Once the top fills with water/snow & freezes, the top may crack. All birdbath/fountain bases, bench legs & statuary should be raised up off the ground in winter so they will not freeze to the ground surface. Ideally, a fountain should be stored indoors in the winter away from the elements. However, if a fountain bowl must be left outside, remove all pumps, rubber stoppers, drain pipes, finials & small components, & cover the top with burlap or any absorbent material (old blanket/towel) & then wrapped with dark plastic, making sure that water does not accumulate in the basin & freeze. Fountain pumps, finials, & other small components should be stored indoors. Check the fountain periodically to insure that the cover is secure & water is not accumulating in any fountain component.