November starts with steady rain for several days. The river Nairn is in full spate and nearly bursting its banks. We walk in light rain climbing to the top of the grouse moors looking out over the Moray Firth and it’s good to get out despite the soak. It feels like an adventure eating sandwiches on the soft mossy bank and catching a blink of sun that just emerges briefly from behind thick grey damp clouds. I feel myself chilling though and pull out a spare jacket from the rucksack.
It’s very quiet up there: normally gregarious grouse fly past silently and sheep graze the short green grass between the clumps of heather paying little attention to us. The inbound flight from London breaks the peaceful silence. It drops down beneath the clouds lowering its undercarriage for the landing in Inverness. The engine revs to compensate for the enormous drag created by the undercarriage, and you can hear the noisy engine roar and air rushing through the undercarriage.
Hosting Beekeeper from Alaska.
This week’s highlight was being asked by Barbara Sandbach from Inverness Beekeeper’s Association to host Lisa Hay a visiting beekeeper from Fairbanks, Alaska and her son Ronan. Barbara was disappointed to have been too poorly to show Lisa some Scottish beekeeping but it was lucky for me,and an honour to be asked. Here was another great opportunity to learn a bit about beekeeping in another country on my very own doorstep.
We walked to the wild bee tree just under 2 miles away before afternoon tea. After that we looked round our apiary and visited Cynthia’s bees down at the distillery to see how double-walled hives operate. Lots of information was exchanged and we learned how Lisa abhors the local practice in Fairbanks, Alaska of destroying the bees at the end of summer and buying in new colonies from the south for the next season. Watch out for a guest blog from Lisa, and an account of making changes that involve building an over wintering bee shed and sharing information locally. https://www.facebook.com/happycreekak
The edited version of this article was published in BeeCraft November 2021.
This article examines bee behaviour in relation to the changing season, and conditions inside the hive over winter in the UK. It includes beekeeping management strategies to promote winter survival.
We know from work by Matilla and Otis1 that winter bee production is stimulated by a diminishing pollen income as the foraging season comes to an end and triggers the internal changes in bee physiology. The time of production onset will vary across the country and according to climate and weather in a particular year. Providing pollen supplements in spring helps boost a colony’s brood rearing, but doing so in autumn could be harmful because it may delay winter bee production causing an imbalance between long-lived winter bees and short-lived summer bees within the colony thus reducing winter survival chances.
We also know that varroa feed on fat body tissue spreading many viruses via the haemolymph, or bee blood, and that varroa numbers falling onto the sticky boards rise exponentially towards the end of summer as brood rearing declines and varroa spend more time on adult bees in the phoretic stage. Armed with that knowledge, we can treat our colonies for varroa with the appropriate varroacides as soon as the last honey harvest is over in August, or early September in the case of colonies returning from the heather. These later times to treat are fine if varroa levels are not sky high and you are not seeing related deformed wing virus or parasitic mite syndrome.
The BeeBase2 varroa calculator is invaluable in helping to make the decision about when to treat, and anyone may use it. All beekeepers in the UK should register their apiaries on BeeBase as a means of reporting the presence of varroa which is a legal requirement as of 2021.
Formic acid in the form of Mite Away Quick Strips can be applied during a nectar flow with supers in place and is the only varroacides currently available that kills varroa in the cell. Its use must be balanced with the risks which may be supersedure of a frail queen, and sometimes the loss of some brood and bees. If you apply two strips as directed but in a small space with inadequate ventilation in a hot weather then you can expect more bee deaths.
As well as giving winter bees the best possible chance of a healthy start and longevity, reducing varroa levels as early as possible towards the end of summer reduces the viral loads of those bees going into winter. For example, it takes around 30 days for deformed wing virus levels to fall significantly after treatment and for symptoms such as high worker mortality and signs of bees with deformed wings to lessen.
We all need carbohydrates to give us energy and produce heat in our bodies, and during winter honey bee colonies rely on honey stores to maintain the temperature inside the winter cluster. This is especially so around the time that the queen begins laying again and when the brood nest temperature must rise to at least 34˚C. I leave around 35 lbs of honey for each colony, but how much to leave will depend on climate and length of winter so it will vary across the country and with different races of honey bees. Our native honey bee, Apis mellifera mellifera, is thrifty and will eat less over winter than the Italian honey bee, Apis mellifera ligustica, for example.
