Discription: Smallish (12 cm) swiftlet. Upperparts blackish brown with paler, greyish or brown rump in Java, or dark brown rump in Sumatra and Borneo (sub-species vestita); tail slightly forked; underparts brown. Generally indistinguishable in the field from Mossy-nest, Black-nest, and Volcano Swiftlets unless at nest. Iris - dark brown; bill - black; feet - black.
Description: Smallish (13 cm) blackish brown swiftlet with rump grading from greyish to the same colour as the back, and virtually indistinguishable in the field from the Edible-nest Swiftlet. Legs are well feathered; tail rather square-cut. Iris - brown; bill - black; feet - black.