I am expecting some chicks in a week and i was wondering how cold hearty they are. I am going to be putting them in my garage in a brooder with a heat lamp. I will be making a tractor for my pasture when they are ready. I am wondering how cold resistant they are when they get all their feathers. I will build a heated shelter if i need to but i would like to use a tractor with coverage. I live in Colorado and the winters can get to 0 sometimes. Thanks in advance!