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SUBJ: BRIEFING MEMORANDUM ON THE LIFE HISTORY AND CURRENT THREATS FACING GOLDEN EAGLE POPULATIONS, SPECIFICALLY THOSE IN WESTERN NORTH AMERICA Mike Stoever, Johns Hopkins University TARGET AUDIENCE: This memorandum is intended for the U.S. Fish and Wildlife Service, the National Park Service, and members of the U.S. Senate and House of Representatives. ISSUE: While considered one of the most widely distributed and successful species of eagle in the world, golden eagle populations in western North America have been in decline in recent years. This is primarily due to human activity, with the placement of wind turbines and power lines in migratory paths and a changing climate that is influencing prey availability and habitat suitability being among the biggest impacts to the species. BACKGROUND: One of the largest, fastest, and nimblest predators in North America, the golden eagle (Aquila chrysaetos) is also the most widely distributed, successful species of eagle in the world (ME IF&W 2013, Cornell Lab of Ornithology 2015) Similar in size to its fellow North American raptor the bald eagle, adults in the species have a characteristic dark brown plumage with a golden sheen on the back of the head and neck, while juveniles have distinct white patches at the base of their tail and wings (see Figure 1 in the Appendix; Cornell Lab of Ornithology 2015). Found across most of the Northern Hemisphere, the species requires partially or completely open landscapes that feature native vegetation for habitat, such as the mountains, canyonlands, and riverside cliffs of western North America, where the majority of the continent’s populations reside (see Figure 2 in the Appendix) (Cornell Lab of Ornithology 2015). As an aerial predator, golden eagles require that their nests be built in such a way as to provide unobstructed views of the surrounding landscape. Therefore, nests are often built on cliffs or in the largest trees in forested stands and generally not in densely forested areas (USFWS 2011). The species avoids urban habitats (though they are occasionally found nesting near semi-urban areas where housing density is low), as they are sensitive to certain forms of human presence (USFWS 2011). They possess astonishing speed and maneuverability for their size, able to reach speeds of close to 200 miles per hour when diving to capture prey (Cornell Lab of Ornithology 2015). This ability is enabled by their superior eyesight. For example, a grazing hare may be visible to a golden eagle flying as far as 2 miles (3.2 km) away (Grambo 2003). They mainly prey upon small to medium-sized mammals (with the black-tailed jackrabbit being a key prey species throughout much of their range), reptiles, and birds, and are capable of taking larger prey including mule deer fawns, coyote pups, and cranes (USFWS 2011, Cornell Lab of Ornithology 2015, Kaufman 2016). While primarily a predator, this versatile species is also an adept scavenger. They are known to utilize carrion as well as catch fish, rob nests, and steal food from other birds (USFWS 2011, Cornell Lab of Ornithology 2015). Golden eagles whose breeding sites are located in northern areas migrate south to winter in milder locations beginning in late fall and return in early spring, while those who breed in southern latitudes tend to be resident year-round (Cornell Lab of Ornithology 2015). For those which migrate, the timing of their departure south depends upon the first lasting snowfall, freeze, northern winds, or decreasing prey abundance (USFWS 2011, Cornell Lab of Ornithology 2015). CHALLENGES FACING THE GOLDEN EAGLE: Classified as a species of least concern according to the International Union for Conservation of Nature’s Red List, the golden eagle has displayed generally stable population trends over the past 40 years in North America, with a currently estimated continental population of 40,000 (IUCN 2015, USFWS 2016). However, current data shows the species to be in decline (see Figure 3 in the Appendix; Katzner et al. 2012, USFWS 2016). Although protected by the Bald and Golden Eagle Protection Act, the Migratory Bird Treaty Act, and the Lacey Act, it appears that humans are the primary factor behind this decline (see Figures 4 and 5 in the Appendix). Human activities can result in negative impacts to golden eagles in myriad ways. The species does not tolerate human

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disturbances near nests well, especially near areas that are important for roosting or foraging, as they can stress eagles to a degree that leads to reproductive failure or mortality elsewhere (USFWS 2011, Kaufman 2016). For example, most recorded deaths of golden eagles are due to collisions with wind turbines or other structures placed in their migratory flight paths and from electrocution at power poles, with the former posing a particular problem in the western United States and the latter contributing to 500 deaths yearly (see Figures 6, 7, and 8 in the Appendix; Cornell Lab of Ornithology 2015, Manville 2016, USFWS 2016). Additionally, Zwart et al. (2016) suggest that while hunting, individual golden eagles may not notice wind turbines as they search for and lock into potential prey and thus are placed at higher risk for collisions resulting in mortality. Research has also shown that the reproductive success of migratory golden eagles in northern latitudes is heavily influenced by prey availability early in the nesting season (McIntyre and Adams, 1999). In one such study, nearly 90% of the variation in golden eagle productivity could be explained by changes in the abundance of prey species such as snowshoe hares and willow ptarmigan (McIntyre and Adams 1999). Thus, any decline in prey species such as these (especially when alternate prey are unavailable) is likely to have dire consequences on golden eagle populations. This is an unfortunately foreseeable scenario as anthropogenic activities continue to warm the planet, affecting prey habitats for both golden eagles and their prey (see Figure 9 in the Appendix). Further, golden eagles in many northern breeding areas begin egg laying when mean daily temperatures remain well below 0°C (McIntyre and Adams 1999). As temperatures continue to warm, it is reasonable to expect clutches to be laid at later dates, potentially out of synchrony with the presence of necessary prey sources.

