It appears as though all my 12 week pullets have started using the perch, which is about 3-4 feet off the ground. Because our nights have still been cool, I have kept the heat lamp in place over any area of the floor. I did this because when they are ready for sleep, they just naturally huddled together on the floor of the coop. I also hadn't yet seen all of them on the perch, so wasn't sure if they had the hang of it. Is it time to place the heat lamp over the perch, so that the are encouraged to sleep on it? Or, at 12 weeks, is it better for them to remain sleeping on the floor?