The Collaborative International Dictionary of English v.0.48:

greenwing \green"wing\ n.
   The common teal (Anas crecca) of Eurasia and North America.

   Syn: green-winged teal, Anas crecca.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Teal \Teal\ (t[=e]l), n. [OE. tele; akin to D. teling a
   generation, production, teal, telen to breed, produce, and E.
   till to cultivate. The English word probably once meant, a
   brood or flock. See Till to cultivate.] (Zool.)
   Any one of several species of small fresh-water ducks of the
   genus Anas and the subgenera Querquedula and Nettion.
   The male is handsomely colored, and has a bright green or
   blue speculum on the wings.
   [1913 Webster]

   Note: The common European teal (Anas crecca) and the
         European blue-winged teal, or garganey (Anas
         querquedula or Anas circia), are well-known species.
         In America the blue-winged teal (Anas discors), the
         green-winged teal (Anas Carolinensis), and the
         cinnamon teal (Anas cyanoptera) are common species,
         valued as game birds. See Garganey.
         [1913 Webster]

   Goose teal, a goslet. See Goslet.

   Teal duck, the common European teal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Anas crecca
    n 1: common teal of Eurasia and North America [syn: greenwing,
         green-winged teal, Anas crecca]