My wife and I maintain three birdbaths for the benefit our backyard bird neighbors. As you might expect, many factors such as season and weather influence when and how often birds use these manmade structures.
Although birds bathe in the winter, they often limit their bathing during frigid weather. On the other side of the coin, many species seem to increase their visits to birdbaths during hot weather.
A number of years ago, I happened across several wood thrushes bathing in a puddle that had formed in a country road during a sudden summer thunderstorm. To this day, I still wonder why these beautiful songsters chose to bathe immediately after the passing of the storm.
In addition, birds also seem to be influenced by the presence or absence of other birds. My personal observations suggest that some species seem to prefer to bathe alone, while others do not mind sharing a bath with other species. For example, when a mockingbird or blue jay flies in to take a bath, other species that are already bathing immediately scatter. It is obvious that they do not wish to bathe at the same as these larger, more intimidating birds. More often than not bathing chipping sparrows will leave when eastern bluebirds arrive. However, I have seen chipping sparrows bathe alongside house finches.
By the same token, birds of the same species often have no problem bathing with others. Northern cardinals often bathe together as do eastern bluebirds.
Birds can be seen bathing throughout the entire day. Some birds seemingly bathe immediately after leaving their nighttime roosts. By the same token, others appear to bathe just before flying up to roost for the night. In between, most birds are not hesitant to take a bath any time during day.
For some reason, I long harbored the notion birds bathed but once a day. I have no idea why I felt that way. However, studies involving color-marked birds have revealed that some species such as the tufted titmouse sometimes bathes as many as five times a day.
As you can see, we have much to learn about bird bathing. In an effort to quench my personal interest in this behavior, I have begun recording information regarding incidences of birds bathing in my yard. I guess that is the biologist coming out in me.