Winter Management

Winter management covers all the tasks that allow a bee colony to get through the cold months with healthy winter bees, sufficient and accessible stores and a dry hive. The colony that will survive the winter is actually prepared in late summer and autumn; in winter the beekeeper's job is to monitor from outside without opening the hive and to deal with emergencies.

What are the three conditions for surviving the winter?

Whether a bee colony gets safely through the winter depends on three basic conditions. If one of the three is missing, the other two often cannot save the colony:

• Healthy winter bees: Long-lived bees reared in late summer under a low varroa load, with well-developed fat bodies.
• Sufficient and accessible stores: Position matters as much as quantity; honey must be above and close to the cluster.
• A dry hive interior: A sound hive where condensation does not drip and ventilation has not been cut off.

What are winter bees and why are they so important?

In summer a worker bee lives only a few weeks. Winter bees, reared in late summer and autumn, can live for months. What makes this possible is a well-developed fat body and the nutrient reserves stored in it (especially the protein vitellogenin).

The Varroa destructor mite feeds on exactly this tissue and transmits viruses to the bees. If the mite load is high while winter bees are being reared, the bees emerge weak and short-lived. The result is familiar: the colony dwindles rapidly in mid or late winter, leaving plenty of honey in the hive but no bees.

That is why the first step in winter preparation is not feeding but timely varroa monitoring and treatment in late summer. The details are explained on the Autumn Management and Summer Management pages.

How does the winter cluster work?

When the weather turns cold (usually around 14 °C and below), the bees form a tight winter cluster (overwintering cluster) between the combs. The bees in the outer shell lock tightly together to insulate, while those inside generate heat by shivering their flight muscles. The inside of the cluster is kept warm, while the rest of the hive can be as cold as the outside air.

As the cluster eats through the honey, it moves slowly upwards. Moving sideways in the cold is very difficult for it. Many of the rules of winter management are based on this simple fact.

How much winter food do bees need, and where should it be?

• The amount varies by region: Coastal areas with short, mild winters need little, while highlands with long, harsh winters need much more. The most reliable measure of this requirement, which ranges roughly from 10 to 25 kg, is to record the consumption of colonies wintering in your own apiary.
• Estimating by frames: A full, capped Langstroth brood frame holds about 2–2.5 kg of honey; the number of full frames gives a quick idea of the stores.
• Complete it on time: Winter syrup should be given at temperatures at which the bees can still process and cap it. Syrup given late stays moist and can ferment.
• Beware of honeydew honey: Honeydew honeys such as pine honey are rich in minerals and certain sugars; in colonies that cannot make cleansing flights for long periods they can cause diarrhoea (dysentery). In regions with harsh winters, replacing some of the honeydew honey in the brood box with blossom honey or syrup is recommended.
• Position of the stores: The cluster moves upwards; stores must be above and adjacent to the cluster.

What is isolation starvation?

Having honey in the hive is not enough; the cluster must be able to reach it. During a long cold spell the cluster cannot cross over to the neighbouring frame. The result is surprising: the colony can starve to death while full frames sit just two combs away. This is called isolation starvation.

Why are humidity and ventilation critical in winter?

The cluster can withstand cold; it cannot withstand condensation dripping on it constantly. Water vapour from the bees' respiration condenses under the cold roof and drips. A wet bee loses heat and combs go mouldy.

• The roof must not leak, and rain and meltwater must not get in.
• The hive should tilt slightly forward so that any water that collects runs out through the entrance.
• Ventilation must not be cut off: The entrance is reduced but never closed completely; sealing the hive airtight traps moisture inside.
• The hive must be raised off the ground: Ground moisture and cold should not pass directly into the floor.
• Insulation placed under the roof (e.g. insulating material on top of the crown board) helps condensation form on the hive walls rather than above the cluster.

Mice, rats and other winter pests

Once the cluster has formed, no one is left to guard the entrance. A warm hive full of honey is an ideal winter home for mice; they gnaw the combs and foul the hive with their nest.

• A mouse guard or entrance reducer is fitted in autumn, before the first cold spells.
• In some regions woodpeckers can peck through hive walls in winter; wire mesh protects against them.
• Against wind, snow load and animals, hives are strapped down and weighted on top.

What should the beekeeper do during the winter?

In winter the hive is not opened. Breaking up the cluster, letting heat escape and breaking the propolis seal on the roof all harm the colony. What can be done is done from outside:

1. Weight check: Stores are monitored by gently lifting the back of the hive (hefting) or by weighing it with a hand scale. Note any hive that is starting to get lighter.
2. Entrance check: The entrance must not be blocked by dead bees, snow or ice. Clear a blocked entrance with a thin stick without jarring the hive.
3. Watching the hive front: On sunny, mild days (above about 10 °C) bees make cleansing flights. Flight activity is a good sign.
4. Listening: A faint, steady hum heard when you put your ear to the hive wall shows that the cluster is alive.
5. Check after storms: Inspect roofs, straps and stands.

How do you emergency-feed bees in winter?

If the weight has fallen to a critical level, emergency feeding is needed. Liquid syrup is not given in the cold: the bees cannot process it, cold syrup chills the cluster and it increases humidity in the hive. Solid feed is used instead.

• Fondant or sugar candy is placed directly above the cluster, on the top bars or under the feed hole of the crown board.
• The hive is opened briefly at a mild moment, preferably around midday; frames are not removed.
• The fondant bag is opened on top to leave a surface the bees can reach; the rest of the packaging can stay in place to keep the moisture in.
• Consumption rises quickly in late winter when brood rearing starts; if the fondant is finished, replace it.

Colonies that die by the end of winter: do a post-mortem

A hive that does not survive the winter holds valuable information for the following year. Close the hive when spring arrives so that robbing does not start, then examine it:

• Dead bees with their heads in the cells and no honey nearby: starvation; if there is honey nearby, isolation starvation.
• Very few dead bees, plenty of honey: The colony dwindled away in midwinter; the most common cause is varroa and the viruses associated with it.
• Faecal spots inside the hive: Dysentery; consider the quality of the stores, humidity or nosema.
• Abnormal brood remains or a foul smell: Suspected brood disease; do not use the comb in another hive, and if necessary consult the official veterinary service / local agriculture authority.