(Northern) Shoveler
Anas clypeata

This dabbling duck has a very large and flattened bill perfectly suited to doing what its name suggests. In fact, it can be quite hard to get a photo of one not shovelling. The first is an adult male, the next two are males in eclipse plumage and the fourth is a female.
 

Male (Northern) Shoveler  Male eclipse(Northern) Shoveler

Male eclipse (Northern) Shoveler  Female (Northern) Shoveler

1: Colebrook Lake, Moor Green Lakes LNR, 06/03/2006.
2-4: Colebrook Lake, Moor Green Lakes LNR, 08/10/2006.