The bald eagle is truly an all-American bird - it is the only eagle unique to North America. It ranges over most of the continent, from the northern reaches of Alaska and Canada down to northern Mexico. The bald eagle, our national symbol, is listed as endangered under the Endangered Species Act in 43 of the lower 48 states and listed as threatened in Michigan, Minnesota, Oregon, Washington, and Wisconsin. (There are about 40, 000 bald eagles in Alaska and none in Hawaii. ) However, bald eagles have improved greatly in numbers, productivity, and security in recent years.
Male bald eagles generally measure 3 feet from head to tail, weigh 7 to 10 pounds, and have a wingspan of about 6 1/2 feet. Females are larger, some reaching 14 pounds and having a wingspan of up to 8 feet. This striking raptor has large, pale eyes; a powerful yellow beak; and great, black talons. The distinctive white head and tail feathers appear only after the bird is 4 to 5 years old. Bald eagles are believed to live 30 years or longer in the wild, and even longer in captivity. They mate for life and build huge nests in the tops of large trees near rivers, lakes, marshes, or other wetland areas.
Nests are often reused year after year. With additions to the nests made annually, some may reach 10 feet across and weigh as much as 2, 000 pounds. Although bald eagles may range over great distances, they usually return to nest within 100 miles of where they were raised. Bald eagles normally lay two to three eggs once a year and the eggs hatch after about 35 days. The young eagles are flying within 3 months and are on their own about a month later. However, disease, lack of food, bad weather, or human interference can kill many eaglets; sometimes only about half will survive their first year.
The staple of most bald eagle diets is fish, but they will feed on almost anything they can catch, including ducks, rodents, snakes, and carrion. I winter, northern birds migrate south and gather in large numbers near open water areas where fish or other prey are plentiful. Wildlife experts believe there may have been 25, 000 to as many as 75, 000 nesting bald eagles in the lower 48 states when the bird was adopted as our national symbol in 1782. Since that time, the bald eagle has suffered from habitat destruction and degradation, illegal shooting, and contamination of its food source, most notably due to the pesticide DDT. By the early 1960 s there were fewer than 450 bald eagle nesting pairs in the lower 48 states. Bald eagles have few natural enemies.
But in general they need an environment of quiet isolation; tall, mature trees; and clean waters. Those conditions have changed over much of the bald eagle's former habitat. History notes many wilderness areas were cleared for farms and towns, and virgin forests were cut for timber and fuel. And, today, an increasing number of people flock to the nation's waterways for recreation, with growing impacts on bald eagle habitat. Meanwhile, these birds of prey became prey themselves. Although primarily fish and carrion eaters, bald eagles and other raptors were seen as marauders that killed chickens, lambs, and other domestic livestock.
As a consequence, large numbers were shot by farmers, ranchers, and others. In 1940, noting that the national bird was "threatened with extinction," Congress passed the Bald Eagle Protection Act which made it illegal to kill, harass, possess (without a permit), or sell bald eagles. In 1967, bald eagles were officially declared an endangered species (under a law that preceded the Endangered Species Act of 1973) in all areas of the United States south of the 40 th parallel. Federal and state government agencies, along with private organizations, successfully sought to alert the public about the bald eagle's plight and to protect its habitat from further destruction.