I have an 8 month old GCC. When I first got him, he was nippy (which was to be expected), but he eventually learned not to bite hard. Everything has been fine for about 4 months. He still loves being around me, being on my shoulder, etc. However, he has started having these very aggressive periods that I don't understand.
They seem to manifest themselves sometimes (but not always) when I open up his cage, whether it's to change the water/food, find out if he wants to come out to play, anything like that. He will scramble from wherever he is in the cage up to the perch right by the cage door like he does when he's excited about coming out. Except when he gets up to the cage door, he sits on a perch and glares at me. When I reach in, his head goes forward like he's going to step up, except then he bites. HARD. Even if my hand isn't going near him, he goes to where my hand is and attacks it. This never happens outside of the cage, and it does stop if I can get him to come out on his own.
I've heard of cage aggression, but I'm not sure if this is it. It doesn't happen all the time (the only pattern I've noticed is that it happens more often than not if he's been dozing), so I'm not really sure what's triggering it. Could it just be the change in weather since it's winter here? Or the fact that he's close to a year old and going through a phase?
I have an appointment with the vet later this week to get his nails trimmed and I plan to ask about it, but was wondering if anyone here recognizes this behavior and can give me some tips (before the bird bites mine off