Golden Eagle

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Golden Eagle
In flight in Spain
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Aquila
Species: A. chrysaetos
Binomial name
Aquila chrysaetos
(Linnaeus, 1758)
Light brown : Wintering only

Brown : Breeding only
Dark brown : All-year
Synonyms

Falco chrysaëtos Linnaeus, 1758

The Golden Eagle (Aquila chrysaetos) is one of the best known birds of prey in the Northern Hemisphere. Like all eagles, it belongs to the family Accipitridae. Once widespread across the Holarctic, it has disappeared from many of the more heavily populated areas. Despite being extirpated from or uncommon in some its former range, the species is still fairly ubiquitous, being present in Eurasia, North America, and parts of Africa. The nesting density for a breeding population near Livermore, California and the Altamont Pass Wind Farm is among the highest in the world for Golden Eagles.[2][3] These birds are dark brown, with lighter golden-brown plumage on their heads and necks.

Golden Eagles use their agility and speed combined with extremely powerful talons to snatch up a variety of prey, including rabbits, marmots, ground squirrels, and large mammals such as foxes and young ungulates.[4] They will also eat carrion if live prey is scarce, as well as reptiles. Birds, including large species up to the size of swans and cranes have also been recorded as prey. For centuries, this species has been one of the most highly regarded birds used in falconry, with the Eurasian subspecies having been used to hunt and kill unnatural, dangerous prey such as Gray Wolves (Canis lupus) in some native communities. Due to their hunting prowess, the Golden Eagle is regarded with great mystic reverence in some ancient, tribal cultures.

Golden Eagles maintain territories that may be as large as 155 km2 (60 sq mi). They are monogamous and may remain together for several years or possibly for life. Golden Eagles nest in high places including cliffs, trees, or human structures such as telephone poles. They build huge nests to which they may return for several breeding years. Females lay from one to four eggs, and both parents incubate them for 40 to 45 days. Typically, one or two young survive to fledge in about three months.

Contents

Description

In flight
Subadult, note white in tail and dark neck

The Golden Eagle is a large, dark brown raptor with broad wings. Its size is variable: it ranges from 66 to 102 cm (26 to 40 in) in length and it has a typical wingspan of 1.8 to 2.34 m (5.9 to 7.7 ft). In the largest race (A. c. daphanea) males and females weigh 4.05 kg (8.9 lb) and 6.35 kg (14.0 lb). In the smallest subspecies (A. c. japonensis), the sexes weigh, respectively, 2.5 kg (5.5 lb) and 3.25 kg (7.2 lb).[4][5][6][7][8] In the species overall, males average around 3.6 kg (7.9 lb) and females average around 5.1 kg (11 lb).[9] The maximum size of this species is a matter of some debate, although the normal upper weight limit for a large female is around 6.8 kg (15 lb) and large races are the heaviest representatives of the Aquila genus.[10] Captive birds have been measured up to a wingspan of 2.81 m (9.2 ft) and a mass of 12.1 kg (27 lb) (the latter figure was for an eagle bred for the purposes of falconry).[10] The standard measurements of the species include a wing chord length of 52–72 cm (20–28 in), a tail length of 26.5–38 cm (10.4–15 in) and a tarsus length of 9.4–12.2 cm (3.7–4.8 in).[6] The culmen reportedly averages around 4.5 cm (1.8 in), with a range of 3.6 to 5 cm (1.4 to 2.0 in) and the bill from the gape measures around 6 cm (2.4 in).[11][12] The sexes are similar in plumage but are considerably dimorphic in size, with females rather larger than males.[13] Adults are primarily brown, with a pale gold color on the back of the crown and nape, and some grey on the wings and tail.[14] Tarsal feathers range from white to dark brown. In addition, some birds have white "epaulettes" on the upper part of each scapular feather tract.[15] The bill is dark at the tip, fading to a lighter horn color, with a yellow cere.[16]

Juveniles have a darker, unfaded color, white patches in the remiges which may be divided by darker feathers,[17] and a large amount of white on the tail with a black terminal band.[13] Occasionally upper wing feathers of juveniles are also white, or birds lack white on the wing entirely. As the bird ages, the amount of white on wings and tail diminishes, and adult plumages is usually acquired by the fifth year.[17]

