I have a flock of 6 chickens and 1 turkey. 3 RIR, 2 BO, 1 JG, and 1 Broad breasted turkey. I need to add 1 polish and 1 narragansett but I don't know how old the chicks should be before I begin the process of introducing them to the flock. Presently they are 4 weeks old. Any suggestions? Thanks all!