Water is a very good way to bring birds to your yard in the winter. Open water for drinking can be hard for birds to find, and it's as important as food. You can buy heated bird baths, or buy a heater for the bird bath you have. Keep the water fresh and clean. Here's a photo of the one we use, simple and effective. The wooden frame surrounds a shallow metal pan that is electrically heated from below. We plug it into an outlet on our deck. That' a piece of brick in the middle, perhaps making access to the water easier.