Asian House Martin Delichon dasypus 煙腹毛腳燕
Category I. Uncommon passage migrant in autumn, scarce to uncommon in spring and scarce in winter; occurs over a variety of habitats at all altitudes. Numbers have declined, particularly in spring. Two subspecies occur, nominate dasypus and D. d. nigrimentale.
IDENTIFICATION
Mar. 2016, Kinni Ho. D. d. dasypus.
12-13 cm. Compact, fairly stocky hirundine with shallow tail fork. Dark above, blue-toned on mantle, back and scapulars, contrasting with white underparts and rump. Forages aerially, often perches on wires.
Two subspecies occur, which can be distinguished in the field. The more northerly nominate subspecies (illustrated) is slightly larger, has cleaner white plumage and is thus more contrasting and a larger rump patch.
Jan. 2024, Paul Leader. D. d. nigrimentale.
Asian House Martin differs from Siberian House Martin in having extremely dark underwing coverts and black that extends lower on the ear coverts and often narrowly below the bill. The dusky underparts of this bird suggest it is the southerly breeding taxon nigrimentale.
Mar. 2016, Kinni Ho. D. d. nigrimentale.
Asian House Martin also has a smaller slightly less pure white rump patch that does not include the uppertail coverts and a dusky-grey wash to the flanks that may extend across the chest and highlight the white throat.
The southerly breeding subspecies nigrimentale is smaller than nominate dasypus with a smaller rump patch, more dark on the head and less white on the underparts.
VOCALISATIONS
In separating the two taxa using flight call, it is important that the same type of utterance is compared, one that is given without any obvious stress or excitement.
The relaxed flight call of dasypus is monosyllabic and sometimes rises in pitch.
The relaxed flight call of nigrimentale is flatter in tone, lower in pitch overall and disyllabic with the second syllable higher in pitch.
DISTRIBUTION & HABITAT PREFERENCE
This species forages over fish ponds, marshes, open agricultural areas, wooded hillsides, mountain tops and forests. Most records are from the Deep Bay area, but it is widespread on passage and in winter, and has also been recorded in the central and eastern New Territories, on HK Island, Lantau, Cheung Chau and Po Toi.
OCCURRENCE
Asian House Martins are recorded from the first week of October to the end of April, with the earliest and latest dates being18 September 1978 and a bird photographed on 24 May 2010, the latter two weeks later than the next latest. Since 1999 highest numbers have occurred in autumn from the second week of November to mid-December; in spring numbers are lower, with most recorded in the first three weeks of March (Figure 1).
This pattern stands in contrast to the period to 1998 when strongest passage by far occurred in March and the first week of April (Figure 1). There has also been a substantial decline in the numbers recorded in spring, with the peak count since 1999 being 40 on 10 March 2009; in contrast, from 1986 to 1998 counts greater than this figure occurred on average every other year, while peak weekly aggregate counts reached 403 in the first week of March 1992 and 683 in the first week of April 1996 (including 400 at several sites in the Deep Bay area on 4 April 1996, the highest single day count on record).
Up to 1998 Asian House Martin was considered irregular in autumn from the second half of September to late November, the peak count being 100 at Ho Chung on 8 November 1992. Since 1999 the peak count is also 100, on 17 November 2009 and 9 December 2012. In 1990 and 1995 there were counts of up to 20 birds in the second half of September; in contrast the earliest date since 1999 is 1 October. It is likely that some autumn records prior to 2009 referred to Siberian House Martin, which has been recorded since, albeit in low numbers.
Occasional records from mid-December to February usually involve small flocks of up to six, the highest count in this period being 20 at Tung Chung on 26 December 1984 and 23 January 2016.
In the 1950s it was noted in small numbers on a total of 11 dates during February-April and November-December (Dove and Goodhart 1953, Walker 1958). A report of ‘large numbers’ at Happy Valley on 16 March 1907 (Vaughan and Jones 1913) was the first for HK.
Based on measurements given by Vaurie (1959), 30 birds trapped on 7 March 1992 and 4 April 1996 were D. d. dasypus, while three trapped on 7 March 1992 were D. d. nigrimentale. Field observations support this reflection of the relative proportions of the two taxa.
BEHAVIOUR, FORAGING & DIET
An aerial insectivore but no details. The largest numbers are often noted following surges of the northeast monsoon, particularly when cloudy or rainy weather causes birds to temporarily remain, awaiting an improvement in the weather.
RANGE & SYSTEMATICS
Discrete breeding populations occur in the Himalayas to central north China, south central Siberia in the area of Lake Baikal, Ussuriland, northeast China, the Korean peninsula, Japan and southeast China; winters from northeast parts of the Indian subcontinent east through Indochina to southwest China and south through southeast Asia to the Greater Sundas (Turner 2020). In China breeds from southeast Tibet northeast to Beijing and eastern parts of the northeast, and south and east parts of the country (Liu and Chen 2020).
Three subspecies are recognised. The nominate form breeds from south central Siberia east to northeast China, the Korean peninsula and Japan; D. d. nigrimentale breeds in south and east China, including Taiwan; D. d. cashmeriense breeds from the Himalayas to west China. There is no evidence the latter taxon occurs here.
CONSERVATION STATUS
IUCN: Least Concern. Population trend increasing.
Figure 1.
Dove, R. S. and H. J. Goodhart (1955). Field observations from the Colony of Hong Kong. Ibis 97: 311-340.
Liu, Y. and Y. H. Chen (eds) (2020). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House, Changsha.
Turner, A. (2020). Asian House-Martin (Delichon dasypus), 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.ashmar1.01
Vaughan, R. E. and K. H. Jones (1913). The birds of Hong Kong, Macao and the West River or Si Kiang in South-East China, with special reference to their nidification and seasonal movements. Ibis 1913: 17-76, 163-201, 351-384.
Vaurie, C. (1959). The Birds of the Palearctic Fauna. A Systematic Reference. Order Passeriformes. H. F. & G. Witherby Ltd., London.
Walker, F. J. (1958). Field observations on birds in the Colony of Hong Kong. Hong Kong Bird Watching Society, Hong Kong (duplicated).
