Discovering one of our bee hives is dead, or a “dead out”, in the middle of winter is always a sad occasion. It always raises the question, “Why did my honey bee hive die?” We know it is challenging to overwinter a honey bee hive in the long, cold Montana winters but it can be done.
We’ve had numerous bee hives over-winter in the nine years we’ve been beekeeping. Unfortunately we’ve also had our fair share of honey bee colonies that have died.
Whenever we discover a bee hive has died and did not survive the winter, I take the opportunity to dismantle the hive and see if we can find some insights into why the honey bee colony may have died in the winter.
Exploring a dead-out honey bee hive is like an autopsy for the bee hive. My hope is that by learning some insights, we can improve how we care for our honey bee hives and hopefully have more hives successfully overwinter in the future!
Observing For Signs of Life
Before opening up a honey bee hive in the winter cold, you need to be sure the colony is dead. I walk by our hives regularly to observe signs of life and say “Hello Honey Bees!” to our hives who provide us with our beloved sweet honey.
When observing a hive for signs of life, I look at the bee hive entrances. If the hive is alive, I usually see movement of honey bees on the frames through the hole in the hive box. Occasionally I will see a honey bee fly out on a cleansing flight.
Another observation is a pile of dead bees in front of the hive. Honey bees will remove dead bees from the hive and place them outside.
By late fall, we had a little pile of dead bees outside each of our bee hives. After the next fresh snow in January, there were no new dead bees on top of the snow. I hadn’t been seeing any movement through the entrances to the hives and did not see any bees flying out.
I waited until we recently had an unusually warm 48 degree day to observe the hives for signs of life one final time. I knew it was definitely warm enough for the honey bees to fly, but there were no signs of life in either of our bee hives.
There was no need to listen to the hives with our stethoscope, I knew they were dead.
Determining What Killed a Honey Bee Hive
There are multiple factors that could cause a honey bee hive to die in the winter. In the nine years we’ve been beekeeping, we’ve had every one of these following issues happen to one of our hives at one time or another and cause a dead-out hive in winter:
Too much moisture:
If the hive is not properly ventilated, too much moisture will build up in the hive and cause the honey bee colony to die. One of the biggest signs we notice in a hive that dies of too much moisture is the presence of a lot of mold in the hive.
Starvation:
If the honey bees eat through all of the honey in their hive and don’t have any supplemental feed in the winter, the hive will die. We had this happen several times in our early years of beekeeping. It is an issue that can easily be prevented by supplementing the feed in the hive in winter.
I now make a point of checking our winter hives on a 50+degree day in January and each month after and place a sugar candy/fondant I make in the hive to supplement their feed. Since starting this practice, we haven’t lost a bee hive to starvation.
Weak hive:
Sometimes a honey bee colony is weak going into the winter and just does not have an adequate number of bees to sustain a warm cluster through the winter. We’ve had hives swarm in the summer, leaving too small of a colony behind to make it through the winter.
Breaking Cluster:
Honey bees may break their cluster on warmer winter days but will die if they do not re-cluster when then temperatures drop. In Montana we have drastic temperature changes that impact our bee hives and this isn’t something we can control. We do have our honey bee hives placed along a tree/shrub line that acts as a wind break to help reduce some impacts of the cold weather on the hives.
Sick Honey bees:
Sometimes you can see signs that your honey bees are ill or weakened. For example if they have a high Varroa mite count you can usually see the mites on the bees with your naked eye. Mites can make the honey bees more susceptible to other illnesses and weaken the colony (We use an Oxalic Acid vaporizer to treat for mites). We’ve also had a hive with Nosema one year which was easy to diagnose in winter.
Exploring a Winter Kill Bee Hive
To try to determine what caused a honey bee hive to die in the winter and be a dead-out, I start observing the hive and noting my observations as soon as I take the lid off the hive.
It’s helpful to have a basic understanding of what honey bees do during winter. Here’s an article that explains in a bit more depth about how honey bees cluster over winter.
I love doing a dead hive inspection with my kids since we feel like detectives looking for clues trying to solve the mystery of why the honey bee colony died.
The first hive we inspected this year was our strongest hive going into fall. I saw honey bees flying in and out of this hive in December AFTER the unusual artic cold snap of -22 below temperatures.
I was elated when I saw the hive had made it through that December cold snap and thought they would be a thriving, hardy Montana colony next summer.
I was so disappointed to discover no signs of life the last couple weeks and was curious to find out what happened.
When we took the lid off, we didn’t see any mold. I took off the inner cover and we could see a small cluster of dead bees in the center of the frames. I carefully started taking out the frames and inspecting them to see how much honey had been eaten.
The frames still had a little honey left, especially the frames on the outer edges of the hive box. The inner frames had a little honey but I could tell they had eaten a lot since the fall.
