. . . and we are itching to get into the hives! But with our unpredictable spring temperatures, it’s still too early to be breaking the seals the bees make between the hive bodies. We can do an assessment, though, to determine which hives will likely make it until mid-April and which ones are already “deadouts”.
What causes winter losses?
Probably not what you would expect. If you read “How do honey bees survive our cold winters?” from February 22, 2021, you know that honey bees are very good at regulating the temperature inside the hive; therefore, cold temperatures don’t effect them that much.
In our experience, there are 5 factors that mean certain death for a honey bee colony:
- Viruses from Varroa mites (more about that to come in future posts)
- Not enough bees
- Lack of food
- Sudden temperature fluctuations
Varroa destructor, a parasitic mite that feeds on honey bee fat bodies, is Public Enemy #1. They were first introduced to the US from Asia in 1987 and are the greatest cause of honey bee losses around the world. In the process of feeding on fat bodies, the equivalent of the liver in mammals, these mites deposit at least 5 known viruses. And just as the mosquito is a vector to deadly diseases in mammals, so are Varroa to honey bees. These mites are present in the colony all year long but reach their pinnacle in fall, just as the size of the bee colony starts to decline. If not kept in check, Varroa means certain death for a colony. Until bees can develop resistance to this predator, managing and controlling Varroa levels is the most important job of the beekeeper.
It takes a lot of bees to keep a colony going through winter. Besides the regular life expectancy losses (life cycle is normally 45 days), the queen stops laying eggs to preserve food. That means the losses are not being replenished. If the colony becomes too small they are not able to generate enough heat to thrive. Our job as beekeepers is to assess the size of the colonies in the fall and combine smaller colonies with stronger ones for optimal winter success.
While most people suppose that falling temperatures are the cause of winter colony losses, it is actually moisture that builds up in the hive that spells a death sentence for the bees. Respiration continues and without proper ventilation has no where to escape. The warm air hits the cold cover, condenses, and falls back on the bees. As we humans know all too well, being wet and cold is much more problematic than just being cold. We, as beekeepers, have two ways of addressing this problem: 1) provide ventilation holes for warm air to escape, and 2) place a box with pine shavings on top to retain the warm air and catch any drips that may occur from condensation.
After our first winter of keeping bees, we opened one colony to find a cluster of dead bees with their heads inside the cells. It looked like they had starved, yet there were plenty of frames of honey left in the hive. How could they have starved? During the winter, bees stay huddled together in a cluster. The bees on the outer perimeter get food from the surrounding cells and transfer it in toward the center “bee-to-bee”. As the food supply in one area is depleted, the whole colony will move upward as a single mass. A traditional hive contains 10 frames of honeycomb in one box. Most beekeepers in our area run two stacked boxes. The cluster is found on the centermost two or three frames, beginning in the bottom box. That means the honey found on the other seven frames in that box is inaccessible to the cluster during the coldest part of the winter. And once the colony has moved up it doesn’t move back down until nightly temperatures are above 50°F. It is very possible for a colony to run out of food and still have 10 or more frames of honey left between the two boxes. Our job as beekeepers is to make sure there are food resources above the colony. We place a candyboard or granulated sugar just above the top frames as “emergency feed” so that the bees have something to eat should they progress to the top of the hive and run out of food. This is most critical during this time of year when the queen is starting to lay eggs again and they colony is expending energy by moving around but there is no nectar to be found and it is still too cold to venture from the cluster.
You know those occasional days we have that start out warmer than usual until the temperature drops 30 degrees in a matter of a few hours? Those conditions are life-threatening to bees and we have lost several colonies in the past due to temperature fluctuations like this. During the warm, sunny part of the day the bees break cluster and begin cleansing flights (defecating). The temperature begins to drop and they don’t have enough time to get back into cluster. It’s a very frustrating situation to be in as there is nothing we can do for them, short of wintering them in a controlled climate. So as most farmers, we hope and pray that they make it through. Some do, but others aren’t so lucky. We lost 8 of 10 hives to a cold snap like this in March 2018. It was heart breaking!
I hope you have learned two things from this post. First, cold winter temperatures don’t mean sudden death for the bees. And secondly, “beekeeper” is a misnomer. We are more likely “bee helpers”.
As for that assessment we did today? Right now we have a survival rate of 18 out of 22 hives. Almost 82%! But we’re not out of the woods yet. Things can change a lot in a month, as proven in 2018.
Want to know how you can help the bees? Stay tuned!