This is the Greylag Goose that was at Nam Sang Wai for a couple of weeks in November. The final conclusion, based on other photos taken at the time, is that it was an escape and was the same as the bird at Long Valley previously.
See:
http://www.hkbws.org.hk/BBS/view ... &extra=page%3D1
http://www.hkbws.org.hk/BBS/view ... page%3D1&page=4
http://www.hkwildlife.net/viewth ... &extra=page%3D1