Status, biology, and conservation priorities for North America's eastern Golden Eagle (<i>Aquila chrysaetos</i>) population

THE GOLDEN EAGLE (Aquila chrysaetos) population in North America is declining (Hoffman and Smith 2003, Smith et al. 2008). This species is enigmatic, indicative of broad conservation value (Sergio et al. 2005), and, for the most part, poorly known. Populations west of the Mississippi River in the lower 48 states number approximately 21,000–35,000 individuals (Good et al. 2004, 2007). However, this estimate is based on limited sampling effort and on broad-scale extrapolation to unsampled habitats, and it does not include Canadian or Alaskan birds. A much smaller population, which has been estimated at 1,000–2,500 individuals, exists east of the Mississippi River. These “Eastern Golden Eagles” were almost completely unknown to ornithologists until the 1930s, when significant numbers were first reported migrating south past Hawk Mountain Sanctuary (Broun 1935). Today, there still is little information on the basic ecology, demography, and size of this population. What is known suggests declines over the past century and recent (1974–2004) short-term increases (Farmer et al. 2008a). In response to apparent ongoing Golden Eagle population declines, the U.S. Fish and Wildlife Service (USFWS) is now re-evaluating its interpretation of the Bald and Golden Eagle Protection Act (BGEPA) to more effectively manage this species. The USFWS has recognized that Golden Eagle populations east of the Mississippi are different and less well understood than others in North America. Currently, the USFWS is not issuing permits for take of Golden Eagles east of 100°W longitude (USFWS 2009). This is because of the small number, potentially high demographic vulnerability, and geographically specific conservation problems confronting birds in the East. For example, although wind turbines are a known source of eagle mortality in the western United States (Smallwood and Thelander 2008) and are thought to be a growing threat elsewhere, no Golden Eagles have been reported killed by turbines in the East. By contrast, biologists in the East consider incidental trap mortality and lead poisoning to be among the most serious threats to eagles (T. Katzner and C. Maisonneuve pers. obs.). Here we review the status, biology, threats, and conservation priorities for the eastern population of Golden Eagles. This commentary is an effort of the recently formed Eastern Golden Eagle Working Group (EGEWG), an international collaborative effort among scientists and managers from across eastern North America. The vision of the EGEWG is to ensure the long-term sustainability of Eastern Golden Eagle populations, ultimately making the species a flagship species for conservation. The group's objectives include (1) collaboratively identifying gaps in knowledge and management about Eastern Golden Eagles; (2) prioritizing species-specific research needs for this geographic region; (3) promoting science-based conservation and management actions based on our collective research; (4) increasing public and governmental awareness about Eastern Golden Eagles, their biology and conservation status, and the need for their protection across their range; and (5) coordinating the activities of managers and biologists working with Golden Eagles in the East. Dates of earliest records and last known resident, breeding, and successful breeding by Golden Eagles in eastern North America. Table does not include states where records are questionable or breeding in the southern Appalachian Mountains by translocated or hacked birds (see text for details). Dates of earliest records and last known resident, breeding, and successful breeding by Golden Eagles in eastern North America. Table does not include states where records are questionable or breeding in the southern Appalachian Mountains by translocated or hacked birds (see text for details). Historical context.—Golden Eagles historically bred in eastern Canada (Ontario, Quebec, and Labrador) and the northeastern United States (Table 1). Breeding records for the species in New England and New York date back hundreds of years. However, in spite of historical summer observations from the southern Appalachian Mountains, there is scant evidence of Golden Eagles breeding south of New York (Lee and Spofford 1990; we consider Beck's [1924] record from Pennsylvania to be of questionable value). Notwithstanding the paucity of historical breeding data, there have been repeated translocations, releases, and hackings in an attempt to “re-establish” breeding Golden Eagles in the southern Appalachians. Presumably these activities, which occurred between 1930 and 2005, were permitted at the state and federal levels. Known present status, distribution, and trends.