American Peregrine Falcon

Falco peregrinus anatum

Description

The Falco peregrinus anatum (peregrine falcon) is a fast-flying bird of prey. It is 15-21 in (38-53 cm) long and has a wingspread of about 3.75 ft (1.4 m). In flight it shows sharply pointed wings and a narrow tail. The peregrine is dark slate above with a broad black mustache and a black cap and nape. It has a white throat and upper breast. The tail is lightly banded. Immature birds are dark brown above, heavily streaked below. The birds's appearance and size varies by region. West of the Great Plains the birds are smaller than their eastern cousins. Average adults show a slight brownish cast to the dorsum. The light-gray wash on the sides and flanks is heavily suffused with rufus. The spotting and barring below is generally not so dark as in birds from the east but a larger proportion of them represent the lighter extreme. Falcons from interior boreal Alaska are larger than those of the west and similar in color but lack much of the brownish cast.

Throughout the world, numerous peregrine falcon subspecies, including the Eurasian peregrine (Falco peregrinus peregrinus ), are Endangered or Threatened. The American peregrine falcon was originally listed as Endangered in 1970, but the relative success of recovery efforts caused the species to be reclassified as Threatened in 1994. The Arctic subspecies was until recently listed as Threatened; it was delisted in 1994. In 1999, the U.S. Fish and Wildlife Service (FWS) delisted the peregrine falcon throughout the United States.

Behavior

The peregrine falcon is monogamous and, while little direct evidence exists concerning the duration of the pair bond in peregrines, it has been suggested that once a pair bond has been established and breeding commences, the pair is likely to remain together unless one of the mates is lost. Full sexual maturation in a wild population is reached at two years for females and three years for males, however birds with immature plumage have been known to breed; this occurs more frequently in females than in males. Breeding success has been documented in birds in excess of fifteen years of age. Typically, birds begin pairing by mid-March; eggs are laid in early April in the south and late April in the north. Clutch size is three to four eggs, which are incubated by both sexes for about 33 days. Males provide most of the prey during incubation, though nest protection is a shared duty (the female, however, is the more aggressive defender). Young peregrines fledge in mid-June to mid-July. For the first eight to 10 days, the chicks are nearly blind and helpless, and require almost constant brooding. Depending on the ambient temperature, some brooding may occur through the first two to three weeks and chicks are frequently sheltered from strong sun and rain over a longer period of time. Peregrines travel up to 7 mi (11 km) from their nest site to hunting areas, flying at speeds in excess of 60 mph (96 km per hour). They prey on a wide variety of birds, striking victims from above with their talons after a dramatic, high-speed dive. Little is known about post-breeding movement, but peregrines are occasionally reported within their breeding range throughout the winter near large rivers or water-fowl refuges such as Monte Vista and Bear River National Wildlife Refuges in southern Colorado and northern Utah.

Habitat

Peregrines are found in a great variety of hunting habitats, such as grasslands, meadows, and open country. Migrant and wintering falcons are well known for frequenting coastal, estuaries and inter-tidal mudflats, where they prey heavily on shore-birds and waterfowl. They prefer cliffs for nesting sites; reintroduced birds now regularly nest on high-rise buildings and bridges in metropolitan areas, primarily in the southern portion of their range. Although peregrine falcons are normally intolerant of human activity near their eyrie (nest site), in urban situations, breeding and wintering falcons may demonstrate a remarkable tolerance to human activity, except in the immediate vicinity of the nest site.

Distribution

Historically, peregrines have ranged throughout the world, wherever prey has been abundant. In North America the American peregrine nested from central Alaska across north central Canada and south to Central Mexico. The American peregrine also winters along the Pacific coast from British Columbia southward. The species has been present in the United States for at least 30,000 years. Fossil remains have been found at the La Brea Tar Pits in California, where Pleistocene remains are believed to range from 5,000-40,000 years in age. Peregrine remains have also been found in Indian caves and mid-dens. Historic records indicate that the peregrine has been only locally common throughout the United States. In the 1930s and 1940s there were at least 210 active nests and about 350 pairs throughout the eastern United States. By the mid-1960s the peregrine was extirpated from the East as a breeding species. In 1973 it was estimated that there were between 250-350 active aeries (nests and broods) in the western United States. As of 1983, somewhat more than 200 of these aeries survived. All breeding pairs in the East since the 1960s are the result of an ambitious effort to reestablish the species through the release of captive-bred birds. This program has achieved considerable success, and the peregrine falcon again breeds throughout much of its original range in the United States. The peregrine falcon has been successfully reestablished as a breeding species in the eastern United States and populations have increased throughout the western United States and in Alaska. According to the Peregrine Fund there were, by the late 1980s, about 100 breeding pairs of peregrines in the East, about 18 in the Midwest, and around 400 in the western United States. As of June, 1995, the FWS reported that the population was estimated at nearly 1,000 nesting pairs in the lower 48 states and more than 300 in Alaska, with additional nesting birds in Canada and Mexico.

