Just to point out the value of the scientific method and using controls: 

I also tried overwintering colonies with no upper entrances. However, as a control, I had several hives with very large upper entrances (4 inches by 5/8 inch). The bulk of my hives had the traditional 1 inch by 5/8 inch top and bottom entrances. 

In spring, basically all the colonies survived. The ones with no upper entrance and the ones with the giant upper entrances were all very strong. My conclusion was there was no difference between different entrances in terms of survival and strength, provided nothing exceptional happens through the winter.  

My overall point is that if one wants to test whether a single entrance results in better winter survival or bee health than two entrances, one needs to use controls so there is something to compare it to. 

Without the control, no conclusions can be made, except maybe that a single entrance didn't kill colonies. 

Tracey

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