From Opus

Genus: Collocalia

[edit] Description

A genus with 3 small Swiftlets from South-east Asia. All have glossy black upperparts, square tails and mottled brownish underparts. All three are thought to be not able to do echolocation.

[edit] Taxonomy

Collocalia is a genus in the Family Apodidae. Together with Hydrochous, Aerodramus and Schoutedenapus this genus belongs to the subfamily Collocaliini. Some authorities still merge most or all Aerodramus species under Collocalia.
The relationships of the different Swiftlets are still poorly understood and can be called a taxonomist's nightmare. Further study is needed and will doubtless lead to new species, subspecies or lumping of some taxa.