Adult Eagles Research Articles

Different migration patterns of Wahlberg's eagles Hieraaetus wahlbergi across Africa

Intra‐Africa movements of most African migratory birds remain an enigma. We describe the migrations of Wahlberg's eagle Hieraaetus wahlbergi using GPS‐GSM transmitters on adult eagles in their South African (n = 3) and Kenyan (n = 7) breeding areas between 2018 and 2022. The dataset included 57 migratory tracks, 29 post‐breeding and 28 pre‐breeding. We found long‐distance migrants (LDMs; from South Africa) and short‐distance migrants (SDMs; from Kenya) using common non‐breeding areas centered in the Sudans and Central African Republic. The timing of annual phases was similar, but LDMs departed on their pre‐breeding migration on average later than SDMs (13 August versus 31 July) and arrived later on their breeding grounds (13 September versus 10 August). Conversely, the average departure date on the post‐breeding migration was 4 April for SDM and 23 March for LDMs. LDMs spent significantly less time of the year than SDMs on breeding grounds (44 versus 57%), and slightly but not significantly more time (40 versus 38%) on non‐breeding areas. The post‐breeding migration distance was on average 3413.9 ± 170.9 km for LDMs and 491.9 ± 158.5 km for SDMs. At non‐breeding areas, LDMs reached more northerly latitudes than SDMs, increasing the pre‐breeding migration distance to 4495.9 ± 372.5 km for LDMs versus 1701.9 ± 167.3 for SDMs. Daily flight distances back to the breeding areas averaged 153.4 ± 130.3 km for LDMs and 167.4 ± 122.3 km for SDMs and to non‐breeding areas were shorter for SDMs (124.8 ± 113.0 km) than LDMs (178.0 ± 134.4 km). Migration speed was similar across populations and for pre‐ and post‐breeding migrations. LDMs used more stopover days than SDMs. We conclude that Wahlberg's eagles from different parts of Africa have adapted their migration to differences in timing of the breeding season, distance of travel, and resources in the landscapes encountered during migration.

Growth of a nestling Little Eagle Hieraaetus morphnoides, with comments on rescue of pre-fledglings

A nestling Little Eagle Hieraaetus morphnoides was photographed and videoed from age 3 weeks until prematurely fledged at 8 weeks near Emmaville, New South Wales, during November–December 2023. This visual record, with notes, of physical and behavioural development supplements descriptions and the few earlier photographs of age-related growth stages of nestlings of this species. The adult Eagles tolerated observation on the ground from ~70 m away, without adverse effects on the breeding event. Brief descriptions of parental behaviour at these weekly stages, and at the incubation and hatching stages, are included. A predator killed the pre-fledged but feathered eaglet after an overnight storm blew the eaglet to the ground before it could fly. Rescue of such grounded fledglings is discussed.

Food Habits of the Mountain Hawk-Eagle (Nisaetus nipalensis orientalis) During the Nesting Period in Japan

ABSTRACT The Mountain Hawk Eagle (Nisaetus nipalensis orientalis) is classified as endangered in Japan and poorly studied throughout its range. We assessed prey fed to a nestling between hatching and fledging (16 April to 31 July) in central Japan. We used a time lapse camera to record prey deliveries and facilitate prey identification, and we estimated prey biomass and energy content across the nesting season. Of 140 prey items delivered to the single nestling, 65 (46.4%) were of five species of snake, 50 (35.7%) were of nine species of birds, 24 (17.1%) were of seven species of mammals, and one was unknown. The diurnal feeding rhythm showed a peak in prey deliveries at midday; all three classes of prey were delivered at various times of the day in a balanced manner. Snakes were especially prominent in the early stages of the brooding period, but diet shifted toward young birds and mammals in the latter half of the season when the prey species' young had become independent of their parents. Snakes made up the greatest percentage of biomass delivered, followed by mammals and then birds. However, mammals provided more energy per g of prey mass than birds and snakes. The adult eagles relied on large snakes awakened from hibernation in early spring, when prey was scarce, and then shifted to mammals with higher energy value during the peak growth period of the eaglet. An additional 233 prey remains collected from 31 other Mountain Hawk-Eagle nests comprised 20 species of birds and 10 species of mammals, and several unidentified snakes. Pooling results, we identified five species of snakes, 24 species of birds, and 14 species of mammals. These results add to the knowledge of the hawk-eagle's diet and will help to inform management of the species.

