In spring, a bee colony's thoughts turn to swarming. The queen and about two-thirds of the workers leave their hive to search for a new home.
The swarm perches on a nearby tree, then sends out a few dozen scout bees to scour the neighbourhood. Their job is to find, measure and evaluate every hollow tree or other enclosed space. When the scouts return to the several-thousand-strong swarm, they dance atop the other bees, telling them what they have found.
A potential nest must be large enough to hold ample honey to feed the colony through the winter, high enough to offer protection from predators, and have a small entrance for the same reason. The vigour and duration of each scout's dance reflect her enthusiasm for the site she has found.