I bought eight chicks - two each BCM, Black Australorp, light Brahma, and Ameraucana, about a month ago. They had been hatched a little over a week before, so are about six weeks old. These eight are in my coop. I then bought five Buff Orpington, which were hatched last week, and are inside my house. At what age will the Orpington be ready to go into the coop, and should I separate them at first? What should I know about combining the flocks?