Many people argue that wintering honey bees seldom die of cold. Instead they die of starvation, either because they could not reach the food or because their food supply ran dry. In truth, the reason a colony dies in winter is usually much more complex than simply cold or starvation.
Thousands of bees but no food
When a colony dies of starvation, the results are often striking. I’ve seen huge populations of dead bees in a hive—dead bees piled deep on the top bars, crammed between the frames, covering the bottom board. Bees, bees everywhere and not a scrap of food anywhere. It is one of the saddest sights ever. But even so, did the bees die of cold or starvation? Once they ran out of food, they could no longer keep themselves warm. So which is it?
Similar questions arise every day. If a plane runs out of fuel and crashes, did the passengers die because of the crash or because the plane ran out of fuel? You can make many arguments. If the plane didn’t run out of fuel, it would not have crashed. On the other hand, the simple act of running out of fuel didn’t kill anyone, but the impact did.
Remember, honey bees are wizards at keeping themselves warm. When you see a dead colony, it helps to ask, “Could feeding the colony have saved it?” To me, that answers the question. If it’s obvious that lack of food was the ultimate cause of death, then yes, they starved. The bees ran out of fuel, just like the plane. When the fuel runs out, the wizards are toast.
A critical mass of bees
Bees die of the cold when the colony isn’t large enough or healthy enough to keep itself warm. To keep itself warm, the colony needs a certain number of healthy, well-fed bee bodies to generate the heat. How many bees is that? Well, assuming the bees are perfectly healthy, that will depend on factors such as the climate, weather, hive type, genetics, the distribution of the food supply, moisture accumulation, and protection from predators. I’ve seen baseball-size colonies make it when conditions are right.
On the other hand, if the colony lacks a sufficient number of healthy, well-fed bee bodies, all bets are off. If the colony is sick due to disease or parasites, if the colony is malnourished, queenless, or if the colony genetics is poorly suited to the environment, it may succumb to the cold. When the colony is not healthy to begin with, no amount of feeding, wrapping, supplementing, or general mollycoddling will make any difference.
The last straw
It is easy to look at dead colonies and say, “My bees died of the cold. They were fine before the cold snap, but that finished them.” This is like saying the passengers died from a plane crash when, in fact, they were doomed the second the plane ran out of fuel. To prevent catastrophes in the future, it helps to understand the ultimate cause.
Assuming a colony is healthy and has easy-to-reach food, it should be able to keep itself warm if it is large enough. The question to ask first is, “Why is the colony so small?” Maybe it resulted from a late swarm or a late split and is, in fact, perfectly healthy. If that is the case, your overwintering strategy should include ways to keep that small colony warm. Perhaps a little mollycoddling is warranted.
Sifting through the reasons
On the other hand, if the colony is small for an unknown reason—especially if it dwindled recently—it may not be healthy enough to overwinter. Many colonies, whose deaths were attributed to cold weather, were goners for other reasons. They couldn’t keep themselves warm because they were already sick or weak or being decimated by pests. A colony of sick bees won’t make it, no matter how much food you give them because food isn’t the limiting factor. As more die, fewer remain to keep the colony warm.
I don’t have answers here. My point is simply that the perennial argument about whether bees died of cold or starvation is often pointless. Instead of just blaming the cold, try to understand why your bees were vulnerable to cold in the first place. Once you have some ideas, you can tweak your practice and become a better beekeeper.
See the conclusion: “Bees head-down in cells.”
Honey Bee Suite