A medium-sized swiftlet with a relatively long forked tail. Mostly brown with very slightly paler brown underparts and a more golden-brown rump and collar. Most common over rocky riverine valleys and humid forests. Similar to Atiu Swiftlet but is less contrastingly patterned, overall more uniformly brown, with a paler rump and a proportionally longer tail. Also extremely similar to Polynesian Swiftlet, but appears darker-faced and more obviously golden-collared. Vocally similar to Polynesian Swiftlet, with a voice consisting of insect-like buzzing and trilling.