So a few other birders who know more about raptor ID than I do have come to the conclusion that the bird I photographed in Leamington the other day is most likely a juvenile Red-tailed Hawk, not a Swainson's as I had originally thought. Some ID features include the dark patagial bar that is somewhat visible on some of the lightened photos, a faint belly band, and relatively broad wingtips. I am not sure why the bird appears to have dark flight feathers but it may just be an artifact of the light!
To be honest when I first observed the bird, it did not give me the impression of a Red-tailed Hawk. It seemed too long-winged, narrow-winged, and long-tailed (plus of course the two-toned wing that recalls Swainson's Hawk). But, it was a very brief field observation (that was backlit) and so I am not sure how accurate my impressions of the bird in the field were.
Right from the start, I had problems with the faint belly band that was visible and the relatively broad wingtips. I convinced myself that the belly band was an artifact of the bad light, but I couldn't justify the broad wingtips. Swainson's Hawk is supposed to have relatively pointed wingtips - like a Broad-winged Hawk with longer wings.
At any rate, that's the way it goes sometimes. Here's hoping the next SWHA that I call is actually one.
I guess that's how you learn right?