I'm new the chicken world. Our four 13 week old pullets arrived Monday, and since then we've noticed that they don't use their roost bar. At all. Both nights they've been huddled together in the corner of the coop on the floor. It's not cold out nor is the coop drafty. So should I do anything, or just let them continue to sleep on the floor...? I was thinking that perhaps the roost is too big (it's a 2" dowel) or perhaps it's not high enough off the floor (it's perhaps 18" high, but the coop is only 4 feet tall). Any other suggestions?