As sea ice in Antarctica melts, it causes disruption in the food chain that chinstrap penguins on the South Shetland Islands depend on, the researchers said.
Chinstraps penguins' main food, shrimplike creatures called krill, depend on algae that attaches to that ice, they said.
"Actually, in the '90s it was thought that the climate change would favor the chinstrap penguin, because this species prefers sea waters without ice, unlike the Adelie penguin, which prefers the ice pack," researcher Andres Barbosa of the National Museum of Natural Sciences in Madrid told LiveScience.com.
Chinstraps, named for the thin black line running from cheek to cheek under their faces, seemed to increase in numbers at the time, he said.
But the decline in winter sea ice is now affecting krill populations, Barbosa said.
Research on the breeding colony on Deception Island in the South Shetlands showed occupied nests had declined by 36 percent between 1991 and 2008, he said.
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