Golden Eagle - Aquila chrysaetos
Adults are brown overall, gold on head and neck feathers, with light brown bands in the tail. Immature birds have white patches on the wings and white at the base of the tail feathers. Golden Eagles often soar with their wings held nearly flat, but slightly upturned. The legs are heavily feathered down to the tops of the toes. Golden Eagles range in length from 33 to 38 inches, and have a wingspan of 6-1/2 to 7-1/2 feet. A very large raptor with mostly brown plumage, a golden wash on the back of the head and neck, and a mostly horn-colored bill; tail is faintly banded; immatures have white at the base of the primaries and and white tail with a dark terminal band; total length 76 to 102 cm, wingspan 203 to 224 cm.
Bald Eagles have feathers only part way down the leg, and usually soar with wings held completely flat. Immature Bald Eagles usually have a strip of white along the underside of the wing, rather than in a round patch on the flight feathers like the immature Golden Eagle. Older immature Bald Eagles have irregular patches of white on their bodies, instead of the sharply defined patterns on Golden Eagles. Turkey Vultures soar with wings held in a more pronounced "V".
Breeds throughout western North America from the Arctic to central Mexico; some breeding also occurs in northern Ontario and Labrador, and on the Gaspe Peninsula of southeastern Quebec. Northern birds (north of southern British Columbia, Alberta, and Saskatchewan) move south in the non-breeding season.
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
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(direct evidence "B")
(indirect evidence "b")
No evidence of Breeding
(regular observations "W")
(at least one obs. "w")
(Records associated with a range of dates are excluded from time charts)
Permanent resident, but migratory movements documented. Migrants were sampled in the Bridger Mountains during 13 September to 27 October (Hoffman and Smith 2003), with an average of 1534 individuals passing through this site each autumn during 1992-2001; there was a slight decline in numbers over the entore sampling period. Some Golden Eagles remain year-round, but vertical migration seen in spring and fall (Skaar 1969). One eagle banded as a nestling near Livingston was shot 1290 miles distant near Kerrville, Texas (McGahan 1968). Three Golden Eagles banded in Montana were reencountered in Montana within 2 miles of where banded six months to four years after banding (Harmata 2002). In a 1991 study of fall migration along the Bridger Range, Omland and Hoffman (1996); concluded that immature Golden Eagles migrated earlier in the season than adults; immatures also spent more time each day migrating and/or were less selective about the time of day during which they migrated than adults. Further, the authors found no evidence of visual interaction among migrating Golden Eagles.
Golden Eagles nest on cliffs and in large trees (occasionally on power poles), and hunt over prairie and open woodlands; some nest sites in the Fallon area include scoroacious badland pillars (Cameron 1905), another near Knowlton was in a ponderosa pine (Cameron 1907). In the Livingston area 62% of 92 nests were on cliffs, 29% in Douglas-fir, and 2-3% each in ponderosa pine, cottonwood, snags, and on the ground (McGahan 1968). About 70% of cliff nests were oriented to the south or east, most nests were found between 4000-6000 ft elevation, and sites were associated with sagebrush/grassland hunting areas (McGahan 1968). In the Bozeman area, Golden Eagles move from mountains to valleys in the winter (Skaar 1969).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at email@example.com
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Open Water / Wetland and Riparian Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
In Montana, Golden Eagles eat primarily jackrabbits, ground squirrels, and carrion. They occasionally prey on deer and Pronghorn (mostly fawns), waterfowl, grouse, weasels, skunks, and other animals. In the Livingstone area, diet included two species of lagomorph, seven species of rodent, two species of small carnivore (mustlids), three species of ungulates (fawns), 15 species of birds, and two species of snakes; of 980 prey items, 87% were mammals, and 80% of the mammals were lagomorphs (jackrabbits and cottontails) (McGahan 1968). In the Fallon area, jackrabbits, cottontails, wood rats, Sharp-tailed Grouse, meadowlarks, and rattlesnakes were noted at eyries (Cameron 1905), mostly prairie dogs at a nest near Knowlton (Cameron 1907), and carrion during winter. Above treeline they are thought to hunt mostly yellow-bellied marmots (Pattie and Verbeek 1966). Golden Eagles sometimes prey on livestock, especially lambs (Arnold 1954), but when they do, losses usually occur in localized areas where migrating eagles congregate. Golden Eagles can carry no more than about seven pounds while flying.
Nesting density varies year to year from 55 to 105 square miles/pair. Some cliff nest sites are used for many decades, maybe even centuries (Ellis et al. 2009). Golden Eagles move to higher elevations after leaving the nest (Baglien 1975). During a two-year study in the Livingston area, density varied from 66.3 to 74.2 square miles/pair (McGahan 1968). BBS data for Montana show non-significant annual increases of 1.0% per year during 1966-2009 and 1.7% per year for 1999-2009; survey-wide the equivalent values are non-significant increases of 0.2% per year and 1.2% per year. CBC data for Montana during the winters of 1979-80 to 2009-10 show a high total count of 124 (0.156/party hour) on 27 counts in 1999-2000, and a low total count of 30 (0.039/party hour) on 9 counts in 1980-81. The mean annual total count for the 31-year period was 79, with numbers/party hour showing a gradual increase.