By no means do the challenges facing golden eagles end with migratory impacts and climate change examples given above. They also face habitat fragmentation through deforestation and development; decreased prey abundance due to a variety of human activities; changes in fire regimes (often as a result of human-induced climate change) that have compromised nesting and hunting grounds in southern California and in the sagebrush steppes of the inner West; and lead poisoning due to the consumption of hunter-shot game (Katzner et al. 2012, Sheffield et al. 2012, Cornell Lab of Ornithology 2015). MANAGEMENT/POLICY RECOMMENDATIONS FOR THE GOLDEN EAGLE: As Katzner et al. (2012) noted, the golden eagle is an enigmatic and, for the most part, poorly known species. Similar to what has been suggested by the National Park Service (NPS 2016), it is recommended that additional research be conducted in order to obtain accurate population counts of the species (i.e., to determine whether their numbers are increasing, decreasing, or stable), following the guidelines for a successful conservation strategy put forth by Domenech et al. (2015). Additionally, it has been shown that a disproportionate take of golden eagles by wind turbines is occurring in the western U.S. (Manville, 2016). Therefore, it is recommended that research also be conducted to better document golden eagle take and that any accurate records currently held by federal wildlife management agencies be publicly released. This is especially pertinent as USFWS is in the process of revisiting the regulations for incidental take permits of eagles. As their data have shown, a revising of the allowable incidental take for golden eagles beyond the current level of zero would likely require a mitigating ratio of >1:1 in order to be compatible with the USFWS population objective for the species (USFWS 2016). It is recommended here that until the suggested additional research is completed, the authorized take level remain at zero. As electrocutions from power lines also pose a significant risk to the species, the implementation of newer technology that can prevent or greatly reduce this risk (such as the installation of triangular “Eagle Guards” on crossarms) is highly recommended (DeLong 2004). Finally, as golden eagles are known to occasionally kill livestock such as sheep and goats, it is recommended that when the predation is found to be locally severe (as can occur sheep-producing areas from New Mexico through Montana) and federally permitted frightening and herding techniques are found to be inadequate, any nuisance individuals be captured for translocation using techniques such as firing a net gun from a helicopter (Vercauteren et al. 2012) or using balchatri live traps.

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PROGNOSIS FOR RECOVERY/CONTROL/ERADICATION/SURVIVAL OF THE GOLDEN EAGLE: High, provided the additional research recommended above is conducted (specifically studies that can provide accurate data on population numbers, current trends (i.e., lambda) and migratory patterns) and that future management decisions are then based upon that research. Additionally, efforts at confronting and reducing human-induced climate change must be successful in order to ensure long-term habitat suitability and survival of both the golden eagle and its prey species. ANY FINAL RECOMMENDATIONS/NEEDS/COSTS INVOLVED/NEXT STEPS IN DEALING WITH THE GOLDEN EAGLE: As noted above, further research is necessary in order to ensure that the most efficacious conservation and management strategies are implemented on behalf of the golden eagle. These include studies on population counts; migratory patterns that are then used in the siting of wind turbines and power lines; and the habitat needs of both the golden eagle and its prey species. The growing ramifications of human-induced climate change looms over the continued survival of the golden eagle; thus, attempts at addressing these changes must be undertaken. Finally, appropriate funding for this research and these management strategies is necessary and will need to be made available, covering staff time and equipment (such as that which will be used in GPS telemetry studies, for example). ATTACHMENTS: Appendix Literature cited

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APPENDIX:

FIGURE 1: Differences in golden eagle plumage, ranging from juvenile (at left) to adult (at right). SOURCE: Wheeler 2003.

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FIGURE 2: Distribution of the golden eagle in North America. SOURCE: DeLong 2004.

FIGURE 3: Population status of the golden eagle. SOURCE: Ford 2016

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FIGURE 4: Golden eagle population trajectory changing only mortality rate. Natural mortality is shown in brown, mortality including humans is shown in gray. SOURCE: Ford 2016.

FIGURE 5: Proportion of golden eagle mortality caused by humans. SOURCE: Ford 2016.

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FIGURE 6: Golden eagle flying past a wind turbine. SOURCE: Mernit 2015.

FIGURE 7: Golden eagle killed by a collision with a wind turbine. SOURCE: UW-LaCrosse 2007.

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FIGURE 8: Golden eagle electrocuted by power line. SOURCE: Lockwood 2015.

(a) (b)

(c) (d) FIGURE 9: Golden eagle habitat in the year 2000 (a) and the projected impact of climate change on habitat for the years 2020 (b), 2050 (c), and 2080 (d). SOURCE: Audubon 2016.

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LITERATURE CITED: Audubon. 2016. How climate change could affect the Golden Eagle’s range.

