Harlequins are delightfully coloured, compact sea ducks. After wintering out at sea harlequins gather in large flotillas at river mouths before exploring upstream for breeding sites. Their preferred habitat is fast-flowing rivers and streams, where they seem to be perfectly at home among turbulent currents. Once summer is over harlequin ducks return to sea until the following year, when the ascent of swift rivers begins once more.

The remarkably flashy plumage of a male harlequin gives rise to both its common and Latin names. Harlequins were medieval court jesters that dressed in brightly coloured costumes, and histrionicus is derived from "histrio", the Latin term for stage player.