Winter is the most common time of the year for beekeepers to lose a colony. The below document addresses Fall Management, Preparing for Winter and How to Be A Good Beekeeper in January.
Why Did My Bees Die?
Beginning on page 14 of the “Wintering Bees In Cold Climates” document is a process to identify the reason the colony was lost so that the beekeeper can take corrective action to protect other colonies and increase survival rates in subsequent years.
Rockwood Park Backyard Beekeepers 