In 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.
Data on natal dispersal distances (NDDs) of golden eagle Aquila chrysaetos in North America are needed to define local area populations and inform decisions authorizing take (i.e., injury, death, or disturbance) of the species via federal permit. Sixteen golden eagles (6 males, 10 females) tagged with satellite transmitters as ∼8-wk-old nestlings in the southwestern United States during 2010–2013 dispersed a mean of 55.3 km (SD = 29.7, median = 64.5), either 1) between their natal nest sites and nests where they first bred (n = 3 females, all subadults, i.e., in their fourth year of life), or 2) between natal sites and where they permanently settled as adults at least in their fifth year of life, but did not necessarily breed (i.e., exhibiting only gross natal dispersal). On average, females dispersed about 50% farther than males; mean NDD of males and females was 41.2 km (90% credible interval = 11.1–75.2) and 63.8 km (44.8–82.6), respectively. Median NDD of males and females was 41.5 and 65.8 km, respectively; in a Bayesian framework, the estimated difference in posterior median distributions of male and female NDDs was 22.2 km (−15.7 to 57.3; P ≠ 0 = 0.89), tentatively indicating that NDD of golden eagles in our study area may be female biased. Although our findings are based on a relatively small data set including both effective and gross natal dispersal records, they represent the first comparison of NDD between sexes of golden eagle in North America and the first published records on the continent of the species' NDD based on telemetry methods. More work is needed to validate whether golden eagle NDD in at least some regions of North America is female biased, which could have important implications for authorizing take of the species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.