[3] Swifts have very short legs which they use primarily for clinging to vertical surfaces (hence the German name Mauersegler, literally meaning "wall-glider").

They never settle voluntarily on the ground where they would be vulnerable to accidents and predation, and non-breeding individuals may spend up to ten months in continuous flight.

[4] The common swift was one of the many species described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae.

[5] The current genus Apus was erected by the Italian naturalist Giovanni Antonio Scopoli in 1777 based on tautonymy.

It is derived from the Ancient Greek α, a, "without", and πούς, pous, "foot", based on the belief that these birds were a form of swallow that lacked feet.

The purpose of these parties is uncertain, but may include ascending to sleep on the wing, while still breeding adults tend to spend the night in the nest.

[citation needed] Radar tracking of swifts at their breeding colonies has revealed that they often move together in flocks during their evening ascent and their dawn descent, but fly separately during the subsequent evening descent and the prior dawn ascent, suggesting that this flocking benefits the swifts via cue acquisition and information exchange between individuals or through extending social behaviour.

Insects such as clothes moths, carpet and larder beetles may consume all but the most indigestible nest elements, typically feather shafts[citation needed].

Young nesting swifts are able to survive for a few days without food by dropping their body temperature and metabolic rate, entering a torpid state.

[22][23][24][25] Subjects of a geolocator tracking study demonstrated that swifts breeding in Sweden winter in the Congo region of Africa.

[26] Swifts spend three to three-and-a-half months in Africa and a similar time breeding – the rest is spent on the wing, flying home or away.

The barn swallow and house martin hunt for airborne insects in a manner similar to that of the slightly larger swift, and occasionally mixed groups of the species form.

The most noticeable differences between the three types are: Swift nests commonly support populations of the chewing louse Dennyus hirundinis and the lousefly Crataerina pallida.

[28] The heraldic bird known as the "martlet", which is represented without feet, may have been based on the swift, but is generally assumed to refer to the house martin; it was used for the arms of younger sons, perhaps because it symbolized their landless wandering.