Journal of Raptor Research
Published by: The Raptor Research Foundation
Table of Contents
September 2016 : Volume 50 Issue 3
Reproductive Success of Eurasian Eagle-Owls in Wetland and Non-wetland Habitats of West-central Korea
Dong-Man Shin and Jeong-Chil Yoo
The breeding success of raptors is strongly affected by food supply. We examined the reproductive success of Eurasian Eagle-Owls (Bubo bubo) and assessed the effects of landscape and diet on reproductive success at 44 nest sites in wetland and non-wetland (mostly agricultural lands, forests, and human settlements) habitats in west-central Korea. We found that eagle-owl reproductive success was significantly higher in wetland than in non-wetland habitats (mean of 1.9 vs. 1.3 fledglings per breeding pair, respectively). Although the average number of fledglings per successful pair was similar in the two habitats (2.0 vs. 1.8), the average numbers of fledglings per hatchling (0.9 vs. 0.7) and per egg (0.8 vs. 0.5) were both higher in wetland habitats. Further, for the wetland habitats, birds (mostly Anatidae, Columbidae, and Phasianidae) were the most important prey group by both number and biomass (67% and 84%, respectively) in the breeding period. However, in non-wetland habitats, both mammals (59% by number) and birds (67% by biomass) were important prey in the breeding period. The amount of Phasianidae in the diet (by biomass) and the date of the onset of egg-laying were positively and negatively (respectively) significant determinants of the number of fledglings per egg, whereas the percentage of wetland in the habitat was the only significant determinant for the number of fledglings per hatchling.
Observations of Migrating Golden Eagles (Aquila chrysaetos) in Eastern Interior Alaska Offer Insights On Population Size and Migration Monitoring
Carol L. McIntyre and Stephen B. Lewis
Migratory Golden Eagles (Aquila chrysaetos) from Alaska winter across a vast region of western North America, much of which is undergoing rapid change from a diversity of indirect and direct human activities. To address recent conservation concerns, we are studying the year-round movements of migratory Golden Eagles from interior and northern Alaska to identify and evaluate potential risks to their survival. We are also developing new survey techniques to estimate population size and trends. As part of our ongoing studies, we observed migrating Golden Eagles in spring and autumn 2014 during field investigations to locate Golden Eagle capture sites in eastern interior Alaska, and in spring 2015 during capture activities. We observed large numbers of Golden Eagles in both spring and autumn, suggesting that the Mentasta Mountains are an important migration corridor for this species. Further, our observations, including 1364 migrating Golden Eagles in October 2014, suggested that the Alaska Golden Eagle population is much larger than is reflected in the only currently available statewide population estimate of 2400 eagles. In combination with historical and contemporary tracking studies, our observations in the Mentasta Mountains provide important new information about Golden Eagle migration in Alaska and stimulate interest in answering fundamental questions about using counts of migrating Golden Eagles to estimate, and detect change in, the population size of Alaska's migratory Golden Eagles. Our observations also provide new information about Rough-legged Hawk migration in Alaska.
Retention, Effect, and Utility of Tail-mounted Satellite-tracked Transmitters on Golden Eagles
Alan R. Harmata
Studies deploying Platform Transmitter Terminals (PTTs) or Global System for Mobile Communications-GPS (GSM) packages on Golden Eagles have typically used backpack harnesses for attachment despite evidence indicating potential significant negative effects on reproduction and survival. Retention, safety, and utility of tail-mounted PTTs were tested on a sample of Golden Eagles in southwestern Montana. Argos satellite-tracked PTTs of two configurations were attached dorsally or ventrally to the central rectrices of 27 Golden Eagles to study survival. Sixteen packages were known to have been molted or removed (i.e., shed) by the eagle and 13 recovered. Of recovered tail-mounts, six (46%) were forcibly removed by eagles; five by males and one by a female. All packages that were forcibly removed were 32-g ventral mounts. Females tended to retain tail-mounts longer than males and dorsally mounted PTTs tended to be retained longer than those mounted ventrally. Eagles tagged in winter retained PTTs the longest. The duration of tail-mounted PTT retention was adequate for analysis of survival and yielded an adult annual survival rate (86%) consistent with recent U.S. Fish and Wildlife Service estimates (87%). Eight of 13 (62%) territorial adults tagged with PTTs were known to attempt breeding the year they were tracked and six (46%) produced young, rates that did not differ (P > 0.23) from those of a larger sample of the population surveyed during the same period. Logistic regression analysis of cumulative range size by monitoring duration of four territorial adult eagles with tail-mounted GPS indicated that 99% of total range was recorded within 140 d of tracking.
