Why Were American Bald Eagles Endangered?
The American bald eagle was placed on the Environmental Protection Agency's endangered species list in 1967. Since then, the only eagle native to the United States has become a symbol for the environmental movement as much as for its representation of American values and ideals. Intense conservation efforts successfully increased populations from the threat of extinction and, in 2007, the bald eagle was officially removed from the endangered species list.
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Taxonomy, Range and Habitat
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The bald eagle's scientific name (Haliaeetus leucocephalus) means sea (halo) eagle (aeetos) with a white (leukos) head. The white head that makes this species so noticeable does not become noticeable until the fourth or fifth year of development. Bald eagles are found throughout North America with the greatest populations being located in the Northwest because of large the populations of salmon in the area, one of their primary food sources. Bald eagles nest high in old-growth trees near large bodies of water.
History of Population Decline
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The bald eagle was once a common sight across the United States. The birds have faced a number of threats through the years, however. Populations of eagles were initially influenced by the destruction of their forest habitat as the population in the United States was increasing. Bald eagles were often shot as they were (and still are at times) mistaken for a hawks because of the juveniles not having a white head. They were also persecuted by many farmers who feared that they were a threat to their livestock, both on land and at sea. Most harmful to eagle population---as well as many other birds---was the prolific use of a chemical called DDT in the mid-20th century.
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DDT
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DDT is an acronym for the chemical pesticide dichloro-diphenyl-trichloro-ethane. Use of the chemical increased dramatically after World War II as it was endorsed and promoted as being a miracle chemical by the federal government as well as the chemical industry. DDT was especially harmful to eagles as the chemical would accumulate through the food web in a process known as biomagnification. The result was low levels of the chemical in the environment but high levels of DDT in eagles at the top of the food chain. DDT would affect the thickness of the eagles' eggs, making them so thin that they would often break when the nesting parent would sit on them to keep them warm. Eagle populations have slowly rebounded in response to a nationwide ban on DDT in the United States in 1972.
Conservation Efforts
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In 1940, Congress passed the Bald Eagle Act, which gave special protection to the birds and their habitat. Legislation helped alleviate some of the direct human pressures, but at the same time DDT use was becoming more widespread in its use. In 1967, the bald eagle was given special protection by the federal government under a precursor to the Endangered Species Act. The bald eagle was one of the first species added and protected under the Endangered Species Act when it was enacted in 1973. Slowly, under federal protection and aided by a landmark decision by the Environmental Protection Agency to ban DDT in 1972, the population of breeding pairs increased in the wild. In 1995, bald eagles were changed from the status of endangered to threatened before being removed from the endangered species list completely in 2007.
Current Populations
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As of 2010, populations of bald eagles in the wild are strong and healthy. Bald eagles pair with another eagle for life, and populations of the bird were only around 500 breeding pairs in the 1960s, according to the U.S: Fish and Wildlife Service. Currently, there are now around 10,000 pairs of bald eagles mating in the wild thanks to federal protection and conservation efforts.
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References
- U.S. Fish and Wildlife Service: Bald Eagle Delisting
- U.S. Fish and Wildlife Service: Chart and Table of Bald Eagle Breeding Pairs in Lower 48 States
- North Dakota State University: The Ban of DDT and the Subsequent Recovery of Reproduction in Bald Eagles
- Northern State University: Bald Eagle
- California State University Stanislaus: Endangered Species Recovery Program - Bald Eagle
Resources
- Photo Credit eagles image by Mat Hayward from Fotolia.com
