Swiftlet

Swiftlets are notoriously difficult at a distance. There are 5 species possible here but Bornean is a montane species so unlikely..<br>
Glossy has a whitish mid-belly and glossy deep blue upperparts which cannot be seen from this angle and an almost square tail.<br>
Black-nest has pale throat and belly with a central darker patch, a whitish rump and almost square tail. The nest is dark grey.<br>
Edible-nest has a plain brown underside, a barely noticeable pale rump patch and a well-notched tail. The nest is white.<br>
Mossy-nest is overall dark with a pale underside and a slightly notched tail. The nest is a mossy green/brown with almost golden spots near the top.<br>
The latter 3 are best separated by their nests and location around areas where there are large caves though they probably range far and wide.