The headlands and inlets of Westray are covered in spongy tufts of damp grass.
Beneath them lie normally invisible tunnels. They are made by Puffins, or made by Rabbits and then abandoned when the cliffs collapse and then colonised by Puffins.
Sometimes they collapse with the wet weather over winter. Sometimes they collapse because of the pressure of unknowing tourists’ feet. I’ve had to say “Sorry, but you’re standing on a Puffin’s burrow”, or “There’s a Puffling directly under your feet. Can you hear it?” several times.
I suspect this Puffin may have some more digging to do come next summer.