A staggering amount of information is available in the colony management archival bee literature on wintering procedures. Truly, entire books could be written on this single subject; however, in this article and others to follow, I will try to condense wintering information to a manageable bulk. It would appear that honey bees are still a warm climate species. Wintering is still a challenge for them and for beekeepers.
Succinctly stated, during an average Winter, the percent of Winter kills has been rising. At meetings, you and others like you have repeatedly said that Winter kills are now more common than a few decades ago. I admit that I have had to work more to keep more of my bees alive, and they still seem weak and lethargic when they do survive.
In 1915, E.F. Phillips1 wrote, 'The beekeepers of the United States lose at least one-tenth of their colonies of bees every Winter . . . This loss is largely due to carelessness or to lack of knowledge, and it is entirely practical to reduce it to less than one percent, the small loss covering various accidents which cannot be foreseen.' When confronted with today’s beehive issues, Phillips’ comments appear harsh. Having not been around in 1915, may I assume that honey bees were less subjected to exotic pests and predators then than now? While it may be true that we still suffer from a lack of knowledge, I am defensive when charged with being careless. The routine mandate by speakers from the podium to 'keep your colonies strong and healthy,' is frequently impractical. There have been runts and sickly beehives as long as people have been keeping bees. (But there now seems to be more runts and sickly beehives – based on the published beekeeping literature.) Lastly, it is no longer realistic to say that it is practical to routinely reduce Winter losses to around one percent. As is 1915, those days and those statistics are long gone.
'The causes of the death of individual bees or of a colony of bees in Winter, barring unusual accidents, are only two in number: (1) Inadequate stores and (2) excessive heat production.' We now know that there was more to Winter losses than those two parameters – but they remain important.
Starvation is still a common cause of Winter colony losses. Researchers past felt that abundant, quality food stores were necessary for heat production, to sustain adult bees, and to provide for later Winter/Spring food for brood. Starvation is not as easy to address was advised in the old publications. Feeding bees carbohydrates can incite late season brood rearing rather than provide food for storage. Secondly, some colonies simply seem never to learn to use feeders or to store the supplemental food.
I must write that too much heat was not the listing I was expecting from the old literature. Results of early research indicated that at hive temperatures between 57° - 69°F, a normal broodless colony of bees does not form a cluster – but the bees remain inactive on the comb. Drop below 57° and a cluster begins to form. Drop even lower, and bees in the center begin to use muscle energy to generate heat. Ultimately, as a colony is subjected to long coldness, the insulating shell of bees begins to fail and die. As the shell becomes increasingly ineffectual, the core bees are required to produce more heat. So, it is not that the colony produces so much heat that it cooks itself, but rather that the colony is required to produce high levels of heat to make up for decreasing cluster size.
As the wintering cluster eats an ever increasing amount of food and if the food has indigestible components to it, bees will accumulate and store increasing amounts of feces in their rectum. In 1915, it was felt that high heat production resulted in large food stores consumption which resulted in feces accumulation. If the heat requirement was great enough and feces levels rose high enough, the bees could no longer contain the waste products and would defecate within the colony. This condition was called dysentery by olden beekeepers.
Now, in 2009, we know this line of thought to be only partially correct. No doubt small clusters would be required to eat disproportionately high levels of stores which would result in feces accumulation. Cleansing flights would be required. But a great part of this problem could very well be digestive pathogens such as those caused by Nosema infections or viruses. So we know more about the hive health than scientists past, but the concept of increased food consumption causing increased need for cleansing flights is still appropriate. With this in mind, an issue that is relevant today is corn syrup – is it a good supplemental wintering food source or are there problems with it? Currently, we don’t have clear answers.
Honey bees emerge into the world with a fixed amount of life’s energy – somewhat like a dry cell battery. Clearly, if this reasoning is correct, young bees are needed to survive the prolonged periods during Winter months. Brood rearing late into the Fall months assures the colony a good population of young bees for this purpose. The dead bees that accumulate – even within a healthy wintering colony – are indicators of old bees dying as the heat generation processes uses the last of their energy.
In the beekeeping literature, Spring dwindling has had many descriptors. Colony Collapse Disorder (CCD) may or may not be a modern name for conditions that have been called Spring Dwindling, Autumn Collapse, Vanishing Bee Syndrome, or Disappearing Disease. In the early 1900s, Spring Dwindling was expressed by colonies that survived until Spring, but then slowly dwindled maybe to the point of dying. The authorities of the day felt that the heat production required of bees during the Winter had used them up and that the balance of young bees versus older bees was awry. The colony had gone into Winter without enough young bees. Again, current guesses are that other factors such as genetics or disease may be playing more a role than simply colony make-up.
