Peregrine Falcon | Research & Encyclopedia Articles

The peregrine falcon (Falco peregrinus), a bird of prey in the family Falconidae, is one of the most wide-ranging birds in the world with populations in both the Eastern and Western Hemispheres. However, with extensive pesticide use, particularly DDT, beginning in the 1940s, many populations of these birds were decimated. In the United States by the 1960s, the peregrine falcon was completely extirpated from the eastern half of the country because DDT and related compounds, which are amplified in the food chain/web,caused the birds' eggshells to become thin and fragile. This led to reproductive failures, as eggs were crushed in the nest during incubation. Prior to the DDT-induced losses, there were about 400 breeding pairs of peregrine falcons in the eastern United States. In the early 1970s there were over 300 active nests in the western states, but within a single decade that number dropped to 200. The numbers continued to decline, and in 1978 there were no breeding pairs of peregrine falcons in the eastern United States. By 1984, due to reintroduction efforts, there were 27 nesting pairs, and in 1985, 38 nesting pairs were present in the east with at least 16 pairs fledging young. Also in 1985, 260 young, captive-raised peregrine falcons were released into the wild, 125 in the eastern states, and 135 in the west. By 1986, 43 pairs were nesting, and 25 of those pairs fledged 53 young. By 1991, over 100 breeding pairs were found in the east, and 400 pairs were found in the west. The increase of peregrine falcons has brought the numbers up to 215 breeding pairs in the mid-west regions.

The recovery success of the peregrine falcon is due largely to the efforts of two groups, the Peregrine Fund based at Cornell University in Ithaca, New York, and the Canadian Wildlife Service at Camp Wainwright in Alberta. Much of their research centered on captive breeding for release in the wild and finding ways to induce the falcons to nest and raise young in their former range. With great patience, and limited early success, the projects paid off.

The restoration projects also yielded much valuable information as well as innovative approaches to reestablishing peregrine falcon populations. For captive breeding, falcons trapped as nestlings stood a much better chance of reproducing in captivity than when trapped as flying immatures or adults. Since habitat destruction and human encroachment limit potential nesting sites—which typically are cliff ledges—researchers found that a potential, and ultimately successful, alternative nest site was the window ledge of tall, city buildings. These locations mimic their natural nest sites, and these "duck hawks," as they were once called, had a readily available prey in their new urban ecosystem. Peregrine falcons immediately began killing rock doves for food, which some saw as a service to the cities, since these "pigeons" tended to be regarded as a "nuisance" species.

Since it began in the 1970s, this captive breeding and release program has become well established, with over 4,000 captive-bred peregrine falcons released over the past three decades. In August of 1999, the peregrine falcon was removed from the Endangered Species list by the U.S. Fish and Wildlife Service.

Ehrlich, P., D. Dobkin, and D. Wheye. Birds in Jeopardy. Stanford, CA: Stanford University Press, 1992.

Ratcliffe, D. A. The Peregrine Falcon. Vermillion, SD: Buteo Books, 1980.

The Peregrine Fund. [cited May 2002]. <http://peregrinefund.org> ;.

The Raptor Center. [cited May 2002]. <http://www.raptor.cvm.umn.edu&# x003E;.

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