Escaping Extinction

The recovery of the peregrine falcon from near extinction is one of the great conservation stories of the 20th century. Before 1940, there were about 7000 peregrines in North America, most of these in the Arctic. But by the 1970s, there were only a few hundred birds left in North America, and the peregrine was placed on the Endangered Species list. Peregrines in the rest of the world were also vanishing.

Their drastic decline was a consequence of exposure to DDT, a pesticide used widely after its synthesis in 1945. Insects exposed to DDT were eaten by small birds, which were then caught by peregrines. DDT is fat-soluble, which means that it is stored in the bodies of organisms, in their fat. Consequently, the amount of DDT present in peregrine falcons built up to high levels. These levels killed some adult birds, but more often it caused females to lay eggs with shells too thin to resist breakage during incubation.

In the early 1970s, DDT was banned in North America, and by 1977 breeding programs were reintroducing captive-bred peregrines to the wild. Through these efforts, peregrines have made a recovery and by 1990 there were about 1200 breeding pairs. The Arctic population, in particular, is increasing steadily.

Although the peregrine has been downlisted from endangered to vulnerable, it is still at risk. DDT is still used heavily in Central and South America, and the small birds that spend their winters there accumulate it in their tissues. When northern peregrines prey on these birds, they are once again ingesting DDT, causing them to lay eggs that often do not survive. The peregrine has escaped death once, but it is not yet safe.

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