So I have two cockerels. They have grown up together along with two other chickens (which I'm pretty sure are pullets). They were always well behaved and lovable. But lately, and especially today when I let them into the yard, I've noticed that they're getting very aggressive towards each other and the pullets. They are not aggressive towards me however. Melon (named because he likes watermelon) is below Roos (the other one) on the pecking order but he is always instigating the fights. I've noticed that this doesn't really happen as much or on this level when they are inside their run. Is there something about the open space that makes them more prone to aggression? What should I do about this, and if I were to re-home the two cockerels, would the other two be alright on their own?