As indoor wintering of colonies becomes increasingly popular among commercial beekeepers, smaller beekeepers have naturally become curious about what benefits indoor storage may provide them. The enormous scale of temperature-controlled warehouses full of pallets might feel either unavailable and unnecessary to a small beekeeper. In the first edition of the indoor storage guide, we included a chapter about modular storage units that may be suitable for sideline beekeepers. But for hobbyists with only a few colonies, this may still not be a realistic option. So, are there other ways for a hobbyist to shelter their colonies from the harshness of winter?
We often hear concerns from beekeepers that their colonies will get too cold over the winter or that cold weather is the cause of some colony loss. It seems impossible that in freezing temperatures a barrier of inch thick woodenware would be sufficient to protect the colony within. In some cases, beekeepers are tempted to provide a heat source to help their colonies stay warm. However, in most cases your bees know best how to maintain the right temperature over winter. Some of the first studies of thermoregulation in honey bee colonies demonstrated that clustered bees could maintain an internal temperature of 80°F even when ambient temperatures were below zero. In fact, by proving a heat source for your colonies such as heaters or blankets, you may actually confuse your bees by making them think it’s warming up inside. When bees think spring is near, they start eating through their honey stores more quickly to prepare for brood production, rather than conserving these stores to survive winter. If your bees think spring is coming before it actually is, they may eat through their honey stores prematurely and be at risk for starvation. Lab studies have shown than bees are most metabolically efficient at 40°F. This means that they become more active (burning more calories/consuming more honey) at temperatures above that, and burn more calories maintaining nest temperatures when outdoor temps drop below 40°F (1). Clustered bees generate heat by using energy from consumed honey to vibrate their powerful flight muscles without flying. The heat generated by these muscles, combined with the insulation of layers and layers of tightly clustered bees, keeps the colony warm for the winter. With this in mind, one of the best things you can do to help your colonies over winter is provide adequate honey stores. The amount of honey needed depends on your location and how long and cold your winter is. A general rule of thumb in northern climates is 80 lbs of honey for 10 frames of bees.
There are some notable exceptions for when you may want to provide your colonies some additional support for winter. In northern US and Canadian climates, temperatures with wind chill can drop low enough to penetrate even the tightest bee clusters. Bees can sustain exposure to very cold temperatures for a short amount of time, but if your weather stays very cold for longer periods, your colonies may be at risk. Temperatures below 15 degrees Fahrenheit for days at a time can be stressful. Wind chill is another important factor. Strong winds whip away heat from around the hive and make the bees have to work a lot harder to maintain their warmth. One of the best ways to ensure your colonies are protected is to give them a wind block. This will greatly reduce the wind chill factor and help the bees maintain their cluster. If you have very cold days for long periods of time, wrapping your colonies in an insulated material can help. Careful consideration should be given to providing adequate ventilation for colonies when wrapping. Bees need to be able to move air through the hive even during the winter. Providing an upper entrance can help bees remove moisture and provide them a flight path if the bottom entrance gets clogged.
Condensation is another concern to consider. As the bees generate heat, their also generate moisture from respiration. As this moisture rises and comes into contact with the cold lid or inner cover, condensation will form. This water can then freeze and bring down the temperature of the colony, or create enough moisture to generate mold. Insulation under the lid or between the lid and inner cover can help. This can be as simple as placing a sheet of newspaper or a layer of straw between the bees and lid. In general, experienced local beekeepers and beekeeping clubs are a great resource to ask about how bees in your area normally fare over winter, and what beekeepers do to help support them.