Sometimes birds get aggressively protective of their cage (house). If your bird is trained to be outside the cage sometimes, he'll be friendlier when on your shoulder or finger. My cockateil was like that. He'd get so mad when I'd touch his house, but was fine once he was off it and on my shoulder.

Parakeet name jack I have had for 2 months liked me for a week and now when I put my hand on the cage he makes this squawking sound and bites me not in a nice way it used to be soft now its hard what do I do