Threats

The increased use of organochlorine pesticides, especially DDT, after 1950 was the major cause of peregrine decline in the United States. Organochlorines cause eggshell thinning in many birds, and was the major cause of low peregrine reproduction. Although banned in the United States in 1972, DDT is still used in many parts of the world. Other toxins remain a serious problem, however, include PCBs. A recent study by state and federal biologists in New Jersey examined contaminant levels in non-viable eggs collected in 1991 and 1992 from eight peregrine falcon eyries in New Jersey. The investigators measures levels of mercury (a heavy toxic metal) and other compounds. Eggs from Atlantic coast eyries contained elevated levels of polychlorinated biphenyls (PCBs), indicating that PCBs were likely contributors to hatching failure on the Atlantic coast. In contrast, eggs collected from falcon nests along the Delaware River did not have elevated PCB levels; biologists attributed these differences to the varying diets between the Atlantic coast and Delaware River birds.

In addition, dioxin concentrations in eggs from the Atlantic coast were among the highest ever documented in peregrine falcon eggs, and may mean mercury concentrations at Atlantic coast eyries are more than 30 times greater than at Delaware River eyries. However, productivity and eggshell thinning data do not indicate that peregrines in New Jersey are experiencing reproductive impairment because of persistent contaminants. On the other hand, some recent peregrine deaths in the United States have been linked to various, contemporary, short-lived pesticides.

Conservation and Recovery

Because the range of the peregrine includes the entire continental United States, the FWS developed regional recovery plans. The eastern-region plan is concerned with reestablishing the extirpated population; the West Coast plan is concerned with protecting existing aeries; and the Rocky Mountain/Southwest plan is aimed at reintroduction of the falcon in the northern Rocky Mountain states, augmenting existing pairs with introduced peregrines in the central Rocky Mountain states, and monitoring and protecting the species in the southwestern states. Recovery efforts concentrated on expanding the captive breeding and release program. Captive breeding technology is now well beyond the experimental stage. A large breeding stock of American peregrine falcons is available, and extensive release programs are in operation. The principal propagation center in the East has been the Peregrine Fund at Cornell University. Peregrines were produced there from 1973 through 1985. In 1986, the captive flock was moved to Boise, Idaho, where it continues to provide young for release in the eastern United States. The Peregrine Fund, a private conservation organization dedicated to saving the species, has released about 3,000 captive-bred peregrines since the early 1970s. Federal and state agencies, together with private conservation groups such as the Peregrine Fund, have initiated release programs throughout the country. While most reintroductions have taken place in wilderness areas, some have taken advantage of the peregrine's ability to nest on bridges and urban high-rises. Captive-bred birds have been released in a number of U.S. cities, including Milwaukee, Wisconsin; Salt Lake City, Utah; Albany, New York; and Baltimore, Maryland. Five baby peregrines were sent to a nesting box on top of the Guardian Building in Detroit as part of the reintroduction effort in the Midwest. Peregrines have also been found nesting on top of the Throgs Neck bridge on Long Island, New York. The presence of these urban raptors often stimulates local interest in preservation and passing motorists occasionally tie up traffic to rescue a fallen nestling. The success of the recovery of the Arctic peregrine (re-classified from Endangered to Threatened in 1984 and finally delisted altogether in 1994), is seen as a beacon of hope for the recovery of the American peregrine. The American peregrine is following the same path of progress, having been reclassified to Threatened in 1994, and being delisted in 1999.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Canter Dr.
Hadley, Massachusetts 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8200
http://www.northeast.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

References

Cade, T. J. 1982. The Falcons of the World. Cornell University Press, Ithaca, New York.

Craig. G. 1986. "Peregrine Falcon." In R. L. Di Silvestro, ed., Audubon Wildlife Report 1986. National Audubon Society, New York.

Ratcliffe, D. A. 1980. The Peregrine Falcon. Buteo Books, Vermillion, South Dakota.

U.S. Fish and Wildlife Service. 1987. "Revised Peregrine Falcon, Eastern Population Recovery Plan." U.S. Fish and Wildlife Service, Newton Corner, Massachusetts.

U.S. Fish and Wildlife Service. 1982. "Pacific Coast American Peregrine Falcon Recovery Plan." U.S. Fish and Wildlife Service, Portland.

U.S. Fish and Wildlife Service. 1984. "American Peregrine Falcon Recovery Plan (Rocky Mountain/Southwest Population)." U.S. Fish and Wildlife Service, Denver.

U.S. Fish and Wildlife Service. 1982. "Recovery Plan for the Peregrine Falcon Alaska Population." U.S. Fish and Wildlife Service, Portland.

U.S. Fish and Wildlife Service. 2000. "Recovery of the Peregrine Falcon." http://endangered.fws.gov/peregrin.html