A Conservation Success Story: DDT, Peregrine Falcons and Our Quest to Save Them

At the first Peregrine Conference in 1965, biologists concluded that the Peregrine Falcon was in serious decline around the world. Concerned enthusiasts in the sport of falconry believed that breeding falcons in captivity would be a way to keep the species alive if the wild birds became extinct. After a second meeting at Cornell University in 1969, the governments of the United States, Canada and Mexico were asked to protect the remaining populations of Peregrine Falcons. The U.S. Department of Interior listed the falcon as endangered in 1970. The falcon remained on the list of endangered species when the Endangered Species Act was adopted by Congress in 1973.

In the mid-1900s, DDT was sprayed on agricultural fields, marshes, and other landscapes as a means to control insect infestations. When small birds ate insects contaminated by this pesticide, some of this chemical remained in their bodies. The more contaminated insects they ate, the more they themselves became contaminated. When Peregrine Falcons, in turn, ate these small birds, DDT accumulated in the falcons’ systems as well, but at an even higher rate. This affected the female falcons’ ability to lay healthy eggs. Their eggs lacked calcium, which meant they were thin-shelled and weak. The population was in trouble. The falcons disappeared from the eastern half of the United States and were rapidly declining in the West. In 1972, the U.S. Environmental Protection Agency banned the use of DDT, which made recovery of the species possible.

Ornithology professor Tom Cade founded The Peregrine Fund at Cornell University in 1970 to save the falcons from extinction. The organization pioneered many techniques through the years for successfully breeding the birds in captivity and releasing them into the wild. The Peregrine Fund bred and released more than 4,000 falcons from 1974 to 1997. In 1985, The Peregrine Fund held an international conference on the 20th anniversary of the first Peregrine Conference to celebrate the survival and growing recovery of the falcon population and to assess its global status.

Through captive breeding and release, Peregrine Falcons were restored to their historic range throughout the United States. In 1999, the Peregrine Falcon was removed from the U.S. Endangered Species List at an international celebration at the World Center for Birds of Prey. Today, this recovery remains one of the most successful conservation efforts in history.