I also think it is a dusting bowl.

Now I msut ask - any turkey tracks in the center or around the edges?

Any straight lines in the dirt as it a beak was dragged through th dirt?

How they dust or at least what I have witnessed this year several times.

The turkey finds a dry spot and lays down it it. With her beak she pecks and drags it from out front to her body and moves around in a circle. Then she scoops the loose soil/sand with her wings while movng her feet. The soil is them tossed over the top of her body. She gets up and then shakes off the excess and repeats the process. The birds I saw did throw up quite a dust cloud and the one hen dusted for over 20 minutes. When done the hen preened and then vanished into the country side.

Now at times these dust bowls get used regularly and sometimes not.

JW