When you see adorable little birds snacking on seeds at your bird feeder or flitting about like they're sewing a dress for Cinderella, don't be fooled. Those birds will gang up and turn on you in a tiny, fluttering heartbeat.
When birds detect a predator, they will start "mobbing" it. It's when small birds join together to fend off a larger bird. Small and large are relative terms here. Crows will band together to mob a hawk, and starlings will come together to mob a crow.