How do researchers non-invasively reconstruct the recent diet of Adélie penguins?

Answer

By collecting and washing droppings to isolate fish otoliths

Researchers can examine regurgitated penguin droppings after washing them to find otoliths, which are the tiny ear bones of fish. These bones resist digestion and allow identification of the fish species and size consumed.

How do researchers non-invasively reconstruct the recent diet of Adélie penguins?
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