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Keep honey bees dry and draft free

After writing a post about upper entrances in winter, I received a lot of mail from beekeepers who insisted that an upper entrance in winter would place the colony at risk of freezing. My own experience with upper ventilation has been the exact opposite, and my colonies have thrived since I began using upper ventilation combined with a moisture quilt. Nevertheless, I decided I should consult other sources.

In Honey Bee Biology and Beekeeping (2013) Caron and Connor explain:

Colonies can survive very well without elaborate wintering preparations by the beekeeper as long as the bees are protected from winter winds and they are able to vent excess moisture. . . . Beekeepers should provide upward ventilation in every hive during the winter . . . An alternative is to place a wooden shim, carpet tack or stick in one of the corners at the top of the hive. Some beekeepers prefer to drill holes in hive bodies or use spacers or inner covers designed to allow air ventilation.

Beekeeping in Western Canada, published by Alberta Agriculture and Rural Development (1998), puts it this way:

An upper entrance is an important requirement for successful outdoor wintering. The colony cluster gives off water vapour as it respires, which rises to the top of the hive and must be allowed to escape.

A passage in The Hive and the Honey Bee (2015) is equally emphatic:

Thus, beekeepers in cold climates must provide an upper entrance to allow water to evaporate out of the hive by drilling a hole in the box or providing an inner cover with an opening in the rim.

In The Beekeeper’s Handbook (1998), Sammataro and Avitabile insist the winter survival depends on a number of items, including

“An upper entrance for winter/spring cleansing flight” and “Top ventilation to release moist air.”

Bees rarely die of cold

Although it is written in many texts and papers, beekeepers tend to forget that bees are extremely well adapted to staying warm in winter. Contrary to popular thought, they do not keep their entire hive warm in the way a human keeps a house warm, instead they only keep the cluster warm. This is aided to some extent by the structure of the hive, but even open-air colonies can survive a moderately cold winter if they can stay dry and out of the wind.

In chapter 21 of The Hive and the Honey Bee, Currie, Spivak, and Reuter report that a cluster of 16,000 bees can survive -112°F (-80°C) for 12 hours. That is an amazing feat, but to succeed at those temperatures, the cluster must be dry and free of drafts.

This phenomenon is easy to reproduce. Just go outside wearing your regular clothes on a 40°F day (4°C) for 15 minutes. Then try it again wearing the same clothes doused with water. Evaporation is a cooling process. When the water on your skin evaporates, it makes you cold. It will evaporate even faster in the wind, which makes you even colder.

Finding a compromise

Dry bees can withstand extremely cold temperatures, but as they say, a wet bee is a dead bee. So your priority for wintering bees should be to keep them dry and out of the wind. Yes, ventilation provides some amount of air movement through the hive, but there is a give and take between too much and not enough. The trick is to find the sweet spot in the middle.

My enthusiasm for moisture quilts is partly due to this give and take. The moist air moves through the wood chips, condenses on the inside of the lid, and rains down on the chips. The chips collect the moisture and then dry slowly. They dry because the space above the chips is vented to the outside. Once dry, they are ready to collect again. And since the air going through the chips does not have a straight-line path—it must wend its way between chips—there is very little draft inside the hive.

Bumble bees can do it too

The amazing ability of honey bees to keep their nest warm is shared by other bee species as well. In A Sting in the Tale (2013), Dave Goulson describes how he had to destroy a colony of bumble bees because they were brought into his country for research only and could not be released. He decided that freezing them would be the most humane way to kill them, so he put the entire colony in a freezer at -30°C (-22°F). He writes:

The next day I came back to find the colony very much alive and buzzing loudly; the workers had gathered into a tight clump over the brood and were presumably shivering at maximum capacity. The queen was hidden in their centre, and seemed quite unperturbed.

A convenient opening

As I mentioned in my previous post, An upper entrance in winter, before this year I never used an upper entrance, only a number of ventilation ports above the wood chips. This worked fine, but this year I added an Imirie shim with an entrance just below the candy board.

All of my colonies have taken a shine to this opening, peeking out of it on cold days and flying out on warm ones. In fact, the bees in all my hives seem to have abandoned the lower entrances altogether. I wondered about this, but realized that part of the attraction may simply be that it is close. As winter progresses, the cluster moves up. How much easier it is to exit through the top, than to go down three stories and exit through the bottom?

