It's just as important (if not more so) to have a water source in the winter. The location of some of our baths made it impossible to add a heater; additionally, they often get completely buried in the snow. We tried to keep the smaller saucers filled but in really cold, snowy weather they freeze very quickly. We solved this problem by adding a heated pet dish.
Moving water will attract even more birds. We have added a birdbath dripper to the front yard. The larger birds take advantage of this bath. Until the plants get larger I think the smaller birds will not feel safe enough to use it.
Ponds are a super addition to the habitat. We do not have one but I am still considering the possibility. I am unsure of my skills in taking care of a pond so I will do some more research. There are lots of great sites on the web that can provide information on building and maintaining ponds.
