Description wikipedia

The volcano swiftlet (Aerodramus vulcanorum or Collocalia vulcanorum) is a species of bird in the Apodidae family, formerly considered conspecific with the Himalayan swiftlet (Aerodramus brevirostris).The volcano swiftlet is commonly measured at 13–14 centimetres (5.1–5.5 in) long and characterized as dark gray with an unmissable brown rump band, whereas younger individuals show a less defined band. They can be easily heard because of the unique "Teeree teereeeee teeereeeee" clicking sound they make. Nothing is known about the diet of this bird. Many species of Aerodramus swiftlets nest colonially in caves, which leads them to use echolocation to navigate through the dark environments like caves and crevices, as well as during the twilight hours. While the swiftlet can echolocate like the very known species of the bat, they are much less educated and less refined in using it for capturing prey. This echolocation capability distinguishes Aerodramus from closely related genera like Hydrochous and most species within Collocalia.