In the spring, the queen begins laying eggs in huge numbers in one central location of the hive known as the brood nest. When the bees perceive that the brood nest is getting too crowded, they prepare their current queen for flight by slimming her down while simultaneously grooming a new queen in one of several queen cells. Before long, several hundred or even thousand bees will gather up the queen and leave for a new home, while the remaining bees will stay and carry on with their new queen.
Last week's practice swarm warned me that this exodus would happen soon, but the weather turned cold and rainy, postponing the event until yesterday. In the morning I could sense that the bee yard was agitated, but my day's events called me away. By late afternoon, I noticed a cluster of bees on the foundation of my greenhouse. They were certainly clustered around a queen, and the day was quickly passing with storms predicted for night.
We jumped into action and scooped them into a shoe box. Homeless bees aren't aggressive, so it's not as scary as it sounds. Then we put the shoe box into the empty red hive along with two top bars of clean new comb (donated from the blue hive). I also gave them a jar of sugar water.
This morning they are still there. I'm keeping my fingers crossed that they won't abscond.