Adeline penguins live on the Antarctic continent and on many small, surrounding coastal islands. They spend the winter offshore in the seas surrounding the Antarctic pack ice. Initially these birds feasted on a diet based only on fish, which now includes a major portion of krill. They have substituted easier-to-catch krill as a preferable high-energy food source.
A study suggests that with the Antarctic hunting of many whales and seals, there was a surplus of krill, tiny crustaceans indirectly influencing the food chain. Penguins have been apparently taking advantage of the surplus. This means a huge ecological dietary response by the penguins in relation to some changes in their environment. This adaptability might in fact help them as Antarctic melts with global warming.
Emslie and colleague William Patterson of the University of Saskatchewan, Canada, based the finding on analysis of more than 220 fossil eggshell fragments ranging from the past 100 to 38,000 years. The proportions of certain forms of carbon and nitrogen in the eggshells tell the researchers what type of food the penguins ate in the days before laying their eggs.
While over fishing poses a threat of fish as a meal, Krill populations are dwindling, where warming temperatures mean less sea ice. Sea ice holds algae that the krill feed on when it melts. Krill is also being depleted by being used as feed in fishing farms.
Source: National Geographic