ajohn

Over the last week or so I have seen a few flocks of Red-billed Leitohrix in the New Territories - four different flocks (at least 13 birds) around Pat Sin Leng and a flock at Tai Po Kau. This seems to be fairly unusual - normally I find this species fairly uncommon in HK, and the established breeding population seems (at least to me) to be largely confined to Tai Mo Shan and the upper areas of Shing Mun.

This has led me to three questions:
1. Has anybody else noticed increased numbers of this species in HK this winter?

2. Where have these birds come from? The flocks at Pat Sin Leng are a fair distance from the breeding population at Tai Mo Shan. Is anyone aware of them breeding near Pat Sin Leng?

3. Does the RC ever assess the status of species such as this to consider whether truly wild birds may occur in HK?

I know it is a very common cage bird, and there is a high chance of escapes occurring, but these sightings have been in several locations over a short period, some fairly remote from human populations. I have previously seen the species in the north-east, but only once or twice and I think only in mid-winter (January-February), despite the fact that I often visit the area in spring, summer and autumn.
I know it is considered to be a truly resident species and is probably considered incapable of making it here unaided, but this was also the accepted wisdom about Pygmy Wren-babbler until they suddenly started turning up in HK. It is a common bird in some south China forests, but I don't know how close the nearest wild populations are to HK.

ajohn

It is very easy to say all birds are the result of releases for species such as this, and to leave that as the status for evermore. There is no question that Red-billed Leiothrix is common in the cage bird trade, and no doubt some escapes or deliberate releases occur (Hong Kong Island in August would seem to me to be a very likely release).

The point I was trying to make is that it may be worth keeping an open mind rather than just flippantly saying 'Bird Release' for all records. The RC regularly reassesses Cat III birds to assess whether wild birds may be occurring (Small Niltava, Mrs Gould's Sunbird and Hawfinch being recent examples of species which have changed status). I was trying to ask whether similar assessments are done for Cat II species. Most of these would be very difficult because they are currently so widespread (Rufous-capped Babbler, Greater Necklaced Laughingthrush etc.), but Red-billed Leiothrix is generally, in my opinion, a rather uncommon bird in HK with a fairly restricted distribution.

I am not saying these birds are wild or that the current status is necessarily incorrect. It may be that there are feral populations I am not aware of or that the population on TMS has had a very successful breeding season and spread to other sites. But if there has been a sudden, simultaneous increase in numbers at geographically-separated sites away from human activity, it seems unlikely to me that these are all the result of recent releases and that something else may be going on.

Any reassessment would, of course, require the consideration of appropriate information, for example the current status of feral populations, the current status in the cage bird trade, the current status over the border in China, any evidence for movements of the species and any pattern in records.

ajohn

As Richard mentions, the Avifauna does provide evidence for the presence of escaped/released birds in Hong Kong, including the high proportion of individuals showing cage damage.

On the other hand, the Avifauna also highlights the fact that a high proportion of cage-damaged birds may indicate that the population (at least at that time) was not self-sustaining. Furthermore, it points out that after the species was listed by CITES in 1997 there was a decline in the number of records in Hong Kong (again, supporting the presence of released birds). This decline appears to have continued according to records in the bird report e.g. peaks counts of three in 2008 and 2009, and only two records in 2010.

This is the basis for me suggesting that this winter may be unusual - there are relatively few records in recent years of this species, whether related to cage releases or otherwise, and yet suddenly it seems to have appeared a several different sites over a short period of time. This influx has coincided with high numbers of other species e.g. record numbers of Chestnut-collared Yuhina and Tristram's Bunting.

I find it hard to exaplin the influx in terms of captive release - the CITES ban which supposedly led to a reduction in escapes previously remains in place, and it is hard to see why there should suddenly be an increase in releases at a number of different locations. I initially wonder whether an assessment of status in light of the CITES ban (introduced over 15 years ago) might be justified.