Peregrine falcon

The peregrine falcon (Falco peregrinus), also known simply as the peregrine, is a cosmopolitan bird of prey (raptor) in the family Falconidae renowned 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, it 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 landmass from which it is entirely absent is New Zealand. This makes 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 owes its success to human-led introduction; the domestic and feral pigeons are both domesticated forms of the rock dove, a major prey species for Eurasian peregrine populations. Due to their abundance over most other bird species in cities, 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 this 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. The genetic differential between them (and also the difference in their appearance) is very small, only about 0.6–0.8% genetically differentiated, showing the divergence is relatively recent, during the time of the Last Ice Age; all the 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 certain 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 multiple eras and areas of human civilization.

The peregrine falcon has a body length of 34 to 58 cm (13–23 in) and a wingspan from 74 to 120 cm (29–47 in). 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 330 to 1,000 g (12–35 oz) and the noticeably larger females weigh 700 to 1,500 g (25–53 oz). In most subspecies, males weigh less than 700 g (25 oz) and females weigh more than 800 g (28 oz), 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 26.5 to 39 cm (10.4–15.4 in), the tail measures 13 to 19 cm (5.1–7.5 in) and the tarsus measures 4.5 to 5.6 cm (1.8–2.2 in).

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.

A study shows that their black malar stripe exists to reduce glare from solar radiation, allowing them to see better. Photos from The Macaulay Library and iNaturalist showed that the malar stripe is thicker where there is more solar radiation. That supports the solar glare hypothesis.