I started the winter with 40 colonies, and now I have 27.
I feel a deep grief. My bees died because there were gaps between the boxes, letting in the cold winter air. They died because heavy, wet air settled in the hive, making the cold all the worse, and the bees couldn't get the moisture out. In other hives they died because their entrances were too open, too indefensible, and robbers from other hives came and stole their food. They died because I split five of them in Autumn, to double their numbers... but in all my splits, either the new hives died, or the parent hives died, or both died.
In one hive that I opened the queen came to the top of the hive. She was all alone. All her children were dead at the bottom of the hive. Her hive boxes had some gaps between them, the front entrance wasn't defensible enough, and the floor was poorly ventilated. I'm not sure she appreciated my effort - my effort killed her, as surely as if I'd just sprayed Raid into the wall cavity I extracted her original hive from. My new hive boxes will not have the defects that killed her, though - so perhaps the bees that survive next winter as a direct result of what I learned this winter will suffice.
I'm making my boxes to a higher standard this year, partly because I want them to look better, but now also because I want my bees to live. They'll have dovetailed sides. The floors will be vented, and the entrances will either have reducers to winter, or just be smaller in general. My top bar hives each have only one 25mm diameter drilled hole for entrances, and they're huge colonies, so I'm probably going to go in that direction.