See 2012 HK Bird Report page 143, comment on Plate 34 which goes as follows
"Plate 34 Japanese Bush Warbler Horornis diphone canturians 日本樹鶯
Mai Po NR, 9th April 2012 米埔 2012年4月9日
Jacky Chan 陳家華
Although field separation criteria between Japanese Bush Warbler, H. diphone (ssp. canturians) and Manchurian Bush Warbler H. borealis have yet to be fully resolved, this (i.e.the photo in the 2012 HKBR) is considered to be a Japanese Bush Warbler due to the rather uniform upperparts, extensively rich crown and lack of grey on the nape (PJ Leader in litt.).
因其較平均的上半部、深色的頭頂及缺乏灰色的頸部,所以辨認為遠東樹鶯 H. borealis 而非日本樹鶯"
Although I am not an expert, that would indicate the bird in this photo is a Manchurian Bush Warbler Horornis borealis since the crown is not richly coloured and there appears to be some grey around the nape in the second photo.
I can't reproduce Plate 34 here as we do not have the photographer's permission outside of the HKBR, but it does appear a more colourful bird than this one.
[ Last edited by wgeoff at 12/01/2015 07:01 ]