Sorry for the terrible image quality, but I thought this was worth posting for the ID challenge. I originally thought it was a leucistic male Redhead based on its reddish head. Fortunately I took a photo. Notice the white around the bill, just like the other female Greater Scaup in the picture. There are very few pictures of leucistic Scaups on the internet, but I did find one of a leucistic Lesser Scaup that looks exactly like this, colour-wise.
This was taken today at the Leslie Street Spit, near the bridge. The same bird was present a month ago in the same location.