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 (raptor) in the family Falconidae. A large, crow-sized falcon, it has a blue-grey back, barred white underparts, and a black head. The peregrine is renowned for its speed. It can reach over 320 km/h (200 mph) during its characteristic hunting stoop (high-speed dive), making it the fastest member of the animal kingdom. According to a National Geographic TV program, the highest measured speed of a peregrine falcon is 389 km/h (242 mph). As is typical for bird-eating (avivore) raptors, peregrine falcons are sexually dimorphic, with females being considerably larger than males.
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 raptorand one of the most widely found bird species. In fact, the only land-based bird species found over a larger geographic area is not always naturally occurring, but one widely introduced by humans, the rock pigeon, which in turn now supports many peregrine populations as a prey species.
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. Experts recognize 17 to 19 subspecies, which vary in appearance and range; disagreement exists over whether the distinctive Barbary falcon is represented by two subspecies of Falco peregrinus or is a separate species, F. pelegrinoides. The two species' divergence is relatively recent, during the time of the last ice age, therefore the genetic differential between them (and also the difference in their appearance) is relatively tiny. They are only about 0.6–0.8% genetically differentiated.
