Chickens will eat almost anything. I once saw a chicken grab a frog and swallow it whole. One of its legs was hanging out of her mouth the rest of the day. She was fine afterwards.

Eggs are also especially tasty to them. You can feed them cooked eggs (very nutritious), but if they ever get ahold of a broken egg and realize how tasty they are, they can start eating their freshly laid eggs before you can collect them.