hgeorge

An Emei Leaf Warbler Phylloscopus emeiensis Alstrom and Olsson, 1995 was found within a bird flock at Ng Tung Chai around 1000am.

This warbler perfectly matches with the description of Emei Leaf Warbler and is  dissimilar to
1) Claudia's Leaf Warbler Phylloscopus claudiae by  smaller size; less distinct and pale crown stripe (very distinct and much brighter crown stripe in Claudia's LW); no obviously white margin of tail (distinct thin white margin on tail underside in Claudia's LW) and thin tarsus (thick in Claudia's LW).
and
2) White-tailed Leaf Warbler Phylloscopus ogilviegranti ogilvegranti/disturbans by less yellow and pale crown stripe and supercilium (yellow crown stripe and supercilium in White-tailed LW); dull green to grey-green mantle (bright green mantle in White-tailed LW) and no white on inner web of tail (underside) (more white in White-tailed LW).

Descriptions are made below:
Overall: small size of phylloscopus leaf warbler, short body, mainly green.  
Head: long supercilium, pale yellowish, and much brighter yellowish in front of eyes, paler behind eyes. Pale median crown stripe, not very distinct. Eye stripe dark grey-green, not blackish, tapering in front of eyes, broader behind eyes. Lateral crown strip similar to eye stripe, uniformly greyish green, slightly darker behind. Ear coverts greenish.
Underpart: Underpart whitish, especially belly. Throat yellowish green, not bright yellow. Breast with pale yellowish stripe, very thin. Undertail-coverts obviously pale yellow with comparison to the white lower belly. Flank yellowish.
Upperpart: Greyish green to dull green from mantle to tail. Scapulars same as mantle.
Tails: Upperpart dull green. Underpart dark, without apparent white margin on underside of tails.
Wings: Two wing-bars, yellowish. The tips are broader on greater coverts.  Tips of median coverts are less distinct compare to the wing-bar of greater coverts.
Bill: Thick and slender. Upper mandible dark, likely blackish. Lower mandible orange-yellowish, slightly darker at the tip.
Legs: Grey to grey-green.
Size: Similar to Kloss's Leaf Warbler Phylloscopus ogilviegranti ogilvegranti/disturbans but slightly larger, slightly smaller than Yellow-browed Warbler Phylloscopus inornatus and smaller than Goodsoni's Lead Warbler Phylloscopus goodsoni.
Song: No song was heard during observation.
Note: Active in treetop. Sometimes hovering over branches. Found in a small bird flock (Grey-headed Flycatcher, Blue-winged Minla and Scarlet Minivet) on the access road.
Related experience:
Emei Leaf Warbler in Sichuan Province
White-tailed Leaf Warbler in Yunnan, Sichuan and Jiangxi Provinces
Goodson's Leaf Warbler and related subspecies in HK

References:
Alstrom, P. and Olsson, U. 1995. A new species of Phylloscopus warbler from Sichuan Province, China. Ibis 137: 459-468.
Baker, K. 1997. Warblers of Europe, Asia and North Africa. Princeton University Press, New Jersey.
Brazil, M. 2009. Birds of East Asia – China, Taiwan, Korea, Japan and Russia. Princeton University Press, Princeton and Oxford.
Del-Hoyo, J., Elliott, A. & Christie, D.A. (eds). 2006. Handbook of the Birds of the World volume 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona.
Olsson, U., Alstrom, P., Ericson, P.G.P. and Sundberg, P. 2005. Non-monophyletic taxa and cryptic species - Evidence from a molecular phylogeny of leaf-warblers (Phylloscopus, Aves). Molecular, Phylogenetics and Evolution 36: 261-276.

Any comments are welcome!
George

hgeorge

Thanks for your comments. Of course, I am expected and ready to be challenged.
First thing, no white on tertials, is greenish, I haven't mentioned, same as the pattern as P. claudiae/goodsoni/ogilviegranti. If the outer web is white on tertials, of course, I must consider it as Yellow-browed Warbler.  Also, this year, I saw many, may be more than fifty to seventy individuals of Yellow-browed Warbler at Tai Po Kau, Shing Mun and Ng Tung Chai due to my nature of work. White outer web on tertials is obvious, is present in this time, for this feature, not difficult to observe in wild. Bill of Y-b W is short with yellowish base. Face pattern is strong with mottling in Y-b W (For this warbler, the ear-coverts are grey-greenish, without obvious mottling;). Wing-bars is whitish in Y-b W. Eye-stripe in Y-b W is dark olive, darker than the lateral crown stripe, very obvious contrast. I can’t see these features in this warbler.
For the bill, this is the light and angle effect, like a shadow, the lower mandibile is almost completely pale orange, except near the tip, slightly darker.
For size, different authors have different opinions on the size, depends on the subspecies, so, “Blyth's” LW is 10.5-11, 10.5-12, 12cm, Emei LW is 10, 11-12cm, White-tailed is 10cm, 10-11cm. Emei is between Blyth and White-tailed. If you can access the paper of Alstrom & Olsson, 1995, in page 461, you can see two images to compare Emei and Blyht's and Emei and White-tailed. Apparently, Emei LW is smaller than Blyht's and bigger than White-tailed. The crown stripe in Emei is less distinct than Blyth's and White-tailed. This warbler, of course, fit into this feature.
For the supercilium, the pale yellowish supercilium is from base of bill to beyond rear edge of ear-coverts based on the holotype (image) and the descriptions of the paper. The supercilium is slightly long due to the angle of the head.
For the tail, in fact, you may see the darkness rather than any pattern. For Emei LW, according to Alstrom & Olsson, 1995:459 “inner webs of outermost two pairs of rectrices show narrower whitish edges (≦0.5mm on outermost and even narrower on penultimate), which are lacking or very indistinct at tip of penultimate.”, hence, it is very indistinct.
Unfortunately, no song was heard, I will try to take song record and more photos of this warbler to convince the record committee.
George