons, ear tufts, facial ruffs, eyes, back of the head. This is a minor quibble to be bills, nostrils, and napes, to name but a sample of sure, but an opportunity missed nonetheless. the features depicted. These photos contain fine The last two chapters are entitled “Techniques points that would seldom be noticed without hav- for the Artist and Garver” and “Gallery,” the latter ing a bird in the hand and thus will serve as a consisting of a collection of photos of some of the valuable reference for people who do not have ac- owls Mr. Scholz has carved and painted. The carv- cess to museum specimens. Most of the photos are ings are absolutely gorgeous and point to the enor- of captive birds, the exceptions being a handful of mous talent of the author. This book will appeal to very nice shots of wild Northern Hawk Owls (Sur- anyone with an interest in owls, although the price nia ulula) Great Gray Owls {Strix nebulosa), and may place it out of reach of all but the confirmed Boreal Owls {Aegolius funereus) by Ron Austing and “owlaholics,” to borrow a phrase coined by Heimo Robert Taylor. Mikkola. Jeff Marks, Montana Cooperative Wild- The photo selection, and the photos themselves, life Research Unit, University of Montana, Missou- are truly excellent, but two criticisms are worth la, MT 59812 U.S.A. .

Journal of Raptor Research INFORMATION FOR CONTRIBUTORS

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340 December 2002 Information for Contributors 341

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I. General Instructions Use “continental” dating (e.g., lOJuly 1993, l-3June, 11 May to (Consult recent issues for additional guidance on format) 11 June). Use 24-hour clock (e.g., 0800 H, 1345-1400 H) Write out numbers one to nine unless a measurement I I Type manuscripts on one side of either 216 X 278 (e.g., four birds, 3 km, 40 sites, yr). Use 1000 and mm (8.5 X IT') or standard international size (210 6 X 297 mm) good quality paper (do not use erasable 10 000; 0.15 instead of .15; % instead of percent. or lightweight paper). Word-processor-generated Each reference cited in text must be listed in the Lit- erature section, vice versa. manuscripts must be done with a letter-quality or near- Cited and Double check the accuracy of all entries- letter-quality printer. DOUBLE SPACE THROUGH- —THE EDITORIAI. STAFF CANNOT THIS FOR YOU. OUT including title, text, tables, hgure legends, and DO Literature citations in text as follows; literature cited. the are Optional electronic submission. Submit e-mail mes- a. One author-Jones (1993) or (Jones 1993) b. Two authors-Smith and Jones (1991) or (Smith sage with two attached file copies of manuscript: 1) and Jones 1991) pdf hie (must include hgures) and 2) word processing c. Three or authors-Hernandez et al. hie (Word Perfect [preferred] or MS Word hies ac- more (1990) or cepted). Follow same format guidelines as for stan- (Hernandez et al. 1990) dard mail submission. Letter of transmittal should be d. Manuscripts accepted for publication but not yet published-Howard (in press) or (Howard in press) included in the e-mail message. E-mail to; jrr@astate. edu e. Unpublished materials-K. Jacobson (unpubl. data); pers. or K. Give the scientihc name at the hrst mention of a spe- (K. Jacobson comm.); Jacobson (pers. comm.) -do not place in the Literature Cited cies, both in the abstract and in the article. Scientihc names of birds should follow the usage of the AOU section. f. When citing several references within parentheses, Check-list of North American Birds (7th. ed. 1998 and subsequent supplements in the Auk) or an authorita- separate with commas and put in chronological order, olde.st hrst). tive source corresponding to other geographic re- g. For manuscripts submitted as letters, place cita- gions. Do not give subspecihc identihcation unless it tions in text in abbreviated form, e.g., (I.C. Birds is pertinent. Capitalize hrst letter of words in com- Raptor Res. 27:45-50). plete common names for birds. Use lower case for all 1993, J. other common names. Assemble manuscripts for regular articles in this order: title page, abstract page, text, ta- D Use American spelling and Webster’s Tenth New Colle- (1) (2) (3) (4) bles, hgure legends, hgures. STA- giate Dictionary (1996, Merriam-Webster, Inc.) as a (5) (6) DO NOT spelling authority. PLE. Leave at least a 25 mm (1") margin on all sides. Avoid II. Title Page hyphens or dashes at ends of lines; do not divide a word at the end of a line. Place full title 6-8 lines below top of page in all Use a nonproportional font of at least elite size (4.7 capital letters. Below title, center author’s characters/cm = 12 characters/inch) or 12 point, name(s) in all capital letters and address (es) preferably Courier. DO NOT USE RIGHT JUSTIFI- CATION-LEAVE RIGHT MARGIN RAGGED. followed by a running title (short title) not to D Use italic type for addresses, scientihc names, journal exceed 30 characters. If the author(s) is/are names, and third level headings. currently at another location from where the last (s) number in Type name(s) of author and page work was done, use superscript number (s) fol- upper right-hand corner of page 2 and all following lowing author (s) name(s) to indicate current pages. address in footnote at bottom of the page. In Cite each hgure and table in the text. Do not repeat multiauthored papers, indicate the author re- material in two forms (i.e., in text and table, or table and hgure). Organize text, as far as possible, so that sponsible for correspondence and requests for tables and hgures are cited in numerical order. reprints. Give phone number and, if possible, Use “Figure” only to start a sentence; otherwise FAX number and e-mail address of the corre- “Fig.” if singular, “Figs.” if plural (e.g.. Fig. 1; Figs. 2, sponding author. 3; Figs, d—6). Use metric units throughout. III. Abstract/summary Use these abbreviations without spelling out: hr, min, sec, yr, mo, wk, d, km, cm, mm; designate temperature For regular articles, include an abstract of about as 32°C. 250 words in one paragraph that is completely 342 Information for Contributors VoL. 36, No. 4

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December 2002 Information for Contributors 343

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Index to Volume 36

By Kristina Baker

This index includes references to general, species, common names, key words, and authors. Reference is also made to book reviews, letters, and reviewers. Taxa other than raptors are included where referenced by authors.