Of course, there may be more to it than that, and it will be interesting to see what they do as the winter warms into spring.

Rusty
Honey Bee Suite

Comments

Bonnie G.
Reply

Hi Rusty! We had a 65 degree day yesterday and I checked my 2 hives. Much to my delight, they are doing great but their stores are low. I made sugar bricks in square cake pans for them last night. I have my hives set up much like yours – 2 deeps, the honey super, Imirie shim, queen excluder and lastly, the quilt box and hive top. I put burlap on top of the queen excluder and then wood shavings (guinea pig bedding). My ladies are dry and even the quilt box contents are dry.. I will gently raise the burlap up and slide a sugar brick in on top of the queen excluder so they can get to it. To keep drafts out that may come up through the bottom, I slid the debris board in under the IPM bottom board and I left the slatted board on, also.

I make my sugar bricks by adding 7-1/2 ounces (weighed on a scale) of hot water to 5 lbs. of sugar. Mix well in a large bowl until all the sugar is wet. Use a spatula and put the wet sugar in a pan. I used square cake pans. Mash the wet sugar down real good. Place the pan(s) in the oven over night with just the oven light on. Voila! I hope this helps make life easier for someone.

Upper entrances are great folks!

Rusty
Reply

Bonnie,

I will try your recipe for no-cook bricks. I use one ounce of water to a pound of sugar, but I think a little more water would make them harder. Thanks!

Tom
Reply

Hi Rusty,

After your former article about upper openings, I put 3/4″ holes in the top. Even with temps down to -4 degrees, the girls use them to fly out to excrete and hang in the holes to look around!

We are tired of Snoqualmie Pass and are putting our Ellensburg house on the market. We are searching for a house somewhere around Olympia.

Tom

Rusty
Reply

Tom,

I remember you talking about moving out here. Grandchildren in the area, if I remember correctly? I hope you like rain, though!

Stephen
Reply

Last winter our little sisters used propolis to reduce the upper entries to about half a centimeter. I had bored a hole the size of a wine cork in the top box. I think the bees determined how much ventilation they needed.

Rusty
Reply

Stephen,

Yes, they will do that. The Carniolans do it more than Italians, and Caucasians do more than anyone.

Terry
Reply

Hi Rusty,

Beekeeping here in Thailand is a little bit different (you had a piece from a contributor on their experience last year about how it is done). Recently we had a cold snap where temperatures were in the single digits centigrade.

According to the forums here a number of beeks lost entire hives and one of my hives had a major setback. This hive had been doing well and was relocated north to Phetchabun and immediately started bringing in large amounts of pollen. It was not a really strong colony (about five or six frames of brood in a 12 frame box that is used here with only a small amount of nectar and no capped honey) and after the cold snap there were numbers of dead bees and brood. Mortuary bees were clearing larvae from the hive and many new bees were dropping outside the hive entrance. Frames outside the centre of the cluster had dead brood in them but the queen and a good number of bees survived.

The practice here (and not one I subscribe to) is to harvest nectar every 7 days, some do 5 days, resulting in what I consider to be very weak colonies of 4 or 5 frames because they think that having brood takes up room for storing honey and it is the honey that makes them money. To my mind they have colonies that are always on the point of starvation and fed sugar to compensate for the high rate of harvesting. I would assume that this compromises the immune system of their stock because they don’t get a normal diet during the honey flows.

The Beekeepers who did not lose bees during the cold snap fed syrup to their hives when they heard the weather forecast and did not suffer losses. Unfortunately they did not communicate this advice to the forums and many others suffered catastrophic losses. Others merged two hives into one to give them enough numbers to cope.

I know in the northern hemisphere you talk of summer bees and winter bees so I was wondering if after forty years the bees in tropical countries have acclimatised and now cannot cope with cold, even when those temperatures would cause no problems to European and North American bees.

Finally thanks for your work on your blog, I find it very informative and thought provoking.

Kind Regards,

Terry

Rusty
Reply

Terry,

They can’t keep warm without enough to eat, so maybe that was the problem? Keeping warm takes lots of food.

Andrew
Reply

In Alberta we say “a wet bee is a dead bee”. We ALWAYS keep our top entrance open.

