It’s gone very cold over the last few weeks and I don’t see any bees buzzing around the garden. Not that there’s much for them to feed on at this time of year. If you’re new to beekeeping like myself you’ve probably wondered what occurs to a bee colony during the cold winter months of the year when all that buzzing comes to an end.
So what happens to honey bees in the winter? Unlike many other insects honey bees do not hibernate during winter. They remain active and shelter inside their hive, huddling together to keep warm and protect the queen. As winter begins, brood rearing ceases and the queen stops laying eggs. The size of a bee colony reduces significantly over winter.
Beekeepers can take a bit of a break at this time of the year because hives get closed up for the winter. But that doesn’t mean you don’t have to do some preparation before winter starts, nor abandon your hives completely. So how do honey bees get through the cold months? What happens to the colony during this time, and what do beekeepers need to do to help their bees cope during the cold season?
How Honey Bees get Ready for Winter
In the northern hemisphere there’s little or no food for bees throughout the winter months between October and February. Honey bees don’t hibernate, but rather they survive the winter by collaborating together as a colony. Bees take refuge inside their beehives during the cold season and they prepare for this period beforehand by storing honey.
The lack of forage at this time of year (nectar and pollen) is the reason bees make and store honey. Bees need honey for energy and they need energy to generate heat and keep the queen bee warm when the temperatures drop. The continued existence of the colony depends on the successful overwintering of the queen.
So when native vegetation is in full bloom the bees are busy collecting nectar and making honey.
But you may already know that bees don’t just collect nectar and pollen. They also forage for resin and sap from trees and plants which bees turn into propolis (also known as bee glue, this sticky stuff is made by combining plant resin with saliva and beeswax). Bees use propolis in particular for sealing up any unwanted gaps in a hive and in preparation for winter honey bees will close up any cracks to prevent any cold draughts.
Honey bees don’t fly well when temperatures drop below 10°C (50°F), although they will leave the hive in search of fresh nectar on warmer winter days and also for cleansing flights to relieve themselves.
By the time the cold months arrive, bees have done the work they need to prepare the colony for winter.
The Honey Bee Winter Cluster
Worker bees do this by forming a huddle around the queen. This is known as a winter cluster. When temperatures drop to around 15°C (60°F) bees will begin to cluster. As the temperature drops further, the cluster becomes more compact and the bees move closer together.
The winter cluster is formed in the brood chamber of the hive (for example in a Langstroth type hive this is located in the larger boxes at the base of the hive). A cluster can spread across a number of frames and can cover 8 to 10 frames at a time, but this cluster will contract in colder temperatures, sometimes down to as little as 2 to 3 frames.
The temperature difference between the outside and inside of cluster varies. The outer layer of bees crowd together to form an insulating coat using the hairs on their bodies to capture and retain heat. As the temperature falls, the bees move closer together to reduce any gaps and increase the level of insulation and reducing the surface area of the cluster. The inner layer of bees is less compact and the bees can move around more freely to get to food and also care for any brood that is still present. The “ideal” temperature for the center of the cluster is 35°C (95°F) but the average core temperature can be lower and bee colonies will still survive. At around -5°C (23°F) bees begin to vibrate their wings and bodies to generate heat.
(All that movement requires a lot of energy which the bees get by feeding on their honey supplies. One of the beekeeper’s winter tasks is to ensure that bees have enough stocks to last the cold months, and if necessary supply extra food if they run out)
The worker bees constantly rotate their position in the cluster to avoid getting too chilled. They change places from the outside to the inside to warm up, and the well fed warmed inner bees move out to the edges.
By vigorously moving their muscles, bees are constantly using up energy. Bees need to generate enough heat to be able to spread out over adjacent comb or change the location of the cluster to reach stores of honey. As the cluster contracts the space in the core becomes smaller. If temperatures remain very cold and this compact cluster continues for a long period, bees will eat all the honey they can reach in the center of the cluster and may have difficulty reaching new food stores. This is why Larger clusters have a better chance of surviving the winter. More bees means that it is easier to get to any available food. This kind of problem is normally only a problem in very cold regions such as the northern half of the U.S.
A larger cluster of bees also means that some bees can reach the outer edges of beehive frames and food can be passed to bees in the center.
