So what is that swarm suppose to be? Looks like the way I use to see Black birds flocking and traveling South for the winter when I was a kid in Southeast Missouri. Been a long time since I've even thought about that, but they would whorl and swhorl just like a school of fish and there would be thousands of them and it would sometimes take them 5 to 10 minutes to fly over before the stragglers would be gone. Quite a site to see for a young farm boy the first time I saw it.