Kloss’s Leaf Warbler Phylloscopus ogilviegranti 白斑尾柳鶯
Category I. Probably rare winter visitor to closed-canopy forest.
IDENTIFICATION
Dec. 2020, Peter Ho.
10-11 cm. Resembles nominate form of Hartert’s Leaf Warbler but differs in smaller size, shorter wings and tail, slenderer bill and more active foraging behaviour resembling Yellow-browed or even Pallas’s Leaf Warbler (without the hovering). It does not creep along tree trunks or branches. The lateral crown stripes are paler while the central crown stripe is less distinct and poorly-marked on the fore crown and the supercilium is less yellow and narrower in front of the eye. The legs are paler, and the lower mandible is entirely pale. The throat, upper chest and undertail coverts are washed yellow, the belly and flanks less so.
Dec. 2022, Guy Miller.
The small size and proportions are evident in this image.
VOCALISATIONS
The call is high-pitched and multi-syllabic (generally two to four syllables). It begins with a short emphatic element that is vertical on a sonagram. Of the Phylloscopus in HK, the call most resembles Two-barred Warbler in structure but is higher in pitch than Greenish Warbler.
Although only low-intensity song has been heard in HK, it appears to resemble the full song of P. o. disturbans, which can be heard in this recording.
DISTRIBUTION & HABITAT PREFERENCE
Occurs in closed-canopy forest.
OCCURRENCE
The first records occurred at Tai Po Kau on 16 March 2017, and at Pak Sha O on 5 January 2019 and 1-2 February 2020 (Carey and Martinez 2023). The last of these records enabled observers to get to grips with the voice and appearance of the species, and there followed a series of records that indicates this species may be a regular, if rare, winter visitor.
BEHAVIOUR, FORAGING & DIET
Has a lively foraging behaviour that differs noticeably from that of Hartert’s Leaf Warbler. Its movements suggest Yellow-browed Warbler or even Pallas’s Leaf Warbler.
SYSTEMATICS & RANGE
Three subspecies are recognised. The nominate breeds in southeast China from Guangxi east to Fujian (probably wintering in Vietnam), P. o. disturbans breeds in central China in Sichuan, Gansu, Shaanxi and Yunnan (wintering in south part of breeding range, southern coastal provinces of China and Indochina), while P. o. klossi is resident in south Laos and central to south Vietnam (del Hoyo et al. 2020, Liu and Chen 2020).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Carey, G. J. and J. Martinez (2023). Kloss’s Leaf Warbler Phylloscopus ogilviegranti: the first records for Hong Kong. Hong Kong Bird Report 2019: 256-260.
del Hoyo, J., N. Collar, and D. A. Christie (2020). Kloss's Leaf Warbler (Phylloscopus ogilviegranti), 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.klolew1.01
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.
