for National Geographic News
Populations of the large birds on Possession Island in the Indian Ocean's Crozet Archipelago are declining as sea temperatures warm and the birds are forced to travel longer distances to find food.
Researchers tagged a king penguin colony and monitored it over nine years while also measuring sea-surface temperatures.
"We wanted to see what effect climate change was having on the breeding and survival of the penguins," said lead study author Yvon Le Maho, research director at the National Center for Scientific Research in Strasbourg, France.
The study appears today in the journal Proceedings of the National Academy of Sciences.
Tough Being On Top
Because king penguins are at the top of the food chain, they are particularly vulnerable to environmental changes.
Even a small shift in the numbers of fish and squid that the penguins eat could have large impacts on their population.
In recent years, many of the prey species have died or migrated as the ocean warms and the algae that those animals eat are impacted.
Warming temperatures also force fish to swim into cool waters farther away from the island, causing penguins to travel greater distances to hunt. The longer time away from home reduces chick feedings, the researchers found.
So during years when seas become warmer, penguins do not breed as successfully, Le Maho and colleagues found.
At the edge of the sea ice, where penguin adults forage during winter, just a 0.47 degree Fahrenheit (0.26 degree Celsius) increase resulted in a 9 percent decrease in the population two years later.
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