The Shoveler has similar colourings to the Mallard, especially the female, but the male's white and tan body is much more striking. If you're in any doubt though, their very broad, long bill makes it clear. However, their bill is not always visible as they spend much of their time either sleeping, or feeding, by 'shovelling' under water. The ones below were on the North Pool and are probable females (although males in summer eclipse can look similar). The second photo is a male, in the spring. He was in the Budge Fields, where there are usually plenty of overwintering Shovelers.