If you think you have a swarm of honeybees, please do not panic! They may look and sound alarming but they are rarely aggressive unless provoked, so please don’t squirt water, use an insecticide or throw stones!
Follow this link and a local beekeeper should be able to assist in their removal.
Swarming is an entirely natural means of reproduction of a honeybee colony. The colony will split into two with half the bees taking off with the old queen, leaving the other half to raise a new queen, thus forming a second colony. When swarming happens bees will leave the hive in a swirling cloud and then come to rest on a nearby fence post, tree, building, etc and form the clump that you see in the photo.
They may rest here for several hours or even days while they send out scout bees to look for a suitable new home. It is when they are in this clump that a beekeeper will be able to collect and remove them to a hive. Swarming usually occurs during the months of April, May and June.