Laurie was out on the patio Saturday when she suddenly said "that's
why it's so quiet! we have a hawk". I popped out to look, and we had
hawk on the telephone pole in the next yard hanging out -- and total
silence around the feeder.
I didn't get a great look at it; it split as I was grabbing the
camera, but after wandering through Sibley's, I *think* it was a
Ferruginous. The most noticable mark I saw was that the breast
feathering was extremely pale, either a very pale yellow or white (it
was late afternoon, it was somewhat backlit). It was also a large
hawk -- definitely larger than a red tail, and larger than the
resident Coopers that live in the area. The general look matches that
of the "light juvenile" in Sibleys, however.