An acrobatic, swift-like raptor with angular wings and a massive gape; capable of snatching prey from the air and devouring it in a flash while still on the wing. Dark with varying amounts of white on the underside; African birds have patchy white throughout the underparts, while white is restricted to the throat and lower belly on New Guinean birds and solely to the throat in Southeast Asian birds. Inactive during the day; hunts at dawn and dusk, and occasionally into the night if light is sufficient. Generally uncommon and localized, most reliably encountered near large bat roosts in forested areas, but can also be seen over open forest, fields, and fringes of habitation.