I might not have a clue what I am talking about, but I noticed that all chicks have some sort of hole or spot like that (although small) where their umbilical cord was...or whatever attaches them to their yolk or whatever...I'm assuming it's like an umbilical cord since I've never studied the anatomy of a baby chick.
To me, it looks to be in the exact spot where that is when they are babies, and maybe some just get infected or whatever. All of my chicks have them, and they all have like hard, dried stuff attached to them. I'll have to go check the bigger birds, maybe some heal up well like our belly buttons, and some maybe don't heal as well. Any thoughts on this anyone?