Space–time home‐range estimates and resource selection for the Critically Endangered Philippine Eagle on Mindanao

Quantifying home‐range size and habitat resource selection are important elements in wildlife ecology and are useful for informing conservation action. Many home‐range estimators and resource selection functions are currently in use. However, both methods are fraught with analytical issues inherent within autocorrelated movement data from irregular sampling and interpretation of resource selection model parameters to inform conservation management. Here, we apply satellite remote sensing technologies to provide updated estimates of home‐range size and first estimates of fine‐scale resource selection for six adult Philippine Eagles Pithecophaga jefferyi using a space–time autocorrelated kernel density estimate (AKDE) home‐range estimator and non‐parametric resource selection functions. All six adult Eagles showed distinct site fidelity, with continuous range residency between 2 and 18 km, 1 month after tagging. The space–time AKDE home‐range estimators had a median 95% home‐range size = 68 km2 (95% confidence interval (95% CI) 62–74 km2, range: 39–161 km2), with the median 50% core range size = 13 km2 (95% CI 11–14 km2, range 9–33 km2). From the resource selection functions, all adult Philippine Eagles used habitat high in photosynthetic leaf and canopy structure but avoided areas of old‐growth biomass and denser areas of vegetation. This is possibly due to foraging forays into secondary forest and fragmented agricultural areas away from nesting sites. For the first time, we determine two important fine‐scale spatial processes for this Critically Endangered raptor that can help in directing conservation management. Rather than employing traditional home‐range estimators and resource selection functions, we recommend that analysts consider space–time approaches and non‐parametric resource selection functions to animal movement data to explore fully space–time and resource selection.

Human Persecution is An Important Threat to the Conservation of the Endangered Black-and-Chestnut Eagle in Northern Andes

Background and Research Aims The Black-and-chestnut Eagle ( Spizaetus isidori) has a total population of fewer than 1000 adult individuals, and is categorized as Endangered at the global level. The northern Andes (Ecuador and Colombia) represent one of the last population strongholds of the species. In this study, we analyzed human persecution of the Black-and-chestnut Eagle as retaliation or as a preventive measure against poultry predation, as well as other threats that have affected the species in this geographical region between 2000 and 2022. Methods In order to understand the human persecution and other threats faced by the Black-and-chestnut Eagle in the northern Andes, we compiled records of immature and adult individuals of the species that had been shot, captured, or had presented evidence of any other affectations during the last 23 years. Results We found a total of 96 Black-and-chestnut Eagles affected by different threats. Human persecution of the species to prevent poultry predation was the motive in 81% (46 of 57) of the cases of shot eagles, 67% (10 of 15) of those captured illegally, 30% (3 of 10) of those in which the cause of affectation was undetermined and for one individual that had been stabbed. Immature eagles were more affected than adult eagles by human persecution. Black-and-chestnut Eagles were also affected by electrocution, illegal trafficking and collision with vehicle. Conclusion Human persecution as retaliation or as a preventive measure against poultry predation is an important threat to the conservation of the Black-and-chestnut Eagle in northern Andes. Implications for Conservation Strict application of laws at human persecution sites, identification and monitoring of areas with high risk of human-eagle conflict, development of environmental educational programs, strengthening of the technical capacities of rural communities, maintaining or even increasing forest cover, and reducing the exposure of poultry by using enclosures are key for Black-and-chestnut Eagle conservation in the northern Andes.

