Notes:
drake in breeding plumage is a striking little duck with a green-patterned head; non-breeding drake (in eclipse plumage) and hen are a much drabber brown overall.
green speculum; plain grey bill (Zoo; 2012-10-09)
slight hints of green on the head (Zoo; 2012-10-09)
drake in eclipse plumage; resembles the hen (Zoo; 2012-10-09)