Hello, i've had my cockatiel for two months, he's 7 months old and he responded good so far to training. I've seen him doing some beak banging but i read that is normal in their behavior. He never really bite, just when he's sleeping and he doesnt want anyone to go near him. Recently he started to bite me, but he doesnt want really to hurt just like he's mad or annoyed about something. So the point is my mom bought a green check conure, and seems like he started being more "aggressive" and doing beak banging more frequently he does it on my hand too. He's still responding good to my training.
Youtube link to behavior
Youtube link to behavior 2
Youtube link to behavior
Youtube link to behavior 2