Golden Eagle Aquila chrysaetos
Version: 2.0 — Published September 17, 2020
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Conservation and Management
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Although the Golden Eagle has special conservation status and appears on Red Lists in many parts of its range it is ranked by IUCN as a species of Least Concern on a global scale. The species is listed in CITES Appendix II and has legal protections within most countries in which it occurs. Globally, the Golden Eagle is an iconic and culturally important flagship species (615, 85). In ancient Egypt, eagle hieroglyphs were symbolic of the soul after death. In contemporary North America, native cultures incorporate eagle feathers into medicines and religious ceremonies. Eagles have long been trained for falconry in Central Asia and are still used to hunt prey as large as wolves in Mongolia.
Historically, in North America and Eurasia, the Golden Eagle was heavily persecuted, via shooting, trapping, or poisoning, causing reductions in population size. Recent reduction in persecution, likely is related to stable or increasing population trends in some countries. However, threats to the species remain due to habitat change and the potential for lead poisoning, collision with wind turbines, electrocution, illegal killing, and even negative interactions with reindeer herding in northern Scandinavia. Disjunct populations in Ethiopia may be rapidly declining.
Legal and Illegal Taking and Trade of Eagles and Eagle Feathers
Trade for eagles in North America is primarily focused on two areas. First, the U.S. Fish and Wildlife Service (USFWS) allows use of a small number of wild-caught eagles for falconry. There are rules that limit the number taken from the wild (616), and these rules change frequently. Second, there is a commercial market for Golden Eagle and their parts for legal use in Native American religious ceremonies and for other illegal uses.
The USFWS authorizes permits to allow Native Americans to take and possess eagles and their parts for religious purposes. The taking of up to 40 nestling eagles by Hopi tribes is authorized under a special permit from the USFWS (617). However, authorized take does not necessarily reflect actual take, and the actual take by Hopi averages around 23 eagles per year (618, 617).
Eagle carcasses in the United States are sent to the USFWS National Eagle Repository for eventual distribution to Native American tribal members. The role of the repository is to “collect, process, and distribute, as expeditiously as possible, eagle feathers and remains to federally recognized tribal members for religious, ceremonial, and cultural purposes in accordance with Federal law” (618).
Illegal take of Golden Eagles happens in many places in the United States A sting operation by the USFWS in 2018 recovered parts from 143 Golden Eagles. The defendants in this case were mostly from the states of South Dakota, and North Dakota, Montana, and Wyoming (619).
Because of their cultural and religious significance, Golden Eagles command a high black-market value that fuels illegal killing and trafficking of eagles (620, 619). A whole Golden Eagle carcass can bring $1,000 to $1,500, a single tail feather from a young eagle, $100, and complete tail, $500 to $800 (620). Collectors of headdresses, bustles, and other replicas of Native American regalia that include eagle feathers are marketed to non-native and Native Americans in the United States and overseas (619).
Legal and Regulatory Protections
Golden Eagle is listed in CITES Appendix II, which includes non-threatened species for which trade should be controlled to protect their survival.
Golden Eagles have legal and regulatory protection in most European countries.
Golden Eagles have legal protection in most of their range states in Asia. They appear in the "Red Data Books" of most central, east and south Asian countries.
U.S. Federal Level
As a result of widespread intentional killing of Golden Eagles in the United States (see Conservation and Management: Effects of Human Activity: Shooting and Trapping), the Eagle Act, originally passed in 1940 to protect the Bald Eagle, expanded coverage in 1962 to include Golden Eagle. The act is now referred to as the Bald and Golden Eagle Protection Act (BGEPA; 1962 U.S. Code Cong. & Admin. News, p. 1453. Act of October 24, 1962, Pub.L. No. 87-884, 76 Stat. 1246). A 1962 revision of the BGEPA recognized the importance of eagles to Native American culture and included an exception allowing Native Americans to obtain permits for take and possession of eagles and eagle parts. That same revision also protected young, eggs, and nests of eagles. Subsequently, BGEPA was amended in 1972 because of ongoing concerns for declining Golden Eagle numbers. The revision aided in enforcement by outlining, “…criminal and civil sanctions as well as an enhanced penalty provision for subsequent offenses,” “forfeiture of anything used to acquire eagles in violation of the statute,” and provision for revoking public land grazing leases of ranchers in violation of the Act. Amendments passed in 1978 authorize and regulate “taking” of unoccupied nests on resource development sites. BGEPA also authorizes rewards for anyone providing information that leads to the arrest and conviction of those who violate the Act (1972 U.S. Code Cong. & Admin. News, pp. 4292–4293; 16 U.S.C. §668(a)).
Golden Eagles in the United States are provided federal protection in several other ways. Most important is the Migratory Bird Treaty Act (MBTA; 16 U.S.C. §§ 703–712). MBTA is similar to BGEPA in that it prohibits taking of migratory birds, including eagles, but the details and implementation of MBTA differ substantially from BGEPA.
