American Peregrine Falcon

Description and biology

Peregrine (pronounced PER–a–grin) comes from the Latin word peregrinus, meaning “foreigner” or “traveler.” One of nature’s most beautiful birds of prey, the peregrine falcon is noted for its speed, grace, and aerial (flying) skills. There are three subspecies of the peregrine falcon in North America: American, Arctic, and Peale’s.

The American peregrine falcon is a medium–sized bird with long, pointed wings. It measures 15 to 21 inches (38 to 53 centimeters) long, with a wingspan of about 44 inches (118 centimeters).

The plumage (covering of feathers) on its wings is slate blue–gray in color. Its bluish back is marked with black bars, and its underside is pale. Its white face has a black stripe on each cheek. It has large, dark eyes. Younger peregrine falcons are darker underneath and browner overall.

Peregrine falcons feed on smaller birds such as songbirds, shorebirds, and ducks. In urban areas, they eat starlings and pigeons. Falcons usually hunt their prey while in flight. Flying high above their intended prey, they “stoop” or dive at speeds of more than 200 miles (320 kilometers) per hour. In mid–air, they strike and kill prey with a blow from their sharp talons.

Peregrine falcons first breed when they are two or three years old. After selecting a nesting site on a high cliff (or on a bridge or ledge of a skyscraper in a city), a male peregrine begins a series of aerial acrobatic displays to attract a female. After rising to a great height, the male folds his wings and streaks down like a missile, pulling up at the last moment and soaring into a series of loops.

Once the male and female mate, the female lays 3 to 5 eggs, which hatch after 32 to 34 days. The nestlings or young leave the nest when they are 35 to 40 days old. Pairs will usually use the same nesting site for many years.

Habitat and current distribution

American peregrine falcons live mostly along mountain ranges, river valleys, and coastlines from Alaska and the Arctic tundra south into Mexico. Historically, they were most common in the Rocky Mountains, the upper Mississippi River Valley, and in parts of the Appalachian Mountains and nearby valleys from New England south to Georgia.

Biologists (people who study living organisms) estimate that more than 1,200 breeding pairs of American peregrine falcons exist in the contiguous United States (the connected 48 states) and Alaska, with additional birds in Canada and Mexico.

History and conservation measures

Peregrine falcons have never been very abundant. In the 1930s and 1940s, it was estimated that about 500 breeding pairs of peregrine falcons existed 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 rapid decline.

The reason behind the falcon’s devastating drop was the rampant spraying of the powerful pesticide dichlorodiphenyl-trichloroethane (DDT), especially after World War II (1939–45). Farmers, foresters, and others used DDT to kill weeds,
insects, rodents, and other pests that harmed agricultural crops. It was sprayed heavily along coastal areas and wetlands to control mosquitoes and other insects.

DDT does not dissolve in water and does not break down chemically in the environment. Animals that ate insects and plant materials in these sprayed areas ingested DDT. Once inside the body, the chemical never leaves; it stays in the fatty tissues.

At each step higher in the food chain, the DDT residue becomes more concentrated in the fatty tissues of the contaminated animals. As predators, peregrine falcons are at the top of the food chain. When they eat a contaminated animal, they ingest a concentrated form of the pesticide.

DDT reduces the amount of calcium in the eggshells of female peregrines (and other birds of prey). Thus, peregrines began laying thin–shelled eggs that cracked before they were able to hatch. Fewer and fewer nestlings were born, and the falcon population plummeted. By the mid–1960s, no breeding pairs of falcons remained in the eastern United States.

The U.S. Fish and Wildlife Service (USFWS) placed the American peregrine falcon on the Endangered Species List in 1970. Two years later, DDT was banned for most uses in the United States. Cooperating together, the USFWS, state wildlife agencies, and the Peregrine Fund (at Cornell University) began releasing captive–bred young falcons into the wild in 1974.

The American peregrine falcon’s recovery has been successful. Reintroduction of peregrines in the eastern United States ended in 1991; only a few small reintroductions are still taking place in certain areas of the west. In all, more than 4,000 peregrines have been released to their former habitat as part of this recovery plan.

In May 1998, the U.S. secretary of the interior proposed that the American peregrine falcon be one of 29 species either downgraded or removed from the Endangered Species List. On August 25, 1999, it was delisted as a recovered species (with a required five–year monitoring program), and is considered one of the success stories of U.S. conservation.