Gadwall

Anas strepera

female (on left) / male (on right)

Appearance:
Medium-sized dabbling duck
White speculum (wing patch)
White belly
Dark bill
Male: 
     Finely barred grey plumage
     Black rear end
Female:
     Light brown and buff plumage
     Orange-edge to bill

Listen to its call.

This pair were enjoying a sunny April afternoon at the London Wetlands when I snapped this picture.  Again, if you haven't been there yet, I would highly recommend it.  It's a treat to find a nature reserve in the middle of the city.

Learn more about the Gadwall.