The queen’s role was clear in 1915. She provided the young replacement bees for the season – including the Winter season. She was able to increase brood production rapidly in the Spring. But other than this important, indirect contribution, she played no direct role in the actual wintering process. Today, that concept is still mostly believed – but not quite. The queen does not have a physical role in the wintering process, but the genetics she extends to her offspring are critical in the colony being able to survive the Winter.
A large cluster is, in all ways, better suited to survive the Winter than a smaller cluster2. There are fewer bees for insulation duty. The interior bees must generate more heat so they use their resources faster. As the interior bees increase the core cluster temperature to offset a reduced cluster insulation layer, the interior temperature of the brood nest is raised to the level appropriate for brood production. Even today, beekeepers can see brood production in small clusters during cold months. The old recommendation was to – so much as possible – limit brood production until the bees had free flight. Whether the brood production in a small cluster was unintentional or was an effort to produce brood for replacement bees, the final effects were the same – the colony used its resources even faster and probably died as a result.
In addition to a healthy colony and a good queen, colony packing was routinely recommended in the early 1900s. On many occasions, I have wondered why that recommendation passed into obsolescence. We insulate our homes, our work places, our clothes and our automobiles – yet bee colonies didn’t need help. The arguments for and against Winter packing are extensive. Labor, bee physiology, and climatic conditions are all fundamental areas of discussion when considering whether or not to pack. It was stated that a beekeeper cannot insulate a colony too much nor can a colony be too strong going into Winter.
The U.S. beekeeping industry went through a period of time when colonies were packed in groups of four3. The phase went (I estimate) from the late 1800s through the late 1930s. Photos and instructions are commonly available, but I have never seen the procedure used to winterize colonies. In the warm months, four colonies sat upon a platform that would become the base during Winter months.
About the time of the first killing frost, the colonies went into the packing phase. Sawdust or wood shavings were frequently used as insulation materials. Rags, leaves, and paper were also common materials. Sawdust would hold escaping moisture so colonies had to be packed properly. Packing should NOT be done after Thanksgiving. It was found that late packing resulted in the colonies increasing colony temperature and initiating brood rearing.
The packing crate was collapsible and was reassembled with screws. The four colonies were raised to sit on a simple 2x6 frame. Hive entrances were modified to be longer and to align with the entrance in the packing crate. The four crate walls were attached, and sawdust (if used) was loosely poured under, around and on the four colonies. An air space was left at the outer cover of the crate so the container was not packed full.
The final container was a large 'doghouse' looking box with a flat lid. Entrances to the outside were present in order to allow the bees free flight on warm days.
Surprisingly, there was little hurry to unpack the colonies. May 15 would have been acceptable but leaving colonies packed well into Spring was not uncommon. If the beekeeper needed to check the colonies, some of the insulation was removed.
In 1915, wintering colonies in two deeps was just becoming a reality. It would seem that for a while some colonies were packed while others were left unpacked in two deeps. For a while, companies such as Root and Dadant manufactured hives that were double-walled and insulated with chaff. Occasionally photos are found showing these 'puffy' hives with oversized hive bodies and oversized outer covers4. For photos and more detail, search double-walled bee hives in The ABC and XYZ of bee culture: a cyclopedia of everything ... - Google Books Result.
In more recent years, various corrugated board boxes (wax impregnated) were available. These boxes were slipped over the wintering colony leaving appropriate entrances for bees to exit when weather allowed.
Still another procedure for providing some insulation was to wrap colonies in black tar impregnated paper (roofing felt paper). The procedure was simple and the blackness was thought to absorb sunlight thereby providing solar warmth. Slats were tacked into the tar paper to hold it in place and entrances – both upper and lower were provided.
Winter is the long, quiet time in the hive. Yet the bees are fighting for their lives. Sometimes beekeepers can help while at other times their assistance is harmful. In upcoming Bee Culture articles, I will address topics such as indoor wintering and Winter cluster biology. When does packing help and when does it harm the bees? Successful wintering is a major aspect of successful beekeeping.
Visit www.honeybeelab.com for additional photos and reprints of some of the pamphlets I used in this article.
I am presently having problems finding firewood for the upcoming Winter. The Emerald Ash Borer (EAB) http://www.agri.ohio.gov/eab/ has very nearly been found in my front yard. Firewood can be moved into my county but not out of it. Much of the ash that would have been lumber (and firewood) has been chipped and put in landfills. I may actually have to go back to cutting and splitting firewood instead of buying it. I really need the firewood to help keep my family and me warm this Winter.