Новые данные о гнездовании беркута в бассейне реки Бердь, Новосибирская область, Россия

Новые данные о гнездовании беркута в бассейне реки Бердь, Новосибирская область, Россия

Анализ зарегистрированных причин смерти взрослых орлов в Грузии в 1973–2022 годы

Since 1973, the author has been conducting a complex study of birds in Georgia. Particular attention was paid to identifying threats and limiting factors, determining the extent and causes of death of all raptors, including eagles. All known cases were registered and, if possible, the causes were determined. In addition to the materials collected by the author together with assistants, for the collecting of statistical data regarding raptor mortality (including eagles), in 1978–1985 and in 1990–1991 special questionnaires were prepared and distributed to all regions, autonomous republics and districts of Georgia, to regional inspectors of regional branches of the former State Nature Conservation Committee, employees of the former Department of Nature Reserves and Hunting Industry of Georgia, stuff of the former Georgian Society of hunters, regional branches of hunters and falconers societies, zoologists and conservationists working in nature reserves, universities, nature history museums, as well as to local amateur naturalists, birdwatchers and school teachers. More than 8700 copies of questionnaires were distributed. Appeals to participate in the counting along with instructions were published in local newspapers and distributed via mass-media (radio, TV). As a result, about 520 responses were received, including detailed information on number of raptors killed by poachers, electrocuted on power lines, trapped by falconers, poisoned by chemicals, etc., altogether giving data on more than 160 death cases of nine eagle species. That was a great help for better understanding of threats and limiting factors. The total number of adult eagles’ deaths recorded in Georgia in 1973–2022 was 441: 118 in 1973–1980, 171 in 1981–1990, 69 in 1991–2000, 56 in 2001–2011, and 27 in 2012–2022. At least 362 of recorded mortality cases, or approximately 82% of all, occurred during the autumn migration, which coincides with the hunting season in Georgia, while 27 cases (6.12%) were recorded during spring passages, 28 (6.35%) cases – during wintering, and 24 (5.44%) cases – during breeding seasons. The main cause of death for adult eagles recorded in Georgia during study has been shooting – 296 cases for 9 eagle species, which is more than 67% of the total number of registered cases. Other recorded causes of mortality were the following: death on electricity cables due to electric shock (17 cases for 4 species), trapping and killing (5 cases for 2 species), death in traps with meat baits (5 cases for 2 species), death due of poisoning at poisoned meat baits (4 cases for 2 species), collisions with technical constructions (4 cases for 2 species), death on garbage damps due of poisoning (2 cases for 1 species), victims of prey (1 cases for 1 species), collisions with vehicles (1 cases for 1 species), unidentified reasons (106 cases for 7 species). There is no doubt that the shooting was the cause of the eagles’ deaths in those cases when it was not possible to accurately determine its cause. More detailed summarized data on distribution of registered mortality cases of adult eagles by seasons of years as well as by regions of Georgia are presented, analyzed, and discussed. Human persecution, especially illegal shooting, should be considered as a basic threat to raptors in Georgia, including all eagle species. The highest level of illegal eagle shooting in Georgia was recorded at Black Sea coastlands, in western part of Kolkheti Lowland, in river valleys, in suburbs of large cities, and in some other areas. If we compare the scale and causes of the eagle mortality in Georgia in different decades, then in general it should be noted that in recent years there has been a slight decrease in the number of shootings. Nevertheless, despite the legislative protection of all species of birds of prey in Georgia, shooting is still the main threat.There are no recent data on raptor protection status from some regions of Georgia annexed by Russia – Abkhazia (from 1993) and South Ossetia (from 2008). According to the available information from these regions, the situation there is alarming. To improve the situation with the protection of eagles in Georgia, as well as for all other raptor species, it is necessary to conduct extensive educational programs among all segments of the population, primarily among hunters.

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

Individual variability in space use near power lines by a long-lived territorial raptor.