The USFWS issues guidelines and regulations designed to protect eagles from take and to set thresholds for permitting take. In 2007, USFWS issued National Bald Eagle Management Guidelines to publicize how Bald Eagle is protected, to advise the public on how human activities may disturb eagles, and to encourage nonbinding management practices to benefit eagles (621). No similar document was produced for the Golden Eagle.
In 2013, USFWS issued an Eagle Conservation Plan Guidance with the goal to help make wind energy facilities compatible with eagle conservation and the laws and regulations that protect eagles (622). In 2016, the USFWS published a final rule in the Federal Register that revised regulations for eagle incidental take and take of eagle nests. Permits issued under this and earlier rules provide a framework for permitting incidental take of eagles, an especially important topic for renewable energy development. Finally, USFWS has created a Bald Eagle and Golden Eagle Electrocution Prevention In-lieu Fee Program that sells compensatory mitigation credits for take of Bald and Golden Eagles. All these, together with many other rules and regulations, form the framework by which the United States Government protects and manages Golden Eagles. As these rules change frequently, readers interested in current protections in the United States should follow up with their local office of the USFWS Division of Migratory Bird Management.
U.S. State Level
In addition to federal protections, in the United States, Golden Eagles are protected by law in most states in which they occur. These protections take the form of specific laws or sometimes by including them on lists of endangered, threatened, or special concern species. Golden Eagles often are mentioned in planning documents such as state Wildlife Action Plans (SWAPs). Regulations vary widely among states, often in relation to the abundance of Golden Eagles in the state and the time of the year in which they are present (i.e., many eastern states do not have state laws that protect Golden Eagles because they do not nest in those states and are present only in winter).
Within Canada, Golden Eagles are not protected at the federal level by the Canadian Migratory Birds Convention Act of 1994. However, individual provinces and territories provide protections to Golden Eagles and other species of wildlife. For details on these and a list of the relevant acts, see here.
Effects of Human Activity
Habitat Loss and Alteration
Habitat alteration has important, often negative effects on the Golden Eagle. Occasionally, such as when nesting sites are created, they can be beneficial to the species.
Climate change is associated with change in eagle habitat. One way climate change acts on habitat is by contributing to an increase in the number and size of wildfires (623, 624, 625), which often lead to the subsequent invasion of exotic plant species (626). In the intermountain American West, since 1980 fires have caused large-scale loss of shrubs and jackrabbit habitat in areas used by eagles. For example, wildfires in the Morley Nelson Snake River Birds of Prey National Conservation Area (NCA) burned 43% (approximately 53,000 ha) of the shrubland habitat between 1979 and 1994 (627). Nesting success at burned territories in the NCA declined after major fires but subsequently increased again, 10–11 years afterwards (604). The number of occupied territories in the NCA has declined significantly after burning, but productivity of the remaining nests has not changed although there have been dietary shifts in the burned territories (348, 603). Combined, these data suggest a possible reduction in carrying capacity for Golden Eagle in the NCA that is driven by climate change mechanisms (604, 603).
Energy development is also associated with changes to eagle habitat. In western North America, modern energy development of all types (e.g., wind and solar, oil and gas) could potentially affect > 40 million ha of shrublands and > 70 million ha of grasslands (628). Wind energy development in Wyoming is not expected to affect nesting habitat for Golden Eagle (629), but there is documented potential for conflict between eagle flight habitat and wind turbines (8, 405, 630, 403).
Golden Eagle nesting and wintering areas occur in habitats where coal and other mineral development occurs (7). Mine high walls can provide nesting sites for eagles (631), but surface coal mines can threaten scarce nesting sites in Wyoming (632). This interaction may become less relevant if less coal is mined when coal-fired power plants are decommissioned (633).
Urbanization and human population growth also alter eagle habitat. These processes have rendered many historical eagle use areas unsuitable, particularly in southern California (634) and the Colorado Front Range (597). In one study, abandoned territories in San Diego County, California, had more dwellings within 2 km and higher human populations within 5 km than territories that continued to be occupied (634). In addition, widespread agricultural development and urban sprawl in the western United States is known to reduce jackrabbit populations and makes areas less suitable for nesting and wintering eagles (473, 347, 234).
The most widespread anthropogenic alteration of habitat now occurring in eastern North America results from hydraulic fracturing (“fracking”) associated with shale gas development (635). Wintering Golden Eagles in this region are associated with forested landscapes, but they also use open areas within those forests (144). Fracking creates forest openings, but it is not known how the effects of fracking on forest cover will influence Golden Eagle numbers.
Landscapes in eastern North America have changed dramatically over the past 100 years as forest cover has increased and suburban landscapes have grown in prominence. These combined effects have had important consequences for numbers of white-tailed deer and wild turkey, both important prey species for eastern Golden Eagle (5).
Effects of Invasive Species
Invasive predators have few impacts on the Golden Eagle. The species sometimes feed on non-native prey (e.g., Ring-necked Pheasant, Rock Pigeon; 304) that may be considered invasive. Parasites that are invasive or expanding their distribution also may be consequential to eagles. See Demography and Populations: Disease and Body Parasites for additional details. Changing weather patterns associated with global warming contribute to an increase in wildfires and the subsequent spread of invasive grasses (e.g., cheatgrass [Bromus tectorum]) plant species (626, 636). These exotics can dramatically alter fire regimes of shrublands and affect important habitats (637), affecting prey species, such as jackrabbits, which in turn affects Golden Eagle distribution and subsequent eagle territory occupancy, reproductive success, and distribution patterns during their annual cycle (604).
