Search birdRS Box

Search birdRS blog posts

Browse the Blog Posts

Or scan through the blog archive below for items of interest as only the latest post is shown below, thanks.

Tuesday, 1 September 2015

Journal of Raptor Research ; September 2015 : Volume 49 Issue 3

Journal of Raptor Research
Published by: The Raptor Research Foundation

Table of Contents
September 2015 : Volume 49 Issue 3 


Landfill Use by Bald Eagles in the Chesapeake Bay Region
Courtney Turrin, Bryan D. Watts and Elizabeth K. Mojica

We examined patterns in the use of landfills (rubbish dumps) in the Chesapeake Bay by Bald Eagles (Haliaeetus leucocephalus). Sites of solid waste landfills (n  =  72) were located using state databases. Satellite tracking data from 64 eagles were used to track eagle movements hourly during daylight and once at midnight to determine roosting locations (2007–2012). Landfill use varied significantly with age class, with hatch-year birds using landfills six times more often than adults and twice as often as third- and fourth-year birds. Hatch-year birds spent significantly more time at landfills than expected based on landfill area relative to the study area outside of landfills. The relationship between time of year and eagle presence at landfills was not significant, though the results suggest a peak in landfill use in the late fall. There was spatial variation in landfill use, with 10% of the landfills used by study birds receiving 75% of the total landfill use. Landfills within two km of communal roosts received significantly more eagle activity than landfills farther from communal roosting sites. If eagle presence at landfills is indicative of foraging at these sites, the results provide evidence that foraging strategies in Bald Eagles change with age. Landfills may serve as important scavenging sites for hatch-year and second-year eagles, whereas older birds may be more successful obtaining higher quality prey elsewhere.

Seasonal Variation in Space Use by Nonbreeding Bald Eagles Within the Upper Chesapeake Bay 
Bryan D. Watts, Elizabeth K. Mojica and Barton J. Paxton

Access to food resources is essential to self-maintenance and reproduction and, for species of conservation concern, foraging areas are considered critical habitat. Human disturbance is an important factor restricting access to prey resources for Bald Eagles (Haliaeetus leucocephalus) and guidelines in the Chesapeake Bay have been developed to mitigate its impact. However, our ability to implement such guidelines has been limited by a lack of information on important foraging areas. We used Brownian bridge movement modeling to develop a population-wide utilization probability surface for Bald Eagles along shorelines within the upper Chesapeake Bay. We used locations (n  =  320 304) for individuals (n  =  63) tracked with GPS satellite transmitters between 2007 and 2011 in the analysis. We examined seasonal variation by developing utilization surfaces for summer and winter. Although shoreline use was widespread, segments receiving high levels of activity were relatively rare. Shoreline classified as having the highest category of use and accounting for 10% of the total utilization made up 0.41% and 0.55% of the total shoreline for winter and summer, respectively. From a management perspective, there is a clear pattern of diminishing returns in conservation value for including sequentially lower-use shorelines in land-use management plans. Shoreline use shifted dramatically in both location and extent between seasons. During the summer months, use was highly concentrated on shorelines along the main stem of the Chesapeake Bay or along major (>1 km wide) tributaries. During the winter months, use shifted away from the main stem of the bay and was more focused on minor (<100 m wide) tributaries and inland ponds. Seasonal shifts in shoreline use suggest the need for season-based management objectives.

Wintering Bald Eagle Count Trends in the Conterminous United States, 1986–2010 
Wade L. Eakle, Laura Bond, Mark R. Fuller, Richard A. Fischer and Karen Steenhof

We analyzed counts from the annual Midwinter Bald Eagle Survey to examine state, regional, and national trends in counts of wintering Bald Eagles (Haliaeetus leucocephalus) within the conterminous 48 United States from 1986 to 2010. Using hierarchical mixed model methods, we report trends in counts from 11 729 surveys along 844 routes in 44 states. Nationwide Bald Eagle counts increased 0.6% per yr over the 25-yr period, compared to an estimate of 1.9% per yr from 1986 to 2000. Trend estimates for Bald Eagles were significant (P ≤ 0.05) and positive in the northeastern and northwestern U.S. (3.9% and 1.1%, respectively), while trend estimates for Bald Eagles were negative (P ≤ 0.05) in the southwestern U.S. (−2.2%). After accounting for potential biases resulting from temporal and regional differences in surveys, we believe trends reflect post-DDT recovery and subsequent early effects of density-dependent population regulation.

