My son brought one of our 4 wk old mixed breed chicks to me to show me a small "claw" it has on it's wing. I thought surely it must just be a pin feather or a quill or something to do w/ feathers. But there really is a small little hook-like claw/talon on it's wing. It's at the bend of the wing. On both wings, and on more than one chick. What are these?