Savanna Nightjar Caprimulgus affinis 林夜鷹
Category I. Locally common resident in grassland and open country, with some seasonal movements.
IDENTIFICATION
Apr. 2011, Martin Hale. Male.
20-26 cm. A medium-sized nightjar resembling Grey Nightjar in showing a large head, large eye, long tail, weak bill, short legs and variegated, cryptic plumage, but easily separated when vocalising. Seen in flight, its profile is more harrier-like than Grey Nightjar, with a shorter tail and broader blunter wings. Males have a conspicuous white patch across the four outermost primaries, and the outermost tail feathers are white, contrasting strongly with dark central tail feathers; on females the wing-tip patches are buffy and there is no obvious contrast between the edges and centre of the tail (Chalmers 1998).
May 2009, Martin Hale. Male.
Seen at rest, the tips of the primaries do not project beyond the tail and the plumage, though complex in pattern, is relatively uniform grey-brown and lightly (males) or more boldly (females) spotted with chestnut. Both sexes lack the heavy black centres to the crown, mantle and scapulars shown by Grey Nightjar (Hale 2002).
VOCALISATIONS
The territorial call is a loud piercing ‘chweep’ frequently repeated at intervals of 2-4 seconds. It can be heard in all months, though mainly February-May.
When foraging at close range, a quiet ‘chep’ can be heard.
DISTRIBUTION & HABITAT PREFERENCE
Savanna Nightjar is a lowland species not usually encountered above 300 metres asl. It is widespread throughout the year in the northern New Territories, where there is much suitable habitat in the form of fire-maintained grassland, open sparsely-vegetated land often on the edges of fish-ponds and poorly vegetated hillsides. It has also also been recorded throughout the year at three golf courses (Kau Sai Chau, Fanling and Discovery Bay). Elsewhere in the New Territories and on HK Island, Lantau and Lamma it is patchily distributed and occurs in areas of open-canopy shrubland and fire-damaged hillsides, mainly in the breeding season. There are also occasional records, all in winter or on passage dates, from urban Kowloon, Po Toi and Tung Ping Chau islands, and isolated records from other smaller islands such as Port Island and Shek Ngau Chau.
OCCURRENCE
Savanna Nightjar occurs throughout the year. Birds are far more active vocally (and hence much easier to detect) at the onset of the breeding season than they are later in the year (Figure 1). Vocalising birds account for over 90% of records in the months February-May compared to less than 30% in September-December. From a low in January, reports rise to a peak in the months of February to May (59% of the total) and decline to a trough in July, probably at least in part reflecting observer activity. Numbers in the second half of the year rise slightly but remain flat in August-September and then reach a peak in October-November (17%), reflecting the presence of migrants either of local origin or from further afield, after which the second trough of the year occurs in December, no doubt largely as a result of limited vocalising.
The highest counts on record in each season are from the golf course at the northern end of Kau Sai Chau island, with peak counts in autumn and winter (22 on 8 October 2000, 19 on 9 February 2001) higher than those in spring and summer (15 on 9 March 2001, seven on 26 June 2000). Largest numbers reported elsewhere are ten at Ping Yeung on 22 October 2004, 13 at the Lok Ma Chau Loop on 9 November 2009, and nine at Fung Kat Heung on 17 April 2020. A record of one at Shek Ngau Chau, a rocky islet with no suitable breeding habitat, on 12 August 2001 shows that some migration or dispersal occurs.
Though most nightjar records prior to the 1970s probably refer to Savanna Nightjar given that its preferred habitats dominated, no individuals were considered satisfactorily identified by Chalmers (1986) due to confusion with Grey Nightjar. The earliest reliably identified birds were two males found dead at the former Kai Tak airfield on 6 December 1974 (Chalmers 1998). Subsequently in the 1990s, Savanna Nightjar was considered to be an uncommon resident with possible autumn and winter movements occurring and a peak count of six at Chau Tau on 2 June 1984 and on 15 April 1992 (Carey et al. 2001).
BREEDING
Nesting records span dates of 20 April to 12 July, with dependent young present to at least 9 August, thus suggesting this species is at least double-brooded in HK. Four nests have been found, all with an adult sitting: on open sandy ground at the former Tin Shui Wai reclamation on 2 May 1994 (contents unknown) and 20 April 1996 (two eggs), on open stony ground at a grave-site on a small hill near Tin Shui Wai on 5 and 12 July 2008 (two eggs), with one or two chicks subsequently noted there between 18 July and 9 August, and on an open hillside at Luk Chau Au (Ma On Shan CP) on 31 May 2011 (two eggs).
BEHAVIOUR, FORAGING & DIET
Crepuscular and nocturnal, not usually encountered by day. Especially in the breeding season, males call frequently at dusk, in early evening and at dawn, either in slow flight about 5-30 metres above the ground, with the wings held in a shallow V and the white wing patches highly visible, or perched on the ground, a branch or a rooftop. Unlike other parts of the range where it can occasionally be heard by day, in HK it appears not to vocalise in the daytime.
RANGE & SYSTEMATICS
Breeds from northeast Pakistan through parts of south and southeast Asia to the Greater and Lesser Sundas, the Philippines and Sulawesi, and from north Vietnam to coastal provinces of south and southeast China and Taiwan and is largely resident except in the extreme west of its range where it is a summer visitor (Cleere & Nurney 1998, Cleere 1999, Liu and Chen 2020). Of eight subspecies recognised, amoyensis occurs in south and southeast China and northern Vietnam.
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Figure 1.
Chalmers, M. L. (1986). An Annotated Checklist of the Birds of Hong Kong. Hong Kong Bird Watching Society, Hong Kong.
Chalmers, M. L. (1998). Identification of Nightjars in Hong Kong. Hong Kong Bird Report 1996: 135-142.
Cleere, N. (1999). Family Caprimulgidae (Nightjars) Pp. 302-386 in: del Hoyo, J., Elliot, A. and Sargatal, J. Handbook of the Birds of the World, vol. 5: Barn-owls to Hummingbirds. Lynx Edicions, Barcelona, Spain.
Cleere, N. and Nurney, D. (1998). Nightjars. A guide to Nightjars and Related Nightbirds. Pica Press, UK.
Hale, M. (2002). Photospot: Hong Kong Nightjars. Hong Kong Bird Report 1998: 149-151.
Lewthwaite, R. W. and Yu, Y. T. (2007). Hong Kong Nightbird Survey 2000-2001. Hong Kong Bird Report 2001-02: 213-238.
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.
