The bald eagle (Haliaeetus leucocephalus) is among the most well-known animal in the United States and has served as its national symbol since 1782. The bald eagle is a bird of prey unique to North America, and renowned for its aura of dignity, majesty and authority in the sky. Eagles will often soar to high altitudes before diving to Earth in search of prey. For much of the last half century the bald eagle was in danger of extinction, although in recent years its population has increased in numbers, suggesting a bright future.
The near-loss of a national symbol:
During the U.S. Revolutionary era, bald eagles were prevalent throughout North America, numbering as high as 75,000 nesting pairs. To celebrate its existence, the bald eagle was made part of our Great Seal by the Continental Congress in 1782. The Great Seal is used for diplomatic purposes, including treaties and letters from the President to foreign dignitaries and leaders.
Over the next century and a half, the bald eagle population suffered from habitat degradation and illegal shooting. The greatest threat to its existence came from the widespread use of pesticides after World War II, especially DDT. During this time, DDT was sprayed on crops across the country, and was absorbed by plants that were ultimately eaten by fish. The contaminated fish then infected the bald eagle, inhibiting the bird's ability to develop strong egg shells. The weakened shells would break during incubation, effectively preventing reproduction.
In 1940, the U.S. Congress passed the Bald Eagle Protection Act, making it illegal to kill, possess without a license or sell bald eagles. Still, by the early 1960's there were fewer than 450 bald eagle pairs nesting in the lower 48 states. By 1967, bald eagles were officially declared an endangered species. In response, an alarmed public banned most uses of DDT in the U.S. in 1972.
Over the past quarter century, the bald eagle has managed something of a comeback, assisted by strong legislation and new breeding and reintroduction efforts. Numerous eggs have been removed from wild nests to be incubated, hatched and raised in captivity to increase the birds' survival rate. At 12 weeks old, the eaglets are released into the wild.
By 1995 there were nearly 4,500 adult bald eagle pairs nesting in the lower 48 states. In July 1995, the Fish and Wildlife Service announced that the bald eagle had recovered to a point where it could be upgraded from "endangered" to "threatened."
Despite relatively small numbers, the bald eagle can be found across the United States, including Alaska, Florida, and Maine. Their range will vary, depending on the time of year and breeding patterns, though northern birds will migrate south in the winter. However, the bald eagle will almost always return to nest within 100 miles of where they were raised.
Male bald eagles generally measure between 2-3 feet (60 to 90 cm) from head to tail, weigh 7-10 pounds (3.2 to 4.5 kg), and have a wingspan of around 6 feet (1.8 m). Females are larger, weighing up to 14 pounds (6.4 kg) with a wingspan of 8 feet (2.4 m). People are often disappointed to learn that the bald eagle is not really bald; instead, it earns its name from the distinctive white feathers covering the head and neck. The rest of the body and wings tend to be very dark, although the bird won't fully develop its color until it matures around age five. Bald eagles often live thirty years in the wild, and even longer in captivity.
The bald eagle feeds primarily on fish plucked out of the water, sometimes submerging completely to catch its prey. However, bald eagles will also prey on just about anything else they can catch, including ducks, rodents, and snakes. They have keen eyesight and find their prey while circling high above the unknowing victim. The bald eagle will then swoop down at very high speeds to attack and kill with its strong talons and beak. In some cases, the bald eagle will let other animals do the dirty work for them. For example, it is famous for stealing the food of ospreys by attacking the bird and forcing it to drop its prey.
Bald eagles will mate for life and normally lay 2-3 eggs one time per year. Sometimes both parents share responsibilities, though often just the female will incubate the eggs, which hatch after about 35 days. Baby eagles will stay in the nest for 3 months or so, after which they are capable of some flight. In order to encourage young to leave the nest, parents will often discontinue feeding or lure the them away with fish. Often eaglets will not make it past their first year of life, due to disease, lack of food, bad weather, or human interference.
The eagle nest is itself quite extraordinary because of its enormous size--in some cases stretching 10 feet wide (3 m) and weighing as much as 2,000 pounds (about 900 kg). Nests are often re-used by the same pair of birds year after year, growing larger as additional material is added. Most nests are built in the tops of large trees near rivers, lakes, and other wetland areas for easy access to food.
Note: Some information has been excerpted from the U.S. Fish and Wildlife Service (USFWS) with permission.