Looks like the winter was just too long, cold, and sunless. They had enough food to sustain them over winter but apparently too few days warm enough for them to get out for their necessary brief cleansing flights. The insides of the hives were all plastered with bee poop and even the "insulated" hives we experimented with didn't seem to provide the needed protection for the bees from the extremely cold, sunless days.
Wintering bees has always been the biggest hurdle for beekeepers to overcome in our locale. And obviously, once more, it's proved to be a big problem again this year. The Chief Beekeeper is too stubborn to give up though. He feels there must be a way. He just needs to keep experimenting and trying different things until he figures it out.
We'll be doing a lot of rebuilding of our bee population this spring and summer. Checking with the rest of our bee keeping friends in the county will perhaps give us a clue as to how we could have done something differently. We're hoping they had better luck than we did this winter.