Brown bee colonies with few overwintering workers rarely use up all their supplies. In the last period of willow flowering, however, colonies can have expanded their brood nest considerably. After this, a week of poor weather, rain, or severe cold can be problematic for the colonies. During such periods without flying activity, emergency feeding might help the colonies survive and keep their brood alive. In general, the colonies should have two frames, or about five kilograms of food, at the beginning of spring. The reason for this is that the feeding of brood and the flying to willow flowers for pollen int he early spring uses up a lot of energy. During the end of flowering, the food supplies are used up, and the cells are filled with either brood or pollen. the brood area will be blocked by honey.