Hippocampus Bildarchiv
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Haliaeetus leucocephalus
American Bald Eagle
code: VVOFT0115
code: VVOFT0116
code: VVOFT0117
code: VVOFT0118
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Exif ImageDescription: Wei§kopfseeadler, Bald eagle, Haliaeetus leucocephalus
The Bald Eagle (Haliaeetus leucocephalus), also known in the United States as the American Eagle, is a bird of prey found in North America, most recognizable as the national bird and one of the primary symbols of the United States. ...The plumage of an adult Bald Eagle is evenly brown with a white head and tail. The tail is moderately long and slightly wedge-shaped. Males and females are identical in plumage coloration, but females are 25% larger than males, displaying sexual dimorphism.[2]The beak, feet, and irises are bright yellow. The legs are unfeathered, and the toes are short and powerful with long talons. The highly developed talon of the hind toe is used to pierce the vital areas of prey while it is held immobile by the front toes. The beak is large and hooked, with a yellow cere. The plumage of the immature Bald Eagle is brown, speckled with white until the fourth year, when it reaches sexual maturity. This species is distinguishable from the Golden Eagle in that the latter has feathers which extend down the legs. Also, the immature Bald Eagle has more light feathers in the upper arm area, especially around the 'armpit'. Body length ranges from 27 to 40 inches (68-100 cm). Adult females have an average wingspan of about 7 feet (2.1 meters); adult males have a wingspan of 6 ft 6 in (2 meters). Adult females weigh approximately 12.8 lb (5.8 kg), males weigh 9 lb (4.1 kg). The smallest specimens are those from Florida, where an adult male may barely exceed 5 lb (2.3 kg) and a wingspan of 6 feet (1.8 meters). The largest are the Alaskan birds, where large females may exceed 16.5 lb (7.5 kg) and have a wingspan of over 8 feet (2.4 meters). In the wild, Bald Eagles typically live about 20-30 years, but can realize a life span of approximately 50 years. They generally live longer in captivity, up to 60 years....The Bald Eagle prefers habitats near seacoasts, rivers, large lakes, and other large bodies of open water with an abundance of warm-water fishes. Studies have shown a preference for bodies of water with a circumference greater than 11 km (7 mi), and lakes with an area greater than 10 sq km (3.8 square miles) are optimal for breeding bald eagles, although longer and narrower bodies of water can support breeding pairs. The Bald Eagle requires old-growth and mature stands of coniferous or hardwood trees for perching, roosting, and nesting. Selected trees must have good visibility, an open structure, and proximity to prey, but the height or species of tree is not as important as an abundance of comparatively large trees surrounding the body of water. Forests used for nesting should have a canopy cover of less than 60 percent, and as low as 20 percent, and be in close proximity to water.The Bald Eagle is extremely sensitive to human activity, and occurs most commonly in areas free of human disturbance. It choose sites more than 1.2 km (0.75 miles) from low-density human disturbance and more than 1.8 km (1.2 miles) from medium- to high-density human disturbance.The Bald Eagle's natural range covers most of North America, including most of Canada, all of the continental United States, and northern Mexico. The bird itself is able to live in most of North America's varied habitats from the bayous of Louisiana to the Sonoran desert and the eastern deciduous forests of Quebec and New England. It can be a migratory bird but it also is not unheard of for a nesting pair to overwinter in its breeding area. Bald Eagles will also congregate in certain locations in winter. From November until February, between one and two thousand birds winter in Squamish, British Columbia, about halfway between Vancouver and Whistler. The birds primarily sit along the Squamish and Cheakamus Rivers and feed on salmon spawning in the area. There are numerous viewing spots where numerous birds can easily be seen....The Bald Eagle is a powerful flier, and soars on thermal convection currents. It is partially migratory. If its territory has access to water, it remains there year-round, but if it lacks access to water, it migrates to the south or to the coast during winter, in order to obtain food. The Bald Eagle selects migration routes which take advantage of thermals, updrafts, and food resources. During migration, it may ascend in a thermal and then glide down, circle steadily down a stream of thermals, an updraft as it sweeps down against a cliff or other terrain. Migration generally takes place during the daytime, when thermals are produced by the sun. Bald Eagles normally squeak and have a shrill cry, punctuated by grunts. They do not make the scream that is found in films; this is usually the call of a Red-tailed Hawk, dubbed into films for dramatic effect.The Bald Eagle's diet is opportunistic and varied, but most eagles live mostly off of fish. In the Pacific Northwest, almost the entirety of Bald Eagle subsistence is comprised by spawning trout and salmon. Locally, eagles may rely largely on carrion, especially in winter, and they can scavenge carcasses up to the size of whales, though it seems that carcasses of ungulates and large fish are preferred. They also may sometimes feed on subsistence scavenged or stolen from campsites and picnics, as well as garbage dumps. Mammalian prey includes rabbits, hares, raccoons, muskrats and deer fawns. Preferred avian prey includes grebes, alcids, ducks, gulls, coots, egrets and geese. Most live prey are quite a bit smaller than the eagle, but predatory attacks on large birds such as the Great Blue Heron and even swans have been recorded. Reptiles, amphibians and crustaceans (especially crabs) are preyed on when available.To hunt fish, easily their most important live prey, the eagle swoops down over the water and snatches the fish out of the water with its talons. They eat by holding the fish in one claw and tearing the flesh with the other. Eagles have structures on their toes called spiricules that allow them to grasp fish. Osprey also have this adaptation. Bald Eagles have powerful talons. In one case, an eagle was able to fly off with the 6.8 kg (15 lb) carcass of a Mule Deer fawn, the greatest weight-carrying capacity ever shown by a flying bird. Sometimes, if the fish is too heavy to lift, the eagle will be dragged into the water. It may swim to safety, but some eagles drown or succumb to hypothermia. When competing for food, eagles will usually dominate other fish-eaters and scavengers, aggressively displacing corvids, mammals such as coyotes and foxes, gulls, vultures and other raptors. Bald Eagles may be displaced by or themselves displace Golden Eagles, with neither formidable species known to be dominant. Occasionally, Bald Eagles will pirate fish away from smaller raptors, such as Ospreys, and the victim will often be forced to give up their prey, a practice known as kleptoparasitism.Bald Eagles perform a "cartwheel" display in which they fly high in the sky, lock talons, and free fall. They separate just before hitting the ground.Bald Eagles build huge nests out of branches, usually in large trees near water. The nest may stretch as large as eight feet across and weigh up to a ton (907 kg). When breeding where there are no trees, the Bald Eagle will nest on the ground. Eagles produce between one and three eggs per year, but it is rare for all three chicks to successfully fly. Both the male and female take turns sitting on the eggs. The other parent will hunt for food or look for nesting material. The eggs average about 2.9 inches (7.3 cm) long and have a breadth of 2.2 inches (5.5 cm). The incubation period averages at about 35 days and the parents will brood their offspring until they are about 4 weeks of age. The fledging stage can occur at any time from 8 to 14 weeks, the wide variation dictated by the effects of sex and hatching order on growth and development. Egg and nestling predation may be committed by Black-billed Magpies, gulls, ravens and crows, black bears and raccoons. With no known predators themselves, adults will fiercely defend their offspring from all these species. Eagles that are old enough to breed often return to the area where they were born. Bald Eagles are sexually mature at 4 or 5 years old.Source:Wikipedia
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