Threats to the Bald Eagle
Bald Eagles Fall to Pesticides, Poisons, Hunters, and Other Dangers
Bald Eagles have gone from plentiful through threatened, endangered, nearly extinct, recovering and now thriving once again.
We nearly lost the Bald Eagle, Haliaeetus leucocephalus, but today the species is living proof that people can prevent extinctions by changing the behaviors that cause species populations to plummet. In 2007, after forty years on the endangered species list, the Bald Eagle was delisted.
Threats to Bald Eagles
Many things contributed to the decline of Haliaeetus leucocephalus, and still threaten the species to some degree:
- Bald Eagles were once believed to be dangerous predators that commonly took lambs and occasionally even attacked human babies—folklore with very little basis in fact. Because of this, people deliberately shot and poisoned Bald Eagles. Even after the species was legally protected, some ranchers continued to put out poisoned bait and hunt the birds from planes.
- The organochlorine pesticide DDT and related compounds cause Bald Eagles and other birds to lay thin shelled eggs, which often break before they hatch. DDT was banned in North America in 1972.
- Other poisons and contaminants in the environment, such as mercury, lead, pesticides, and toxic waste poison the birds, which ingest the substances second-hand in prey.
- Gradual and continuing clearing of forest and plowing of prairie, as well as acid rain, decrease eagle nesting sites and hunting range, and cause decreases in the populations of prey species.
- Structures built by humans, such as power lines and windmills, cause many bird injuries and deaths.
- Misguided individuals who harass the birds, steal their eggs, and kill them for their feathers, interfere with nesting and threaten local populations.
Today, the major human threat to Bald Eagles is the power line, accounting for two thirds of accidental deaths. While deliberate harassment and killing of the birds is now relatively rare, accidental shooting, trapping, and poisoning still take their toll.
Conservation Measures for Bald Eagles
Two things have had a very significant impact on the recovery of Haliaeetus leucocephalus: the banning of the pesticide DDT, and laws that made it illegal to shoot, trap or even disturb a Bald Eagle. Protection of suitable habitat has also supported their return. In areas where the birds were completely wiped out, the release of captive reared birds has had some success. Other conservation efforts include:
- public education about the habits and needs of Bald Eagles.
- protection of specific nests from human disturbance.
- artificial nest sites to attract breeding pairs.
- rehabilitation of injured birds.
- establishment of sanctuaries.
The Bald Eagle, whose US population ( lower 48 states) was estimated at less than 500 breeding pairs in the early 1960s is still legally protected, but is no longer considered endangered.
Sources:
"Bald Eagle Population Size." U.S. Fish and Wildlife Service: Ecological Services
“Bird Fact Sheets: Bald Eagle.” Canadian Wildlife Service and Canadian Wildlife Federation Hinterland Who’s Who.
“Unfair Game.” Drabelle, Dennis. Audubon: Jan-Feb 2008; Pg 84-86.
