I think this is my fault for suggesting the barring on the head and back was distinctive of Red-backed, which it clearly is not. As I say, I'm no expert.
Paul Leader has listed the key identification features above as
'very warm upperparts, white ground colour to the underparts, long primary projection, rather square tail and white fringe to the outer tail feathers'
but I think the pale face mask is also distinctive, at least between Brown and Red-backed.
Another source for the differences is pages 258 to 260 of the 2007-08 HKBR, the first HK Record of Red-backed Shrike, which includes a description in English and in Chinese and is given here
"This bird was easily aged as a first-winter due to the retained juvenile greater coverts and tertials. Identification was less straightforward but was based on a combination of rather rufous tones above (strongest on the uppertail coverts), a long primary projection, whitish underparts, more square (i.e. less rounded tail), rather slender bill and poorly-defined mask. In combination these eliminate other shrike species, but especially Brown Shrike L. cristatus, the most likely confusion species. Red-backed Shrike breeds from Europe west to Xinjiang Province, China. It is a long distance migrant and has been recorded as a vagrant to Japan, South Korea and Taiwan. Given the condition of this individual and migratory behaviour of the species, the Records Committee readily accepted this to Category I of the Hong Kong List.
辨認這鳥為首次渡冬鳥很容易，是因為牠保留了幼鳥的大覆羽和三級飛羽。要辨認這鳥種就較為因難，不過根據上述部分略帶紅色(在尾上覆羽最為明顯)、修長的外型、白色的下體、較方型的尾部(即尾部形狀沒有那麼圓)、稍為纖細的喙部，以及不太明顯的眼紋等特徵可得出結論。綜合這些特徵，便可以排除屬其他伯勞的可能性，尤其是最有機會混淆的紅尾伯勞 L. cristatus。紅背伯勞的繁殖地遍及西歐至中國新疆。這鳥會作長途遷徙，曾在日本、南韓和台灣有紀錄，並被列作迷鳥。基於這鳥的情況以及這鳥種的遷徙行為，紀錄委員會十分樂意將這鳥種加入香港鳥類名錄第I類。"
I think it is quite possible some juvenile/first winter Red-backed Shrikes have been overlooked in the past, since we've now had five records in five years.
[ Last edited by wgeoff at 3/10/2013 07:44 ]
