By Gary S. Reuter, Department of Entomology, University of Minnesota
In this article I would like to discuss the factors in a honey bee colony that pertain to winter and early spring. How does a colony make it through the cold winter? What are some of the hazards? What can we do to help?
I am not going to go into step by step how to prepare a colony for winter. For this you can go to www.BeeLab.umn.edu and find Beekeeping Information under the Bee Squad heading. Under our Free-bee Information section, you can download information on the steps for commercial winter cover or tar paper.
There are some similarities between the way the bees heat their hive and we heat our homes. There are also a lot of differences.
First we need fuel (gas, oil, electricity, solar, etc.) and so do the bees. The bees use honey for their fuel. Imagine what would happen in the middle of the winter if you ran out of fuel with no way to get more! This can happen to the bees if you do not leave them with enough honey in the fall to get through winter. One big difference is that the fuel is also their food so they don’t usually freeze to death but rather starve to death. Not that that is much of a distinction if you are the bee because you are dead either way.
A major difference between bees and us is that we heat our entire house; the bees only heat the area they are in at the time. It would be like gathering your family together under a bunch of blankets on the bed to stay warm with no other heat source. You really would not care how cold the room is as long as you have enough blankets and can stay under there bundled together. I hope you brought enough food under the blankets with you!
The bees do not have blankets so they cluster together in a ball to stay warm. Some of the bees are on the outside of the cluster with the hairs of their bodies touching providing the “blanket” or insulation. The bees on the inside of the cluster are around the food and will eat it and flex their flight muscles (shiver) without moving their wings to create heat. So the bees create heat just like you would under the blanket. The colder it is the tighter they cluster together. The bees take turns and rotate jobs on a periodic basis. One day a bee is a blanket the next she may be a heater.
What happens when you run out of food under the blanket? Someone will have to go get more food or you will starve. How can you do that without freezing to death? It may depend on how cold it is outside. Can everyone go and bring the blankets to keep warm or should just one person run and bring back a load of food?
This happens to the bees when they run out of food under the cluster. If all goes well with the weather there will be days when it is “warmer” and the cluster can expand. During this expansion they can move the cluster to access more honey. If it stays very cold for an extended period of time the bees cannot loosen the cluster to move to more food.
Most of us heat with some kind of combustible fuel (oil, gas). This causes a large amount of air to be passed into the house to provide for burning of the fuel and exhausting of fumes. Bringing outside cold air into the warm house causes the humidity in the house to be low. If you have electric or solar heat you would actually have high humidity in the house. Bees use internally produced heat and moisture is produced from metabolizing honey; therefore, without ventilation, their hive will have high humidity. High humidity is not good for insects in the winter. Therefore, you must be sure to leave openings for ventilation to bring in some drier air.
Speaking of entrances, now you know why you must leave an entrance. You should provide an upper and a lower entrance. You should be careful not to leave a large entrance on the bottom that would allow mice to enter the hive. Mice are a problem because they build a nest in an unprotected (by the bees) area and destroy comb and stink up the hive. So how small of a hole can a mouse fit into? I have used 3/8” entrance reducers for years and have not had a mouse go in. EXCEPT when they chewed out the reducer to make the hole bigger. They did not have to make it much bigger; in fact I think they just needed to round if off. I have now stapled a piece of 8×8 hardware cloth on the opening so they can’t chew it. You can use any metal you have around.
What you need to have to get a colony through winter is (in no particular order):
- Sufficient population of healthy bees
- Enough honey
- Healthy young queen
- Adequate moisture control
- Pollen stores available in late winter
For more from Gary:
Entomology website: www.entomology.umn.edu
Gary’s website: www.tc.umn.edu/~reute001
Lab website: www.BeeLab.umn.edu