My chicks have been outside for close to 3 weeks now. I don't run a heat lamp. There are 7 of them in a fairly small coop. Yesterday we had our first freezing temps and I checked on them throughout the day, added scratch, full of cracked corn to their feed, added about an inch or more of fresh bedding to what was already there and changed out their waterer every time it froze. This morning it's 13 F outside with a high of 21 and a low of 7. Tomorrows forecast looks the same. Should I bring them in overnight when the temps will get their coldest? Right now (when dh checked and replenished their water) two were roosting and the rest were scratching around, eating and exploring. We've also considered throwing a tarp over the coop to provide more insulation for these cold days and nights and I'm taking down a smaller box filled with shavings to provide them with a tighter space and added warmth. Running heat to the coop is not an option so if anyone has more suggestions I'd love to hear them. So...what should I do? Bring them in? Leave them out? I'm a nervous chicken mommy.