This is a phenomenon that seems to be more prevalent on hot, humid days, though I haven’t actually done charts or anything. I’ve often noticed small birds (which I’ve tentatively identified as sparrows) happily cheeping and wriggling around in the dust as though it were a lovely cool birdbath. It’s not just one or two sparrows deluded by Washington humidity, either.
So why are they doing this? For some reason, I’m quite perturbed by their behavior.
Dust bathing keeps their feathers in shape and protects against parasites. I don’t know how, unfortunately.
From Bird’s Eye View: A Practical Compendium for Bird Lovers by Dr. David Bird:
Other sites mention that the dust can also absorb excess oil in the feathers. Also, Dr. Bird’s name raises the question of whether his career was predestined, or did he change his name? Inquiring minds etc.
I’ve also seen birds doing this and always assumed it was a defence against skin parasites.
Another wierd thing some birds do is anting, in which they either pick ants up and apply them to their feathers, or allow the ants to crawl all over them squirting out formic acid. It’s often assumed that this is also anti-parasite behaviour, but nobody seems to know for sure.
IANABE, but my personal opinion is that this only happens with males at mating time and that they are actually masturbating.
