An unusual duck of alpine lakes and mountain streams. Very distinctive elongated shape with yellow bill, dark head, strong barring on the body and a pointy tail which is cocked when startled. In flight, it has a green panel in the wing bordered with white. It swims with a distinctive head-bobbing motion and feeds by dabbling and diving. It is a strong swimmer and can also do agile leaps onto rocks. Usually silent, but occasional gives a quack or series of “whip-whip-whip” notes.