Some were from wild stock, but many came from falconers from throughout the United States and Canada. Today, The Peregrine Fund estimates it has released some 4,000 birds. One possible side effect of captive breeding programs has been the appearance of peregrines in more heavily populated areas, where they have been nesting in tall buildings, church towers and power plant smokestacks. Their incursions into the human sphere have made them very popular. Bird watchers line up in metropolitan areas like Toronto and New York City to view peregrines that are nesting in skyscrapers.
Peregrines are one of the success stories of the environmental movement.
The birds, once near extinction, were removed from the Endangered Species List on Aug. 25, 1999. Scientists like Cade, however, warn that the birds will have to be carefully monitored. They winter in South America, where DDT is still in use. Peregrines still have DDT in their systems and eggshells are still thinner than they should be. In addition, the birds are still scarce in some traditional nesting areas, including the Northeastern U.S. and the northern Great Plains.