Recovery of the Peregrine Bird Population from DDT Poisoning

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The Peregrine is the world's fastest bird; it can reach over 200 miles as it dives from tall cliffs onto smaller birds (1). It circles high searching for prey and when a smaller bird like a pigeon takes off it plummets to the earth and kills it with razor sharp talons. The Peregrine's identifying characteristics include its large size, long pointed wings and dark mustache set against white cheeks (11). The female has a wingspan of about 4 feet and often weights more than two pounds as compared to the smaller males the generally only weight in at one pound (11). It was found from the subarctic boreal forests of Alaska and Canada all the way south to Mexico (1). It was called 'the worlds most successful flying bird' largely as a result of its unsurpassed flight characteristics and unusually stable, near-global population. Peregrines could once be found on every continent except Antarctica (2). Besides man the Peregrines only natural predator is the great horned owl which often raids the Peregrines nest (11). The peregrine has recovered remarkably well. It is now found throughout North America and is breeding in the wild. There are 1,593 breeding pairs of Peregrines in North America, up from 324 in 1975 and well past the initial repopulation goal of 631 pairs (3). Their repopulation was aided by their integration into manmade environments. Peregrines have adapted remarkably well to the city environment. Often they make nests on the ledges of sky scrappers where they are able to dive down onto the unsuspecting pigeons that cloud the city air. They will return to the same ledge year after year. Over 50 pairs of Peregrines winter in L.A. (4). DDT was a very effective and stable pesticide that was sprayed over large sections of swampland in order to combat mosquito populations. Because of its stability it was concentrated as it moved up the food chain. It kills mosquitoes and other small insects that are then eaten by fish which in turn are eaten by birds of prey. When DDT is introduced into the environment it produces DDE, which accumulates in eggshells causing them to break in the nest (2). The Environmental Protection Agency banned the pesticide in 1972. One of the major driving forces behind the banning of DDT was the book "Silent Spring" by Rachel Carson, who was a former U.

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