The peregrine falcon (Falco peregrinus), sometimes referred to simply as the peregrine, is a bird of prey (raptor) in the family Falconidae known for its speed. A large, crow-sized falcon, it has a blue-grey back, barred white underparts and a black head. As is typical for bird-eating (avivore) raptors, peregrine falcons are sexually dimorphic, with females being considerably larger than males. Historically, the bird has also been known as the "black-cheeked falcon" in Australia and the "duck hawk" in North America.
The 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 landmasses from which it is entirely absent are the islands of New Zealand, making it the world's most widespread raptor and one of the most widely found wild bird species. In fact, the only land-based bird species found over a larger geographic area, domestic and feral pigeons, owe their success to human-led introduction. Both are domesticated forms of the rock dove, and are a major prey species for peregrine populations. Due to their greater abundance in cities than most other birds, feral pigeons support many peregrine populations as a staple food source, especially in urban settings.
The peregrine is a highly successful example of urban wildlife in much of its range, taking advantage of tall buildings as nest sites, and an abundance of prey such as pigeons and ducks. Both the English and scientific names of the species mean "wandering falcon", referring to the migratory habits of many northern populations. A total of 18 or 19 regional subspecies are accepted, which vary in appearance. Disagreement existed in the past over whether the distinctive Barbary falcon was represented by two subspecies of Falco peregrinus or was a separate species, F. pelegrinoides, and several of the other subspecies were originally described as species. However, the difference in their appearance is very small, as is their genetic difference, being only about 0.6–0.8% genetically differentiated. That indicates the divergence is relatively recent, occurring during the Last Ice Age, and all major ornithological authorities now treat the Barbary falcon as a subspecies.
Although its diet consists almost exclusively of medium-sized birds, the peregrine will sometimes hunt small mammals, small reptiles, or even insects. Reaching sexual maturity at one year, it mates for life and nests in a scrape, normally on cliff edges or, in recent times, on tall human-made structures. The peregrine falcon became an endangered species in many areas because of the widespread use of various pesticides, especially DDT. Since the ban on DDT from the early 1970s, populations have recovered, supported by large-scale protection of nesting places and releases to the wild.
The peregrine falcon is a well-respected falconry bird due to its strong hunting ability, high trainability, versatility, and availability via captive breeding. It is effective on most game bird species, from small to large. It has also been used as a religious, royal, or national symbol across many eras and civilizations.
Description
The peregrine falcon has a body length of and a wingspan from . The male and female have similar markings and plumage but, as with many birds of prey, the peregrine falcon displays marked sexual dimorphism in size, with the female measuring up to 30% larger than the male. Males weigh and the noticeably larger females weigh . In most subspecies, males weigh less than and females weigh more than , and cases of females weighing about 50% more than their male breeding mates are not uncommon. The standard linear measurements of peregrines are: the wing chord measures , the tail measures and the tarsus measures .
The back and the long pointed wings of the adult are usually bluish black to slate grey with indistinct darker barring (see "Subspecies" below); the wingtips are black. The white to rusty underparts are barred with thin clean bands of dark brown or black. The tail, coloured 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 "moustache" 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. An immature bird is much browner, with streaked, rather than barred, underparts, and has a pale bluish cere and orbital ring.
The patch of black feathers below the falcon's eyes is called the malar stripe. A 2021 study of photos from around the world showed that the malar stripe is larger in areas that receive more sunlight, and concluded that the stripe serves to improve the falcon's vision by reducing glare.
Taxonomy and systematics
Falco peregrinus was first described under its current binomial name by English ornithologist Marmaduke Tunstall in his 1771 work Ornithologia Britannica. The scientific name Falco peregrinus is a Medieval Latin phrase that was used by Albertus Magnus in 1225. Peregrinus is Latin, meaning "one from abroad" or "coming from foreign parts". It is likely the name was used as juvenile birds were taken while journeying to their breeding location (rather than from the nest), as falcon nests are often difficult to get at. The Latin term for falcon, , is related to , 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 Late Pliocene, about 3–8 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, as the issue is complicated by widespread hybridization confounding mtDNA sequence analyses. One genetic lineage of the saker falcon (F. cherrug) is known to have originated from a male saker ancestor producing fertile young with a female peregrine ancestor, and the descendants further breeding with sakers.