Evaluating species responses to anthropogenic infrastructures and other habitat changes is often used to assess environmental impacts and to guide conservation actions. However, such studies are generally carried out at the population level, disregarding inter‐individual variability. Here, we investigate population‐ and individual‐level responses toward power lines of a territorial raptor, the Bonelli's eagle Aquila fasciata. We used GPS‐PTT tracking data of 17 adult eagles to model space use as a function of distance to transmission and distribution lines, while accounting for other habitat features known to affect this species. At population level, eagles increased the intensity of space use in the proximity of power lines (up to 1,000 m), suggesting an attraction effect. At individual level, some eagles shared the general population attraction pattern, while others showed reduced intensity of space use in the proximity of power lines. These differential responses were unrelated to the sex of individuals, but were affected by the characteristics of the power grid, with a tendency for apparent attraction to be associated with individuals occupying home ranges with a denser network of transmission lines and transmission pylons. However, the study could not rule out the operation of other potentially influential factors, such as individual idiosyncrasies, the spatial distribution of prey availability, and the availability of natural perches and nesting sites. Overall, these results suggest that power lines may drive different behaviors and have differential impacts across individuals, with those attracted to the proximity of power lines potentially facing increased risk of mortality through electrocution and collision, and those avoiding power lines being potentially subject to exclusion effects. More generally, our results reinforce the need to understand individual variability when assessing and mitigating impacts of anthropogenic infrastructures.

Using drones to reduce human disturbance while monitoring breeding status of an endangered raptor

AbstractIn birds, obtaining information related to nest occupancy, offspring status or breeding success is essential for population monitoring, particularly for species of conservation concern. Traditionally, nest monitoring demands a lot of time and effort in order to gather accurate information and avoiding nest disturbance. Instead, Unmanned Aerial Vehicles (UAVs, hereafter drones) present an alternative to traditional methods, but few studies have been done measuring their influence on birds’ behavior and reproductive success. We addressed the utility of drones equipped with an on‐board camera in examining nesting status of the endangered Chaco Eagle Buteogallus coronatus in semiarid environments of central Argentina, as well as the degree of disturbance of drone flights to individuals. We performed 76 drone flights at 41 Chaco Eagle nests registering flight duration, tree height, nest relative height and pilot proximity to nest. Of those, 38 flights were done over occupied nests where we recorded adult behavior. Before drone took off, most adult eagles remained in the nests or in the surroundings (<100 m away), particularly during the incubation period and in tall trees. During drone flights, only one adult flew as a response to drone flights. The rest of them remained vigilant or emitted alarm calls while incubating or perched on the nest platform. No attack toward drones was registered. The use of drones for monitoring Chaco Eagle’s nests significantly reduced levels of disturbance when compared with traditional methods where all adults flew away during climbing. Additionally, this method was almost three times faster in comparison to traditional climbing (performed at the end of the reproductive season) and had no negative effects on reproductive success of Chaco Eagles. Although responses to drones could be species‐specific, our results encourage researchers to consider and test the use of drones as a less disturbing and rapid method to monitor breeding raptor populations.

Novel step selection analyses on energy landscapes reveal how linear features alter migrations of soaring birds.

Human modification of landscapes includes extensive addition of linear features, such as roads and transmission lines. These can alter animal movement and space use and affect the intensity of interactions among species, including predation and competition. Effects of linear features on animal movement have seen relatively little research in avian systems, despite ample evidence of their effects in mammalian systems and that some types of linear features, including both roads and transmission lines, are substantial sources of mortality. Here, we used satellite telemetry combined with step selection functions designed to explicitly incorporate the energy landscape (el-SSFs) to investigate the effects of linear features and habitat on movements and space use of a large soaring bird, the golden eagle Aquila chrysaetos, during migration. Our sample consisted of 32 adult eagles tracked for 45 spring and 39 fall migrations from 2014 to 2017. Fitted el-SSFs indicated eagles had a strong general preference for south-facing slopes, where thermal uplift develops predictably, and that these areas are likely important aspects of migratory pathways. el-SSFs also provided evidence that roads and railroads affected movement during both spring and fall migrations, but eagles selected areas near roads to a greater degree in spring compared to fall and at higher latitudes compared to lower latitudes. During spring, time spent near linear features often occurred during slower-paced or stopover movements, perhaps in part to access carrion produced by vehicle collisions. Regardless of the behavioural mechanism of selection, use of these features could expose eagles and other soaring species to elevated risk via collision with vehicles and/or transmission lines. Linear features have previously been documented to affect the ecology of terrestrial species (e.g. large mammals) by modifying individuals' movement patterns; our work shows that these effects on movement extend to avian taxa.

