HIMALAYAN SWIFTLET Aerodramus brevirostris 短嘴金絲燕
Category I. Scarce but increasing, passage migrant and winter visitor.
IDENTIFICATION
Dec. 2020, Michelle and Peter Wong.
13-14 cm. Sexes alike. Slightly smaller than House Swift with more fluttering flight. Wings blunt-tipped and tail slightly notched when closed. Plumage features subtle and apparent colour varies depending on the light.
Typical A. b. innominatus has blackish-brown upperparts contrasting with a paler grey-brown rump. The dark crown contrasts with paler grey-brown nape giving a capped appearance, and there is a dark area around eye.
Dec. 2020, Michelle and Peter Wong.
Underparts paler grey-brown than the upperparts. Dark underwing coverts contrast with paler flight feathers and dark undertail coverts have pale scales.
Most records of swiftlets in HK are considered to be A. b. innominatus on the above characteristics. Dark-rumped birds are occasionally reported but are currently regarded as within the variation of Himalayan Swiftlet: Chantler & Boesman (2020) state that “rump colour varies within populations of innominatus” and refer to “dark-rumped” birds”.
VOCALISATIONS
Appears to be silent away from breeding grounds.
DISTRIBUTION & HABITAT PREFERENCE
Although most records are from wetland and open country areas in the northwest New Territories, there are widespread sightings elsewhere, including the central and eastern New Territories, Po Toi, Lantau , Cheung Chau and HK Island.
OCCURRENCE
First recorded in HK in 1994, Himalayan Swiftlet remained rare until 2009 with no more than three records a year and several blank years. All records from 1994 to 2008 were in the period January to May apart from the first autumn report in September 2007. Numbers increased slightly in 2009 and 2010, when more birds were noted on autumn passage.
There was a further change in its status from 2014 when annual totals were generally in low double-digits and there was a small but obvious spring passage in April-May and a more pronounced autumn passage during late August-October, with a smaller influx of birds in December and January (Figure 1). The total number of birds per annum increased to 28 in 2019 and 57 in 2020; 45 of the 2020 birds occurred in September and October during an unprecedented autumn movement of this species through HK.
BEHAVIOUR, FORAGING AND DIET
Often solitary in HK, although sometimes associates with other swifts and hirundines over wetland areas, particularly fish ponds. No local information on diet, although presumed to feed largely on Diptera and Hymenoptera.
RANGE & SYSTEMATICS
Breeds from the Himalayas east to central China, south to Myanmar, northern Thailand and southwest China. Winters south to Bangladesh and the Malay Peninsula. Three subspecies are recognised.
A. b. innominatus breeds in China (Hubei, south Sichuan, north Guizhou and Yunnan) and winters to southwest Thailand and the Malay Peninsula. There are regular records of non-breeding birds from south China, including HK, and north Vietnam, and it has strayed to eastern China, Taiwan, South Korea and Japan. A. b. brevirostris breeds in the Himalayas and mountains of north India east to southwest China (west Yunnan), Myanmar and Thailand, and winters to Bangladesh, southwest Thailand and the Malay Peninsula. A. b. rogersi breeds in east Myanmar and west Thailand, and winters south to south Thailand (Chantler et al. 2020).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Figure 1.
Chantler, P., G. M. Kirwan, and P. F. D. Boesman (2020). Himalayan Swiftlet (Aerodramus brevirostris), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.himswi2.01
