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.

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.