(in tennis-watching mode below...)
I think the (male) Common is flightless too, though I'm guessing that's just because it's doing normal duck moult. I can't even speculate on what left it stranded in southern Lake Michigan.
The two stuck together but the (male) Common was somewhat aggressive towards the smaller
(8/3/15) one last pic of the female that in retrospect also has a much cleaner delineation between the head and the breast than a Red-breasted would have.