The female is all brown, with the same bill, and with a semi-circular white crescent just behind the bill. Greater scaups are larger, have rounder heads with a greenish gloss and longer wing stripes. Both are divers, seldom seen in marshes. The bluebills have had the most liberal hunting limits of any duck over the last 50 years. The Green-winged Teal is a very small duck of the wetlands and small lakes or rivers.
Males show a distinctive white stripe on the body and a green eye patch, otherwise being brownish.
Female is brown speckled with a small green speculum behind the wing at rest. Occasionally breeds in Saginaw Bay region. Easy to confuse with Blue-winged Teal, which lacks body stripe but male has white crescent ahead of eye and both sexes show blue patches on wings. The Mallard is the most widespread of all the ducks. Easy to distinguish by the bright green head, white neck ring and ruddy breast.