In Montana, we did a two-year, monthly inspection and sampling project over in the Helena valley, brutal cold. We observed that colonies with large bee populations often failed to move from the bottom box to the top box, essentially starving with a full super of honey above them. We were conducting mite trials. Those colonies with the heaviest mite loads died first, and they failed to move upwards as they consumed honey. That didn't happen in the controls and colonies with the lowest mite loads.
Since then, I've found reports of varroa mites affecting how the cluster moves in winter in cold climates.
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