I have the same problem with one of my girls, ironic that she was named Marvin by my tom boy step-daughter, lol. I try to handle her a lot but her pecks are much more aggressive than the curious pecks of my other girls. Even when I'm holding her though, she still has her head and neck stretched out like she is trying to be bigger than me. My girls are only 9 weeks old though so I think of it as kind of cute. I've never seen her be aggressive with the other girls, just me.