Swarming is a natural process. It’s part of colony reproduction where the old queen takes flight from her hive with some of the bees to find a new home. They will form a noisy dark cloud-like formation moving rapidly across the sky until they decide to cluster into a rugby ball shape, hanging off a tree branch, shrub, wall etc., anywhere the old queen will feel comfortable while scouting bees try to find a better location for their home. The length of time they cluster in a location will depend on the time of day and temperature, this could be minutes, hours or overnight. Hence, it’s important to notify a honeybee swarm collector as quickly as possible otherwise the swarm cluster could take flight and move to another location.
Honeybees are generally docile during swarming flight and clustering as they’re concentrating more on finding a new location for their home. Please be careful and keep your distance until the swarm collector you’ve managed to contact has arrived.