Ranging behaviour of Long-crested Eagles Lophaetus occipitalis in human-modified landscapes of KwaZulu-Natal, South Africa

The ranging behaviour of raptors in human-altered environments, such as agricultural and suburban landscapes, is becoming increasingly important for conservationists in the context of unprecedented high rates of anthropogenic land use change. We studied the movement ecology of adult Long-crested Eagles Lophaetus occipitalis fitted with geographic positioning system transmitters in an agricultural landscape in KwaZulu-Natal Province, South Africa. Mean home ranges (± SD) of males and females estimated using the autocorrelated kernel density estimator (AKDE) method were 608 ± 552 ha (n = 5) and 664 ± 844 ha (n = 4), respectively. Core areas (KDEhref 50%) were estimated as 80 ± 38 ha and 39 ± 20 ha for males and females, respectively. We also recorded exploratory behaviour (in the form of long excursions) in two of the birds, of up to 49 km from the centre of their home range. The relatively small home ranges reported in this study are suggestive of productive foraging habitats whereby Long-crested Eagles can meet their energy requirements without having to travel long distances to obtain resources. Consistent with predictions, non-breeding male and female Long-crested Eagles showed similar ranging behaviour, which includes occasional exploratory behaviour.

Collision Avoidance by Wintering Bald Eagles Crossing a Transmission Line

Collision with electric lines is a global conservation concern for many birds but raptor species are generally thought to have a low risk of line collision. Collision risk at electric lines is not well understood for Bald Eagles (Haliaeetus leucocephalus), with only incidental reports of collisions in the literature. Line collisions reported for Bald Eagles predominantly occur where lines intersect movement corridors around foraging, roosting, or nesting areas. During five winters from 2014 to 2018, we monitored 602 Bald Eagle crossings of a 230/500-kV transmission line at the Delaware River to determine collision risk. Eagles successfully crossed the line by flying predominantly below the wire zone. There was no difference in flight heights for immature or adult eagles crossing the line. Wire-marking protocols within the electric industry are primarily focused on marking the top plane of wires to alert birds flying above the wires. Additional development of wire-marking options for energized conductors could further reduce collision risk for eagles and other bird species flying below wires. Overall, collision risk appears low for Bald Eagles making localized movements across transmission lines.

Ecology of the Golden Eagle in Mongolia, Part 1: Breeding Distribution and Nest-Site Descriptions

During seven expeditions across Mongolia, we found 40 Golden Eagle (Aquila chrysaetos) breeding territories with eggs or young. At 20 other locations, we either found old eagle nests with Golden Eagle feathers or saw adult eagles but found no eggs or young. Golden Eagles nested in all but the driest portions of the Gobi Desert and the easternmost grasslands. Nearly all pairs had alternate nests. Of 53 nests used, 60% were on cliff ledges as is typical around the world. However, 19% were on the ground or at other sites that were easily accessible to canid predators, with the most vulnerable nests small and seldom or never reused. The most unusual nests included one atop a conical basalt peak, one on relatively flat ground among tall boulders, four on steep hillsides, one on almost flat ground amid rocky protrusions, and three on cliff tops. Where tall cliffs with many ledges were available, the eagles nested at least 7 m above the ground. Nest construction materials were often unusual and included trash, patches of large mammal hides, paper money, and clothing.

