The Atiu swiftlet (Aerodramus sawtelli), is a species of swift in the Apodidae family. It is endemic to Atiu in the Cook Island. This small, dark swift measures 10 cm (3.9 in) long. It is sooty-brown above, slightly lighter below. Its natural habitats are the island's fernlands and mixed horticultural areas over which it feeds, and in makatea limestone caves within which it nests. The species is known on Atiu as kopeka.