I saw Maria tidbitting for her chicks (still together at 3 months) close enough to me this afternoon that I could actually see what she was encouraging them to eat, and was surprised to find it was mushrooms. Not whole ones or standing ones, but pieces of caps of those that had been knocked off their stems and broken by passing feet (chicken or human). Looking it up, I see that they're quite nutritious, with a good range of B vits, tons of vit D, and plenty of protein including some lysine and methionine. I learn something new every day with chickens!