Size readily distinguishes this species from most other raptors when it is seen well. Most other raptors are considerably smaller, including Buteo hawks which are perhaps most similar to the Golden Eagle in structure among smaller raptors. Buteos are also usually distinctly paler below.[18] Only some Old World vultures and the California Condor (Gymnogyps californianus) (among the other raptorial birds this eagle co-exists with) are distinctly larger, with longer, broader wings, typically held more evenly, and often have dramatically different color patterns. Compared to Haliaeetus eagles, the Golden is usually longer-tailed and is distinctly smaller-headed, with broad wings that are more hawk-like and less plank-like in shape. Whereas more Haliaeetus eagles are heavily streaked in their juvenile phase, the Golden has a more solidly golden-brown coloration. Distinguishing it from other Aquila eagles in Eurasia is a greater identification problem. This identification may rely on the Golden's relatively long tail and patterns of white or gray on the wings and tail. At close range, the paler head and golden nape-shawl of the Golden are distinctive from other Aquila. Most other Aquila eagles are darker looking in plumage, although the slightly smaller Tawny Eagle (A. rapax) is paler than the Golden Eagle. The Eastern Imperial (A. heliaca) and Spanish Imperial Eagle (A. adalberti) are the most similar in size to the Golden Eagle among Eurasian Aquila but are distinguished by their longer neck, flatter wings in flight, white on their shoulder forewing-coverts and generally darker coloration.[6] Verreaux's Eagle (A. verreauxii) are most similar in size and body shape to the Golden but are almost entirely black (except for some whitish color on the wing primary) in plumage and are not known to co-occur with the Golden Eagle in Africa.[6] Among the Aquila genus, only the long-winged and tailed Wedge-tailed Eagle (A. audax) exceed the Golden Eagle in average wingspan and length.

Taxonomy and systematics

This species was first described by Linnaeus in his 1758 Systema naturae as Falco chrysaetos.[19] The type locality was given simply as "Europa"; it was later fixed to Sweden. It was moved to the new genus Aquila by French ornithologist Mathurin Jacques Brisson in 1760.[20]

The Golden Eagle is one of the largest eagles in the genus Aquila, which are distributed almost worldwide. The latest research indicates it forms a worldwide superspecies with Verreaux's Eagle, Gurney's Eagle, and the Wedge-tailed Eagle.[citation needed]

Subspecies and distribution

There are six extant subspecies of Golden Eagle that differ slightly in size and plumage.

The larger Middle Pleistocene Golden Eagles of France (and possibly elsewhere) are referred to a paleosubspecies Aquila chrysaetos bonifacti, and the huge specimens of the Late Pleistocene of Liko Cave (Crete) have been named Aquila chrysaetos simurgh.[22]

Ecology

Habitat

Golden Eagles are fairly adaptable in habitat but often reside in areas with a few shared ecological characteristics. They are best suited to hunting in open or semi-open areas and search them out year-around. The largest numbers of Golden Eagles are found in mountainous regions today, with many eagles doing a majority of their hunting and nesting on rock formations. However, they are not solely tied to high elevations and can breed in lowlands if the local habitats are suitable. They can additionally be found in tundra, shrublands, coniferous forests with openings and steppe, prairies and other regional grassland habitats. Though not generally a wetland bird, they may pass through or hunt in marshes, normally while migrating or wintering. Golden Eagles usually nest in desolate areas where human disturbances are minimal and often avoid highly populated areas year-around. They may be found in elevation from sea-level up to at least 3,700 m (12,100 ft).[6]

Movements

Some populations of Golden Eagles are migratory and others are sedentary. Eagles who nest in colder climes such as Alaska, Scandinavia or Russia tend to migrate to points further south due to declining available food sources in the north. Those found further south in the species' breeding range are usually non-migratory and may remain without striking distance of their breeding territories all year.[6] While they usually fly at average speeds of 45–52 kilometers per hour (28–32 mph), they can glide quickly at up to 130 kilometers per hour (81 mph) and can reach 240 kilometers per hour (150 mph) when diving after prey. The characteristic flight of the species consists of a mix of flapping and soaring.[23]

Feeding

Golden eagle feeding on a red fox, Nasavrky[disambiguation needed], Czech Republic

