I can beat that... last year I had five swarms in the same tree, and a sixth in the lilac bush beneath it. The best part is, they weren't from my hives because I was there when they each flew in. ( A seventh swarm landed in another tree about 20 yards away, as well.) I'm thinking my girls are explaining how nice they have it here. There has to be a bee tree nearby, somewhere, but I haven't had time to go searching. This year I'll be placing swarm traps to see if they'll simply move in on their own.