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EAGLE NUMBERS MAY BE AT ALL TIME HIGH
The
U. S. Fish and Wildlife Service recently announced results showing the
largest population of breeding bald eagles in the U.S. since World War
II. Bald eagles in the lower 48 states have climbed from an all-time low
of 417 nesting pairs in 1963 to an estimated new high of 9,789 breeding
pairs today.
This updated estimate is based on information gathered by the States
in 2004 or later. Minnesota tops the list with 1,312 pairs of eagles,
followed by Florida with 1,133 pairs and Wisconsin's 1,065 pairs. There
are also eagles now breeding in the District of Columbia and the state of
Vermont, which was the only state in the contiguous U.S. which lacked
eagles until the first eaglets hatched successfully in 2006.
The bald eagle, which is protected as a threatened species under the
Endangered Species Act, once sounded an environmental alarm for the
American public when it was learned the widespread use of the pesticide
DDT had the national symbol plummeting towards extinction.
For years after World War II, DDT (dichloro-diphenyl-trichloroethane)
was used to control mosquitoes and agricultural pests. When it rained, DDT
would wash off the soil and into the waterways. There, it was absorbed by
aquatic plants and animals. Fish ate the plants and animals, and eagles
ate the fish.
When ingested, the chemical compound would build up in the fatty
tissues of female eagles and prevent the formulation of calcium necessary
to produce strong eggshells. Consequently, eggshells thinned and cracked
when an adult tried to incubate them. Widespread reproductive failure and
a precipitous decline in numbers followed.
Rachel Carson, a biologist and writer for the U.S. Fish and Wildlife
Service, became aware of the dangers of chemical pesticides including DDT,
but was also aware of the controversy within the agricultural community
which needed such pesticides to support crop production. Carson made the
decision to produce her book Silent Spring after years of research across
the United States and Europe.
When Silent Spring was published in 1962, Carson immediately became
the focus of a storm of controversy. But as a result of her research and
the publication of Silent Spring, the government eventually banned the use
of DDT in 1972.
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