Thanks, all. It was nice, for once, to have a clear-cut identification - thanks to the hawk's hanging around and posing, flashing all of the ID tips. Usually I'm scratching my head and fussing over an ambiguous photo. Claire

Looks like a Coopers to me as well. I had one spend the day in the backyard on Saturday. Needless to say, I didn't much in the way of other birds. ;)

These guys are very sneaky in my yard. The only time I see them is when they are leaving one of my trees. I have yet to spot one while it`s perched in my trees. Very nice photo!

Yes, your bird was a juvenile Cooper's Hawk. Looked like a big, nicely marked one. Sorry it took so long for someone to respond; I hadn't checked this forum in some time. Cooper's Hawks are Accipiters and Accipiters are built for ambushing and chasing birds around and about. I have read they do occasionally take smaller squirrels (such as Eastern Gray), but the vast majority of the time they stalk bird feeders to take birds. The squirrel probably felt safe challenging the Cooper's for that reason. Had that been a Red-tailed Hawk hanging around, there may have been a different reaction by the squirrel....