Aerodramus

Aerodramus is a genus of small, dark-plumaged, cave-nesting swiftlets confined to tropical and subtropical regions of southern Asia, Oceania, and northeastern Australia. Many species were formerly classified within the genus Collocalia before American ornithologist Harry Church Oberholser separated Aerodramus as a distinct genus in 1906. The group is taxonomically difficult, with very similar-looking species distinguished using echolocation calls, DNA sequencing, and even parasitic lice, though some relationships remain unresolved. Aerodramus swiftlets are among the very few birds capable of echolocation, using simple clicking calls to navigate the total darkness of their nesting caves. Their nests are built largely or, in two species, entirely from hardened saliva, which is harvested for the Chinese delicacy bird's nest soup, a trade that places significant pressure on wild populations.