Wild Things: Bald Eagle (Haliaeetus leucocephalus)

This iconic bird of prey is the national bird of the United States. The white head and tail of the adult contrast with the dark body and wings, giving it the appearance of being bald, thus the name. The yellow beak and nasal cere compliment the white head and neck feathers. Juveniles are dark brown with scattered white feathers. The head and tail are also brown, gradually fading to white as the bird matures.

Sexes are similar, but females are smaller than males. The Bald eagle's body can reach over 3 feet in length and the wingspan stretch to over 7 feet. It is one of the largest raptors in North America, with only the California condor and Steller's sea eagles being larger. Eagles may be distinguished from other large soaring birds at a distance by the profile: eagles soar with wings spread horizontally while vultures and hawks show an uptilt or dihedral in their spread wings.

They are found year-round in the northwestern states, along the Mississippi river watershed, in Florida and the southeastern coastal states, and in the far northeast. Winter habitat is widespread across the central and southern U.S. and they are found only in breeding season across Canada and throughout much of Alaska. In winter Bald eagles are common along the Rio Grande and may be seen regularly at the Bosque del Apache National Wildlife Refuge. In the breeding season bald eagles inhabit wetlands and coastlines of lakes and rivers where fish are abundant.

Bald eagles are opportunistic predators and scavengers, hunting from a perch or by soaring over land or water. Where fish are available, they can form a primary dietary component, with the eagle swooping down to the surface of the water and snagging a fish out of the water with the talons in flight. In addition to fish, Bald eagles will take a variety of other birds and mammals, as well as turtles and shellfish. They will also spend time on the ground feasting on a captured prey item or perhaps a scavenged or stolen carcass.

Bald eagles build one of the largest nests of any bird; a nest may be 8 feet across and over 12 feet deep and composed of tree limbs and other smaller vegetative materials. They select large trees where a nest can be constructed high in the canopy. Normally two eggs are laid and one of the parents will remain with the young during the first two weeks after hatching. Both parents hunt and bring food to the nestlings, tearing off bits and feeding them to the young birds. The young fledge and fly at about 3 months of age. Mated pairs may stay together for life.

The Bald and Golden Eagle Protection Act of 1940 officially protected both eagle species by prohibiting killing or trapping of the birds. However, illegal shooting was found to be the leading cause of death in eagles by the U.S. Fish and Wildlife Service in 1978. Besides additional mortality from vehicle collisions, lead poisoning, and power line electrocution, the pesticide DDT also played a large role in population declines. Years of in-depth research finally revealed that DDT ingested by eagles— through eating game birds that had consumed pesticide residues—accumulated in the bodies of eagles, leading to thinner shells in the eggs produced by those eagles, as well as lower fertility. The fragile shells were easily broken and the embryos killed as a result. By the 1950s the lower fertility and reduced nestling survival resulted in an estimated number of Bald eagle nesting pairs at just over 400. The drastic population decline motivated the U.S. Fish and Wildlife Service to declare the Bald eagle endangered in 1967. In 1972 DDT was banned from use in the U.S. and Canada followed suit, banning the pesticide in 1989. Bald eagles recovered year by year and were eventually removed from the endangered species list in 2007. The population in the lower 48 states is estimated at over 300,000 today, with over 71,000 nesting pairs.

The Bald eagle matures at 4-5 years of age and banding records show that longevity may be as long as 38 years in the wild, and even longer in captivity.

The Audubon Society predicts a loss of winter range in the deep south, Texas, Oklahoma, and Texas as global warming proceeds.

James Taulman is a semi-retired research wildlife biologist who worked with the U.S.F.S. research branch and taught zoology, ecology, and more in several university positions. Search for him on Youtube to see wildlife videos.