I got a couple of emails yesterday with questions about honey bee swarms. It seems like swarms are misunderstood; so here’s the scoop.
When conditions in a hive are very good or very bad, meaning over-population by a productive queen or under-population by a failing queen that isn’t laying enough eggs; a colony will produce a new queen. There is 16 days between when a n egg is laid for a new adult queen emerges. During this time the old queen prepares to leave taking half of the hives population with her to start a new colony elsewhere. If she doesn’t leave there will be a fight to the death when the new queen emerges. However, the older queen usually leaves the day before the new queen makes the scene.
The old queen and half of the bees will eat a bunch of honey and they will take off and usually land in a nearby tree. They form a cluster that is normally the size of a football. The queen is at the center and the other bees keep her warm and protected. At this point they have no food or brood to defend and this is the safest time to deal with bees.
If left alone they may hang on the branch for two or three days, but the entire time they hang there scout bees are going out searching for an appropriate place to start a new colony. They come back and report when a good place is found. Hopefully they find a good place like a tree with a hole in it. Large bird houses are good as well (except for bird lovers that paid a fortune for the said bird house). Hopefully they will not decide your home or an out building is a good place to build a hive. If they do it will cost big bucks to have them removed. It becomes a construction issue where areas of a wall needs to be removed and replaced.
So if you see a swarm of bees somewhere call your local Extension Agent for a referral to a bee keeper who can come get them before they become a problem. Most keepers will not charge to remove a swarm (except the rat bastards in California), however it can get expensive if the bees need to be removed from a structure. The photo above is of a colony that is moving into someone's home.