A B

Abuladze, Alexander and Jevgeni Shergalin, The Golden Baghino, Luca, see Agostini, Nicolantonio

Eagle in north Caucasia and Transcaucasia, 10-17 Bainbridge, Ian R, see McGrady, Michael J. (suppl.) Baja California Peninsula, 3-9 (suppl.) Afdpiler, 229-230 Baker, Aaron, see Thorstrom, Russell (ooperii 229-230 Balbontin, Javier and Miguel Ferrer, Plasma chemistry

gentilis, 141-143, 229-230, 265-279 reference values in free-living Bonelli’s Eagle {Hi-

sLriaius, 229-230 eraaetus fasciatus) nestlings, 231-235

Aegolius funereus, 2 1 8—2 1 Bald and Golden Eagle Protection Act, 29-31 (suppl.) Age differences, 115-120 Band, encounters, 97-110 Agostini, Nicolantonio, Luca Baghino, Charles Coleiro, recoveries, 97-110 Ferdinando Corbi, and Guido Premuda, Circuitoxis Barry, Irene M., see Powell, Larkin A. Barton, Nigel W.H., Nicholas C. F. autumn migration in the Short-toed Eagle { Circaetus Fox, Peter Surai, and gallicus), 111-114 Brian K. Speake, Vitamins E and A, carotenoids, and Alaska, 50-54 (suppl.) fatty acids of the raptor egg yolk, 33-38 Albinism, 200-202 Bates, John M., see Grifliths, Carole S. Alloparental care, 70-73 Bats, 146-148 Ammer, Frank K. and Petra Bohall Wood, Probable Beasom, Sam. L, see Proudfoot, Glenn A. breeding of Short-eared Owls in southern West Vir- Bechard, MareJ. and Michael J. McGrady, Status and con- ginia, 237-238 servation of Golden Eagles, 2 (suppl.) Bednarz, 1-2 Andersen, David E., see Warnke, D. Keith James C., Working toward excellence, Behavior, 77-81, 136-139 Anderson, David L., see Thorstrom, Russell 121-127, copulation, 66-70 Angulo, Elena, Factors influencing length of the pc^st- hunting, 194-199 fledging period and timing of dispersal in Bonelli’s ranging, 70-77 (suppl.) Eagle {Hieraaetus fasciatus) in southwestern Spain, Beheim, 157 Janne, Katrine Eldegard, Gro Bj0rnstad, Mats Isaksson, Geir Sonerud, Olav Heie, and Helge Anthropogenic food sources, 220-224 Klungland, DNA polymorphisms in Boreal Owls {Ae- Aparicio, Jose, see Cordero, Pedro J. golius funereus 2 1 8—2 1 Apodaca, Christine K., see Seavy, Nathaniel E. ) , Bellocq, M. Isabel, Patricio Ranhrez-Llorens, andjulieta Aquila dirysaetos, 3-9 (suppl.), 10-17 (suppl.), 18-19 Filloy, Recent records of Crowned Eagles {Harpyhal- (suppl.), 20-24 (suppl.), 25-28 (suppl.), 29-31 iaetus coronalus) from Argentina, 1981-2000, 206- (suppl.), 32-40 (suppl.), 41-49 (suppl.), 50-54 212 (suppl.), 55-61 (suppl.), 62-69 (suppl.), 70-77 Berkelman, James, James D. Fraser, and Richard T. Wat- (suppl.) son, Nesting and yjerching habitat use of the Mada- xvahlbergi, 51—57 gascar Fish-Eagle, 287-293 Argentina, 206-212, 315-319 Bertram, Joan and Antoni Margalida, Social organization Asia otus, 73-77 of a trio ol Bearded Vultures {Gypaetus barbatus): sex- Athene cunicularia Jloridana, 3-10 ual and parental roles, 66-70 Avila, Gregorio Lopez, see Whitacre, David F. Bianchi, Edward W., see Hunt, W. Grainger Avila, Juventino Lopez, see Whitacre, David F. Bias, 11-16 Avery, Michael L., John S. ITiimphrey, Eric A. Tillman, Bildstein, Keith 1.., sec Yosef, Reuven Kimberly O. Phares, and Jane E. Hatcher, Dispersing Bj 0rnstad, Gro, see see Beheim, Janne 45-50 vulture roosts on communication towers, Blood, 231-235 Ayers, Serena, see Thorstrom, Russell parasites, 139-141

Bloxton, Thomas D., Audi Rogers, Michael F. Ingraldi,

344 December 2002 Index to Volume 36 345

Steve Rosenstock, John M. Marzluff, and Sean R Columbretes Islands, 139-141 Finn, Possible choking mortalities of adult Northern Common Buzzard, 24—32, 115-120, 128-135, 188-193 Goshawks, 141-143 Communication tower, 45-50 Boano, Giovanni and Roberto Toffoli, A line transect sur- Conservation, 10-17 (suppl.), 20-24 (suppl.), 29-31 vey of wintering raptors in the western Po Plain of (suppl.), 41-49 (suppl.), 51-57, 206-212

northern Italy, 128-135 Constraints, 41-49 (suppl.) Bogliani, Giuseppe, see Sergio, Fabrizio Control region, 17-23 Bolivia, 146-148 Cooke, Raylene, Robert Wallis, and John White, Use of Boto, Alberto, see Sergio, Fabrizio vegetative structure by Powerful Owls in outer urban Brazil, 328-331, 332-334 Melbourne, Victoria, Australia—implications for Breeding, 161-169 management, 294-299 diet, 332-334 Coragyps atratus, 45-50 season, 194-199 Corbi, Charles, see Agostini, Nicolantonio

success, 24-32, 81-84, 224-228 Cordero, Pedro J., Jose M. Aparicio, and David T. Parkin, Brendel, Ulrich M., Rolf Eberhardt, and Karen Wies- Genetic evidence of alloparental care of a female mann, Conservation of the Golden Eagle (Aquila Lesser Kestrel in an alien nest, 70-73 chrysaetos) in the European Alps—a combination of Coulson, Jennifer O., Mississippi Kites use Swallow-tailed education, cooperation, and modern techniques, Kite nests, 155—156 20-24 (suppl.) Crested Caracara, 203-206 Bubo bubo, 11-16 Cromrich, Lee A., Denver W. Holt, and Shawne M. Lea- virginianus, 58—65 sure, Trophic niche of North American Great Buhay, Jennifer E. and Gary Ritchison, Hunting behavior Horned Owls, 58-65 of and space use by Eastern-Screech Owls during the Culver, Melanie, see Tingay, Ruth E. breeding season, 194—199 Cumulative impacts, 55-61 (suppl.)

Buteo buteo, 24-32, 115-120, 128-135, 188-193 Cytochrome b, 183-187 lineatus, 152-153 D C Dams, 245-255

Calvert, Dan J., see Powell, Larkin A, de Vries, Tjitte and Cristian Melo, Micrastur or Accipiter, Canada, 32-40 (suppl.) that is the question, 337 Canary Islands, 17-23 Deforestation, 51-57 Cannibalism, 200-202 Degraaf, Richard M., see Smith, Harvey R. Capote, Nieves, see Donazar, Jose Antonio Demography, 3-10 Capture, 188-193 Denali National Park, 50-54 (suppl.) techniques, 320-323 Density, 24—32 Caracara cheriway, 203—206 Development, 3-10, 77-81 Carpathian Mountains, 25—28 (suppl.) Dho-gaza, 320-323 Carrion, 152-153 Diet, 24-32, 58-65, 148-152, 328-331 Caryospora hutzeri, 84—86 assessment methods, 11-16 Cathartes aura, 45-50, 144—145 Dispersal, 176-182, 309-314 burrovianus, 183-187 natal, 203—206 melambrotus, 183-187 roost, 45-50 Caucasia, 10-17 (suppl.) Distribution, 10-17 (suppl.) Ceballos, Olga, see Donazar, Jose Antonio Disturbance, 294—299 Central America, 39-44 DNA, fingerprinting, 280-286 Chavez-Ramirez, Felipe, see Proudfoot, Glenn A. mitochondrial, 17—23 Chihuahua, 3-9 (suppl.) multilocus fingerprinting, 70-73 Chile, 315-319 polymorphisms, 218-219 Choking, 141-143 Donazar, Jose Antonio, Juan Jose Negro, Cesar Javier Pa- Circaetus gallicus, 111-114 lacios, Laura Gangoso,Jose Antonio Godoy, Olga Ce- Cliffs, 39-44 ballos, Fernando Hiraldo, and Nieves Capote, De- Coahuila, 3-9 (suppl.) scription of a new subspecies of the Egyptian Vulture Coccidiosis, 84—86 (Accipitridae: Neophron percnopterus) from the Canary Coleiro, Charles, see Agostini, Nicolantonio Islands, 17-23 Colonization, 18-19 (suppl.) Driscoll, Daniel E., see Hunt, W. Grainger Colorado, 256-264 Durango, 3-9 (suppl.) 346 Index to Volume 36 VoL. 36, No. 4

