Ensure that you have a birdbath that can be left out year-round. Many metal birdbaths, such as decorative copper baths, are best stored indoors during the winter.
Plug in your birdbath if you have a self-heating model. Self-heating baths feature thermostats which will activate the heating function when the temperature dips.
Determine whether your birdbath can accommodate a de-icer, an electrical heating unit that is separate from the bath itself. Metal baths and ceramic baths could be damaged by de-icers; plastic baths usually work well.
Install a de-icer. De-icers can keep a birdbath unfrozen even if the temperature dips to 20 degrees F.
Check on your birdbath daily in the cold months to ensure that the heater is still functioning, and that ice has not formed.