Monitoring Contaminants in Alaskan Peregrines

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Arctic and American peregrine falcons (Falco peregrinus tundrius and F. p. anatum, respectively) were listed as endangered in 1970. At the time, some local populations of American peregrine falcons in the eastern United States had disappeared, and populations in western and northern North America had been reduced by 80 percent or more. Organochlorine pesticides such as DDT and its breakdown product DDE were identified as the main cause of the decline. The peregrines accumulated these chemicals in their tissues by feeding on birds that had eaten DDT-contaminated insects or seeds. These chemicals prevented normal calcium deposition during eggshell formation, and caused females to lay thin-shelled eggs …