Bees need to stay warm in cold weather, too. Where does a wintering hive of bees get its firewood – of a sort? How does a bee cluster 'bump' its thermostat up on those cold nights just before dawn? As the beehive keeper, what are my responsibilities to the beehive as the temperature drops? These are hard questions with vague answers. Honey bees were keeping themselves warm long before I was ever a carbon-based being. They know a lot about their heating requirements while we are only just beginning to understand their needs.
The bees gather their firewood just as I do – they collect it, season it, and conveniently store it nearby. Rather than wood or natural gas, the bees’ firewood is capped honey. Bees gather their unseasoned fuel (nectar), season it (convert it to honey) and then store it (place it in capped honey combs). Honey is the specialized fuel burned by the colony’s furnace. Each little cell of honey can figuratively be compared to a miniature barrel of fuel oil or a few sticks of firewood. And where is the hive’s heating furnace? It’s within each individual bee. Each bee consumes honey, metabolizes it (burns it) at the cellular level and produces heat and muscular energy. Each individual bee’s heat is contributed to the cluster and communal heat is produced – in some cases, a lot of communal heat.
The manner in which a hive population warms itself is delightfully simple so long as you don’t mind being extremely close to your neighbors – really physically close – so close that another is touching you on all sides all the time. Let’s suppose that for some unfathomable reason, about 20 lightly dressed people were put into a room and the temperature was slowly lowered. At first, little notice of the coldness would be given. After a short while, our test group would begin to move around, inquiring about the availability of hot coffee and complaining about the encroaching cold. At an even colder temperature, our twenty cold people would begin to exhibit agitated movement (we, too, as human-things, generate heat at the cellular level). Clumps of shivering people slapping themselves and loudly complaining would begin to form. Approaching hard cold, all inhibitions would be lost and our 20 people would pack together trying to produce communal heat. Those inside this human cluster would be warmest while those on the fringes would be the coldest, ergo my human comparison to the wintering bee cluster.
Individual bees are cold blooded, but a healthy cluster of bees within a hive, with honey positioned correctly, has a great deal of control over its group temperature. As the outdoor temperature approaches about 55-57°F, depending on wind and sun conditions, bees within a hive begin to loosely centralize themselves near the bee nursery area (the brood nest) or near stored honey combs if the nursery has already been closed down for the season. As the day really cools to the 40s or so, bees will have clearly centralized themselves and will have begun to cozy-up. Colder still and the bees, just like our chilled, hypothetical human test population, will compact tightly. Some bees are in the interstices between combs while others are laying head first in empty cells. This tight configuration forms a solid, living cluster having roughly the volume of a soccer ball. The population at this point consists of adult worker bees, possibly some immature bees and the queen. No drones. They were all 'eliminated' during the Autumn and will be reproduced during the following Spring season. If baby bees are present, the nursery area will be kept at around 90-95°F while bees making up the outer layer will be nearer 40°F. If no developing bees are present, the center of the cluster will be around 70°F. Now suppose it gets really cold – down around 0°. Those bees making up the outer boundary get cold rear-ends, get agitated, and in their own bee way, begin to vociferously complain. This agitates bees that are closer to the center and that are warmer. All bees begin to flex (micro vibrations) their flight muscles, which increases the burn rate of their honey firewood, and the temperature of the cluster is increased. No honey = no heat = frozen bees. Every few weeks, a warm period is needed to give the cluster an opportunity to reposition itself onto more honey; carrying out the ashes is a human analogy for this. A bee cluster can withstand a bitter amount of cold for many weeks and survive very well. Indeed, the bee cluster may even survive better during a cold Winter. They live so closely that contagious Winter diseases can spread rapidly; however, some authorities feel that coldness suppresses bacterial spread.
The cluster’s composition
Other investigators speculate that the cluster is simply a condensed environment that is controlled by temperature. On warm days, the environment is opened up and bees fly freely. On cold days, in an effort to control the temperature of the cluster, the large environmental expanse compresses itself into a volleyball-sized volume. Nurse bees and the queen are at the epicenter while house bees and foragers make up the insulating shell. It is as though the bees’ environment collapses on itself. It goes from being acres and acres in size to hardly 10 inches in diameter. Just as in warm weather when nurse bees make decisions concerning the nest’s temperature needs, nurse bees make the Winter temperature decisions, too. Said a different way, the bees cannot heat the ecosystem to 60°F, but they can form a cluster and heat themselves to 60°F.
