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Aquila chrysaetosgolden eagle

By Kari Kirschbaum and Alicia Ivory

Geographic Range

Golden eagles (Aquila chrysaetos) have a Holarctic distribution. They occur throughout Eurasia, in northern Africa, and in North America. In North America, golden eagles are found in the western half of the continent, from Alaska to central Mexico, with small numbers in eastern Canada and scattered pairs in the eastern United States. (Kochert, et al., 2002)

Habitat

Golden eagles are found in open and semi-open habitats from sea level to 3600 m elevation. Habitat types that they inhabit include tundra, shrublands, grasslands, woodland-brushlands, and coniferous forests. Most golden eagles are found in mountainous areas, but they also nest in wetland, riparian and estuarine habitats. (Kochert, et al., 2002)

  • Range elevation
    0 to 3600 m
    0.00 to 11811.02 ft

Physical Description

Golden eagles are North America's largest predatory bird. They are dark brown raptors with long, broad wings. Their length ranges from 70 to 84 cm, and their wingspan ranges from 185 to 220 cm. Males and females are similar in appearance, but females are much larger than males. Female weight ranges from 3940 to 6125 g whereas male weight ranges from 3000 to 4475 g. Adults are largely dark brown, except for a golden area near the crown, nape and sides of the neck and face. The tail is grayish brown. From below, the large flight feathers of the wings appear to be brownish gray, while the head, body and smaller feathers on the forepart of the open wings are blackish. The eyes of adults are dark brown. The bills and claws are black, while the cere and feet are yellow. The legs are feathered all the way down to the toes.

Juvenile golden eagles appear similar to adults, except for light patches on the tips of the wings, and a wide white band on the tail and a terminal band of black. This plumage is sometimes referred to as its "ringtail" plumage as a result of these bands. Juveniles attain adult plumage between ages 4 and 6 years.

There are 5 or 6 recognized subspecies of the golden eagle. These subspecies are differentiated by geographic distribution, size and coloration. Only one subspecies, Aquila chrysaetos canadensis is found in North America. (Kochert, et al., 2002)

  • Sexual Dimorphism
  • female larger
  • Range mass
    3000 to 6125 g
    105.73 to 215.86 oz
  • Range length
    70 to 84 cm
    27.56 to 33.07 in
  • Range wingspan
    185 to 220 cm
    72.83 to 86.61 in
  • Average basal metabolic rate
    4.9929 W
    AnAge

Reproduction

Golden eagles are monogamous, and may maintain pair bonds for several years. In non-migrant populations, pairs appear to stay together year round. For migratory golden eagles, pair formation and courtship begin when the eagles return to the breeding grounds, between February and mid-April. There is no information available regarding whether pair bonds are maintained year-round in migratory populations. Courtship activities in this species include undulating flight by one or both members of the pair, chases, dives, mock attacks, presenting talons, soaring together and circling. (Kochert, et al., 2002)

Golden eagles breed from March through August, depending on their geographic location. Golden eagle pairs in much of the range are sedentary, remaining in the same territory year round. These pairs may begin nest-building and courtship as early as December. For migratory golden eagles, pair formation and courtship begin when the eagles return to the breeding grounds, between February and mid-April. Pairs may have several nests in their breeding territory and often re-use nests year after year, refurbishing them before each breeding season. Golden eagles usually build their nests on cliffs, but may also use trees, riverbanks and man-made structures, such as windmills, observation towers, nest platforms, and electrical towers. Nests are built 0 to 107 m off the ground. Both the male and female of a pair refurbish or build the nest, which may take 4 to 6 weeks. Nests are constructed of sticks and local vegetation and lined with soft vegetation, including shredded yucca, grasses, dry yucca leaves, inner bark, dead and green leaves, mosses and lichens. Nests may be huge if the site allows. The largest nest on record measured 6.1 m tall and 2.59 m wide.

The female lays 1 to 4 (usually 2) eggs, with 3 to 4 day intervals between each egg. The female begins incubating after the first egg is laid, and is responsible for most of the incubation, though the male often takes part. The eggs are dull white and spotted or blotched with brown or reddish brown. Incubation lasts for 35 to 45 days (average 42 days). The young hatch several days apart, and are altricial. The older nestlings are usually much larger than the younger nestlings, and the older, stronger eaglets often kill their smaller siblings. The chicks are brooded by the female with decreasing frequency for the first 45 days or so. Both parents bring food to the nestlings. The nestlings begin to leave the nest between 45 and 81 days of age by walking, hopping or falling out of the nest. They begin to fly around 10 weeks of age, and become independent from the parents 32 to 80 days after fledging. Juveniles do not breed until age 4 to 7 years, after attaining adult plumage. (Kochert, et al., 2002)

  • Breeding interval
    Golden eagles breed once yearly.
  • Breeding season
    Golden eagles breed from March through August, depending on their geographic location.
  • Range eggs per season
    1 to 4
  • Average eggs per season
    2
  • Average eggs per season
    2
    AnAge
  • Range time to hatching
    35 to 45 days
  • Average time to hatching
    42 days
  • Range fledging age
    45 to 81 days
  • Range time to independence
    32 to 80 days
  • Range age at sexual or reproductive maturity (female)
    4 to 7 years
  • Range age at sexual or reproductive maturity (male)
    4 to 7 years

