Raptors have been greatly affected by human activity. Certain birds of prey have become threatened or endangered as the result of hunting, pollution, and habitat destruction. As many as 18 raptor species have been labeled as endangered or threatened in the United States. However, efforts to restrict hunting, create and protect preserves and wildlife refuges, decreased pollution, and captive breeding and rehabilitation efforts have helped some raptor populations to survive and regain their numbers. In the 1940s, heavy use of the pesticide DDT caused a drastic decline in bald eagle populations. By 1974, it was estimated that only 700 breeding pairs of bald eagle remained. After DDT was banned, numbers of bald eagles rose. Similarly, when the use of another potent pesticide was banned, numbers rose. During the same period, legislation was passed that prohibited poaching of bald eagles and disturbance of their nests. As a result, there are believed to be more than four thousand breeding pairs of bald eagles in the lower 48 states alone. However, given this success, several species, such as the California condor, remain endangered. One such example is. At one period, there were thousands of California condors. By 1939, however, the number of condors fell to less than 100. By 1982, fewer than 25 remained in the wild. Their decline was attributed to habitat loss, organic pesticide poisoning, and electrocution on high voltage wires. Due to their slow reproductive rate, these problems were compounded. Conservationists feared the extinction of the species and organized a huge effort to breed more California condors before they were lost. Because of captive breeding programs, over 100 California condors live, and some have been released back into the wild where it is hoped they will survive to reproduce on their own.
Arnold, Caroline. On the Brink of Extinction: The California Condor. San Diego: Harcourt Brace Jovanovich Publishers, 1993.
Brooke, Michael, and Tim Birkhead, eds. The Cambridge Encyclopedia of Ornithology. Cambridge: Cambridge University Press, 1992.
Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.