Conserving wide-ranging animals requires knowledge about their year-round movements and resource use. Golden Eagles (Aquila chrysaetos) exhibit a wide range of movement patterns across North America. We combined tracking data from 571 Golden Eagles from multiple independent satellite-telemetry projects from North America to provide a comprehensive look at the magnitude and extent of these movements on a continental scale. We compared patterns of use relative to four alternative administrative and ecological mapping systems, namely Bird Conservation Regions (BCRs), U.S. administrative migratory bird flyways, Migratory Bird Joint Ventures, and Landscape Conservation Cooperatives. Our analyses suggested that eagles initially captured in eastern North America used space differently than those captured in western North America. Other groups of eagles that exhibited distinct patterns in space use included long-distance migrants from northern latitudes, and southwestern and Californian desert residents. There were also several groupings of eagles in the Intermountain West. Using this collaborative approach, we have identified large-scale movement patterns that may not have been possible with individual studies. These results will support landscape-scale conservation measures for Golden Eagles across North America.

Knowledge of dispersal from natal areas by pre-breeding-age Golden Eagles (Aquila chrysaetos) in North America is sparse, though crucial for conservation planning. During 2010–2015, we used satellite telemetry to document movement behavior of pre-breeding-age Golden Eagles from the Colorado Plateau and Southern Rocky Mountains of the southwestern U.S.A. Here we report on (1) 1st-yr dispersal timing, distances, strategies, and survival; (2) influences of age, sex, nest-mates, and area of origin; and (3) progressive distancing from natal nests and coinciding space use, including overlap between individuals' home ranges at the end of their 1st and 2nd yr. Our dataset included 293,960 GPS fixes from 66 Golden Eagles monitored through at least the onset of dispersal. All dispersed at age <1 yr. Most (66.7%) initiated dispersal during 16 September–21 November (median = 22 October, 191 d after median hatch date). We could assign each of 60 eagles to one of four 1st-yr dispersal categories based on maximum distance traveled from natal nests: short-distance (SD), generally <120 km (66.7% of eagles); moderate-distance (MD), 120–500 km (16.7%); long-distance (LD) >500 km (13.3%); and Other (3.3%). LDs dispersed at younger ages than SDs and were more likely to be from the arid half of our study area. First-year survival was significantly lower for LDs. Overlap of 95% kernel density home ranges at ages 12 and 24 mo was 42.2% (±6.4 SE) for 26 SDs and 26.5% (±9.5) for eight MDs. Our data indicate that, during at least their 1st and 2nd yr of life, most Golden Eagles from the Colorado Plateau and Southern Rocky Mountains remain within 120 km of their nests, where they experience high survival and are relatively settled by the end of their 1st yr. As such, these landscapes are key habitat for at least 1st- and 2nd-yr eagles as well as breeding pairs.

Spatial demographic models can help guide monitoring and management activities targeting at-risk species, even in cases where baseline data are lacking. Here, we provide an example of how site-specific changes in land use and anthropogenic stressors can be incorporated into a spatial demographic model to investigate effects on population dynamics of Golden Eagles (Aquila chrysaetos). Our study focused on a population of Golden Eagles exposed to risks associated with rapid increases in renewable energy development in southern California, U.S.A. We developed a spatially explicit, individual-based simulation model that integrated empirical data on demography of Golden Eagles with spatial data on the arrangement of nesting habitats, prey resources, and planned renewable energy development sites. Our model permitted simulated eagles of different stage-classes to disperse, establish home ranges, acquire prey resources, prospect for breeding sites, and reproduce. The distribution of nesting habitats, prey resources, and threats within each individual's home range influenced movement, reproduction, and survival. We used our model to explore potential effects of alternative disturbance scenarios, and proposed conservation strategies, on the future distribution and abundance of Golden Eagles in the study region. Results from our simulations suggest that probable increases in mortality associated with renewable energy infrastructure (e.g., collisions with wind turbines and vehicles, electrocution on power poles) could have negative consequences for population trajectories, but that site-specific conservation actions could reduce the magnitude of negative effects. Our study demonstrates the use of a flexible and expandable modeling framework to incorporate spatially dependent processes when determining relative effects of proposed management options to Golden Eagles and their habitats.

