Aging Bewicks Swans

Two years ago, I got an e-mail from Adri Clements about second winter Bewick's Swan.  Two years later, I have seen some birds he mentioned. Their plumage is slightly different from adults, since they have left some grey feathers in their neck and on their head. Also, the yellow part of the upper mandible is a bit paler. In good conditions, you can seperate them from adults. Unforntunately, I don't have pictures of second winters yet. But recognizing this plumage is important to measure the survival rate of the species. 

Still from 28 January 2012 -first winter

Another interesting thing is the difference in moult in first winter birds. They start moulting in December, beginning with the scapulars and underparts. Some birds still show an almost grey plumage at the end of the winter. Others have replaced up to 80% of the scapulars and most of feathers the belly and head. Have a look at this short video: