The red-breasted merganser (Mergus serrator) is a diving duck, one of the sawbills. It has a spiky crest and long thin red bill with serrated edges. The male has a dark head with a green sheen, a white neck with a rusty breast, a black back, and white underparts. Adult females have a rusty head and a greyish body.
The fastest duck ever recorded was a red-breasted merganser that attained a top airspeed of 100 mph while being pursued by an airplane.