A comfortable bee
Another concept that is getting traction is that year-round temperature in the cluster is controlled by each bee doing whatever it takes to make itself comfortable. It becomes clumsy to try to write what a bee could be thinking, but individual bees are apparently struggling to keep themselves at a comfortable temperature in both Winter and Summer. When combined, that individual effort results in what humans see as cluster temperature control. So a cluster is made up 30 or 40 thousand individuals that are individually working to meet their individual needs. It is apparently not 30 or 40 thousand individuals working to meet the greater needs of the cluster. The bee is instinctually concerned about itself – not the cluster. Let me get back to you in 10 or 20 years to see if this concept takes hold.
Heat the cluster – not the hive
In my human comparison that I presented earlier, it’s important to point out that the room of cold people made no effort to heat the room, only themselves. In like fashion, the bees make no effort to heat all the space within the hive, only themselves. Beekeepers are frequently admonished not to open a hive during cold weather. It is said that they 'Will let all the heat out'. Not so. The temperature within the hive, excepting the cluster, is the same temperature as the ambient temperature.
I know where we get that impression. My three daughters and now my grand kids have made most of life’s decisions standing in an open door while letting out my expensive heat. Now, for whatever reason – and I can’t think of a good one – if the beekeeper should break the cluster, that’s another story. Dislocated bees will quickly become chilled and freeze. Much below 40°F and individual bees are in real trouble. Bees still within the disrupted hive will be unable to reform the cluster and conditions inside the cold hive quickly become desperate.
I have stood at one of my shop windows on snowy, wintry days, after nature has stripped everything to an outline, and marveled that my snow-covered hives, on that frigid day, actually had a hot spot within them that was at least 70°F. In essence, the bees are keeping their living room warmer than I am keeping mine. The snow covering is an insulating asset. In a reverse way, a hive covered in snow generally fares better than one sitting exposed and unprotected during Winter months.
Restroom breaks. Bees need them, too.
With all these warm ruminations about cold snow, it shouldn’t be surprising that the lower entrance to the hive will readily close shut with drifted snow. As this occurs, the beehive keeper can be of assistance to the wintering cluster. Providing the hive with a second, higher entrance allows the bees to get out on those occasional warm Winter days. The snow will have closed off the normal lower entrance. The upper entrance also serves to allow moisture-laden air to escape in much the same way that our human homes have ventilated eves and gables.
On cold Winter days, when all my family hops into the car, the windows quickly frost over. Ventilation is required to remove the window frost. When that small bit of warmed air rises from the warm cluster inside the hive, it quickly cools to the same temperature as that of the surrounding air. Cool air can’t hold as much water as warm air, so water condenses. In a very real way, it rains in the hive. An upper entrance allows for ventilation to let the warm air along with its heavier moisture load to exit the hive. It’s one thing to be cold, but it’s something worse to be cold and wet.
Throughout the Winter, when possible, bees from the wintering cluster are constantly checking the countryside for the first early Spring food sources, which are normally pollen snacks from maples and willows. Secondly, they need to go to the toilet. For practical hygienic reasons, bees don’t defecate within the hive, but rather relieve themselves in-flight producing yellow rain.
When the Winter weather briefly breaks, bees will take cleansing flights and will reposition themselves nearer their food stores as the afternoon temperature drops. An upper entrance and an occasional warm Winter day are good things for the overwintering hive.
Long-time enemies – bees and mice
An on-the-ball beekeeper will have restricted the hive’s lower entrance from its normal large opening to a slit not much larger than a single bee during early Autumn. Surprisingly, this is not to keep out the coldness, but to keep out mice. Mice, too, get cold during Winter months. What a great mouse place – that dark, somewhat warm wintering beehive. There are dead bees to munch on and protection from the elements.
In general, I don’t care for mice. Bees seem to dislike mice, too. Moving about through the wintering hive, the interloping mouse family causes constant disruptions. The agitated bees produce more heat, which uses more honey, which increases fecal content, which causes the bee colony to Winter more poorly. The beekeeper should be certain that the entrance reducing cleat be put in the lower entrance before the mouse family moves in. Otherwise the mouse group is effectively trapped within the hive making a bad situation worse.
What really happens in the wintering beehive is still mysterious. We know a good deal, but as beekeepers who are trying to help bees during cold weather, Winter becomes a quiet, trying time. Most of the help beekeepers can administer should be done during this time of the year. Next month, the final segment of this series will review what beekeepers can do and what they should do to help bees survive the Winter. A lot of guessing will be required.
Dr. James E. Tew, State Specialist, Beekeeping, The Ohio State University, Wooster, OH 44691, 330.263.3684; Tew.firstname.lastname@example.org; http://beelab.osu.edu/.