Eagle, any of many large, heavy-beaked, big-footed birds of prey belonging to the family Accipitridae (order Accipitriformes). In general, an eagle is any bird of prey more powerful than a buteo. An eagle may resemble a vulture in build and flight characteristics but has a fully feathered (often crested) head and strong feet equipped with great curved talons. A further difference is in foraging habits: eagles subsist mainly on live prey. They are too ponderous for effective aerial pursuit but try to surprise and overwhelm their prey on the ground. Like owls, many decapitate their kills. Because of their strength, eagles have been a symbol of war and imperial power since Babylonian times. Their likeness is found on Greek and Roman ruins, coins, and medals.
Eagles are monogamous. They mate for life and use the same nest each year. They tend to nest in inaccessible places, incubating a small clutch of eggs for six to eight weeks. The young mature slowly, reaching adult plumage in the third or fourth year.
The harpy eagles, named after the foul, malign creatures (part woman and part bird) of Greek mythology, are large, powerful, crested eagles of the tropical forests of South America and the South Pacific. They nest in the tops of the tallest trees and hunt macaws, monkeys, and sloths. The great harpy eagle (Harpia harpyja), which ranges from southern Mexico to Brazil, is about 1 metre (3.3 feet) long and bears a crest of dark feathers on its head. Its body is black above and white below except for a black chest band. It is becoming increasingly rare, particularly in Mexico and Central America. The New Guinea harpy eagle (Harpyopsis novaeguineae) is about 75 cm (30 inches) long. It is gray-brown and has a long tail and a short but full crest. Very similar in appearance and habits is the Philippine eagle (Pithecophaga jefferyi). It is about 90 cm (35 inches) long, brown above and white below, with a crest of long, narrow feathers. It is an endangered species.
The harrier eagles, six species of Circaetus (subfamily Circaetinae, serpent eagles), of Europe, Asia, and Africa, are about 60 cm (24 inches) long and have short unfeathered legs. They nest in the tops of trees and hunt snakes.