Gary Brain
Reply

I have found that in the high desert my hives have done better with a top escape (entrance). Moisture even in the high desert is a problem and without a way for the moisture to escape the hive will surely suffer. Some will survive but the plan is to get as many colonies through out the winter as possible. Any thing we can do to enhance that is to the good.

Michael Green
Reply

My bees are still using the bottom entrance but have also started using the top one. I never noticed them using it during the summer. Maybe it’s just more convenient, kind of like having the option of using the front door or back door.

Bob Simpson
Reply

Can I get a picture or plans for a moisture quilt?

Bob Simpson
Reply

I have an above ground pool and each day during the swimming season, I pull about 25 bees per day from the pool, some dead and some not. I realize 25 is not a significant number considering the egg laying capacity of a queen, but I don’t like to see anything die needlessly.

I’m looking for a light weight, floating cover that can keep my bees from drowning. Not looking for a solar cover, the pool is already warm enough. And I do keep another water source nearby, but perhaps the bees are being blown into the pool by winds.

Any suggestions? Thanks.

Rusty
Reply

Bob,

I don’t have an idea for a cover, sorry. But it is believed that bees locate water sources by odor, and they can learn to identify sources by their scent. So pools with chlorine or salt become recognized as water sources. Very difficult to change their habit, once established.

Greg
Reply

Hello Rusty,

We are in Canada and one hour north of Montreal with four hives. We position the hives against each other in a cube with two inches of Styrofoam on all four sides, top and bottom. The key to their winter survival is keeping the bottom and TOP doors open and free of snow. We have discovered the hard way what damage moisture accumulation can do to the hive. The bees use the bottom doors for removing dead bees and the top door for bathroom breaks when possible.

Some times ice forms over the upper door as they ventilate their home!

Vince
Reply

In my neighborhood I noticed the bees on honeysuckle with pollen on back legs. Are you using the pink grease patties this year? Have Bee-Pro I made up from your recipe and placed it in cat food tin cans, this is just tall enough to slide in quickly. Will make moisture boards for next year. Have drilled upper holes on most all supers. Hope to go from 9 hives to 14 this spring. Going to use a Nozevit Plus sugar spray to help with Nocema and do something for the mites all in late Feb. You can get Nozevit from completebee.com.

Rusty
Reply

Vince,

I haven’t used grease patties in a few years. They always looked the same when I took them out as when I put them in. I’ve heard good things about Nozevit, though.

Margot Rideaux
Reply

Bonnie, do you line the pan or does the cake just pop out?

Bonnie G.
Reply

They pop out. When I mash the sugar down in the pan, I take the spatula and go around the edges to make a nice rounded edge. I plop them out on a piece of wax paper.

Katherine
Reply

Hi, Rusty,
We have Warré hives, so the “quilt” is part of the hive design. I don’t usually give them an upper entrance, but something happened the other day which made me rethink that. We had a 15 -18″ snowfall (fairly rare for our location in KY). I know that hives “breathe,” depending on air exchange through the entrance. Light snow is no problem, but as snow melts it packs and can suffocate a hive. When I went out to clear our entrances, which are much smaller than a full-width langstroth entrance, I found that on the strongest hives the breath of the colony had created an ice barrier about an inch away from the entrance, several inches deep and an inch and a half high. If I hadn’t cleared, they’d have been in trouble. An upper entrance would be a nice backup plan in such a case. If I had an out apiary, I would definitely provide every hive with a small upper entrance.

Rusty
Reply

Katherine,

Right. The Canadians with all their snow are adamant about their upper entrances, and that is one of the main reasons.

John Zone 5
Reply

Do you leave the screened bottom board open all winter with an upper entrance?

Rusty
Reply

John,

Some do and some don’t. It depends on local conditions, amount of wind, and strength of the colony. I leave screened bottom boards open all winter, and this year I had upper entrances open as well. Sometimes, if a colony is small, I close the screened bottom when the temperatures are below freezing for an extended period.

