A small brown-black swallow with a short tail and comparatively weak flight. The forehead, crown, and back of the neck are dull chestnut with faint dark streaks. The back is glossy deep blue with a few narrow whitish streaks; the rump is pale brown and is more prominent in flight. The wings and tail are blackish-brown, and the tail almost square-ended. Underparts are buffy white with blackish-brown streaks, especially the chin, throat, and upper breast. Juvenile is duller and browner than adult, with buff feather edges and faint streaks on underparts. Found mostly as individuals in mixed swallow flocks; different, weaker flight action is characteristic.