Penguin species in the Antarctic that once benefited from rising temperatures are now in decline due to warming gone too far, scientists said Thursday. 
Previous scientific research was unable to determine why populations of Adelie and chinstrap penguins are in decline, while gentoo penguins are increasing in numbers.
In the new study, biologists said that all three species expanded after the last Ice Age ended around 11,000 years ago, but rising temperatures being seen today are threatening their food supply.  
"There was less ice around Antarctica, which was good for these penguins, as it opened up new breeding habitats," Gemma Clucas of the University of Southampton's Ocean and Earth Sciences department told AFP.
"However, what we're seeing now is that climate change is resulting in even less ice, and this is now bad for Adelies and chinstraps because they no longer have enough food."
Adelie and chinstrap penguins eat mainly krill, small shrimp-like animals, which in turn feed on algae under the declining ice.
Gentoos, on the other hand, have a more varied diet, which includes fish and squid less affected by warmer seas.
"What we are seeing is a 'reversal of fortunes' where increased warming is no longer good for two out of the three species of Antarctic Peninsula penguins," added co-author Michael Polito from the Woods Hole Oceanographic Institution.
"This research shows quite clearly how a single environmental change, in this case warming, can have different consequences over time."
The study was published in the Nature journal Scientific Reports.