The harlequin duck (Histrionicus histrionicus) is a small sea duck. In North America it is also known as lords and ladies. Other names include painted duck, totem pole duck, rock duck, glacier duck, mountain duck, white-eyed diver, squeaker and blue streak.
Adult breeding males have a colorful and complex plumage pattern. The head and neck are dark slate blue with a large white crescent marking in front of the eye that extends up to the crest, a small round dot behind the eye, and a larger oval spot down the side of the neck. A black crown stripe runs over the top of the head, with chestnut patches on either side. A black-bordered white collar separates the head from the breast. The body is largely a lighter slate blue with chestnut sides. The bill is blue-grey and the eye is reddish. Adult females are less colourful, with brownish-grey plumage with three white patches on the head: a round spot behind the eye, a larger patch from the eye to the bill and a small spot above the eye.