Populations of a picky species of Antarctic penguin have plummeted as a less-fussy species has prospered, showing that even closely related species respond differently to the effects of climate change.

Chinstrap (Pygoscelis antarctica) and gentoo (Pygoscelis papua) penguins share a habitat and a taste for Antarctic krill (Euphausia superba), small shrimp-like creatures that were once abundant. But over the past 40 years, warming waters and decreasing sea ice have made krill scarcer. During the same time period, chinstrap penguin populations have also tumbled, whereas gentoo penguins have experienced a more than sixfold increase in numbers.

Michael Polito at Louisiana State University in Baton Rouge and his colleagues analysed the chemistry of penguin feathers from museums for clues to the birds’ diets. The team found that, in recent decades, gentoo penguins have shifted from depending almost exclusively on krill to a more diverse diet that includes fish and squid. But the researchers detected no change in the chinstraps’ diet, indicating that specialist species such as the chinstrap are much more vulnerable to environmental change.