I saw this bird in the St. Clair River and am stumped as to what species it is, even after reviewing my Sibley Guide. What do you think?

I saw this bird in the St. Clair River and am stumped as to what species it is, even after reviewing my Sibley Guide. What do you think?

Here is a closer view of one of the Broad-winged Hawks I saw Saturday evening. You can see the distinctive white stripe across the tail as well as the black border on the wings.
I don’t remember ever seeing one before and had get out my hard copy of The Sibley Guide to Birds to identify it. Then I went to its entry at allaboutbirds.org to learn more.
