Several points to respond to, as follows:
Active wing moult of Ferruginous Duck: SY Chan's very nice photos clearly show P1 in pin; I agree no evidence of moult in the Greylag;
I agree with Geoff W that the Greylag Goose seems to be a different individual to the 2011/12 bird, bill structure definately seems to be different and this is unlikely to change over time once fully grown;
I chose my words carefully, I 'have reservations' regarding the origin of these birds, I did not state that I considered them to be ex-captive.
As John A suggests we need to consider what mechanism might have brought them here (other than the ex-captive option). One possibility is 'moult migration' which is a phenomenon known in Europe for (at least) Mute Swan, Canada Goose and Common Shelduck. Moult migration routes can be counter intuitive to us (e.g. large numbers of Canada Geese breeding in southern England fly several hundred kilometres north to winter in the Beauly Firth in northern Scotland in late summer); I will do a bit of research as to whether this is known for Greylags and Aythya ducks;
Conversely, I am not sure that we can assume that all ex-captive waterfowl will show (obvious) signs of cage damage. In Europe and North America this is rarely the case as the individuals are generally well cared for (hence the relevance of the bread test). I do not think it unreasonable to hypothesise that ,with increased wealth and education, captive waterfowl in collections in China might be well cared for too. We may have to abandon the assumption that ex-captive waterfowl in Hong Kong will show obvious signs of previous captivity.
Perhaps this is something that Forum members can help with - what do we know about waterfowl collections in China, in parks, zoos etc? It would be useful to hear what members have seen on visits to the mainland.
Mike Leven
