A process known as dwindling sometimes occurs in the early springtime in weaker hives. Spring dwindling is the process whereby the number of bees in the colony is reduced to where the colony cannot sustain itself. The population continues to reduce until the colony completely dies. Dwindling occurs in the spring in a weaker hive because of one or more of the following factors:
Poor quantity or quality of winter stores of honey and pollen
Weak queen that does not over-winter well
Drafty, damp hive interior
Colony has been weakened by nosema, mites or insecticides
Excessive drifting has occurred before fall