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Falcons

Falcons

Interaction of falcons with humans

Current status of North American falcons

Resources

Falcons are birds of prey in the family Falconidae. There are 39 species of true falcons, all in the genus Falco. Like other species in the order Falconiformes (which also includes hawks, eagles, osprey, and vultures), falcons have strong raptorial (or grasping) talons, a hooked beak, extremely acute vision, and a fierce demeanor. Falcons can be distinguished from other raptors by the small toothlike serrations (called tomial teeth) on their mandibles and by their specific coloration. They also have distinctive behavior patterns, such as killing their prey by a neck-breaking bite, head-bobbing, defecating below the perch or nest, and an often swift and direct flight pattern.

Falcons can be found on all continents except Antarctica. Some species have a very widespread distribution. In particular, the peregrine falcon (Falco peregrinus ) is virtually cosmopolitan, having a number of subspecies, some of them specific to particular oceanic islands. Other falcons are much more restricted in their distribution: for example, the Mauritius kestrel (F. puctatus ) only breeds on the island of Mauritius in the Indian Ocean. At one time, fewer than ten individuals of this endangered species remained, although populations have since increased as a result of strict protection and a program of captive breeding and release.

Species of falcons exploit a very wide variety of habitat types, ranging from the high arctic tundra to boreal and temperate forest, prairie and savanna, and tropical forests of all types. Falcons catch their own food. Most species of falcons catch their prey in flight, although kestrels generally seize their food on the ground, often after hovering above. As a group, falcons eat a great range of foods; however, particular species are relatively specific in their feeding, limiting themselves to prey within certain size ranges. The American kestrel (F. sparverius ), for example, eats mostly insects, earthworms, small mammals, and small birds, depending on their seasonal availability. Heavier, more powerful falcons, such as the peregrine, will eat larger species of birds, including ducks, sea-birds, grouse, pigeons, and shorebirds.

The nests of many falcons are rather crudely made, often a mere scrape on a cliff ledge or on the ground. Some species, however, nest in natural cavities or old woodpecker holes in trees, as is the case with the American kestrel. Most kestrels will also use nest boxes provided by humans. Peregrines, which sometimes breed in cities, will nest on ledges on tall buildings, a type of artificial cliff.

The courtship displays of falcons can be impressive, in some cases involving spectacular aerial displays and acrobatics. Those of the peregrine are most famous. To impress a female (properly called a falcon), the male bird (called a tiercel) will swoop down from great heights at speeds as high as 217 mph (350 km/h) and will execute rolls and other maneuvers, including midair exchanges of food with its intended mate. Although this species undertakes long-distance seasonal migrations, the birds return to the same nesting locale and, if possible, will mate with the same partner each year. Incubation of falcon eggs does not begin until the entire clutch is laid, so all young birds in a nest are about the same size. This is different from

many other birds of prey, which incubate as soon as the first egg is laid, resulting in a great size range of young birds in the nest. In falcons, the female (which is always larger than the male) does most of the incubating, while the tiercel forages widely for food.

The most northerly species is the gyrfalcon (F. rusticolus ), a large white species that breeds throughout the Arctic of North America and Eurasia. This bird usually has its nest, or aerie, high on a cliff. The nest site is typically reused for many years, and can often be discerned from miles away by the colorful orange and white streakings of guano and rock lichens growing in a fertilized zone extending several meters beneath the nest. Depending on the nearby habitat, gyrfalcons may feed on ptarmigan, seabirds, or small migratory birds such as buntings and shorebirds.

Other familiar falcons of North America include the prairie falcon (F. mexicanus ), which ranges widely in open habitats of the southwestern region, and the merlin or pigeon hawk (F. columbarius ), which breeds in boreal and subarctic habitats and winters in the southern part of the continent and Central America.

Interaction of falcons with humans

Falcons fascinate many people, largely because of their fierce, predatory behavior. As a result, sightings of falcons are considered to be exceptional events for bird watchers and many other people. Some species of falcons, such as kestrels, are also beneficial to humans because they eat large numbers of mice, grasshoppers, and locusts that are potential agricultural pests.

However, as recently as the middle of this century, some species of falcons were themselves regarded as major pestsdangerous predators of game birds. As a result, falcons, especially peregrines, were killed in large numbers by professional gamekeepers and hunters. Fortunately, this practice ended, and falcons are now rarely hunted by humans. However, young falcons are still taken from wild nests, often illegally, for use in falconry.

