It is interesting to understand why a source of cool water is so important to birds. David Allen Sibley, author of The Sibley Guide to Bird Life & Behavior provides an excellent explanation: "Although birds lack sweat glands, they can perspire through their skin and thus reduce body heat. Birds can also get rid of excess body heat by panting, which allows water to evaporate from the surface of the air sacs." Continuing, Sibley explains: "The challenge is both of the above cooling methods are dependent upon a ready source of cool water".
While having a fancy birdbath may be appealing to us, it is not necessary for the birds. Something as simple as a clay saucer or upturned garbage can lid kept refreshed often with clean, cool water will provide an extra water source during extreme heat as many areas are experiencing now. However, one thing we know is that moving water attracts 10 times more birds. There are products that can address this need. A simple way I've used is to hang a plastic pot for plants above my bird bath. Before filling with water make a very tiny hole in the bottom so the water can slowly drip into the bath. Good advice is to start with a really tiny hole as you can always enlarge it if you need more water to drip. Using this type of container (milk jug or bucket) is a quick way to provide moving water, but you do need to refill the container, as necessary.
If refilling the container might prove inconvenient, products like the Water Wiggler can be put in your bird bath. The Water Wiggler runs on batteries that make its legs jiggle keeping the bird bath water constantly moving. The Water Wiggler I use runs on 2 D-cell batteries which keep the Wiggler moving 24-hours a day for 3 months. Actually, I went a step farther and purchased the Water Wiggler Aurora which provides a gradually changing rainbow of colors casting a soft glow on my deck at night. The colored light turns on automatically at dusk and glows for 3 hours and then shuts off automatically. However, only the light shuts off as the Water Wiggler provides continuous water movement as mentioned.
Please don't forget to provide water for all our feather friends as they truly need and appreciate it. They'll fill your backyard with brilliant color, intriguing behavior and beautiful song as a thank you.