Shooting and Trapping
Historically, eagles have been shot in parts of North America where depredation of domestic livestock was suspected, and to supply the trade in eagle-related Native American artifacts. Unregulated but legal aerial hunting of eagles began in California as early as 1936, with > 200 killed that winter. From 1941 to 1961, 20,000 Golden Eagles may have been shot from airplanes in southwestern states (417). Hunting clubs in western Texas shot nearly 5,000 eagles between 1941 and 1947, likely reducing the number of breeding pairs in parts of Texas and New Mexico (638). In 1971, > 500 eagles were killed in Colorado and Wyoming by helicopter gunmen hired by sheep ranchers (639).
Even after legal protections were enacted (see Conservation Status: Legal and Regulatory Protections), eagles continue to be killed and shooting appears to be a common cause of death of eagles in North America and elsewhere in the world (611, 640, 574, 422).
Native Americans harvest Golden Eagles for cultural and religious purposes (641, 642). Historically, this harvest was widespread, and it pre-dated other forms of human-caused mortality in North America (29, 422). Some tribal cultural and religious activities involve the taking of live eagles. For example, members of the southwestern Hopi tribe remove nestlings from nests in April, raise them in captivity, and sacrifice them in July, when they are fully feathered. Recent research indicates that harvest may negatively affect local fledgling production (643).
Incidental Capture by Mammal Trappers
Incidental trapping resulting in death of eagles has probably occurred as long as people have been trapping mammals. Eagles are incidentally captured in traps set for mammalian predators for predator control, and in traps set to capture furbearing mammals for commercial and other purposes.
There is peer-reviewed published evidence that eagles and other raptors are attracted to exposed bait associated with leg-hold traps, snares, and poison sets designed to catch wild furbearers and other vertebrate animals (575, 644, 645, 573). Most trapping or poisoning deaths occur in winter when eagles are more likely to scavenge. Females may be more susceptible to incidental trapping or poisoning than are males (575).
There are numerous anecdotal reports that illustrate the diversity of ways that eagles may be inadvertently captured in traps for mammals. In western North America, two adult females were incidentally killed in a marten trap in April 1901 in the Forty-Mile region of western Yukon Territory, Canada (646). Much more recently, 3 telemetered eagles from south-central Alaska were incidentally killed in wolf snares in central British Columbia in winter (December, January) in 2016 and 2018 (T. Booms, personal communication).
In the eastern United States and Canada, Golden Eagles are sometimes caught in and killed in both snares and leg-holds (647, TEK, TAM). Of 95 Golden Eagles tracked in eastern North America, 6 were captured in snares or leg-hold traps (TAM, TEK). In recent years, several Golden Eagles and Bald Eagles have been photographed at migration count sites, at bait over carrion, or simply in flight, with broken-off snares hanging around their necks (TAM), or with leg-hold traps attached to one foot (TEK).
Strychnine is highly toxic to birds, including eagles (648), and has been used to control animals in the United States since before 1947. However, because of threats to non-target species such as raptors, above-ground use of the toxicant has been prohibited in the United States since 1988 (644). At least 10 eagles died in 1971 from eating thallium sulfate–laced antelope set out by sheep ranchers in Wyoming. Poisoning of this type by sheep ranchers continued into the 1980s (639). Carbofuran, which kills raptors frequently in Africa (649), also can present risk to Golden Eagles (650) if it is used inappropriately within their range. In Scotland, this toxicant is used illegally to kill Golden Eagles (651). Carbofuran was banned in granular form in the United States in 1999 because of its lethal effects on migratory birds. The U.S. Environmental Protection Agency issued a final rule in May 2009 banning all use of carbofuran (marketed as Furadan) on food crops in the United States It is also banned in Canada.
Pesticides and Other Contaminants or Toxicants
Susceptibility of Golden Eagles to organochlorine pesticides appears to depend on the degree to which birds in a given region feed on birds or mammals. In the western United States where the species feeds primarily on mammals, data suggest that Golden Eagles are not highly exposed to DDT poisoning. For example, eggs collected after 1946 had shell thicknesses similar to those collected in earlier years (519; for additional details, see Breeding: Eggs: Eggshell Thickness). Likewise, from 1964 to 1975, when many organochlorine pesticides were still legal, DDE and dieldrin levels in eggs and tissues from Golden Eagles in western North America were below thresholds known to cause reproductive problems (for exact levels, see 358, 199, 652, 653). From 1990 to 1993, 48% of migrant eagles in west-central Montana had detectable levels of DDE in their blood, but the maximum concentration was < 0.021 ppm wet weight (654). Of 14 territorial Golden Eagles captured and tested in the Columbia Basin, Washington from 2005-2013, six had DDE levels below detection levels, and the remaining eight had low but detectable DDE concentrations (316). Dieldrin was not detected in eggs in that study. Finally, DDT poisoning was not the cause of death for any of the 139 tracked and recovered Golden Eagles considered in the U.S. Fish and Wildlife Service analysis noted previously (422).