Conserving populations of long-lived birds of prey, characterized by a slow life-history (e.g., high survival and low reproductive output), requires a thorough understanding of how variation in their vital rates differentially affects population growth. Stochastic population modeling provides a framework for exploring variation in complex life histories to better understand how environmental and demographic variation within individual vital rates affects population dynamics. Specifically, we used life-stage simulation analysis (LSA) to identify those life-history characteristics that most affect population growth and are amenable to management actions. The Golden Eagle (Aquila chrysaetos) is a wide-ranging raptor of conservation concern, which has been adopted as a focal species for conservation planning. Golden Eagle population trends in western North America currently appear stable. Yet an expanding human footprint that may increase mortality stimulated our investigation into the ability of populations to sustain reduced survival. We fit mixed-effects models to published estimates of vital rates to estimate the mean and process variation of productivity (young fledged per pair) and survival for use in a LSA framework. As expected, breeding adult survival had the greatest relative effect on population growth, though productivity explained the most variation in growth. Based on perturbation analyses, we demonstrate that even minor reductions in breeding adult survival (<4.5%) caused otherwise stable populations to decline. Despite its importance, precise estimates of spatial and temporal variation in breeding adult survival are poorly documented. Importantly, we found that the ability for increases in reproductive output to compensate for decreased survival was very limited. To maintain stable populations, declines in survival >4% required increases in productivity that generally exceed the evolutionary potential for Golden Eagles. Our findings support the current U.S. Fish and Wildlife conservation strategy which mitigates eagle “take” via efforts to reduce mortality elsewhere.

Contaminant exposure is among the many threats to Golden Eagle (Aquila chrysaetos) populations throughout North America, particularly lead poisoning and anticoagulant rodenticides (AR). These threats may act in concert with others (e.g., lead poisoning and trauma associated with striking objects) to exacerbate risk. Golden Eagles are skilled hunters but also exploit scavenging opportunities, making them particularly susceptible to contaminant exposure from ingesting tissues of poisoned or shot animals. Lead poisoning has long been recognized as an important source of mortality for Golden Eagles throughout North America. More recently, ARs have been associated with both sublethal and lethal effects in raptor species worldwide. In this review, we examine the current state of knowledge for lead and AR exposure in Golden Eagles, drawing from the broader raptor contaminant ecology literature. We examine lead and AR sources within Golden Eagle habitats, exposure routes and toxicity, effects on individuals and populations, synergistic effects, and data and information needs. Continued research addressing data needs and information gaps will help with Golden Eagle conservation planning.

Avian electrocutions on power poles (hereafter, poles) are a global conservation concern, particularly for large-bodied species like Golden Eagles (Aquila chrysaetos). Retrofitting poles through increasing clearances (separation) between components, adding insulation to components, or adding redirection materials like perch discouragers reduces risk, but electrocutions may occur even on retrofitted poles. We evaluated 52 retrofitted poles where 56 birds, including 17 Golden Eagles, were electrocuted after retrofitting. We used burns on pole equipment and carcasses to identify precise pole-top locations where electrocutions occurred, and we identified three categories of retrofitting errors: product design, mitigation plan, and application. Product design errors (n = 9 poles, 6 Golden Eagles) occurred when products did not sufficiently cover energized equipment. Mitigation plan errors (n = 30 poles, 6 Golden Eagles) occurred when retrofitting plans did not include coverage of all energized components on a pole. Application errors (n = 13 poles, 5 Golden Eagles) occurred when the correct products were installed incorrectly. Retrofitting mistakes were identified in this study retroactively when avian electrocutions occurred on poles described as retrofitted. This is typical of how retrofitting mistakes are identified by the electric industry, which can lead to expensive duplicate efforts, and ongoing avian electrocutions. These can be avoided if retrofitting is done correctly initially. This study provides insight to electric utility personnel and wildlife managers interested in proactively evaluating the thoroughness of retrofitting, facilitating immediate identification and correction of retrofitting errors, increasing cost effectiveness, and reducing avian electrocution mortality.

