Eagle

I

Introduction

Eagle, large bird of prey that is active during the daytime. Like other birds of prey, such as hawks and vultures, eagles hunt, kill, and eat other animals. Eagles are found throughout the world except in Antarctica and on some remote ocean islands. Only two kinds of eagles live in North America: the golden eagle and the bald eagle. Among the largest eagles in the world are the harpy eagle of Latin America and the Philippine eagle of Asia. These birds have wingspans as great as 2.5 m (8 ft) and weigh as much as 9 kg (20 lbs). In most eagle species, the female is slightly larger than the male.

The word eagle comes from the ancient Roman name for the golden eagle, aquila. This eagle has been regarded from ancient times as a symbol of courage and power because of its large size, superb flying skills, and its unreachable nest sites in remote, mountainous country. In Roman myths the golden eagle is associated with the principal god, Jupiter. It was the emblem of certain Roman military legions, of France under Napoleon, of Germany, and of the Russian and Austro-Hungarian empires. In 1782 the bald eagle was adopted for the emblem of the United States as a symbol of strength and freedom.

II

Characteristics of Eagles

Eagles are characterized by their stout legs, strong feet with sharp talons (claws), and a hooked bill that is nearly as long as their head. They have large, broad, strong wings and a broad tail that in flight is spread like a fan. The broad wings enable eagles to soar gracefully through the air. To conserve energy they flap their wings as little as possible, gliding and using thermals—rising columns of warm air—to gain height. Eagles can reach speeds up to 100 km per hour (60 mph), but they usually fly more slowly to use less energy. They can dive for prey at speeds greater than 160 kph (100 mph).

Eagles have extremely sharp eyesight and can spot prey from a great distance. Respect for the eagle’s keen eyesight is conveyed by the expression eagle eye. The various kinds of eagles prey on mammals, reptiles, or fish. They may swoop low to snatch prey with their feet, or make a direct downward dive onto the prey. The eagle kills its prey with its strong feet and talons, with which it can squeeze the life from the captured animal, and it rips the flesh from its prey with a large, curved bill.

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Eagles have a lifespan of about 20 to 30 years in the wild, though some species live even longer. Eagles in captivity can live more than 40 years. Male and female eagles are thought to form lifelong pair bonds. Some eagle species perform spectacular flight displays during courtship. They may lock talons high in the sky and tumble together through the air, separating just before they reach the ground. Eagles build nests largely of sticks and twigs, which they place in layers. They may return to the same nest year after year, adding new materials to the old nest. Over time eagle nests can become enormous, measuring more than 3 m (10 ft) high and more than 3 m (10 ft) across and weighing more than a ton.

The female eagle generally lays one or two eggs. She sits on the eggs, while the male hunts and brings her food. Although male golden eagles will brood (cover and keep warm) newly hatched chicks, in most eagles the male’s role is to hunt for food. He brings food to the female at the nest, and she then feeds the chicks.

The female stays at or near the nest until the downy young have begun to grow feathers. At this time she starts hunting for food for the chicks while the male does less of this work. After the young are fully grown, they remain near the nest for a time while still being fed by the parents. In some species the young become independent quite soon, whereas in others there is a long transition period as the parents do less and less feeding.

Eagles do not nest close to one another, and they need a large territory for hunting. Generally, the larger the eagle, the larger its prey and the larger the territory it seeks to defend. When too many nests appear in an area, fights may break out among the occupants. Because eagles raise so few offspring and because of their territorial requirements, habitat disturbances, such as water pollution, the development of waterfronts, and the destruction of forests, have threatened many eagle species. See Endangered Species.

III

Kinds of Eagles

Eagles belong to a large family of birds that also includes kites, hawks, buzzards, and certain vultures. There are about 60 different species of eagles and no widely accepted system of classifying them. Some experts classify eagles by prominent features or habits into four loose groups: booted or true eagles, sea or fish eagles, forest eagles, and snake or serpent eagles. The booted eagles have feathered legs in contrast to the bare and scaled legs of eagles in the other groups (and of most other birds). Sea eagles, such as the bald eagle, feed mainly on fish. Most forest eagles inhabit tropical rain forests. As their name suggest, snake eagles feed primarily on snakes.

IV

Golden Eagles and Other Booted Eagles

The golden eagle is distributed through most of the northern hemisphere, in North America, Europe, Asia, and Africa. In North America they are most common in the mountainous areas and the prairies of the western United States and Canada. Golden eagles are found as far south as Mexico.

Dark brown or blackish-brown plumage covers the bodies of golden eagles, with a layer of golden feathers on the back of the head and neck. This golden plumage gives the bird its name. Female golden eagles grow about 1 m (about 3 ft) long from the tip of the beak to the tip of the tail. They have a wingspread of about 2 m (about 7 ft). Males are smaller, as is true for most birds of prey. The birds’ legs and feet are feathered down to the toes. The tail of adults is brown with several indistinct pale bands; that of immature birds is white with a dark brown band at the end.

Most golden eagles build their nests on cliff ledges, but in some areas they prefer to nest in large trees. Like other eagles they build large, coarse nests of sticks and twigs. The female usually lays two eggs, but she may lay only one or, on occasion, three. The eggs are heavily marked with blotches and spots of various shades of brown.

Golden eagles feed mainly on small mammals, especially mice, larger rodents, and rabbits, although they can kill mammals as large as deer. They also eat reptiles and birds. If live food is in short supply, golden eagles will eat carrion (dead animal flesh). When hunting, they usually soar in low over their prey.

There are a number of other species in the golden eagle’s genus, Aquila. All of them are found in the Eastern Hemisphere. The smallest is the lesser spotted eagle, with a wingspan of about 1.5 m (about 5 ft); it migrates from central Europe to as far south as South Africa. The largest is the wedge-tailed eagle of Australia, a mostly black bird with a wingspan of as much as 2.4 m (about 8 ft). A group of small to medium-size booted eagles, known collectively as hawk-eagles, are found in many parts of the world.

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