carwreck.com: around Boston harbor...

A visitor in our back yard. My brother thinks it was a peregrine falcon but I think it's a sharp-shinned hawk because it didn't have the black marks below its eyes that the falcon should have and it had the sharply squared tail-feathers that the hawk has. Anyone have other ideas?

Definitely a Sharp-Shinned hawk... it could also be a Cooper's Hawk (I think that's what it's called) but due to the very square tailfeathers I'm gonna agree with your original assessment.