Bianchi’s Warbler Phylloscopus valentini 比氏鶲鶯
Category I. Rare passage migrant and winter visitor to wooded areas.
IDENTIFICATION
Nov. 2009, Michelle and Peter Wong.
11-12 cm. Yellow and usually unbroken orbital ring (may be slightly diffuse above the front of the eye), blackish lateral crown stripe usually fading out on forehead, grey median crown stripe (greener on forehead), grey along lower edge of lateral crown stripe, dull greyish-green upperparts, yellow underparts with variable amount of greenish on breast sides and flanks, distinct wing bar on greater coverts (rarely faint or lacking), relatively long and thick bill.
Separated from extremely similar Plain-tailed Warbler by greater amount of white in tail and from very similar Grey-crowned and Martens’s Warblers by less distinct head pattern (Alström 2020, Leader and Carey 2016). Call diagnostic (see below).
VOCALISATIONS
The call is ‘tyoo’, ‘syoo’ or ‘choo’ that descends sharply in pitch.
DISTRIBUTION & HABITAT PREFERENCE
Most records have occurred on Po Toi. Elsewhere it has been seen in closed-canopy forest in the central and east New Territories.
OCCURRENCE
The first record was a bird trapped at Kadoorie Agricultural Research Centre on 11 November 1990. The next occurred on 9 October 2004; subsequently it was recorded in approximately 50% of winter periods from 2006/07 to 2019/20. Extreme dates are 9 October and 26 January; given these dates and the fact that most of these records are from Po Toi, it appears to be largely a passage migrant.
Lack of knowledge regarding field identification of members of the ‘golden-spectacled’ group of warblers means only in-hand records before 2002 can be assigned to species.
BEHAVIOUR, FORAGING & DIET
Forages on insects unobtrusively in the understorey, often making short flights to take insect prey on the vegetation or in the air. Often adopts a rather horizontal posture.
RANGE & SYSTEMATICS
Breeding and wintering ranges remain imperfectly understood. The nominate subspecies breeds in central and south China into north Myanmar, while P. v. latouchei breeds locally in southeast China in Hubei, northeast Jiangxi, Fujian, north Guangdong and north Vietnam. Winters to south in China and north Indochina (Alström 2020, Liu and Chen 2020).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Alström, P. (2020). Bianchi's Warbler (Phylloscopus valentini), 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.biawar1.01
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.
Leader, P. J. and G. J. Carey (2016). The identification of Seicercus warblers in Hong Kong. Hong Kong Bird Report 2014: 322-333.