Attributes of a Breeding Population of Peregrine Falcons Associated with Reservoirs on the Colorado River 
Joseph G. Barnes, Ross D. Haley, Daniel B. Thompson and Jef R. Jaeger

We describe results from a comprehensive effort to survey and monitor Peregrine Falcons (Falco peregrinus) breeding in Lake Mead National Recreation Area (LMNRA) from 2006–2010. We identified 37 breeding territories, and the annual occupancy rate averaged 94%. Pooled over time, breeding success was 72%, and average reproductive output was 1.8 young per nesting attempt. The closest distance between eyries from neighboring territories was 1.2 km; the lowest annual mean nearest-neighbor distance (NND) was 6.3 km. No relationship was apparent between NND and breeding success or reproductive output. Nesting attempts occurred twice as often in eyries with a north-facing (68%) aspect than in eyries with a south-facing (32%) aspect. Pairs using south-facing eyries began incubating 5 d earlier than those using north-facing eyries, although the difference was not statistically significant. On a finer scale, pairs most commonly selected northwest-facing eyries (45% of nesting attempts), despite experiencing a trend of lower mean breeding success (64%) than in eyries with aspects facing all other quadrants (83%). Within territories, peregrines used alternate eyries following 58% of nesting attempts; however, switching eyries between years did not influence breeding success. Peregrines appear to be largely year-round residents at LMNRA, based on monthly surveys at five territories during a nonbreeding season (August 2008 through January 2009). We also detected peregrines at 10 of 24 territories in September and October 2009 using 10-min call-broadcast surveys at eyrie cliffs. Our results contribute to knowledge of increasing populations of peregrines following the DDT era in the southwestern U.S., and provide insight about how reservoirs may influence local breeding populations.

Origin, Growth, and Composition of the Recovering Peregrine Falcon Population in Ontario 
Marcel A. Gahbauer, David M. Bird and Ted (E.R.) Armstrong

After an absence of more than two decades, Peregrine Falcons (Falco peregrinus) resumed nesting in Ontario in 1986. Between 1991 and 2006, at least 193 young fledged in southern Ontario and 548 young fledged in northern Ontario. The number of breeding pairs, nesting attempts, successful nests, and young fledged all steadily increased in both regions throughout this period. In southern Ontario, 25% of the breeding adults produced nearly 50% of all fledglings, and 87% of the fledglings came from just eight breeding sites. Direction of natal dispersal was variable, but females consistently moved farther than males, and there was frequent movement both to and from adjacent American states. The population recovery resulted from the release of 592 captive-bred F. p. anatum juveniles in Ontario between 1977 and 2005, plus immigration from other provinces and release efforts in adjacent regions of the United States, where at least five subspecies contributed to the gene pool of captive-bred birds. Encounter rates for both captive-bred and wild-fledged young in Ontario have been low, but wild-raised young have been recruited to the breeding population almost twice as frequently as captive-bred birds. This difference partially explains the genetic composition of the southern Ontario population, where at most 21% of nesting attempts between 1995 and 2006 involved a pair of Canadian-released anatum adults, and 59% of cases involved at least one adult of American origin. Therefore, although the Ontario population has exceeded documented historical levels, it may not be greater than actual historical numbers, and it cannot be strictly considered an anatum population.

