Wintering Without a Top Entrance
In the last number of winters we have been successfully wintering our hives without top entrances. In the beekeeping world the idea, for many years, has been to use a top entrance to let the humidity out of the hive so that it doesn’t condense on top of the cluster and drip down on the bees bees, causing them to be chilled and die. However this has been proven to be counter intuitive to how the bees what to arrange there nests. In the wild bees will choose an entrance that is lower down rather then further up, if given a choice. Also beekeepers have often notices the bees closing any top entrance with propolis as much as possible in the fall in preparation for winter.
The top entrance has always been somewhat of a problem to solve. The beekeeper goes to great length to insulate the hive and when he is done he makes an hole on top where the heat will accumulate to let the cold air in! This has never made much sense.
So how can bees survive with all that humidity that needs to go somewhere in wintertime? There are a quit a few tricks that a bee colony can play to make it all work for them. It is not a simple one answer solution that they have. The beekeepers job in all of this is to firstly make sure that his hives are healthy and strong, low varroa levels etc. The top lid needs to be well insulated, whatever method is used is not as important as long the top of the hive can’t go below the dew point then no moisture well condense on top of the cluster. The heat from the cluster together with a well insulated top will prevent this.
What I have found is that the condensation will happen towards the outside frames of and the bottom board. The water will run out the front and often I find the entrance will almost completely freeze shut. I have not found an entrance that has frozen completely shut, rather there is always a hole somewhere that stays open.
One thing that took me completely by surprise the first few winters where I tried wintering without top entrances is that the hives start brooding up in winter much much earlier then I would have thought they would. With top entrances I found my hives started to brood up in the middle, or more often, towards the end of March. Now without a top entrance they start raising brood early February if not in January already! This can cause a problem if the cluster is not large enough to reach all the honey stores in the frames. I have had to start feeding the hives in the first week of February, otherwise I find quit a few strong healthy hives starved because they were not able to move to new stores because of the brood that they were raising.
Hive without top entrance in late winter.
Bees can not raise brood without water, lots of water. Also in order to use the honey stored in the frames the bees need to diluted it with water in order to uptake it through their proboscis. When wintering without a top entrance the bees now have a constant supply of fresh water which they can lick of the walls of the hives. A much more stable temperature can be maintained inside the hive. Water is a very important part of the bees ability to survive. In summer they can fly out and collect it but in winter they use the water that is in the hive already to survive. This water is carefully controlled by the bees through expiration and also through temperature control. In fact on theory is that bees will sometimes raise brood in winter simply to use up water that is accumulating inside the bees. Raising brood needs a lot of water and bees are able to use up a lot of water which they are forced to hold in their gut in winter because they can not take a cleansing flight. If a bee can not get rid of the water in its body it accumulated in the gut and when it reaches about a third of the body weight of the bee then it needs to be expelled from the body. When the bee can not expel the water then it shows up as dysentery in the hive. Since about 80% of the feces is water by getting rid of water through expiration or brood rearing the bee is able to go longer without have to take a cleansing flight in winter.
This video was taken in middle of a typical cold spell in Manitoba. This is what happens with the moisture coming out of the hive. The inside of the hive has very little moisture condensing in it. Most of it seems to condensing on the bottom board rather then on the sides. According to some of the research that I have read, in winter the hive will ventilate downwards which causes most of the moisture in the air to condense on the bottom board. Based on what I’m seeing this makes sense because most of the water I see in the hive is condensed on the bottom board.
Over wintered hive without top entrance.
When wintering without a top entrance the bees are a lot more active on top of the hive.