Atiu Swiftlet Aerodramus sawtelli Scientific name definitions

10 cm. Small to medium-sized swiftlet with relatively long, forked tail ; black-brown upperparts with contrastingly pale grey rump; pale grey-brown underparts appearing darkest on undertail-coverts; pale supraloral patch reduced or missing. Separable from A. leucophaeus leucophaeus by smaller size, shorter tail, paler bases to uppertail-coverts, paler underparts and different bill structure; A. l. ocistus somewhat intermediate. Capable of echolocation.

Atiu I (S Cook Is).

Occurs over both open and forested habitats (1 Tarburton, M.K. (1990). Breeding biology of the Atiu Swiftlet. Emu. 90(3): 175-179. Close ); favours forests, agriculturally developed areas such as croplands, and populated sections of the island (e.g. gardens) but avoids the dry, upraised coral ring of the island (2 Fullard, J.H., Barclay, R.M.R. and Thomas, D.W. (2010). Observations on the behavioural ecology of the Atiu Swiftlet Aerodramus sawtelli. Bird Conservation International. 20(4): 385–391. Close ).

Resident.

Little known. In a faecal analysis, all of the identifiable fragments were the remains of insects except for occasional feather fragments, while in pellets only beetles (Coleoptera) and flies (Diptera) were identified; fragments of the island pinhole borer beetle Xyleborus perforans, a pest species, were present in c. 75% of all pellets analysed (2 Fullard, J.H., Barclay, R.M.R. and Thomas, D.W. (2010). Observations on the behavioural ecology of the Atiu Swiftlet Aerodramus sawtelli. Bird Conservation International. 20(4): 385–391. Close ). Forages slowly amidst forest canopy and along forest margins. 

Uses echolocation inside nesting caves, by emitting repeated high-bandwidth clicks at a rate of 4–14 clicks per second, producing a rattling “tic-tic-tic-tic-tic...”; it differs from other swiftlets in that it emits exclusively single rather than double clicks (3 Fullard, J.H., Barclay, R.M.R. and Thomas, D.W. (1993). Echolocation in free-flying Atiu Swiftlets (Aerodramus sawtelli). Biotropica. 25(3): 334-339. Close ).

Most nests built Sept with last chicks fledged Apr. Colonial cave breeder . Nest typically bracket-and-cup-shaped and self-supporting using a small quantity of saliva, though those on ledges had cups supported upon a base. Nest composed primarily of plant material, mostly coconut crown fibre and lichens with lesser quantities of Casuarina needles, grass, angiosperm leaves and passion-fruit (Passiflora) tendrils; other components include feathers from this species and less commonly its own eggshells and flowers of Ocimum gratissimum. Two eggs, both sexes incubating; sometimes 2 broods. Average weight of young 1·1 g at hatching and 9·5 g when they fledge; fledging period averages 53 days.

VULNERABLE. Restricted-range species: present in Southern Cook Islands EBA. No decline apparent to date. There were thought to be only 60 nests when species was first discovered in 1973. Census in 1987–1988 recorded 190 active nests in two caves; in addition, other smaller colonies are believed to exist. Recent studies show density of 1 breeding bird per 7 ha, equivalent to total of 380 breeding birds on the island. Crab predation and starvation after falling from nest are main causes of fledgling mortality. Tourist disturbance may pose future problem.