In 3 areas of one apiary, bees on three sides of the orchard, the following hives were lost. 3 of 7, 4 of 8, and 1 of 7. These are not big numbers to draw conclusions but in percentages they are. No hives were treated with medication, all were strong. Had a bad winter with extreme cold.
Now my question-Did I kill my hives with being to good of a painter/builder? In my mind I did a great job in making the hives airtight, with only a bottom entrance. Hives are elevated and no blockage from snow. I never had a problem before with moisture but previous years were more milder. No mite kill evidence so I'm thinking moisture. Does anyone have good info concerning this. I read about open bottom etc. and have always thought the more I protected the bees from winter the better but I guess thats not the case.
The better site (1 of 7) is more open and condusive to wind and sun. Does anyone think that perhaps location/moisture is a big contributor of other problems such as winterkill, mites, etc. Anyone...
I don't think you want an airtight hive, but neither do I think an open bottom is good in a norther climate. I think you need some ventilation through the hive in winter, but only a small amount and only a controlled amount. In other words, there shouldn't be a lot of difference in the air flow when it's calm outside or when the wind is blowing. A draft from the wind is not good. The inner cover is designed to provide some ventilation. I put a couple of more holes in it, cover them with screen and a box on top of that with some holes and screen over those holes. That way you have the heat of the hive creating a steady, but slow draft up through the hive from convection, but not a blowing draft from the wind. Some people prop up the inner cover with something to provide more ventialtion around the sides. I haven't tried this.
I know of people who have lost bees with the bottom open and they thought it was from the cold. I have heard of others who overwintered with an open screened bottom board and did well. The end result is, it's hard to say what the cause of loses are sometimes.
Does it appear that they have cold starved?
The cluster requires breaks in the cold temperatures during winter to move and adjust food stores.
This winter did not provide much in the way of breaks in the cold temperatures.
The hives that were more exposed to the sun, may have gained enough warmth on some of the sunny days to be able break cluster and get at food stores.
As for moisture, it can cause the cluster extra stress and make keeping the cluster warm more difficult.
What I have done and it has work well is, I made up "feeder boxes" from 1" rough cut pine boards. I set the hives up for winter in (3) deep hive bodies and then put one of the pine boxes on, then the inner cover, then the outer cover. I do wrap the hives in black felt paper also.
The extra pine "feeder box" allows me to inspect and feed when required over the winter. The pine box is not painted or sealed so it helps with moisture / condensation within the hive.
Common practice here in NH is to use screened reducers on the bottom opening (to keep out mice mostly) which are kept clear of snow, and on the front face of the upper hive body, drill a 3/4" hole. This gives a limited but valuable updraft to help the bees expel excess moisture.