thousands of bees in swarm on sidewalk
I've never posted here before, but saw a very strange thing on my front sidewalk--a dark 'puddle' about 2 feet in diameter located under a maple tree and comprised entirely of what appear to be small golden bees. There must be thousands of them in there. They are crawling over each other and appear to be all alive but staying in this grounded swarm on the front sidewalk.
I got fairly close and a few were flying out of the pile and back but none paid me any attention. But I'm worried that someone's dog will disrupt the swarm while out walking on that sidewalk tomorrow and harm will come to bees, dogs and maybe people.
Any idea why they're doing this or what we should do?