The Golden Eagle (Aquila chrysaetos) has great religious importance to many indigenous North American peoples, including the Hopi Tribe and Navajo Nation of the southwestern United States. Hopi oral traditions indicate their ancestors harvested nestling Golden Eagles prior to the arrival of Europeans to the region, and this religious practice continues today. Despite contemporary conservation concern for Golden Eagles, no studies have evaluated potential negative effects of religious harvest on populations of this species. We conducted aerial and ground searches for Golden Eagle nesting territories on the Navajo Nation from 1996–2005, and monitored occupancy and reproductive rates of territories in three study areas: one area where Hopi annually harvested eaglets, and two areas without harvest. We analyzed 9 yr of data (1997–2005) using multi-season occupancy models and generalized linear mixed models to test for differences among study areas in occupancy dynamics, and production of early-season and fledging-age nestlings. We found no significant differences in probabilities of occupancy, persistence, or colonization of territories between study areas. Territories in harvest and control areas produced similar numbers of nestlings early in the season; however, significantly fewer (53%) reached fledging age in the harvested area, suggesting collection of nestlings led to locally depressed fledgling production. Given possible declining trends of Golden Eagle populations in the southwestern U.S., we recommend continued monitoring and more intensive demographic studies to better understand the effects of religious harvest on the population of Golden Eagles nesting on the Navajo Nation.

Wind energy development has expanded rapidly in the past decade, becoming a significant source of electricity, and a major element in a global strategy to reduce carbon emissions and the effects of climate change. Golden Eagles (Aquila chrysaetos) can collide with wind turbines, adding to the existing and substantial mortality from other anthropogenic sources. These collisions are a conservation concern, and they pose a legal risk to wind energy companies and potentially hamper development in areas where the range of Golden Eagle overlaps areas of high wind energy potential. The U.S. Fish and Wildlife Service, through the revised Eagle Rule and the Eagle Conservation Plan Guidance, has designed a mitigation strategy for eagle conservation that allows wind energy companies to obtain incidental take permits. However, the strategy is challenged by a lack of data supporting scientifically rigorous strategies to mitigate eagle take, where mitigation is defined as efforts to avoid and minimize take, and compensate for unavoidable take. We review the steps and options a wind developer can consider to mitigate predicted eagle collisions with wind turbines consistent with the U.S. Fish and Wildlife Service's revised Eagle Rule and Eagle Conservation Plan Guidance. Most of these options have limited or no scientific support and their effect on reducing risk of eagle collisions is unknown. We briefly describe approaches for evaluating technology intended to minimize eagle take and for developing options to offset unavoidable eagle take that are quantifiable and verifiable. Because estimates of Golden Eagle fatalities at many wind energy projects are low, research to evaluate mitigation measures needs to be coordinated and collaborative across multiple wind energy facilities to improve our ability to produce scientifically robust mitigation strategies. The impetus for these efforts is improving implementation and compliance with the revised Eagle Rule, but the results have benefits beyond Golden Eagles, for raptors and their ecological communities.

Golden Eagles (Aquila chrysaetos) are facing rapid environmental changes that may reduce the abundance and distribution of their prey in the western United States. Mitigation of negative effects depends in part on understanding Golden Eagle diet and the relationship between prey abundance and eagle reproduction. We documented reproduction and diet for Golden Eagles nesting in Wyoming's Bighorn Basin 2009–2015 and examined relationships between primary prey abundance and Golden Eagle diet breadth and reproductive rate. Annual Golden Eagle reproductive rate averaged 0.73 (range = 0.38–1.32) fledglings per occupied nesting territory. Cottontails (Sylvilagus spp.) dominated the diet in each year of the study, although cottontail abundance fluctuated markedly from year to year. The annual occurrence of cottontails in prey remains collected from nests ranged from 60.1% to 90.9% (frequency) and from 46% to 96% (biomass). Annual Golden Eagle diet breadth (Levins index) averaged 1.91 (frequency) and 1.98 (biomass). Both measures of annual diet breadth were negatively related to cottontail abundance. Annual eagle reproductive rate increased significantly as cottontail abundance increased (r² = 0.78, F_1,5 = 17.35, P = 0.009). Our results suggest that the abundance of cottontails was the critical factor influencing Golden Eagle reproduction in a given year during our study. To mitigate negative effects of environmental changes on the Golden Eagle population in the Bighorn Basin, we suggest maintaining or improving habitat conditions that support robust cottontail populations and improving conditions for potential alternative prey species where ecologically feasible and socially acceptable.