Travis
Reply

This year I thought I would “help” my bees out by pushing three hives together and wrapping them as one so that they could share the warmth. Unfortunately it has been a very mild winter in northern British Columbia. I have opened up the lids on the outside hives a few times and everyone inside was quite happy, I didn’t check the inside hives though as it was more difficult to open them up.
Well the other day I opened all of my hives only to find the middle ones all dead. They had starved. They had lots of stores at the start of winter but I think by putting the hives together the inside ones were too warm which caused them to go through there stores much faster. I think if we would have had a typical winter with cooler temperatures then this may not have happened. I have since separated my remaining hives and have added frame feeders with a thick syrup. The remaining hives look great, large clusters and lots of bees out flying around on warm days.

chris conrad
Reply

HI Rusty,
I’m going with a different opinion here. I remove bees for a living here in Sonoma County. Here too, the “push for ventilation” is very strong. Yet I see how bees live and when the have ventilation, they always, always, try to plug it up. We have a certain type of inner cover that has a 2 inch screen at one end. If I put that on a healthy set of bees, they will propolize it all in. What a tremendous amount of work. I believe that bees do not like us leaving the window upstairs open letting all the heat out. Think of a tree, most of the time, there is no opening at the top. They like it dark, claustraphobic, and stuffy in there. If they didn’t, they would leave the screens alone, and not try to propolize them all in every single time.
Chris

Rusty
Reply

Hollow trees don’t have upper openings but they can absorb much more moisture than milled lumber. Hollow trees are often punky and behave very much like a sponge, something milled lumber just does not do. If I were keeping bees in hollow trees, I would not provide upper ventilation or upper entrances.

dgrc
Reply

I’ve had a temperature and humidity monitor in my single backyard hive all winter. I have a 1″ diameter hole in the top box, BildRite moisture board inside the telescoping cover. The telescoping cover is propped ajar. Long story short — humidity is fine — tends to track a little moister than ambient. So is temperature — a steady 65 F. The girls hang out in the hole. The biggest problem is that they decide to fly out and poop, then freeze.
On a recent warmish day, we popped the top cover and saw a healthy, active hive. Peering down the frames we saw what should be enough capped honey to hold them until spring.

Larry Burden
Reply

I am new to the hobby and started my only hive last July. With that said I wanted to make sure my bees had every opportunity to survive a cold Canadian winter so I did a few things to help. First I installed a fence panel to deflect the prevailing wind. I wrapped the hive in tar paper and placed three bales of straw against three sides of the hive. Most importantly for me, was the fact that I did not take any honey from the hive including the two small frames of honey.

My top board has a notch in it so I didn’t have to drill a hole. I have a screen bottom and other than the piece of white plastic on the screen I did nothing to insulate the bottom. Heat rises and anyone who has slept in a snow bank quinzy in the winter knows that the cold air is held down by the warm air above it. So with the screen bottom the entrance rescuer hole and the top hole my bees are doing quite well. The other day (Feb 28th) it was 6 degrees C (42.8 F) and my girls were out enjoying the sun, I have fed them 1:1 sugar water throughout the winter and they have happily consumed every drop. So I am a firm believer in having a top hole for ventilation and allowing the bees to play peek-a-boo.

Loralei
Reply

Hi Rusty,

We recently moved to central/northern BC (just north of 100 Mile house). Given the depth of the snow we receive, I closed off my lower entrance, and went strictly to upper. Yesterday was warm, so I checked on the bees, only to find a pile up of dead bees behind the closed lower entrance (also dead bees on the inner cover, which is my top entrance).

My setup is 2 mediums on top of 1 deep, inner cover, shim, and ventilated box on top, with a double height bee cozy. I cleared the pile of dead bees, and left a reducer on the bottom, which lead to bees coming out and flying. What I don’t understand, is why all the dead bees? This year has been rough, with losing 2 of 3 hives – and I’m worried that whatever the cause, I may not have a big enough colony to overwinter now (of course I had to close up quickly yesterday, as rain was on its way).

Rusty
Reply

Loralei,

In summer, a large colony loses about 1000 bees a day. In winter, that number drops significantly to perhaps several dozen per day. Still, that’s hundreds per week. To me, it doesn’t sound like anything is wrong. Usually by spring, I have a couple of inches of dead bees on the bottom boards of my healthiest colonies.

Loralei
Reply

Thank you for the response. I was worried that having the huge pileup of dead bees might compromise the immune system of my survivors, and totally forgot about daily expiration rates. I can sleep more soundly now.

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