Northern Prairie Wildlife Research Center
Description: The bald eagle is a large raptor, measuring 31-37 inches (79-94 cm) in length. Its wingspan is 6.5-8 feet (2-2.5 m). The adult (4-5 years) has a uniform dark brown body contrasting with a white head and tail. Its eyes and beak are yellow. Immature birds have dark plumage mottled irregularly with white and lack the adult's white head and tail. Immature bald eagles have dark eyes and a dark beak.
Habitat and Habits: The bald eagle is almost always found near water, primarily on river systems, large lakes, reservoirs and coastal areas. These birds are mainly scavengers, feeding on dead and dying fish, usually early in the morning. Although capable of catching live fish at the water's surface, they also steal fish from other birds, such as osprey. Waterfowl, rabbits, rodents and other animals, taken mostly as carrion, are also eaten.
Bald eagles generally roost together in large mature trees surrounded by a buffer of smaller trees. Daytime perches are usually within 180 feet of water.
Nests are usually located in trees about 10-15 feet aboveground, and are used year after year with sticks and debris added. One nest reportedly weighed over two tons after 35 years of use. Nests usually contain two eggs which hatch in 35 days. Young remain in the nest for about 75 days. Both parents feed the young and protect the nest site from potential predators.
Distribution: The bald eagle has a widespread distribution throughout Canada and portions of the United States. A northern race occurs throughout Alaska, Canada and across the northern United States from the Paciflc Northwest to the Great Lakes and Maine coastline.
This species historically nested in southeastern South Dakota. Reservoirs may offer suitable habitat for future breeders. In the neighboring states of North Dakota and Nebraska, bald eagles have recently begun nesting for the flrst time in many years. Bald eagles overwinter in the Black Hills, the lakes region of northeastern South Dakota and along the Missouri River (in the Pierre-Fort Pierre/Oahe Dam Area, the Karl Mundt National Wildlife Refuge/ Fort Randall Dam Area and portions of the Missouri National Recreational River).
Conservation Measures: The bald eagle is unique to North America and was chosen by Congress as our national symbol in 1782. The decline of the bald eagle throughout its range was largely the result of DDT residue accumulation in fish.
The bald eagle was formally listed in 1978 as federally threatened in Minnesota, Wisconsin, Michigan, Oregon and Washington, and endangered in the remaining lower 48 states. Pesticide contamination caused thinning of egg- shells, resulting in premature egg breakage and death of the embryo, as well as in the poisoning of adults.
Since the banning of DDT in 1972, bald eagle populations have rebounded. However, loss of habitat and interference with nesting habitat, loss of traditional nest trees and illegal killing still jeopardize the bald eagle. Federal and state conservation agencies implement strict management guidelines to protect existing populations, primarily by minimizing human disturbance. This may involve establishing a buffer zone (450 m on water, 250 m on land, 500 m from nest) which protects feeding areas, perch and nest trees and the general area surrounding active nests and wintering areas.
South Dakota offers the opportunity to view impressive wintering concentrations of bald eagles. As an endangered species, the bald eagle is protected from harassment. When observing these birds during the winter, do not disturb them. It is not only illegal, but is dangerous to the eagles' welfare, since valuable energy is used to fly away.