My family has a 45+ year old double yellow headed Amazon parrot. He belonged to my great grandmother and came to us 5-7 years ago when she became too sick to care for him. He is nervous and aggressive towards everyone but my mom which leads to him spending most of his time in his cage. I just feel bad that such an intelligent, beautiful creature is spending all his time in a cage (it's a big cage with lots of toys, but still). I've tried to "make friends" with him, sitting outside the cage talking to him and offering him bites of the fruit I'm eating, but whenever I open the door to the cage (even just to change his food or water) he charges and bites at me. I think this is out of territorial instinct or fear. Outside the cage he will make noises at me and take food from my hands, but if I move in a way he doesn't like or get too close he will bite at the bars. Is there anything I can do, or is he so old that the ingrained behavior is probably unchangeable?