Lead poisoning occurs worldwide in populations of predatory birds, but exposure rates and population impacts are known only from regional studies. We evaluated the lead exposure of 1210 bald and golden eagles from 38 US states across North America, including 620 live eagles. We detected unexpectedly high frequencies of lead poisoning of eagles, both chronic (46 to 47% of bald and golden eagles, as measured in bone) and acute (27 to 33% of bald eagles and 7 to 35% of golden eagles, as measured in liver, blood, and feathers). Frequency of lead poisoning was influenced by age and, for bald eagles, by region and season. Continent-wide demographic modeling suggests that poisoning at this level suppresses population growth rates for bald eagles by 3.8% (95% confidence interval: 2.5%, 5.4%) and for golden eagles by 0.8% (0.7%, 0.9%). Lead poisoning is an underappreciated but important constraint on continent-wide populations of these iconic protected species.

AbstractIn the United States, the Bald and Golden Eagle Protection Act prohibits take of golden eagles (Aquila chrysaetos) unless authorized by permit, and stipulates that all permitted take must be sustainable. Golden eagles are unintentionally killed in conjunction with many lawful activities (e.g., electrocution on power poles, collision with wind turbines). Managers who issue permits for incidental take of golden eagles must determine allowable take levels and manage permitted take accordingly. To aid managers in making these decisions in the western United States, we used an integrated population model to obtain estimates of golden eagle vital rates and population size, and then used those estimates in a prescribed take level (PTL) model to estimate the allowable take level. Estimated mean annual survival rates for golden eagles ranged from 0.70 (95% credible interval = 0.66–0.74) for first‐year birds to 0.90 (0.88–0.91) for adults. Models suggested a high proportion of adult female golden eagles attempted to breed and breeding pairs fledged a mean of 0.53 (0.39–0.72) young annually. Population size in the coterminous western United States has averaged ~31,800 individuals for several decades, with λ = 1.0 (0.96–1.05). The PTL model estimated a median allowable take limit of ~2227 (708–4182) individuals annually given a management objective of maintaining a stable population. We estimate that take averaged 2572 out of 4373 (59%) deaths annually, based on a representative sample of transmitter‐tagged golden eagles. For the subset of golden eagles that were recovered and a cause of death determined, anthropogenic mortality accounted for an average of 74% of deaths after their first year; leading forms of take over all age classes were shooting (~670 per year), collisions (~611), electrocutions (~506), and poisoning (~427). Although observed take overlapped the credible interval of our allowable take estimate and the population overall has been stable, our findings indicate that additional take, unless mitigated for, may not be sustainable. Our analysis demonstrates the utility of the joint application of integrated population and prescribed take level models to management of incidental take of a protected species.

Resumen El empetrolado de las aves puede tener consecuencias importantes a nivel individual y poblacional. Aunque la mayoria de los ejemplos publicados sobre empetrolado se refieren a la exposicion a fuentes antropicas de hidrocarburos, el empetrolado puede ocurrir naturalmente. Describimos cuatro casos de empetrolado natural de siete pollos de Aquila chrysaetos asi como nuestra intervencion para mitigarlo. En todos los casos, el aceite en estas aves provino casi seguro de sus presas, en su mayoria ardillas terrestres (Otospermophilus beecheyi), aportadas por aguilas adultas en cantidades mayores de las que los polluelos podian consumir. Algunos pollos solo fueron empetrolados levemente. Otros fueron empetrolados tanto que la funcion de las plumas se vio comprometida a un nivel en el que, sin nuestra intervencion, la supervivencia de estos pollos de aguila seguramente hubiera sido afectada. Hasta donde sabemos, este es el primer informe publicado sobre empetrolado de rapaces como consecuencia de un sobre ...

Raptors are exposed to a wide variety of human-related mortality agents, and yet population-level effects are rarely quantified. Doing so requires modeling vital rates in the context of species life-history, behavior, and population dynamics theory. In this paper, we explore the details of such an analysis by focusing on the demography of a resident, tree-nesting population of golden eagles (Aquila chrysaetos) in the vicinity of an extensive (142 km2) windfarm in California. During 1994-2000, we tracked the fates of >250 radio-marked individuals of four life-stages and conducted five annual surveys of territory occupancy and reproduction. Collisions with wind turbines accounted for 41% of 88 uncensored fatalities, most of which were subadults and nonbreeding adults (floaters). A consistent overall male preponderance in the population meant that females were the limiting sex in this territorial, monogamous species. Estimates of potential population growth rate and associated variance indicated a stable breeding population, but one for which any further decrease in vital rates would require immigrant floaters to fill territory vacancies. Occupancy surveys 5 and 13 years later (2005 and 2013) showed that the nesting population remained intact, and no upward trend was apparent in the proportion of subadult eagles as pair members, a condition that would have suggested a deficit of adult replacements. However, the number of golden eagle pairs required to support windfarm mortality was large. We estimated that the entire annual reproductive output of 216-255 breeding pairs would have been necessary to support published estimates of 55-65 turbine blade-strike fatalities per year. Although the vital rates forming the basis for these calculations may have changed since the data were collected, our approach should be useful for gaining a clearer understanding of how anthropogenic mortality affects the health of raptor populations, particularly those species with delayed maturity and naturally low reproductive rates.

