Atiu swiftlet

The Atiu swiftlet or Sawtell's Swiftlet is a species of bird in the swift family, endemic to Atiu in the Cook Islands.
This small, dark swift measures 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.
Unlike all other swiftlets, it echolocates only through single clicks, rather than a mix of single- and double clicks.