The bee hives have had time now to build up their populations since winter. Swarm season will soon be upon us. In fact, yesterday while I was stealing a few frames of bees from a hive to populate a queen mating nuc I found a frame with 5 capped queen cells. These cells were on the lower edge of the frame; classic swarm cells. Looking closer the hive showed other classic precursors to swarming. All center frames were full of capped brood; leaving the queen no place to lay. The bees were heavy on all 20 frames. It takes about 7 days after the cells are capped before the new queen(s) will emerge. The current queen will take flight sometime before that and off she goes with about half of the hive population.
So today I plan split the hive. I will take the current queen and half the hive population and start a new hive. In theory this "artificial swarm" will stop the swarm. I will then remove the queen cells and install a Russian queen cell that I have available and is due to emerge on Wednesday. I will end up with two hives with strong populations; instead of one weak hive and one swarm off in the bush. With a little luck I could still get a small honey crop from these hives this year.
With last year's mild winter the potential for a lot of swarm activity is there. Swarms typically emerge from the hive around 10 AM. If you have a lot of strong hives, it would be good idea to visit your apiary around 11 AM to check nearby bushes and trees for hanging swarms. Of course you need a spare hive to take advantage of this opportunity.
Or you could open the hive and inspect for swarm cells. By slightly tipping the brood chamber back and looking for hanging swarm cells on the frame bottoms you have a good chance of stopping the swarm. Just removing the swarm cells will not stop the swarming process. The queen will just start a new batch of replacements. Doing a split is your best bet.