Dykstra, Cheryl R., Michael W. Meyer, and D. Keith Warn- Peregrine, 176-182, 200-202, 213-217, 315-319 ke, Bald Eagle reproductive performance following Fatty acids, 33-38 video camera placement, 136-139 Feeding, 144-145, 152-153 Dykstra, Cheryl R., see Warnke, D. Keith habits, 224-228 Ferrer, Miguel, see Balbontin, Javier E Filloy, Julieta, see Bellocq, M. Isabel Finn, Sean R, Daniel E. Varland, and John M. Marzluff, Eagle, Bald, 29-31 (suppL), 121-127, 136-139, 161-169, Does Northern Goshawk breeding occupancy vary 245-255, 256-264, 324-327 with nest-stand characteristics on the Olympic Pen- Bonelli’s, 231-235 insula, Washington?, 265-279 Crested, 77-81 Finn, Sean R, see Bloxton, Thomas D. Crowned, 206-212 Firmanszky, Gabor, The status of the Golden Eagle {Aq- Crowned Hawk-, 300—308 uila chrysaetos) in Hungary, 18-19 (suppl.) Golden, 3-9 (suppL), 10-17 (suppL), 18-19 (suppl.), Flake, Lester D., see Fahler, Natalie A. 20-24 (suppl.), 25-28 (suppl.), 29-31 (suppl.), Flocking, 111-114 32-40 (suppl.), 41-49 (suppl.), 50-54 (suppl.), Florida, 3-10, 203-206 55-61 (suppl.), 62-69 (suppl.), 70-77 (suppl.) Flyways, 97-110 Long-crested, 51-57 Food, 144-145 Madagascar Fish-, 280-286, 287-293, 309-314 -niche breadth, 58-65 Short-toed, 111-114 Foraging habitat, 220-224 Wahlberg’s, 51-57 Forestry, 24—32 White-tailed Sea, 220-224 Fox, Nicholas C., see Barton, Nigel W.H. Eberhart, Rolf, see Brendel, Ulrich M. Fractures, 229-230 Effigy, 45-50 Framework, 41—49 (suppl.) Eggs, 324-327 Fraser, James D., see Berkelman, James yolk, 33-38 Fraser, James D., see Tingay, Ruth E. Eggshell characteristics, 324-327 French, Thomas W., see Roth, Aaron J. Elat, 115-120 Eldegard, Katrine, see Beheim, Janne G Elliot, James D., A review of Birds of Prey: Health & Dis- ease, by John E. Cooper, 2002, 338 Gangoso, Laura and Cesar J. Palacios, Endangered Egyp- Elhs, David H., Beth Ann Sabo, James K. Fackler, and tian Vulture {Neophron percnopterus) entangled in a Brian A. Millsap, Prey of the Peregrine Falcon {Falco power line ground-wire stabilizer, 238-239 peregtinus cassini) in southern Argentina and Chile, Gangoso, Laura, see Donazar, Jose Antonio 315-319 Genetics, 183-187 Ellis, David H., Lynn W. Oliphant, and James K. Fackler, Gladdium brasilianum, 170-175 Schizochromism in a Peregrine Falcon from Arizo- Godoy, Jose Antonio, see Donazar, Jose Antonio na, 200-202 Grant, Justin R., see McGrady, Michael J. Emergent trees, 300-308 Great Lakes, 136-139 Englund, Judy Voigt, see Martell, Mark S. Griffiths, Carole S. and John M. Bates, Morphology, ge- Environmental education, 20-24 (suppl.) netics and the value of voucher specimens: an ex- European Alps, 20-24 (suppl.) ample with Cathartes vultures, 183-187 Gypaetus barbatus, 66-70 F

Fackler, James K., see Ellis, David H., 200-202 H Fackler, James K., see Ellis, David H., 315-319 Fahler, Natalie A. and Lester D. Flake, Nesting of Long- Habitat, 287-293 eared Owls along the lower Big Lost River, Idaho: a management, 55-61 (suppl.) comparison of 1975-76 and 1996-97, 73-77 preferences, 224-228 Falco deiroleucus, 39-44 quality models, 20-24 (suppl.) eleonorae, 139-141 selection, 245-255 naumanni, 70-73, 148-152 use, 51-57 peregtinus, 176-182, 200-202, 203-217, 315-319 Haliaeetus albicilla, 220-224 tinnunculus, 81—84, 84-86 leucocephalus, 29-31 (suppl.), 121-127, 136-139, 161- Falcon, Eleonora’s, 139-141 169, 245-255, 256-264, 324-327 Orange-breasted, 39-44 vociferoides, 280-286, 287-293, 309-314 Pallid, 315-319 Hallerman, Eric M., see Tingay, Ruth E. ,

