Bald Eagle: Profile and Information

The bald eagle (Haliaeetus leucocephalus) is a well-known bird of prey native to North America.

A bald eagle has two other known subspecies, pairing a species with the white-tailed eagle (Haliaeetus albicilla).

Its range includes most of Alaska and Canada, northern Mexico, and the contiguous United States.

It is seen near seas with a large food supply and old trees for building nests.

The bald eagle is regarded as an opportunistic feeder that preys mostly on fish when it dives down and snatches the fish from the water with its talons.

Bald eagles build the largest nest of any North American bird and are recorded as the largest nest ever built by any bird species, up to 8.2 ft (2.5 m) wide, 13 ft (4 m) deep, and 1.1 short tons (1 metric ton) in weight. Sexual maturity begins at the age of 4-5 years.

The term bald, given to the bald eagle, was derived from an old meaning, ‘’white-headed,’’ which means the bald eagles are not bald.

Adults are mostly brown with a white head and tail. Both sexes look the same in plumage, but females are 25% larger than males.

The beak is hooked and large. The plumage of the young eagle is brown.

It is the national bird of the United States of America. The bald eagle is presented on the seal.

In the 20th century, it was on the brink of local extinction in the contiguous United States.

The eagle population has recovered, and on July 12, 1995, it was removed from the U.S. Government of Endangered Species and was added to the list of threatened species.

On June 28, 2007, it was declared that the bald eagle was no longer on the List of Endangered and Threatened Wildlife in the contiguous states.

Scientific Classification

Characteristics

The plumage of a fully-grown bald eagle is dark brown with a white head and tail. The tail of an adult eagle is moderately long and slightly wedge-shaped.

Both males and females look the same in plumage coloration, but the sexual difference is evident in the species, and females are 25 percent larger than males.

The feet, irises, and beak are bright yellow. The toes are powerful but short with large talons, and the legs are feather-free.

The strongly developed talons of the hind toes are used for dissecting the vital area of prey while it is held still by the front toes. The beak is hooked and large with a yellow cere.

The plumage of the young eagle is a dark brown overlaid with spikey white streaking until the fifth (rarely fourth) year when it is sexually matured.

The bald eagle has been recognized as the largest true raptor (accipitrid) native to North America. The only large raptor-like bird species is the California condor (Gymnogyps califonianus).

The bald eagle has a body mass of 28 to 40 in (70 to 120 cm). The total wingspan is between 5 ft 11 in and 7ft 7 in (1.8 and 2.3 m), and the mass is between 6.6 and 13.9 lb (3 and 6.3 kg). The females are 25 percent larger than males, averaging as much as 12 lb (5.6 kg), and the males weigh about 9.0 lb (4.1 kg).

The size of the eagle corresponds with the location and generally follows Bergmann’s rule since the bird grows faster in size, further away from the equator and the environment. For example, species from South Carolina average 7.2 lb (3.27 kg) in mass and 6ft 2 in (1.88 m) in wingspan, which is smaller than its northern cousin.

The largest eagles are found in Alaska, where large female eagles weigh more than 15 lb (7 kg) and span 8ft 0 in (2.44 m) across the wing. An Alaskan fully-grown female eagle was recorded as outsized, weighing up to 16 lb (7.4 kg).

The young eagle call includes kleekkikikikik, chirping whistles, and weak staccato somewhat similar to that of a gull’s call. Its call is slightly harsher and shriller than the fully-grown eagle.

Habitat

The bald eagle appears during its mating season in any American wetland habitat, such as marshes or large lakes, rivers, seacoast, or other large bodies of open water with an unlimited supply of fish.

Some research has shown that a total body of water with a circumference greater than 7 mi (11 km) and lakes with a measurement greater than 4 sq mi (10 km²) is necessary for mating.

The bald eagle mostly uses mature stands of hardwood or coniferous trees for roosting, nesting, and perching. If a tree is selected, it must have good visibility, be over 66 ft (20 m) tall, have an open environment, and be available to prey.

If the trees are in standing water, such as a mangrove swamp, the nest can be positioned lower, as low as 20 ft (6 m) above the ground. If the tree is in dry land, the nest may be from 52 – 125 ft (16 – 38 m) in height.

In the Chesapeake Bay, nesting trees are usually 92 ft (23 cm) in total height and 32 in (82 cm) in diameter, while in Florida, nesting trees are usually about 9.1 in (23 cm) in diameter and 75 ft (23 m) in height.

Forests or trees used for nesting should have a canopy cover greater than 60 percent and less than 20 percent and be close to water.

Most nests have been seen within 660 ft (200 m)of open water. The largest distance recorded from a bald eagle nest to open water was over 1.9 mi (3 km) in Florida.

The bald eagles are normally aware of human events while nesting and are mostly seen in locations with minimal human commotion.

It selects an area greater than 0.75 mi (1.2 km) from low-density human commotion and greater than 1.1 mi (1.8 km) from medium-to-high-density human commotion.

While in winter, bald eagles are always less disturbed. They usually stay in an area with abundant prey and (in northern climes) almost unfrozen waters. The bald eagles are famous fliers and soar on thermal convection currents.

It attains a speed of 35 to 43 mph (56 to 70 km/h) when soaring and flapping and approximately 30 mph (48 km/h) while carrying prey. Its diving speed is between 75 to 99 mph (120 to 160 km/h), though it hardly dives down.

Despite their flying skills, the bald eagle is surprisingly maneuverable despite being slower than the golden eagle in flight (especially during dives). Hunters shooting from planes said they were harder to hunt while flying than golden eagles, as they would dive down as soon as it approached.

