Honeybees often split off from their existing beehive colony, and migrate as a swarm of bees. This can be observed as thousands of bees traveling as a swarm in a sort of circular motion to keep together. If you are nearby you'll hear a fairly loud buzzing /humming noise. While swarming to a new location the bees are non-aggressive. Swarms that split may have come from a beekeepers apiary bee box or from a natural setting of nature.
Before bees move they may send out scout bees looking for a suitable home. A party of scout bees can consist of a handful or more of bees that appear to be floating around looking for something. Actually there inspecting the area. if the bees like the location, more bees will come to inspect, then a short while later may move in with the swarm. Often this happens without anyones knowledge.
A migrating bee swarm may rest on a bush or tree for up to a few days before continuing on. When resting, the swarm can be the size of a football or basketball and kind of beard shaped containing some 2,000 to 7,000 bees! Harassing the bees during this faze may confuse the bees causing them to stay longer.
Some lower areas of the U.S. have Africanized honey bees (hybrid honeybees) these bees swarm more often than European honeybees. African or hybrid bees are also non-aggressive while migrating to a new home. Care should be taken around any established beehive.
Bees that are returning to the hive with yellow pollen sacs on the backs of their legs can be a sign that the bees have an established home. If the swarm does not leave, bee removal may be the best solution. Bee keepers & live bee removers remove and relocate bees, while bee exterminators kill the bees and may charge higher rates.
The longer a beehive is established the more protective they tend to be of the hive. If you have had a history with bees near a structure and you hear swarming or see a large group of bees nearby, there is a good chance the hive has split and you are seeing half of the bees grouped together perhaps planning a migration. Bee removal from a structure should take some consideration, if honey in wall is left inside, recurring problems tend to occur; additionally attracting rodents and other critters.