About 7000 years ago, gentoo penguins came to Ardley Island in the South Shetlands chain just off the Antarctic Peninsula.

The island is a little over 1.6km long, almost small enough for a classic castaway cartoon, except that it is the Antarctic. And instead of a lone palm tree, there are now about 5000 breeding pairs of gentoo penguins, one of the largest colonies in the Antarctic, and a lot of guano (penguin excrement), much of which is washed into the freshwater Ardley Lake, where it accumulates in the sediment.

Examination of penguin excrement has helped scientists trace the rise and fall of gentoo penguins. Credit:David Merron Photography

In that guano, scientists have found the record of a recurring natural historical drama. Three times since the gentoos arrived on Ardley, the colony was devastated by volcanic eruptions. The ash and smoke killed them or drove them away. Penguins gather in colonies to breed, so there may well have been chicks caught in the ash fall even if adults escaped. The landscape the eruptions left cannot have been hospitable, because each time it took 400 to 800 years for a colony of similar size to re-emerge.

That is the story, reported in Nature Communications, that Stephen J Roberts of the British Antarctic Survey, Patrick Monien of Bremen University in Germany and other scientists from Poland, Scotland and England teased out of lake sediments that show, in the rise and fall of guano concentration, the rise and fall of the penguin colony.