Bald eagles have also caught birds and thrust their talons into their breast. It is temporarily migratory, depending on the area.

If its location has excess water, it stays there, but its water becomes limited during the winter, making it stressful to obtain food; it migrates to the coast or the south.

Diet and Feeding

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Bald eagles are clever raptors who can devour a large amount of food. Among their varieties, fish is the main source of their diet.

More than 400 species are part of the bald eagle diet spectrum, far greater than the ecological equivalent in past years.

Despite being less numerous, the bald always comes second among all North American accipitrids. It is always behind the red-tailed hawk in the number of prey species killed.

In Southeast Alaska, fish make up 66% of the year’s bald eagle diet, and 78% are brought by the parent to the nest. Eagles inhabit the Columbia River Estuary in Oregon, where they have been seen to rely on fish for 90% of their diet intake. Almost 100 fish species have been seen to be in the bald eagle’s selective diet.

In the Pacific Northwest, spawning salmon and trout make up the bald eagle diet throughout the summer falls. Southeast Alaskan eagles mostly prey on pink salmon (Oncorhynchus gorbuscha), coho salmon (O. kisutch), and, more locally, sockeye salmon (O. nerka) with Chinook salmon (O. tshawytscha), due to their enormous size (26 – 40 lb (12 – 18 kg) average adult size) mostly being taken only as carrion.

In Oregon’s Columbia River Estuary, the most selective prey species were common carp (Cyprinus carpio; 10.8%), largescale sucker (Catostomus macrocheilus) (17.3% of prey species found there), and American shad (Alosa sapidissima; 13%).

Eagles that inhabit the Chesapeake Bay in Maryland were recorded to subsist largely on white bass (Morone chrysops), American gizzard shad (Dorosomacepedianum), and threadfin shad (Dorosomapetenense).

Bird species that are often selected as prey by eagles are always medium-sized; they include the American coot (Fulica americana), western grebes (Aechmophorus occidentalis), and mallards (Anas platyrhynchos).

American herring gull (Larus smithsonianus) are the most selected avian prey for eagles living in areas like Lake Superior.

Enormous water birds are also hunted occasionally by adult bald eagles. They include brown pelicans (Pelecanus occidentalis), common loons (Gravis immer), great blue herons (Ardea Herodias), great black-backed gulls (Larus marinus), fledging American white pelicans (P. erythrorhynchos), sandhill cranes (Grus canadensis) and Canada geese (Branta canadensis). Bald eagles always prey on such birds at all ages, from hatched eggs to fully grown adults.

Mammalian targets include ground squirrels, rabbits, hares, muskrats (Ondatra zibethicus, raccoons (Procyon lotor), deer fawns, and beaver (Castor canadensis). Moreover, adults are sometimes targeted, such as adult beavers and raccoons.

Other mammalian prey is always taken by a bald eagle as full-grown, such as red and Arctic foxes (Vulpes vulpes & Vulpes lagopus), Virginia opossum (Didelphis virginiana), striped skunks (Mephitis mephitis), and nine-banded armadillos (Dasypusnovrmcinctus). A full-grown bobcat (Lynx rufus) is also targeted.

In coastal New Jersey, 14 – 20 researched eagle nests included remains of reptiles. The main prey is mostly diamondback terrapin (Malaclemys terrapin), young common snapping turtles (Chelydra serpentina), and common musk turtles (Sternothernusodoratus). In New Jersey, a nest of small adults measured up to 3 – 6.7 in (9.2 – 17.1 cm).

The bald eagles are known to be larger in numbers in North America than the golden eagles; the bald species has several 150,000 members. The number of golden eagles that inhabit North America is half that of the number of bald eagles that live there.

Due to its lack of numbers, golden eagles have been outnumbered by the bald eagle in attaining food sources. Despite the differences between these species, it has been recorded that they work together to kill snow geese without violence during winter. They have been seen stealing prey from herons, otters, and ospreys.

Reproduction

Bald eagles are sexually mature at the age of 4 or 5. It has been seen that bald eagles mate for life.

Sometimes, if one of the partners dies, the one left will find a new mate. Bald eagle lovemaking includes spectacular calls, flight displays, and elaboration.

The flight includes chases, cartwheels, and swoops; they fly high, lock talons, and free-fall, departing before reaching the floor.

Normally, an area with a mature couple will have as large as 0.62 – 1.24 mi (1 – 2 km) of waterside environment.

Unlike most species of birds, bald eagles mate as early as mid-February and lay eggs in late February (Mostly during deep snow in the North). The eggs are kept in incubation for at least mid-March.

Chicks hatch from mid-April to early May, and the young start flying in late June to early July. The nest is the largest of any ever recorded in North America; it is used yearly, and they bring new materials each year.

Eventually, it may measure up to 8.2ft (2.5 m) across, 13ft (4 m) deep, and 1.1 short tons (1 metric ton); one nest in Florida was seen to be 9.5ft (2.9 m) across, 20ft (6.1 m), and weighing up to 2.7 metric tons (3 short tons).

A young eagle can weigh up to 6.0 oz (170 g) daily and has the quickest growth rate of any North American bird species.

The young eagle plays tug of war, practices tearing things with their talons, and flaps and stretches their wings.

For the next 4 – 5 years, the young eagle flies off for food until they reach maturity and are ready to reproduce.

The total lifespan of a bald eagle living in the wild is 20 years; there is a record of a bald eagle reaching the age of 38.

A bald eagle in captivity lives a bit longer; for instance, a bald eagle in New York lived for about 50 years.