Just one more comment to add to this thread.  For years, I've had a yard
right next to a horse farm, separated only by a grove of spruce trees.
There was never any problem until last year when the owner began giving
group riding lessons.  Then there was a swarm of bees that went over the
spruces and clustered on the horse farm side of the trees. Suddenly
there was a big problem - the owner wondered what her students did that
"angered" the bees so much.  She couldn't have such things happening
around her classes!  So therefore the bees had to be moved.  The problem
really had nothing to do with horses, but rather people impatient with
the bees around them.

Ted Fischer
Dexter, Michigan USA