Hi all, I am moving my first backyard flock into their coop today and want to know if I need to put a heat lamp in at first? The chickens are 10 weeks old and are hardy breeds. The overnight temps are averaging around 30 degrees. The coop has a deep pile of pine shavings and is a 4 by 6 structure with 2 vent holes that measure 4" by 12". Thanks, in advance, for any advice.