Attached are two pics of circular clean spots in my gravel driveway. I have about seven of them. All that happens is the gravel is brushed away from the base material. Almost all are nearly round and I've seen them for a couple years and almost always in the fall.
These two areas in the driveway are maybe 30 ft apart.
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My first thought is a bird was doing this in order to get smaller grit to eat for their gullet that grinds up food. I don't know. We are also frequented by possums and coons and an occasional red fox. A couple housecats as well and a rabbit.
Anyone have a guess what these are or what is causing them?