While researching overwintering to get other opinions in preparation for my upcoming talk at the Ohio State Beekeepers Association Summer Conference I discovered Michael Bush’s page on overwintering. I’ve written before on the advantages of switching to all medium but never considered overwintering as a reason to switch to medium brood boxes.
I have not had the opportunity to run medium and deep hives side by side for a few winters to compare their overwintering success, and since I’ve switched to all medium hives I refuse to put any deeps into operation. So I must take Michael Bush’s observation that medium hives tend to overwinter better than deep hives. The logic makes sense however. Bees in deep hives have less freedom to move around in the cluster as the cluster is broken up by the frames more effectively than with medium frames. This, I suppose, is why deep frames often have ‘communication holes’, typically located near the bottom corners of the frame (Unfortunately this location makes them of very little value to a cluster that would typically be located more towards the center of the frame. It would make more sense to me to put these ‘communication holes’ in the center of the frame.)
So I can’t say for certain that medium hive bodies overwinter better, but I generally do have fewer losses than the average for my area. Of course I do many other things in preparation for overwintering (usually) that likely have larger effects.