It has been occasionally reported as a male Scaup but it's more likely to be confused with Lesser Scaup although with views like these it shouldn't be a problem.
The extensively black-tipped bill and grey back with fine black vermiculations separate the two. Lesser Scaup has just the nail of the bill black and the back is white with coarse black vermiculation.
You can see these differences on the Lesser Scaup photographed at Ogston in March 2013, click the link and view below.
|Tufted Duck x Pochard male hybrid|