Mason bees hibernate during the winter. Wasps die off, leaving only their queens to begin again in spring. Honey bees, however, are busy all year long.
(This photo of a pollen-dusted bee with her full pollen sacs is from September.)
With enough honey and pollen stores, hard work, and luck, a colony will survive the winter.
Full frames of pollen provide protein so the larvae can develop. I love the full palate of pollen colors from the various blooms.
Honey provides energy to the workers and queen. The workers will keep the queen fed, keep the hive clean, keep the hive warm, and forage on warmer winter days. They warm the hive by vibrating their abdomens or wing muscles while clustering around the queen and her brood.
Fall thieves try to steal the hives' resources. In my yard, yellow jackets are the primary predators. My bees are at their most aggressive in late summer and early fall as they fight off the bandits.
Their beekeeper host also attacks the wasps (My current record is 22 yellow jacket kills in 30 minutes!). The entrance to the hives is reduced in winter to keep out the wind and so the bees have a smaller space to defend.
Even more dangerous, Varroa mites weaken the bees and leave them susceptible to other diseases. I lost my colonies to Varroa last winter and colony collapses around the country are linked to these parasites.
This year, I put my bees through a sugar roll (http://bees.msu.edu/2010/varroacheck/) to measure the number of mites in the colony and then treated them with Thymol to reduce the infestation. The sugared bees were quickly cleaned off by their sisters when I returned them to the hive.
My two hives have plenty of honey, lots of pollen, good-laying queens, and hard workers. It's cloudy and 50 degrees today and the bees are out collecting what pollen they can find. Fingers and toes crossed that their hard work and my well-wishes will see them through to spring!