In the northeastern United States, a region where Golden Eagles may eat more birds, long periods of reproductive failure followed by territory vacancy suggest that DDT poisoning had a role in the local extirpation of the species (5). Numbers of adult eagles counted at migration count sites in eastern North America declined during the DDT era (195), and chronic nesting failures in New York were attributed to DDT poisoning (216). Finally, a single unhatched egg collected from one of the last occupied eagle territories in Maine, in 1996, contained levels of DDE and PCBs adequate to impair reproduction (195).
Golden Eagles are exposed to mercury, but the toxicant is usually detected at low levels. Data reported in the literature come primarily from western North America, although different studies have different minimum detection levels. Mercury was detected at low levels (<1ppm in blood) in 22% of 77 migrant eagles sampled in Montana from 1985–1992 (654), and in 21% of 70 migrants sampled between 2008 and 2010 (655). The latter study also reported that 83% of birds had low but detectable levels of mercury in feathers. Similarly, mercury was detected at low levels (≥ 0.015 ppm) in the blood of most of the 16 Golden Eagles trapped in the Columbia Basin, Washington from 2005–2013 (316). Finally, 72% of 214 wintering eagles sampled in Idaho from 1990 to 1995 had low but detectable mercury levels in blood (between 0.001 and 0.4 ppm; 443, EHC, T. Craig, unpublished data).
Eggs collected in Canada between 1968 and 1975 contained mercury at levels thought to be too low (<0.35 mg/kg) to affect reproduction (n = 22; 653). Mercury residues in eggs and tissue from Idaho also were below lethal levels (<1 ppm; 199). However, some of the nestlings tested in that study from agricultural areas had elevated mercury residues in feathers, possibly because they ate Ring-necked Pheasants that had eaten seed treated with methyl mercury. A single unhatched egg collected in 1996 from an eyrie in Maine had a mercury level of 0.526 ppm (195).
Lead poisoning has long been recognized as a threat to Golden Eagles in North America (656) and more recently in Europe (13, 18). It is thought to cause about 2–3% of Golden Eagle deaths in the United States (422), although elevated but sublethal blood lead levels are widespread across the continent (657, 658). Data from individual field studies support these observations. Elevated blood-lead levels (> 0.20 ppm; 659, 660) occurred in 36% of 162 eagles from southern California, 1985–1986 (661), 46% of 281 wintering eagles from Idaho, 1990–1997 (443), 56% of 86 spring migrants in Montana, 1985–1993 (654), 33% of 178 autumn migrants in Montana, 2006–2012 (662), and 30% of 66 eagles captured during winter in the eastern United States 2010–2016 (J. Cooper, M. Lanzone, S. Van Arsedale, W. Perrone, unpublished data; TAM, TEK). Lead poisoning is also a frequent cause of illness or death of eagles admitted to rehabilitation centers (656, 659, 663) or necropsied at wildlife health labs (664).
A recent large-scale analysis of Golden Eagles from across the United States provides the most comprehensive look at the extent to which eagle populations are exposed to lead (665). Of 384 eagles whose blood was tested, only 13% had no evidence of lead exposure (lead levels were below the level of detection of the instrument), and 9% had blood lead levels above the threshold for clinical poisoning (> 50 ug/dL). Liver data from 171 eagles told a similar story: only 10% had no evidence of lead exposure, and 7% were above the threshold for clinical poisoning. However, lead levels in eagle bone, an indicator of chronic subclinical lead exposure (664, 18), provided a different perspective on lead exposure. Of 223 individuals sampled, only one had no evidence of lead exposure, and nearly 50% had levels above the threshold for clinical poisoning. This study also provided evidence of seasonal, regional, and age-related variation in lead exposure. Finally, although this study detected no sex-related differences in lead exposure, other studies have identified potential differences in lead exposure of male and female eagles (238).
There is good evidence that eagles are exposed to lead via their diet (666). Sources of lead are predominantly fragments of ammunition in hunter-killed mammals and birds (664, 667, 668, 657), particularly deer (661) and ground squirrels (654, 669, 670). Blood-lead levels vary with season (661, 238), and they decreased regionally after a ban on lead ammunition was implemented in parts of California (671). Seasonal variation in blood lead levels and the correspondence of the timing of eagle scavenging with the timing of hunting seasons provide good evidence of the link between human hunting behavior and lead exposure of eagles (672, 665).
Eagles that consume prey items contaminated with lead may experience only temporary elevations in blood lead levels (654), but the linkages between routes and intensity of exposure and consequent tissue lead levels are poorly understood (673). Blood-lead levels of 67% (n = 33) of wintering eagles in east-central Idaho, increased or stayed the same when recaptured (from 1–5 years after initial capture), suggesting repeated exposure to lead (443). Chronic subclinical lead exposure may alter movement behavior of Golden Eagles (674) and also may weaken birds and predispose them to injury, predation, starvation, disease, or reproductive failure (659, 443).
