Usually when we think of “water birds”, ducks and geese come to mind. But if you have a backyard bird bath, you might have noticed that Robins are the most enthusiastic bathers of all the birds that use the bird bath. The robins in my backyard monopolize the bird bath, and really deserve to be called “water birds”.
Birds really do love bird baths, or even just shallow depressions that collect water along the side of a road, and most will get thoroughly wet at least once every couple of days. But what does getting wet really accomplish? Is it to rid themselves of skin parasites, or to cool off, or just to rinse the dirt off?
We know that birds spread oil from a gland at the base of the top of the tail onto their feathers while preening — this effectively waterproofs them, causing water to bead up on the surface. But too much waterproofing oil on the feather surface isn’t a good thing either, because it attracts dirt and dust, and eventually clumps making feathers less pliable and less effective airfoils. Hence, a good bath is needed to get those feathers back into shape.
Wetting the feathers makes them more pliable, so that when birds preen themselves, they can more easily readjust the feathers to form the most efficient flying surface. And there is proof that this works: a study in 2009* demonstrated that Starlings prohibited from bathing were clumsier flyers (had more trouble avoiding obstacles in their path) than those that had access to bird baths regularly. Clumsy flying compromises predator avoidance, so bathing does seem to be linked to survival.
But I still don’t know why Robins seem to love the bird bath so much more than other birds…do you?