The Golden Eagle is one of the most powerful predators in the avian world. They usually hunt by flying slowly while scanning the environment in a low quartering flight, often around mountainous slopes.[6] When prey is spotted, the eagle makes a short dash hoping to surprise its prey or engages in a longer rapid chase. They also hunt by flying in a fast glide or soar followed by a sudden stoop. Rarely, they may also still-hunt, watching for prey from an elevated perch and then pouncing down when it is spotted.[6] Given that their favorite prey are often mammals or birds that hesitate to fly, unsurprisingly most of their prey is killed on the ground and some prey may even pursued on foot for a short distance by the eagle.[6] When hunting birds, they may engage in an agile tail-chase (much in the style of the Accipiter hawks) and can occasionally snatch birds in mid-flight.[6] The powerful talons of the Golden Eagle ensure that few prey can escape them once contact is made. The talons of this species exert an estimated 440 pounds per square inch (3 MPa) of pressure, though the largest individuals may reach a pressure of 750 psi (5.2 MPa), around 15 times more pressure than is exerted by the human hand.[24]

While they do show strong local preferences for certain prey, Golden Eagles are first and foremost opportunists and virtually any small to mid-sized animal may be predated if encountered. Nearly 200 species of mammal and bird have been recorded as golden eagle prey.[4] Prey selection is largely determined by the local availability and abundance of the prey species.[4] Most prey taken are around half the weight of the predating eagle, with a typical prey weight range of 0.5–4 kg (1.1–8.8 lb),[4] though this eagle will sometimes fly with prey equal to or slightly heavier than its own weight (4–7 kg (8.8–15 lb)).[4]

In North America and most of Europe, the predominant prey are leporids (hares and rabbits) and sciurids (ground squirrels, prairie dogs, and marmots). In one North American study, mammals comprised 83.9% of the eagles' diet.[25] In Washington, the Yellow-bellied marmot (Marmota flaviventris) was eaten significantly more than other species, while in Great Britain and central and alpine Eurasia, the Mountain Hare (Lepus timidus) was taken far more than any other species.[4][26] On the Swedish island Gotland, the preferred prey of the Golden Eagle are hedgehogs, which are peeled of their prickly backs before being eaten.[6] Additional mammals regularly taken include smaller rodents, such as mice and voles, mid-sized mammals such as foxes and the offspring of ungulates such as deer, antelope, ibex, goats and sheep.[4] At the breeding ground of the Caribou (Rangifer tarandus), this eagle is one of the most frequent predators of newborn or young calves.[4][6] Domesticated types of ungulate young are taken as well.[4] For juvenile eagles, wintering eagles or eagles that have failed to breed, being able to carry off prey is less important than it is for those who are nesting and such birds are more likely to take large prey that can be left and returned to repeatedly feed on. Wild eagles have exceptionally taken ungulate prey in such circumstances weighing 30 kg (66 lb) or even more, such as adult Roe Deer (Capreolus capreolus).[4] Recent cases in which Golden Eagle were caught on film attacking unusual, large prey have included an unsuccessful attack on a large adult White-tailed Deer (Odocoileus virginianus) and a successful attack on an adult male Coyote (Canis latrans).[27][28] YouTube videos show trained Golden Eagles in Mongolia working alone, or in tandem, to take down wolves and foxes there, though the prey animals in this display may be already disabled.[29] There are no known instances of wild eagles predating adult wolves and, in falconry, almost all reported of trained killing of wolves are anecdotal.[4] Other videos show goats being dragged off cliffs to their deaths before being fed upon, and in one case being carried fully away by the leg, though the animals appear to be juveniles.[30][31] There are also numerous eye-witness accounts in Europe of sheep being carried off; again, these may be younger, lighter-weight animals. There is one confirmed report of a Golden Eagle snatching the cub of a Brown Bear (Ursus arctos).[32]

