Justification of Red List Category
This poorly known swift qualifies as Vulnerable owing to its very small known population. Discovery of new breeding colonies or identification of possible threats would necessitate a reassessment of its threat status.
The population is thought to lie within the range 250-999 individuals, based on estimates of breeding colony sizes ranging from a few to 200 individuals. This estimate roughly equates to 167-666 mature individuals, but the population is probably unlikely to be at the lowest end of this range. A provisional population estimate of 250-700 mature individuals is therefore given.
The population is suspected to be stable in the absence of evidence for any declines or substantial threats. This is supported by observations: records at its known sites have remained stable for many years, for example at Cherrapunji (J. Eaton in litt. 2013).
Apus acuticauda is known from just a few breeding colonies in the Himalayan foothills in Bhutan, and the hills of Meghalaya, Nagaland and Mizoram, north-eastern India (BirdLife International 2001, Chantler 2005, Ahmed et al. 2007, K. D. Bishop in litt. 2013, J. Eaton in litt. 2013, M. Sharma in litt. 2013). Its seasonal movements and wintering areas are virtually unknown. There are records throughout the year from India and during the non-breeding season from north-western Thailand and Yunnan, China (J. Hornskov in litt. 2005). There are unconfirmed reports of the species from Myanmar (per J. W. Duckworth in litt. 2013). At known breeding colonies, the number of birds ranges from a few to more than 250 (C. Robson in litt. 2013), and the total population may not exceed 1,000 individuals.
It breeds colonially in the crevices of rocky cliffs and deep gorges, at 200-1,350 m, generally in the vicinity of forest. Breeding is from March to May usually at the same site each year. Birds apparently remain in close proximity to the nesting colonies while breeding, normally disappearing soon afterwards and reappearing the following year. Away from breeding sites, it has been recorded up to at least 1,500 m. It has been suggested that it may only undertake local movements, but this requires further investigation.
There are no known threats, although its reliance on forest as a feeding habitat should be investigated.
Conservation Actions Underway
A presumed breeding site is located within the Blue Mountain National Park, Mizoram, north-eastern India. Strict forest policy and wildlife protection laws in Bhutan suggest that its future there is secure.
17-18 cm. Slim, all-dark swift with scaly underside and deeply forked tail. Tends to have dark throat. Similar spp. Fork-tailed Swift A. pacificus has white rump-band, less sharply forked tail and paler throat. Common Swift A. apus lacks scaling to underparts and has shorter, less deeply forked tail. Voice High-pitched, rapid, quavering tsrr'i'i'i'i and tsrr'i'i'i'i'is'it at nest-sites.
Text account compilers
Peet, N., Allinson, T, Davidson, P., Bird, J., Tobias, J., Westrip, J., Taylor, J.
Sharma, M., Hornskov, J., Robson, C., Duckworth, J.W., Mahood, S., Ahmed, F, Bishop, K.D., Eaton, J.
BirdLife International (2019) Species factsheet: Apus acuticauda. Downloaded from http://www.birdlife.org on 17/11/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/11/2019.