Bald Eagle
Facts
Conservation Status: Least Concern
Location: North America
Lifespan:
Conservation Status: Least Concern
Location: North America
Lifespan:
Scientific Classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Haliaeetus
Species: H. Leucocephalus
Binomial name: Haliaeetus Leucocephalus
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Haliaeetus
Species: H. Leucocephalus
Binomial name: Haliaeetus Leucocephalus
Description
Length: 70 to 100 cm (8 to 40 in)
Wingspan: 1.7 to 2.4 m (66 to 96 in)
Weight: 2.5 to 7 kg (5.5 to 15 lbs) Females are about 25% larger than males.
Other: 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 sexual dimorphism is evident in the species in that females are 25 percent larger than males. The beak, feet, and irises are bright yellow. The legs are feather-free, and the toes are short and powerful with large 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.
Length: 70 to 100 cm (8 to 40 in)
Wingspan: 1.7 to 2.4 m (66 to 96 in)
Weight: 2.5 to 7 kg (5.5 to 15 lbs) Females are about 25% larger than males.
Other: 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 sexual dimorphism is evident in the species in that females are 25 percent larger than males. The beak, feet, and irises are bright yellow. The legs are feather-free, and the toes are short and powerful with large 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.
Behaviour
he Bald Eagle is a powerful flier, and soars on thermal convection currents. It reaches speeds of 56–70 kilometers per hour (35–43 mph) when gliding and flapping, and about 48 kilometers per hour (30 mph) while carrying fish. Its dive speed is between 120–160 kilometers per hour (75–99 mph), though it seldom dives vertically. It is partially migratory, depending on location. If its territory has access to open water, it remains there year-round, but if the body of water freezes during the winter, making it impossible to obtain food, it migrates to the south or to the coast. 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, or may ascend in updrafts created by the wind against a cliff or other terrain. Migration generally takes place during the daytime, when thermals are produced by the sun.
he Bald Eagle is a powerful flier, and soars on thermal convection currents. It reaches speeds of 56–70 kilometers per hour (35–43 mph) when gliding and flapping, and about 48 kilometers per hour (30 mph) while carrying fish. Its dive speed is between 120–160 kilometers per hour (75–99 mph), though it seldom dives vertically. It is partially migratory, depending on location. If its territory has access to open water, it remains there year-round, but if the body of water freezes during the winter, making it impossible to obtain food, it migrates to the south or to the coast. 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, or may ascend in updrafts created by the wind against a cliff or other terrain. Migration generally takes place during the daytime, when thermals are produced by the sun.
Predators or Prey?
The adult bald eagle’s only predator is the human. Small eaglets are vulnerable to larger birds of prey, ravens, and larger climbing mammals such as bears and raccoons. Grounded non-flying young are vulnerable to other mammalian predators (e.g., wolves, coyotes) as well. The Bald Eagle's favourite food is fish but they are opportunistic feeders and the menu can include mammals, birds, reptiles and amphibians. The fish can be fresh-caught, stolen from other birds, or scavenged. During the 2009 nesting season, in addition to fish they also delivered the remains of several opossums, a mink, a partial waterfowl, a crow, and possibly a gull to the nest.
The adult bald eagle’s only predator is the human. Small eaglets are vulnerable to larger birds of prey, ravens, and larger climbing mammals such as bears and raccoons. Grounded non-flying young are vulnerable to other mammalian predators (e.g., wolves, coyotes) as well. The Bald Eagle's favourite food is fish but they are opportunistic feeders and the menu can include mammals, birds, reptiles and amphibians. The fish can be fresh-caught, stolen from other birds, or scavenged. During the 2009 nesting season, in addition to fish they also delivered the remains of several opossums, a mink, a partial waterfowl, a crow, and possibly a gull to the nest.
Diet
The Bald Eagle's diet is opportunistic and varied, but most feed mainly on fish. In the Pacific Northwest, spawning trout and salmon provide most of the Bald Eagles' diet. Locally, eagles may rely largely on carrion, especially in winter, and they will 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, beavers, 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 larger birds such as swans have been recorded. Reptiles, amphibians and crustaceans (especially crabs) are preyed on when available.
The Bald Eagle's diet is opportunistic and varied, but most feed mainly on fish. In the Pacific Northwest, spawning trout and salmon provide most of the Bald Eagles' diet. Locally, eagles may rely largely on carrion, especially in winter, and they will 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, beavers, 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 larger birds such as swans have been recorded. Reptiles, amphibians and crustaceans (especially crabs) are preyed on when available.
