Honey bees are social creatures. They live in a nest of tens of thousands of bees and this nest is their key to survival.
In order to understand how bees survive the winter, let's first look at how honey bees prepare for winter.
Then, we'll look at how they withstand the cold, the common reasons why colonies don't survive the winter and what the beekeeper can do to help.
How Honey Bees Prepare for Winter
Winter preparation begins in the late summer/early fall. It starts when the bloom season ends. The lack of flowers blooming (which also means lack of food for bees) causes somewhat of a frenzy. This is often a time when your bees will be a little cranky and you may see them frantically visiting the few flowers they can find as well as robbing other bee hives.
Yes, honey bees rob each other! The amount of robbing that goes on depends on how many flowers there is available. That's why planting flowers that bloom in the late summer and early fall is a great way to help the bees. See our article about winter time projects to create a pollinator garden and how to make a bee hotel for planting guides.
Yes, honey bees rob each other! The amount of robbing that goes on depends on how much food there is to gather.
Winter Bees & Decrease of Population
The next step to preparing for winter is making the winter bees. Not only will the queen stop laying so many eggs, but the eggs she does lay will grow up to be the winter bees. Winter bees have a higher body fat content and larger hypopharyngeal glands. They will take the hive through the winter.
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Photo: drone (male) honey bee
Kicking Out the Drones
Although it's not the nicest part of the winter preparation, the hive will also kick out the drones (male honey bees). The worker bees may bite them or sting them or simply not let them back in the hive. I've seen sad little piles of drones just a couple of feet from my hives on an autumn day.
It's sad to think that the poor drones are kicked out just because they're male, but the hive works solely for the benefit of the hive's survival, not each individual bee. Since the drone's primary purpose is to mate with a queen, and there is no mating done from fall to early spring in cold climates, they are eating the hive's food storage and decreasing their chance of survival.
Photo: Beekeeping for Dummies
What Bees Do In Winter When It's Cold Out
In the Late Fall / Early Winter
Once it is around 55-58F (12-14C) outside, the bees will form a cluster inside the hive. This cluster is loose and allows air to flow through. As it gets colder out, the cluster will tighten and the bees will vibrate the muscles in their thorax to produce heat. Since there is no brood present in the late fall and early Winter, the cluster does not have to produce as much heat. They only have to keep the adult bees warm enough to stay alive.
...the bees will form a cluster inside the hive. As it gets colder out, the cluster will tighten and the bees will vibrate the muscles in their thorax to produce heat.
What Bees Eat In the Winter
Bees still have to eat! The cluster usually forms at the bottom of the hive and it will move up over the course of the winter, eating the honey stored in the cells of honeycomb. If necessary, the bees will move to the very top of the hive where the beekeeper has left them dry, white sugar or a hard candy.
Mid-Winter to Early Spring
Once it is early to mid-winter, the queen will start laying eggs and the cluster will tighten to keep the brood (baby bees) warm. The brood needs to be kept at a temperature of 93F (33C). The walls of the cluster will be about 3" thick with the bees' heads facing toward the center of the cluster. The very center of the cluster is loose so that bees can walk around and take care of the brood and the queen can lay eggs.
Watch our video about bees in the Winter.
The Role of the Beekeeper in Winter
Late Summer Preparation
The beekeeper usually harvests honey from the hive in the late summer, or whenever the hive slows down and stops bringing in a considerable amount of honey. Once the harvest is over, that is when most beekeepers will treat their hives for varroa mites if it has a mite level of 2 or more (a simple mite test is done to calculate the level). Here's an article about how to use apivar strips to control a varroa mite infestation.
Additional things the beekeeper will do in the late Summer is:
- Reduce robbing by blocking up all of the entrances except one and reducing the one remaining entrance.
- Put a feeder with 2-to-1 sugar syrup in the hive if it does not have enough food for winter.
- In late summer or early fall (depending on the daytime temperature), the beekeeper will put a mouse guard on the hive's entrance.
The Beekeeper's Fall Preparation
In fall, the hive population has decreased and there may be very little brood or none at all. This is when the beekeeper gets ready to close up the hive for the winter. They will make sure the bees have adequate ventilation, something to absorb moisture and prevent condensation from dripping onto the bees, plenty of food, a warm, sunny spot, insulation and an upper entrance. They will also take the sugar syrup out.
The Beekeeper's Duties Throughout the Winter
The beekeeper should check their hive every 1-2 weeks and use their hive tool to scrape any dead bees out of the hive that are blocking the lower entrance as well as shovel any snow that might be blocking the entrance.
The beekeeper's second task is to make sure the colony has enough food. This can be done by simply tipping the hive to see how much it weighs or on a warm, sunny, low wind day, when it is at least 50F (but preferably 55F+) the beekeeper can peak under the lid to see if there are any bees eating the sugar they have stored for them under the lid. If the beekeeper sees bees in this area, that means they will want to add more food.
What the Beekeeper Should Not Do In the Winter
It is important that the beekeeper not open the hive and inspect the colony, disturb the bees or pull out frames when it is below 65F.
I believe the beekeeper shouldn't inspect a hive at all during the winter time, even if there is a period when it is above 65F. This is a time when the beekeeper has to trust that the bees know what to do and how to stay warm. It is not a time to introduce a new queen, add frames of honey or treat for varroa mites.
A Tip for the Beginner Beekeeper
Preparing your hive for winter and making sure they're healthy isn't easy. There's a few steps the beekeeper takes in order to do this properly. This article goes over the basics, but I strongly recommend doing your research or taking a class in order to understand these steps fully.
Our online beekeeping class, takes you through the steps of preparing your hive for winter in the summer and fall so your bees go into winter as healthy as possible. If you would prefer an in-person class, many beekeeping associations offer beekeeping classes. If you just need a refresher on how to prepare your hive for winter, I recommend picking up a copy of Beekeeping for Dummies.
