Yellow-streaked Warbler Phylloscopus armandii 棕眉柳鶯
Category I. Rare autumn passage migrant and winter visitor, one spring record; occurs in open country areas and reed marsh.
IDENTIFICATION
Nov. 2018, John Clough.
12.5-13.5 cm. Very similar to Radde’s Warbler, with the sole diagnostic feature in the field being call, a metallic ‘tzik’ that is bunting-like at times. A summary of identification issues is provided in Leader (1995).
Plumage differences are very poorly marked and for many birds not apparent. However, compared to Radde’s Warbler, Yellow-streaked may have 1) a dark brown ground colour to the breast and upper belly forming a darker breast band (typically whitish on Radde’s, which rarely shows a breast band), 2) a paler, more clearly-demarcated throat, 3) a supercilium that is often narrower and more distinct in front of the eye and whitish behind (variable in Radde’s), 4) plainer ear coverts and more brownish upperparts (more olive on average in Radde’s). First-winter birds have rather buff or yellowish-buff underparts; however, the streaks are very difficult to see.
The bill is slightly finer than Radde’s but only marginally sturdier than Dusky Warbler; the upper mandible, however, is decurved as on Radde’s. The contrast between upper and lower mandible is slightly more marked than on Radde’s and there is a dark tip to the lower mandible. The legs are thicker than Dusky Warbler but thinner than Radde’s. Differences in plumage and bill structure are subtle and subjective, and call is the only feature currently known to reliably identify this species.
VOCALISATIONS
The diagnostic call of Yellow-streaked Warbler is a fairly loud ‘tzik’.
The song begins with 2-3 introductory notes followed by a flat rattle (neither as forceful nor as rich as Radde’s Warbler).
DISTRIBUTION & HABITAT PREFERENCE
Occurs is open-country areas with dense bushes and in reed bed. As most records are of trapped birds, it has generally been recorded at Mai Po NR, particularly in reed marsh, and formerly at Kadoorie. However, it has also been recorded in other widespread areas of HK including HK Island, Lantau, Ho Man Tin, Ho Chung, Long Valley, Tai Lam CP and Ping Che.
OCCURRENCE
The first record was of one trapped at Kadoorie ARC on 16 October 1994 (Leader 1995). This was followed by eight further records up to 17 November 1998. Subsequently, however, there was a gap of over ten years before the next, which occurred on 26 October 2009. Regular trapping activities in reed marsh, increased observer coverage and an understanding of the importance of the call enabled it to be recorded nearly annually from 2010 until 2020, though usually no more than three times a year.
The 20 records up to 2020 occurred in the period 16 October to 9 February, with a further record of a migrant in song on 9 April 2012. Most records have occurred from the last week of October to 17 November. The longest-staying bird was present from 8 November 2018 to 19 January 2019 at Mount Austin.
BEHAVIOUR, FORAGING & DIET
Forages low in bushes or trees. Does not appear to utilise as large a foraging area as Radde’s Warbler, making it somewhat easier to watch when it is present.
RANGE & SYSTEMATICS
Nearly endemic to China in the breeding season, when it occurs from northeast China southwest through north central parts of the country as far as north Yunnan and southeast Tibet, and just into northeast Myanmar. In the non-breeding season, it occurs in southwest China and north Indochina (Clement 2020, Liu and Chen 2021).
CONSERVATION STATUS
IUCN: Least Concern. Population trend stable.
Clement, P. (2020). Yellow-streaked Warbler (Phylloscopus armandii), 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.yeswar1.01
Leader, P. J. (1995). Field identification of Dusky, Radde’s and Yellow-streaked Warblers. Hong Kong Bird Report 1994: 170-180.
Liu, Y. and S. H. Chen (eds) (2021). The CNG Field Guide to the Birds of China (in Chinese). Hunan Science and Technology Publication House, Changsha.
Leader, P. J. (1995). Yellow-streaked Warbler: the first records for Hong Kong. Hong Kong Bird Report 1994: 123-126.
