[header] How to add new chickens to a flock [title] Quarantine your new chickens away from the old flock for several weeks, and watch them carefully for any signs of sickness. [step] The new chickens should not share the same ground or air as the old flock. Wash your hands and clean the bottom of your boots after you interact with the new flock to avoid inadvertently transmitting illnesses. 
[title] Make sure the new chickens are of the same size as the old flock. [title] Ensure adequate room in the coop or pen to reduce the chance of bad habits that come from over crowding.