I have 3 RSL chickens who are about a year old. I am bringing in a polish, an EE and a SLW. My question is about introducing them to the 3 hens I have. I have read to bring them in the coop at night and place them next to the hens. My hens sleep on the highest roost about 4 1/2 feet off the ground. How old should my chicks be to be placed up that high in the coop? I want them to be able to get up and down ok. Thanks!!