Hi John,
I never mentionned 57 000 ducks, I written birds, of wich a part of them could be have been duck.
This was for a single campaign, but I know that the identification dpt from The South China Endangered Animals Institute is sollicitades regurarly to ID birds that has been seized indeed birds are seized and released all the year round.
"Why do we not see similar summer records with the other species you mention (Red-crested Pochard, Baikal Teal, Scaup)?"
1st HK Red-crested Pochard turn up in HK in march 2013, just after big campaign and market crack down in Guangdong following the story of the poisoned stork in Tianjin and various reportage concerning bird market around Guangzhou. We notice rare birds, but do not common species....Does necessary all of them ended at Mai Po.
What would be the behaviour of a Red-crested Pochard or a Ferruginous that has been raised since several generation and then released in the wild? My guess is that they would stay at a not too far distance from where they have been released.
Short distance movment of birds at this time of the year can be easily explained as they usually have stayed at a place to complete their mould with a period during wich they can't fly.We can easily imagine that some place they will have choosen for moult could have changed due to heavy rain...., then once moult is complete the bird has to moove to find more suitable habitat...
"Finally, why do these birds not show any sign of damage to plumage or bare parts?"
As said if raised in small pool then why should they show any more damage than a wild bird...Since these bird just complete a full body moult, it is very unlikely to find any feather damage...
To conclude, in my opinion all this recent event with illegal market and better law enforcement concerning poaching, as well as increase of demand concerning waterfowl for delicacies has a better chance to explain the occurence at various time of the year of different species known to breed at several thousand kilometer away of HK, rather than by an hypothetical unknown behavior. Even I agree that every hypothesis has to be kept in mind...
If you would see a Chinese Pangolin swimming accross Deep Bay, you would have immediatly the same reaction as I does for these birds...(just joking)...
All the best,
Jonathan