The U.S. Fish and Wildlife Service has a long tradition of scientific excellence and always uses the best-available science to inform its work to conserve fish, wildlife, plants, and their habitat for the benefit of the American public.
Created in 1903 by President Theodore Roosevelt, today's National Wildlife Refuge System protects habitats and wildlife across the country, from the Alaskan tundra to subtropical wetlands. Managed by the U.S. Fish and Wildlife Service, the Refuge System's 560-plus refuges cover more than 150 million acres and protect nearly 1,400 species of birds, mammals, reptiles, amphibians, and fish.
While national wildlife refuges were created to protect wildlife, they are for people too. Refuges are ideal places for people of all ages to explore and connect with the natural world. We invite you to learn more about and visit the national wildlife refuges and wetland management districts in Colorado, Kansas, Montana, Nebraska, North Dakota, South Dakota, Utah, and Wyoming.
The Mountain-Prairie Region's Office of Ecological Services (ES) works to restore and protect healthy populations of fish, wildlife, and plants and the environments upon which they depend. Using the best available science, ES personnel work with Federal, State, Tribal, local, and non-profit stakeholders, as well as private land owners, to avoid, minimize, and mitigate threats to our Nation's natural resources.
Providing leadership in the conservation of migratory bird habitat through partnerships, grants, and outreach for present and future generations. The Migratory Bird Program is responsible for maintaining healthy migratory bird populations for the benefit of the American people.
The U.S. Fish & Wildlife Service Fish and Aquatic Conservation Program in the Mountain-Prairie Region helps conserve, protect, and enhance aquatic resources and provides economically valuable recreational fishing to anglers across the country. The program comprises 12 National Fish Hatcheries.
Law enforcement is essential to virtually every aspect of wildlife conservation. The Office of Law Enforcement contributes to Service efforts to manage ecosystems, save endangered species, conserve migratory birds, preserve wildlife habitat, restore fisheries, combat invasive species, and promote international wildlife conservation.
External Affairs staff in the Mountain-Prairie Region of the U.S. Fish and Wildlife Service provides support to the regional office and field stations to communicate and facilitate information about the Service's programs to the public, media, Congress, Tribes, partners, and other stakeholders in the 8-state region.
Conservation and management of golden eagles requires understanding and addressing the factors that limit their populations. Although some population limiting factors such as the availability of prey resources and nest sites are considered “natural”, golden eagle management and mitigation typically focus on the effects of human activities on eagle populations. Human activities can limit golden eagle populations directly by causing mortality, and indirectly through impacts to habitat, prey and nest site availability. In a recent study of telemetered golden eagles, the U.S. Fish and Wildlife Service (Service) estimated that anthropogenic factors including shooting, poisoning and electrocution were responsible for approximately 56% of all eagle deaths (USFWS 2016). Subsequent population modeling indicated that the population would be larger without these additive sources of mortality. Human activities may also indirectly affect golden eagle survival and fecundity by modifying habitat and reducing prey resources. In the aforementioned telemetry study, the Service determined that starvation was the leading cause of mortality among golden eagles, and other studies have shown prey availability to strongly influence productivity of breeding golden eagles. Addressing the cumulative effects of direct and indirect population limiting factors will require expanded knowledge of how these factors operate and new management approaches ranging from planning at broad spatial scales to technical information for compensatory mitigation projects.
To support golden eagle management and development of compensatory mitigation methods, the Service and numerous research partners conducted research into factors limiting golden eagle populations and approaches for addressing them. The Service and their partners developed information resources and decision support tools to inform golden eagle management and mitigation. These include spatial models for decision support related to project siting and to identify conservation and management priorities; information resources to assist in the management of golden eagles, including compensatory mitigation; and a conservation banking framework.
Electrocution of golden eagles and other raptors on power lines has been recognized as a source of mortality for several decades. Despite legal protections under the Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act, it is estimated that approximately 500 golden eagles are electrocuted annually.
Electrocution occurs when a bird simultaneously contacts an exposed energized wire or component and another exposed wire or component of different electric potential; the structure and configuration of power poles is therefore an important determinant of electrocution risk.
Electrocution risk is also influenced by the density of eagle use (exposure) in areas where power poles exist. Minimizing electrocution hazard is an important conservation action that benefits golden eagle populations.
Addressing the problem of golden eagle electrocutions is a primary objective of the Service. To do so, the Service and collaborators developed risk assessment tools that can be used to aid siting of new power line routes, identify landscape-scale patterns of electrocution risk, and assess risk posed by individual power pole structures. The Service and others have also developed informational materials that identify common retrofitting mistakes and discuss solutions.
