If you'd like to give your concrete bird bath some extra protection from the elements, you should consider sealing it. Not only is sealing a bird bath easy, but it can go a long way in extending the bath's life.
Step 1 - Clean Your Concrete Bird Bath
Before you can seal your bird bath, you'll need to give it a thorough cleaning. Begin this step by combining warm water with a mild brand of liquid soap inside of an empty spray bottle. Next, seal the bottle and shake it until your cleaning solution takes form. You will now need to apply your newly formed cleaning solution to your bird bath and proceed to clean off any caked-on dirt or grime with the aid of a hard bristled scrub brush. Once the bath has been properly cleaned, use a garden hose to rinse off any lingering traces of your cleaning solution, then give your bird bath ample time to dry.
Step 2 - Apply Your Sealer
After your concrete bird bath has fully dried, you'll be ready to apply your sealer. Begin this process by laying your bird bath on top of a small tarp or an expendable towel. Next, use a paint brush to apply your sealer in broad, even strokes. When performing this step, take care to apply at least two coats of sealer to every part of the bath. Once you've applied the proper amount of sealer, allow the sealer to dry for 2 to 3 days, then fill it up with fresh water.
Also, when selecting a suitable sealer for your bird bath, make a point of selecting a non-toxic brand, as the alternative has been known to cause health problems in birds.