The bald eagle, Haliaeetus leucocephalus, is a large fish-eating raptor of North America, the national bird of the United States, and the standard example of a species brought back from the edge by banning a single chemical. It fell to roughly 417 nesting pairs in the contiguous states and now numbers in the hundreds of thousands.

An adult bald eagle. The white head and tail that give the bird its name appear only at four to five years old.
An adult bald eagle. The white head and tail that give the bird its name appear only at four to five years old.Credit: Saffron Blaze (CC BY-SA 3.0).

It is a sea eagle, in the genus Haliaeetus with the white-tailed eagle of Eurasia and the Steller's sea eagle, rather than a true eagle of the genus Aquila. Adults reach a wingspan of about two metres, with females roughly a quarter larger than males, as in most raptors.

It is not bald. The name comes from an older sense of balde meaning white, describing the head rather than an absence of feathers.

The range of the bald eagle, which covers most of North America and concentrates around coasts, large lakes and rivers.
The range of the bald eagle, which covers most of North America and concentrates around coasts, large lakes and rivers.Credit: Mad Max (CC BY-SA 3.0).

Bald eagles occur across Canada, the United States and northern Mexico, always associated with water. Alaska and British Columbia hold very high densities, and the largest concentrations gather at salmon runs.

The diet is mainly fish, taken from at or near the surface with the feet rather than by diving. Beyond that, the bird is an opportunist: waterfowl, small mammals, and a great deal of carrion, including winter-killed deer and, at coastal sites, marine mammal carcasses.

It also steals. Bald eagles routinely harass ospreys and other birds into dropping their catch, which is kleptoparasitism and is a substantial part of how some individuals feed.

That habit is behind a well-known anecdote. Benjamin Franklin wrote in a private letter in 1784 that the bald eagle was a bird of bad moral character, that it did not get its living honestly, and made a favourable comparison to the turkey. The frequently repeated claim that he formally proposed the turkey as the national bird is not supported: the letter was private, it was written after the Great Seal was adopted, and it reads as a joke at the expense of a badly drawn eagle on a society's emblem.

A bald eagle in immature plumage. Young birds are mottled dark brown and are commonly mistaken for golden eagles until they acquire adult markings.
A bald eagle in immature plumage. Young birds are mottled dark brown and are commonly mistaken for golden eagles until they acquire adult markings.Credit: Nirajha (CC BY-SA 4.0).

Nests are the largest built by any North American bird and are added to year after year. The record, at St Petersburg, Florida, was about 2.9 metres across and 6 metres deep and was estimated to weigh close to two tonnes.

DDT. The insecticide itself was not acutely toxic to eagles; its persistent breakdown product disrupted calcium deposition, so eggshells thinned and broke under the incubating parent.
DDT. The insecticide itself was not acutely toxic to eagles; its persistent breakdown product disrupted calcium deposition, so eggshells thinned and broke under the incubating parent.Credit: Ben Mills (Public domain).

Bald eagles were shot, trapped and poisoned throughout the nineteenth and early twentieth centuries, treated as competition by fishermen and as vermin generally, with an Alaskan bounty running from 1917 to 1953. The Bald and Golden Eagle Protection Act of 1940 stopped the legal killing.

The collapse that followed was chemical. DDT, used widely from the 1940s, breaks down to DDE, which accumulates up food chains and concentrates heavily in fish-eating birds. DDE interferes with calcium transport in the shell gland, so eggs were laid with shells too thin to bear the weight of an incubating adult and broke in the nest. Reproduction failed across whole regions while the adults appeared healthy, which is why the cause took time to identify.

Rachel Carson's Silent Spring in 1962 brought it to public attention. The contiguous United States held about 417 known nesting pairs by 1963. DDT was banned for agricultural use in the United States in 1972, the eagle was listed under the Endangered Species Act in 1978, and recovery followed within a few decades: delisted in 2007, and a 2021 assessment put the lower-48 population above 300,000 individuals including around 71,400 nesting pairs.

The recovery is genuine and it is also specific. It worked because the cause was a single identifiable compound with a legislative fix, the bird was long-lived enough to persist while shells recovered, and habitat was still available. Most declines do not have that shape.

Lead is now the significant chemical threat. Eagles feed on carcasses and gut piles left by hunters, which contain fragments of lead ammunition, and a 2022 continent-wide study found evidence of chronic lead exposure in roughly half the eagles sampled and acute poisoning in a substantial minority. Modelling in the same work suggested it is suppressing population growth measurably. Non-lead ammunition solves it and adoption is partial.

Highly pathogenic avian influenza reached North American raptors in 2022 and killed bald eagles directly and through infected prey, causing nest failures in some regions. Collisions with vehicles and power lines, and disturbance at nest sites, account for the rest.

A golden eagle. It is a true eagle of a different genus, is widespread across the northern hemisphere, and is routinely confused with immature bald eagles in North America.
A golden eagle. It is a true eagle of a different genus, is widespread across the northern hemisphere, and is routinely confused with immature bald eagles in North America.Credit: Giles Laurent (CC BY-SA 4.0).

The bald eagle was placed on the Great Seal of the United States in 1782 and has appeared on currency, passports, military insignia and the presidential seal ever since.

A United States passport. The eagle has been on federal insignia since 1782, which is part of why almost nobody noticed it had no legal status as the national bird.
A United States passport. The eagle has been on federal insignia since 1782, which is part of why almost nobody noticed it had no legal status as the national bird.Credit: United States Department of State (Public domain).

Here is the detail: it was not the official national bird until December 2024. For 242 years it was the national emblem by convention and by its use on the Great Seal, and no statute had ever designated it. A bill correcting that was signed in December 2024, which is why an animal universally described as the national bird of the United States became so only very recently.

The Native American relationship with the bird is older and legally distinct. Eagle feathers are central to ceremonial practice for many nations, and because possession is otherwise prohibited, the National Eagle Repository distributes feathers and parts from birds found dead to enrolled members of federally recognised tribes.

The bald eagle is the case most often cited to show that environmental regulation works, and it does show that. It is worth being precise about what it shows: that a persistent, bioaccumulating chemical can devastate a species without killing a single adult visibly, that the damage can be invisible for years because the failure is in the eggs, and that removing the cause can reverse it if the animal lives long enough to wait.