The likelihood of golden eagle electrocution can be minimized by:
Avoiding areas of high eagle use when routing new lines
The quality and security of breeding sites is an important aspect of golden eagle conservation and management. Golden eagles build their nests on a wide variety of substrates ranging from cliffs and rock outcrops to trees and human-made structures. The availability of suitable nest substrates can, however, limit the density and distribution of golden eagle breeding territories in some landscapes. Changes in availability of nest substrates, as in the loss of mature cottonwood trees in prairie landscapes, may result in local population declines through losses of territories.
At established territories, nest conditions such as vulnerability to predation and disturbance, exposure to direct sunlight, and infestations of ectoparasites (e.g., Mexican chicken bugs) may influence territory occupancy and productivity. Nests constructed on human-made structures may suffer reduced productivity due to inherent hazards (e.g., electrocution on utility structures) or physical disruption, as in re-opening of mine highwalls.
Alternately, some man-made structures may provide higher-quality nest substrates than those naturally available. Finally, human activities and subsequent disturbance of breeding golden eagles may negatively affect nest site occupancy and reproductive success.
Management actions to create or enhance nest substrates for golden eagles have the potential to increase occupancy and productivity at established territories, or even support the establishment of new territories, and may therefore provide valuable tools for eagle conservation and mitigation. Protective measures such as temporal and spatial buffers around golden eagle nest sites have long been applied to reduce the effects of disturbance caused by human activities, but a consistent basis for determining appropriate buffer sizes is lacking. Working with research partners, the Service conducted field research and developed information resources to improve the scientific foundation for management of golden eagle nest sites.
Human disturbance is recognized by researchers and the Service as a potential threat to golden eagles in the U.S. Available scientific information indicates that human disturbance can negatively affect breeding golden eagles by causing them to flush from nests and perches, reducing parental care, or failing to breed or occupying nest sites. Because these effects may result in “take” under the Bald and Golden Eagle Protection Act, it is important to determine appropriate actions for reducing or avoiding impacts from human disturbance.
Because empirical information about distances at which human activities disturb breeding golden eagles is limited, the Service used a structured process to formally elicit the knowledge and opinions of experts regarding distances at which breeding golden eagles are likely to be disturbed by various human activities. Results of the elicitation were synthesized with other available information to produce a scientific report that evaluates human disturbance of golden eagles to inform conservation decisions for the species.
The synthesis includes:
a review of the scientific literature regarding the effects of human activities on golden eagles and other raptors;
a discussion of how the responses of golden eagles to human activities may be influenced by characteristics of the individual bird, human activity, or environment; and
possible approaches for protecting breeding golden eagles from human disturbance.
The Service is currently using this synthesis and expert elicitation to evaluate possible measures for protecting breeding golden eagles from human disturbance, such as temporal and spatial buffers around nests or buffering territory core areas.
In addition to synthesizing existing information, the Service also supported field research on effects of off-highway vehicles (OHV) to nesting golden eagles, leading to multiple scientific publications evaluating various aspects of recreational disturbance.
Golden eagle populations are strongly influenced by availability of key prey species, and food availability may be a limiting factor for golden eagles throughout their annual cycle. For example, starvation is the leading cause of mortality among juvenile golden eagles. The distribution and abundance of medium-sized prey species such as hares, rabbits, and ground squirrels has been linked to breeding success, breeding territory occupancy, and population-level distribution of golden eagles. The status of prey populations and the impacts of changes in prey availability to golden eagles have been influenced by habitat modification and changes in land use across large areas of the western U.S. An improved understanding of prey selection by golden eagles, the dynamics of prey populations, and the effects of changes in prey communities on eagle populations is needed to support conservation actions and habitat-based compensatory mitigation.
To address these information needs, the Service published a synthesis of golden eagle diets based on an extensive literature review and analysis of previously unpublished data. The Service also developed a series of species accounts for key prey groups that address the importance of each prey group to golden eagles, and describe their biology, ecological roles, influences on abundance, and management considerations. Information on spatial and temporal patterns in golden eagle diets, along with species-specific information on important prey, can be used to inform prey management with an emphasis on supporting the development of compensatory mitigation, conservation banking, and other resource management programs related to golden eagles.
