Hello! I've recently gotten two new cockatiels about two weeks ago, Rocky and Yuzu. As I've tried to interact with Rocky, however, I've noticed that he's super aggressive. He doesn't run away, I think he might be territorial? But I've tried leaving my hand in the cage for him to bite to show that it won't harm him, but as he bites he eventually gets on and starts humping my hand. My friend was over when this happened for the first time, and she noticed it immediately and I put him down immediately. I know I shouldn't let him do this, but every time he gets on he just does it? I know that birds can sometimes see you as their mate, but why is he so aggressive with me? How can I stop this behaviour?