The cherry blossoms (Somei-yoshino) have come to an end, but spring brings a burst of many different flowers blooming all at once. The bees are busily returning to their hives with pollen—yellow, white, and sometimes even red. As nectar sources become abundant and the inside of the hive grows livelier, it signals the beginning of swarm season.
The bees begin raising a new queen, and the old queen leaves the hive with about half of the colony. Swarming plays an important role in the preservation of the species.
However, for beekeepers, this can be quite a serious problem.