This raptor is identified by its long, pointed wings and a long tail. Its shape as well as its size makes it stand out—the long primary feathers give the peregrine a long-winged shape. As with most raptors, males are smaller than females, so peregrines can overlap with large female merlins or small male gyrfalcons. Adults are blue-gray above with barred underparts and a dark head with thick sideburns. Juveniles are heavily marked, with vertical streaks instead of horizontal bars on the breast. Despite considerable age-related and geographic variation, an overall steely, barred look remains.
Peregrines do not make stick nests; although they may use old common raven (Corvus corax) or great horned owl (Bubo virginianus) stick nests. The cliff usually has a small cave or overhung ledge large enough to contain three or four full-grown nestlings. Several holes or ledges that can be used in alternate years are apparently not an absolute requirement but probably increase the suitability of the cliff (Recovery Plan, 1982).
Peregrine falcons generally reach breeding maturity at 2 years of age. Usually, the male arrives at a nesting site and begins a series of aerial acrobatic displays to attract a mate. An average clutch of four eggs is laid in the spring, hatching about a month later. Peregrines vigorously defend their nests, although they may abandon them if severely or continuously harassed.
As a result, there was a slow but drastic decline in the number of peregrine falcons in most areas of its range in North America. By the time peregrine falcons were listed as endangered in 1970, the eastern population of the American peregrine falcon was gone and the populations in the west had declined by as much as 90 percent below historical levels. By 1975, there were only 324 known nesting pairs of American peregrine falcons.
An aggressive recovery program began in 1974 and resulted in over 6,000 falcons being reintroduced to the wild. Now there are about 3,000 breeding pairs of American peregrine falcons in Canada, Mexico, and the United States. Territory occupancy, nest success, and productivity are all at levels considered normal for healthy peregrine falcon populations.
In August 1999, the U.S. Fish and Wildlife Service removed the American peregrine falcon from the list of endangered and threatened species, marking one of the most dramatic successes of the Endangered Species Act. Post-delisting monitoring will continue until 2015.
Surveys in 2013 recorded a total of 45 peregrine falcon territories on the eight Channel Islands, and 27 of those territories had eggs or chicks by the end of April 2013. In 2013 there were 5 territories on Anacapa, 16 on Santa Cruz, 13 on Santa Rosa, 9 on San Miguuel, and 3 on Santa Barbara (Sharpe 2013).