ajohn

David Stanton and I saw this bird on Monday evening, in the same location on Tan Shan River (for those who are not familiar with the site, Tan Shan River is on the southern side of Sha Tau Kok road).
Fortunately the bird was standing out of the water when we managed to find it. We were able to get scope views of both legs, and confirmed that the bird is not ringed.
I have some personal doubts about the record, however. Contrary to Brendan's suggestion that the bird is shy, I was concerned that it was directly across the river from a village house - perhaps only 10-15m from the house. There are a number of other habitat options in the area (including e.g. the reservoirs at Ho Pui/Lau Shui Heung), and I would expect a wild bird to be a bit more shy and avoid a location with such levels of disturbance.
I am also concerned that I know there is (or, at least, used to be) an aviculturalist in this area - I have previously been hiking in the area and heard exotic bird calls coming from the back of one of the houses (including e.g. Grey Peacock-Pheasant).

Mandarin is a tricky species in a Hong Kong context. HK is close to the natural range, and in the past the species has apparently occurred here in a natural state. There is no reason that wild birds should not continue to occur here. However, this is a very frequently traded species and it is very difficult with each individual to be sure of possible provenance.

As an example, the Mandarin pair I found at Kam Tin a few years ago included a male with a plastic ring (cable-tie?) on one leg, suggesting a captive origin - this was not visible when I first found the birds, and only later discovered from photos. The female of that pair had no such evidence of captive origin. These birds apparently disappeared for the entire summer, reappearing the following winter - at one point with an additional female. It is feasible that one or both females were from a wild population but it seems more likely that these were from the same (unknown) origin as the male. Without photos showing the ring on the male, these would perhaps have been considered wild, as has been suggested for the current birds.

Overall, I have now seen 5 free-flying Mandarins in Hong Kong. The species is not currently on my HK list - I was hoping the Tan Shan bird would change this, but somehow it just didn't feel right for a wild bird and I have still not added it to my list.

ajohn

The fact that two birds are found at a similar time does not necessarily mean that they escaped at the same time. Alternatively, the fact that they are found at two different locations does not necessarily mean that they escaped from two locations. Once they are free-flying, birds such as this could be very mobile. As I mentioned in my earlier post, the KT mandarins disappeared for a long period over the summer and then reappeared the following winter - presumably they went somewhere in the intervening period. Similarly the fantail at Ng Tung Chai has appeared over a number of separate winters but disappeared during the summer.

It is possible that the presence of these two individuals is linked i.e. the birds arrived in HK, or escaped, together and have subsequently ended up in different locations. The simultaneous appearance of mandarins (or indeed Hawfinches or Red-headed Buntings) at more than one site does not prove a wild origin for any of these individuals.

Mandarins are common (and I think relatively easy to breed) in captivity - I'm not sure how highly valued they are. They have apparently been declining gradually in their native range, yet there seems to have been an increase in the number of records in HK in recent years and my impression is that the species currently seems to be almost annual here (although I don't have the data to back this up!). Some are obvious escapes, some are not. It is even possible that many of the recent records relate to the same individuals which could be mobile throughout HK or further afield.

There is always a problem with separating possible wild individuals from ex-captive individuals. As I said, something about this individual didn't feel right to me. Perhaps it is wild - I don't know - but I didn't think that at the time (in fact, I thought the KT birds seemed more like wild birds than this individual).

Incidentally, the only photos I have seen of the Lam Tsuen bird (male) are those posted a couple of days ago by Vivian. I understand there are more photos of this individual - are these still available online? Also, has anyone seen the legs on this bird to assess whether or not it is ringed. At the time of the KT birds, it was suggested that males are more often ringed in captivity than females because males are more highly valued in the trade.

ajohn

Mandarin is usually a species associated with wooded rivers and lakes. The fact that there are a number of records from fish ponds in the Deep Bay area (e.g. Tai Sang Wai, Mong Tseng) is one thing that concerns me about the recent occurrence of the species in HK. I would think some of the smaller reservoirs (e.g. Hok Tau, Ho Pui) should provide better habitat.