While subbing at Santa Rosa GINS on Saturday, I was surprised to see the beginning of a collapse at SR7211. It's about a week early. In fact, there were nests which had been laid a week earlier than this one that had not hatched, but this has been an unusual year.
Under drier condtions, you will usually see a soft bowl-like depression in the sand. When we've had long periods of rain like this summer or when a nest has been washed over during a storm surge, the surface may become compacted and crusty, resulting in a collapse with defined edges such as you see above.
An interesting aside about the photo above. Look closely and you will see there are actually three small holes atop the collapsed area. One of them is obvious, but there are two more above it on the upper edge of the collapse. They are not air holes. This is where a mouse was sitting! Sometimes you will see three pad/paw prints and others you will see all four. It was probably the Santa Rosa mouse which lives in the dunes. Yes, we have our own little beach mouse, but unlike Perdido Key, ours are not endangered. The photo below with multiple mouse tracks was taken at another nest earlier in the year.