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The Midwest Region includes Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio and Wisconsin. Find a location near you »

 

Conserving the Nature of America

The mission of the U.S. Fish and Wildlife Service is working with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people.

 

Fact Sheet

Natural History, Ecology and Recovery

 

Adult bald eagle perched in a tree above its nest.

Photo courtesy of Ryan Anthony; USFWS

 

A North American species with a historic range from Alaska and Canada to northern Mexico, the bald eagle is an Endangered Species Act success story.

 

Forty years ago, our national symbol was in danger of extinction throughout most of its range. Habitat destruction and degradation, illegal shooting, and the contamination of its food source, largely as a consequence of DDT, decimated the eagle population. Habitat protection afforded by the Endangered Species Act, the federal government’s banning of DDT, and conservation actions taken by the American public have helped bald eagles make a remarkable recovery.

 

Bald Eagle Biology

Bald eagles are a North American species that historically occurred throughout the contiguous United States and Alaska. The largest North American breeding populations are in Alaska and Canada, but there are also significant bald eagle populations in the Great Lakes states, Florida, the Pacific Northwest, the Greater Yellowstone area, and the Chesapeake Bay region.

 

Adult bald eagles have the dark brown body and distinctive white head and tail.  In contrast, juvenile bald eagles have mottled brown and white plumage.  They gradually acquire the adult plumage as they mature, which takes about five years. Most bald eagles can breed at 4 or 5 years of age, but many do not start breeding until much older.  Bald eagles may live 15- 30 years in the wild. The oldest known bald eagle in the wild was at least 38 years old. It was hit and killed by a car in New York in 2015. It had been banded in New York state in 1977.

 

Adult bald eagles are powerful, brown birds that may weigh 14 pounds and have a wingspan of 8 feet. Male eagles are smaller, weighing as much as 10 pounds and have a wingspan of 6 feet. Sometimes confused with golden eagles, bald eagles are mostly dark brown until they are four to five years old and acquire their characteristic coloring. There is a distinction between the two species, though, even during the early years. Only the tops of the bald eagle’s legs have feathers. The legs of golden eagles are feathered all the way down. Learn more about bald and golden eagle identification here.

 

Bald eagles are opportunistic feeders with fish comprising much of their diet.  They also eat waterfowl, shorebirds, colonial waterbirds, small mammals, turtles, and carrion (often along roads or at landfills). Because they are visual hunters, eagles typically locate their prey from a conspicuous perch, or soaring flight, then swoop down and strike.

 

Bald eagles require a good food base, perching areas, and nesting sites. Their habitat includes estuaries, large lakes, reservoirs, rivers, and some seacoasts. In winter, the birds congregate near open water in tall trees for spotting prey and night roosts for sheltering.

 

Eagles usually mate for life, choosing the tops of large trees to build nests, which they typically use and enlarge each year. Bald eagles may also have one or more alternate nests within their breeding territory. In treeless regions, they may also nest in cliffs or on the ground. The birds travel great distances but usually return to breeding grounds within 100 miles of the place where they were raised.

 

Bald eagles generally nest near coastlines, rivers, and large lakes where there is an adequate food supply. They nest in mature or old-growth trees, snags (dead trees), cliffs, and rock promontories.  Recently, and with increasing frequency, bald eagles are nesting on artificial structures such as power poles and communication towers, and away from large water bodies.  In forested areas, bald eagles often select the tallest trees with limbs strong enough to support a nest that can weigh 1,000 pounds or more. Nest sites typically include at least one perch with a clear view of the water, where they forage. Eagle nests are constructed with large sticks, and may be lined with moss, grass, plant stalks, lichens, seaweed, or sod.

 

Bald eagle nests are generally 4-5 feet wide and 2-4 feet deep, although the nesting pair will add nesting material to the nest every year. Some eagle nests stay small, but some can reach 10 feet across and weigh a thousand pounds! The largest recorded bald eagle nest, located in St. Petersburg, Florida, was 9.5 feet in diameter, 20 feet deep and weighed almost 6,000 pounds. Nests may grow so large that they make a tree top heavy, and will cause the nest or tree to fall over in storms.  


Breeding bald eagles typically lay one to three eggs once a year, and they hatch after about 35 days. The young eagles are flying within three months, but they will continue to use their nest as a "home base" where their parents continue to care for them for an additional 4-6 weeks. Learn more with the Nesting Calculator. Young eagles can have high rates of mortality due to disease, lack of food, bad weather, or dangers associated with humans (collision with cars or power lines). Mortality rates their first year can be as high as 50%. After they are a year old, their survival rates are much higher.

 

The Plight of the Bald Eagle

When America adopted the bald eagle as the national symbol in 1782, the country may have had as many as 100,000 nesting eagles. The first major decline of the species probably began in the mid to late 1800’s, coinciding with the decline of waterfowl, shorebirds, and other prey.

