BALD EAGLE

Bald eagle (Haliaeetus leucocephalus) (Haliaeetus leucocephalus), bird of the family Accipitridae, the only eagle solely native to North America. Since 1782 the bald eagle has been the national bird of the United States. It is a sea eagle (Haliaeetus) that commonly occurs inland, along rivers and large lakes. The adult male bald eagle is about 90 cm (36 inches) long and has a wingspan of 2 m (6.5 feet). Females, which grow somewhat larger than males, may reach 108 cm (43 inches) in length and have a wingspan of 2.5 m (8 feet). The bald eagle is dark brown in colour, with a white head and tail. The bird is not actually bald; its name derives from the conspicuous appearance of its white-feathered head. The beak, eyes, and feet are yellow. The bald eagle's nest is a large tangle of sticks atop a large, isolated tree or pinnacle of rock that is within easy flight of a sea, lake, or stream. The female lays two or three eggs that hatch in 35 days, and both parents share in the incubation and feeding of the young. The immature birds are brown with whitish tail and wing linings, but the pure white head and tail plumage appears only when the birds are four or five years old. Bald eagles pluck fish out of the water with their talons, and sometimes they follow seabirds as a means of locating fish. Bald eagles also rob ospreys of their fish catches. Besides live fish, bald eagles prey on other birds, small mammals, snakes, turtles, and crabs, and they readily eat carrion. Bald eagles numbered in the tens of thousands when they were declared the American national bird in 1782, but their numbers steadily declined over the next two centuries owing to human activities. The birds were hunted, both for sport and because they were thought to menace livestock. In Alaska, where eagles perched on fish traps and scared away the salmon (an annoyance eventually overcome by fitting the traps with devices to discourage perching), Alaskan bounty hunters killed more than 100,000 eagles in the period 191752. The U.S. government made it illegal to kill bald eagles (with Alaska exempted) in the Bald Eagle Protection Act of 1940, but the birds' numbers continued to decline, primarily because of the effects of the pesticide DDT, which came into widespread agricultural use after World War II. This pesticide accumulated in the birds' tissues and interfered with the formation of the shells of their eggs; the thin, weak shells were easily broken. By the early 1960s, the number of bald eagles in the conterminous United States had dropped to fewer than 450 nesting pairs. In 197273 the use of DDT was banned in the United States, and in 1978 the U.S. government declared the bald eagle an endangered species in all but a few of the northernmost states. By the late 1980s, these measures had enabled the birds to replenish their numbers in the wild. The bald eagle was reclassified from endangered to threatened status in 1995, by which time there were an estimated 4,500 nesting pairs in the lower 48 states. Some authorities distinguish two subspecies of bald eagle: a northern one (H. l. alascanus), which sparsely inhabits the area from Maine to the Pacific Northwest and is still widespread in Alaska and nearby regions of Canada; and the southern bald eagle (H. l. leucocephalus), which is numerous now only in Florida. See also eagle.