I have 3 grown New Hamps & their 7, 4 week old chicks. Currently I shut the 3 up in the chicken house to let the little ones run & play several times a day. When I have them in their pen in the yard the adults seem to pay them little to no attention. I have seen no aggressive behavior from Harry to them but don't want anything to start or have him possibly hurt one. I am putting up a pic of them from this morning. At what age can I safely let the chicks run with their parents?