38-46 cm (15-18") Common. Wooded lakes, bays, ponds, rivers. Small diving duck with a distinctly ringed grayish bill. Questionably named for hard to see brownish "ring" on male's neck; Ringed-bill would make more sense.
Male: purplish-black head shows a peak in profile; thin white ring at base of bill and much wider white ring near tip; black back; white crescent separates black breast from gray sides.
Female: small, dark, gray-brown diving duck with a distinctly ringed black-tipped grayish bill. Head shows a dark-crowned peak in profile; dark eye with white eye ring; often shows a faint white line behind eye; light area on face at base of bill; white ring near tip of bill.
In flight: white belly; gray speculum.
Song: loud whistles, soft purring.