High Prevalence of Leucocytozoon Parasites in Nestling Northern Goshawks (Accipiter gentilis) in the Northern Great Basin, U.S.A. 
Michelle I. Jeffries, Robert A. Miller, Michelle D. Laskowski and Jay D. Carlisle

The Northern Goshawk (Accipiter gentilis) is currently listed as a sensitive species by the U.S.D.A. Forest Service. Previous research in our study area, the South Hills of the Minidoka Ranger District of the Sawtooth National Forest, Idaho, identified possible signs of parasite infections among the banded adult and nestling goshawks, which could influence their survival and breeding success. Therefore, we sought to quantify the prevalence and intensity of Leucocytozoon parasites among a sample of nestling goshawks in the South Hills during the 2012 breeding season. We sampled 27 nestlings from 12 nests for Leucocytozoon parasites by examining blood smears. All sampled nestlings were infected with Leucocytozoon parasites. The infection intensity ranged from 0.82–10.05 Leucocytozoon parasites per 1000 erythrocytes (mean ± SE  =  4.35 ± 0.54). Using site elevation, distance-to-water, nestling age, nestling sex and nest tree species as predictor variables for infection intensity by Leucocytozoon parasites, we employed an information theoretic approach to select a top model to determine the presence of an effect. The top model included nest tree species as the sole predictor for infection intensity. Specifically, higher Leucocytozoon parasite intensity was associated with quaking aspen (Populus tremuloides) nest trees, as compared to lodgepole pine (Pinus contorta). Further research will help identify management implications for this species of concern in this high altitude forest surrounded by a shrub-steppe ecosystem.

Nesting Season Diet of Golden Eagles (Aquila chrysaetos) in Western Iran 
Arya Shafaeipour

I studied the diet of the Golden Eagle (Aquila chrysaetos) in western Iran by identifying food items in prey remains, pellets, and video recordings at seven nests during the 2011–2013 breeding seasons. Two methods were used to calculate diet composition: minimum number of individuals of each prey species and estimated biomass for prey items. I identified 316 prey items, which included five species of birds, four species of mammals, and two species of reptiles. Mammals made up the greatest proportion of the diet, 44.0% by frequency and 76.8% by biomass, and birds accounted for 43.7% of the diet by frequency and 17.7% by biomass. Cape hare (Lepus capensis), Chukar (Alectoris chukar), Common Magpie (Pica pica), large-toothed souslik (Spermophilus fulvus) and common fox (Vulpes vulpes) were the most important prey species. The percentage of mammals in the Golden Eagle’s diet in western Iran was lower than in North America, Scotland, the mountains of the Mediterranean, and across Europe and Asia.


Estimating Natal Origins of Migratory Juvenile Golden Eagles Using Stable Hydrogen Isotopes
Robert Domenech, Tim Pitz, Kathy Gray and Melanie Smith

We used stable isotope analysis to estimate the hydrogen national origin of juveniles of Aquila chrysaetos captured during fall migration along the front range of the Rocky Mountains in Montana, USA. We collect feather samples of 50 individuals under one year (juveniles) in many places of fall migration between 2004-2007. We analyze the radius of deuterium (δ 2 H f ) in the feathers showing results in parts per thousand [‰]. A model of simple linear regression was used to calibrate our isotope ratios obtained from migrant eagles with a base map for specific deuterium prey. This allowed us to make inferences about the place of native origin of juveniles of A. chrysaetos captured during the fall migration. Our analysis showed that the national origin stretched from the Brooks Range in Alaska to northern Montana. However, 66% (range 50-76%) of the individuals analyzed had its probable origin in areas located in Yukon and the Northwest Territories, Canada, and a small portion of eastern Alaska (-140 ≤ δ 2 H f ). We did not observe any difference in the dates of migratory path associated with sex or the latitude of the place of birth. Our study suggests that the stable isotope analysis can be a useful tool to link census and immigration data trends A. chrysaetos with its population status when considering multiple locations of census migration and wintering areas throughout North America.

