A rare swiftlet found very locally in the mountains and foothills. Fairly large swiftlet with a shallow forked tail, brown plumage and a paler throat. Feeds in flocks, possibly favouring lagoons and gullies. Roosts in caves, but some nocturnal activity suggested using clicking calls as a basic form of echolocation. Very difficult to ID with confidence. Similar to Mountain and Bare-legged Swiftlets, but Three-toed Swiftlet is bigger than Mountain and slimmer than Bare-legged, with a smaller head. Vocalizations are not well known.