IDENTIFICATION

VOCALISATIONS

A high-pitched modulated scream can be heard from birds in flight.

DISTRIBUTION & HABITAT PREFERENCE

Migrant pacificus are recorded most often over fish ponds, especially in the Deep Bay area, and occasionally over hillsides and mountains. Summering kurodae breed on the offshore islands of Waglan and the Ninepins and have been noted from widespread upland and coastal areas in the eastern New Territories and southern parts of HK Island.

OCCURRENCE

A. p. pacificus has been recorded in all months of the year but occurs mainly as a passage migrant between the end of January and the end of May. Rare in January and scarce in February, most spring migration takes place between the third week of March and the end of May, with a clear peak during the first week of April (Figure 1). It is less common during autumn migration with most records occurring in September. There are few records after the second week of October.

A. p. pacificus was previously much commoner, especially during spring when flocks of 500 or more were fairly regular in late March and early April. The highest single-site count was 3,000 at Mai Po on 4 April 1987. Figure 2 shows how peak weekly numbers fell after 1996, and triple-figure weekly counts have not occurred since 1997. The highest single-site count since 1998 is 80 at Po Toi on 18 March 2010. The reason for this decline is unclear, although Welch et al. (2016) speculate it might be due to changes in fish pond management or changes in habitat area of quality outside HK.

A. p. kurodae is a summer visitor in small numbers to rocky cliff-faces on the small islands of Waglan and the Ninepins in southeastern waters. However, because of their relative remoteness, the islands receive rather limited observer coverage. On Waglan, nesting was thought to have taken place in summer 1958 and 50 were present there on 23 June 1995. At the Ninepins, at least 12 birds were present on 15 June 1980, 200 were there on 2 May 1993 when nest-building was noted, and 100 were noted on 22 June 1995. More recently, up to 80 were noted at the Ninepins in June 2003 and up to 36 were at Waglan in July 2011. During the Breeding Bird Survey 2016-2019, an abundance rating of 14-37 birds was made at Waglan but no more than nine were counted in the Ninepins group.

Noted in summer in the Pearl River delta by Kershaw (1904), Pacific Swift was first recorded in HK by Vaughan and Jones (1913) who described it as a summer visitor between late March and early September, with main arrival in spring though ‘the greater number of birds pass on to regions further north’. Subsequently, it was only infrequently reported between early spring and late summer in the 1930s (Hutson 1931, Herklots 1935). In the mid-1950s, however, Walker (1958) noted it between 18 February and 12 November and considered that ‘immense numbers must pass through each spring’.

BREEDING

Nests in fissures in rocky cliffs on small islands. Nest building has been noted at Waglan and the Ninepins in summer but difficulty of access means that there is no further local information available.

BEHAVIOUR, FORAGING & DIET

An aerial feeder preying almost exclusively on insects. Forages over open areas, hillsides and mountain tops. Migrants are recorded most often over fish ponds with House Swifts, particularly in overcast conditions when they may fly low over the water.

RANGE & SYSTEMATICS

A. p. pacificus breeds in Siberia east to Kamchatka, north China and Japan; it winters to Indonesia, Melanesia and Australia. In China, it breeds in Inner Mongolia and Hebei south to Jiangsu and west to Sichuan (Liu and Chen 2020). A. p. kurodae breeds in eastern China south to Guangdong, southern Japan, Taiwan and the northern Philippines; it winters to Malaysia, Indonesia and the Philippines (Chantler et al. 2020). In China its status west of here, particularly in western Guangdong and eastern Guangxi, is obscured by the presence of Cook’s Swift A. cooki.

Previously considered conspecific with Salim Ali’s Swift A. salimali, Blyth’s Swift A. leuconyx and Cook’s Swift, Pacific Swift occurs in East Eurasia, the Oriental region, and Australasia. Two subspecies are recognised by the IOC: A. p. pacificus and A. p. kanoi. However, the HKBWS Records Committee follows Leader (2011) in treating A. p. kanoi as A. p. kurodae. Both the nominate form and A. p. kurodae occur in HK.

CONSERVATION STATUS

IUCN: Least Concern. Population trend stable.