Chickens also eat less exciting foods, like vegetables, fruits, flowers and grass. They eat grains and seeds. They scratch the ground and find bugs and specks of things that we can't see. So, the question isn't really what chickens eat, but what the right diet is for them.
Similarly one may ask, what you shouldn't feed your chickens?
Tomato, pepper and eggplant leaves As members of the nightshade family, they contain Solanine, just like potatoes, so you should try to keep your chickens off your plants. They can, however, eat tomatoes, peppers and eggplants. Avocadoes – The pits and skins contain the toxin Persin, which can be fatal to chickens.
What food is toxic to chickens?
Don't give chickens any edible containing salt, sugar, coffee, or liquor. Uncooked raw or dried beans contain hemaglutin, which is poisonous to chickens. Raw green potato skins contain solanine, which is poisonous to chickens. Onions are a poor food to give to chickens because onions flavor eggs.