What I did was instead of putting them in the coop I put them on the ramp and guided them up. Once close enough they hear mom talking and go running to her. I found with mine it takes 3-7 days of showing them the ramp then they can do it. And yes they will go under mom if cold.I have the same questions. Mimy babies can't get up the ramp I have to try and catch them . It's in the 60s at night but they sleep under her so guess that's warm enough.