December 2002 Index to Volume 36 347

Harmata, Alan R., Vernal migration of Bald Eagles from manni) in its winter quarters in South Africa, 148- a southern Colorado wintering area, 256-264 152 Harpyhaliaetus coronatus, 206-212 Krone, Oliver, Fatal Caryospora infection in a free-living Hatcher, Jane E., see Avery, Michael L. Juvenile Eurasian Kestrel {Falco tinnunculus) 84—86 Hawk, Cooper’s, 229-230 Red-shouldered, 152-153 L Sharp-shinned, 229-230 Heie, Olav, see see Beheim, Janne land use, 55-61 (suppl.) Hieraaetus fasciatus, 231-235 Landaeta, Carlos A., see Vargas, Julieta Hiraldo, Fernando, see Donazar, Jose Antonio Leasure, Shawne M., see Cromrich, Lee A. Hoffman, Stephen W., Jeff R Smith, and Timothy D. Leucism, 200-202 Meehan, Breeding grounds, winter ranges, and mi- Linda, Lomo, see Nunnery, Tony gratory routes of raptors in the mountain west, 97- Logistic regression, 265-279 110 Londei, Tiziano, The Fox Kestrel {Falco alopex) hovers, Hokkaido, Japan, 220-224 236-237 Holt, Denver W., see Cromrich, Lee A. Lophaetus occipitalis, 51-57 Home range, 70-77 (suppL), 245-255 Homosexual matings, 66-70 M Humphrey, John S., see Avery, Michael L. Hungary, 18-19 (suppl.) Madagascar, 287-293 Hunt, W. Grainger, Ronald E. Jackman, Daniel E. Dris- Madders, Mike and Dave Walker, Golden Eagles in a mul- coll, and Edward W. Bianchi, Foraging ecology of tiple land-use environment: a case study in conflict nesting Bald Eagles in Arizona, 245-255 management, 55-61 (suppl.) Malan, Gerard and Susanne Shultz, Nest-site selection of I the Crowned Hawk-Eagle in the forests of Kwazulu- Natal, South Africa, and Tai, Ivory Coast, 300-308 Idaho, 73-77 Management, 20-24 (suppl.), 294—299 Immobilization, 188-193 Manganaro, Alberto, see Salvati, Luca Ingraldi, Michael R, see Bloxton, Thomas D. Mangrove, 328-331 Injuries, 229-230 Marches!, Luigi, Paolo Pedrini, and Fabrizio Sergio, Bi- Isaksson, Mats, see Beheim, Janne ases associated with diet study methods in the Eur- Italy, 11-16, 24-32, 128-135 asian Eagle Owl, 11-16 Margalida, Antoni, see Bertran, Joan J Mark-recapture, 3-10 Jackman, Ronald E., see Hunt, W. Grainger model, 176-182

Jacobs, Eugene A. and Glenn A. Proudfoot, An elevated Marks, Jeff, A review of Owls, by Floyd Scholz, 2001, 338- net assembly to capture nesting raptors, 320-323 339

Janovsky, Martin, Thomas Ruf, and Wolfgang Zenker, Martell, Mark S., Judy Voigt Englund, and Harrison B. Oral administration of tiletamine/zolazepam for the Tordoff, An urban Osprey population established by immobilization of the Common Buzzard {Buteo bu- translocation, 91—96 teo), 188-193 Martinez-Abrain, Alejandro and Gerardo Urios, Absence Jenkins, M. Alan, Steve K. Sherrod, David A. Wiedenfeld, of blood parasites in nestlings of the Eleonora’s Fal- and Donald H. Wolfe, Jr., Florida Bald Eagle {Hal- con {Falco eleonorae), 139-141 iaeetus leucocephalus) egg characteristics, 324-327 Marzluff, John M., a review of The Spanish Imperial Ea- Jones, Gwilym S., see Roth, Aaron J. gle, by Miguel Ferrer, 2001, 242-244 Marzluff, John M., see Bloxton, Thomas D. K Marzluff, John M., see Finn, Sean P. Karasov, William H., see Warnke, D. Keith Mating system, 280-286 Kery, Marc, New observations of the Peregrine Falcon Mays, Jody L., see Proudfoot, Glenn A. {Falco peregrinus) in Peru, 213-217 McAllister, Kelly R., see Watson, James W. P. Kestrel, Eurasian, 81-84, 84-86 McGrady, Michael J., Justin R. Grant, Ian Bainbridge, Lesser, 70-73, 148-152 and David R.A. McLeod, A model of Golden Eagle

Klungland, Helge, see see Beheim, Janne {Aquila chrysaetos) ranging behavior, 62-69 (suppl )

Kochert, Michael N. and Karen Steenhof, Golden Eagles McGrady, Michael J., see Bechard, MarcJ.

in the G.S. and Canada: status, trends, and conser- McGrady, Michael J., see McLeod, David R.A vation challenges, 32-40 (suppl.) McIntyre, Carol L., Patterns in nesting area occupancy Kopij, Grzegorz, Food of the l,esser Kestrel {Falco nau- and reproductive success of Golden Eagles {Aquila 348 Index to Volume 36 VOL. 36, No. 4

chrysaetos) in Denali National Park and Preserve, North America, 58-65, 229-230 Alaska, 1988-99, 50-54 (suppl.) western, 97-110

McLeod, David R.A., D. Philip Whitfield, and Michael J. Northern Goshawk, 141-143, 229-230, 265-279 McGrady, Improving prediction of Golden Eagle Nunnery, Tony, Lomo Linda, and Mark R. Welford,

{Aquila chrysaetos) ranging in western Scotland using Barred Forest-Falcon {Micrastur ruficollis) predation GIS and terrain modeling, 70-77 (suppl.) on a hummingbird, 239-240

McI.eod, David R.A., see McGrady, Michael J. Mediterranean areas, 81-84 O Meehan, Timothy D., see Hoffman, Stephen W. Melo, Cristian, see de Vries, Tjitte Olfaction, 144-145 Mexico, 3-9 (suppl.) Oliphant, Lynn W., see Ellis, David H. Meyer, Michael W., see Dykstra, Cheryl R. Olmos, Fabio, see Silva e Silva, Robson Meyer, Michael W., see Warnke, D. Keith Oral administration, 188-193 Microsatellite, 218-219 Orientation, 111-114 Migration, 97-110, 111-114 Osprey, 91-96, 328-331 differential, 97-110 Otus asio, 194-199 spring, 115-120 choliba, 332-334 vernal, 256-264 Overstory depth, 265-279 Millar, Jody Gustitus, The protection of eagles and the Owens, Thomas E., see Watson, James W. Bald and Golden Eagle Protection Act, 29-31 Owl, Barn, 146-148, 224-228 (suppl.) Boreal, 218-219

Miller, Richard S., see Smith, Harvey R. Burrowing, 3-10

Millsap, Brian A., see Ellis, David H. Eastern Screech-, 194-199 Millsap, Brian A., Survival of Florida Burrowing Owls Eurasian Eagle-, 11-16 along an urban-development gradient, 3-10 Ferriginous Pygmy-, 170-175 Minnesota, 91-96 Great Horned, 58-65 Mizera, Tadeusz, see Waclawek, Krzysztof Long-eared, 73-77 Monitoring, 32-40 (suppl.) Mechanical, 320—323 Morphnus guianensis, 77-81 Powerful, 294-299 Morrison, Joan L., see Nemeth, Nicole M. Tengmalm’s, 218-219 Mortality, 32-40 (suppl.), 141-143 Tropical Screech-, 332-334 Mottajunior, Jose Carlos, Diet of breeding Tropical Screech-Owls (Otus choliba) in southeastern Brazil, P 332-334 Movements, 62-69 (suppl.) Palacios, Cesar Javier, see Donazar, Jose Antonio

Palacios, Cesar J., see Gangoso, Laura N Pandion haliaetus, 91-96, 328-331 Parental roles, 66-70

Navigation, 111-114 Parkin, David T, see Cordero, Pedro J. Negro, Juan Jose, see Donazar, Jose Antonio Pedrini, Paolo, see Marches!, Luigi Nemeth, Nicole M. andjoan L. Morrison, Natal dispersal Perch time, 194—199 of the Crested Caracara {Caracara cheriway) in Flori- tree, 287-293 da, 203-206 Peru, 213-217

