It was only yesterday that I had a chance to look at my pictures from that day, and I was really struck by how different this bird looked. I sent the pictures to two experienced birders to have a look. Because the pictures are so poor, it is taking a while to get an ID. In the meantime, I thought I would share the mystery bird so that if anyone sees it again, it can be photographed better than I did. I will keep you updated if the bird is identified.
Click to enlarge.
It turns out this is not a raptor at all but a Raven, likely carrying something red in its mouth. I guess that is why is was being pursued so vehemently by the crows. This kind of excitement, followed by deflation, is not uncommon. Thank you to everyone who looked at the shot and offerred suggestions. It did turn out to generate some good study and discussion.