I suspect this is something unusual:
http://waarneming.nl/foto_details.php?id=284471 (http://waarneming.nl/foto_details.php?id=284471)
could be either new Zealand scaup x Tufted duck ? or a backcross (Tufted duck x ferruginous duck) x Tufted duck?
What is wrong for Greater Scaup x Tufted Duck? Too brown, too short-bodied?
Date of photo would make this a male in full breeding plumage?
Or at least, if it is not moulting regularly, there should be at least some white flank feathers if it were tufted x scaup sp.
however head looks as if it is already in full breeding- so i think it is unlikely to be tufted x scaup.