I have seen 3 mandarins (one male, 2 females) around the Sha Po/Kam Tin area a couple of times this winter. I believe there has also been a sighting near Nam Sang Wai.
I suspect that all these records (including the Tai Sang Wai record) relate to the same birds, which are travelling around the area.
The birds appear to be unringed, but due to the number of individuals and long stay, I don't think they are wild. In fact, I think they are probably the same as the pair that was present at Kam Tin last winter and the elastic on the legs has fallen off. That leaves me with three questions though:
How did they lose the rings?
Where were they last summer? (in HK or elsewhere)
And, most importantly, where did the third bird come from?