I've heard a lot of GCC owners say that their little guys went through a "terrible twos" phase, but they do become sexually mature around the 1 year mark, so that could be it. It could be a lot of things though. What's his diet like? Has he been getting enough sleep?
If this is about him becoming hormonal and an adolescent, you just need to make sure that you stick to the training and behaviors you've established so far. Michael's guide on getting a bird to step up could be really helpful. You just need to make sure never to react to him when he gets you (because any kind of reaction could potentially encourage it) and not to immediately leave after he tries to bite. If you leave him be after he's bitten/lunged, you just taught him that it's an good way to get some privacy. In Michael's guide it talks about not leaving him be until he's calm
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