The blue swallow (Hirundo atrocaerulea) is a small bird within the swallow family which is in the order Passeriformes. Swallows are somewhat similar in habits and appearance to other aerial insectivores, such as the martins (also a passerine) and the swifts (order Apodiformes). It breeds in the Afromontane (from South Africa to Tanzania), wintering north of Lake Victoria.
This bird breeds in montane grassland, preferring high rainfall, undulating areas. In winter it prefers open grassland, with bushes and trees. The nest is usually attached to the roof or side of a hole in the ground.
This species is a small swallow at 18–25 centimetres. The adult birds have a highly lustrous dark metallic steel-blue appearance with long tail streamers, which are particularly noticeable in males. White feathers are visible on the rump and flanks when the birds are preening and especially during courtship. In poor light, blue swallows appear almost black and therefore can be mistaken for black saw-wing swallows (Psalidoprocne spp.) which occur throughout its breeding range. Young blue swallows start life a brownish-grey, acquiring their blue colour as they mature. This species has a musical "bee-bee-bee-bee" call when in flight.