I got a call from someone today who has a colony which has been inside a tree for a week or maybe two. It's in a hollow near the base of the tree and looks as though the cavity is actually under the tree roots. There don't seem to be any other entrances and the tree was shaped so that I believe I can fill the cavity with water.
I put an empty hive touching the base of the tree and put a hose down into the hollow and started water trickling down. The owner waited about and hour and slowly increased the flow until the hose was running full force. After a couple of hours there was a football sized cluster at the top of the hollow, but they're not appearing to go into the box.
If the water is left on so it, hopefully, fills the cavity and all the bees come out I think they'll go in the box.
Anyone got any helpful suggestions? Am I on the right track?