The team examined other possible threats to the penguins’ precarious existence on their remote island. Birds here nest in the shadow of an active volcano – Mount Curry, also aptly known as Mount Asphyxsia.
Sites downwind of the volcano have been given names including Stench Point, Noxious Bluff and Asphyxia Plain, because of the smell of fumes emitted from the crater.
Dr Ratcliffe told BBC News: “When you add all the penguin guano on top of that, and you really do have one of the smelliest places in the world.
“It’s like a penguin Mordor.”
Mount Curry’s last major eruption was back in 2016, but the penguin declines that this study analysed have been steady and ongoing since 2011, suggesting that something else was happening.
Another concern was competition for the krill that chinstrap penguins rely on – possibly from migrating humpback whales. But, while the humpbacks eat huge quantities of krill, they also help boost krill production by fertilising marine plants that the krill feed on (with their huge quantities of whale poo).
Researchers say a more fundamental, climate-driven shift in ocean food supplies is to blame.