We could be forgiven for thinking that bumblebees will be relaxing as the year comes to an end and the broods have left the nests but we would be wrong. There is obvious desperation being shown by the surviving queens as they seek out the few flowers that are still blooming. No longer can they afford to stick to a single species in the interests of efficiency and so they stop at anything in flower. Currently Dahlia, Anemone, Nasturtium and Scabious are good sources of pollen and nectar. Soon Mahonia and Heather will take over. If our gardens have nothing in flower, we will see no bees but they will visit as long as we make it worth their while.
Large queen bees are now also looking for places to hibernate. Only those with well filled fat reserves will make it through the next four months when it is too cold to fly. Ideally they will find a nook at ground level beyond the reach of birds, mice and spiders. It could be under a garden shed, in brickwork, or a compost heap. In the wild they look for a North-facing bank in earth that is soft enough for them to burrow in. They are not designed for digging but we can help by spreading a sackful of compost in a suitable position, perhaps with a few strategically placed cardboard tubes as burrows. By choosing a North-facing site they avoid being woken up too early by an unusually hot Spring day before any flowers are in bloom.
Recently we found a weak bumblebee on the ground. She ignored the sugar solution on offer but climbed up the teaspoon onto my hand. She then lowered herself onto my palm and rested for a couple of minutes before flying up and away. I think that she had been too cold to fly and used me as a heat source. Low air temperatures can only be coped with by bees that can find sufficient nectar to provide the energy for them to shiver themselves enough to raise their body temperature to above 30C.
Most of the bumbles flying locally this month will be the Common carders in their ginger fur coats, and the Buff-tailed ones wearing the more usual black fur with two yellow bands and a grubby white tail. These fertilised queens will hibernate unless we have a mild Winter and will only emerge when temperatures reach 10C or more. Those that remain active will benefit from Cyclamen and plants like Primrose, Snowdrop and Crocus in a few weeks’ time.
Adrian Doble (Bumblebee Conservation Trust) October 2020