Preening Behavior and Survival of Territorial Adult Golden Eagles with Backpack Satellite Transmitters
Dale W. Stahlecker, Terrell H. Johnson and Robert K. Murphy

We use backpack harnesses to attach satellite transmitters 55g and 100g (PTTs, its acronym in English) in seven territorial adults of Aquila chrysaetos during a study of the ecology of this species in southwestern North America. The percentage of time spent on grooming by four adult individuals, after 1-6 weeks of being fitted with PTTs, did not differ from time spent over the same period by four territorial adult individuals not equipped with PTTs. However, only two of the seven territorial eagles fitted with PTTs were not killed or their transmitters were removed in the first or second year after being appointed and one of them was apparently expelled from its territory. Our observations, though limited in number, suggest a deeper analysis of the possible negative impact of satellite emitters PTT type A. chrysaetos . We urge conducting collaborative meta-analysis to better understand how it affects the installation of satellite transmitters on the behavior and survival of A. chrysaetos long term.

Breeding Biology of the Upland Buzzard (Buteo hemilasius) on the Tibetan Plateau 
Wei Chen, Lichun Jiang, Zhangqiang You and Mao Chen

Ecology and conservation status of the populations of Upland Buzzard on the Tibetan plateau are poorly understood. We studied the reproductive biology of this species in 2014 in swamps height Zoige plateau located in southwest China, on the eastern edge of the Tibetan plateau. The start took place from early April to late May ( n  = 24). The average clutch size (± SD) was 3.13 (± 0.95, range 1-5 eggs). The average number of eggs hatched in the last visit was 2.54 (± 1.25, range 0-4). The failure rate was relatively low (20.8%), the main causes of nest failure of natural damage, human disturbance and predation. Compared to individuals B. hemilasius low altitudes, we study birds laid fewer eggs but apparently had a greater number of young survivors, suggesting that birds may be higher altitudes reproductive investing more energy in a smaller offspring to overcome the restrictions imposed by the time and limited resources high altitude environments.

Migratory Pathways, Timing, and Home Ranges of Southern Greater Yellowstone Osprey 
Bryan E. Bedrosian, Steven L. Cain, Susan Wolff and Derek J. Craighead

During the period 2010-2012 documented migrant and seasonal movements of 11 individuals Pandion haliaetus that breed or born in the Grand Teton National Park, Wyoming. We follow the movements of individuals of P. haliaetus with satellite telemetry transmitters through Argos, documenting a total of 13 fall migrations five spring migrations. The average starting dates for the fall were the September 19 and September 23 for adults and juveniles, respectively, and individuals traveled an average of 225 km / d. Individuals of P. haliaetus had dispersed wintering areas, usually around the Gulf of Mexico. The average starting date in the spring was April 2 adults and individuals traveled an average of 269 km / d. The adults showed an average home range of 176 and 199 ha, considering the minimum convex polygon of 95% for distributions of summer and winter, respectively. We documented a new migration route from the Rocky Mountains to Cuba through the Great Plains and Florida. Our data suggest that the wintering habitat of individuals of P. haliaetus that breed in the Northern Rocky Mountains is dispersed and that any disruption in breeding populations may be the result of changes in migration routes or distribution of summer.

Winter Roost Place Selection of Long-eared Owls in European Russia 
Tatiana Makarova and Alexander Sharikov

We investigate the use of roosts in winter by long-eared owl in an urban setting in southwestern Russia. Individuals A. otus prefi-laughed rest in conifers (93.7%, n  = 429), particularly in Picea abies (65%) and Pinus sylvestris (21%). Thuja occidentalis and deciduous trees were used infrequently by owls. Among the trees used as roosts, except P. abies , the number of owls in a particular roost was determined significantly by year, type and level of tree and tree foliage area. Intermediate areas and tree foliage nearest the trunk area were chosen by a greater number of owls that other levels and areas. The location of the roost in P. abies was close to half the tree trunk and close. Therefore, A. otus often he used their winter roosts in trees and specific locations within these trees had better quality caches, probably to ward off factors such as climate and anthropogenic disturbances.

