So here's Joe's stupid question of the day. (I'm going to limit this to one thread after good advice from SG)

There's a plethora of pigeons (that means a flock) that fly around outside my living room window. I love to watch them swoop and dive. But do they ever crash into each other, and one ends up with a broken wing? Or do they have an innate sense of distance, and keep just far enough from their mates to avoid a collision?