The beekeeper who harvests every last drop of honey usually feeds a sugar syrup solution as soon as the honey supers have been removed and before it is too cold for the bees to evaporate the water and store the sugar in a form resembling honey. With increasing awareness of bee health and its promotion, increasing numbers of beekeepers are leaving their colonies with a super full of honey for winter stores. This means that they spend less on feed bills and they might only need to supplement stores in early spring by giving fondant.
Contrary to what some beekeepers believe, honey bees do actually store fondant and it looks just like white pollen though it isn’t. I’ve tasted it. Bees probably bite off pieces of fondant with their mandibles and carry them down to pack in cells which you can see in the photograph. So, you can successfully feed only fondant if you wish to boost winter stores.
It is quite common where I live for egg laying to decline in August and inexperienced beekeepers often panic and think that they have lost a queen. Good queens are often purchased and promptly lost as the hasty beekeeper introduces her to a queenright colony.
A young vigorous queen will contribute positively to the colony’s winter survival, and she will be ready to lay around the winter solstice when brood rearing commences in preparation for the new season ahead. For various reasons, queens today usually do not remain productive for more than a couple of seasons which impacts our management.
This is a good reason to ensure that queens going into winter are not old. It is also a very good reason to turn down the kind offer from benevolent beekeeper down the road who offers you one of his old queens as he gets his colonies ready for a good winter with fresh young queens. You might be lucky, but if you want to give your bees the best chance of winter survival, and a strong spring build up, then plan your own management and learn to raise queens from local stocks to ensure that only young local queens head your colonies at the end of the season.
The Winter Cluster.
Let’s look at what happens when the weather cools, how the winter cluster forms, and the bees become a compact ball. Let’s also review the by-products of metabolism in relation to hive ventilation, and consider the waste disposal process of individual worker bees.
Back in 1927, Wilson and Milum3 discovered that the winter cluster begins to form when the inside hive temperature drops below 18˚C. Bear in mind, the colony only keeps the brood nest warm and doesn’t expend energy heating the whole house, which reminds me of living in a Glasgow flat in winter on a low nurse’s wage and keeping only one room heated.
As the cluster is forming, very active feeding goes on as the bees stoke up in readiness to generate heat when required by isometrically contracting their flight muscles without opening their wings. Heat is conserved through the clustering action because the colony’s surface area is reduced and there is less conductive heat lost to the cooler atmosphere and to hive structures. There is also less heat is lost by convection if there are no spaces between the bees for draughts to flow through.
When the ambient inside-hive temperature inside the hive drops further, to below around 14 ˚C, the cluster forms a compact outer layer or mantle of quiescent bees. Meanwhile, inside at the core the cluster there is still room for the bees to move about a little. The outer mantle can consist of several layers of bees with their heads facing inwards as in a rugby scrum without the action. These mantle bees will position themselves so that their body hairs interlace and creating duvet-like insulation material. This is due to branched plumose hairs that have special properties similar to down, which traps warm air.
Figure 1 from Wilson & Milum, 1927 demonstrating the connection between ambient hive temperature and the size of the winter cluster.
The cluster stops contracting when the hive temperature falls to -5 ˚C, and this is when consumed stores are utilised and extra heat is generated by wing muscle contraction. More honey is needed to continue heat production and so the cluster breaks (here and there) to enable individual bees to move through the nest to reach supplies. It is important to understand that the cluster extends over several frames and not just one single frame, but if the colony is not large enough to conserve and generate heat under very cold conditions, the bees may not be able to leave the cluster and access food that may be close by. This leads to isolation starvation. The risk of losing colonies this way is reduced by having strong colonies going into winter and having plentiful food stores above the cluster. A large cluster of bees also has proportionally less surface area so there is proportionally less heat loss compared with a small cluster. A large cluster also contains more bees that can act as insulators and heater bees. A small cluster may not have enough bees to maintain cluster temperatures in very cold weather.
Individual worker bees can fall off the mantle and perish when the temperature of this outer layer falls below 8 ˚C. Meanwhile, in the cluster centre the temperature is usually maintained around 20˚C when there is no brood rearing. This changes as soon as the queen begins egg laying again around the winter solstice and the colony’s core temperature increases to be maintained at the best temperature for brood rearing which is between 30-35 ˚C. Naturally, more stores are consumed to raise and maintain such temperatures which is why the colony’s need for energy is greatest in early spring, and why this is the time when colonies often starve.