Multiresistant Salmonella Serovar Typhimurium Monophasic in Wintering Red Kites (Milvus milvus) in Segovia, Central Spain
Guillermo Blanco

Wild birds that feed at landfills and dumps can purchase associated with decaying flesh and debris microorganisms and pathogens of cattle, and disperse over long distances during migration, with implications for public health and conservation wildlife. We evaluated the presence of Salmonella and antimicrobial resistance in fecal samples from individuals Milvus milvus feeding on a mixture of wild prey and carrion cattle during the winter in central Spain. The only isolated serotype was Salmonella enterica subspecies enterica serotype Typhimurium phase 4,5,12: i: -. These isolates were resistant to approximately half of the antimicrobials, including those that are typical of this serotype in pigs and their derivatives. Carrion pork and other feedlot cattle could be the source of infection with this serotype emerging zoonotic potential transmission resistant to multiple antibiotics, although other sources of infection such as contaminated water or wild prey are also possible. More research is needed to determine if the dumps and landfills can influence the spread of this and other serotypes in cattle and humans, and their impact on the health of individuals wintering M. milvus and other wildlife.


Do Raptors React to Ultraviolet Light?
W. Grainger Hunt, Christopher J.W. McClure and Taber D. Allison

Lead Paragraph
Birds are renowned for their excellent vision, including the sensitivity of many species to ultraviolet light (UV; Birkhead 2012). Bird color vision is mediated by four single-cone types, one of which houses SWS1 pigments that determine whether a species is sensitive to UV (<400 nm in wavelength) or only to longer wavelengths (reviewed by Hart 2001). Field observations led to the proposition that certain raptors might use the UV reflectance of vole urine to aid in hunting (Viitala et al. 1995, Koivula and Viitala 1999), although others have maintained that differences between UV reflectance of vole urine and underlying substrates were likely indistinguishable (Lind et al. 2013). Genetic studies by Odeen and Hastad (2003) suggested that raptors generally lacked UV-sensitivity, and most recently, sequencing of a Golden Eagle (Aquila chrysaetos) genome by Doyle et al. (2014) revealed genes indicating sensitivity to the violet spectrum and not to the near-ultraviolet part of the spectrum. In field tests of the efficacy of UV reflectance in reducing the incidence of raptor collisions with wind turbine blades, Young et al. (2003) found no effect of blades painted with UV reflective paint on mortality rates. A remaining question regarding the potential of UV light to deter raptors from entering hazardous areas was their possible sensitivity to projected, rather than reflected, UV light. Here we recount observations made during exploratory field tests of the potential of projected UV light to elicit an avoidance response in a small sample of Golden Eagles and other raptors.

Polygyny Leads to Disproportionate Recruitment in Urban Cooper’s Hawks (Accipiter cooperii)
Timothy G. Driscoll and Robert N. Rosenfield

Lead Paragraph
Excluding harriers (Circus spp.) and the Boreal Owl (Aegolius funereus), polygyny is rare in most species of raptors and more often occurs under conditions of food abundance and in rodent-eating birds of prey (Korpimäki 1988,Korpimäki and Hakkarainen 2012, Simmons et al. 1986, Rosenfield et al. 2007a). We genetically confirmed paternity of a male Cooper’s Hawk (Accipiter cooperii) in successful polygyny in a high density population in the city of Grand Forks, North Dakota, where the predominant prey for this species is birds (Rosenfield et al. 2007a, T. Driscoll unpubl. data). To our knowledge, ours was the first study to report polygyny in Cooper’s Hawks, and the first documentation of successful polygyny in Accipiter; that is, all three young fledged in each of two simultaneous nests in 2006. The male’s reproductive output may have been enhanced in this urban setting, whereas that of the females may have been compromised as each female’s output was below the average number of young fledged in successful nests in our urban population. The male’s collective production of six young from both nests exceeded by one the maximum brood size of all but one monogamous pair of Cooper’s Hawks in Grand Forks (Rosenfield et al. 2007a, T. Driscoll unpubl. data). Production of six young in one nest is rare among Cooper’s Hawk populations (Rosenfield et al. 2007a, Millsap et al. 2013).

No comments:

Post a comment