Yeah, still quarentine. Not everyone that passes on an ill bird does it knowingly. There are some things that a bird can carry that will harm your flock but never cause the other flock any problems because they've built up a resistence to it over time. Sometimes the stress of the move will bring something to the surface that wasn't visable before too. I'd feel much better about bringing an adult bird in from a source I trusted, but I'd still quarentine. On the rare occasion that I've brought adult birds in I not only quarentine I also pen an "extra" roo next to the new birds for the last two weeks of the quarentine period. I might be a bit paranoid, but I'm not going to lose my flock over something so easy to prevent.