I was in my yard watching my cockerel and my pullet (the two on the very bottom of the pecking order). They were about 20 feet away from the rest of the flock looking for tasty eats. A pigeon decides he wants to eat in the same area. The cockerel isn't going to have it. He goes after the pigeon with an intent to kill, said pigeon flies away looking for easier eats. Several minutes later, one of those little whatever birds gets the same idea. The cockerel runs it off the first time, but the little bird is persistent. The pullet then spends the next 1 1/2 to 2 minutes chasing this little bird until it decides the meal is not worth it and flies away. Maybe a part of the pecking order is running off food competitors. What do you think?