[1] The back and upper surface of the wings are dull dark blue with a moderate green gloss.

The rump is paler due to the white margins of feathers forming the uppertail coverts.

There is sometimes a tuft of small feathers on the hallux, the rear facing toe.

[2] The grey-rumped swiftlet was described by the Italian ornithologist Tommaso Salvadori in 1882 and given the current binomial name Collocalia marginata.

Seen in almost any habitat including coastal areas, montane forest , agricultural lands and even roads.