Whooper swan
Cygnus cygnus

This swan is the national bird of Finland and a winter visitor to the UK. They are much more vocal than the Mute Swan (they are named after their call) and have a yellow bill without the knob. They are also larger than Bewick's Swan with a longer neck and less black on the bill.
 

  

1-2: Lochwinnoch RSPB, 20/03/2005.