Swan Goose Anser cygnoides
Swan Goose is an Asian species which was domesticated many centuries ago. Domestic birds are dealt with separately - this page is for wild-type birds which so far I've only photographed in captivity.
captive Swan Geese, Martin Mere (Lancashire, UK), 26th December 2014
Some of the following birds show a small amount of orange on the bill. I am not clear if this ever occurs on wild Swan Geese (I've not seen it on photos taken in the wild in their natural range) but there is no other evidence of hybridisation so my working assumption is that these are pure Swan Geese.
captive Swan Geese, Pensthorpe (Norfolk, UK), 9th March 2014