This won’t be an in-depth talk about swarming. There are entire books addressing the subject. It’s so easy to always be a little bit behind, but at this time in the Berkshire bee season, it pays to be ready for anything. That means having an empty nuc box or two, or even a few deeps, with some frames, drawn and undrawn. When you check your hives, if you have 2 deeps, use your hive tool to pry between them. Standing behind the hive, lift the back end of the top box and slide slightly toward you, then tilt up to view the underside of the frames. That is where you will usually find queen cells. If you do, it’s an indication of swarming. If cells are capped, your hive will almost surely swarm, so keep a close watch and hope you can be there to capture it when it happens.
To determine if the hive has already swarmed, you may notice a much smaller population (about 50%) than you saw last time you looked. That is one sign. Another sign is queen cells that are open at the bottom but have a round “hinge” of wax still attaching the capping to the cell. This means a virgin queen has chewed her way out and is hopefully still in the hive.
If the situation is uncapped queen cells, or capped cells with no newly hatched queens, you can use some frames with queen cells to start new 5 frame nuc hives. Before you know it, you’ll have more hives than you know what to do with. One other benefit of swarming is that it breaks the brood cycle of Varroa.