I am new to chicken keeping. I have one Bantam rooster, one Polish Bantam hen, and one Easter Egger hen. My husband and I have been letting all three out into their run most days. We live in Wisconsin, where the temperatures have ranged from 10-40 degrees over the month. Yesterday, we noticed our little Bantam rooster had what appears to be a bit of frostbite on his comb. So, I'm wondering, when should we keep them inside their coop? I'd like to let them out as often as possible as I can't imagine being cooped up is any fun for them, but I don't want them to get frostbitten or sick. Also, I've read that oftentimes frostbite results from humidity. Besides opening a coop window or door, how does one better ventilate the coop? THANKS!