I'm new to having a bird and I had some trouble with Mort (Nanday conure) being aggressive at first, especially towards hands. He's warmed up to me and especially my dad and he has started rubbing his beak against our fingers. He will come up to our bent knuckle and rub the side of his beak against it. He almost vibrates his head up and down pretty fast, and once in awhile he will do it against his favorite rope toy. I just want to make sure this isn't a different aggressive behavior. He doesn't show any other signs of aggression when he does it. Thanks in advance!