Abstract :
The Atiu Swiftlet Aerodramus sawtelli is endemic to the Cook Island of Atiu and has an
estimated total population of less than 400, rendering it one of the world’s most globally
endangered bird species. Over a series of five visits to Atiu, we collected data on the distribution
of foraging swiftlets on the island, and their foraging and echolocation behaviour. The bird
favours forests, agriculturally developed areas such as croplands, and populated sections of the
island (e.g. gardens) but avoids the dry, upraised coral ring (makatea) of Atiu. It appears able to
readily exploit new insects after they have immigrated to Atiu and may act as a natural control
agent on pest species (e.g. Xyleborus perforans and Atrichopogon jacobsoni). We reanalysed the
swiftlets’ echolocation calls within one of their roost caves in conjunction with new recordings.
The calls do not contain ultrasonic components and are uniquely single clicks compared to the
echolocation vocalisations of other swiftlet species. The minimal impact of human disturbance on
the remote nesting caves of this bird suggests that its numbers, although small, represent
a stable population
