The geometry of tree hollows
Thanks to the study “The nest of the honeybee” by T. Seeley & R. Morse from 1976 (see downloads), we have gained a good understanding of the structure and shape of beehives in hollow trees. In the study the authors determined an average volume of 45L and a ratio of height to width of 7.
The space that has been available to the bees in tree caves since ancient times is thus significantly taller and slimmer than the space offered to them in modern beekeeping.
Thermal insulation of tree cavities
Tree caves are equipped with a considerable thermal insulation. The side walls should have had an average thickness of 30cm-70cm. Assuming an average wall thickness of 40cm, a thermal insulation of 2.670m²K/W is obtained (beech wood).
This value significantly exceeds the thermal insulation of houses for humans. The insulation is better still from the top and the bottom of the tree cave. Obviously the bees want a similarly good insulation for their habitations as we humans do for ours.
Because of the good insulation, more time remains for the bees to engage in important work. In modern bee hives, the temperature on the side walls and on the ground drops to the level of the outside temperature very quickly. The bees are forced to cease all work early and to take up the winter formation.
Good thermal insulation makes the climate in the tree hollow drier, the dew point is deep in the wood of the tree.
Renaissance of Tree-Beekeeping
Fortunately, there are currently many initiatives and promising projects to keep bees in their natural habitat. Great information about the subject of hives and zeidling can be found at Tree Beekeeping International. We also prepared Zeidler trees ourselves, which are fitted with sensors.