In the long term, they need fairly high protein content food with certain nutrients, including amino acids. Specific feeds, like corn meal, ground wheat, oatmeal, or that rice do not give the overall balanced diet they need, but it certainly can be used short-term in a pinch. They'll do OK on the 16% Grower from Day 1, but they really do better with a 22% or so chick Starter for the first 4 to 8 weeks.
If you let them totally free range on good quality forage, which means different grasses and weeds, different grass and weed seeds, places to scratch and find various creepy crawlies, and some flying or hopping insects to chase and catch, they really don't need any additional feed. Mama will take care of that. On a backyard lawn that is only grass and is never allowed to go to seed, the quality of forage does not meet my standards for not supplementing them. It's great for them to have access to that lawn, but they need supplements. It never hurts to supplement free ranging on good quality forage with good quality feed. In the short term, the individual foods are fine, but in the long term, they need the protein, fiber, fats, minerals, vitamins, and other nutrients that come from a balanced diet.
We really didn't know when they'd hatch! 
