Subject: Age of Chinese Pond Heron [Print This Page] Author: badesc Time: 10/07/2012 18:40 Subject: Age of Chinese Pond Heron
Can anyone tell me if this Chinese Pond Heron is an adult in winter plumage or (perhaps more likely) an immature bird? And why? The photo was taken at Mai Po at the end of June[local]1[/local].
Just a guess: juvenile. Plumage very fresh, and head slightly redish. Author: 9Wi Time: 10/07/2012 22:37
Dr. CHEUNG, following picture was taken on 2011-11-05 at TBT, I think this juvenile is younger than the first picture taken by badesc, as it's bill is still in dark colour. Please correct me if I'm wrong. Thanks.
Author: ajohn Time: 11/07/2012 08:39
It will be difficult to say for sure which is older or younger. Both a juveniles (i.e. birds which are in their first set of true feathers) and both will have hatched and fledged this year.
Probably the best indicator of age in Chinese Pond Herons is the pattern of the wing coverts. In adults the wing is mostly white, in first year birds there are extensive dark areas in the coverts. This is very obvious in Bart's first picture (notice how the wing looks mostly brown), and is also visible in 9Wi's picture. Also, juveniles tend to have finer streaking or spotting on the head than in winter-plumage adults - again, these two birds show this well.
I haven't really looked closely enough at bill colour to know whether that indicates age, but it does vary during the year. Author: kmike Time: 11/07/2012 10:53
To provide some context . . . the breeding adults in Lam Tsuen all still have the red breeding plumage on the head, neck and breast and a black back, although it is beginning to fade - the juveniles all look brown.
Cheers
Mike Author: 9Wi Time: 11/07/2012 17:58
Thanks, John and Mike. Author: badesc Time: 11/07/2012 18:55
Thanks to everyone for their useful comments! So a juvenile it is.
Bart Author: ajohn Time: 12/07/2012 08:41
Mike's comment is correct in that almost all Chinese Pond Heron adults seem to go into breeding plumage, and most are still in full breeding plumage. This will certainly be the case around breeding colonies.
However, Deep Bay seems to have a very small non-breeding population (first summer birds?) which have not gone into full breeding plumage, and some of the finished breeders seem to have started moulting back into non-breeding. After breeding has finished, separating non-breeding adults from juveniles becomes very difficult, if the pattern of the coverts is not seen. Author: wcaptain Time: 12/07/2012 09:58
In this time of yr, most breeding adults around nesting colonies should still have breeding plumage. So, it should not be a breeding adult.
Quite unlikely to be a newly-fledged juvenile. The plumage is too tidy.
It is known that newly-fledged pond herons (squacco heron in France) could be back to their birth place (nesting colony) in their second calendar yr (sexually mature enough to breed), so I guess it could be a first calendar yr bird.
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