Bald Eagle

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Image:BaldEagle.jpg

Common Name: Bald Eagle
Scientific Name: Haliaeetus leucocephalus

Size: 28-40 inches (70-102 cm); Wingspan: 69-89 inches (180-230 cm)

Habitat: North America; breeds in Canada, USA, Mexico, and the French island territories of Saint Pierre and Miquelon. It is considered a vagrant in Belize, Bermuda, Ireland, Puerto Rico, and the US Virgin Islands. Bald eagles will also congregate in certain locations in winter. From November until February, one to two thousand birds winter in Squamish, British Columbia, about halfway between Vancouver and Whistler. The birds primarily gather along the Squamish and Cheakamus Rivers, attracted by the salmon spawning in the area.

It occurs during its breeding season in virtually any kind of American wetland habitat such as seacoasts, rivers, large lakes or marshes or other large bodies of open water with an abundance of fish. It requires old-growth and mature stands of coniferous or hardwood trees for perching, roosting, and nesting. Tree species reportedly is less important to the eagle pair than the tree's height, composition and location.

Status: Least Concern. Global population: 250,000 adult individuals with an increasing population trend. This species has had a 779% increase over 40 years, equating to a 72.2% increase per decade.

Once abundant in North America, the species became rare in the mid-to-late 1900s—the victim of trapping, shooting, and poisoning as well as pesticide-caused reproductive failures. In 1978 the bird was listed for protection under the Endangered Species Act. Since 1980, conservation efforts with the banning of DDT (the bird’s main pesticide threat) have led to a dramatic resurgence. By the late 1990s, breeding populations of Bald Eagles could be found throughout most of North America. In June 2007, the bird’s recovery prompted its removal from the Endangered Species list. Continuing threats to Bald Eagle populations include lead poisoning from ammunition in hunter-shot prey, collisions with motor vehicles and stationary structures, and development-related destruction of shoreline nesting, perching, roosting and foraging habitats. They are still vulnerable to environmental pollution, as evidenced by the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska. An estimated 247 Bald Eagles died from oil exposure. Population levels in the Sound decreased by almost four percent the following year. The local population returned to pre-spill levels by 1995.

Diet: Mostly Fish (56% fish, 28% birds (mostly waterfowl and shorebirds), 14% mammals and 2% other prey). They take their prey live, fresh, or as carrion. Bald Eagles sometimes gorge, ingesting a large amount of food and digesting it over several days. They can also survive fasting for many days, even weeks.

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. Bald Eagles often go after other creatures’ catches. A Bald Eagle will harass a hunting Osprey until the smaller raptor drops its prey in midair, where the eagle swoops it up. A Bald Eagle may even snatch a fish directly out of an Osprey’s talons.

Nesting: Males and females are alike however females are 25% larger than males. Eagles in the far Northern Hemisphere are larger than more southern ones. The plumage of an adult bald eagle is evenly dark brown with a white head and tail. The tail is moderately long and slightly wedge-shaped. The beak, feet and irises are bright yellow. The legs are feather-free, and the toes are short and powerful with large talons. The beak is large and hooked, with a yellow cere.

Bald eagles are sexually mature at four or five years of age. When they are old enough to breed, they often return to the area where they were born. Bald eagles mate for life, however if one member of a pair dies or disappears, the other will choose a new mate. A pair which has repeatedly failed in breeding attempts may split and look for new mates. Bald eagle courtship involves elaborate, spectacular calls and flight displays. The flight includes swoops, chases, and cartwheels, in which they fly high, lock talons, and free fall, separating just before hitting the ground.

Nests are located in trees that are 38 m (52 to 125 ft) in height. Preferred tree height depends on location. In Chesapeake Bay, nesting trees averaged 82 cm (32 in) in diameter and 28 m (92 ft.) in total height, while in Florida, the average nesting tree stands 23 m (75 ft.) high and is 23 cm (9.1 in) in diameter. Trees used for nesting in the Greater Yellowstone area average 27 m (89 ft.) high. Trees or forest used for nesting should have a canopy cover of no more than 60%, and no less than 20%, and be in close proximity to water. Most nests have been found within 200 m (660 ft) of open water. When breeding where there are no trees, the bald eagle will nest on the ground, as has been recorded in areas largely isolated from terrestrial predators.

The nest base is built out of large sticks. Both sexes bring materials to the nest, but the female does most of the placement. They weave together sticks and fill in the cracks with softer material such as grass, moss, or cornstalks. The inside of the nest is lined first with lichen or other fine woody material, then with downy feathers and sometimes sprigs of greenery. The typical nest is 5 to 6 feet in diameter and 2 to 4 feet tall, and ranging in shape from cylindrical to conical to flat, depending on the supporting tree. The largest recorded nest was found in Florida in 1963, and was measured at nearly 10 feet wide and 20 feet deep.

1-3 eggs are laid. Both the male and female take turns incubating the eggs, but the female does most of the incubation. The parent not incubating will hunt for food or look for nesting material during this stage. For the first two to three weeks of the nestling period at least one adult is at the nest almost 100% of the time. After five to six weeks, the attendance of parents usually drops off considerably (with the parents often perching in trees nearby). A young eaglet can gain up to 170 g (6.0 oz.) a day, the fastest growth rate of any North American bird. The young eaglets pick up and manipulate sticks, play tug of war with each other, practice holding things in their talons, and stretch and flap their wings. The young fledge at anywhere from 8 to 14 weeks of age, though will remain close to the nest and attended to by their parents for a further 6 weeks.

Cool Facts: The Bald Eagle has been the national emblem of the United States since 1782 and a spiritual symbol for native people for far longer than that. Bald eagles are not actually bald; the name derives from an older meaning of "white headed". They can live a long time, with a longevity record of 28 years in the wild and 36 years in captivity.

Bald Eagles have been known to play with plastic bottles and other objects pressed into service as toys. One observer witnessed six Bald Eagles passing sticks to each other in midair.

There are two subspecies of bald eagle:

  • H. l. leucocephalus (by Linnaeus in 1766) is the nominate subspecies. It is found in the southern United States and Baja California.
  • H. l. washingtoniensis (by Audubon in 1827), the northern subspecies, is larger than southern nominate species. It is found in the northern United States, Canada and Alaska.


This 3D model is found in Songbird ReMix Birds of Prey Volume IV: Eagles of the World

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