My observation hive (a 5 frame nuc) died out through starvation. A couple of weeks ago the bees from this hive were out and flying, but I looked yesterday and ominously saw a few dead bodies out of the front. When I looked inside I found the hive had died.
It showed classic signs starvation; bees with their heads in cells and no stores at all. Back in the fall I tried to feed the hive, but I guess the bees just weren't able to put away enough stores in the five frames. There were a lot more bees in the hive than I was expecting to find, especially as it was a 5 frame nuc box and I suppose they just ran out of supplies. If truth be told I wasn't really expecting this one to make it. If it did that would have been a bonus.
I haven't looked inside my other hives to check on them yet, but I do know they had more stores available going into the winter. And I did hear some buzzing from one. I will nevertheless prepare some "mush" for a possible feed later in the week!