The peregrine falcon is among the world’s fastest birds, flying at up to 55 mph and diving at more than 200 mph when striking avian prey in mid-air. Peregine populations began to decline rapidly in the late 1940s because of pesticide contamination. One of three North American subspecies, the peregrine found in Greater Yellowstone (Falco peregrinus anatum) was considered extirpated by the 1960s. As part of a national reintroduction program, peregrines were released in Bighorn Canyon, Grand Teton, and Yellowstone national parks during the 1980s. They typically reside in Greater Yellowstone from March through October, when their favored prey—songbirds and waterfowl—is most abundant. During winter they may migrate as far south as Mexico.