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:

Bewick - music from the Tundra

I live in an area of Dutch lowland polders with a lot of grasslands containing much protein. As a green dish for thousands of geese and hundreds of swans every winter, the Alblasserwaard is an important wintering area for much waterfowl. Probably the most elegant appearance is the Tundra or Bewick's Swan Cygnus bewickii. The Netherlands is the most important wintering place for this arctic species with more than 60% of the world population of 15.000 birds. The species has underwent a substantial decline in the past years and is evaluated as vunerable by Birdlife.

Tundra Swans (Cygnus bewickii) - polder Wijngaarden - 25/12/2011  In the center neckband yellow 062E.

Hence, it is important is to gather information about their survival rate and breeding success. Simple observers like me can help by counting juveniles and reading codes on their neckbands. The last two days, I spent some time to count juveniles and search for neckbands. On Saturday, I counted an amount of 18 juveniles amongst 235 adults (n = 253), a percentage of 7,3%. Today I counted 23 juveniles in some flocks with 185 adults (n= 208): 11%. Too low for a stable population and conform the numbers of a recent international sample, coördinated by Wim Tijsen and Jan Beekman (Kleine zwanennieuws 2011-2012 (6)). They collected data from up to 60% of the population (n=8382) and counted a juvenile percentage of 9,2%. 

Tundra Swans (Cygnus bewickii)- polder Ganzenwei, Brabantse Biesbosch - January 2011

But, the swans continue making music. They keep performing lovely ceremonies acommpanied by their jubilant sounds........ I hope they will never surrender. 

Tundra Swan (Cygnus bewickii) - polder Wijngaarden - 30/11/2010

Tundra Swan (Cygnus bewickii) - polder Bleskensgraaf - 17/12/2011