American Bald Eagle
Scientific Fact Sheet

Scientific name - Haliaeetus leucocephalus

Order: Falconiformes

Family: Accipitridae, Genus Haliaeetus, Species leucocephalus
The Accipitridae family,, which also includes hawks, kites, and old-world vultures. Scientists loosely divide eagles into four groups based on their physical characteristics and behavior. The bald eagle is a sea or fish eagle.

Subspecies: There are two subspecies of bald eagles. The "southern" bald eagle, H. l. leucocephalus, is found in the gulf states from Texas and Baja California across to South Carolina and Florida, south of 40 degrees north latitude. The "northern" bald eagle, H. l. alascanus, is found north of 40 degrees north latitude across the entire continent. The largest number of northern bald eagles are in the Northwest, especially in Alaska. The "northern" bald eagle is slightly larger than the "southern" bald eagle. The two subspecies integrate with one another in the central and northern states.

Size: The female bald eagle is 35 to 37 inches, slightly larger than the male. The wingspan of a female ranges from 79 to 90 inches. The male bald eagle has a body length from 30 to 34 inches. The wingspan of a male ranges from 72 to 85 inches. Mature bald eagles weigh from ten to fourteen pounds. Females are about 30% larger than males. Northern birds are significantly larger than their southern relatives.

Color: The white head and tail and the large dark brown body and wings are the features that distinguish adult bald eagles from other raptors. The adults also have yellow eyes, cere (base of beak, including nostrils), bill, legs, and feet with black claws. There are at least five different plumages that apparently correspond with age; Juvenile, Basic I, Basic II, Basic III, and Adult. Juvenile bald eagles are a mixture of brown and white; with a black bill in young birds. The distinctive adult plumage develops when they're sexually mature, at about 4 or 5 years of age.

Life expectancy: Wild bald eagles may live as long as thirty years, but the average lifespan is probably about fifteen to twenty years. Eagles sit at the top of the food chain, making them more vulnerable to toxic chemicals in the environment, since each link in the food chain tends to concentrate chemicals from the lower link.

Diet: Bald eagles feed primarily on fish, but will hunt other animals like small mammals, waterfowl, snakes and carrion. Nearly all the fish that eagles catch are either dead or in shock due to winter temperatures. Eagles will consume approximately 1 to 2 pounds a day.

Tolerance to cold temperatures: A bald eagle's skin is protected by feathers lined with down. The feet are cold resistance because they are mostly tendon. The outside of the bill is mostly nonliving material, with little blood supply.


Amy Reichardt of the World Bird Sanctuary in St. Louis County
helps a young visitor build a model life sized bald eagle nest 

Fidelity and nesting: Once paired, bald eagles remain together for life. If one dies, the survivor will not hesitate to accept a new mate. Bald eagles build some of the biggest nests in the world averaging 7 feet across and 5 feet deep. The eagles return to the same nest annually with improvements made each season. The female will lay 1 to 3 chicken sized white eggs in the spring. The eggs will hatch after about 35 days and both parents take on parental duties until the young are about 12 weeks old when they are old enough and strong enough to fly on their own.

Voice: Shrill, high pitched, and twittering are common descriptions used for bald eagle vocalizations. Eagles do not have vocal cords. Sound is produced in the syrinx, a bony chamber located where the trachea divides to go to the lungs. Bald eagle calls may be a way of reinforcing the bond between the male and female, and to warn other eagles and predators that an area is defended.

Skeleton: An eagle's skeleton weighs about half a pound (250 to 300 grams), and is only 5 or 6 percent of its total weight. The feathers weigh twice that much. Eagle bones are light, because they are hollow. The beak, talons, and feathers are made of keratin.

The wings and soaring: An eagles wings are long and broad, making them effective for soaring. To help reduce turbulence as air passes over the end of the wing, the tips of the feathers at the end of the wings are tapered so that when the eagle fully extends its wings, the tips are widely separated. To help them soar, eagles use thermals, which are rising currents of warm air, and updrafts generated by terrain, such as valley edges or mountain slopes. Soaring is accomplished with very little wing-flapping, enabling them to conserve energy. Long-distance migration flights are accomplished by climbing high in a thermal updraft, then gliding downward to catch the next thermal updraft, where the process is repeated.

Eagles can fly at speeds up to 65 miles per hour at level flight and reach speeds of 150 miles an hour in a dive. The wings are not only equipped for flight but can be used as paddles to swim to shore if a caught fish is to heavy to carry.

The tail: The tail is very important for flight and maneuvering. While the bald eagle is soaring or gliding in flight, the tail feathers are spread, in order to attain the largest surface area and increase the effect of thermals and updrafts. The tail also helps to brake the eagle when landing and assists in stabilization during a controlled dive or swoop toward prey. The strength of the feathers and the follicles holding the feathers is quite impressive, while watching the tail move back and forth and up and down during maneuvers.

Feathers: Bald eagles have 7,000 feathers. Eagle feathers are lightweight yet extremely strong, hollow yet highly flexible. They protect the bird from the cold as well as the heat of the sun, by trapping layers of air. To maintain its body temperature an eagle simply changes the position of its feathers. While an eagle suns itself on a cold morning, it ruffles and rotates its feathers so that the air pockets are either opened to the air or drawn together to reduce the insulating effect. Feathers also provide waterproofing and protection, and are crucial for flight. Feather structure makes pliability possible. Overlapping feathers can form a dense covering, which the birds can open or close at will. The bald eagle has several layers of feathers, each serving a different function. Under the outer layer of feathers is an inner layer of down or smaller feathers.

The inter locking of feathers is an astonishing design of nature. The feathers enable eagles to live in extremely cold environments. Eagles do not have to migrate to warmer areas each year to fulfill temperature requirements, they migrate to available food supplies. A lone eagle feather is believed to convey great power. North American Indians incorporated the eagle's primaries and tail feathers into their ceremonies and legends.

The beak and talons: The hook at the tip of the beak is used for tearing. Behind the hook, the upper mandible, the edge sharp enough to slice tough skin, over laps the lower, creating a scissors effect. A bald eagle's beak is a strong weapon, but is also delicate enough to groom a mate's feathers or feed a small portion of food to a newly hatched chick. Talons are important tools for hunting and defense. Eagles kill their prey by penetrating its flesh with their talons. The talons are very strong and can grasp prey at strengths of 2600 pounds per square inch. This is the equivalent to driving a nail through concrete. The beak and talons grow continuously, because they are made of keratin, the same substance as our hair and fingernails. The beak of a captive eagle is not worn down naturally, so must be trimmed annually.

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