Renewable energy is expanding quickly with sometimes dramatic impacts to species and ecosystems. To understand the degree to which sensitive species may be impacted by renewable energy projects, it is informative to know how much space individuals use and how that space may overlap with planned development. We used global positioning system global system for mobile communications (GPS-GSM) telemetry to measure year-round movements of golden eagles (Aquila cluysaetos) from the Mojave Desert of California, USA. We estimated monthly space use with adaptive local convex hulls to identify the temporal and spatial scales at which eagles may encounter renewable energy projects in the Desert Renewable Energy Conservation Plan area. Mean size of home ranges was lowest and least variable from November through January and greatest in February March and May August. These monthly home range patterns coincided with seasonal variation in breeding ecology, habitat associations, and temperature. The expanded home ranges in hot summer months included movements to cooler, prey-dense, mountainous areas characterized by forest, grasslands, and scrublands. Breeding-season home ranges (October May) included more lowland semi-desert and rock vegetation. Overlap of eagle home ranges and focus areas for renewable energy development was greatest when eagle home ranges were smallest, during the breeding season. Golden eagles in the Mojave Desert used more space and a wider range of habitat types than expected and renewable energy projects could affect a larger section of the regional population than was previously thought. Published by Elsevier Ltd.

Abstract During 1987–89, we placed VHF transmitters and colored identification bands on 15 nestling Bald Eagles (Haliaeetus leucocephalus) in central Arizona to determine the direction and extent of their post-fledging migration. Thirteen of the juveniles fledged successfully, and one transmitter failed; 11 eagles survived the post-fledging, premigration period which ranged from 18 to 65 d (mean  =  44 d). One eagle was lost by trackers after departure, but 10 monitored eagles traveled north from 925 km to 1955 km before stopping for extended periods or until weather prevented further tracking. Habitats varied among stopping locations and included interior reservoirs and lakes, open ranchland, and the Pacific marine coast. Food at inland destinations included spawning fish (cutthroat trout [Salmo clarki]) and fish carrion (common carp [Cyprinus carpio] and white suckers [Catostomus commersoni]). At least nine of 13 fledged juveniles survived ≥1 yr (69%), and a minimum of six (46%) survived to breeding age.

We trapped and translocated golden eagles (Aquila chrysaetos) from the Channel Islands off the southern California coast between 1999 and 2003 in an ongoing effort to mitigate a catastrophic decline in three subspecies of island fox (Urocyon littoralis). As of August 2003, we had removed 31 (70%) of 44 known eagles from Santa Cruz and Santa Rosa Islands. Translocated eagles were released in areas of suitable habitat in northern California from 275–880 km from the islands. Eaglets removed from nests were either fostered into mainland golden eagle nests or hacked into the wild. Eleven of the released eagles (seven adults, three subadults, one juvenile) were tracked with combination satellite and conventional VHF transmitters to determine if they would return to the islands. The satellite transmitters operated for an average of 13.6 months (range 0–28). We obtained 1,568 satellite locations of class 3, 2, or 1 (est. accuracy of <150 – <1,000 m). Locations were plotted and analyzed with the geographic information system ArcGIS 8.0. Released birds ranged over areas of 1,366–256,413 km. The most proximal location obtained was 304 km NNE of Santa Cruz Island. Sensor data suggested that five eagles (45%) shed their transmitters or died within 1–7 months. Six birds were still alive and wearing their transmitters when transmissions ceased (5–28 months post-release). None of the radioed eagles returned to the islands during tracking and no banded golden eagles have subsequently been observed on the islands. Since the onset of eagle removal efforts, annual island fox survivorship on Santa Cruz Island has risen to near pre-decline levels. We conclude that translocation of golden eagles is an effective non-lethal method of reducing the island golden eagle population and their potential impact on island fox recovery.