<http://www.audubon.org/field-guide/bird/golden-eagle> Accessed 16 July 2016. Cornell Lab of Ornithology. 2015. All About Birds: Golden Eagle.

<https://www.allaboutbirds.org/guide/Golden_Eagle/id> Accessed 13 July 2016. DeLong, J. P. 2004. Effects of management practices on grassland birds: Golden Eagle. USGS Northern

Prairie Wildlife Research Center, Jamestown, North Dakota, USA. Domenech, R., B. E. Bedrosian, R. H. Crandall, and V. A. Slabe. 2015. Space Use and Habitat Selection

by Adult Migrant Golden Eagles Wintering in the Western United States. Journal of Raptor Research 49(4):429-440.

Ford, J. 2016. Eagle Rule Revisions and Programmatic EIS. <https://www.fws.gov/migratorybirds/pdf/management/Eagle%20Rule%20and%20PEIS%20Release5-3-16-rfl.pdf> Accessed 13 July 2016.

Grambo, R. L. 2003. Eagles. Voyageur Press, New York, New York, USA. Katzner, T., B. W. Smith, T. A. Miller, D. Brandes, J. Cooper, M. Lanzone, D. Brauning, C. Farmer, S.

Harding, D. Kramar, C. Koppie, C. Maisonneuve, M. Martell, E. K. Mojica, C. Todd, J. A. Tremblay, M. Wheeler, D. F. Brinker, T. E. Chubbs, R. Gubler, K. O'Malley, S. Mehus, B. Porter, R. P. Brooks, B. D. Watts, and K. L. Bildstein. 2012. Status, biology and conservation priorities for North America's eastern Golden Eagle (Aquila chrysaetos) population. The Auk 129(1):168-176.

Kaufman, K. 2016. Guide to North American Birds: Golden Eagle. National Audubon Society, New York, New York, USA.

Lockwood, B. 2015. Image of Golden Eagle Electrocuted by Power Line. <http://ornithologyexchange.org/articles/_/community/usfws-to-issue-programmatic-environmental-impact-statement-on-incidental-take-of-mbta-species-r203> Accessed 17 July 2016.

McIntyre, C. L. and L. G. Adams. 1999. Reproductive Characteristics of Migratory Golden Eagles in Denali National Park, Alaska. The Condor 101(1):115-123.

Maine Department of Inland Fisheries and Wildlife (ME IF&W). 2013. Wildlife: Golden Eagle. <http://www.maine.gov/ifw/wildlife/species/birds/golden_eagle.html> Accessed 15 July 2016.

Manville, A. M. II. 2016. Impacts to Birds and Bats Due to Collisions and Electrocutions from Some Tall Structures in the United States: Wires, Towers, Turbines, and Solar Arrays—State of the Art in Addressing the Problems. Pages 415-442 in F. M. Angelici, editor. Problematic Wildlife: A Cross-Disciplinary Approach. Springer International Publishing, Switzerland.

Mernit, J. L. 2015. Green energy’s dirty secret. <https://www.hcn.org/issues/47.18/green-energys-dirty-secret> Accessed 16 July 2016.

National Parks Service (NPS). 2016. Glacier National Park: Birds. <https://www.nps.gov/glac/learn/nature/birds.htm> Accessed 14 July 2016.

Sheffield, S. R., J. P. Sulllivan, and E. F. Hill. 2012. Identifying and Handling Contaminant-Related Wildlife Mortality or Morbidity. Pages 154-180 in N. J. Silvy, editor. The Wildlife Techniques Manual. Volume 1. Seventh Edition. The Johns Hopkins University Press, Baltimore, Maryland, USA.

U.S. Fish and Wildlife Service (USFWS). 2011. Golden Eagle Fact Sheet. <https://www.fws.gov/migratorybirds/pdf/management/golden-eagle-fact-sheet.pdf> Accessed 15 July 2016.

USFWS. 2016. Bald and Golden Eagles: Population demographics and estimation of sustainable take in the United States, 2016 update. Division of Migratory Bird Management, Washington, D.C., USA.

University of Wisconsin, LaCrosse (UW-LaCrosse). 2007. The Amazing Aquila chrysaetos; Golden Warrior of the Sky. <https://bioweb.uwlax.edu/bio203/f2013/bjorklun_luke/facts.htm> Accessed 17 July 2016.

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Vercauteren, K. C., R. A. Dolbeer, and E. M. Gese. 2012. Identification and Management of Wildlife Damage. Pages 232-269 in N. J. Silvy, editor. The Wildlife Techniques Manual. Volume 2. Seventh Edition. The Johns Hopkins University Press, Baltimore, Maryland, USA.

Wheeler, B.K. 2003. Raptors of Western North America. Princeton University Press, Princeton, New Jersey, USA.

Zwart, M. C., A. J. McKenzie, J. Minderman, and M. J. Whittingham. 2016. Conflicts Between Birds and On-Shore Wind Farms. Pages 489-504 in F. M. Angelici, editor. Problematic Wildlife: A Cross-Disciplinary Approach. Springer International Publishing, Switzerland.