I got some gorgeous Barnevelders and Silkies at the end of November. I've been brooding them in my house, but they're getting crowded in their brooder. I'm not sure when I can put them outside. The temps dip below freezing at night. They have a large Formex coop that they'll be going into, with a cozy flat panel heater. Any ideas when they'll have a chance at all surviving? Any tips? Thanks!