Geez. milo! The only place I ever in my life saw a swarm of bats was when I was in the
Philippines, and the huge University of Santo Tomas building had hundreds of small cracks
from many minor earthquakes from which at dusk would come hundreds and hundreds of
bats. I don't recall their circling at all, just dispersing in every direction very quickly.
I can't think of any reason why they should circle in either direction. Their prey insects
were distributed randomly, I'm sure. Not like migratory waterfowl that I one year watched
over Susquehannah River, Just below the Conowingo Dam, circling to see which one of them
was the fastest and going to be point man (or woman) Offhand, I think they tended to fly
counter-clock wise, but I wouldn't swear to it. And anyway, all they were doing was settling
who was going to lead, not which direction they were going to head in.
What possible reason can you think of why bats should circle?