In 2016, ornithologist Steven Emslie was studying penguin colonies along the shores of Antarctica’s Ross Sea, when he heard about pebble mounds associated with guano deposits on Cape Irizar, a rocky outcrop surrounded by water and ice.

Guano forms as the corrosive poop of generations of nesting birds reacts with rocks and soil. But no active colonies have ever been recorded at the site, even by early Antarctic explorers spotting and naming the cape in 1901.

Visiting the site, Emslie came across of what seemed at first a fresh penguin carcass resting on older remains, including bones, feathers, and eggshell. Later sampling and carbon-dating put the carcass at a minimum of 800 to 1,100 years old, with some of the older remains found at the site dating back to 1,375-2,340 and 2,750- 5,145 years ago. The pebble mounds were nests, suggesting that the site was a former penguin colony.

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