We are hand training our new bird. He/she doesn't mind climbing on my finger, but she's very interested in tasting, then nibbling, then biting/chewing on my finger or thumb. It doesn't seem like fear of threat, just enjoyment. How can I correct this behavior so he/she will just be content sitting on my finger without chewing on me? She starts to bite harder and harder and I eventually just need to get her/him off!