The dept of the interior did an exhaustive report in 1992 called "Species, Age and Sex Identification of Ducks Using Wing Plumage".
I have a copy of it and its nearly impossible to find. I don't really care whether or not I'm breaking any copyright laws by posting these pics since it was our tax money that paid for the study in the first place.
The bottom picture is the description of how to age a Canvasback. You have to know your duck parts and wing elements but its pretty easy to look up anything you don't know on google.
The top picture is of a Mature Drake Can Wing. If yours looks simimlar, then you are in business. There are also pics of female and immature male wings. If you want them send me a PM and I'll send you a photo of them as well.
Hope this helps. If you can't read the text, let me know and I'll try again.
Internet Scouting Pro Staff