Hollows on the hillside

I was out looking for rock piles on what turned out to be a big sandy hill in Natick. Saw some nice graffiti on a water tower at the top but few rocks of any kind. I did notice, in a couple of places, hollows dug into the sandy soil. Finally, after seeing just one more of them, I decided these might be worth mentioning. I do not know if Anglos would dig isolated holes like this on the hillside. Indians did, to store grain.