I would say this is a first-winter Red-breasted Flycatcher. Note the combination on limited black in the upper tail coverts, tail itself apparently not fully black (but possibly due to the angle?), the brownish tones to the upperparts, buff wash to what can be seen of the underparts, buffish pale tips to the greater coverts, obvious 'rose thorn' shape to the tertial tips, and the pale base to the lower mandible.
Do you have additional photos?
This really has proved to have been overlooked in the past and is now clearly a regular but rare winter visitor to Hong Kong which is amazing given that the nearest breeding gounds are in northern Iran. I have one looking set to winter near my house in Sai Kung, although that is not giving quite the views that this bird is, but is very vocal.
[ Last edited by lpaul at 2/12/2010 14:11 ]