Binghamton Zoo Animals

Bald Eagle

(Hailiaeetus leucocephalus)
Order: Falconiformes
Family: Accipitridae
Genus: Haliaeetus
Species: Haliaeetus leucocephalus

HABITAT AND RANGE: Bald Eagles live along shores of lakes and rivers. They are native only to North America, except for a few in eastern Siberia. The extent of their range has decreased during the 20th century, but it is slowly increasing due to extensive hacking programs and the banning of highly persistent pesticides.

PHYSICAL CHARACTERISTICS: Like most birds of prey, the female is larger than the male, and she is usually around 42” high, has a 7-8 foot wingspan, and weighs 10-14 pounds. The male is usually about 35” high, has a 6 ½ -7 foot wingspan, and weighs 8-10 pounds. It is interesting to note that the young are often larger and heavier than either of the parents. Apparently, as the eagle matures, its bones contract slightly, and it loses weight, since as a flying adult, it exercises more. A bald eagle has more than 7,000 feathers, but all of them together weigh less than 21 ounces. In fact, 30 feathers way weigh less than a penny! Being light weight is very important for flight. The entire skeletal system of an eagle is just slightly more than one half pound; the 8 foot long wings weigh less than 2 pounds. Although a bald eagle looks big, it usually weighs 2 pounds less than the average house cat.

ADAPTATIONS: Bald eagles are diurnal predators. They are non-migratory except when winter is severe enough to freeze over the water sources upon which they rely on for food.

DIET: The Bald eagle’s diet consists primarily of fish (60-90%). Eagles are remarkable predators. While soaring at 500 feet, an eagle can spot a fish a mile away, and then swoop down on it at 100 mph. After swinging its talons forward, it plucks up the fish and seeks a perch from which to feed. Eagles will also eat dead fish and are not above stealing fish from osprey. Other food includes carrion, rabbits, turtles, waterfowl and other small birds, small rodents, and crabs. They eat only 5-10% of their body weight a day (about a pound of food). Captive eagles may be fed fish, chicks, mice, rats, or a commercially prepared Bird of Prey diet (BOP). In order to ensure a complete diet, these food items are alternated.

REPRODUCTION AND DEVELOPMENT: Nesting is often preceded by an aerial courtship display. Locking talons, the pair dives and somersaults across the sky. Bald eagles mate for life, and both help to build the nest (aerie, or eyrie). The aerie site is usually 50-100 feet off the ground in a large tree situated near water. The completed nest, 5 feet across and 41/2 feet deep, may take four days to build. Often eagles will return to the same nest year after year, and add about a foot of new twigs and branches. One of the largest nests ever observed was in St. Petersburg, FL; occupied for at least 35 consecutive years, it was 20 feet deep, 91/2 feet in diameter, and weighed 2 tons! Although it may appear that the birds purposefully choose to nest among dead branches, such is not the case. Oils from fish that have been brought to the nest seep through the bark and stop the upward flow of sap, eventually killing the branch. The female lays only 2 eggs each season (usually March or April in this area). The eggs, unmarked and dull white, are actually quite small for such a large bird; it is only about an inch longer and wider than a chicken egg. After 35 days, the eggs begin to hatch, taking about 18 hours for the eaglet to cut its way out. Since the parents begin to incubate the eggs as soon as the first is laid, the young hatch a few days apart. Often, the youngest will not get enough food to survive; thus, these birds are typically the ones removed for captive raising and future release programs (“hacking”). The downy white chicks develop drab brownish-black juvenile feathers in 3-4 weeks. By the time the birds are 6-7 weeks old, they are able to walk around the nest, but will be 3 months old before they begin to fly. Unlike most birds, the eaglets often return to the nest after their maiden flight; sometimes the parents will continue to feed them there. However, when fall approaches, the young birds are on their own. At the end of the first year the white head and tail feathers that characterize the adults begin to appear, but will not be completely in place until the bird is 4-5 years old, and sexually mature. Bald eagles can live for 35-45 years.

STATUS IN WILD: Threatened