Neofjhron percnopterus majormsis, 1 7-23 Pesticides, 324-327 Nest, access, 300-308 Phares, Kimberly O., see Avery, Michael L. helper, 280-286 Piscivory, 245-255 tree, 287-293 Plasma, 33-38 Nest-site selection, 300-308 chemistry, 231-235 Nesting, 73-77 Poland, 25-28 (suppl.) biology, 77-81 Polyandry, 280-286 Nestlings, 77-81, 139-141 cooperative, 66-70 free-living, 231-235 Population restoration, 176-182 Net, drop, 320-323 Post-fledging, length, 157 elevated, 320-323 movement, 220-224 mist, 320-323 status, 161-169

New records, 206-212 Powell, Larkin A., Dan J. Calvert, Irene M. Barry, and Ntnox strenua, 294—299 Lowell Washburn, Post-fledging survival and dispers- Dec;ember 2002 Index to Voeume 36 349

al of Peregrine Falcons during a restoration project, Habitat preferences, breeding success, and diet of

176-182 the Barn Owl ( Tyto alba) in Rome: urban versus rural Pranty, Bill, Red-shouldered Hawk feeds on carrion, 152- territories, 224-228 153 Salvati, Luca, Spring weather and breeding success of the Pre-Alps, 24-32 Eurasian Kestrel {Falco tinnunculus) in urban Rome, Premuda, Guido, see Agostini, Nicolantonio Italy, 81-84 Prey, 141-143, 315-319 Saskatchewan, 256-264 biomass, 332-334 Satellite telemetry, 309-314 size, 146-148 Scandolara, Chiara, see Sergio, Fabrizio Productivity, 91-96, 161-169 Scavenging, 144-145 Protozoa, 84-86 Schizochromism, 200-202 Proudfoot, Glenn A., Sam L, Beasom, Felipe Chavez-Ra- Scotland, 62-69 (suppl.) mirez, and Jody L. Mays, Response distance of Fer- Seavy, Nathaniel E. and Christine K. Apodaca, Raptor ruginous Pygmy-Owls to broadcasted conspecific abundance and habitat use in a highly-disturbed- for- calls, 170-175 est landscape in western Uganda, 51-57 Proudfoot, Glenn A., see Jacobs, Eugene A. Sergio, Fabrizio, Alberto Boto, Chiara Scandolara, and

Provisioning, 121-127 Guiseppe Bogliani, Density, nest sites, diet, and productivity of Common Buzzards {Buteo buteo) in the R Italian pre-Alps, 24-32 Sergio, Fabrizio, see Marchesi, Luigi Radio-tracking, 256-264 Sex, 231-235 Radiotelemetry, 245-255 Shergalin, Jevgeni, see Abuladze, Alexander Rafanomezantsoa, Simon, Richard T. Watson, and Russell Sherrod, Steve K., see Jenkins, M. Alan Thorstrom, Juvenile dispersal of Madagascar Fish-Ea- Shiraki, Saiko, Post-fledging movements and foraging gles tracked by satellite telemetry, 309-314 habitats of immature White-tailed Sea Eagles in the Ramirez-Llorens, Patricio, see Bellocq, M. Isabel Nemuro Region, Hokkaido, Japan, 220-224 Ranazzi, Lamberto, see Salvati, Luca Shoreline, 297-293 Range, 62-69 (suppl.) Shrub cover, 265-279 model, 70-77 (suppl.) Shultz, Susanne, see Malan, Gerard use, 194-199 Silva e Silva, Robson, and Fabio Olmos, Osprey ecology Raptor nutrition, 33-38 in the mangroves of southeastern Brazil, 328-331 Raptors, 128-135 Simonetti, Javier A., see Vargas, Julieta Recovery, 161-169 Smith, Harvey R., Richard M. DeGraaf, and Richard S. Repopulation, 25-28 (suppl.) Miller, Exhumation of food by Turkey Vulture, 144- Reproduction, 50-54 (suppl.) 145 Reproductive performance, 136-139 Smith, Jeff R, see Hoffman, Stephen W. Restani, Marco, A review of Raptors of the World, by Solifugae, 148-152 James Ferguson-Lees and David A. Christie, 2001, Sonerud, Geir, see Beheim, Janne 241-242 Sonora, 3-9 (suppl.) Riparian, 73-77 South Africa, 148-152 Ritchison, Gary, see Buhay, Jennifer E. South America, 213-217 Rivers, 245-255 Spain, 66-70 Rodriguez-Estrella, Ricardo, A survey of Golden Eagles in Speake, Brian K., see Barton, Nigel W.H. northern Mexico in 1984 and recent records in cen- Status, 32-40 (suppl.), 206-212 tral and southern Baja California Peninsula, 3-9 Steenhof, Karen, A review of The Raptor Almanac, by (suppl.) Scott Weidensaul, 2000, 87-88 Rogers, Andi, see Bloxton, Thomas D. Steenhof, Karen, see Kochert, Michael N. Rome, 224-228 Stephanoaetus coronatus, 300—308 Rosenstock, Steve, see Bloxton, Thomas D. Stinson, Derek, see Watson, James W. Roth, Aaron Gwilym S. Jones, and Thomas W. French, J., Subspecies, 17-23 Incidence of naturally-healed fractures in the pec- Surai, Peter E, see Barton, Nigel W.H. toral bones of North American Accipiters, 229-230 Survey, 39-44 Ruf, Thomas, see Janovsky, Martin broadcast, 170-175 roadside, 51-57 S winter, 128-135

Sabo, Beth Ann, see Ellis, David H. Survival, 3-10, 176-182 Salvati, Luca, Lamberto Ranazzi, and Alberto Manganaro, ,

