The issue isn’t so much just adding more space- the issue is that in temps of 46C in full sun the lid of the hive is BAKING hot. In a single brood hive with bees densely packed inside the brood combs melt and collapse at their tops- setting off a chain reaction that kills the entire hive. “The trick is to see what has worked in the past and use that information.” Agreed- and that’s why I will add the supers: Last year I had 13 hives. 11 of them had supers and all survived the 46C day with no major problems. The two hives that were just single broods were completely annihilated. So that was very clear to me: the supers saved the hives- I have NO doubt about that at all. I also saw a beekeeper who lost around 100 hives that day- an entire apiary wiped out and I noticed they were all Nucs or single broods.
I have a feeling that humidity may play a role- the bees desperately bring in water to cool the hive- however evaporative cooling becomes ineffective if humidity is too high. In a small single brood box perhaps the humidity hits a critical level. Without additional space to move into the bees are clustered too tightly- or if they try to beard they must do so in the baking hot sun… Insulation in the roof will also help during these heat waves to block some of the heat from the lid cooking the hive below.
I believe that quilt boxes, and slatted racks will both help- the quilt boxes will shield the combs from the heat at the roof- whilst also allowing excess moisture to wick out of the hive- and even create a kind of evaporative cooler in the roof… and the slatted rack will give the bees more space in the dark and cool to spread into so they are not clustered too tightly. Anytime the temps are over 43C I believe that shade cloth will also help a lot.
there is ZERO doubt that beekeepers here in SA are going to need to adapt and change what they do if we continue to get these record high temps- and especially if they increase. Many commercial beekeepers with decades of experience lost 1000’s of hives last year. It was a wake up call- no doubt at all.