Bees survive the winter by having a massive group hug. I get asked the question, “Do they hibernate?” No, they don't hibernate. What bees do when it gets cold is cluster together and form a tight ball. They form a CO2 bubble that they live in, which lowers their metabolism rate, and they are able to keep the temperature inside that cluster.
Before we have our shortest days, it doesn't matter what the outside temperature is; they will keep it at +20°C one bee depth into that cluster. Once we go past the shortest day and the light changes from the sun—so after December 21, when the days start to get longer—they raise that temperature to about 36°C and they keep it inside there.
In some of the comments that I've made is “critical mass population.” If bees do not have enough bees in that cluster, they cannot generate that heat. Imagine, if you will, we're a bunch of bees. If I were to stand by myself in the middle of the room, I would freeze and die, but if all of us were to get together in a group hug and stand there together, we'd have to take our jackets off, because we'd be pretty sweaty and hot. That's what happens inside the hive. If they don't have enough feed and if they don't have enough of a population inside the hive, they can't survive the winter. However, if they're healthy and they have that substantial population, they will.
Natural pollinators don't have that. If we were to rely on natural pollinators, we wouldn't get the pollination effect, simply because natural pollinators don't start pollinating until much later in the season. Because bees are a social insect, they can start here right now.
Right now at my farm, I have bees flying on all the poplar trees, making sure that there's going to be good cross-pollination for all the poplars that are out there. They're then going to go to the pussy willows, then they're going to the crocuses, then they're going to go to the dandelions and then they're going to go off to the clovers, the caraganas, the lilacs and to everything else. In the fall, the last thing they pollinate is pine trees.