The Mountain Swiftlet occurs on New Guinea. It flies in flocks over highland forests, catches insects in the air and breeds colonially in caves.
It is about 12 cm long, with uniform dark-brown upperparts, pale-grey underparts and a moderately forked tail.
It prefers highland forest and occurs up to about 4,000 m. It is highly gregarious, sometimes with other swifts, and catches insects in flight. Colonies nest in caves, using moss, ferns and grass in bulky nests.
It normally lays a single egg in its cave nest.
Its tarsi are feathered, and its bill is tiny and downcurved.
An extinction-risk assessment has not been added yet.