Eagle visitation rates to carrion in a winter scavenging guild

ABSTRACTUnderstanding the behavioral ecology of species of conservation concern can help to inform better management. During winters 2011 through 2017, we placed camera traps at stations baited with carrion to investigate characteristics of winter scavenging by golden eagles (Aquila chrysaetos) and bald eagles (Haliaeetus leucocephalus) in eastern Washington and Oregon, USA. Our objectives were to better understand exposure risk of individual eagles to lead contaminants and evaluate factors that affect eagle visitation to carrion to inform measures that reduce lead exposure. We studied photo sequences from 108 traps ( = 2,725 ± 306 [SE] images/trap) and used plumage and physical characteristics to track visitation of 183 individual golden eagles and 90 bald eagles at deer (Odocoileus spp.) carrion until it was totally consumed. At least 1 eagle visited 76% of traps ( = 2.5 ± 0.3 unique eagles/trap). On average, an eagle visited a trap 3.4 ± 0.2 times (range = 1–19 visits) over 1.9 ± 0.1 days (range = 1–9 days). We used general linear mixed models to identify influences on number of eagle visits and pooled visit duration. Individual golden eagles visited carrion about 25% more often and 50% longer than bald eagles, and individual juvenile eagles visited carrion more often and longer than immature and adult eagles. On average, an eagle made an additional visit to carrion for every golden eagle that came to the same trap. Eagles spent less time at offal ( = 26.2 ± 6.4 min) than at a whole carcass ( = 92.9 ± 7.5 min), and understory vegetation immediately surrounding carrion was associated with a 30% reduction in visitation time. In the Pacific Northwest during winter, adult and juvenile golden eagles, by virtue of their abundance and visitation to carrion compared to the immature age class and bald eagles of all ages, have the highest potential for exposure to anthropogenic effects from carrion visitation. Concealment of offal piles in vegetation may reduce, but not eliminate, eagle use because of competing scavengers that expose carrion locations. We found no evidence that carrion proximity to nearest known nests, topography, or snow cover affect visitation by eagles. Thus, short of using alternative ammunition to lead, we recommend burial or removal of offal from hunter‐killed ungulates. © 2019 The Wildlife Society.

Using Motion-Activated Trail Cameras to Study Diet and Productivity of Cliff-Nesting Golden Eagles

Studies of cliff-nesting raptors can be challenging because direct observations of nest contents are difficult. Our goals were to develop a protocol for installing motion-activated trail cameras at Golden Eagle (Aquila chrysaetos) nests to record diet information and productivity, and to estimate prey detection probability using different diet study methods. In 2014 and 2015, we installed cameras at 12 Golden Eagle nests with 18–42-d-old nestlings. Following installation, we monitored adult behavior using direct observation and post-installation image review. At two nests, adult eagles did not return to nests or exhibited behaviors suggesting avoidance of the cameras, but returned to the nests after cameras were removed. We visited the 10 remaining nests every 4 d to collect prey remains and pellets to generate prey-specific detection estimates for both images, and prey remains and pellets. Compared to inspection of prey remains and pellets, cameras recorded twice the number of prey (622 vs. 316), were more likely to detect the smallest and largest prey, and cost half as much. Cameras recorded productivity, fledging dates, and in one case, a nestling death. Trail cameras may be a reliable and cost-effective option to address clearly defined research goals and obtain required information about eagle behavior and nest contents. However, cameras should be used judiciously because installation creates a persistent manipulation at the nest. Camera appearance should be minimized, and post-installation monitoring that allows for timely responses to nest-avoidance behavior by adult eagles is important to prevent adverse effects on nesting success.

Using web-sourced photography to explore the diet of a declining African raptor, the Martial Eagle (Polemaetus bellicosus)

