Already have a winter proof birdbath? Winter proof Cement or poly-resin?
The the Bird Bath de-icer may be all that you need. 200 Watts, 120Volts. Ice free water all winter. Built-in thermostat. Stainless steel guard and auto shut-off. 1 Yr. warranty. Fits all types of bird baths.
Read more about heated birdbaths here.
It is not recommended to use glass or ceramic birdbaths through cold weather. They are prone to break and not likely to survive the winter.