I was amazed and delighted to see these "sparrow baths" made by a group of House Sparrows returning to the same spot everyday to bathe in the dust. Inside the dust was very fine, sifted by feathers. Outside the ground was hard and crusted over. It must have taken some time to form these lovely bowls.
Unfortunately, the Sparrows left the baths upon the car's approach - which is why I noticed them in the first place. Had I more time I would have staked it out to get a bathing shot, but I had to leave and only managed this image which at least provides a sense of scale.