I am a soon to be new chicken owner and wondering how much feed a flock of 12-15 chickens will go through per month? I will throw kitchen scraps and such, but want to know how to budget. They will be free range in a large back yard. I live in Wisconsin, so wondering how to do things in the winter as opposed to the summer. I really do want to have them eating as much natural as possible (not organic per-say...but natural) Thanks.