Detailed information on diets and predatory ecology of Golden Eagles (Aquila chrysaetos) is essential to prioritize prey species management and to develop landscape-specific conservation strategies, including mitigation of the effects of energy development across the western United States. We compiled published and unpublished data on Golden Eagle diets to (1) summarize available information on Golden Eagle diets in the western U.S., (2) compare diets among biogeographic provinces, and (3) discuss implications for conservation planning and future research. We analyzed 35 studies conducted during the breeding season at 45 locations from 1940–2015. Golden Eagle diet differed among western ecosystems. Lower dietary breadth was associated with desert and shrub-steppe ecosystems and higher breadth with mountain ranges and the Columbia Plateau. Correlations suggest that percentage of leporids in the diet is the factor driving overall diversity of prey and percentage of other prey groups in the diet of Golden Eagles. Leporids were the primary prey of breeding Golden Eagles in 78% of study areas, with sciurids reported as primary prey in 18% of study areas. During the nonbreeding season, Golden Eagles were most frequently recorded feeding on leporids and carrion. Golden Eagles can be described as both generalist and opportunistic predators; they can feed on a wide range of prey species but most frequently feed on abundant medium-sized prey species in a given habitat. Spatial variations in Golden Eagle diet likely reflect regional differences in prey community, whereas temporal trends likely reflect responses to long-term change in prey populations. Evidence suggests dietary shifts from traditional (leporid) prey can have adverse effects on Golden Eagle reproductive rates. Land management practices that support or restore shrub-steppe ecosystem diversity should benefit Golden Eagles. More information is needed on nonbreeding-season diet to determine what food resources, such as carrion, are important for overwinter survival.

Elucidating the genetic structure and ascertaining the natal origin of Golden Eagles (Aquila chrysaetos) are challenging for a number of reasons, including the lack of highly reproducible, variant genetic loci. Here, we developed a new high-quality Golden Eagle genome reference to serve as a computational atlas for future genetic investigations. We then generated unique genetic resources for the Golden Eagle by performing low-coverage genomic sequencing for 32 individuals ranging from Alaska to southern New Mexico and California to Nebraska. By aligning the reads from these 32 individuals to our Golden Eagle reference genome, we detected approximately 900,000 population variants in the form of Single Nucleotide Polymorphisms (SNPs). Using linkage disequilibrium and other quality filters, we next derived a set of 30,006 SNPs that were used to cluster our samples into three genetic groups. Although additional work is needed to fully characterize these loci, we provide a high-quality Golden Eagle genome reference and a comprehensive set of genetic markers for the conservation and management of Golden Eagles. Additionally, with a more comprehensive Golden Eagle genome assembly and associated transcriptomes, it is now possible to target specific genes or other biologically relevant regions for evaluating the effects of many anthropogenic stressors on Golden Eagle survival.

Clearly defined terms are essential for reporting and understanding research findings, and inconsistent terminology can complicate efforts to compare findings from different studies. In this article, we reiterate and clarify recommended terms for describing Golden Eagle (Aquila chrysaetos) territory occupancy and reproduction. Several authors have provided recommendations for reporting data on raptor reproduction, but our literature review showed that authors continue to use different, often ambiguous and undefined, terms. The inconsistent use of terminology by researchers has been continued and expanded by lawmakers, regulators, and managers, perpetuating confusion. We recommend that authors clearly define and reference all terminology that they use, and we caution against use of the term “active” to describe a nest or nesting territory, because it is tainted with a history of inconsistent use. We provide a glossary of recommended terms for Golden Eagles and other large, long-lived raptors.