[US FWS Photograph By Unknown Photographer]
The peregrine falcon is one of nature's swiftest and most beautiful birds of prey. The name comes from the latin word peregrinus, meaning "foreigner" or "traveller." It is noted for its speed, grace, and aerial skills. There are three subspecies of the peregrine falcon in North America: the American, Arctic, and Peale's.
Peregrine falcons are medium-sized hawks with long pointed wings. Adults have slate blue-gray wings and backs barred with black; pale undersides; white faces with a black stripe on each cheek; and large, dark eyes. Younger birds are darker below and browner.
Peregrine falcons are roughly crow-sized -- about 15 to 21 inches long -- with a wingspan of about 40 inches. As with many raptors, or birds of prey, females are larger than males.
Peregrine falcons live mostly along mountain ranges, river valleys, and coastlines. Historically, they were most common in parts of the Appalachian Mountains and nearby valleys from New England south to Georgia, the upper Mississippi River Valley, and the Rocky Mountains. Peregrines also inhabited mountain ranges and islands along the Pacific Coast from Mexico north to Alaska and in the Arctic tundra.
Peregrine falcons are found in other parts of the world. Most peregrines from northern Alaska, Canada, and Greenland migrate in the fall to Central and South America. On the way, they often hunt along the barrier islands on the Atlantic and Gulf of Mexico Coasts. Peregrines that nest south of Canada migrate lesser distances, and some may not migrate at all.
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.
The nest is a scrape or depression dug in gravel on a cliff ledge. Rarely, peregrines will nest in a tree cavity or an old stick nest. Unlike many other animals that cannot coexist with urbanization, some peregrines have readily accepted man-made structures as breeding habitat. For example, skyscraper ledges, tall towers, and bridges serve as the ecological equivalent of a cliff ledge. In 1988, 21 nesting pairs of peregrines present in various urban areas throughout North America successfully fledged more than 40 young.
Peregrine falcons feed primarily on other birds, such as songbirds, shorebirds, ducks, and in urban areas, starlings and pigeons. Flying high above their intended prey, peregrines will "stoop" or dive and strike in mid-air, killing the prey with a sharp blow. Scientists estimate the speed of a diving peregrine to be more than 200 mph.
Peregrine falcons have never been very abundant. Studies in the 1930s and 1940s estimated about 500 breeding pairs of peregrine falcons in the eastern United States and about 1,000 pairs in the West and Mexico. Then, beginning in the late 1940s, peregrine falcons suffered a devastating and rapid decline. By the mid-1960s, the species had been eliminated from nearly all of the eastern U.S. Although less severe, the decline spread west, where peregrine populations were reduced by 80 to 90 percent by the mid-1970s. At that time, only those populations with Peale's falcons nesting along the north Pacific Coast in Alaska and British Columbia appeared to be stable.
Scientists at the Patuxent Wildlife Research Center near Laurel, Maryland, investigating the peregrine's decline, found unusually high concentrations of the pesticide DDT and its breakdown product DDE in peregrine falcons and other birds of prey. The peregrines accumulated DDT in their tissues by feeding on birds that had eaten DDT-contaminated insects or seeds. The toxic chemical interfered with eggshell formation. As a result, falcons laid eggs with shells so thin they often broke during incubation or otherwise failed to hatch. As too few young were raised to replace adults that died, peregrine populations seriously declined.
In 1970, the American and Arctic peregrine falcon subspecies were listed as endangered (under a law that preceded the Endangered Species Act of 1973), meaning they were considered in danger of extinction throughout all or a significant portion of their ranges. Because DDT and other pesticides were not used in the northerly areas where Peale's peregrines lived, these falcons declined to a lesser degree and were not listed. In addition, Peale's peregrines were not susceptible to picking up DDT in other areas because they do not migrate and feed largely on non- migratory prey.
In 1972, DDT was banned for most uses in the U.S. However, DDE residues are still found in some areas of the country, and DDT continues to be used in many Latin American countries where some peregrines and their prey spend the winter.
The U.S. Fish and Wildlife Service established peregrine falcon recovery teams comprised of federal, state, and independent biologists to recommend actions necessary to restore peregrines in the U.S. As part of recovery efforts, scientists at Cornell University successfully bred and raised peregrine falcons in captivity. The Peregrine Fund, a private organization, developed a major propagation facility in Idaho.
As part of a cooperative effort among the Fish and Wildlife Service, state wildlife agencies, and The Peregrine Fund, in 1974 scientists began releasing captively produced young falcons into the wild. Reintroduction of peregrines in the East ended in 1991, and based on signs of the peregrine's recovery, only a few small reintroductions are still taking place in certain areas of the West. In all, more than 4,000 peregrines were released to their former habitat as part of reintroduction efforts.
To release captively bred peregrines, young birds were placed in a specially equipped box on top of a man-made tower or cliff ledge. At first, the birds were fed through a chute so they could not see their human benefactors. When they were old enough, the box was opened and the young peregrines could begin testing their wings. Gradually, their food was reduced as the young falcons learned to hunt on their own. This process is known as hacking.
Arctic peregrine falcons may have declined by as much as 80 percent; however, enough survived the pesticide era that releases of captively bred young were not necessary. Following restrictions on the use of DDT and recovery efforts under the Endangered Species Act, Arctic peregrine numbers increased to the point that the subspecies was reclassified to "threatened" in 1984. "Threatened" status is a less dire category than "endangered," meaning a species is considered likely to become endangered, but is not in danger of extinction. Then, in October 1994, the Fish and Wildlife Service announced the Arctic peregrine falcon had increased in numbers to the point that the subspecies no longer needed the protection of the Endangered Species Act -- another endangered species success story. There are now thousands of Arctic peregrines in North America and the vast majority of peregrines on the continent belong to this subspecies.
Populations of American peregrine falcons are now estimated to be about 1,200 breeding pairs in the Lower 48 states and Alaska, with additional birds in Canada and Mexico, and the subspecies has reached or is approaching recovery goals throughout North America. Today, the Fish and Wildlife Service is considering removing the American peregrine falcon from the Endangered Species List.
The restrictions placed on the use of DDT and the protection afforded by the Endangered Species Act almost certainly saved the peregrine falcon from extinction. A cleaner environment and the success of reintroduction efforts provide great promise for the peregrine falcon's full recovery in North America.
revised July 1995
Initially found at: Peregrine Falcon (Endangered Species)