There's nothing quite so gratifying as seeing January foragers with pollen baskets full!
"The point that every beekeeper needs to understand is that the real nutrition for the colony comes from pollen. Specifically, a mixture of various and appropriate plant pollens, gathered by foragers, and carried back to the hive in the specialized pollen baskets on their hind legs. Pollen is synonymous with “bee food”—it provides the protein, lipids (fats), vitamins, sterols, minerals, and micronutrients that bees need for growth and health. Honeybee colonies require pollen in a big way—to the tune of 30-100 lbs a year! The stimulus for pollen foraging is largely the presence of brood pheremones produced by young larvae—hence, beekeepers who see pollen loads coming in at the entrance generally assume that the colony is queenright with brood present."
Randy Oliver - www.scientificbeekeeping.com