Secondary poisoning occurs when individuals consume prey killed or sickened by chemical pesticides such as those used to protect crops or kill rodents. Recent evidence suggests that anticoagulant rodenticides may be an important source of increased mortality rates for many birds of prey (675, 422). Golden Eagle is susceptible to several different first- and second-generation anticoagulant rodenticides (676, 675, 677). From 1990 to 1993, heptachlor epoxide levels in plasma of spring migrants in west-central Montana were < 0.039 ppm wet weight (654). Three eagles that died in Oregon from 1977–1980 had lethal (> 8 ppm) levels of heptachlor epoxide (678). Those poisoned eagles apparently ate prey that had eaten heptachlor-treated seed. Anticoagulant rodenticide also was detected in the liver of the single Golden Eagle whose carcass was submitted to the New York Department of Environmental Conservation (679).
Collisions with Stationary or Moving Structure or Objects
Often are injured or killed by collisions with cars, fences, wires, and wind turbines (422). Of these, collisions with vehicles may be the most common. As an example, nearly 1,000 Golden Eagles were killed on highways near Rock Springs, Wyoming in winter 1984–1985 (638).
Eagle mortality from blade strikes at wind energy facilities is of substantial interest within the United States and in Europe (see, e.g., 8, 680, 681, 682). At least 79 Golden Eagles were killed at 10 facilities in the United States from 1997–2012, with most fatalities occurring towards the end of that period as turbines became more numerous (682). However, this study almost certainly underestimates actual fatalities because it relies on incidental finds and voluntary reporting, and it ignores some of the facilities in California where many recorded fatalities have occurred. For example, during the period 1998–2002, an average of 67 Golden Eagles were killed each year by turbine blade strikes at the Altamont Pass Wind Resource Area, California (8). That number appears to have declined with repowering and installation of larger turbines (683).
Golden Eagle fatalities at wind turbines have occurred in most western U.S. states, especially Wyoming. Of 113 deaths of eagles tagged from 1994 to 2000 in and around Altamont Pass (6), 37% were turbine strikes, 11% were electrocutions, and 6% were non-anthropogenic in origin. The remainder of fatalities were unknown in origin or were from poisonings, collisions or shootings. In another study, > 25% of fatalities at Altamont were of birds that grew their feathers long distances away, suggesting that demographic impacts extend far beyond the region where the turbines are located (684).
Golden Eagle is vulnerable to electrocution when they land on power poles and they are among the most frequently electrocuted raptors in North America (685, 686). Pole configuration is the most frequently identified risk factor associated with electrocution of eagles (687). Younger birds appear more susceptible to electrocution, possibly because they are less skilled fliers and more likely to make contact with wires when landing (685, 686, 422, 687). Risk also appears to increase when inclement weather hampers flight or when wet feathers increase electrical conductivity (688, 685). A large proportion of electrocutions appear to occur during winter and in areas in western states where there are relatively fewer natural perches (689, 690).
Human release of pharmaceuticals and other environmental contaminants may have indirect effects that are not well understood. Antibiotic resistant bacteria have been found in Bald Eagles in Alaska (691). The demographic consequence of these infections, whether direct or indirect, are not understood and it is not clear whether Golden Eagle is also exposed to these drug-resistant bacteria.
Beyond indirect effects of pharmaceutical products via drug-resistant bacteria, these chemicals may also have direct effects. In particular, non-steroid anti-inflammatory drugs have caused widespread declines in vultures in south Asia (692), several are toxic to many raptor species (693) and at least one of these, Diclofenac, is known to be toxic to congeneric Steppe Eagles (Aquila nipalensis; 694).
Disturbance at Nest and Roost Sites
Human activity near nests can prevent nesting and cause failure of breeding attempts by Golden Eagles. Human activity close to nesting sites was thought to be the main reason that several eagle pairs did not nest in a northern Colorado study area (695). As of 1985, abandoned Golden Eagle territories in San Diego County, California, had more dwellings and higher human populations nearby than did territories that continued to be occupied (634). Two studies in western North America attributed 46–85% of Golden Eagle nesting failures to human disturbance (472, 268), and nesting success in Scotland is related inversely to human disturbance around nests (2).
Human activity near nests also can interfere with and reduce parental care. Adult Golden Eagles in Alaska spend less time at nests and feed their young less often and a smaller amount of food per day when observers are camped close by (696). That study suggested that vulnerability of nesting eagles to human disturbance likely depends on topography and physical characteristics of the nest (696).
Outdoor recreation, whether on foot or by off-road vehicle can influence the nesting biology of eagles adversely. Golden Eagle territory occupancy rates in northern Finland are lower near tourist communities and are associated negatively with the length of nearby skiing and snowmobile trails (697). In southwestern Idaho, occupancy and success of territories near recreational trails and parking areas declined from 1999 to 2009 after a dramatic increase in off-highway vehicle (OHV) use (546). In contrast, occupancy and success of territories not impacted by OHVs did not change. In that same study area, a 2-year follow-up study indicated that OHV use was associated with a reduction in the probability of both territory occupancy and nest survival (419). In addition, early season pedestrian use and other nonmotorized use reduced the probability of egg-laying, and pedestrians, who often arrived near eagle nests via motorized vehicles, were associated with a reduction in time that eagles spent at the nest. A more recent study in the same area concluded that recreation can be a significant threat to occupancy of eagle territories and reproduction (698). Modeling indicated that recreation effects on eagle reproduction can have population-level consequences, through a process whereby marginal territories become vacant and reproductive potential of eagles is reduced in areas with high levels of recreation activities (699).
