Budgies don't have a full moon. Why? There is a bald spot on the back and back. I wonder whether the mother bird or the young bird pecked each other off. Why?

Probably pecked by a big bird. Can you eat by yourself? Did you take this bird away from the big bird? If pecked by a young bird as big as it, most of its hair will not fall off. It should be a big bird. But it's okay, maybe it has poop on its head or something, and the big bird wants to help it manage it. Or make noise, watch and listen again, and nothing will happen without a particularly exaggerated scream. I wish them healthy growth.

I just saw the picture. It looks like a big bird. With mom and dad? Are there any other pippi in the cage?