At what temperature will the cluster reform?

Why?

In spring, the situation differs from the broodless winter. If the colony is already rearing larvae or pupae, the bees do not merely re-form a classic winter cluster around the stores.

The brood must be kept in a zone of high temperature, generally around 34 °C to 35 °C. In the event of a return of cold, the bees therefore increase their heat production around the brood nest.

If chilled brood is observed, this often means that the colony has not managed to produce enough heat, for lack of bees, of accessible stores or of the capacity to cover the brood properly.

What to understand

The formation of the winter cluster is above all a protective behaviour in cold periods with little or no brood. In March, the presence of brood changes the colony’s priority.

A return of cold can be very costly in energy, because the bees must heat the brood while remaining able to reach their stores. A colony that is too weak or badly positioned on its stores can then find itself in difficulty.

The question must therefore not be understood as a simple search for a threshold in degrees Celsius. One must observe the strength of the colony, the area of brood, the stores, access to food and the duration of the cooling.

Key points

In March, with brood, the colony does not react like a broodless winter colony.

It seeks above all to keep the brood nest warm, which strongly increases its energy needs.

In the event of a return of cold, the colonies that are weak, too spread out or poorly supplied with accessible stores are the most at risk.

Further reading

► Sense and nonsense of thermal insulation of hives

► Overwintering in the honey bee: a very particular phase of its biological cycle

► The winter cluster

► Overwintering successfully