Corey over at Lovely,Dark and Deep has an interesting picture here of an immature swan and he - not the swan - isn't entirely sure about the bird's specific identity.
Sure enough, it looks very much like a Mute Swan but some things about the bird's bill structure and colouration do appear a bit strange.
I am not going to make an attempt at saying here what it is by just having seen one picture of the bird but I thought it might be useful to put up some pictures of Mute Swans I took at the end of February 2006 in Stralsund on the German Baltic coast.
The first two pictures are of a bird in its second calendar year. The plumage is still largely grey brown and looks dirty. The same goes for the bill which looks dirty pink, as if it was rubbed in coal dust.
Note the very pointed tail which is a unique feature of the Mute Swan and often much better suited to distinguish between immature birds of the different species than bill colouration.
Next up is a picture of two adults with one third calendar year bird on the right and a cropped version showing only the head of the immature (and a Mallard). You can distinguish it from adult birds by its paler colouration which still is more pink than orange (as it should be for an adult bird). The plumage is completely white as in adults but some show a few single brownish feathers here and there.
And here finally a nice and crisp adult with a bright orange bill.
Common maybe, but pretty nice as well.