Golden Eagles first breed when four to five years old. In the Bozeman area, courtship flights reported 14 February to 26 April (Skaar 1969), 25 February through March in the Knowlton area (Cameron 1907). The same pair often uses the same nest year after year; nests are sometimes over six feet in diameter. A nest on a basalt cliff near Sun River, and in use long before 1972 (when it was nearly 6 m tall), was 7 m (23 ft) tall in 2004, the tallest nest reported for any bird species; a twig from the base of the nest grew during 1414 to 1444 AD as determined by radiocarbon dating (Ellis et al. 2009). One to three eggs are laid in March or April; a nest near Knowlton in eastern Montana had 2 eggs on 1 April (Cameron 1907). Incubation lasts about 45 days. In the Livingston area, 5% of 20 clutches had a single egg, 80% 2 two eggs, and 15% three eggs (McGahan 1968). The eaglets fly in June or July when about 10 weeks old. Eggs layed early April, hatch mid-May, fledge mid-July to early August. In south-central MT, clutch average is 2.1, with circa 1.5 eaglets fledged per successful eyrie, and circa 76% of nests successful (McGahan 1966, Reynolds 1969).
Management of healthy Golden Eagle populations requires maintaining prey habitat where eagles forage. This involves sustaining native grasslands and shrub-steppe landscapes which are the prime habitats for jack rabbits. Shrub communities should be protected within 3 km of nests, which can be maintained through fire suppression and through shrub restoration. Hacking can be used to reestablish eagles where they have been eliminated in the past. Power poles can be designed and built to reduce the likelihood of electrocution. Use of scarecrows and harassment may be methods useful to protect lambs from eagles (Kochert et al. 2002).
Threats or Limiting Factors
Shooting, trapping, and ingestion of poisoned bait have been significant threats in the past (Cameron 1905), shooting and poisoning from the ingestion of lead fragments in carrion remain as threats (Harmata and Restani 1995, Kochert et al. 2002). Collisions with wind turbines and electrocutions from high voltage powerlines also continue to present significant threats. At least 28-43 eagles were killed annually by turbine blade strikes at the Altamont Pass area, California during 1994-1997, while during 1998-2003 the estimated annual mortality was 67 (Smallwood and Thelander 2008). During 1986-1996 at least 272 Golden Eagles were electrocuted in western North America (Harness and Wilson 2001, Kochert et al. 2002); 54% of 61 bird electrocutions reported in Montana during 1980 to 1985 were Golden Eagles (O'Neil 1988).
- Literature Cited AboveLegend: View WorldCat Record View Online Publication
- Arnold, L.W. 1954. The golden eagle and its economic status. Circular 27:1-35.
- Baglien, J. W. 1975. Biology and habitat requirements of the nesting golden eagle in southwestern Montana. M.S. thesis. Montana State University, Bozeman.
- Cameron, E. S. 1905. Nesting of the golden eagle in Montana. Auk 22:158-167.
- Cameron, E. S. 1907. The birds of Custer and Dawson Counties, Montana. Auk 24(3):241-271.
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- Harmata A. and M. Restani. 1995. Environmental contaminants and cholinesterase in blood of vernal migrant bald and golden eagles in Montana. Intermountain Journal of Sciences 1:1-15.
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- Harness, R.E. and R.W. Kenneth. 2001. Electric-utility structures associated with raptor electrocutions in rural areas. Wildlife Society Bulletin 29(2): 612-623.
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- McGahan, J. 1966. Ecology of the golden eagle. M.S. thesis. University of Montana, Missoula. 78 pp.
- McGahan, J. 1968. Ecology of the golden eagle. Auk 85:1-12.
- O'Neil, T. A. 1988. Analysis of bird electrocutions in Montana. Journal of Raptor Research 22:27-28.
- Omland, K. S. and S. W. Hoffman. 1996. Seasonal, diet, and spatial dispersion patterns of golden eagle autumn migration in southwestern Montana. The Condor 98:633-636.
- Pattie, D.L. and N.A.M. Verbeek. 1966. Alpine birds of the Beartooth Mountains. Condor 68: 167-176.
- Reynolds, H. U., III. 1969. Population status of the golden eagle in southcentral Montana. M.S. thesis. University of Montana, Missoula. 93 pp.
- Skaar, P.D. 1969. Birds of the Bozeman latilong: a compilation of data concerning the birds which occur between 45 and 46 N. latitude and 111 and 112 W. longitude, with current lists for Idaho, Montana, Wyoming, impinging Montana counties and Yellowstone National Park. Bozeman, MT. 132 p.
- Smallwood, K. and C. Thelander. 2008. Bird mortality in the Altamont Pass Wind Resource Area, California. The Journal of Wildlife Management 72(1): 215-223.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
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