For birds, cleanliness is not optional. They rely on their feathers for flight and insulation, and only replace those feathers once or twice each year. In between molts, they need to keep their feathers as whole as possible.
Feathers, like our hair, are made of protein; and like all organic things, they degrade over time. Sunlight hastens this degradation, but certain aspects of the feathers themselves can slow it: dark feathers colored with melanin last longer in sunlight, for example. Of more concern, though, are the many creepy-crawly things that like to eat protein, and will happily hang out in a bird’s feathers, munching and laying eggs.
To combat these parasites, birds coat their feathers in protective oil from the preen gland located at the base of their tail, and they bathe.
But they have to be careful. Small wild birds are lunch for everything from feral cats to Cooper’s Hawks, and no bird wants one of these sneaking up on it while it is obliviously scrubbing behind its ears. So they bathe in bursts, a plunge into the water followed by a quick look around.
Or they soak and shake their back ends while holding their heads still, vigilant.
The exuberance of this style of bathing—you have to get everything wet really really fast—sends water flying everywhere.
Sometimes you have to dunk your head, but that doesn’t mean you shouldn’t have your eyes open.
Even an oversized part-domestic part-Mallard duck, too big to have to worry about most predators, keeps his eyes open.
One thing I love about photographing bathing birds is that it brings home just how fast they are. My shutter speed will freeze water droplets in midair, but the bird will still be blurry.
The skill of bathing while remaining vigilant may be one that the birds have to practice. Unlike the adult juncos I’ve seen bathe, a juvenile junco I watched seemed to only know how to wade in the water. He didn’t splash.
This might explain why most of the juncos we saw with feather mites were juveniles: poor bathing habits in the young ‘uns.
After washing, it’s time to smooth all your feathers down and re-coat them with oil from the preen gland. While doing this, keep a look-out. Predators are still out there.
The only acceptable reason to close your eyes while bathing is to quickly scratch an itch.
I am glad that humans get to bathe without worrying about being attacked—those of us who haven’t recently watched the shower scene from Psycho, anyway—but birds’ frenetic bathing style does look kind of fun.