I think this is a White-rumped Shama - a popular species in the cage-bird trade, which has unfortunately led to a decrease of the number of birds in the wild in parts of its range.
It is a Category III bird in Hong Kong i.e. an escaped or released bird.
Coincidentally, I saw one at Shek Kong on March 20th.
David
www.birdinghongkong.com
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Last edited by ddavid at 25/03/2017 22:08 ]