After mammals, the secondary important prey group for Golden Eagles are other birds. Various gallinaceous birds (largely phasianids and grouse) are the most significant avian prey.[4] However, virtually any bird, from the size of a lark or a pipit to a crane or a swan, about double the weight of an eagle, is potential prey.[6][33] In Sweden, birds were found to be the primary prey, with the most common prey species being the Western Capercaillie (Tetrao urogallus); while in sub-Arctic regions a strong preference for Rock Ptarmigan (Lagopus muta) has been noted.[4][34] Golden Eagles are avian apex predators, meaning a healthy adult is not preyed upon. There are records of Golden Eagles killing and eating other large raptors such as Gyrfalcons (Falco rusticolus), Northern Goshawks (Accipiter gentilis), and Buteo hawks, whether adults, nestlings or eggs.[33] Falcons, skuas, and Buteos like Rough-legged Hawks (B. lagopus), which are normally fierce competitors with each other, have worked together to group-mob Golden Eagles that have passed their adjacent nesting areas.[33] In one instance, a Golden Eagle flying in towards a Peregrine Falcon (Falco peregrinus) nest was struck and killed by a swooping parent falcon, a reversal of fortune for the falcon given that the much larger eagle is usually dominant over (and a potential predator of) them.[35] Large owls, such as those in the Bubo genus, may be killed by these eagles but usually avoid direct conflicts by being nocturnal in activity rather than diurnal.[36][37] More commonly, Golden Eagles kleptoparasitize, or steal prey, from other raptors. While not as large as some vultures, Golden Eagles are usually considerably more aggressive and are capable of driving vultures (including much larger-bodied species) and other raptors from carrion or kills.[4] Interspecies competition occurs regularly with large Haliaeetus eagles, principally White-tailed (H. albicilla) and Bald Eagles (H. leucocephalus). Although these other eagles (which are actually not closely related to the Golden) are generally less active predators, they are of comparable size, strength and tenacity to the Golden Eagle and victory in such conflicts depends on the size and disposition of individual eagle rather than on species.[33]

Numerous other types of prey may supplement the diet. Reptiles are rarely taken over most of the range but prey such as large snakes and lizards appears to be fairly common in the southern reaches of its Asian range, as well as in Japan and in desert-like regions of central Eurasia.[4][6] In southeastern Europe, Turkmenistan and other arid regions, tortoises are a favored prey item. Tortoises are dispatched using the same method employed by the Lammergeier (Gypaetus barbatus), which consists of flying with the bulky reptile and dropping it from some height onto rocks or other hard surfaces so the shell will crack open and its flesh can be eaten.[6] Other secondary prey items may include amphibians, fish (which are eaten regularly in Southeast Asia but are usually scavenged) and even insects such as large beetles.[6] During winter months, when live-caught prey can be scarce, Golden Eagles often scavenge on carrion.[18]

Reproduction

Eyrie (in hollow at left center) in the Valley of the Siagne de la Pare, Alpes-Maritimes, France

Golden Eagles usually mate for life. They build several eyries within their territory and use them alternately for several years. In the western United States, eagles' nesting territories may range from 22 to 33 square miles, whereas those nesting further north may maintain territories of up to 39 square miles. Territories are maintained by flight displays.[6] These nests consist of heavy tree branches, upholstered with grass when in use. Old eyries may be 2 metres (6.6 ft) in diameter and 1 metre (3.3 ft) in height, as the eagles repair their nests whenever necessary and enlarge them during each use. If the eyrie is situated on a tree, supporting tree branches may break because of the weight of the nest. Certain other animals—birds and mammals too small to be of interest to the huge raptor—often use the nest as shelter. Their predators are just the right size for Golden Eagle prey, and therefore avoid active eyries.

Mating and egg-laying time is variable depending on the locality and can be January and September, though is usually in March or later. The female lays one to four (usually two) eggs.[6] The eggs vary from all white to white with cinnamon or brown spots and blotches. Laying of the eggs occurs at 3 or 4 day intervals. The female starts incubation when the first egg is laid and continues to do so for 40 to 45 days, though the male may occasionally incubate as well.[6] They are covered in fluffy white down and are fed and brooded consistently for 45–50 days, with both parents taking shifts at feeding the young.[6] The nestlings start to leave the nest after 45 days (sometimes as late 81 days) by walking, hopping or falling out of the nest. At around 10 weeks of age, they start to fly and, once fledged, begin to eat on their own. Independence from the parents may variably be attained 32 to 80 days after the young are fledged.[6] Juveniles usually become established and start to breed at 4 to 7 years of age.[6]

