Gadwall
Anas strepera

A moderately common duck, they are about the same size as Mallards. Pictures 1 to 3 are males and 4 is a female, nicely displaying her wing bar.
 

  

  

1: RSPB Radipole Lake, 25/05/2009.
2: Moor Green Lakes, 12/05/2006.
3: Baron’s Haugh RSPB reserve, Motherwell, 19/06/2005.