Bees have all kinds of fascinating tricks to stay warm and avoid freezing. Bees gather around their queen like a big cluster of grapes once the temperature drops below about 50F. She's in the middle. They surround her and vibrate their middle body segment, the thorax, to keep her and the whole hive warm. Bees, like many insects, also have a glycol component to their hemolymph (blood). This acts like an antifreeze and prevents the blood from forming ice crystals and freezing.
But, there are a lot of complicating factors to their efforts to make it as a hive through the winter months; I highlight several here. 1) Is there enough honey in the hive for the workers to eat as the bee cluster with the queen in the center moves up in the hive? This will be their source of energy for metabolism. Normally, for Maryland, we expect to have a few cold nights in winter, but this is already our second or third bout of single digits. Two weeks ago, we even got down to -1F! Unheard of here; a new term-polar vortex was in suddenly our vernacular.We would normally be fine with 60lbs of honey stored in the hive for the winter, but who knows with these low temperatures. 2) Is there enough ventilation? To stay warm, the bees vibrate their thoraces and keep the queen in the center of the cluster warm (as long as there is enough honey to eat to do so!) The temperature doesn't fluctuate much from about 92-95F all winter long. One must be sure that the top cover of the hive is cocked a bit to allow steam to rise and leave and not condense back on them as the hot air hits the cover to outside with cold air; moisture will promote disease causing fungi. The hive's bottom board allows for passive ventilation up and through the hive and out the top. But, below the hive, the bottom board area must be clear of obstacles, such as snow, to allow for this passive airflow to occur to heat the hive and cluster. 3) Are there enough bees to cluster and provide the warmth for the queen and hive? A healthy hive going into the winter months needs to have 60,000-100,000 bees present. 4) Is there a healthy queen present? This is only evident ahead of the winter by how well she is laying eggs and how she looks. (In the winter she is not laying eggs.) 5) Are there disease or pests present in the hive? Is the hive in general healthy? Varroa and tracheal mites, and small hive beetles are just a few of the many pests that my hives have experienced. A weakened hive having to fight pests, predators or disease will have a very hard time surviving the winter. 6) Is the hive location protected from strong northerly winds that bring rains, hail, sleet, ice and snow? The front of the hive (entry) should not face North. If some buffering device can be placed to prevent heavy winds, that is also ideal. In more northern climes, beekeepers often insulate their hives with things like tar paper wrapping. (I've never done this and do not know much about it. But, in places like Maine and Minnesota with prolonged periods of frigid temperatures, this is commonplace. 7) Is the entrance reducer on to the smallest opening? To help insulate the hive, you want the smallest entry opening available. YOU DO NOT WANT TO CLOSE THE HIVE! On nice days, the bees will take cleansing flights and need to be able to get outside. In areas that get heavy snow pack that might cover the entrance reducer down low, many beekeepers will create a second opening up higher in the hive near the top, by drilling a small opening. An opening must be present. If one can make it to the hive and sweep snow or ice off of the entrance to keep it free and open, that is best. But, snow breathes to some extent. Ice does not. 8) Can an ipm bottom board be added into the slot at the bottom of the hive? This will help to insulate the hive as well.
Beyond these illustrated steps, the beekeeper cannot do much more to protect the bees from winter's onslaught. It makes one wonder how bees in nature survive at all. But, they do. So, sometimes, even benign neglect is best! And, beekeepers can kill their bees with too much attention. It's a delicate balance knowing when to assist or not. Knowing that these queens originally came from Georgia in the Southern USA, I feel the need to assist them some.
Most winter bee kills are due to the cluster either getting wet and chilled/cold from moisture condensing and falling on them, or to starvation; either they don't have enough honey stored, or if they do, they don't move up into it properly. Yes, there can be enough honey in the hive, but as they move up into it through the winter months, the cluster may be off center to it and miss what's available all together. This is particularly sad when the beekeeper sees it. So close, and yet so far!
A friend asked me how to know if my bees were alive in the winter months, since I could not open the hive. (And, please DO NOT OPEN THE HIVE, unless it is an ambient temperature of at least 55-60F outside. The bees cannot fly at lower temperatures, and the hive will lose hard to replace heat.)
There are a few signs to look for. If the colony is alive, workers will be kicking out dead bees that were on the edges of the cluster, keeping the queen warm in the center. You will see their dead bodies on the landing board and in the front of the hive on warmer days as their sisters carry them out. (On frigid nights, there is a kill of those bees on the edges of the cluster, while the others in the center are at that toasty 94F! Since no new bees are being made-no eggs laid-at this temperature and time of year, the cluster will get progressively smaller as a result, with fewer individuals vibrating and generating heat.)
The other two traditional ways to know if your bees are still alive is to see them break cluster and flying on warm days, and/or to see them depositing fecal material on the front of the hive-little brown specks or flecks. On warm days (above 55F), the bees take cleansing flights to relieve their guts of the built up of feces and metabolic wastes. They do not need to fly far to do this; just out the door and back. (Amazingly, they can hold it all in until a warm day to do this.) So, if you see the brown flecks on the front of the hive when they were not there before, and it's been a warm day, this is a good sign.
The non-traditional approach would be to use an infra red camera to see a heat profile within the hive. I do not own an infra red camera, and because I'm still in a cast from an ankle surgery in mid-December, I can't get out to see how my bees are doing. So, I'm keeping my fingers crossed that they are ok!
And, I've already placed an order for bee packages, just in case I lose my hives. Order your bee packages, now!
View from my living room window-snow on my hives this afternoon!