350 Index to Volume 36 VoL. 36, No. 4

T W

Tea plantation, 51-57 Waclawek, Krzysztof and Tadeusz Mizera, The status of Temperature, 294-299 the Golden Eagle {Aquila chrysaelos) in Poland, 25- Territoriality, 62-69 (suppl.) 28 (suppl.) Territories, 224-228 Wallis, Robert, see Cooke, Raylene Thorstrom, Russell, Comments on the first nesting re- Warnke, D. Keith, David E. Andersen, Cheryl R. Dykstra, cord of the nest of a Slaty-backed Forest-Falcon {Mi- Michael W. Meyer, and William H. Karasov, Provi- crastur mirandollei) in the Ecuadorian Amazon, 335- sioning rates and time budgets of adult and nestling 336 Bald Eagles at inland Wisconsin nests, 121-127 Thorstrom, Russell, Richard Watson, Aaron Baker, Ser- Warnke, D. Keith, see Dykstra, Cheryl R. ena Ayers, and David L. Anderson, Preliminary Washburn, Lowell, see Powell, Larkin A. ground and aerial surveys for Orange-breasted Fal- Washington, 161-169, 265-279 cons in Central America, 39-44 Watson, James W., Derek Stinson, Kelly R. McAllister, and Thorstrom, Russell, see Rafanomezantsoa, Simon Thomas E. Owens, Population status of Bald Eagles Tiletamine, 188-193 breeding in Washington at the end of the 20^’^ cen- Tillman, Eric A., see Avery, Michael L. tury, 161-169 Time budgets, 121-127 Watson, Jeff and Philip Whitfield, A conservation frame- Tmgay, Ruth E., Melanie Culver, Eric M. Hallerman, work for the Golden Eagle {Aquila chrysaetos) in Scot- James D. Fraser, and Richard T. Watson, Subordinate land, 41-49 (suppl.) males sire offspring in Madagascar Fish-Eagle {Hal- Watson, Richard, see Thorstrom, Russell iaeetus vociferoides) polyandrous breeding groups, Watson, Richard T., see Berkelman, James 280-286 Watson, Richard T., see Rafanomezantsoa, Simon Toffoli, Roberto, see Boano, Giovanni Watson, Richard T., see Tingay, Ruth E.

Tordoff, Harrison B., see Martell, Mark S. Weather conditions, 81-84 Transect, 128-135 Welford, Mark R., see Nunnery, Tony Translocation, 91-96 Whitacre, David R, Juventino Lopez Avila, and Gregorio Tropical, 77-81 Lopez Avila, Behavioral and physical development of Tryjanowski, Piotr, see Yosef, Reuven a nestling Crested Eagle {Morphnus guianensis) 77— Tyto alba, 146-148, 224-228 81 White, John, see Cooke, Raylene U Whitheld, D. Philip, see McLeod, David R.A. Whitfield, Philip, see Watson, Jeff Uganda, 51-57 Wiedenfeld, David A., see Jenkins, M. Alan Urban, habitats, 81-84, 224—228 Wiesmann, Karen, see Brendel, Ulrich M. wildlife, 91-96 Wildlife, habitat relationships, 265-279 wildlife management, 3-10 management, 300-308 Urbanization, 294—299 Wind energy, 55-61 (suppl.) Urios, Gerardo, see Martinez-Abrain, Alejandro Winter quarters, 148-152 U.S., 32-40 (suppl.) Wintering, 256-264 ecology, 328-331 V Wisconsin, 121-127

Wolfe, Jr., Donald H., see Jenkins, M. Alan Vargas, Julieta, Carlos Landaeta A., and Javier A. Simo- Wood, Petra Bohall, see Ammer, Frank K. netti. Bats as prey of Barn Owls { Tyto alba) in a tropical savanna in Bolivia, 146-148 Y Variability, 218-219

Varland, Daniel E., see Finn, Seair P. Yosef, Reuven, Piotr Tryjanowski, and Keith Bildstein, Vegetation structure, 294-299 Spring migration of adult and immature buzzards Video camera, 136-139 {Buteo buteo) through Elat, Israel; timing and body Vitamins, 33-38 size, 115-120 Voucher specimens, 183-187 Vultures, 45-50 Z Bearded, 66-70 Zacatecas, 3-9 (suppl.) Egyptian, 17-23 Zemplen Mountains, 18-19 (suppl.) Turkey, 144—145 Zenker, Wolfgang, see Janovsky, Martin Yellow-headed, 183-187 Zolazepam, 188-193 Zones, 41-49 (suppl.) THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC. (Founded 1966)

EDITOR IN CHIEF James C. Bednarz

ASSOCIATE EDITORS James R. Belthoff Marco Restani Clint W. Boal Ian G. Warrentin Joan L. Morrison Troy I. Wellicome Juan Jose Negro BOOK REVIEW EDITOR Jeffrey S. Marks .

CONTENTS FOR VOLUME 36, 2002

Number 1

Editor’s Page: Working Toward Excellence. James C. Bednarz 1

Survival of Florida Burrowing Owls Along an Urban-Development Gradient. Brian A. Millsap 3

Biases Associated with Diet Study Methods in the Eurasian Eagle-Owl. Luigi Marchesi, Paolo Pedrini, and Fabrizio Sergio 11

Description of a New Subspecies of the Egyptian Vulture (Accipitridae; Neo- phron fercnopterus) FROM THE Canary Islands. Jose Antonio Donazarjuan Jose Negro, Cesar Javier Palacios, Laura Gangoso, Jose Antonio Godoy, Olga Ceballos, Fernando Hiraldo, and Nieves Capote 17

Density, Nest Sites, Diet, and Productivity of Common Buzzards {Bijteo buteo) in the Italian Pre-Alps. Fabrizio Sergio, Alberto Boto, Chiara Scandolara, and Giuseppe Bogliani 24

Vitamins E and A, Carotenoids, and Fatty Acids of the Raptor Egg Yolk. Nigel

W.H. Barton, Nicholas C. Fox, Peter F. Surai, and Brian K. Speake 33

Preliminary Ground and Aerial Surveys for Orange-breasted Falcons in Central

America. Russell Thorstrom, Richard Watson, Aaron Baker, Serena Ayers, and David L. Anderson 39

Dispersing Vulture Roosts on Communication Towers. Michael l. Avery, John s, Humphrey, Eric A. Tillman, Kimberly O. Phares, and Jane E. Hatcher 45

Raptor Abundance and Habitat Use in a Highly-Disturbed-Forest Landscape in Western Uganda. Nathaniel E. Seavy and Christine K. Apodaca 51

Trophic Niche of North American Great Horned Owix. Lee a. Cromrich, Denver w. Holt, and Shawne M. Leasure 58

Short Communications

Social Organization of a Trio Of Bearded Vultures ( Gypaetus barbatus) : Sexual and Parental Roles. Joan Bertran and Antoni Margalida 66

Genetic Evidence of Ali.oparental Care of a Female Lesser Kestrei. in an Alien Nest. Pedro J. Cordero, Jose M. Aparicio, and David T. Parkin 70

NE.STING OF Long-eared Owls Along the Lower Big Lost River, Idaho: A Comparison of 1975-76 and 1996-97. Natalie A. Fahler and Lester D. Flake 73

Behavioral and Ph\sical Development of a Nestling Crested Eagle {Morphnus GuiANENsrs) David

F. Whitacre, Juventino Lopez Avila, and Gregorio Lopez Avila 77

Spring Weather and Breeding Success of the Eurasian Kestrel {Falco riNNUNCULUs) in Urban

Rome, Italy. Luca Salvati 81

Eatal Caryospora Infection in a Free-living Juvenile Eurasian Kestrel {Falco riNmmcuLus) .Olivei: Krone 84 Book Review. Edited by Jeffrey S. Marks 87

Manuscript Referees 89

Number 2

An Urban Osprey Population Established by Translocation. Mark s. Marteii, Judy Voigt Englund, and Harrison B. Tordoff 91

