My family used to raise chickens when I was a kid. The chickens were free-range (only house for like a mile), but they had a coop to eat and nest in, which we shut every night. When getting new chickens to add to the flock (neighbor has too many, etc), we’d keep them in a “chicken tractor” for a few weeks (basically a small, mobile chicken coop). I guess that gave everyone time to get used to each other’s smells or something, because the few times we didn’t do that the new chickens would get pecked in the head by the locals, and once the locals realize that the new ones taste like blood it’s pretty much over for the new chickens.