Swifts have erratic, fluttering flight patterns and are known for their acrobatic aerial displays, being able to turn sharply mid-flight by varying the speed at which they beat their wings (7). Swifts are closely related to hummingbirds (2), and both groups share a unique wing structure that allows them to perform intricate manoeuvres during flight (7).
In general, swifts are opportunistic hunters, feeding mainly on invertebrates, particularly insects and spiders, caught during flight. Swifts will exploit a variety of food sources, including swarms and even beehives when available (2).
The abundance of prey has a significant impact on the breeding biology of swifts, and for most species the timing of breeding typically coincides with the wet season in the tropics and summer in the temperate zone (8). On the Canary Islands, the breeding season of the plain swift is fairly long, usually beginning around March and continuing until August or September (8). The plain swift is a colonial breeder, typically nesting with other individuals in caves or fissures in cliffs (5). The clutch of the plain swift consists of two white eggs, and this species usually produces two broods during a single breeding season (3). As in other swift species, it is likely that both the male and female take turns to incubate the eggs (2).
Except for the population on Madeira, which tends to remain resident all year round, the plain swift will migrate from the breeding grounds around September to mid-October. This species is presumed to overwinter in Africa, although the exact locations of wintering sites are unknown. The plain swift returns to the breeding grounds between January and March (3).