Habitat
The Bald Eagle prefers habitats near seacoasts, rivers, large lakes, oceans, and other large bodies of open water with an abundance of fish. 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 square kilometers (4 sq mi) are optimal for breeding Bald Eagles. 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 no more than 60 percent, and no less than 20 percent, and be in close proximity to water.
The Bald Eagle prefers habitats near seacoasts, rivers, large lakes, oceans, and other large bodies of open water with an abundance of fish. 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 square kilometers (4 sq mi) are optimal for breeding Bald Eagles. 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 no more than 60 percent, and no less than 20 percent, and be in close proximity to water.
Conservation
Once a common sight in much of the continent, the Bald Eagle was severely affected in the mid-20th century by a variety of factors, among them the thinning of egg shells attributed to use of the pesticide DDT. Bald Eagles, like many birds of prey, were especially affected by DDT due to biomagnification. DDT itself was not lethal to the adult bird, but it interfered with the bird's calcium metabolism, making the bird either sterile or unable to lay healthy eggs. Female eagles laid eggs that were too brittle to withstand the weight of a brooding adult, making it nearly impossible for the eggs to hatch. It is estimated that in the early 18th century, the Bald Eagle population was 300,000–500,000, but by the 1950s there were only 412 nesting pairs in the 48 contiguous states of the US. Other factors in Bald Eagle population reductions were a widespread loss of suitable habitat, as well as illegal shooting, which was described as "the leading cause of direct mortality in both adult and immature bald eagles," according to a 1978 report in the Endangered Species Technical Bulletin. In 1984, the National Wildlife Federation listed hunting, power-line electrocution, and collisions in flight as the leading causes of eagle deaths. Bald Eagle populations have also been negatively affected by oil, lead, and mercury pollution, and by human and predator intrusion.
Once a common sight in much of the continent, the Bald Eagle was severely affected in the mid-20th century by a variety of factors, among them the thinning of egg shells attributed to use of the pesticide DDT. Bald Eagles, like many birds of prey, were especially affected by DDT due to biomagnification. DDT itself was not lethal to the adult bird, but it interfered with the bird's calcium metabolism, making the bird either sterile or unable to lay healthy eggs. Female eagles laid eggs that were too brittle to withstand the weight of a brooding adult, making it nearly impossible for the eggs to hatch. It is estimated that in the early 18th century, the Bald Eagle population was 300,000–500,000, but by the 1950s there were only 412 nesting pairs in the 48 contiguous states of the US. Other factors in Bald Eagle population reductions were a widespread loss of suitable habitat, as well as illegal shooting, which was described as "the leading cause of direct mortality in both adult and immature bald eagles," according to a 1978 report in the Endangered Species Technical Bulletin. In 1984, the National Wildlife Federation listed hunting, power-line electrocution, and collisions in flight as the leading causes of eagle deaths. Bald Eagle populations have also been negatively affected by oil, lead, and mercury pollution, and by human and predator intrusion.
Reproduction
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. It is thought that 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 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. The nest is the largest of any bird in North America; it is used repeatedly over many years and with new material added each year may eventually be as large as 4 meters (13 ft) deep, 2.5 meters (8.2 ft) across and weigh 1 metric ton (1.1 short tons); one nest in Florida was found to be 6.1 meters (20 ft) deep, 2.9 meters (9.5 ft) across, and to weigh 3 short tons (2.7 t). This nest is on record as the largest tree nest ever known. The nest is built out of branches, usually in large trees near water. 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 incubating the eggs. The other parent will hunt for food or look for nesting material. The eggs average about 73 millimeters (2.9 in) long and have a breadth of 55 millimeters (2.2 in).
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. It is thought that 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 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. The nest is the largest of any bird in North America; it is used repeatedly over many years and with new material added each year may eventually be as large as 4 meters (13 ft) deep, 2.5 meters (8.2 ft) across and weigh 1 metric ton (1.1 short tons); one nest in Florida was found to be 6.1 meters (20 ft) deep, 2.9 meters (9.5 ft) across, and to weigh 3 short tons (2.7 t). This nest is on record as the largest tree nest ever known. The nest is built out of branches, usually in large trees near water. 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 incubating the eggs. The other parent will hunt for food or look for nesting material. The eggs average about 73 millimeters (2.9 in) long and have a breadth of 55 millimeters (2.2 in).
