Peregrine falcons have suffered due to their dangerous position atop the food chain. Pesticides accumulate in small (not lethal) quantities in the tissues of small birds and mammals, but become concentrated enough in predatory birds, such as falcons, to kill them or render them incapable of producing offspring. Organochlorine pesticides (DDT and dieldrin) have been proven to reduce the birds' ability to produce eggshells with sufficient calcium content, making the egg shells thin and more likely to break. Peregrine falcon populations dropped precipitously in the middle of the 20th century. All breeding pairs vanished in the eastern United States. A successful captive breeding and reintroduction program, combined with restrictions in pesticide use, has been the basis of an amazing recovery by peregrine falcons. Now the use of many of the chemicals most harmful to these birds is restricted. However, it is not yet restricted in Central and South American where many subspecies spend the winter. After having been on the endangered species list since 1969, the incredible recovery of peregrine falcons has become a perfect example of how effective human conservation can be. In the 1990s they were taken off the federal list of endangered species in the United States. They are still listed as endangered in the state of Michigan.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: appendix i
IUCN Red List of Threatened Species: least concern