To create heat by contracting flight muscles, bees must also use carbohydrates from their stores and oxygen from the atmosphere. They exhale carbon dioxide (CO2) during respiration which also produces water creating moisture and humidity in the hive. Honey bees can cope with high levels of CO2 which would be toxic to humans.
In a natural tree cavity, the nest is lined with propolis giving a shiny and almost waterproof coating to the cavity walls. Propolis is also used to reduce the entrance and seal draughty chinks, thus preventing some heat loss. The entrance is usually below the cluster so any ventilation is also below it, which has the great advantage of allowing a relatively warm and humid atmosphere to exist around the cluster and brood nest. This means that water stays trapped in warm air and only condenses when it hits the cooler sides of the cavity where it runs down, thus avoiding wetting the brood nest and the clustered bees.
In hives, we can create a similar environment if we provide top insulation above the cluster and ensure that ventilation only comes from below it. However, if we provide top ventilation using such methods as propping the crown board slightly open with a matchstick, we create a poor environment where the cool air coming in at the top causes water to condense and fall straight down onto the clustering colony rather than running down the hive walls.
Some moisture is used by the colony to dilute stores and the bees obtain it from the hive walls and crown board in winter, which saves risky trips outside. John Gaut4 has observed and filmed bees collecting water from a Perspex crown board/ inner cover during winter and he describes how these bees would otherwise have to take big risks of fatally cooling by going outside to collect water which is essential for producing brood food and diluting honey.
The advantages of top insulation are, as you see in the second photograph, less condensation under the crown board and a warmer upper part of the hive where the cluster forms because heat is not lost from above. This means that the cluster can be looser making movement to collect stores much easier. Being warmer also means that fewer stores are consumed because the clustered bees do not have to work so hard generating heat to maintain the cluster core temperature. It is important to remember, though, that adding insulation does not add heat, -; it only prevents heat already there from being lost.
Gaut’s work shows how an uninsulated cover board causes abundant and frozen condensation to form above the cluster compared with an insulated cover in which the condensation is minimal and unfrozen which allows access for water collection. Professor Seeley5 describes these bees as “water bottle” or water reservoir bees and their role is fill up on water and store it in their honey crops until it is required by other bees then it is exchanged by trophallaxis.
By- products of digestion build up in the rectums of honey bees over winter and are stored there until there is a day of good weather that allows them out to defecate. If you ever get the chance to dissect a winter bee under a microscope, you will be amazed at how the rectum almost fills the abdominal cavity.
Should food supplements with excess water have been given when it was impossible for it to be evaporated because the weather grew cool, then instead of normal, yellow, semi-formed bee faeces one might see brown spattering on the outsides of the hives, or inside them on the frames. We call this dysentery because we have no other name to accurately describe it, but it is not dysentery in the true sense of infection. Nor is it true diarrhoea and it may be a one-off event and harmless. It is a situation where there is too much water in the gut. However, when we notice it, we must be mindful of nosema infections and be vigilant. This is where the local association’s microscopist can help with a diagnosis and you can bring along a sample of 30 bees from an affected colony for testing.
The Cycle Continues.
If you are fortunate, your bees will do well over winter. As the queen begins laying in December, the colony naturally builds up in numbers, albeit slowly, and prepares for swarming in the late spring. When the first pollen- producing plants flower you will see bees return with corbiculae laden with pollen. Sunny days will encourage your bees to take flight to evacuate full rectums and you will rejoice, even if the laundry gets spattered.
1 Matilla, HR and Otis, GW (2007). Dwindling Pollen Resources Trigger the Transition to Broodless Populations of long-lived Honey Bees Each Autumn. Ecological Entomology 32:496-505.
3 Wilson, H. F., and V.G. Milum. 1927. Winter Protection for the Honeybee Colony. Research Bulletin of the Wisconsin Agricultural Experiment Station. No. 75: 1-47.
4 Gaut, J. A., 2021, The Benefits of Providing Good Hive Insulation but No Upper Entrance in Winter. The American Bee Journal October 2021.
5 Seeley, T.D.S. 2019. The Lives of Bees. Princeton University Press, Princeton, New Jersey.