Gadwall n. : A large duck (Anas strepera), valued as a game bird, found in the northern parts of Europe and America; -- called also gray duck.

Example:


Taxonomy
Gadwall, Birds, Anas strepera, free encyclopedia, concern species, breeding, Systema naturae, family Anatidae, breeding range, Clements, Field Guide to the Birds of North America, California, juvenile, plumage, breeds, genus Anas, Floyd, Madge.

Defination from the web:
Gadwall breeds in the northern areas of Europe and Asia, and central North America. ... In Great Britain, the Gadwall is a scarce-breeding bird and winter visitor, though its population has increased in recent years. ...