Зондская салангана Aerodramus salangana

One of a number of essentially identical-looking small swifts. Best identified by its nest, made up of dried moss and other scraps of vegetation; compare with the dark nest of Black-nest Swiftlet and white nest of Edible-nest Swiftlet, with which it often shares its breeding caves. Often flies in large flocks over forests and waterways; mixes with other swiftlets.