 

Although they primarily eat fish and carrion, bald eagles used to be considered marauders that preyed on chickens, lambs, and domestic livestock. Consequently, the large raptors were shot in an effort to eliminate a perceived threat. Coupled with the loss of nesting habitat, bald eagle populations declined.

 

In 1940, noting that the species was “threatened with extinction,” Congress passed the Bald Eagle Protection Act, which prohibited killing, selling, or possessing the species. A 1962 amendment added the golden eagle, and the law became the Bald and Golden Eagle Protection Act.

 

Shortly after World War II, DDT was hailed as a new pesticide to control mosquitoes and other insects. However, DDT and its residues washed into nearby waterways, where aquatic plants and fish absorbed it. Bald eagles, in turn, were poisoned with DDT when they ate the contaminated fish. The chemical interfered with the ability of the birds to produce strong eggshells. As a result, their eggs had shells so thin that they often broke during incubation or otherwise failed to hatch. DDT also affected other species such as peregrine falcons and brown pelicans.

 

In addition to the adverse effects of DDT, some bald eagles have died from lead poisoning after feeding on waterfowl containing lead shot, either as a result of hunting or from inadvertent ingestion.

 

By 1963, with only 487 nesting pairs of bald eagles remaining, the species was in danger of extinction. Loss of habitat, shooting, and DDT poisoning contributed to the near demise of our national symbol.

 

The Road Back

As the dangers of DDT became known, in large part due to the 1962 publication of Rachel Carson’s book Silent Spring, the Environmental Protection Agency took the historic and, at the time, controversial step of banning the use of DDT in the United States. That was in 1972, and it was the first step on the road to recovery for the bald eagle.

 

In 1967, the Secretary of Interior listed bald eagles south of the 40th parallel under the Endangered Species Preservation Act of 1966. Following enactment of the Endangered Species Act of 1973, the Service listed the species in 1978 as endangered throughout the lower 48 states, except in Michigan, Minnesota, Oregon, Washington, and Wisconsin where it was designated as threatened.

 

“Endangered” means a species is considered in danger of extinction throughout all or a significant portion of its range. “Threatened” means a species is considered likely to become endangered within the foreseeable future, but is not currently in danger of extinction.

 

The species was not listed as threatened or endangered in Hawaii because it does not occur there, or in Alaska because populations there have remained robust.


Listing the species as endangered provided the springboard for the Service and its partners to accelerate the pace of recovery through captive breeding programs, reintroduction efforts, law enforcement, and nest site protection during the breeding season.

 

In July 1995, the Service announced that bald eagles in the lower 48 states had recovered to the point where those populations previously considered endangered were now considered threatened.

 

In July 1999, the Service proposed to remove the bald eagle from the list of threatened and endangered species. Since then, the Service has reviewed comments received on that proposal along with new data and information to determine the best ways to manage the species once it is removed from the protections of the Endangered Species Act. In 2006, the Service re-opened the public comment period due to new information on the proposal to delist. Data gathered during this comment period was factored into a final decision on the status of the species.

 

In 2006, the Service estimated that there are at least 9,789 nesting pairs of bald eagles in the contiguous United States. Bald eagles have staged a remarkable population rebound and have recovered to the point that they no longer need the protection of the Endangered Species Act. Up-to-date information on eagle population numbers can be found here. (updates on-going)

 

Thus, on June 28, 2007, the Service announced the recovery of our nation’s symbol and removal from the list of threatened and endangered species.

 

A detailed narrative of the bald eagle's recovery can be found here.

 

 

What Lies Ahead

Although the Service removed the bald eagle from the list of threatened and endangered species under the Endangered Species Act, it will still be protected by the Migratory Bird Treaty Act and the Bald and Golden Eagle Protection Act. Both laws prohibit killing, selling or otherwise harming eagles, their nests, or eggs.

 

The Service has continued to work with state wildlife agencies to monitor the status of bald eagles for five years after delisting, as required by the Endangered Species Act. If the species should need the protection of the Act, the Service can relist it as endangered or threatened. In the meantime, individual states may also pass or implement laws to protect bald eagles.

 

As part of the 2016 Eagle Rule Revisions, the Service committed to a long-term monitoring plan of bald and golden eagles in order to determine appropriate thresholds for permit issuance. Assuming sufficient appropriated funding, the Service plans to conduct eagle surveys on a 6-year rotation: One set of paired summer–winter golden eagle surveys in the first and second and fourth and fifth years of each assessment period, and to conduct bald eagle surveys in years three and six.

 

Fact Sheet Revised July 2019

 


Eagle Natural History

 

Midwest Eagle