North Cascades

Threatened and Endangered Species

Bald Eagle Haliaeetus leucocephalus Bald eagles are large raptors; they measure 31-37 inches in height with a wingspan of 70-90 inches. An adult bald eagle will weigh between eight and 12 pounds. Young birds, usually less than 5 years old, are brown or mottled (blotchy brown) all over. Adult birds have dark brown bodies, a yellow beak, with a white head and tail. Bald eagles mate for life and return to the same nesting territory each year. They may use the same nest for several years to raise one or two chicks. Pesticides were largely, if not exclusively, responsible for causing the bald eagle to be federally listed as an endangered species. Chemicals sprayed on agricultural fields washed into the rivers and fish bodies absorbed them. Small vegetation-eating animals consumed remaining chemicals in the fields. These contaminated fish and mammals were eaten by bald eagles. The chemicals did not always kill the organisms as they passed through the food chain, but they did build up in the organism's fatty tissues. Chemicals that were ingested by the bald eagle caused the shells of the bald eagles' eggs to form so thin that they would break when the adults attempted incubation. The population of bald eagles was upgraded to threatened after the restricted use of certain farming chemicals. Concern about the eagle's recovery still lingers, stemming from the loss of habitat to development and the decline of salmon, an important winter food source.