There are three holes all the same, within a foot of each other. I hope the photos make that clear. I have no idea what it's about. They just appeared one morning. I tried sticking my finger in one to see how deep it was and I couldn't touch a bottom. I've watched to see if there are bees coming in and out but no sign of any. And the only thing I could think of, because it's such a small hole, is a chipmunk? But I haven't seen a chipmunk all season.

This hole is between two pavers.

This one is a 8-12" away from the first one...which is to the left of this photo. You can see from my shoe how large the hole is and the other is about the same. I think there might a third hole about 10" to the right of this 2nd hole. I tried filling them up the first time I saw them, but the next day they were open again.