I have a cockatiel who hatched in an Avery but only got a bit of partial handling before he came to me. He loves to be with me but he hates my hands and will hiss and bite if my hands come near. He will only step up if he’s outside the cage and recognises I’m helping him back to the cage. He will take a sunflower seed from my fingers inside the cage but if I try to get him to step up inside the cage he runs away. He is now about 6 years old is there much I can do to get him comfortable with my hands?