One of my hives died this winter. It was my strongest hive going into the winter, so I was very sad and also pretty surprised.
Here is a very bad pic of the dead bees in the bottom of the hive when I opened it up. That's a lot of dead bees.
To find out what caused it, I opened the hives and I examined the frames.
You can see the cluster in this pic. All of the bees in the circle are dead. The cluster was just a bit bigger than a softball. It extended three frames wide. That's pretty small to get through the winter and keep everybody warm and fed.
Blow it up to see all the bee butts sticking out of the cells. This is a sure sign of starvation.
The problem is that there was a lot of honey still in the hive. A lot. They shouldn't have starved.
Notice the rough spots at the tops of the open cells near the capped cells. Those are chew marks from the bees opening the stores. This is right next to where the cluster is, so I have to wonder why they starved. They were so close!
Could be they were too sick or too cold because the temps here vary so greatly and the cluster was too small.
One of the things a beekeeper must ask is whether the mite load was heavy and caused too much stress on the bees during our wild and crazy winter, thus weakening the hive and causing the deadout.
To check the mite load, I pulled the bottom board out from under where the cluster was [and all those dead bees]. The bottom board closes things up way down under the bottom screen of the hive. The screen keeps the bees in, but allows for good ventilation - essential here where it's so humid. The bottom board slides in under the screen and helps close things up to keep them warm for the winter.
When I pulled the bottom board I found a lot of tiny wax pieces. Those are the wax cappings that they've chewed off to get to their stores.
With a magnifying glass I counted mites. The dark oval in the pic is a varroa mite. That's a bee leg next to it. The mite is tiny - the size of a chigger. But on a bee, it's big. To a bee, one of these is the equivalent of a mite the size of your fist on you. Eew.
I counted only 5 mites. Not bad at all.
All bees in this part of the country have mites, just like all forests in this part of the country have ticks. It's a fact of life. There are things you can do if they get bad, but generally you encourage good hygiene and small cell size and the bees manage.
I showed these pics to the experts at Beemaster and they agreed that the cluster died because it was too small. There's no way to determine why the cluster was too small - could have been the robbing in the fall, and the robbing might have resulted in them going queenless. The bees had dysentery, but folks seem to think that it wasn't bad enough to kill the cluster, just further weaken it.
If I had been on the ball and known what I was looking at in January, I would have recognized the small cluster size right away and then reduced the inside space of the hive with a follower board, which would have been less space for them to heat. That might have given them a chance.
Also, from now on I'll be checking the hives in late November to see what the cluster size is so that I can reduce the hive size earlier if need be. In the horizontal hives, you can see the cluster size easily when you lift the lid and you can see right where the cluster is. All you have to do is put a follower board where you want it to close up [narrow up] the hive space inside.
Next year, we're going to set the hives right next to each other with just enough space for insulation board between them. That'll help keep things warmer, too.
The last question is what to do with the dead hive full of honey. I asked the folks at Beemaster and they suggested just leaving it for the other hive to clean out for me. The day I opened it up for these pics, the other hive was pretty busy checking things out. If you blow up the pic you might be able to see the hundreds of bees on this hive trying to harvest it.