What happens to honeybees in the winter?
The role of a beekeeper changes each season.
In spring, we monitor for swarms. In summer, we feed colonies. In fall, we treat for mites.
This is an oversimplification, of course. But the point is that it requires active maintenance throughout the year to keep bees healthy.
In a lot of ways, everything we do is in preparation for one particularly difficult season: winter.
Winter is when the greatest number of hive losses occur. Even the best beekeepers can't keep every hive alive. This is part of working with nature. Imagine if every colony in the world made it through winter. Then, imagine the following year all of those colonies reproduced 2 or 3 times. We'd be overrun with bees!
This isn't an excuse for hands-off, careless beekeeping. A colony should never die from poor husbandry. Beekeepers need to understand winter losses can and will occur, do everything they can to minimize them, and improve the quality their stock every year.
In this article, we explore what bees do in the winter and what beekeepers do to help their colonies survive.
Do honeybees die in the winter?
Yes, unfortunately, some colonies inevitably die in the winter. This can happen if the population is not large enough, the food stores are insufficient, or the colony enters the winter with a disease or virus.
In 2021, an estimated 32.2% of managed colonies in the United States were lost the previous winter.
At Buddha Bee, those who participate in our Host-a-Hive program often wonder about what the chances of their colony making it through the winter are. The answer is…it’s complicated. But we will say that 97% of our colonies made it through last winter.
Below is a map of winter losses by state from the Bee Informed Partnership which surveys over 22,000 beekeepers across the US:
Beekeepers spend the entire year preparing their colonies to overwinter. It's heartbreaking to open a hive in February only to find a small cluster of dead bees.
When you only have one or two hives, a single loss can be devastating. For beekeepers with hundreds of hives, winter losses are simply a part of life.
Regardless of how many hives you have, winter losses are a learning opportunity.
The best thing to do when your colony dies is to piece together why they may not have made it.
We review our inspection notes, look at the frames of the dead colony, and ask ourselves the following questions:
Did the colony have poor genetics?
Did the colony exhibit signs of a virus before entering winter?
What were the results of the last mite test?
Did they have enough food?
Was there excessive moisture?
Did they have enough ventilation?
What do honeybees do in the winter?
In the winter, honeybees cluster tightly inside of the hive to stay warm. The worker bees vibrate their bodies to generate heat. The queen is toward the center of the cluster where the temperature is around 90–100 °F.
Clusters have two parts: a dense out mantel and a loose inner core. In the outer mental, bees are packed together to retain heat. Toward the center, the bees are loosely packed and can freely move around. The cluster expands or contracts depending on the outside temperature.
Do bees hibernate?
No, bees do not hibernate in the way mammals do. They do not become inactive to conserve energy. Instead, the colony acts like a tiny furnace by pumping their flight muscles all winter long.
This is why you don't see a lot of activity at the entrance of the hive during the winter. The bees not going out to forage because they're too busy keeping the hive warm. Plus, there's next to nothing to eat in the environment in the winter.
On warm days, you may see bees fly out of the hive. If there's no food outside, what are they doing? Well, they're doing their business. Bees are very tidy and prefer not to poop in the hive. Instead, they go on "cleansing flights."
What do bees eat in the winter?
It takes a lot of energy to vibrate all day and night. In the winter, bees eat the honey they've stored away during the spring and fall. While pollen is essential for their diet, honey is their main source of energy.
Honeybees are careful not to waste their precious food stores. As winter approaches, female worker bees will evict male drone bees from the hive.
Drones only live to mate with the queen. Because the queen does not go on mating flights during the winter, the drones are a needless drain on resources.
If you watch the entrance of a hive in the late fall don't be surprised to see a male bee being dragged out by a feisty worker.
How do you keep bees alive in the winter?
The key to keeping bees alive in the winter is proactive management before the winter.
Start with bees that are adapted to the area. If you purchase a package of bees from another state with a different climate, you're starting at a disadvantage.
Monitor for varroa mites and treat if necessary. High viral loads going into the winter put an unnecessary strain on the bees.
Be sure colonies have enough honey. If they don't, feed sugar syrup.
Provide a way for excess moisture to escape the colony. We use shims on our colonies for this purpose, but some beekeepers drill holes into their boxes.
Feed fondant if necessary. When a colony is low on food going into winter, we provide fondant blocks on top of the frames. This is another benefit of using a shim. It provides a gap to add in fondant and/or pollen patties.
Should you wrap your hives?
This varies depending on your location. Where we live, in central North Carolina, it is generally recommended not to wrap your hive because it locks in moisture. The carbon dioxide released by the bees can condense on the hive cover then drip down onto the bees. Imagine trying to stay warm with a leaky faucet dripping on you!
When is winter over for bees?
Bees will engage in clustering behavior anytime the temperature drops beneath 64 degrees. In our area of North Carolina, winter is officially considered over in April. Until the first flowers begin to bloom, careful management is still required to ensure the colonies don't starve.
Final thoughts on honeybees and winter
There is no secret or silver bullet to make every colony survive. Beekeepers debate endlessly about small details such as the configuration of equipment. The truth is, there's still a lot we don't know about the behavior of honeybees in the winter. There's still research left to be done. One thing is certain: careful husbandry before winter is crucial to healthy bees during winter.
We've covered the very basics of honeybees and overwintering. If you'd like to learn more about the dynamics of the winter cluster, this article from Randy Oliver goes into greater detail.