Common swifts are medium-sized aerial birds known for their superb flying ability. They are entirely blackish-brown in color except for a small white or pale grey patch on their chins which is not visible from a distance. They have a short forked tail and very long swept-back wings that resemble a crescent or a boomerang. These birds 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.
The summer breeding range of Common swifts runs from Portugal and Ireland in the West across to China and Siberia in the East. They breed as far south as Northern Africa (in Morocco and Algeria), with a presence in the Middle East in Israel, Lebanon and Syria, the Near East across Turkey, and the whole of Europe as far north as Norway, Finland, and most of sub-Arctic Russia. Common swifts migrate to Africa, ending up in Equatorial and Sub-Equatorial Africa, excluding the Cape. These birds inhabit a wide range of habitats; these include arid steppe, grassland, savanna, desert, shrubland, rainforests, and wetlands. They can also be found around villages and towns.
Common swifts are highly gregarious birds; they roost, nest, migrate, and hunt in groups. Except when nesting, swifts spend their lives in the air, living on the insects caught in flight; they drink, feed, and sleep on the wing. Some individuals go 10 months without landing. No other bird spends as much of its life in flight. Over a lifetime they can cover millions of kilometers. Common swifts are far-distance migrants. They 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. Unsuccessful breeders, fledglings, and reproductively immature year-old birds are the first to leave their breeding area. Breeding males follow next, and finally the breeding females as they stay longer in the nest to rebuild their fat reserves. In order to communicate with each other Common swifts give loud screams. They often form 'screaming parties' during summer evenings, when 10-20 swifts will gather in flight around their nesting area, calling out and being answered by nesting swifts. Larger 'screaming parties' are formed at higher altitudes, especially late in the breeding season. 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.
Common swifts are monogamous. They form pairs that may remain together for years and often return to the same nesting site year after year. The breeding season occurs in spring, generally from March to June according to the range. Common swifts build their nests of air-borne material caught in flight, bonded with their saliva, in suitable buildings hollows, such as under tiles, in gaps beneath window sills, and most typically under eaves and within gables. The female lays 1-4 white eggs and both adults share the incubation during 19-20 days. The chicks hatch altricial; they are blind and naked and brooded continuously in the first week. The nestlings usually fledge between 37-56 days and become reproductively mature at 2 years of age.
Common swifts are widespread and abundant and are not considered globally threatened. However, the population of these birds is declining due to the loss of suitable nest sites through building renovation and due to declines in the numbers of their insect prey.
According to the IUCN Red List, the total Common swift population size is around 95,000,000-164,999,999 mature individuals. The European population consists of 19,100,000-32,500,000 pairs, which equates to 38,200,000-65,000,000 mature individuals. Overall, currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.