In most cases only the older chick survives, while the younger one dies without leaving the eyrie. This is due to the older chick having a few days' advantage in growth and consequently winning most squabbles for food. This strategy is useful for the species because it makes the parents' workload manageable even when food is scarce, while providing a reserve chick in case the first-born dies soon after hatching. Golden Eagles invest much time and effort in bringing up their young; once able to hunt on their own, most Golden Eagles survive many years, but mortality even among first-born nestlings is much higher, in particular in the first weeks after hatching.[4] Due to the defensive ferocity of the eagles, predation on the Golden Eagle is rare even with eggs and small nestlings. The only known predators of Golden Eagle nests are wolverines and brown bears.[23] Although a high percentage may die in their first year, Golden Eagles who survive to adulthood may live quite long. In some cases, wild eagles can live for 28 to 32 years and individuals in captivity have survived to an age of 46 years. Most adult mortality is now human-related. This can include collision with man-made objects, incidental poisoning from chemicals, lead or ingestion of poison meant for mammalian scavengers or from hunting or trapping.

Status and conservation

Aquila chrysaetos 3 (Martin Mecnarowski).jpg

At one time, the Golden Eagle lived in almost all of temperate Europe, North Asia, North America, North Africa, and Japan. In most areas this bird is now a mountain-dweller, but in former centuries it also bred in the plains and the forests. In recent years it has started to breed in lowland areas again, e.g., in Sweden and Denmark.

There was a great decline in Central Europe where they are now essentially restricted to the Apennine, Alps, and Carpathian Mountains. In Britain, the last comprehensive survey of Golden Eagles took place in 2003, and found 442 occupied territories.[38] A less thorough survey in 2007 showed that in addition to large numbers of territories in the Scottish Highlands and the Inner and Outer Hebrides, there were a handful of birds in southern Scotland and northern England.[39] Between 1969 and 2003 they nested in the Lake District, Cumbria.[38]

In Ireland, where it had been extinct due to hunting since 1912, efforts are being made to re-introduce the species. Forty-six birds were released into the wild in Glenveagh National Park, County Donegal, from 2001 to 2006, with at least three known female fatalities since then. It is intended to release a total of sixty birds, to ensure a viable population. In April 2007, a pair of Golden Eagles produced the first chick to be hatched in the Republic of Ireland in nearly a century. The previous attempt to help the birds breed at the Glenveagh National Park had failed.[citation needed]

In North America the situation is not as dramatic, but there has still been a noticeable decline. The main threat is habitat destruction which by the late 19th century already had driven Golden Eagles from some regions they used to inhabit.[40] In the 20th century, organochloride and heavy metal poisonings were also commonplace, but these have declined thanks to tighter regulations on pollution. Within the United States, the Golden Eagle is legally protected by the Bald and Golden Eagle Protection Act.[6]

Available habitat and food are the main limiting factor nowadays. Collisions with power lines have become an increasingly significant cause of mortality since the early 20th century. Controversially, the US Fish and Wildlife Service has permitted that a "wind-farmer" in central Oregon could legally cause the incidental killing of Golden Eagles by large wind turbines. Such turbines have set up as an alternative source of energy and appear to move slowly from a distance but at close range move quickly enough to appear invisible or as a blur. It is estimated that up to 70 Golden Eagles may be killed by turbines each year.[41]

On a global scale, the Golden Eagle is not considered threatened by the IUCN due to an estimated world population of more than 170,000 individuals.[1] On a conservation front, the Golden Eagle is itself unintentionally contributing to the conservation crisis of another animal, the Island Fox (Urocyon littoralis), a small insular relative of the Gray Fox (U. cinereoargenteus) found only in the Channel Islands of California. This critically endangered canid had evolved without predators but the large breeding population of Golden Eagles in California has spilled in numbers over to the islands and is there feeding largely on the foxes, whose already declining population cannot support sustained predation.[42]

In human culture

1870s illustration of burkut falconers in Kazakhstan

Falconry

Golden Eagles have been used in falconry since the Middle Ages. In Asia, they were used in teams to hunt such animals as deer, antelope and wolves, while their use was reserved for Emperors in Europe.[43] They can be trained for falconry.[44]

