During this winter hibernation period the bees begin to cluster when the temperature reaches fifty-seven degrees Fahrenheit. They congregate in the brood comb area to regulate the brood nest temperature and keep it at ninety-five degrees. The queen’s egg-laying activity decreases dramatically during the cooler fall months, and by December she has generally stopped altogether. This pause in the queen’s activity reduces the amount of area the bees need to maintain at ninety-five degrees. In January, the queen will begin to lay a few eggs and slowly increase egg production as the outside temperature rises.
When the temperature begins to drop, the bees crawl into the empty cells in and around the brood nest. Since wax provides little insulation, the bees themselves act as a buffer between the brood and the cold outside air. The bees form a ball that looks very similar to what you see when they swarm and hang from a tree branch. The mass of bees is commonly referred to as the winter cluster. The outside layer of bees is tightly packed with their heads facing towards the center of the cluster providing the first line of defense against the cold temperature. Near the center, the cluster is much loose. These bees can move around and retrieve food and care for the young.
The temperature on the outer layer of the cluster does not drop below forty-five degrees. To keep these temperatures regulated so precisely, the bees from the outside layer slowly move towards the inside and the inside layer slowly moves to the outside areas of the cluster. The bees vibrate their wing muscles to generate heat to keep the cluster warm. The entire cluster moves slowly on the comb which allows the bees to take advantage of their food supply stored in the comb. As the temperatures continue to drop, the bees in the cluster form a tighter ball by moving closer together. The ball becomes smaller and more compact, thus reducing heat loss from the interior portion of the cluster.
During the winter months, the bees only regulate the temperature on and within the winter cluster. The temperature inside the hive is basically the same as the ambient temperature outside of the hive. There are times when the ambient temperature is so low that the cluster cannot reduce in size anymore. If the bees are unable to move the cluster to a fresh food source on the comb, the hive will perish. Sometimes the food source is only inches away from the cluster, but the bees were not able to shift the cluster that short distance, and they perish. Running out of food, not being able to reach the food stored, and/or a high mite count are the main reasons a hive will perish during the winter months.
Normally, even during the coldest winter months, there are days the temperature rises high enough to allow the bees to move around on the comb to get fresh food. It is usually not the cold that will kill the bees, but the moisture in the hive that takes its toll. If a hive does not have adequate ventilation to reduce the moisture level, condensation will collect on the bottom part of the top cover and begin to rain back down on the winter cluster. The cold wet moisture can quickly kill the bees. It is very important to provide adequate ventilation for the bees all year long. Enjoy your bees!
This article was written by Dennis Brown, a veteran beekeeper from Bryan, Texas (U.S.A.), with over 50 years of beekeeping experience since beginning in 1964. At one time, he managed 250 hives, raised his own queens, and performed all the duties of a commercial beekeeper. Dennis adapted or completely discarded many traditional beekeeping management practices found in books. Throughout his years with bees, he never introduced chemicals into his hives. Years ago, he started a “Survival of the Fittest” program that eliminated the need for chemicals. Dennis was a very successful beekeeper and enjoyed every minute of it. While there is much more to share about his beekeeping journey than space allows, his books capture the many changes and insights he developed over his career.
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