@Kazem Naderi,
I live in Maryland. My hens raise chicks from eggs and I have a 20 by 70 foot run. I let the mother hen take care of her chicks as she pleases. I would like to not let the chicks out of the run until they are about five or six weeks, but the hens need to get back to the hut to lay eggs. There are about 30 chickens and they just ignore the chicks for the most part. I have an acre of fenced in back yard and I have lost a few to predators over the years. I chose the buff Orphington because they are large and the owls and chicken hawks do not usually hunt them after about six or eight weeks old. I also have a great rooster.