—The Golden Eagle population in eastern North America has undergone long-term declines over the past century (Bednarz et al. 1990), with an apparent recovery since the end of the DDT era (Farmer et al. 2008a, b). In eastern Canada, populations presently are considered “stable,” and breeding pairs are most numerous in Quebec, with less-well-known and presumably smaller populations in Labrador and Ontario (Tables 1 and 2). There are no breeding records and only occasional migration-season reports from insular Newfoundland or the Maritime Provinces (Tuck 1968). Populations of Golden Eagles in northern New England have been more closely monitored, and their declines are relatively well documented. Maine and New York supported territorial breeding Golden Eagles until the late 1990s, and most of the remainder of New England also once supported breeding pairs (Table 1). These populations have all been extirpated. Nesting attempts also were documented in north-central Tennessee and northwestern Georgia in the 1990s following the previously mentioned hacking and translocation efforts (S. Somershoe and J. Ozier pers. comm.). Golden Eagles wintering in the East are found in Appalachian high country, but sightings are recorded regularly in other regions (e.g., western Tennessee and Kentucky; the Virginia, Delaware, and North and South Carolina Coastal Plains; and the Okefenokee National Wildlife Refuge in Georgia; Millsap and Vanna 1984). There are no breeding records for this species from Minnesota, Wisconsin, Michigan, or Iowa. In all four states, there are widespread spring, fall, and winter records from most counties (Roberts 1932, Granlund et al. 1994, Kent and Dinsmore 1996, Mueller and Kowalchuk 2009). Kent and Dinsmore (1996) noted that the average number of winter records reported annually in Iowa rose steadily, from an average of 2.2 in the 1960s to 3.1 in the 1970s, 7.1 in the 1980s, and 11.0 in the 1990s. Millsap and Vana (1984) considered Crex Meadows Wildlife Area in Wisconsin (7 records from 1963–1977) and Crab Orchard National Wildlife Refuge in Illinois (5 records from 1957–1980) as “regular wintering sites.” Records of Golden Eagles on fall migration over Hawk Ridge in Duluth, Minnesota, date back to 1951 (Hofslund 1966). Breeding-season ecology.—Like their counterparts in Alaskan and western Canadian populations, Eastern Golden Eagles are migratory (Morneau et al. 1994, Watson 2010). Nests are built primarily on cliffs but are sometimes found in trees in the Gaspé Peninsula of southeastern Quebec and in northern Ontario (Lumsden 1964, Brodeur and Morneau 1999). Breeding habitat use by Golden Eagles in eastern North America is diverse and consistent with that of some other populations of this species (Kochert et al. 2002). In northern Quebec, Ontario, and Labrador, breeding birds are found at the interface of tundra, boreal forest, and wet meadows, often on the edge of, but generally avoiding, heavily forested areas (Fig. 1). On the Gaspé Peninsula and in the former U.S. breeding range, nests are in forested habitats but eagles forage in open landscapes created by disturbances and wetlands (J. A. Tremblay and C. Maisonneuve pers. obs.). In the Hudson Bay region of northern Quebec, home range varied from 846 to 1,585 km2 (minimum convex polygon, June– October, n = 3; Brodeur 1994). In the Gaspé Peninsula, breeding home ranges varied from 515 to 2,132 km2 (fixed kernel estimator, n = 3; J. A. Tremblay and C. Maisonneuve unpubl. data). The few published historical data on the diet of breeding Golden Eagles in eastern Canada suggest that they feed on birds (particularly waterfowl and wading birds) with greater frequency than do eagles in western North America (Spofford 1971a, Brodeur and Morneau 1999). From late autumn to early spring, Golden Eagles are regularly observed feeding on carrion—Caribou (Rangifer tarandus), Moose (Alces alces), and White-tailed Deer (Odocoileus virginianus) (Todd 1940, Spofford 1971a, Singer 1974). Migration ecology.—Fall migration from northern breeding grounds starts as early as mid-August, although the bulk of migration is from mid-October through mid-December (mean migration dates = 19 October ± 4.4 days to 22 November ± 3.8 days; n = 12 complete telemetry tracks). Spring migration is shorter, extending from late February to mid-May, with the majority of movements occurring during a single week in mid-March (mean starting migration date = 18 March ± 3.4 days; n = 22, including partial tracks; ending date = 4 April ± 5.6 days; n = 10 complete tracks). Golden Eagles in eastern North America appear to engage in “leapfrog migration” (Baker 1978) and follow one of several autumn migratory pathways (Fig. 1). The majority of birds from northern Quebec and Labrador migrate west of the Gulf of St. Lawrence, cross the St. Lawrence River just to the southwest of Montreal, pass through central New York and into the parallel ridges of eastern and central Pennsylvania, western Maryland, and eastern West Virginia to inland wintering grounds (routes A and B; Fig. 1). Some younger birds apparently leave, or “overshoot,” the ridges and end up on the Atlantic Coast (route C; Fig. 1). Birds that summer on the Gaspé migrate mainly through New England (route D; Fig. 1). Because these individuals winter mainly in New York and Pennsylvania, they may not be counted at raptor migration watch sites. Finally, hawk migration count data suggest that 15–25% of eastern Canada's Golden Eagles migrate through the Great Lakes region. Telemetry data indicate that these birds migrate west of Lake Erie (routes E, F, and G; Fig. 1) (Brodeur et al. 1996, Mehus and Martell 2010). Migratory routes of individuals summering in Ontario are unknown, but these may contribute disproportionately to the Midwestern wintering population. Distribution of Eastern Golden Eagles, showing known summer and wintering grounds as well as known and suspected southbound migration corridors. Areas where distribution is unclear are indicated with a question mark (open on breeding grounds, filled on wintering grounds). Letters correspond to different suspected southbound migration routes that are described in greater detail in the text. Spring migration routes are less well known than fall routes. Most of the known routes cross through the western Appalachian Ridge and Valley Province, the Allegheny Plateau and the Adirondack region, with birds crossing into Canada via southern Quebec (Brandes and Ombalski 2004). Spring migration routes in the Great Lakes region are poorly known but include movements along the western edge of Lake Superior and the southern shore of Lake Ontario (www.hawkcount.org). Winter ecology.