When ever you hear a bunch of crows making a racket,
they are usually either harassing a hawk or their mortal enemy
the owl.
I've also seen them after baby squirrels in large groups too.
I had a small screech owl, "Hooty", and a pet crow, "Joe" when
i was younger and they never did get along.

Hooty was in a large screened
cage, Joe was always free and wouldn't leave the neighborhood.
However every morning he would sit in the maple tree above the
owl's cage and squawk for 10-15 minutes.
