It's that time of year. These bees swarmed from a colony and landed here as a location from which to scout out a new location for the colony. Bees will go out, find a new potential home, report back and other bees will go check it out. If the new digs seem acceptable the whole swarm leaves as quickly as it came. At this point these bees are fairly docile, as they have not brood to protect. When you see a swarm like this leave it 'bee' and it usually departs within a day or two.
