The cleansing flight is the first flight of the bees after the winter. They empty their digestive tract after a long time of confinement. Avoid greatly disturbing the bee colony before the cleansing flight. Move the mice guard from the flight entrance. Be aware that the first flights may happen later than in other subspecies, and sometimes, you won't even know it. Moreover, there are usually not that many dead bees outside the hive after the cleansing flight as you might see in other subspecies.