Heraldry

Main article: Eagle (heraldry)
Albanian Flag
Mexican coat of arms
Coat of arms of Egypt

The Golden Eagle is the most common national animal in the world, with five nations—Albania, Germany, Austria, Mexico and Kazakhstan—making it the national animal. It is also a common motif in the national symbols of countries that have not officially made it the national animal or national bird. The reasons for this are various, but among the nations that use the Golden Eagle as or in a state symbol, there are two clear traditions that help explain the modern usage. Among European countries, the Golden Eagle was the model for the aquila, the most prominent symbol of the Roman legions and more generally the Roman civilization that had such a powerful impact on Western culture; furthermore, some Roman traditions were carried on by the Byzantine Empire in the Southern and Eastern of Europe and the Holy Roman Empire in Central and Western Europe, transmitting the use of the Golden Eagle to several modern states. This association of the Golden Eagle with Rome has also led to the adoption of similar symbols in other countries; for instance, the adoption of the related and physically similar Bald Eagle as the national bird of the United States was inspired by the conception of the United States as a modern reincarnation of the Roman Republic, a theme that recurs in other elements as well (including the prevalence of neoclassical architecture in American public buildings and the use of Roman terminology—such as naming the upper house of Congress the Senate—to hark back to the Roman model).

Another large tradition of using the Golden Eagle can be found in the Arab world, where the eagle is historically a symbol of power in Arabic poetry, and was according to legend the personal emblem of Saladin. The specific depiction of Golden Eagle legendarily considered to be Saladin's was adopted by the Arab nationalist movement, and currently appears on the arms of Egypt, Iraq, and Palestine; it had previously appeared on the arms of the People's Democratic Republic of Yemen (1967–1990) and on the arms of the Libyan Arab Republic (1970–1972). The current emblem of Yemen displays a Golden Eagle, but it is not that of Saladin.

Religion

In North America

The eagle is a sacred bird in some cultures and the feathers of the eagle are central to many religious and spiritual customs, especially among some Native Americans in the United States and First Nations in Canada, as well as among many of the peoples of Meso-America. Some Native American peoples revere eagles as sacred and the feathers and other parts of Bald and Golden Eagles. Feathers are often worn on Native American headdresses and have been compared to the Bible and crucifix of Christianity. Eagle feathers are often used in various Native ceremonies and are used to honour noteworthy achievements and qualities such as exceptional leadership and bravery.[citation needed] The Golden Eagle is thought to be the origin of the Thunderbird legends of the southwestern United States,[43]

Current United States eagle feather law (50 CFR 22) stipulates that only individuals of certifiable Native American ancestry enrolled in a federally recognized tribe are legally authorized to obtain eagle feathers for religious or spiritual use. Thus, the supply of eagle material for traditional ceremonial use can be guaranteed and ceremonial eagle items can be passed on as heirlooms by their traditional owners without the restrictions that would usually apply. Commercial trade in Golden Eagles or their feathers or body parts is not legalized by these exceptions.[45]

Postage stamps

The Golden Eagle is the eighth-most common bird depicted on postage stamps with 155 stamps issued by 71 stamp-issuing entities.[46][47]

Other

J.R.R. Tolkien used an image of an immature Golden Eagle from T. A. Coward's 1919 work The Birds of the British Isles and Their Eggs for an illustration depicting Bilbo awaking next to Gwaihir (a giant eagle).[48] Tolkien's Gwaihir was recreated digitally in the Academy Award-winning film The Lord of the Rings: The Return of the King. The cinematic Gwaihir was modeled after a stuffed Golden Eagle, which was thence scaled up to the size of a small airplane.[49]

