Bald Eagle

California Trail

Location

In the Zoo

Scientific Information

Scientific Name: Haliaeetus leucocephalus
Class: Aves
Order: Falconiformes
Family: Accipitridae
Genus: Haliaeetus

Size

Male

Female

Height: 30-36 inches 35-38 inches
Wingspan: 7 feet 5.5-7.5 feet
Weight: 7-14 pound 7-14 pounds
Maturity: 5-6 years 5-6 years

Lifestyle and Lifespan

Diet: Carnivorous
Activity Timeframe: Diurnal
Interactivity: Solitary
Sexual Dimorphism: Yes
Gestation: 35 days
Lifespan in the Wild: 15-25 years
Lifespan in Captivity: 50 years

Geographic Range

Canada, Mexico, Saint Pierre & Miquelon, United States (Vagrant in Belize, Bermuda, Ireland, Puerto Rico, Russian Federation, Virgin Islands)

Conservation

Status in the Wild:
Threats: Habitat Loss

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 Web

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

In 1782, the country may have had as many as 100,000 nesting eagles. In the first half of the 20th century, bounties were paid for Bald Eagles in Alaska. About 150,000 were killed there during that period; it is unclear whether their population has genetically recovered from such a large-scale slaughter. In the 1960s and 1970s it suffered further huge losses through adverse effects of pesticides, especially DDT. This led to many local extinctions and widespread breeding failures (DDT was banned in 1972).

Current Threats

Habitat Loss

Our Role

Exhibit and Educate

How You Can Help

Use nontoxic pesticides, herbicides, fertilizers & other chemicals; use all other chemicals only in accordance to law. Help protect old growth trees, particularly within a mile from water, and other roost/nest sites and important foraging areas. Avoid boating and fishing near foraging areas & during peak feeding times. Contact representatives and government organizations to express your interest in bald eagle conservation.

Fascinating Facts

The golden eagle is the only North American member of a large worldwide group of 'true' eagles, thought to be closely related to buteos. Conversely, the bald eagle is a member of a group known as fish-eagles, which are thought to be more closely related to kites.

Chosen as the national bird of the United States on June 20, 1782. Several people opposed this idea, including Benjamin Franklin. A century later, ornithologist Arthur Cleveland Bent said bald eagles "hardly inspire respect and certainly do not exemplify the best in American character."

Bald eagles are considered 'lazy' because they pirate food so often and eat carrion. What we consider as laziness is actually competence. Inept birds waste energy searching for food; adult eagles are free to sit and conserve energy precisely because they can secure food at will.

The scientific name translates to sea (halo) eagle (aeetos) with a white (leukos) head (cephalus)

References

National Geographic Field Guide to the Birds of North America (4th Edition)

Bird: The Definitive Visual Guide Audubon 2007

BLM Bald Eagle

A Grosset All-Color Guide: Birds of Prey 1970

Encyclopedia of Birds: A Comprehensive Illustrated Guide by International Experts (2nd Edition) 1998.

Raptors of the World. James Ferguson-Lees ad David A. Christie 2001

Reader's Digest Book of North American Birds. 1990.

US Fish and Wildlife Service Bald Eagle Fact Sheet

The Sibley Guide to Bird Life and Behaviour. Chris Elphick, John B. Dunning, Jr., David Sibley 2001

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