Confidence: I'm as sure as I can be.
Notes: Scott I found a dead mallard drake on the coast road last Friday. This feather is from immediately below the secondary feathers of the wing (the irridescent blue secondaries). Having compared it with yours, they are similar to a degree but not identical. I think your feather still looks like it belongs to a duck but as it is so much more robust than this one, possibly from the dorsal surface of a ducks wing, cant be more specific as regards species at this point. I didnt find a feather to match yours exactly on the mallard drake.