References

  1. ^ a b BirdLife International (2012). "Aquila chrysaetos". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. http://www.iucnredlist.org/apps/redlist/details/106003537. Retrieved 16 July 2012.
  2. ^ Hunt, Grainger; Hunt, Teresa (June 2006). "The trend of Golden Eagle territory occupancy in the vicinity of the Altamont Pass Wind Resource Area: 2005 survey". Scientific Review Committee of the Altamont Pass Wind Resource Area. http://www.altamontsrc.org/alt_doc/r43_hunt_cec_500_2006_056.pdf. "The area surrounding the Altamont Pass Wind Resource Area (WRA) near Livermore, California contains a higher reported density of nesting golden eagles than anywhere else in the world."
  3. ^ Hunt, W. Grainger; Jackman, Ron E.; Hunt, Teresa L.; Driscoll, Daniel .E.; Culp, Lois (June 1999). "A Population Study of Golden Eagles in the Altamont Pass Wind Resource Area: Population Trend Analysis 1994–1997". National Renewable Energy Laboratory. http://www.nrel.gov/wind/pdfs/26092.pdf. "Annual nest surveys have revealed a substantial breeding population, the density of which is among the highest reported for the species. An 820–km2 area near the town of Livermore held at least 44 pairs in 1997, a density of one pair per 19 km2"
  4. ^ a b c d e f g h i j k l m n o p q Jeff Watson (23 August 2010). The Golden Eagle. A&C Black. ISBN 978-1-4081-1420-9. http://books.google.com/books?id=aj5MNvCkun0C. Retrieved 22 August 2012.
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  19. ^ "[Falco] cera lutea, pedibus lanatis, corpore fusco ferrugineo vario, cauda nigra basi cinereo-undulata." – "A [diurnal raptor] with yellow cere, [feathered tarsometatarsus], body dusky brown variegated with rusty, tail black with ashy-waved base." (Linnaeus 1758)
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  26. ^ Marr, N. Verne; Knight, Richard L. (1983). "Food Habits of Golden Eagles in Eastern Washington". The Murrelet (Society for Northwestern Vertebrate Biology) 64 (3): 73–77. doi:10.2307/3535265.
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  29. ^ Golden Eagle kills Grey wolf and fox.. YouTube (2010-01-22). Retrieved on 2012-08-22.
  30. ^ Golden Eagle dragging mountains goats off cliffs.. YouTube. Retrieved on 2012-08-22.
  31. ^ Golden Eagle Kills Goat for it's prey.. YouTube (2007-11-25). Retrieved on 2012-08-22.
  32. ^ Sørensen, Ole; Mogens Totsås, Tore Solstad, Robin Rigg (2008). "Predation by a Golden Eagle on a Brown Bear Cub". Ursus 19 (2): 190–193. doi:10.2192/08SC008.1. http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_19/Sorenson_Totsas_Solstad_Rigg_19_2.pdf.
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  34. ^ Tjernberg, Martin (1981). "Diet of the Golden Eagle Aquila chrysaetos during the Breeding Season in Sweden". Holarctic Ecology (Nordic Society Oikos) 4 (1): 12–19.
  35. ^ Hays, Larry L. "Peregrine Falcon Nest Defense Against a Golden Eagle". Journal of Raptor Research 21 (2): 67. http://elibrary.unm.edu/sora/jrr/v021n02/p00067-p00067.pdf.
  36. ^ Smith, D.G. (1982). "Spatial Relationships of Nesting Golden Eagles in Central Utah". Journal of Raptor Research 16 (4): 127–132. http://elibrary.unm.edu/sora/jrr/v016n04/p00128-p00132.pdf.
  37. ^ Owls of the World by Konig, Weick & Becking. Yale University Press (2009), ISBN 0300142277
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  40. ^ E.g. Henninger (1906)
  41. ^ Feds propose allowing wind-farm developer to kill golden eagles – U.S. News. Usnews.msnbc.msn.com (2012-01-04). Retrieved on 2012-08-22.
  42. ^ Urocyon littoralis (California Channel Island Fox, Channel Islands Fox, Island Fox, Island Gray Fox, Island Grey Fox). Iucnredlist.org. Retrieved on 2012-08-22.
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  47. ^ Scharning, Kjell. "Stamps showing Golden Eagle Aquila chrysaetos". Theme Birds on Stamps. http://www.birdtheme.org/mainlyimages/index.php?spec=1265. Retrieved 17 January 2011.
  48. ^ Hammond, Wayne G.; Scull, Christina (1995). J. R. R. Tolkien Artist and Illustrator. Hammersmith, London: HarperCollins. pp. 120–21. ISBN 0-261-10322-9.
  49. ^ http://gryphonking.aelfhame.net/iview.php3

Works cited

External links

Wikimedia Commons has media related to: Aquila chrysaetos
Wikispecies has information related to: Aquila chrysaetos

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