Nesting Golden Eagles were not affected adversely by helicopter passes during heli-skiing and military operations in the Wasatch Mountains of Utah (430). There were no differences in nesting success or productivity the year of the helicopter activity, or in occupancy in following years, at territories that were visited and not visited by helicopters. In that study, most (66%) eagles either showed no response or watched (30%) the 227 helicopters passing by. The few cases eagles responded (2% of passes), were all after hatching and the responses were that eagles would either flatten in the nest or fly away from the nest. These data are consistent with anecdotal observations from biologists who have conducted surveys of eagle nests from helicopter (MNK, P. Bloom, personal observations).
An anecdotal account from a single nest in Arizona suggests that birds do not respond to sonic booms or low-level jets flights (700). However, a larger-scale study in Idaho suggested that when military training was occurring, birds were less frequently seen attempting to capture prey, and, in years when prey levels were low, flew at higher altitudes during training than when training did not occur (701).
Golden Eagle may grow habituated to presence of humans (CLM, MNK, 702) as is the case for other related species (habituation, the reduction of a response to a frequent stimulus is to be distinguished from tolerance, which does not require repeated exposure to a stimulant). Bald Eagle is reported to habituate to human activity (703, 704). Similarly, nest defense by Spanish Eagle in response to research visits grows more intense over time, as the birds gain experience with researchers (705).
Putatively benign or beneficial research activities also can influence survival and behavior of Golden Eagle. For example, climbers entering nests for research purposes can kill eggs or nestlings when they: (1) spend too much time at a nest and cause parents to abandon eggs or nestlings; (2) keep parents off a nest long enough to subject eggs or young nestlings (incapable of thermoregulation) to overheating or cooling; (3) flush an adult, who accidentally knocks an egg or nestlings out of nest; (4) cause a nest to collapse; or (5) cause nestlings to fledge prematurely. These cases are rare and can be avoided with proper precautions (706; USGS, unpublished data). Likewise, as noted above for closely related Spanish Imperial Eagles, repeated visits to nests, conducted at territories over many years, resulted in increased intensity of nest defense (705). Furthermore, nestling Imperial Eagles handled by ungloved human hands were more likely to have Staphylococcus infections than were those handled by scientists wearing gloves (707).
There is other evidence from North America of research impacts on Golden Eagle. Of 76 eagle pairs monitored in the states of Colorado, Montana and Wyoming, the 23 whose nests were visited and whose young were banded were more likely to switch nests and less likely to attempt breeding in the subsequent year, than were those whose nests were not visited (549). At a single nest in Montana, nestlings lost weight when parents temporarily abandoned nests following a prolonged visit to a nest by researchers (529). All these nestlings later fledged at or above normal weights (529).
As is the case for recreational or military aircraft, surveys conducted by aircraft also do not seem to influence behavior or productivity of eagles. Early studies from fixed-wing aircraft in the Rocky Mountains caused no desertions or mortalities, despite the fact that the pilots deliberately passed close to the nest in an attempt to drive eagles away (to check nest contents; 708). In later studies in Montana, close approaches with fixed-wing aircraft and helicopters never caused adults or nestlings to flush from cliff nests (709). During 906 helicopter passes by nests with incubating adults in southwestern Idaho and interior Alaska (n = 20 yr), only 11 adults flushed from nests. However, behavior differs when birds are not on the nest. In the Idaho study area, adults perched away from nests flushed in 121 times of 227 passes. No nestlings were flushed prematurely from nests during 778 helicopter checks in southwestern Idaho and Denali National Park and Preserve, Alaska (USGS, unpublished data; CLM).
Eagles may respond to aircraft in other ways. Coyle (323) observed “aggressive territorial behavior” toward a Piper PA-18 Super Cub fixed-wing aircraft on numerous occasions during nest surveys in North Dakota. In contrast, eagles rarely attack helicopters during nest surveys or flyovers in southern Idaho (3, EHC; T. Craig, personal communication), interior Alaska (n = 30 years, > 90 territories; CLM), the Brooks Range, Alaska, (EHC; T. Craig, personal communication), or Utah (430).
Capture and marking of eagles (wing tags, transmitters, rings/bands) almost certainly influence birds and may have negative consequences for individuals. It is not known how these factors influence populations, although individual birds are known to have been injured or killed by nest entry, or errors in capture, handling, or marking (TEK, MNK, KS, CLM, EHC, TAM).
However, in southwestern Idaho, wing markers had no adverse effects on individuals marked as nestlings (710). Likewise, in Wyoming, six adults wearing colored wing markers exhibited normal reproductive behavior and above-average reproductive success (711). In southwestern Idaho, nine nesting pairs with adults wearing backpack radio transmitters had similar productivity and success rates as control pairs (n = 3 yr; 176).