Since there were still honey frames in the hive box, we were guessing that the bees did not starve like we had happen in the past in our early days of beekeeping.
When I had all the honey frames removed from the upper box, we peaked down into the box below and could see some of the dead bees that had fallen from the cluster in the box above. I picked up several intact dead honey bees and looked at them closely.
I did not notice any deformities visible to the naked eye, which is not to say they couldn’t have had a disease that is more difficult to detect.
This hive was the stronger hive of our two new nucs when we harvested honey in the fall and had no easily visible health issues.
The second dead bee hive we inspected this year did not have any visible activity for several months.
There was a pile of dead bees in front of the hive in the fall but the last couple months I have not observed any movement inside the entrances of the hive and no bees flying in or out like in the other hive.
When we took the lid off, we immediately noticed at least a dozen dead bees. What was unusual was that they were not in a cluster but look like they died in place doing what bees do in their hive-it’s like they were frozen in place.
When I removed the cover, we noted more dead honey bees scattered around but there was no distinct dead cluster of bees like we saw in the other hive.
The absence of a dead cluster of bees tells us that the bees broke their cluster of warmth, likely on a warmer day, but did not reform their cluster to stay warm before they died.
Then we started pulling out frames to inspect them. The frames from this second dead hive were heavy and still really loaded down with honey.
The frames in the middle of the box looked like hardly any honey had been eaten.
We knew this hive was the weaker of the two hives so even going into winter we weren’t sure they would make it through. It’s always disappointing to lose a honey bee hive even when you know the chances aren’t good!
We’ll save these honey frames to put in the beehives later this spring when we install our new nucs in our beehives.
What killed our honey bee hives this year
I don’t know if we can ever be 100% sure what killed a honey bee hive on our homestead, but we can make an educated guess based on our observations.
I talked with my kids about our observations of the hives and what they thought happened. We know that both hives had plenty of honey still in the frames so we could rule out starvation.
We know the artic cold snap in December didn’t kill either hive since one was still alive after the bitter cold and the large amount of honey left in the other hive makes it seem like it died in the fall.
We are guessing that our strongest hive died because the cluster of bees was too small to keep warm through the most recent cold snap in January. We have had a long, cold winter this year and the cold temperatures started earlier than usual this fall.
The size of our hives were smaller this year because they were new nucs we bought in the spring. The cluster of bees we saw dead in the strongest hive was quite small and probably wouldn’t have been able to provide enough warmth to stay alive.
The second hive that appeared to have died earlier in winter didn’t have a visible dead cluster of bees. It had a bunch of dead bees outside the hive and scattered throughout the hive.
We knew this hive was smaller and weaker so we are not surprised it didn’t survive the winter. We also inspected dead bees we found in this hive and did not see any visible deformities.
Likely this hive died from the temperature fluctuations this fall when they broke their cluster.
This fall we didn’t see mites on our honey bees and didn’t see any visible deformities so we had high hopes for the hives making it through the winter. But maybe they had something else we couldn’t see?
Maybe next year if we notice one hive is a lot weaker than the other, we’ll combine hives to increase the chance of having at least one be strong enough to survive the cold Montana winters.
Moving Forward After Losing Bee Hives in the Winter
I know some beekeepers who become so disheartened after losing beehives in the winter that they quit beekeeping. We almost did that the first time we lost beehives in the winter.
But then I had a major shift in perspective and it’s completely changed the way I approach beekeeping.
After our dead bee hive autopsy, I talked with my kids about how it’s sad that our honey bees died and didn’t make it through winter.
But the positive is that we did care for them and provide a home for two colonies of much needed pollinators for over half the year.
Those honey bees helped to pollinate our gardens, fruit shrubs, flowers, trees and all the neighboring flowering trees, gardens and wildflowers.
So the question I’m sure many of you are asking: Will we get more honey bees this year? You bet! We don’t let a failure make us quit.
For us, beekeeping is about supporting our pollinators so even if a hive dies we know we’ll get another nuc, care for them throughout our growing season and hope they make it through the winter.
We know that beekeeping has it’s ups and downs, especially in cold weather Montana!
We learn from our mistakes and try to do better next year. Beekeeping is always a learning experience!
Who knows, maybe next year we’ll get lucky and have a hive over winter again like we did in the past.
And if not, we know we tried and at least helped the pollinators do their important work through another growing season in Montana!
If you want to learn more, here’s a helpful book with tips on how to help your bees get through winter
Have you had a bee hive die in the winter? What did you discover when doing an autopsy on the dead hive?
References:
I learned a lot of beekeeping knowledge by attending our local Beekeeping Club meetings and talking with beekeeping mentors. We also have several beekeeping books that have been helpful:
–Storeys Guide to Keeping Honey Bees
Leave a Reply