Subspecies Numerous subspecies of Falco peregrinus have been described, with 18 accepted by the IOC World Bird List, and 19 accepted by the 1994 Handbook of the Birds of the World, which considers the Barbary falcon of the Canary Islands and coastal North Africa to be two subspecies (F. p. pelegrinoides and F. p. babylonicus) of Falco peregrinus, rather than a distinct species, F. pelegrinoides. The following map shows the general ranges of these 19 subspecies.
Falco peregrinus anatum, described by Bonaparte in 1838, is known as the American peregrine falcon or "duck hawk"; its scientific name means "duck peregrine falcon". At one time, it was partly included in F. p. leucogenys. It is mainly found in the Rocky Mountains. It was formerly common throughout North America between the tundra and North Mexico, where current reintroduction efforts are being made to restore the population. Most mature F. p. anatum, except those that breed in more northern areas, winter in their breeding range. Most vagrants that reach western Europe seem to belong to the more northern and strongly migratory F. p. tundrius, only considered distinct since 1968. It is similar to the nominate subspecies but is slightly smaller; adults are somewhat paler and less patterned below, but juveniles are darker and more patterned below. Males weigh , while females weigh . It became regionally extinct in eastern North America in the mid 20th century, and populations there now are hybrids as a result of reintroductions of birds from elsewhere. Falco peregrinus babylonicus, described by P.L. Sclater in 1861, is found in eastern Iran along the Hindu Kush and the Tian Shan to the Mongolian Altai ranges. A few birds winter in northern and northwestern India, mainly in dry semi-desert habitats. It is paler than F. p. pelegrinoides and similar to a small, pale lanner falcon (Falco biarmicus). Males weigh , while females weigh . , described by Sharpe in 1873, is also known as the Mediterranean peregrine falcon or the Maltese falcon. It includes F. p. caucasicus and most specimens of the proposed race F. p. punicus, though others may be F. p. pelegrinoides (Barbary falcons), or perhaps the rare hybrids between these two which might occur around Algeria. They occur from the Iberian Peninsula around the Mediterranean, except in arid regions, to the Caucasus. They are non-migratory. It is smaller than the nominate subspecies and the underside usually has a rusty hue. Males weigh around , while females weigh up to . , described by John Latham in 1790, it was formerly called F. p. leucogenys and includes F. p. caeruleiceps. It breeds in the Arctic tundra of Eurasia from Murmansk Oblast to roughly Yana and Indigirka Rivers, Siberia. It is completely migratory and travels south in winter as far as South Asia and sub-Saharan Africa. It is often seen around wetland habitats. It is paler than the nominate subspecies, especially on the crown. Males weigh , while females weigh . Falco peregrinus cassini, described by Sharpe in 1873, is also known as the austral peregrine falcon. It includes F. p. kreyenborgi, the pallid falcon, a leucistic colour morph occurring in southernmost South America, which was long believed to be a distinct species. Its range includes South America from Ecuador, Argentina, and the Falklands. It is non-migratory. It is similar to the nominate subspecies, but slightly smaller with a black ear region. The pallid falcon morph F. p. kreyenborgi is medium grey above, has little barring below and has a head pattern like the saker falcon (Falco cherrug), but the ear region is white. Falco peregrinus ernesti, described by Sharpe in 1894, is found from the Sunda Islands to the Philippines and south to eastern New Guinea and the nearby Bismarck Archipelago. Its geographical separation from F. p. nesiotes requires confirmation. It is non-migratory. It differs from the nominate subspecies in the very dark, dense barring on its underside and its black ear coverts. Falco peregrinus furuitii, described by Momiyama in 1927, is found on the Izu and Ogasawara Islands south of Honshū, Japan. It is non-migratory. It is very rare and may only remain on a single island. It is a dark form, resembling F. p. pealei in colour, but darker, especially on the tail. Falco peregrinus japonensis, described by Gmelin in 1788, includes F. p. kleinschmidti, F. p. pleskei, and F. p. harterti, and seems to refer to intergrades with F. p. calidus. It is found from northeast Siberia to Kamchatka (though it is possibly replaced by F. p. pealei on the coast there) and Japan. Northern populations are migratory, while those of Japan are resident. It is similar to the nominate subspecies, but the young are even darker than those of F. p. anatum. , described by Swainson in 1837, is the Australian peregrine falcon or "black-cheeked falcon". It is found in Australia in all regions except the southwest, where replaced by F. p. submelanogenys; some authorities treat the latter as a synonym of F. p. macropus. It is non-migratory. It is similar to F. p. brookei in appearance, but is slightly smaller and the ear region is entirely black. The feet are proportionally large.