Crows are damn smart. When I was a kid, I used to try to shoot them in my backyard with a cheap crossman pellet gun. After one or two shots, they knew exactly which tree line they could sit in without being hit... and they would sit there and sit there squawking at me. So, I saved up a few weeks of paper route money and bought a really powerful pellet gun, and nailed two of them when I got home. That pushed them back another 50 yards or so.
When I was growing up there was an old man in my neighborhood who had had a pet crow for fourty years (like Brooks in Shawshank Redemption). He had taught the bird to talk like a parrot.