Importantly, other studies suggest the potential for negative effects on reproduction and survival from trapping territorial adults and fitting them with wing-markers or telemetry devices (MNK, M. Lochkart, unpublished data). Furthermore, these markers potentially can alter drag and airflow, thus influencing flight behavior, migratory performance, metabolic rate, and survival as has been shown for other species (712, 713, 383, 714, 715, 716). This is especially true when tail-mount transmitters are used (e.g., 717, 718), as these have well-documented negative effects (719, 720). Finally, although there are few data to evaluate strengths and weaknesses of different designs of harnesses for attachment of telemetry units to birds, this likely influences the effect of telemetry units on birds (CLM, TAM, TEK). Appropriate positioning of telemetry devices near the center of mass of the animal, reductions in size related to technological development, and advances in form factor to reduce drag (716), and improvements in harness design, all may reduce the effects of tagging on research animals.
Conservation Measures and Habitat Management
Mitigation and Management
In conjunction with the Eagle Conservation Plan Guidance and the framework for permits for incidental take, the USFWS established a policy of “no net loss’’ for Golden Eagles in the United States. As such, any permitted take must be offset by actions that either reduce Golden Eagle mortality from another source or increase Golden Eagle productivity (622). Currently there are limited approved options to compensate for take (622, 721). However, the USFWS has a stated policy of willingness to approve credible and defensible forms of mitigation that will offset added mortality, such as nest site improvements demonstrated to increase productivity (B. Millsap, personal communication). As of 2020, several proposals for mitigation options are being considered. Most prominent of these is to mitigate take of eagles by reducing lead poisoning rates of eagles. This would be implemented via efforts to convince hunters to voluntarily switch from lead to non-lead hunting ammunition (“lead abatement”; 722). Other similar proposals include removal of ungulate roadkill where eagle scavenging can result in collision mortality, prey habitat improvement, nest site enhancement, and rehabilitation of injured birds (721).
Despite these alternatives, mitigation to offset take for the Golden Eagle is primarily accomplished via retrofitting power poles that pose the risk of electrocution. Over the past 40 years, biologists, engineers, and government officials have cooperated in developing and publicizing power-pole designs that reduce raptor electrocutions. Some new power lines in non-urban areas have been built to raptor-safe construction standards (688). Since the early 1970s, utility companies have modified poles to prevent eagle electrocutions and such retrofitting is an important component of mitigation to offset take at wind energy facilities. Retrofitting may be an effective way to reduce fatalities of eagles due to electrocution, though this can be difficult to demonstrate (685, 686); nonetheless, birds can still be electrocuted when retrofitting is done incorrectly (723).
Because of the risks to eagles and other birds associated with leg-hold and snare traps for mammals, many U.S. states have regulations governing their use. Typical approaches to minimizing take of birds is to prohibit use of exposed baits, or to require baits to be located away from traps to avoid capturing non-target species (645); see online trapping regulations published by state wildlife agencies for additional information. Nevertheless, eagles are still captured in such traps when they are set illegally or in states without these regulations. Snares appear to be particularly dangerous to eagles in Quebec because there are no regulations requiring stops that prevent the snare from fully closing around an eagle’s neck (647).
Mitigation and management for take of eagles at wind energy facilities is, as of 2020, an important research focus within the United States. The U.S. Department of Justice has prosecuted two wind companies for killing eagles in Wyoming (724, 725). These prosecutions resulted in fines for these companies and some of the money generated from those fines was used to establish research and mitigation funds to support conservation of Golden Eagles in Wyoming. The U.S. Fish and Wildlife service has issued permits to allow take of eagles at wind facilities, but take requires offsetting mitigation or management actions (721). Because there are limited options for mitigation of take of eagles, the U.S. Department of Energy has funded research programs focused on developing detection and deterrent technologies that would reduce frequency of eagle-turbine collisions. Detection technologies often involve computer vision solutions such as IdentiFlight or DTBird. As of spring 2020, no deterrents are commercially available, although loud noises and bright lights have been tested to scare away birds. These technologies are nascent but, in many cases, promising, and their development, in conjunction with the development of mitigation options described above, has the potential to have broad benefits for eagle conservation.
Hacking techniques have been used to establish or re-establish populations of raptors (726). Hacking involves placing nestlings in artificial cages at sites where they will eventually be released. Humans care for the young until they are of fledging age, at which point the cage is opened and birds are allowed to leave and begin feeding themselves. Often, fledglings will continue return to be fed at hack sites for 4–6 weeks until they achieve independence. Hacking has been used for the Golden Eagle in North America in the southern Appalachians (see Introductions in the Southern Appalachians, below), in Kansas (727), and possibly elsewhere.
