Well, not necessarily mean, but my roo (3 months old) is incredibly aggressive toward me. When he was in the biddy pin, he would go out of his way to peck at me (and trust me, it didn't feel good). We let them out yesterday because they're as big now as our other chickens and he was ok as long as he was in the bigger pin. So far. If he continues to be aggressive though, is there a way to break him of that?