Be careful not to give moldy food to birds, however, as it may cause illness or death. To prevent the spread of some avian diseased, food should not be spread on the ground, and feeders should be cleaned and disinfected regularly. In winter, when the ground is covered by snow, suitable grit may be hard to find. You can supply grit to birds at the feeder in the form of crushed eggshells, coarse sand, or from boxes of grit that are sold at variety and pet stores. Water in a bird bath or other container often attracts birds in spring and summer, but the costs of maintaining open water through the winter are not justified.
Birds survive on water derived from foods they eat and from eating snow.
Seed-eating birds, like crossbills, are sometimes attracted by salt and other minerals that can be supplied by a salt block. Their need for shelter and protection from predators is often stronger than their attraction to an artificial food sources. Also, because birds will not normally visit your yard in search of natural food if there are no trees or shrubs, they would be unlikely to detect food in your feeder. Start planning to landscape your yard for birds. A brush pile also can provide cover for some birds.