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Peregrine Falcon Falco peregrinus anatum (Endangered Colorado, Federally) Falco peregrinus tundrius (Threatened Colorado, Federally) A medium-sized hawk that formerly nested in many parts of the world, including North America, the peregrine falcon is now absent from most of the eastern United States, and its population level is greatly reduced in many other areas. Characterized by a nearly black helmet, a dark slate- blue coloration on the back and a buff coloration broken by horizontal bars on the underparts, the peregrine varies in length from 15-22 inches. Like all falcons, it has long, pointed wings and quick, steady wing beats in flight. The principal prey of the peregrines are small- to medium-sized birds such as swallows, blackbirds, robins, doves, pigeons, and shorebirds. Although this species is regarded as a fearless hunter, it's interesting to note that the peregrine doesn't defend itself against attacks from other birds, and that some birds will lie in wait and steal its food. Peregrines prefer to nest on high, precipitous cliffs and river gorges such as those found in the Rocky Mountains. Although they've never been abundant, their numbers are now critically low. The major causes of population decline have been the injurious effects of the pesticide DDT and the loss of important nesting and feeding areas due to human encroachment. Of the two, DDT has been the primary culprit. The problem with DDT is that it accumulates in adult peregrines when they eat contaminated prey. Eventually it causes thinning of the shells of peregrine eggs, and the eggs break before they hatch. Fortunately, DDT has been banned in the United States, but some peregrines that nest here are probably still exposed to this pesticide when they or their prey migrate to Latin America. There are two subspecies of peregrine falcons - the American and the Arctic. Attic peregrines migrate through Colorado. The American breeds and nests here, and efforts are now underway to reintroduce American peregrines raised in captivity into areas where they have disappeared. Some additional relief to the peregrine's plight in Colorado can be provided by keeping the remaining nest sites free from human intrusions during the nesting season and by ensuring that development provides for habitat that supports the peregrine's prey species. Hundreds of peregrines have been released into Colorado's wilds since 1976, and more peregrines are breeding in Colorado today than at any time since the 1950s. Left: A captive male American peregrine falcon used for breeding purposes. 1 7