I only shot 1 canvasback and that was in Louisiana 43 years ago when I was 17 years old, since then I only saw 1 in flight on one occasion a few years after that one kill. From what I remember a mature bird is fairly white in body plumage, especially on the back (breast is black of course). I would agree with the consensus that you have a young bird. However I also fully agree that any canvasback taken is a big event, I had no idea they were this far West (as I recall they are fairly prominent in the Chesapeake Bay area). I can say this for sure...it is one of the best tasting waterfowl.
Do you know why Cajuns don't hunt elephants? Because the decoys won't fit in their pirogues!