The Peregrine Falcon (Falco peregrinus), also known simply as the Peregrine, and historically as the “Duck Hawk” in North America, is a cosmopolitan bird of prey in the family Falconidae.
It is a large, crow-sized falcon, with a blue-gray back, barred white underparts, and a black head and “moustache”. It can reach speeds over 322 km/h (200 mph), making it the fastest animal in the world. As is common with bird-eating raptors, the female is much bigger than the male.
Experts recognize 17–19 subspecies, which vary in appearance and range; there is disagreement over whether the distinctive Barbary Falcon is a subspecies or a distinct species.
The Peregrine’s breeding range includes land regions from the Arctic tundra to the Tropics. It can be found nearly everywhere on Earth, except extreme polar regions, very high mountains, and most tropical rainforests; the only major ice-free landmass from which it is entirely absent is New Zealand. This makes it the world’s most widespread bird of prey.
Both the English and scientific names of this species mean “wandering falcon”, referring to the migratory habits of many northern populations.
The Peregrine Falcon has a body length of 34 to 58 centimetres (13–23 in) and a wingspan of around 80 to 120 centimetres (31–47 in).
The male and female have similar markings and plumage, but as in many birds of prey the Peregrine Falcon displays marked reverse sexual dimorphism in size, with the female measuring up to 30 percent larger than the male] Males weigh 440–750 g, and the noticeably larger females weigh 910–1500 g; for variation in weight between subspecies, see under that section below.
The back and long, pointed wings of the adult are usually bluish black to slate gray with indistinct darker barring (see “Subspecies” below); the wingtips are black. The underparts are white to rusty and barred with thin clean bands of dark brown or black. The tail, colored like the back but with thin clean bars, is long, narrow and rounded at the end with a black tip and a white band at the very end. The top of the head and a “mustache” along the cheeks are black, contrasting sharply with the pale sides of the neck and white throat.
The cere is yellow, as are the feet, and the beak and claws are black. The upper beak is notched near the tip, an adaptation which enables falcons to kill prey by severing the spinal column at the neck. The immature bird is much browner with streaked, rather than barred, underparts, and has a pale bluish cere.
The Peregrine Falcon feeds almost exclusively on medium sized birds such as doves, waterfowl, songbirds, waders and pigeons. Worldwide, it is estimated that between 1,500 and 2,000 bird species (up to roughly a fifth of the world’s bird species) are predated by these falcons.
In North America, prey has varied in size from 3-g hummingbirds to a 3.1-kg Sandhill Crane (killed by a peregrine in a swoop). Other than bats taken at night, it rarely hunts small mammals, but will on occasion take rats, voles, hares, mice and squirrels; the coastal populations of the large subspecies pealei feed almost exclusively on seabirds. In the Brazilian mangrove swamp of Cubatão, a wintering falcon of the subspecies tundrius was observed while successfully hunting a juvenile Scarlet Ibis.
Insects and reptiles make up a small proportion of the diet, which varies greatly depending on what prey is available.
In urban areas, the main item of the Peregrine’s diet is the Rock or Feral Pigeon, which comprise 80% or more of the dietary intake for peregrines in some cities. Other common city birds are also taken regularly, such as Mourning Doves, Common Swifts, Northern Flickers, Common Starlings, American Robins and various corvids.
The Peregrine Falcon hunts at dawn and dusk, when prey are most active, but in cities also nocturnally, particularly during migration periods when hunting at night may become prevalent. Nocturnal migrants taken by Peregrines include species as diverse as Yellow-billed Cuckoo, Black-necked Grebe, Virginia Rail and Common Quail.
It requires open space in order to hunt, and therefore often hunts over open water, marshes, valleys, fields and tundra. It searches for prey either from a high perch or from the air. Once prey is spotted, it begins its stoop, folding back the tail and wings, with feet tucked.
The air pressure from a 200 mph (320 km/h) dive could possibly damage a bird’s lungs, but small bony tubercles in a falcon’s nostrils guide the shock waves of the air entering the nostrils (compare intake ramps and inlet cones of jet engines), enabling the bird to breathe more easily while diving by reducing the change in air pressure. To protect their eyes, the falcons use their nictitating membranes (third eyelids) to spread tears and clear debris from their eyes while maintaining vision. Prey is struck and captured in mid-air; the Peregrine Falcon strikes its prey with a clenched foot, stunning or killing it, then turns to catch it in mid-air. The Peregrine will drop it to the ground and eat it there if it is too heavy to carry. Prey is plucked before consumption.
The Peregrine Falcon is sexually mature at the end of the first year of age but in healthy populations they breed after two to three years of age.
The pair mates for life and returns to the same nesting spot annually.
The courtship flight includes a mix of aerial acrobatics, precise spirals, and steep dives. The male passes prey it has caught to the female in mid-air. To make this possible, the female actually flies upside-down to receive the food from the male’s talons.
