How interesting! I've never seen a swarm either. From what I've read they are not prone to stinging when swarming. They are just hanging out waiting on the results of scouting expeditions sent out to find a good place to build a new hive. Hopefully, not in your attic! ... LOL

When the scouts come back the faster they waggle the better the site they've found. Based on that a consensus of where to go is reached. Honey bees are fascinating social insects especially in how they communicate in several different ways.

Hives, wild or domesticated, will split when the population reaches a certain mass. Sometimes the swarm is led by a new queen, or perhaps the old. How they decide such things is a mystery.

Often bee keepers will come and capture the hive at no charge. Being high in a tree might put them off though..

Thanks for all the information, Ragna. I'm fine with having them around as long as they don't build a hive in the attic. I've thought about keeping bees in the past, but I'm already stretched thin with all my projects so I don't need to add another one. Plus climbing that high in the tree to gather bees doesn't sound like a great idea.

They've grouped tighter together now:

I used to have a couple of hives. There's a lot to be responsible for in keeping bees, but it was fun learning about them.

Yes, I can see how much tighter the swarm is. Keep us posted.