Temporal and Spatial Dietary Variation of Amur Falcons (Falco amurensis) in their South African Nonbreeding Range
Jarryd Alexander and Craig T. Symes
We studied the spatial and temporal dietary patterns of the Amur Falcon (Falco amurensis), a nonbreeding Palearctic migrant to South Africa, by collecting regurgitated pellets at two large colonial roost sites, i.e., Middelburg and Newcastle, over 11 equal sampling periods during December 2012 to March 2013. We dried the pellets to constant mass and classified the prey items to the lowest taxonomic level possible. Amur Falcons fed mainly on invertebrates (seven orders), and occasionally on vertebrates (three orders). The five most abundant prey taxa (pooled for both sites) were; Coleoptera, Orthoptera, Isoptera, Solifugae, and Hymenoptera. Lepidoptera, Hemiptera, Passeriformes, Rodentia, and Soricomorpha were consumed almost 20 times less frequently. Isoptera, Hymenoptera, Lepidoptera, and Rodentia were consumed significantly more frequently at Middelburg, while Orthoptera and Solifugae were consumed more frequently at Newcastle. The consumption of Coleoptera did not differ significantly between sites but decreased through the season, being most important when falcons arrived in South Africa in December. Consumption of Orthoptera increased through the season and was greatest prior to migration. The percentages of Isoptera and Hymenoptera in the diet peaked at different periods, likely the result of prey population irruptions. Diet similarity of sample periods between sites ranged from 33.3–100% (mean = 69.5%), and within-site similarity among sample periods ranged from 50–100% (mean = 75.6%) and 37.5–100% (mean = 65.9%) for Newcastle and Middelburg, respectively. This study highlights the variable importance of specific prey taxa, predominantly invertebrates, for Amur Falcons during the overwintering period in South Africa.
Seroprevalence of Avian Pox and Mycoplasma gallisepticum in Raptors in Central Illinois
Elizabeth R. Wrobel, Travis E. Wilcoxen, Jacques T. Nuzzo and Jane Seitz
We assessed prevalence of the bacterium Mycoplasma gallisepticum and virus Avipoxvirus in seven species of raptors admitted to the Illinois Raptor Center from 1 January 2014 to 1 September 2015. We used visual identification of pathology to diagnose current infections and enzyme-linked immunosorbent assays (ELISA) for avian IgY antibodies against each pathogen to determine infection history of the birds. Seroprevalence of IgY against each pathogen differed significantly among species. Species that commonly prey upon birds had a greater prevalence of antibodies against each pathogen. Our finding of infrequent physical signs of disease, but frequent antibody presence, suggests that although exposure to each of these pathogens is not a rare occurrence, these raptors are capable of mounting an effective adaptive immune response and preventing development of pathology in most cases.
A Comparison of Nest Survival Between Cliff- and Tree-nesting Golden Eagles
Ross H. Crandall, Derek J. Craighead and Bryan E. Bedrosian
Morphometric Sex Determination of After-hatch-year Bald Eagles in Louisiana
Nickolas R. Smith, Alan D. Afton and Thomas J. Hess,Jr.
Body Mass of Female Cooper's Hawks is Unrelated to Longevity and Breeding Dispersal: Implications for the Study of Breeding Dispersal
Robert N. Rosenfield, John Bielefeldt, Taylor G. Haynes, Madeline G. Hardin, Frederick J. Glassen and Travis L. Booms
First Record of Peregrine Falcon (Falco peregrinus) Ground Nesting Activity on the U.S. Atlantic Coast
Ruth Boettcher and Elizabeth K. Mojica
Long-term Occupancy (1900–2015) of an Egyptian Vulture Nest
Juan Ramírez, Julio Roldan, Manuel de la Riva and José A. Donázar
Predation of Dawn-swarming Bats by Eurasian Hobby (Falco subbuteo)
David J. Stanton
Aerial Rolling Behavior by a Crested Caracara (Caracara cheriway)
Daniel M. Brooks and Steven G. Mayes
Evidence of an Urban Peregrine Falcon (Falco peregrinus) Feeding Young at Night
Esther F. Kettel, Louise K. Gentle and Richard W. Yarnell
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