If the chicks are under a broody hen I don't see why you would need lights or any heat. I have chicks that are just a little older than these pictured and they are doing fine. On the colder days I just haven't let them out. By colder I'm talking about 20° F I think we even had over night temps into the teens. By the time the real cold hits they should be big enough to handle the cold in a draft free coop. My chicks are now in with the coop with the chickens.
Beautiful chicks