ABSTRACTUnderstanding a species’ diet can be critical for effective conservation. While several traditional methods for assessing raptor diet exist, many pose inherit biases and often require extensive fieldwork that can limit sample sizes and the geographic scope of studies. This is especially true for species that nest at low densities (e.g., large eagles). Recently, several studies have demonstrated the value of web-sourced photographs in tackling ecological and evolutionary questions. Specialized software (e.g., MORPHIC) has been developed to systematically extract Google Images for this purpose. We used this approach to explore the diet of Martial Eagles (Polemaetus bellicosus). A shortage of prey is one of the proposed hypotheses for recent population declines across their range. Of the 4,872 photographs selected by MORPHIC, 254 were usable (5%). Birds, mammals, and reptiles each contributed similarly to overall identified prey. Helmeted Guineafowl (Numida meleagris) were the most important bird prey identified (12% of overall prey). The 4 most important mammalian prey species were Thompson’s gazelle (Eudorcas thomsonii; 5%), impala (Aepyceros melampus; 4%), common duiker (Sylvicapra grimmia; 4%), and banded mongoose (Mungos mungo; 4%). Reptile prey was dominated by monitor lizards (Varanus spp.; 21%). Prey class proportions differed significantly by regions with mammalian prey being more common in eastern Africa and reptile prey being more common in southern Africa. Within South Africa, reptile prey proportion was greater in the east than in the west. These corroborate existing prey composition studies. Prey composition differed between age classes, with adult eagles preying on more birds than non-adults. There was no significant difference in the average estimated prey weight by eagle age or feeding position (ground, perched, or flying). Our results suggest that this approach may offer a useful method to explore the diet for raptor species that are well photographed across their range, at minimal cost and research effort.

Observations on the roosting behaviour of adult male Golden Eagles from satellite telemetry

ABSTRACT The roosting behaviour of two adult male Golden Eagles Aquila chrysaetos was studied using GPS satellite tags. One eagle (tag 816) used 120 different roost sites over two years and the other (tag 991) more than 87 roosts over one year. These numbers of roost sites were substantially greater than expected from previous field-based studies. Around 70% of the roost sites were used on only one night and such roosts accounted for 17–25% of roosting behaviour. Seven roosts that were used for more than ten nights each (multi-use roosts) were located for one bird and five for the other. Roosts that were used on only one night tended to be used more than expected on evenings when winds were light (<5 ms-1), while multi-use roosts were used more than expected on evenings with strong winds (>10 ms-1). Hence, eagles appear to select more-sheltered, multi-use roost sites during strong winds.

Migration corridors of adult Golden Eagles originating in northwestern North America.

There has been increasing concern for Golden Eagle (Aquila chrysaetos) populations in North America due to current and future projections of mortality risk and habitat loss from anthropogenic sources. Identification of high-use movement corridors and bottlenecks for the migratory portion of the eagle population in western North America is an important first step to help habitat conservation and management efforts to reduce the risk of eagle mortality. We used dynamic Brownian Bridge movement models to estimate utilization distributions of adult eagles migrating across the western North America and identified high-use areas by calculating the overlap of individuals on population and regional levels. On a population level, the Rocky Mountain Front from east-central British Columbia to central Montana and southwestern Yukon encompassed the most used migration corridors with our study extent for both spring and fall. Regional analysis on a 100 x 200 km scale revealed additional moderate and high-level use corridors in the central British Columbia plateaus. Eagles were more dispersed in the spring until their routes converged in southern Alberta. High-use fall corridors extended farther south into central Wyoming. Knowledge of these high-use areas can aid in conservation and site planning to help maintain and enhance migratory Golden Eagle populations in western North America.

Parental Care of the Endangered Chaco Eagle (Buteogallus coronatus) in Central Argentina

Sexual differences in parental care investment may affect individual survival or performance, and also demography. We investigated parental-care behavior of the endangered Chaco Eagle (Buteogallus coronatus) to evaluate implications for population conservation in semiarid habitats of central Argentina. From 2004 to 2012, we monitored three breeding attempts using video recording (275 hr) during the incubation period, and nine pairs during the nestling-rearing period by means of video recording (1087 hr) and focal observations at nests (232 hr). Chaco Eagles showed a strong division of parental care by sex. Females contributed significantly more than males to incubation, shading/brooding, and feeding of the nestling, whereas males provided prey to females during incubation and to nestlings during the early nestling-rearing period. Foraging males, which spend more time away from the nest, may be more exposed to anthropogenic activities and negative interactions with humans. If males are more vulnerable to such effects, this could decrease the survival of breeding males and potentially increase the recruitment of immature males to the breeding population. In this event, the ability of the inexperienced immature males that replace the adult eagles to cope with the food and care demands of the mate and offspring is critical for ensuring Chaco Eagle population maintenance.