Breeding Grounds, Winter Ranges, and Migratory Routes of Raptors in the

Mountain West. Stephen W. Hoffman, Jeff P. Smith, and Timothy D. Meehan 97

Circuitous Autumn Migration in the Short-toed Eagle ( Circaetus gallicus) . Nicolantonio Agostini, Luca Baghino, Charles Coleiro, Ferdinando Corbi, and Guido Premuda Ill

Spring Migration of Adult and Immature Buzzards {Buteo buteo) through Elat,

Israel: Timing and Body Size. Reuven Yosef, Piotr Tryjanowski, and Keith L. Bildstein 115

Provisioning Rates and Time Budgets of Adult and Nestling Bald Eagles

AT Inland Wisconsin Nests. D. Keith Wamke, David E. Andersen, Cheryl R. Dykstra, Michael W. Meyer, and William H. Karasov 121

A Line Transect Survey of Wintering Raptors in the Western Po Plain of Northern Italy. Giovanni Boano and Roberto Toffoli 128

Short Communications

Bald Eagle Reproductive Performance Following Video Camera Placement. Cheryl R. Dykstra, Michael W. Meyer, and D. Keith Warnke 136

Absence of Bi.ood Parasites in Nestlings of the Eleonora’s Falcon {Falco ejmonoraf). Alejandro Martinez-Abram and Gerardo Urios 139

Possible Choking Mortalities of Adult Northern Goshawks. Thomas D. Bloxton, Andi Rogers,

Michael F. Ingraldi, Steve Rosenstock, John M. Marzluff, and Sean P. Finn 141

Exhumation of Food by Turkey Vulture. Harvey R. Smith, Richard M. DeGraaf, and Richard S. Miller 144

Bats as Prey of Barn Owls ( lYro alba) in a Tropical Savanna in Bolivia. Julieta Vargas, Carlos

Landaeta A., and Javier A. Simonetti 146

Food of the Lesser Kestrel (Falco naumanni) in its Winter Quarters in South Africa. Grzegorz Kopij 148

Red-shouldered Hawk Feeds on Carrion. Bill Pranty 152

Letters

First Repiacement Clutch by a Polvandrous Trio of Bearded Vultures (Gypaetus baebatus) in the Spanish Pyrenees. Antoni Margalida and Joan Bertran 154

Mississippi Kites Use Swallow-tailed Kite Nests. Jennifer O. Coulson 155

Erratum 157 Number 3

Population Status of Breeding Bald Eagles in Washington at the end of the

20th Century. James W. Watson, Derek Stinson, Kelly R. McAllister, and Thomas E. Owens 161

Response Distance of Ferruginous Pygmy-Owls to Broadcasted Conspecific

Calls. Glenn a. Proudfoot, Sam L. Beasom, Felipe Chavez-Ramirez, and Jody L. Mays 170

POST-FLEDGING SURVIVAL AND DISPERSAL OF PEREGRINE FALCONS DURING A RESTORATION

Project. LarkinA. Powell, DanJ. Calvert, Irene M. Barry, and Lowell Washburn 176

Morphology, Genetics, and the Value of Voucher Specimens: An Example with

CATT/ARTES Vultures. Carole S. Griffiths and John M. Bates 183

Oral Administration of Tiletamine/Zolazepam for the Immobilization of the

Common Buzzard {BUTEO BUTEO) . Martinjanovsky, Thomas Ruf, and Wolfgang Zenker 188

Hunting Behavior of and Space Use by Eastern Screech-Owls during the

Breeding Season. Jennifer E. Buhay and Gary Ritchison 194

Short Communications

ScHizocHROMiSM IN A PEREGRINE Falcon erom ARIZONA. David H. Ellis, Lynn W. Oliphant, and James

K. Fackler 200

Natal Dispersal of the Crested Caracara (Caracara cherjway) in Florida. Nicole M. Nemeth and

Joan L. Morrison 203

Recent Records of Crowned Eagles {Harpyhaliaetus coronatus) from Argentina, 1981-2000.

M. Isabel Bellocq, Patricio Ramirez-Llorens, and Julieta Filloy 206

New Observations of the Peregrine Falcon {Falco peregrinus) in Peru. Marc Kery 213

DNA Polymorphisms in Boreai. Owls {Aegolius funereus) . Janne Beheim, Katrine Eldegard, Gro Bj0rnstad, Mats Isaksson, Geir Sonerud, Olav Heie, and Helge Klungland 218

Post-fledging Movements and Foraging Habitats of Immature White-tailed Sea Eagi.es in the

Nemuro Region, Hokkaido, Japan. Saiko Shiraki 220

Habitat Preferences, Breeding Success, and Diet of the Barn Owl (Tyto alba) in Rome; Urban

versus Rural Territories. Luca Salvati, Lamberto Ranazzi, and Alberto Manganaro 224

Incidence of Naturally-healed Fractures in the Pectoral Bones of North American Accipiters.

Aaron J. Roth, Gwilym S. Jones, and Thomas W. French 229

Piasma Chemistry Reference Values in Free-living Bonelli’s Fagle (Hieraaetus fasciatus)

Nestlings. Javier Balbontin and Miguel Ferrer 231

Letters

The Fox Kestrel {Falco alopex) Hoytrs. Tiziano Londei 236

Probable Breeding of Short-eared Owls in Southern West Virginia. Frank K. Ammer and Petra Bohall Wood 237

Endangered Egyptian Vulture {Neophron percnopierus) Entangled in Powerline Ground-wire Stabilizer.

Laura Gangoso and Cesar J. Palacios 238 Barred Forest-Falcon {Miciustur ruficollis) Predation on a Hummingbird. Tony Nunnery and

Mark R. Welford 239

Book Reviews. Edited byjeffrey S. Marks 241

Number 4

Foraging Ecology of Nesting Bald Eagles in Arizona, w. Grainger Hunt, Ronald e.

Jackman, Daniel E. Driscoll, and Edward W. Bianchi 245

Vernal Migration of Bai.d Eagles from a Southern Colorado Wintering Area.

Alan R. Harmata 256

Does Northern Goshawk Breeding Occupancy Vary with Nest-stand Character-

istics on the Olympic PeNINSUIA, Washington? Sean P. Finn, Daniel E. Varland, and John M. Marzluff 265

Subordinate Males Sire Offspring in Madagascar Fish-Eagle {Haliaeetus vociee-

ROWES) POLYVNDROUS BREEDING GROUPS. Ruth E. Tingay, Melanie Culver, Eric M.