Physiological effects of hematophagous ectoparasites on golden eagle nestlings
Golden eagles across the West face several diseases, including trichomoniasis, West Nile virus, and aspergillosis, as well as hematophagous nest ectoparasites, such as Mexican chicken bugs (Haematosiphon inodorus). The prevalence and intensity of these stressors may be influenced by changes in climate, habitat, and/or available prey species. For example, declines in preferred prey species of golden eagles (e.g., black-tailed jackrabbits) in the Great Basin may lead to increased predation on rock pigeons and therefore exposure to the protozoan, Trichomonas gallinae, potentially increasing golden eagle risk of trichomoniasis in this area. The prevalence and negative effects of ectoparasites such as Mexican chicken bugs may increase with changes in climate. Mexican chicken bugs have been documented to decrease nestling fitness, and in some cases cause mortality.
Management of infectious diseases and nest ectoparasites at golden eagle nests may provide a method for compensatory mitigation, particularly when focused at local scales such as a mitigation bank. Assessment of the distribution, incidence, and local population effects of these stressors is necessary, however, before management prescriptions and their efficacy can be evaluated. To address these knowledge gaps, the Service partnered with collaborators to conduct a series of research projects designed to identify and understand factors that influence individual susceptibility to disease and ectoparasites within populations of golden eagles.
Several additional products are forthcoming that focus on prevalence, risk factors, and effects of T. gallinae and hematophagous ectoparasites on golden eagles. Research results suggest that disease and ectoparasites have the potential to negatively affect golden eagle productivity. The available and forthcoming products can provide the necessary foundation for developing management actions that may help reduce the impacts of disease and ectoparasites on golden eagles.
Environmental contaminants have long been recognized as potential threats to golden eagles and other raptors that opportunistically scavenge on dead animals, with lead and anticoagulant rodenticides currently the contaminants of primary concern.
While some sources of lead in the environment have been reduced or eliminated (e.g., lead paint and leaded gas), animal carcasses and gut piles contaminated with lead bullet fragments provide an exposure route for scavenging golden eagles. Anticoagulant rodenticides, often used for control of prairie dogs and other ground squirrel species, are emerging as a potential threat to golden eagles, particularly second generation rodenticides, even though they are not approved by EPA for agricultural field or rangeland use. Lead and anticoagulant rodenticide exposure may have sublethal and lethal effects, depending on individual and environmental factors.
To summarize existing research and further evaluate patterns of exposure, the Service collaborated with USGS researchers to develop a review and synthesis of contaminant risks to golden eagles, and conduct field research on recreational shooting of ground squirrels and lead exposure in nestling golden eagles. We also supported an investigation of lead, rodenticide, and mercury levels of eagles found dead in USFWS Legacy Region 6 (Interior Regions 5 and 7, excluding New Mexico); and developed a lead exposure risk index map based on ungulate harvest rates.
Conservation banks are permanently protected lands that are managed for a species to offset adverse impacts to that species. Conservation banking benefits species by establishing large reserves that function as compensatory mitigation areas for multiple projects. In exchange for permanently protecting the land and managing it for the species, the Service approves a specified number of habitat or species credits that bank owners may sell to project proponents who need to compensate (mitigate) for the unavoidable adverse impacts their projects have on the species.
The Bald and Golden Eagle Protection Act (Eagle Act, 16 U.S.C. 668–668d) prohibits take of eagles except pursuant to federal regulations and requires that any authorized take of eagles be compatible with the preservation standard. Because it has been determined that there is no sustainable take of golden eagles nationwide, (i.e., the Service sets take limits at zero), all authorized take of golden eagles must be offset by compensatory mitigation at a ratio of 1.2 to 1 to mitigate remaining impacts after the application of all practicable avoidance and minimization measures. Conservation actions that offset project-induced eagle mortality or disturbance by reducing take elsewhere are considered compensatory mitigation, which may include activities such as retrofitting power lines to reduce eagle electrocutions, removing road-killed animals along roads where vehicles hit and kill scavenging eagles, or increasing prey availability.
The Service has received multiple proposals for developing conservation banks to benefit golden eagles, but to date none have been implemented, largely due to the difficulty in quantifying the number of golden eagles added to a local population by a given management action. To aid in the development and review of golden eagle conservation bank proposals, the Service created an analysis framework that outlines factors that should be considered for the establishment of potential conservation banks. The Golden Eagle Conservation Bank Analysis Framework is linked to a wide range of resources such as golden eagle habitat models and risk assessments that support site selection, establishing baseline conditions, identifying local limiting factors and potential management actions, and development of a mitigation plan. Taken together, these resources represent a science foundation that supports the development and implementation of management actions that are likely to benefit golden eagle populations and may provide the basis for compensatory mitigation credits.