Let me throw out another question.
 
Does a swarm try to find a new site some (minimum) distance away from the
parent?  How does this work out as regarding competition for available
forage, etc.  I have a dim recollection of reading somewhere that a swarm
won't investigate potential home-sites that are too "close" to their
origin.  I wonder if anyone can provide some info or references.
 
I have always presumed that swarms that arrive and occupy empty hives at my
bee-yards have always come from some distance away, and not from my own
hives there.  Any comments appreciated.                            Thanks!
JWG