Hallerman, James D. Fraser, and Richard T. Watson 280

Nesting and Perching Habitat Use of the Madagascar Fish-Eagle. James Berkeiman,

James D. Fraser, and Richard T. Watson 287

Use of Vegetative Structure by Powerful Owls in Outer Urban Melbourne, Victoria, Austraija—Implications for Management. Rayiene Cooke, Robert WaiUs, and John White 294

Nest-Site Selection of the Crowned Hawk-Eagle in the Eorests of Kwazulu- NATAL, South Africa, and TAI, Ivory Coast. Gerard Malan and Susanne Shultz 300

Short Communications

Juvenile Dispersal of Madagascar Fish-Eagles Tracked by Satellite Telemetry. Simon

Rafanomezantsoa, Richard T. Watson, and Russell Thorstrom 309

Prey OF the Peregrine Falcon {Falco Peregrinus cassini) in Southern Argentina and Chile. David

H. Ellis, Beth Ann Sabo, James K. Fackler, and Brian A. Millsap 315

An Elevated Net Assembly to Capture Nesting Raptors. Eugene A. Jacobs and Glenn A. Proudfoot 320

Florida Bald Eagle {Haliaeetus teucocephalus) Egg Characteristics. M. Alan Jenkins, Steve K.

Sherrod, David A. Wiedenfeld, and Donald H. Wolfe, Jr. 324

Osprey Ecology IN THE Mangroves OF Southeastern Brazil. Robson Silva e Silva, Fabio Olmos .... 328

Diet of Breeding Tropical Screech-Owls ( Otus choliba) in Southeastern Brazil. Jose Carlos Motta-Junior 332

Letters

Comments of the First Nesting Record of the Nest of a Slaty-backed Forest Falcon {Micrastur

MIRANDOLLEI) IN THE ECUADORIAN AMAZON. Russell Thorstrom 335 Micrastur or Accipiter, That is the Question. Tjitte de Vries and Cristian Melo 337

Book Reviews. Edited by Jeffery S. Marks 338

Information For Contributors 340

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BUTEO BOOKS is the largest retailer of Ornithology titles in North America, with over 2000 in-print titles in stock.

In-Print Falconry and Birds of Prev

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Volume 3, covering owls. They are priced at $185 each.

The Raptor Almanac: A Comprehensive Guide to Eagles, Hawks, Falcons, and Vultures. Scott Weidensaul. Lyons Press, 2000. 382 pp. Color photos. Cloth. $40.00

The Harris Hawk: Management, Training and Hunting. Lee W. Harris. Swan Hill Press, 2001. 144 pp. Color and b&w photos and illustrations. Cloth. $32.95

Rare and Out-of-print Falconry Usually available from Buteo Books, the classic reference on diurnal raptors: Brown & Amadon: Eagles, Hawks and Falcons ofthe World. First English edition, 1968. $300.

Birds of North America series individual species accounts for over 500 species, including: Swallow-tailed Kite Zone-tailed Hawk Northern Hawk Owl White-tailed Kite Hawaiian Hawk Northern Pygmy-Owl. Snail Kite Red-tailed Hawk Ferruginous Pygmy-Owl Mississippi Kite Ferruginous Hawk Elf Owl Bald Eagle Crested Caracara Burrowing Owl Northern Harrier American Kestrel Spotted Owl Sharp-shinned Hawk Merlin Barred Owl Cooper’s Hawk Gyrfalcon Great Gray Owl Northern Goshawk Prairie Falcon Long-eared Owl Common Black-Hawk Bam Owl Short-eared Owl (R) Harris’ Hawk Flammulated Owl Boreal Owl Red-shouldered Hawk Eastern Screech-Owl Northern Saw-whet Owl Broad-winged Hawk Whiskered Screech-Owl Available soon: Swainson’s Hawk Great Homed Owl American Kestrel White-tailed Hawk Snowy Owl California Condor .

2003 ANNUAL MEETING

The Raptor Research Foundation, Inc. 2003 annual meeting will be held on 3-7 September 2003 in Anchorage, Alaska. For information about the meeting see the following website: http://www. alaskabird.org or contact Nancy DeWitt ([email protected])

Persons interested in predatory birds are invited to join The Raptor Research Foundation, Inc. Send inquests for information concerning membership, subscriptions, special publications, or change of address to OSNA, P.O. Box 1897, Lawrence, KS 66044-8897, U.S.A. TheJournal ofRaptor Research (ISSN 0892-1016) is published quarterly and available to individuals for $33.00 per year and to libraries and institutions for $50.00 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 continental United States.) Periodicals postage paid at Hastings, Minnesota, and additional mailing offices. POSTMASTER: Send address changes to TheJournal ofRaptor Research, OSNA, P.O. Box 1897, Lawrence, KS 66044-8897, U.S.A. Printed by Allen Press, Inc., Lawrence, Kansas, U.S.A. Copyright 2002 by The Raptor Research Foundation, Inc. Printed in U.S.A. © This paper meets the requirements of ANSi/NISO Z39.48-1992 (Permanence of Paper).

Raptor Research Foundation, Inc., Awards Lifetime Achievement Awards

The Tom Cade Award recognizes an individual who has made significant advances in the area of captive prop- agation and reintroduction of raptors. Nomination packets can be submitted at any time. Contact: Brian Walton, Predatory Bird Research Group, Long Marine Laboratory, University of California, Santa Cruz, CA

95064 U.S.A.; tel. 408-459-2466; e-mail: [email protected]. The Fran and Frederick Hamerstrom Award recognizes an individual who has contributed significandy to the understanding of raptor ecology and natural history. Nomination packets can be submitted at any time. Con-

tact: Dr. Clint Bo

15th Street & Boston, Ag Science Bldg., Room 218, Lubbock TX 79409-2120 U.S.A.; tel. (806) 742-2851; e-mail: [email protected].

Student Recognition and Travel Assistance Awards

The James R. Koplin Travel Award is given to a student who is the senior author and presenter of a paper or poster to be presented at the RRF annual meeting for which travel funds are requested. Contact; Dr. Patricia

A. Hall, 5937 E. Abbey Rd. Flagstaff, AZ 86004 U.S.A.; tel. 520-526-6222; e-mail: [email protected]. Application Deadline: due date for meeting abstract.

The William C. Andersen Memorial Award is given to the students who are senior authors and presenters of the best student oral and poster presentation at the annual RRF meeting. Contact: Laurie Goodrich, Hawk

Mountain Sanctuary, 1700 Hawk Mountain Road, Kempton, PA 19529 U.S.A.; tel. 610-756-6961; email; [email protected]. Application Deadline: due date for meeting abstract; no special application

is needed.

Grants

For each of the following grants, complete applications must be submitted to the contact person indicated by 15 February. Recipients will be notified by 15 April.

The Dean Amadon Grant for $200-400 is designed to assist persons working in the area of distribution and sys- tematics (taxonomy) of raptors. Contact: Dr. Carole Griffiths, 251 Martling Ave., Tarrytown, NY 10591

U.S.A.; tel. 914-631-2911; e-mail: [email protected].

The Stephen R. Tully 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; Dr. Kim Titus, Alaska Department of Fish and Game, Division of Wildlife Conservation, P.O. Box 240020, Douglas, AK 99824 U.S.A; e-mail; [email protected]. The Leslie Brown Memorial Grant for up to $1,000 to support research and/ or dissemination of information on birds of prey, especially to proposals concerning African raptors. Contact: Dr. Jeffrey L. Lincer, 9251 Golondrina Dr., La Mesa, CA 91941 U.S.A.; e-mail: [email protected].