The Peregrine Falcon is territorial during the breeding season; nesting pairs are usually more than 1 km (0.6 miles) apart, and often much farther, even in areas with large numbers of pairs. The distance between nests ensures sufficient food supply for pairs and their chicks. Within a breeding territory, a pair may have several nesting ledges; the number used by a pair can vary from one or two to seven in a 16 year period. The pair defends the chosen nest site against other Peregrines, and often against ravens, herons, gulls and (in ground nest) mammals like foxes, wolverines, felids, bears and wolves.
Both nests and (less frequently) adults are predated by larger-bodied raptorial birds like eagles, large owls, or Gyrfalcons. Peregrines defending their nests have managed to kill raptors as large as Golden Eagles and Bald Eagles (which they normally avoid) that have come close to the nest.
The Peregrine Falcon nests in a scrape, normally on cliff edges or, today regularly in many parts of its range, on tall buildings or bridges. Cliff nests are generally located under an overhang, on ledges with vegetation, and south-facing sites are favored. In some regions, as in parts of Australia and on the west coast of Northern North-America, large tree hollows are used for nesting. Before the demise of most European peregrines, there was a large population of peregrines in central and western Europe using the disused nests of other large birds. The female chooses a nest site, where she scrapes a shallow hollow in the loose soil, sand, gravel, or dead vegetation in which to lay eggs. No nest materials are added. In remote, undisturbed areas such as the Arctic, steep slopes and even low rocks and mounds may be used as nest sites. The human-made structures used for breeding closely resemble the natural cliff ledges that the Peregrine prefers for its nesting locations.
Mostly three to four eggs (range 1-5) are laid in the scrape. The eggs are white to buff with red or brown markings. They are incubated for 29 to 33 days, mainly by the female. The male also helps with the incubation of the eggs over day, but at night only the female incubates. The date of egg-laying varies according to locality, but is generally from February to March in the Northern Hemisphere, and from July to August in the Southern Hemisphere (the Australian subspecies macropus may breed as late as November and equatorial populations may nest anytime between June and December). The female generally lays another clutch if the eggs are lost early in the nesting season, though this is extremely rare in the Arctic owing to the short summer season. As a result of some infertile eggs and natural losses of nestlings, the average number of young found in nests is 2.5, and the average number that fledges is about 1.5.
After hatching, the eyases, or chicks, are covered with creamy-white down and have disproportionately large feet. The male, which is called the “tiercel”, brings food to the female and chicks, but the chicks are fed by the female, which stays at the nest and watches the young. The hunting territory of the parents can extend a radius of 19 to 24 km (12-15 miles) from the nest site. Chicks fledge 42 to 46 days after hatching, and remain dependent on their parents for up to two months.
The Peregrine Falcon lives mostly along mountain ranges, river valleys, coastlines, and increasingly in cities. In mild-winter regions, it is usually a permanent resident, and some individuals, especially adult males, will remain on the breeding territory. Only populations that breed in Arctic climes typically migrate great distances during the northern winter. The Peregrine Falcon is often stated to be the fastest animal on the planet in its hunting dive, the stoop, which involves soaring to a great height and then diving steeply at speeds commonly said to be over 320 km/h (199 mph), and hitting one wing of its prey so as not to harm itself on impact. A study testing the flight physics of an ‘ideal falcon’ found a theoretical speed limit at 400 km/h (250 mph) for low altitude flight and 625 km/h (390 mph) for high altitude flight. In 2005, Ken Franklin recorded a falcon stooping at a top speed of 389 km/h (242 mph).
The life span in the wild is up to 15.5 years. Mortality in the first year is between 59–70%, declining to between 25–32% in adults. Apart from anthropogenic threats like collision with human-made objects, the Peregrine may be killed by large eagles or large owls. The Peregrine Falcon is host to a range of parasites and pathogens. It is a vector for Avipoxvirus, Newcastle disease virus, Falconid herpesvirus 1 (and possibly other Herpesviridae), and some mycoses and bacterial infections. Endoparasites include Plasmodium relictum (usually not causing malaria in the Peregrine Falcon), Strigeidae trematodes, Serratospiculum amaculata (nematode), and tapeworms. Known Peregrine Falcon ectoparasites are chewing lice Ceratophyllus garei (a flea), and Hippoboscidae flies (Icosta nigra, Ornithoctona erythrocephala).
This species was first described by Marmaduke Tunstall in his 1771 Ornithologia Britannica under its current binomial name. The scientific name Falco peregrinus, means “wandering falcon” in Latin. Indeed, the species’ common name refers to its wide-ranging flights in most European languages. The Latin term for falcon, falco, is related to falx, the Latin word meaning sickle, in reference to the silhouette of the falcon’s long, pointed wings in flight.
