Species Spotlight: Bald Eagle

January 12, 2009, 1:44 pm

One of the most recognizable symbols of the United States, the bald eagle (Haliaeetus leucocephalus) deserves its reputation as a fierce and flexible carnivore. A powerful flier, it can reach speeds of up to 44 miles per hour. It prefers to live near seacoasts, rivers, large lakes and water bodies filled with fish. It’s a large, majestic bird and formidable predator with exceptional eyesight that allows it to see fish underwater from several hundred feet in the air.

Description: The adult bald eagle is covered in brown feathers except for its white head and tail, and bright yellow feet. Among their most striking features are their bright yellow irises and beaks. Juveniles are completely brown except for the yellow feet and may be confused with Golden eagles. Bald eagles are large birds, with a body lengths ranging from 28 to 42 inches, wings spanning 72 to 96 inches, and weights falling between 6.6 to 15.5 lbs. Females and males are identical in coloring but females are about 25 percent larger than males.

Park habitat: Two recognized subspecies of bald eagles exist—H.I. leucocephalus found from roughly the latitude of San Francisco south, and H.I. washingtoniensis, the northern subspecies. Since bald eagles depend on open waters to fish for their food, the southern subspecies may migrate south. Optimal habitat for eagles includes large bodies of open water—greater than four square miles in area—and old-growth stands of coniferous or hardwood trees for perching, roosting or nesting.

Diet: Although they depend on fish as their primary food source, the bald eagle’s diet is opportunistic and varied. They may regularly feed on carrion in the winter when food is scarce, taking advantage of carcasses as large as those of a whale. You may also notice them scavenging or stealing from picnic or campsites and dumps. Their mammalian prey includes rabbits, raccoons, muskrats, beavers, sea otters and deer fawns.

Threats: Although it was delisted in June of 2007, the bald eagle spent almost four decades on the endangered species list due to hunting, trapping, habitat loss and the widespread use of a now banned chemical, DDT. A synthetic pesticide, DDT was not lethal to the adult eagle but did render affected birds sterile and weaken the strength of their eggshells. In 1984, the National Wildlife Federation listed hunting, power-line electrocution, and collisions in flight as the leading causes of eagle deaths. Bald Eagle populations have also suffered due to oil, lead, and mercury pollution, and by human and predator intrusion. However, with the 1984 ban on DDT, the bird’s populations rebounded significantly. A current threat to the eagle involves lead poisoning as the birds feast on dear or other carrion shot by hunters—when the hunters leave the shot carcass, the meat becomes neurotoxic as the bullet leaks. Programs are in place to educate hunters and rescue poisoned eagles.

Interesting fact: Benjamin Franklin wrote a famous letter after the revolutionary war in protest of the eagle as the national symbol. Writing to his daughter from Paris in 1784, he criticized the choice of the eagle and suggested the wild turkey as a more apt symbol of American values. He wrote that the bald eagle was “a bird of bad moral character,” who was too lazy to fish for itself and so stole from the osprey. He also sited the bald eagle as "a rank coward" that could be scared from its perch by the much smaller kingbird. Franklin further described the wild turkey as "a much more respectable bird." While he did consider the turkey a little vain and silly, he heralded it for its courage. Even so, the bald eagle remains the emblem of the United States, a formidable predator by any standard, and a majestic biological study.