While birding at Great Kills Harbor a couple of winters ago, my friend and I found and photographed what was then identified as a Brewster's Duck. Unfortunately, those images were lost during various computer changes.
Luckily, on Friday, January 15, 2010, while birding at Great Kills Park I stumbled upon what I believe is the same bird. This belief is based on the head pattern/markings, to be discussed below.
The overall size, shape and patterning of the bird clearly reveal its Mallard parentage. The silvery tetrails, bicolored bill, square shape of bill, maroon head with green through the eye and extending to the nape, and uneven divide between the brown breast and gray flanks are suggestive a Gadwall parents.
Same as above, from different angle.
The silvery webbing of the long tetrials and scapular of the gadwall are clearly seen in this image.
Perhaps the most telling image. The gray, not white outer tail feather, and the white inner secondaries are features of the gadwall parentage.