Do you have squirrels in the area? The divots look like where they dig and bury nuts and sunflowers/peanuts from wild-bird food people put out -- usually fall through warm, frost-free days of winter. They dig, bury, then firm down the loose soil with their paws. Sometimes you would see tiny pawprints.
As seasons change to late-winter and spring, they start the reverse process of digging up stuff. But they sometimes don't remember for sure where and dig multiple holes in one area.
I would say squirrels dig around 2 inch diameter holes.
If these holes are smaller than that, the culprit could be birds, too.
If it rained to wash/flatten down the mounds, these could be remains of nightcrawler hills where nightcrawlers had emerged and then went back down, making a little molehill like mounds of worm casting. If so, the "soil" in the divots should be richer than surrounding soil. In my area, they become active after the ground has thawed in spring. ...birds would try to hunt down the worms and enlarge/make deeper holes in the process.
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