(Tip: If you live in a particularly cold climate then it’s a good idea to take winter into consideration when you locate your hive. try to put it in a location where the low winter sun will be able to warm the front of the hive during the day).
Honey Bee Colony Population during Winter
What happens to the population of a honey bee colony during the winter time?
A healthy colony can have up to 60,000 bees at the end of summer. That number can reduce to 20,000 or less by spring. Some of the colony’s bees will die every day. It’s just part of the natural life cycle of a colony. But during the winter the queen isn’t laying and old worker bees don’t get replaced by young bees.
Bee colonies live through the winter but not all of the bees will survive. A bee colony is composed of three types of bees. The Queen, the workers and the drones. There’s only one queen and she’s the most important. The rest of the population is made up mostly of worker bees and a few drones. As you can guess, the “worker bees” do all the work. The drones only purpose is to mate with a queen. They don’t collect nectar, so drones don’t contribute to food stocks in the hive. In preparation for the winter, drones are usually forced out of the hive in the fall and will be replaced when more drones are born in the spring of the following season. Drones are of no use over winter and would only increase the number of mouths to feed!
Some bees will inevitably die off during winter so don’t be shocked to find dead bees littering the front of your hives. Usually bees will die when they’re out foraging for food so you don’t notice. But in the winter, worker bees will simply push dead bees out the front door!
Brood Rearing over Winter
(Beekeepers use the term “brood” to refer to the various stages of development of bees ranging from eggs, to larvae, then pupae and finally adult bees. “Brood cells” are the hexagonal shaped holes found on the wax honeycomb).
Brood rearing stops when bees enter the winter period but brood rearing can begin again as early as mid-winter when outside average temperatures are above 4°C (39°F). It’s been found that queens who begin rearing brood in mid winter produce colony sizes four times bigger than queens who start laying later in the spring.
Brood Rearing happens even when there are no pollen or nectar sources available. During the cold nights worker bees must work particularly hard to prevent brood from getting chilled. Bees will crawl inside the comb cells to keep surrounding brood cells warm.
Consequently the bee’s honey stores are consumed more quickly during this activity. This can of course increase the risk of colony starvation. Beekeepers can try to ensure that this doesn’t happen by providing bees with supplementary feeding. You can also quickly check on your hives during the winter by lifting the lids every few weeks to control food stores and replenish them if necessary. Do this during the warmer days to avoid chilling the interior of the hive.
How much Honey to Leave Bees for Winter?
Prior to the winter months beekeepers harvest honey from their hives (playfully referred to as collecting the rent). But by now you know, you can’t take all the honey from your bees because they need food to survive cold winter months when they’re confined inside their beehive. So how much honey should you leave for bees to get through the winter comfortably?
This is a tricky question and depends very much on the severity of your winters. If you live in a hot climate, bees will use less energy than if your beehive is located in a cold region. In the south bees can probably be out flying all year round, but in the north winters can be long. In the United States you can use the following rule of thumb to help judge the amount of stored honey your bees will need.
- In the southern states: between 0 and 50 lb (0 to 23 kg) of stored honey
- In the middle states: between 60 and 75 lb (27 to 34 kg)
- In the northern states: between 80 and 100 lb (36 to 45 kg)
In regions where winter is a concern most beekeepers check honey stores around October before closing down and preparing the hive for winter between the beginning of November and thanksgiving.
A lot of beekeepers keep bees for honey, but don’t be guilty of taking too much honey from your hives and letting the colony starve. A good supply of natural honey will avoid the need for lots of supplemental feeding.
Tip: Knowing how much honey to leave will vary from year to year and region to region. It’s a good idea to join a local beekeeping association. Locals will have a much better experience of what to do where you live. Read my complete guide about how much honey bees need for winter here.
Ways to Help Bees Survive the Winter
Apart from upholding good beekeeping practices what else can you do for your bees during the difficult parts of the year?
If you’re a keen gardener you can always help out your bees by planting certain types of flowering vegetation. In late fall and early spring nectar sources can be hard to find, but certain plants bloom well at these times of the year and can be a welcome source of nourishment for bees.
For a more details take a look at my article about honey plants and flowers for attracting bees.