It is a great achievement to have birds eating from feeders the year around in a backyard, but if there is no water area, a great many birds that do not eat feeder food will be missed.
April is a very good time to consider installing a bird bath to attract the insect-eating summer residents of backyards. Beautiful and spectacular birds such as warblers, tanagers, thrushes, and thrashers will drink and bathe in a water area, but will not eat seeds from a feeder.
There are many options for providing water for birds. The simplest, least expensive and easiest to maintain is the simple dish on a pedestal. It holds still water that needs to be refreshed and cleaned often, particularly during hot weather.
A better bird bath is one that has moving water that birds can hear from some distance. Migratory birds that are passing through a yard will hear the water and will stop for a drink and a dip before moving on.
Moving-water bird baths are commonly operated by a small submersible pump that moves the water to an upper level, where it then flows to the lower levels. Sprays and fountains are also effective ways to move water in a bird bath. Hummingbirds will often fly through a spray to wet their feathers, rather than bathe like most other birds. Nevertheless, all bird baths should have shallow areas, no deeper than a couple of inches, to allow birds to wade in for a bath.
-- George H. Harrison