Just about anything. We have 7 hens (newly aquired this spring as chicks) They especially love clover and alfalfa from the pasture. Everyday my daughter and I grab a few handfuls and toss them on the ground in their run. They really love the purple and white flowers. Our pasture grass (Timothy and Orchard) is going to seed right now and one of the other things we do is gather a bunch of it together and tie it in small bundles, hang it up about six inches from the ground with the seed pods facing downward. The chickens have a great time stripping he seed from the stems. After it rains we always find worms crawling around and gather them up and toss them in the run too. My daughter calls it "Worm Attack" We have one hen that is especially talented at catching flying insects. Watched her jump about 3 feet in the air to catch a wasp yesterday and just this morning the same hen chased down a carpenter bee. So far the only thing the hens don't like is green beans.