Male ducks are easily identifiable by their colourful, iridescent plumage. After breeding, the drakes lose their colourful feathers and don their so-called eclipse plumage. During this time, only the yellow bill can be used to tell them apart from the females.
Drakes do not have a brown mark on their bill, unlike females.
Dimensions: 1.7 x 1.2 x 1.9 inch (W x D x H)