This species is very similar to the common swift but can be distinguished under optimum viewing conditions by the contrast between its black back and paler secondary wing feathers.

This species feeds readily over lowland, and can form very large flocks, often with other gregarious swifts.

Two other dark races, A. b. balstoni and A. b. mayottensis (see: Malagasy black swift), are restricted to Madagascar and the Comoro Islands respectively.

East African birds nest in hollow trees, whereas in South Africa this species uses cliffs, usually inland but also on the coast.

The nest is a shallow grass cup glued to the substrate with saliva, and the typical clutch is one or two eggs.