I gave a rooster to my Father-in-Law a couple months ago and he decided he didn't want him any longer so I took the roo back. My question is will my chickens remeber him, or should I do a slow introduction as if he were a totally new bird?
Maybe a rooster they may remember, but certainly would not if it was a pullet. If you do not have another rooster then introducing / re-introducing it would not be a problem anyway.