—Telemetry and camera-trapping data suggest that Golden Eagles are found in greatest numbers during winter in the north-central Appalachian Mountains of Pennsylvania, West Virginia, and Virginia (T. Miller and T. Katzner unpubl. data). Birds are regularly reported in the mountains of neighboring states (Kentucky, Tennessee, North Carolina, and New York), as far north as southern Quebec and as far south as Alabama. Likewise, a small portion of the population winters in the Piedmont and Coastal Plains of several eastern and southeastern states, and in the “driftless” (i.e., unglaciated) area of the upper Mississippi River Valley. Habitat use, relative density, and the overall distribution of these eagles during winter are poorly understood and of high priority for future study. Preliminary observations suggest that winter home ranges of Golden Eagles in eastern North America vary dramatically (13–33,553 km2; kernel density estimator, n = 11 birds), the smallest home range being in the mid-Atlantic Coastal Plain and the largest in the Appalachian Highlands of Kentucky and West Virginia (D. Kramar et al. unpubl. data). In the mountains, birds used large blocks of woodlands most heavily, with 74% of tracking data points found in forested habitat (U.S. Geological Survey, Gap Analysis Program 2010). The remaining observations were in agricultural, disturbed, and wetland areas. Demography.—Numbers of breeding Eastern Golden Eagles are highest in Quebec, where most of the estimated 300 to 500 breeding pairs nest above 50°N (Brodeur and Morneau 1999, J. A. Tremblay and C. Maisonneuve unpubl. data). Dispersion of breeding territories in the northern part of the range is largely unknown. On the Gaspé Peninsula in the south, nests are spaced at approximately 13–20 km, generally far apart for Golden Eagle territories (e.g., Watson 2010), which suggests that habitat in the region is of low quality for this species. Known reproductive output of eagles is low and varies from 0.17 to 1.17 nestlings per occupied territory per year in the Côte-Nord area (F. Morneau et al. submitted) to approximately 0.33 to 0.67 nestlings per known occupied territory per year in the Gaspé Peninsula (J. A. Tremblay and C. Maisonneuve unpubl. data). There are probably fewer than 50 territories each in Labrador (T. Chubbs unpubl. data) and Ontario (Ontario Breeding Bird Atlas; www.birdsontario.org). The most robust and longest-term estimates of population trends come from counts at migration watch sites in the central Appalachians of Pennsylvania and southern New York. Evidence suggests long-term declines in counts of eastern North America's Golden Eagle populations from the 1930s through the mid-1980s, followed by short-term increases after the banning of DDT (Bednarz et al. 1990, Titus and Fuller 1990). Hussell and Brown (1992) noted no change in autumn counts in Minnesota from the mid-1970s to late 1980s but a simultaneous significant annual increase of 8% in spring counts in Ontario. Over the 30-year period between the mid-1970s and 2004, most eastern hawk counts show significant annual increases of 2–5% (Farmer et al. 2008a). Finally, recent short-term trends are largely positive, with significant 2–6% annual increases from 1994 to 2004, although there also are nonsignificant indications of declines in counts in the eastern Great Lakes and Quebec (Farmer et al. 2008b). Genetics.—Populations of Eastern Golden Eagles exhibit some degree of geographic isolation from their western counterparts and historically may have been genetically distinct. However, the recent history of repeated reintroduction of western birds in the southern Appalachians may have compromised the integrity of the eastern gene pool. Beginning in 1984, 111 nestlings, mostly from Wyoming, were hacked into Georgia (Touchstone 1997). In another effort from 1980 to 1986, multiple agencies, including the Tennessee Valley Authority, the USFWS, and the North Carolina Wildlife Resources Commission coordinated the release of 24 western nestlings into North Carolina (Roberts 1985, C. Kelly et al. pers. comm.). Forty-seven captive nestlings were hacked into Tennessee by private organizations from 1995 to 2006; at some of these birds were observed to in central Tennessee (S. Somershoe pers. comm.). Finally, at birds of unknown but presumably western U.S. were into Pennsylvania from to (T. pers. comm.). Preliminary of some into of North Golden Eagle populations and unpubl. data). Analysis of 10 with the = suggests no population between eastern and western North Golden Eagles. of pairs of the gene no between 12 western and eastern birds. with the greatest occurring between eastern birds. There one by western and eastern