Always choose the boy that is most respectful of humans and the other birds. A cockerel that respects your space and gives you room to do what you need to do around the coop is one that is worth considering keeping. Cockerels that are always running up to you could be birds that will take it one step farther, by charging and jumping to spur you. Cockerels that will jump on top of you the second you are still is not showing you affection, he is displaying dominance over you. What newbies see as cute and friendly, are usually precursors to aggressive behavior.
