Eagles

Eagles

North American eagles

Eagles elsewhere

Eagles and humans

Resources

Eagles are large, diurnal birds of prey in the family Accipitridae, which also includes kites, harriers, gos-hawks, sparrowhawks, buzzards and other broad-winged hawks, vultures, and the osprey. The accipitrids are in the order Falconiformes, which also includes falcons, caracaras, and the secretary bird.

Like all of these predatory birds, eagles have strong, raptorial (or grasping) talons, a large hooked beak, and extremely acute vision. Eagles are broadly distinguished by their great size, large broad wings, wide tail, and their soaring flight. Their feet are large and strong, armed with sharp claws, and are well-suited for grasping prey. Some species of eagles are uniformly dark brown colored, while others have a bright, white tail or head. Male and female eagles are similarly colored, but juveniles are generally dark. Female eagles are somewhat larger than males.

Species of eagles occur on all of the continents, except for Antarctica. Some species primarily forage in terrestrial habitats, while others are fish-eating birds that occur around large lakes or oceanic shores. Eagles are fierce predators, but they also scavenge carrion when it is available.

North American eagles

The most familiar and widespread species of eagle in North America is the bald eagle (Haliaeetus leucocephalus ). Mature bald eagles have a dark brown body, and a white head and tail. Immature birds are browner and lack the bold white markings on the tail and head. They gradually develop the rich adult plumage, which is complete when the birds are sexually mature at four to five years of age. The bald eagle mostly feeds on fish caught or scavenged in rivers, lakes, ponds, and coastal estuaries.

Bald eagles nest on huge platforms built of sticks, commonly located on a large tree. Because the nests are used from year to year, and new sticks are added each breeding season, they can eventually weigh several tons. Northern populations of bald eagles commonly migrate to the south to spend their non-breeding season. However, these birds are tolerant of the cold and will remain near their breeding sites as long as there is open water and a dependable source of fish to eat. Other birds winter well south of their breeding range.

The golden eagle (Aquila chrysaetos ) is an uncommon species in North America, breeding in the northern tundra, in mountainous regions, and in extensively forested areas. The golden eagle also breeds in northern Europe and Asia. This species has dark brown plumage, and its wingspan is as great as 6.5 ft (2 m). These birds can prey on animals as large as young sheep and goats, but they more commonly take smaller mammals such as marmots and ground squirrels.

Golden eagles nest in a stick nest built on a large tree or a cliff. As with the bald eagle, the nest may be used for many years, and may eventually become a massive structure. Usually, two to three white-downed eaglets are hatched, but it is uncommon for more than one to survive and fledge. It takes four to five years for a golden eagle to become sexually mature.

Eagles elsewhere

The largest species of eagle is the harpy eagle (Harpia harpyja ) of tropical forests of South America. This species mostly feeds on monkeys and large birds. The Philippine monkey-eating eagle (Pithecophaga jefferyi ) and New Guinea harpy eagle (Harpyopsis novaguineae ) are analogous species in Southeast Asia.

The sea eagle or white-tailed eagle (Haliaeetus albicilla ) is a widespread species that breeds in coastal habitats from Greenland and Iceland, through Europe, to Asia. This species has a dark brown body and white tail. Another fishing eagle (H. vocifer ) breeds in the vicinity of lakes and large rivers in Africa.

The imperial eagle (Aquila heliaca ) and spotted eagle (A. clanga ) are somewhat smaller versions of the golden eagle, breeding in plains, steppes, and other open habitats from central Asia to Spain and northwestern Africa. These birds tend to eat smaller-sized mammals than the golden eagle.

The short-toed or snake eagle (Circaetus gallicus ) breeds extensively in mountainous terrain in southern Europe and southwestern Asia. This species feeds on small mammals and snakes. Because it preys on large numbers of poisonous vipers, the short-toed eagle is highly regarded by many people living within its range.

The black eagle (Ictinaetus malayensis ) is a species of tropical forest, ranging from India and southern China to the islands of Java and Sumatra in Indonesia.

Eagles and humans

Because of their fierce demeanor and large size, eagles have long been highly regarded as a symbol of power and grace by diverse societies around the world. Eagles have figured prominently in religion, mythology, art, literature, and other expressions of human culture.

In North America, for example, the bald eagle is an important symbol in many Native American cultures. Many tribes believe that the feathers of this bird have powerful qualities, and they use these feathers to ornament clothing and hats, or will hold a single feather in the hand as a cultural symbol and source of strength. Various tribes of the Pacific coast know the bald eagle as the “thunder bird,” and they accord it a prominent place on totem poles.

Today, most North Americans regard the bald eagle as a valued species, and it is even a national symbol of the United States. However, some people consider eagles to be pests, believing the birds to be predators of domestic animals such as sheep, or of economically important fish. For these reasons, many eagles have been killed using guns, traps, and poison. These attitudes about eagles are now in an extreme minority, and very few people still seek to kill these magnificent predators.

However, eagles and many other species of raptors are also damaged by other, less direct, human influences. These include the toxic effects of insecticides used in agriculture, some of which accumulate in wild animals and affect them or their reproduction. Eagles have also been poisoned by eating poisoned carcasses set out to kill other scavengers, such as coyotes or wolves. Eagles are also affected by ecological changes in their necessary breeding, migrating, and wintering habitats, especially damage caused by agriculture, urbanization, and forestry.

Because of these and other damaging effects of human activities, most of the world’s species of eagles are much less abundant than they were a century or so ago. Many local populations of these magnificent birds have become endangered or have actually been extirpated. In more extreme cases of endangerment, some species are at risk of total biological extinction. The monkey-hunting harpy eagle, for example, is a sparsely distributed and rare bird that requires extensive tracts of tropical rainforest in South America. It has been extirpated from large parts of its former

KEY TERMS

Diurnal— Refers to animals that are mainly active in the daylight hours.

Extirpated— The condition in which a species is eliminated from a specific geographic area of its habitat.

Raptor— A bird of prey. Raptors have feet adaptive for seizing, and a beak designed for tearing.

range. The harpy eagle is endangered because of deforestation, hunting, and even competition with humans for prey.

Resources

BOOKS

del Hoyo, J., A. Elliott, and J. Sargatal. “Handbook of the Birds of the World.” Vol. 2, New World Vultures to Guineafowl. Barcelona: Lynx Edicions, 2000.

Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.

Freedman, B. Environmental Ecology. 2nd ed. San Diego: Academic Press, 1995.

Gerrard, J., and G. Bortolotti. The Bald Eagle. Washington, DC: Smithsonian Press, 1988.

Johnsgard, P.A. Hawks, Eagles, and Falcons of North America: Biology and Natural History. Washington, DC: Smithsonian Press, 2001.

Savage, C. Eagles of North America. 2nd ed. New York: Sterling, 2000.

Bill Freedman