When you add new chickens to an established flock it can upset the group dynamics. For this reason we put the new ones to into a metal cage in the same room as the existing flock. It helps them get used to each other.

By the way I would not keep chickens long term in this type of cage although in Spain it is a fairly common thing to do. In a commercial egg farms they would keep 6 or more in a cage this size.

Our chickens are not actually free range because we have foxes, they do however have a large room to live in.