Bald Eagles

Characteristics

Adults are identified by the white head and tail with a large, yellow bill. Juveniles are mostly dark, with blotchy white on underwing coverts, axillaries and tail. Often confused with Golden Eagle juveniles, but they have a more sharply defined pattern. Bald eagles also have a larger head and shorter tail.

Species Specifics

There are 59 species of eagles; bald eagles fall under the 'sea eagle' grouping.

Physical Characteristics

Powerful feet with sharp talons & spicules (bumps on bottom of feet that help to grip food), and strongly hooked beaks for tearing up their food. They also have the stamina and ability to migrate (though they take advantage of updrafts whenever possible).

Ecology

Habitat

Mostly near water, including rivers, lakes, and coastal sites to an altitude of 6,500 feet

Distribution

Home Range: Minimum territory size (defended part of home range) is estimated at ~150 acres. Entire home ranges are known to be about 5,000 acres, though vary depending on area, season, food availability, and breeding status.

Diet

Carnivorous, Mostly fish and carrion

Ecological Web

Considered an apex predator in their food web, though they are also scavengers. They remove disease and chemicals from the ecosystems by eating carrion (and build up high levels of chemicals in their own bodies).

Activity and Behavior

Activity Pattern

Diurnal; move out in early in the morning to forage. They frequently sit in a favored perch tree away from disturbance and after a meal they will spend most of the day sunning, preening, and, if the weather is too warm, they may perch in the shade under the crown of a tree.

Behavior

In winter, large numbers of bald eagles gather at the spawning grounds of salmon. Hundreds of salmon die shortly after spawning, which makes it easy for the eagles to feed on dead or dying fish on the shore, without entering the water. They also steal food from other predatory birds and often fight among themselves for food. Regularly pirates prey from conspecifics and other raptors, especially Osprey

Social Behavior

Solitary or in pairs when breeding, though nests are sometimes in very loose, small colonies. Winter roosts can hold 1,000+ individuals where there are abundant food sources.

Reproductive Behavior

Courtship displays commonly involve the male diving at the female flying below. She rolls and raises her legs to him and they can grasp talons and fall toward the ground. They nest in mature or old-growth trees, snags, cliffs, rock promontories, and artificial structures (such as power poles and communication towers). Usually nests are about 4-6 feet in diameter and 3 feet deep and frequently return to the same nest every year. Each season they add more material and nest can weigh half a ton. The largest nest measured was nearly 10 feet wide and over 19.5 feet deep.

Offspring

Generally 1-3 (though 4 have been recorded). Approximately 70% survive their first year of life.

Conservation

Status

Listed as Least Concern by IUCN; CITES Appendix II, protected under Migratory Bird Treaty Act, Bald & Golden Eagle Protection Act; Population Trend: Increasing

Historical

The Bald Eagle is the national animal of the United States of America. It was also chosen in 1782 as the emblem of the United States of America, because of its long life, great strength and majestic looks. The bald eagle plummeted from abundance to endangered status; only 417 pairs were left in 1963. DDT was the main reason for the decline, causing non-viable eggs, but the Bald Eagle story is one of SUCCESS and shows that recovery is possible when we have the Endangered Species Act and local institutions that can help. Bald Eagles are breeding once again in Central California Coast Region, thanks to a successful re-introduction project conducted by Ventana Wildlife Society, in cooperation with U.S. Fish and Wildlife Service and California Department of Fish and Game. While their goal was to get to 4 breeding pair, there are now over 30 and counting! This was the biggest Bald Eagle rebound in California.

Current Threats

Our Role

Oakland Zoo supports Ventana Wildlife Society who has successfully worked to increase bald eagle populations. Oakland Zoo works to spread the word about rat poison and its deadly effect on raptors.