It’s June 2019 and I’ve significantly rewritten this post from 2014 to reflect my practice of not always reversing the brood boxes in the spring. To cut to the chase, these days I tend to reduce my hives to a single deep in the spring because the colony seems to stay warmer and expand faster when it’s restricted to a single deep. Only when the colony is close to filling the single deep with bees do I add a second deep. If the weather is still cold or the colony is more on the weak side, the second deep goes on the bottom where it’s less likely to screw up the thermodynamics of the brood nest. But if the weather is warm, the colony strong and expanding quickly, the second deep goes on top. You can pretty much skip the rest of this post now.
I used to reverse the brood boxes in my hives in early spring as soon as I had a warm enough day for it. That means at the end of winter in a typical 2-deep hive when the brood nest was usually living only in the top deep, usually some time in April, I would move the top deep (full of bees) to the bottom of the hive and then the bottom deep (mostly empty drawn comb) to the top of the hive.
The logic behind reversing is to prevent swarming by providing space above the brood nest for the colony to expand. That logic assumes honey bees always expand the brood nest upwards. Perhaps the bees have a greater tendency to expand upwards in the spring after a winter of working their way up into their honey stores. But experience tells me that most colonies will expand wherever they can find space, whether it’s up or down or sideways. So the whole argument for reversing is easily dismissed.
Aware of that, I reversed my hives anyway because reversing allowed me to assess the strength of the colony going into the new season and make adjustments on the spot if necessary. I would add drawn comb to the brood nest if the cluster needed the room. I would add frames of honey or pollen if the bees were starving for it. I would give them frames of brood from another colony if they were weak. In short, I would take whatever action was required to get the bees started on the right path for the new season.
Then for the rest of the year, because I knew exactly what condition the colony was in at the beginning of the year, I’d be able to assess the strength of the colony without having to dig much into the hive and disturb the brood nest every time I did an inspection.