>swarms re-bivouacing before selecting a final cavity. 

A possibility that is often not considered is that the swarm may be a mating
swarm.

These can be very large swarms if a clipped queen has tried to swarm and
then been lost in the long grass.  If the beekeeper fails to take action
then the first virgin to emerge often leads out a very large swarm as there
will have been bees emerging for the 7 days since the clipped queen was
lost.

The swarm may or may not return to the hive or, if the queen has not
finished mating then it may bivouac for a while and then take off again.
These swarms are also notorious for 'absconding' if they are collected
before the queen has finished mating as she will probably fly again the
minute the beekeeper's back is turned and bees will, of course, go with her.

Best wishes

Peter 
52°14'44.44"N, 1°50'35"W

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