Size: L: 60cm. Wt: Males: 1330 g. Females: 1160 g. Sexually dimorphic in size, and only slightly in colour. This species not seasonally dimorphic. The American Black Duck readily hybridizes with the Mallard (Anas platyrhynchos); intermediates have characteristics of both species.

Male: body blackish-brown; head and neck paler; purple speculum, bordered with black; bill yellow; legs orange.

Female: similar to male, but bill dull green, may have black marks.

Duckling: similar to Mallard, but darker on head and face; dark markings extend over more of body.

Note: American Black Duck-Mallard hybrids are common in some regions; they typically show characteristics of both species; males often have green and brown patches on heads.