Two-barred Warbler Phylloscopus plumbeitarsus 雙斑柳鶯
Category I. Uncommon passage migrant and winter visitor to woodland.
IDENTIFICATION
Oct. 2021, Michelle and Peter Wong.
11.5-12 cm. Slightly smaller, larger-headed and narrower-billed than Arctic Warbler from which it also differs in usually having two wing bars, a yellow lower mandible with no or very restricted dark mark, greyer crown and legs, supercilium usually reaching forehead, a slightly shorter primary projection and in lacking obvious greyish streaking on the breast (Shirihai and Svensson 2018). Call is distinctive and differs significantly (see below).
VOCALISATIONS
The typical call is a rolling and rather full, moderately high-pitched ‘tirririt’, ‘chirilee’, ‘chirrit’ or similar. Usually sounds disyllabic or even trisyllabic.
The song is noted from late February, particularly in late April and May, but rarely in autumn. Not unlike Swinhoe’s White-eye in timbre and pitch though more emphatic, the strophes usually include a number of repeated elements uttered in a rather insistent manner.
DISTRIBUTION & HABITAT PREFERENCE
Occurs throughout HK in open and closed-canopy forest, disturbed woodland, shrubland, park-type habitat in the urban area and other sites with sufficient tree cover.
OCCURRENCE
The first accepted record was of one trapped at Kadoorie ARC on 27 September 1989 (Leader 1990). Following this, four field records prior to the trapped bird were accepted, the earliest of which concerned one at Mount Davis on 6 April 1987. It has subsequently been recorded every year since 1989 and is an uncommon winter visitor that was, to some extent at least, overlooked previously. The numbers recorded are on the rise, no doubt due in part due to an increase in observer activity, but there appears also to be a genuine increase.
The earliest record in autumn concerns one on 11 September 2010. It remains rare in September, but numbers increase in October to a peak in the third week of the month (Figure 1). From the second week of November to the last week of January numbers are broadly similar, but from the first week of January they decline to a low in March. This is likely due to a reduction in vocal activity and/or a departure for cold weather reasons early on, and departure on spring migration later. There is a weak spring passage in April and the first half of May, and the latest record occurred on 17 May 2020.
BEHAVIOUR, FORAGING & DIET
Forages in the canopy and prefers higher trees. Foraging manner livelier than that of Arctic Warbler. Observed eating insects, caterpillars and small spiders.
RANGE & SYSTEMATICS
Monotypic. Breeds in southeast Siberia from the area of Lake Baikal and north Mongolia east to the Sea of Okhotsk and south to northeast China; winters in Indochina and southern coastal provinces of China (Clement 2020, Liu and Chen 2020).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Figure 1.
Clement, P. (2020). Two-barred Warbler (Phylloscopus plumbeitarsus), 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.grewar2.01
Leader, P. J. (1990). Two-barred Greenish Warbler: a species new to Hong Kong. Hong Kong Bird Report 1989: 105-108.
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.
Shirihai, H. and L. Svensson (2018). Handbook of Western Palearctic Birds Vol. 1. Passerines: Larks to Warblers. Helm, London.
