Plumed, male's neck ring divides green head from chestnut-brown chest. Speculum: violet-blue bordered by black and white. Bill yellow to yellowish-green. Legs: orange-ish; generally indistinguishable from hens. Hens: brownish with violet speculum bordered by black and white. Head crown dark brown surrounded by lighter brown. Bill: orange with brown splotches. Legs, feet: orange. Dabbles to eat. Appears larger in flight. Often flies before sunup.
Appear similar to scaup (bluebills), except that males have distinctive white bill markings and uniformly dark upper wings. Hen ringnecks resemble hen redheads but are smaller, with a peaked, angular head and pale region around the face. Bill ringed, like males. Diving duck. Flies in small knots. Might land without circling.
Males wildly colored, with most plumed by opener. Even if not plumed, males identified by their head crests. Iris is red. Legs and feet: straw yellow. Females have smaller crest. Distinctive white teardrop patch surrounds brownish-black eye. Bill is gray; legs and feet, dull grayish-yellow. Dabbles. Distinctive wing beat in flight.
Males: Black-edged white crescent in front of eyes (when fully plumed, otherwise sexes are similar in appearance). Most upper wing coverts are blue-gray; secondaries form iridescent green speculum. Bill: black. Underwing: whitish. Females: brown-gray heads with darker crown and eye stripe. Upper wing coverts are bluish but duller than drakes. Bill: gray-black. Legs, feet: dull, yellow-brown. Small in flight, and fast. Often appear in fast, tight knots.