Glossary

Overwintering Bees

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Beekeeping

Definition

A guide to preparing honey bee colonies for winter survival and understanding the remarkable biology that allows a warm-blooded superorganism to survive months of cold, darkness, and forageless conditions.

The Winter Cluster

As temperatures drop below approximately 57°F, bees form a tight cluster within the hive. The cluster functions as a living, breathing heat generator. Bees on the outer shell form a tight insulating layer. Bees on the interior generate heat by vibrating their flight muscles. The cluster maintains an internal temperature of 90-95°F at its core.

The cluster moves as a unit through the hive, consuming stored honey for energy. A colony needs approximately 60-90 pounds of stored honey to survive winter in northern climates. Running out of food is the primary cause of winter starvation, second only to varroa mites as a cause of winter colony loss.

Preparation

Fall preparation includes: verifying adequate food stores (supplemental feeding if needed), treating for varroa mites (fall treatment is critical because mites weaken the long-lived winter bees), reducing entrances (to prevent mice and reduce drafts), ensuring upper ventilation (to prevent condensation dripping on the cluster), and optionally adding insulation.

Do not wrap hives so tightly that ventilation is eliminated. Moisture (from metabolic respiration) is more dangerous than cold. A dry colony survives much lower temperatures than a wet one.

Frequently Asked Questions

How cold can bees survive?

Properly prepared colonies with adequate stores survive temperatures well below -30°F. The cluster generates sufficient heat to maintain its core temperature as long as food (honey) is available. Extreme cold is less dangerous than moisture or starvation.

Should I feed bees in winter?

If a colony is light on stores entering winter, emergency feeding (fondant or dry sugar placed directly above the cluster) can prevent starvation. However, fall preparation (ensuring adequate stores before cold sets in) is far more effective than emergency winter feeding.

Do bees hibernate in winter?

No. Bees remain active throughout winter, clustering, eating honey, maintaining temperature, and caring for the queen (and sometimes raising small amounts of brood in late winter). They are dormant in the sense that they do not forage, but they are not hibernating.

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