Ancient Murrelet Synthliboramphus antiquus 扁嘴海雀
Category I. Scarce passage migrant through offshore waters in spring, but rare in autumn and winter, when it is more likely to occur in inshore waters.
IDENTIFICATION
Nov. 2020, Michelle and Peter Wong. Non-breeding plumage.
Very small with short, relatively deeply-based and pointed bill. In non-breeding plumage has black head from chin back to nape, white extending up behind eye, greyish upperparts and whitish underparts.
Nov. 2020, James Kwok. Breeding plumage.
In breeding plumage black head and entire throat, white supercilium not extending in front of eye and pale bill are diagnostic. Flies low over sea showing white underbody, largely white underwing and narrow black half-collar.
VOCALISATIONS
Ancient Murrelet has a diverse vocabulary on the breeding grounds dominated by the ‘chirrup’ call (Gaston and Shoji 2020). A variant of this call is given away from the breeding area.
DISTRIBUTION & HABITAT PREFERENCE
Most records are from offshore waters in the vicinity of Po Toi from where migrants are noted flying northeast. Other records are from boat-based surveys or ferries in the same area, while there is a scattering of other records from other areas, though mainly in non-estuarine waters.
OCCURRENCE
Chalmers (1986) included only three records of Ancient Murrelet, the first being a breeding plumage adult off the north coast of Kat O Chau, Mirs Bay on 18 May 1975 (Viney 1976). From 1975 to 1998 there were 17 records concerning 30 birds between 26 November and 18 May. These included flocks of seven in Mirs Bay on 6 April 1996 and five to the south of HK Island on 27 February 1997.
Increased observer coverage was the cause of the increase in records, which has continued since and resulted in approximately 70 records since 1999, some involving birds on migratory flight over the sea near Po Toi. The highest count is nine in southern waters on 19 February 2006. From Po Toi sea-watches have recorded up to six birds a day flying northeast from 23 February to 21 April. Figure 1 indicates that the number of birds wintering is low and that most birds occur on spring passage. Extreme dates are 26 November and 29 May.
BEHAVIOUR, FORAGING & DIET
Occurs singly or in small groups on the sea or migrating north in small parties in spring. Rarely seen foraging, though one remained in Po Toi harbour for a week diving for prey.
RANGE & SYSTEMATICS
Breeds in the north Pacific on the Aleutian Islands, the Gulf of Alaska, Sea of Okhotsk and south of Kamchatka Peninsula, Peter the Great Bay and the Yellow Sea; winters in coastal seas of the east and west Pacific, including east China (Gaston and Shoji 2020).
Two subspecies are recognised: the nominate, which breeds in much of the range, and microrhynchos, which breeds on the Commander Is.
CONSERVATION STATUS
IUCN: Least Concern. Population trend decreasing.
Figure 1.
Gaston, A. J. and A. Shoji (2020). Ancient Murrelet (Synthliboramphus antiquus), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.ancmur.01
Viney, C. A. (1976). Systematic List for 1975. Hong Kong Bird Report 1975: 7-43.
