I have 15 rir pullets that came from Meyers and they are afraid of any thing they see. When I let out in the morning in a 20x20 run they go under the coop and spend the rest of the day there not coming out until all most dark. If I give them bread they run out to get a piece and right back under the coop. My pullets are 13 weeks old and I have had them from the time they were 3 days old. I am wondering if they will out grow this behavior or do I need to get some other chickens. I would like to free range my pullets but if they see some one or some thing they are gone. Thank you for your help.
but all jokes aside, I would say it's pretty normal. Younger chickens seem to be a lot more skittish than adults and I've seen that they seem to mellow out a lot once they lay. They could be just still getting used to their surroundings. Is there any way to prevent them from going under the coop? Chickens seem to be like little kids in the sense that if they haven't tried something, they usually don't like it. I would block any ways they can get under the coop and throw a little scratch out there every day. Also I would (if you haven't) look into setting up roosts in the run along with different levels of things try can jump and play on. I would give it time. 