The Peregrine Falcon belongs to a genus whose lineage includes the hierofalcons and the Prairie Falcon (F. mexicanus). This lineage probably diverged from other falcons towards the end of the Late Miocene or in the Early Pliocene, about 8–5 million years ago (mya). As the Peregrine-hierofalcon group includes both Old World and North American species, it is likely that the lineage originated in western Eurasia or Africa. Its relationship to other falcons is not clear; the issue is complicated by widespread hybridization confounding mtDNA sequence analyses; for example a genetic lineage of the Saker Falcon (F. cherrug) is known which originated from a male Saker producing fertile young with a female Peregrine ancestor some 100,000 years ago.
Today, Peregrines are regularly hybridized in captivity with other species such as the Lanner Falcon (F. biarmicus) to produce the “perilanner”, a somewhat popular bird in falconry as it combines the Peregrine’s hunting skill with the Lanner’s hardiness, or the Gyrfalcon to produce large, strikingly colored birds for the use of falconers. As can be seen, the Peregrine is still genetically close to the hierofalcons, though their lineages diverged in the Late Pliocene (maybe some 2.5–2 mya in the Gelasian).
There are many subspecies of Peregrine Falcon, including:
These last two races are often split as Barbary Falcon Falco pelegrinoides. There is a 0.6–0.7% genetic distance in the Peregine-Barbary Falcon (“peregrinoid”) complex. These birds inhabit arid regions from the Canary Islands along the rim of the Sahara through the Middle East to Central Asia and Mongolia. They have a red neck patch but otherwise differ in appearance from the Peregrine proper merely according to Gloger’s Rule. The Barbary Falcon has a peculiar way of flying, beating only the outer part of its wings like fulmars sometimes do; this also occurs in the Peregrine, but less often and far less pronounced. The Barbary Falcon’s shoulder and pelvis bones are stout by comparison with the Peregrine, and its feet are smaller. They have no postzygotic reproduction barriers in place, but they breed at different times of year than neighboring Peregrine Falcon subspecies
The Peregrine Falcon became an endangered species because of the use of pesticides, especially DDT during the 1950s, 60s, and 70s. Pesticide biomagnification caused organochlorine to build up in the falcons’ fat tissues, reducing the amount of calcium in their eggshells. With thinner shells, fewer falcon eggs survived to hatching.] In several parts of the world, such as the eastern USA and Belgium, this species became extinct as a result.
Peregrine eggs and chicks are often targeted by black marketeers and unscrupulous egg collectors, so it is normal practice not to publicize unprotected nest locations.
The Peregrine Falcon was used in falconry for more than 3,000 years, beginning with nomads in central Asia. Due to its ability to dive at high speeds, it was highly sought-after and generally used by experienced falconers. Peregrine Falcons are also occasionally used to scare away birds at airports to reduce the risk of bird-plane strikes, improving air-traffic safety, and were used to intercept homing pigeons during World War II.
In the USA, Canada, Germany and Poland, Wildlife services in Peregrine Falcon recovery teams breed the species in captivity. The chicks are usually fed through a chute or with a hand puppet mimicking a Peregrine’s head, so they cannot see to imprint on the human trainers. Then, when they are old enough, the rearing box is opened, allowing the bird to train its wings. As the fledgling gets stronger, feeding is reduced forcing the bird to learn to hunt. This procedure is called hacking back to the wild. To release a captive-bred falcon, the bird is placed in a special cage at the top of a tower or cliff ledge for some days or so, allowing it to acclimate itself to its future environment. Worldwide recovery efforts have been remarkably successful. The widespread restriction of DDT use eventually allowed released birds to breed successfully. The Peregrine Falcon was removed from the U.S. Endangered Species list on August 25, 1999. The population studies and recovery plan devised by Dr. Richard M. Bond and William Griffee are considered by the Cooper Ornithological Society and the Pergrine Fund to have been critical to the recovery effort for the Peregrine Falcon population in the United States.
Many Peregrine Falcons have settled in large cities, nesting on cathedrals, skyscraper window ledges, and the towers of suspension bridges. As early as 1946, Peregrine Falcons were nesting atop Philadelphia City Hall, which is believed to be among the first artificial structures in the world to be used as a nest site by this species. In Virginia, state officials working with students from the Center for Conservation Biology of the College of William and Mary in Williamsburg successfully established nesting boxes high atop the George P. Coleman Memorial Bridge on the York River, the Benjamin Harrison Memorial Bridge and Varina-Enon Bridge on the James River, and at other similar locations. Thirteen new chicks were hatched in this Virginia program during a recent year. Over 250 falcons have been released through the Virginia program. The New York State Department of Environmental Conservation reported that there were 67 pairs of peregrine falcons in the state during 2008.
In Britain, there has been a recovery of populations since the crash of the 1960s. This has been greatly assisted by conservation and protection work led by the Royal Society for the Protection of Birds. Peregrines now breed in many mountainous and coastal areas, especially in the west and north, and nest in some urban areas, capitalizing on the urban pigeon populations for food.
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