Common Causes of Hive Death In the Winter
Unhealthy Queen
Many people think the cold is what kills most hives during the winter. In fact, there are many things that can influence a hive's survivial. A young, healthy queen is important for survivial. If a hive's queen is not strong enough to survive the winter, they will not have brood reared (baby bees growing) for early Spring.
Lack of Ventilation and Condensation
Bees do not heat the entire hive during the winter. Instead, the cluster produces heat just for the bees in the cluster. It is important that the hive have ventilation. This means giving the bees an upper and lower exit to leave the hive and a way for warm air to chimney up and out of the hive. An upper entrance will cut back on the amount of condensation building up in the hive. Condensation dripping on the cluster can kill a colony .
Lack of Food
It's exciting to harvest honey from the beehive in the summer, but it's more important that the bees have enough food to get them through the winter. The beekeeper will not only leave the colony enough food to go through winter, but also give them an extra box of dry, white sugar or candy up above the honey as a backup.
An easy way for you, as a beginner beekeeper, to see how much honey to leave your hives is to not harvest any honey your first year and see how much is left in the spring. This will tell you how much honey the bees consumed over the winter. Make sure you, first, calculate how much honey is on the hive before you close it up for the winter!
An easy way for the beginner beekeeper to figure out how much honey to leave their hives is to not harvest any honey their first year and see how much is left in the spring.
As a backup, the beekeeper should still have a box of sugar up above these frames of honey. This box of sugar is up above the honey and solely a backup feed in case of emergency.
Varroa Mite Infestation
It is important that the beehive have very low varroa mite levels in the late summer and fall. If a hive is tested and has more than 2 mites per 1/2 cup of bees, it is recommended that the beekeeper "treat" the hives with an organic or inorganic chemical to kill the majority of the mites.
The first varroa mite treatment the beekeeper may have to administer will be in the later summer, so that the winter bees are healthy as pupae.
Unfortunately, because a lot of robbing occurs in the Fall, most beekeepers will have to treat again in the late fall before they close up the hive for winter. This is often done with oxalic acid which is highly affective when no brood is present.
Photo: Me checking a beehive in the winter. Long sleeves, veil and gloves optional.
What Bees Do In the Winter In Warm Climates
In warm climates where there is no frost and the outside temperature does not get below 65F in the daytime, the bees will not be clustered inside the hive. The queen will continue to lay eggs and, in most cases, there will be drones in the hive year round.
The Role of the Beekeeper in the Winter in Warm Climates
Warm winters may sound nice, but it also means that there are a lot of insects! Here in Hawaii, we have very high levels of varroa mites and small hive beetles. In the winter, there is not much blooming. The bees will rob each other and will be pretty cranky and aggressive for a few weeks. The queen does not lay as many eggs and the population decreases quite a bit.
Photo: small hive beetle larvae and slime on honeycomb.
Because there is a high small hive beetle population and a lower honeybee population, this is a common time for hives to collapse from beetle infestations. To prevent this, we store excess frames of honeycomb in a chest freezer and feed it back to the bees as needed. It is a balancing act ensuring that the bees have enough food to survive but not too much that a beetle infestation occurs.
In Conclusion
Honey bees have been dealing with cold weather for many years. Some strains, like the Russian and German honey bees, are better at dealing with it than others. With the right genetics and a strong colony, your bees have a great chance of surviving the winter. The best way to ensure you have a colony with the genetics to deal with a cold winter is to buy your bees as locally as possible.
One of the hardest parts as a beekeeper is trusting that the bees know what to do and not bothering them! Bees do an excellent job gathering an excess of food, sensing when the seasons are changing and preparing the hive for the cold.
It may seem like it is too cold out for bees to survive in a wooden box outside, but the cluster does an excellent job producing heat and keep the colony warm. Remember, they don't have to heat the entire hive, just the cluster. And when there's a warm day, go out to your hive and watch the bees flying out to do a cleansing flight.
Winter Hive Loss Data
For those of you who love cold, hard, facts, here's some interesting data from the Bee Informed Partnership.
- The Bee Informed Partnership conducts a survey of managed honey bee colony loss in the United States. 3,377 beekeepers managing 276,832 colonies as of October 2019 were surveyed. This survey represents 9.9% of the estimated 2.81 million managed honeyproducing colonies in the nation (according to the USDA, 2020).
- During the 2019-2020 winter (1 October 2019 – 1 April 2020), an estimated 22.2% of all managed honey bee colonies in the U.S. were lost. This loss represents a decrease of 15.5 percentage points compared to last year (37.7%), and a decrease of 6.4 percentage points compared to the 28.6% historic average winter colony loss rate documented by previous surveys.
- This is the second lowest level of winter loss reported since the survey began in 2006-2007. Similar to previous years, backyard beekeepers lost just slightly more colonies over the winter (32.8%) compared to sideline beekeepers (31.8%).
- Backyard, sideline and commercial beekeepers lost an estimated 32% of their managed colonies.
- During the summer 2019 season (1 April 2019 – 1 October 2019), an estimated 32.0% of managed colonies were lost in the U.S.. This is the highest summer loss rate ever reported by this survey.
- "The observed increase in summer mortality during 2019 can most likely be explained by the high losses experienced by commercial beekeepers (33.0%). Their historic average summer loss rate was 22.0%."
- For the entire survey year (1 April 2019 – 1 April 2020), beekeepers in the U.S. lost an estimated 43.7% of their colonies. This is the second highest annual colony loss rate reported since the survey began estimating this measure in 2010-2011.
Learn more about this organization and see hive reports from previous years.
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