Generic-looking “white-bellied swiftlet”, but fortunately the only regular one on Christmas Island; migratory House and Pacific Swifts are larger, with bright white rump patches. Note the pale belly, dusky throat, weakly forked tail, and glossy dark upperparts, all traits typical of the genus Collocalia. Forages in swift, bat-like flight above a range of habitats on Christmas Island, sometimes forming loose flocks.