Hume’s Leaf Warbler Phylloscopus humei 淡眉柳鶯
Category I. Rare winter visitor and passage migrant to wooded areas. Most records are P. h. mandellii, with the nominate taxon very rare.
IDENTIFICATION
Dec. 2019, Roman Lo. P. i. mandellii.
10-11 cm. Very similar to Yellow-browed Warbler but the taxon mandellii (illustrated) differs in the following ways: legs and bill darker, plumage overall greyer (especially early in winter), greyish (not blackish) centres to tertials that have less distinct pale fringes, less distinct dark bases to flight feathers, slightly thinner wing bars (especially on median coverts), more diffuse crown stripe, paler cheeks, buff fore part of supercilium, more distinct eye stripe on lores.
Nominate humei differs slightly from mandellii in having darker bill and legs and generally rather colder plumage tones, including less bright green fringes to flight feathers. See Vocalisations.
VOCALISATIONS
Compared with Yellow-browed Warbler the call of mandellii is a slightly shorter and more monosyllabic ‘chweet’ that is not obviously inflected terminally.
In comparison with mandellii the call of nominate humei is a slightly lower-pitched, slightly longer and more nearly disyllabic ‘chooeet’.
The song of mandellii is a long, drawn-out buzzing ‘tzzzzeeeeeo’ that falls in pitch; this may be accompanied by a double-note ‘tsweeoo-tsweeoo’, or the latter may be uttered alone.
DISTRIBUTION & HABITAT PREFERENCE
Records of wintering birds mainly occur in closed-canopy forest though also in mixed habitat locations such as Lam Tsuen, while migrants have occurred on Po Toi and near the top of Tai Mo Shan and Sunset Peak.
OCCURRENCE
One trapped at Kadoorie ARC on 2 December 1989 and 27 January 1990 was the first record (Leader 1990), and by the end of 1997 there had been four records. There was subsequently a gap of nearly seven years before the next, in November 2004. Thereafter the frequency with which it was recorded increased, no doubt due to increased familiarity with its call and appearance. Since 2015 it has been recorded annually with possibly as many as seven individuals recorded in winter 2019/2020. Extreme dates are 14 October 2012 and 23 February 2020 for autumn migrants and winter visitors, and 15 March 2020 to 13 April 2009 (Carey and Williams 2012) for migrants in spring.
Most reports appear to refer to the taxon mandellii, which breeds nearest HK, but there are two records of nominate humei, which were identified on the basis of call. These occurred at HK Wetland Park on 9 December 2018 and at Pak Sha O from 1 November 2020 to 9 March 2021.
BEHAVIOUR, FORAGING & DIET
Typical Phylloscopus behaviour, actively foraging among the foliage, both just below the canopy but also low down in the understorey, the latter of which is unlike the typical foraging behaviour of Yellow-browed Warbler (Leader 1992).
RANGE & SYSTEMATICS
Two subspecies are recognised: P. h. humei breeds in south central Russia and east Kazakhstan to Xinjiang in northwest China and central Nepal, while P. h. mandellii breeds from southwest and central China northeast to Beijing. The wintering grounds of nominate humei ranges from northeast Afghanistan through north Pakistan and north India to Bangladesh, while mandellii winters in northeast India, north Indochina and southwest China (Clement 2020, Liu and Chen 2020); small numbers appear to winter as far east as HK.
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Carey, G. J. and Williams, M. D. (2012). Identification of a vocalising Phylloscopus warbler on Po Toi. Hong Kong Bird Report 2009-10: 310-217.
Clement, P. (2020). Hume's Warbler (Phylloscopus humei), 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.humwar1.01
Leader, P. J. (1990) Hume’s Yellow-browed Warbler: a new subspecies for Hong Kong. Hong Kong Bird Report 1989: 99-104.
Leader, P. J. (1992). Observations on the call and behaviour of a Hume’s Yellow-browed Warbler in Hong Kong. Hong Kong Bird Report 1991: 198.
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.
