The Harlequin Duck Histrionicus histrionicus is a small, relatively uncommon sea duck. It gets its English name from characters in Italian comedy that wear masks and have oddly painted costumes. The colourful male, or drake, is one of the most attractive of sea ducks. At an average weight of less than 700 g for males and less than 600 g for females, the species is roughly half the size of an average Mallard.
From a distance, Harlequin Ducks look black or dark grey and can easily be confused with more common sea ducks, such as scoters. At close range, however, the adult male is striking and brightly coloured. It is characterized by slate blue plumage, chestnut flanks, and streaks of white on its head and body. The most distinctive markings on the head are a crescent-shaped white patch at the base of the short bill and a round white ear patch. The belly is slate grey.
Females and young birds lack the lustre of the drakes. The female has plain, brownish-grey colouring that is darkest on its head, a white patch extending below and in front of each eye, and a prominent white ear patch. The belly is white with brown speckles. Young birds strongly resemble the adult females. They have the white spot between the bill and eyes, as well as the prominent round ear patch. However, the feathers on the upper body of the young are darker than those of adult females, and the belly is more finely barred, giving an overall greyer appearance. The young males achieve some adult features during their first winter, but do not grow full adult plumage until two or three years of age.
Seen from afar, Harlequin Ducks can be distinguished from other sea ducks by several features. They have slighter bodies and shorter bills than scoters, and they raise and lower their heads and nod while swimming. The birds are also normally found in smaller flocks and closer to shore than other sea ducks. Female and immature birds do not have the white wing patches found on Buffleheads and White-winged Scoters.
Signs and sounds
Harlequin Ducks are also known as "sea mice" and "squeakers" because of their mouse-like call.