I suppose your all knew this. I didn't.
I've been wondering why house sparrows love the sandier part of my property. They dig and then roll in it. Trying to get an answer took my own digging lol but after I accompanied my question with the specific type of bird I learned:
"House sparrows – are champions of dust baths.
House sparrows prefer very fine dust and will flap up a storm when they find a patch of it. They dig a hollow with their feet, push their bellies into the dust and toss it under their wings and over their backs as if it was water. Their goal is to get the dust into their feathers and all the way down to their skin. When they’re suitably coated they shake off the dust and preen it away until their feathers are in good condition again.
Why go to this trouble? Dust smothers skin and feather parasites and absorbs excess oil that’s removed as the dust is preened away."
I keep filling in the shallow holes and they make new ones.