Golden Eagle is occasionally responsible for losses of newborn domestic sheep on the open range in the western United States (425), particularly in cool, wet springs when rabbit populations are low (728). In the past, some of these birds have been trapped and relocated. In 1975, for example, 145 Golden Eagles were trapped and relocated (729). A later study of marked and relocated resident eagles suggested that most (12 of 14) returned to their original territories after relocation 400–500 km away (425). In another study, relocation of migratory eagles as far as 322 km was successful in reducing depredation on a short-term basis (730). However, translocations are expensive and sometimes may only move the depredation problem from one place to another (728). As a consequence of these concerns, translocations are rarely used for management of eagles. Recent rules allow a small number of master falconers to apply for a permit to take, remove, and possess a Golden Eagle suspected of killing livestock (50 CFR 22.24).
Golden Eagle nests have been relocated to move them away from human activity. Nests with broods have been relocated up to 1.4 km in Wyoming to move young from proposed mining areas or from existing mine high walls scheduled for elimination (731, 631). Pairs at relocated nests have been successful for > 20 years (H. Postovit, personal communication).
Rehabilitation of Sick or Injured Animals
Management for individual Golden Eagles can include rehabilitation of sick or injured animals. Wildlife rehabilitation centers treat eagles that have been injured (see Demography and Populations: Causes of Mortality: Free-flying Eagles for summaries from wildlife rehabilitation centers and wild populations). Effective treatments are available for many of these illnesses (732, 733, 673, 569, 603). Recent studies have used point-of-care technologies developed for humans to assess lead poisoning of eagles caught in the course of field research, and to determine when it may be appropriate to remove a sick bird from the wild for treatment before releasing it (673).
Introductions in the Southern Appalachians
Despite good evidence that Golden Eagle has not bred in the southern Appalachians in recent times (190), there have been numerous attempts to release non-migratory eagles into these landscapes. These actions are mistakenly called “reintroductions.”
Efforts to establish exotic nesting populations in the southern Appalachians began in 1981 at the Pisgah National Forest, North Carolina (734). Eagles were subsequently introduced to Tennessee (B. Anderson, personal communication) and Georgia (735). Released birds were either free-flying birds taken to mitigate depredation, young from nests in Wyoming and Colorado, or captive bred. At least one individual hacked in Georgia later successfully fledged 7 young between 1991 and 2000, 5 km from the hacking site (T. Touchstone, personal communication). Another successfully fledged 4 young between 1993 and 1996 in Tennessee > 200 km from the hacking site (B. Anderson, personal communication). Introductions continued in Tennessee until 2006 when the state agency halted them.
There is no evidence that these introduced birds ever became part of the migratory population. However, sporadic nesting appears to continue in the region (TAM, TEK). An adult and juvenile were recorded sitting together on a branch over the Cumberland River in Tennessee in 2010, a recently fledged juvenile was found starving in Tennessee in 2012, and a juvenile was found emaciated in August 2016 in southwestern Virginia. Isotope analysis of a feather from the latter bird was consistent with it growing its first set of feathers in the southeastern United States (D. Nelson, personal communication).
Effectiveness of Measures
Research suggests that reducing eagle exposure to human activity can benefit eagles. One study recommended buffer zones for activity and no-stopping zones for vehicles to protect nesting Golden Eagles (736). Simulation modelling (737) predicts that reducing trail densities or recreation levels use around occupied nests can reduce the frequency of disturbance experienced by Golden Eagles.
Although the effectiveness of closures or disturbance buffers has not been formally evaluated, they likely benefit eagles and numerous state and federal agencies use them to protect nesting eagles from human disturbance. The USFWS and many state agencies suggest restrictions on activity around eagle nests during the nesting season (see examples in Wyoming and North Dakota. Denali National Park and Preserve sometimes restricts human activity near occupied Golden Eagle nests during the nesting season (CLM). Eagle nesting cliffs have been closed to rock climbing on a seasonal basis in in Oregon and Colorado (F. Isaacs, W. Keeley, personal communication). In 2009, the Bureau of Land Management (BLM) permanently closed approximately 75 km of motorized trails to reduce disturbance to nesting Golden Eagles in southwestern Idaho (738), and the BLM implemented seasonal trail closures in 2011 near the most vulnerable territories (739).
Early analyses suggest that detection by automated camera systems may be effective at detecting more eagles than human observers (740).
A successful example of effective local eradication of Golden Eagles via relocation occurred at the Channel Islands, off the southern coast of California. The Golden Eagle had not historically bred or wintered on these islands (741, 742). However, the nesting Bald Eagles that once inhabited the islands were driven to local extirpation by a combination of organochlorine poisoning and persecution. Golden Eagles were first sighted on the islands in the 1980s, and the first nesting attempt was recorded in 1999. The low levels of genetic diversity of these eagles suggested that a small number of colonization events led to the establishment of this population (89). Unlike the Bald Eagles on the island, the Golden Eagles preyed on mammals, primarily feral pigs, but secondarily on other species. Their predation on native and rare island fox (Urocyon littoralis), caused fears that they may cause its extinction. As a consequence, at least 45 Golden Eagles on the Channel Islands were trapped and relocated to mainland California (742). Removal of Golden Eagles from the Channel Islands happened in conjunction with removal of the pigs that provided the most important food source for the birds. Telemetry on a subset of the eagles released in northern California suggested that they did not attempt to return to the islands (741).