Female golden eagles are primarily responsible for incubation, though males may do some of the incubation. The female also broods the chicks for much of the time in the first 45 days after hatching. Both parents bring food to the nest, though the male provides the majority of food, especially in the first few weeks after hatching. (Kochert, et al., 2002)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

The oldest known golden eagle lived to 46 years in captivity. In the wild, golden eagles have been known to live up to 32 years. (Kochert, et al., 2002)

  • Range lifespan
    Status: wild
    48 (high) years
  • Range lifespan
    Status: captivity
    46 (high) years
  • Average lifespan
    Status: wild
    340 months
    Bird Banding Laboratory

Behavior

Some populations of golden eagles are sedentary, while others are migratory. In North America, most golden eagles in Alaska and Canada travel south in autumn when the food supply on their northern range begins to decline. Most pairs that breed in the continental U.S. and southern Canada remain in the same area year-round.

Golden eagles are generally solitary or in pairs, though non-mated juveniles may be found in groups. Wintering adults may also be found in groups during times of extreme weather or very abundant food.

Golden eagles can carry up to 8 pounds during flight. They can fly up to 80 mph, though the average speed is 28-32 mph, and may reach speeds up to 200 mph in a dive. In flight, golden eagles hold their wings horizontal to the body, rather than at an angle as many other hawks and vultures do. They fly with slow, powerful wingbeats alternated with gliding and soaring. (Kochert, et al., 2002)

  • Range territory size
    22 to 33 km^2

Home Range

Golden eagle home range sizes vary with season and quality of habitat. During the breeding season, golden eagles in the western U.S. have home ranges from 20 to 33 square kilometers. Breeding pairs defend the boundaries of their home range with flight displays. (Kochert, et al., 2002)

Communication and Perception

Golden eagles are mostly silent, except during the breeding season. They use nine different calls to communicate. Most calls appear to be associated with food delivery to nestlings and begging by the nestlings.

Golden eagles don't appear to use vocalizations to mark their territory. Instead, they use an undulating flight to defend the boundaries of their territory. (Kochert, et al., 2002)

Food Habits

The diet of golden eagles is composed primarily of small mammals such as rabbits, hares, ground squirrels, prairie dogs, and marmots. They also eat birds, reptiles and fish in smaller numbers. Golden eagles occasionally capture large prey, including seals (Phocoidea), ungulates, coyotes and badgers. They have also been known to capture large flying birds such as geese or cranes. A pair of eagles will often hunt together; one chases the prey to exhaustion, and the other swoops down for the kill. Golden eagles rarely cache prey for later consumption. (Kochert, et al., 2002)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles
  • fish

Predation

Golden eagles have few predators. There is no record of predation of golden eagle eggs, and few records of adult or nestling predation. Wolverines and grizzly bears are the only recorded predators of golden eagle nestlings. (Kochert, et al., 2002)

Ecosystem Roles

Golden eagles impact the local populations of the animals that they prey on. They may also compete with other species for prey and habitat. For example, golden eagles may compete with bald eagles, coyotes, California condors, and white-tailed eagles for prey items. They most likely also compete with common ravens, gyrfalcons, peregrine falcons, rough-legged hawks and other species for territories. (Kochert, et al., 2002)

Economic Importance for Humans: Positive

Some researchers suggest that golden eagles are beneficial to livestock production because they eat a large number of rabbits, which compete with livestock for forage.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Golden eagles occasionally kill livestock, costing ranchers money.

Conservation Status

The golden eagle is federally protected under the Bald Eagle Protection Act of 1962. In some parts, a decline of golden eagle populations has been recorded. Washington and Montana list it as a species of special concern; and Maine, New Hampshire and New York recognize it as an endangered species. But in other areas they are common and populations are presumably stable. (Tesky, 1994)

Previous to the Protection Act of 1962, some 20,000 golden eagles were killed, mostly from aircraft, because they were thought to prey on yound sheep and goats. But studies in towns where sheep are raised found no evidence to support such claims, as almost 70% of the eagle diet consisted of rabbits. Many golden eagles have been electrocuted in power lines, caught in steel traps set for coyotes and other animals, and poisoned by ranchers. Direct and indirect human-caused mortality, disturbance and elimination of prey by habitat alteration are the main factors limiting golden eagle populations. Recreational activites may also disturb breeding, migration and wintering activities. Golden eagles are likely to abandon nests during incubation if they are disturbed. (Terres, 1980; http://www.fs.fed.us/database/feis/animals/Bird)

Other Comments

Golden eagles are sometimes called the American War Bird or the Bird of Jupiter (Terres, 1980).

Contributors

Kari Kirschbaum (author, editor), Animal Diversity Web.

Alicia Ivory (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

visual

uses sight to communicate

References

Reilly, E. The Audubon Illustrated Handbook of American Birds. McGraw-Hill Book Company, New York, 1968.

Terres, John. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knoph, New York, 1980.

"The Raptor Center, University of Minnesota College of Veterinary Medicine" (On-line). Accessed (Date Unknown) at http://www.raptor.cvm.umn.edu/.

Kochert, M., K. Steenhof, C. McIntyre, E. Craig. 2002. Golden Eagle (Aquila chrysaetos). Pp. 1-44 in A Poole, F Gill, eds. The Birds of North America, Vol. 684. Philadelphia: The Birds of North America.

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