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Bald Eagles Soaring High
Courtesy of U.S. Fish and Wildlife Service
The bald eagle, our national bird, has had a difficult history. They were adopted as one of our nation’s symbol for their strength, grace, and courage. Anyone who has ever seen the bald eagle soaring above would agree that they look amazingly strong and graceful as they float high in the sky. Nevertheless, the strength of bald eagles has been threatened in the past.
Bald Eagles have always been found throughout the forests of the North America, anywhere near water—rivers, lakes, marshes, reservoirs, or oceans—due to their preference for palatable fish. However, humans have been directly responsible for the decline in eagle numbers through habitat loss and toxins introduced to their environment. Bald eagles need tall pine trees to build their nests, and human logging efforts and land development have destroyed many of these very trees.
In the 1950s and 60s, eagle numbers continued to decline due to the large-scale use of the pesticide DDT. DDT was sprayed on huge expanses of crops and land to fight insects. When storms came, the DDT ran off the land into bodies of water, like the ones that eagles prefer to live nearby. The DDT in the water is incorporated with water nutrients into the phytoplankton in the water—photosynthetic one-celled algae. The phytoplankton (and the DDT they have taken up) were then eaten by zooplankton, zooplankton by small fish, and this process continued until it reached the top of the food chain, the bald eagles. The problem is, as the DDT moved up the food chain, its concentration becomes higher and higher, because the animals must eat more and more food to sustain their larger bodies, a phenomenon known as biomagnification. The DDT that humans used to keep insects away from our food had made it into the eagles’. Unfortunately, it had very negative consequences, causing reproductive problems including eggs with too-thin shells.
However, beginning in 1976, Signals of Spring collaborator Peter Nye and his team from the New York State Department of Environmental Conservation began a ‘hacking’ program. Peter’s crew brought healthy young eaglets from Alaska, where there were still healthy populations, to New York. Since then, eagle numbers have steadily been increasing, and scientists have high hopes for the future. According to the U.S. Fish and Wildlife Service, eagle numbers in the lower 48 states have risen from 417 nesting pairs in 1963 to 4500 nesting pairs in 1995—an amazing increase. This success story has been attributed to the Endangered Species Act of 1973, the banning of DDT, and programs such as Peter Nye’s aimed directly at protecting bald eagles. In 1995, the bald eagle was taken off the Endangered Species list and is now listed as Threatened. In New York, Peter's work has been instrumental in improving the plight of our national bird!
Findings from scientists like Peter Nye allowed the government to make the decision to ‘de-list’ the eagles. Like Signals of Spring students, Peter uses satellite tracking to study the movements and migrations of the eagles and to find out what habitats they prefer for nesting, resting, and feeding.
If you would like to see bald eagles up close, join us on next year’s bald eagle cruise up the Connecticut River!