Falcons (/ˈfɒlkən, ˈfɔːl-, ˈfæl-/) are birds of prey in the genus Falco, which includes about 40 species. Some small species of falcons with long, narrow wings are called hobbies, and some that hover while hunting are called kestrels. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene.
Adult falcons have thin, tapered wings, which enable them to fly at high speed and change direction rapidly. Fledgling falcons, in their first year of flying, have longer flight feathers, which make their configuration more like that of a general-purpose bird such as a broadwing. This makes flying easier while still learning the aerial skills required to be effective hunters like the adults.
The falcons are the largest genus in the Falconinae subfamily of Falconidae, which also includes two other subfamilies comprising caracaras and a few other species of "falcons". All these birds kill prey with their beaks, using a tomial "tooth" on the side of their beaks — unlike the hawks, eagles and other larger birds of prey from the unrelated family Accipitridae, who use talons on their feet.
The largest falcon is the gyrfalcon at up to 65 cm (26 in) in length. The smallest falcon species is the pygmy falcon, which measures just 20 cm (7.9 in). As with hawks and owls, falcons exhibit sexual dimorphism, with the females typically larger than the males, thus allowing a wider range of prey species.
As is the case with many birds of prey, falcons have exceptional powers of vision; the visual acuity of one species has been measured at 2.6 times that of human eyes.They are incredibly fast fliers, with the Peregrine falcons having been recorded diving at speeds of 320 km/h (200 mph), making them the fastest-moving creatures on Earth; the fastest recorded dive attained a vertical speed of 390 km/h (240 mph).
The genus Falco was introduced in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae. The type species is the merlin (Falco columbarius). The genus name Falco is Late Latin meaning a "falcon" from falx, falcis, meaning "a sickle", referring to the claws of the bird. In Middle English and Old French, the title faucon refers generically to several captive raptor species.
The traditional term for a male falcon is tercel (British spelling) or tiercel (American spelling), from the Latin tertius (third) because of the belief that only one in three eggs hatched a male bird. Some sources give the etymology as deriving from the fact that a male falcon is about one-third smaller than a female (Old French: tiercelet). A falcon chick, especially one reared for falconry, still in its downy stage, is known as an eyas (sometimes spelled eyass). The word arose by mistaken division of Old French un niais, from Latin presumed nidiscus (nestling) from nidus (nest). The technique of hunting with trained captive birds of prey is known as falconry.
Compared to other birds of prey, the fossil record of the falcons is not well distributed in time. For years, the oldest fossils tentatively assigned to this genus were from the Late Miocene, less than 10 million years ago. This coincides with a period in which many modern genera of birds became recognizable in the fossil record. As of 2021, the oldest falconid fossil is estimated to be 55 million years old.Given the distribution of fossil and living Falco taxa, falcons are probably of North American, African, or possibly Middle Eastern or European origin. Falcons are not closely related to other birds of prey, and their nearest relatives are parrots and songbirds.