Size: L: 35cm. Wt: Males: 450 g. Females: 330 g. Sexually dimorphic in colour, and also somewhat in size. Males of this species exhibit eclipse plumage.
Male: head large, puffy, dark, with large white head patch; bill gray with black tip; breast and belly white; back blackish, with white shoulders.
Female/Eclipse Male: head dark brown, with elongate white patch; breast and belly whitish; flanks pale brown; back dark brown.
Juvenile: males with elongate white patch, larger than in female, with less distinct edges.
Duckling: downy; blackish-brown above; white patch on cheeks and throat; white below; similar to Common Goldeneye, but smaller.