Sparrows digging holes

[Garye]

I was watching what I think were sparrows burrowing holes in some dirt. At first I thought they were trying to either make a nest or they were trying to hide from something, but then I got the idea that maybe they were taking a dirt bath. They all seemed to enjoy doing it and they would chase others away from a hole one of them had created. Then they would get in the hole and just wallow away in the dirt creating a deeper hole.

Can someone tell me just what they were doing this for? It looks like they were trying to take a dirt bath which to me sounds crazy because I think if they wanted a bath, they'd use water instead. Why would a bird prefer a dirt bath over a normal water bath or were these sparrows doing it for some other reason? Do they just do it to relieve themselves of itches, to keep themselves cool? It was really hot today and they were just wallowing away in those holes they had created. (The landscape people won't be too happy about their holes).