I gave my broody BO 9 chicks about 10 days ago. After the first 5 days, we moved them all out of the coop and into a corner of the run due to space issues. She has been doing a great job of keeping them warm. We've had several warmer days, especially last weekend when we moved them into the run, but now had some frigid nights and were a bit worried how the biddies would do. Well, last night it snowed (unusual for us), so we broke down and added a heat lamp to the pen area, but Mama is still tucking them close when they want to warm up and letting them run around and eat and drink for a few minutes in between. After raising our first batch of chicks in a brooder in my home, this is amazing to see just how hardy chicks are and how a mother hen and chicks all have the instinct to make it work even in colder weather.