Mariana swiftlet

The Mariana swiftlet, also called the Guam swiftlet, Aerodramus bartschi, is a small species of swiftlet in the family Apodidae. It was formerly lumped with the island swiftlet. The bird is about 11 centimetres long, with a dark grey-brown head and upperparts, a grey-white throat and upper breast, darker grey underparts and a shallow forked tail without gloss. It lives on Guam, Saipan and Aguijan in the Northern Mariana Islands, is locally extinct on Rota and Tinian, and was introduced to Oahu in the early 1960s, where the population is small. Its habitats are tropical moist lowland forest, mangrove forest and grassland. It nests in colonies on the walls and ceilings of limestone caves, even in total darkness, lays a single egg, navigates with echolocation clicks and catches small insects in flight. It is considered Vulnerable, and predation by brown tree snakes and agricultural pesticides drove the decline on Guam.