Why does my big chicks do this?

[Minah]

I can't explain but why does my big chicks crowd out in the corner and digging in the sand? You can see it in the video below

 

[sourland]

Because chickens like to dust bathe?

 

[Aapomp831]

They’re bathing lol... is this your first time owning chickens? This is a very common and necessary behavior; they are smothering parasites and while getting “clean.”