birds. in this include (1) more geographic populations and (2) including historical from to population may have been by past and ornithologists migration of large numbers of Golden Eagles along the Appalachian Mountains and the Great Lakes (e.g., in the research and the public largely that the species and winters in eastern North America. vary in their awareness and published of the conservation of this Golden Eagle population, in the central and southern Appalachian Mountains (Table 2). Most eastern Wildlife are breeding Golden Eagles are recognized in only of Golden Eagles are as a in of in a conservation for are and Eagles in eastern North America are generally little U.S. or Canadian federal protection that of the Migratory Bird Act and, in the United (Table 2). In the eastern United Golden Eagles have in only of In eastern Canada, of four a for this population (Table 2). the U.S. federal and are the that Golden Eagles from take is as or individuals, their nests and In the Bald Eagle from the Act in the USFWS a to and a described as or a Bald or Golden Eagle to a degree that to an or nest In a to take including and or take of nests where to a to or to ensure public and to to a or where the or for the a to The a where take of eagles be with the that the take is with of the as with the of or increasing breeding Eastern Golden Eagles and threats include incidental and threats are largely to habitat in from habitat and the demographic of in population from in and for have been known for more than a century as a source of mortality for Golden Eagles in eastern North America In the to Quebec, West Virginia, and Virginia each reported multiple incidental reported per Brodeur and Morneau 1999). of in Quebec that the number of birds killed may be that reported et unpubl. between and at of known Golden Eagle in the United States from et al. another in the East The demographic of these threats, or is all but unknown. and with that are the known of mortality for Golden Eagles in the western United States et al. unpubl. data). increasing numbers of wind at high in breeding, and wintering Golden Eagles in eastern North America have and and several poisoning from of lead in is of high for Golden Eagle populations and 1997). lead has been in most states and lead is still used to and lead are still used for Golden Eagles in the northwestern United States lead in at the end of the et al. 2010). Likewise, numerous Bald and Golden eagles in the and to in eastern North America have lead of Virginia of Virginia of and unpubl. data). lead poisoning may eagles to to other threats, and have to Golden Eagle population in the northeastern United States (Todd Records from Maine show that territorial eagles on and that DDT (Spofford in of and of reproductive (Todd Finally, with for other (e.g., Golden Eagles in the western United States and, may Golden Eagles in the East as well et al. 1984, and 2002). the threats to habitat on and southern breeding of the greatest Habitat in present by including that for wind and (i.e., from and of Eastern Golden Eagles a of their about this population include the large is the What is its do distribution and quality of and habitat reproductive output and What migration do these birds use and which of these routes are most to do and to where do they is also to and on this species. areas of conservation are (1) of and for of wind and other (2) the degree to which and lead from lead are to (3) the demographic of incidental take from in and and (4) of habitat on eagle habitats and for Eastern Golden Eagles on threats from lead and as well as habitat conservation is well documented that wind turbines including Golden Eagles 2002). The most for turbines in in the and other that as annual migration or are used for or areas. the USFWS National that an or and Protection for with the Migratory Bird recently have been published in (USFWS the to and of eagles by wind USFWS also has a Eagle (USFWS that a for avoiding, and eastern states and also have for wind as it to the take of migratory including Golden Eagles, although in all these are apparently may be for this at the and Canadian federal the threats to Eastern Golden Eagle populations by and to small are now to the of protection in several This is because state conservation and because they federal when the former are more than the However, these at all not the research to the basic history and of this population. Finally, the historical distribution of Golden Eagles in eastern North America and the of translocation we that or of western Golden Eagles into states east of the Mississippi be Eastern Golden Eagles appear to be a of a declining North population that is at from threats on breeding, and wintering growing in the range, Canadian and U.S. are re-evaluating management for its Historical knowledge about Golden Eagle populations in the East is relatively complete in a few areas with to migration count it is in information on basic geographic distribution, demography, ecology, and ornithologists are of the of and threats to Eastern Golden Eagles. This commentary is to the knowledge about this population, increase its for and to the threats these birds the for their of the that to this for the by the Virginia of and and the Hawk Mountain Sanctuary from and the This is Hawk Mountain Sanctuary to conservation number

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