Falconry is a sport with a three-thousand-year history, in which falcons are free-flown to catch and kill game birds, such as grouse, ptarmigan, pheasants, and ducks. Falcons are rather wild birds, however, and they must be well trained or they may not return to the falconers hand. Because of their power, speed, and fierce and independent demeanor, the most highly prized species in falconry are the largest, most robust falcons, especially the gyrfalcon and the peregrine.

Some birds trained in falconry are not only used for sport. Falcons are also used in some places to drive birds, such as gulls, away from airports in an effort to prevent catastrophic collisions with aircraft.

Some species of falcons have suffered considerable damage from the widespread usage of certain types of insecticides. Most harmful has been the use of persistent bioaccumulating chlorinated-hydrocarbon insecticides, such as DDT and dieldrin. These and other related chemicals (such as polychlorinated biphenyls, or PCBs) have caused the collapse of populations of peregrines and other species of birds. For example, populations of the most widespread subspecies of the peregrine falcon in North America (F. peregrinus anatum) were widely destroyed by these toxic exposures, and the northern subspecies (F. p. tundrius) suffered large declines. However, because of restrictions on the use of these chemicals since the 1970s, they now have less of an effect on falcons and other birds. In fact, some breeding and migratory populations of peregrine falcons in North America have significantly increased since the late 1970s. This recovery has been aided by large captive breeding programs in the United States and Canada aimed at releasing these birds into formerly occupied or underpopulated habitats.

Still, the populations of many species of falcons is greatly reduced, and some species are threatened or endangered. Protecting these species would best be accomplished by ensuring that extensive tracts of appropriate natural habitat always remain available for falcons and other wildlife. However, in more acute cases, expensive management of the habitat and populations of falcons is necessary to protect these fascinating birds.

Current status of North American falcons

  • Aplomado falcon (Falco femoralis). Has been reintroduced in Texas and is breeding there. Decline in population is thought to have been due to agricultural expansion and to eggshell thinning resulting from the use of pesticides.
  • Collared forest falcon (Micrastur semitorquatus). Southwestern stray.
  • Peregrine falcon (Falco peregrinus). Pesticides and PCB poisoning caused widespread reproductive failure from the 1940s to 1970s, causing species to disappear from many of the former nesting grounds. It has since been reintroduced in many areas, and appears to be doing well locally.
  • Prairie falcon (Falco mexicanus). Species has experienced some eggshell thinning and mercury poisoning (mainly built up from feeding on the seed-eating horned lark). Has declined in some areas (including Utah, western Canada, and agricultural regions of California), but the current population appears stable.
  • American kestrel (Falco sparverius). Decline in population in the Northeast in recent years, but otherwise the population appears stable. Nest boxes have helped maintain populations in some areas.
  • Gyrfalcon (Falco rusticolus). Rare. Has declined in parts of Arctic Europe, but appears stable in North America. Illegal poaching for falconry may be a problem in some areas, but fortunately most nest sites are out of range of human disturbance.
  • Merlin (Falco columbarius). There were earlier indications that this bird was experiencing adverse effects from the use of pesticides in eastern Canada, and from mercury buildup in western Canada. Numbers now appear to be increasing in the northern prairies, and to be remaining stale elsewhere.
  • Crested caracara (Polyborus plancus). Has declined due to loss of habitat due to agricultural expansion and hunting. There has been some evidence of an increase in population in Texas. The population on Guadalupe Island, Mexico, became extinct in 1900.

Resources

BOOKS

Cade, T.J. The Falcons of the World. Ithaca, NY: Cornell University Press, 1982.

del Hoyo, J., A. Elliott, and J. Sargatal. Handbook of the Birds of the World. Vol. 2, New World Vultures to Guineafowl. Barcelona: Lynx Edicions, 2000.

Freedman, B. Environmental Ecology. 2nd ed. San Diego: Academic Press, 1994.

Peterson, Roger Tory. North American Birds. Houghton Miflin Interactive (CD-ROM), Somerville, MA: Houghton Miflin, 1995.

PERIODICALS

Hunt, W. Grainger, Tom J. Cade, and Angel B. Montoya. Home Above the Range: Pairs of Aplomado Falcons Are Nesting in the Southwest Again, Showing Off Their Incredible Hunting and Flying Skills. Natural History 115 (May 2006): 48-54.

Randall Frost

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