I don't think this can be Ryukyu Robin - females seem to be pale on the lores and the lower/front half of the ear coverts, unlike this bird. The scales on Ryukyu seem poorly marked. Ryukyu also has a curious structure, looking large-headed and large-footed relative to a small body. Compare with this bird:
http://orientalbirdimages.org/se ... _ID=&pagesize=1
It does not quite fit with Rufous-tailed either - not just the orange saturation of the upperparts, but also the head pattern - there is an orange wash to the ear coverts which would not be expected for Rufous-tailed, and this extends down towards the throat. The throat looks particularly well demarcated with white. Rufous-tailed often also seems to show a slight half-collar of white, which this bird apparently lacks. Also note that the tail does not contrast with the mantle, as would be expected for Rufous-tailed.
On balance, I think this is most likely a female Japanese Robin. We know that young female Siberian Rubythroats have white throats, but develop redder throats in adults. Could this also be the case with at least some Japanese Robins, and that this is a first-winter female in a poorly-known plumage?
One important lesson for all of us I think is how we would identify this bird on a brief view in the field? These woodland chats can be very skulking and difficult to observe. I think there is a good chance it could be overlooked as a Rufous-tailed. If this is a regular plumage for Japanese Robin, is it possible this species is under-recorded in Hong Kong?
