A small dark brown swift with an indistinctly paler gray rump. Underparts are lighter brown than upperparts. A gregarious aerial species, found in flocks, often with other swiftlet species, over a wide variety of open and forested habitats at varied elevations. Limited to the north Moluccas. Marginally smaller than Uniform Swiftlet, and shows a neatly defined, subtly paler rump. In certain lights, Uniform Swiftlet can appear to have a pale rump, but it usually appears to cover a broader area.