Abandoned 'supercolony' may hold clues to penguins' response to climate change

More than 600,000 Adelie penguins nest on Cape Adare,
Antarctica. Photo credit: Steve Emslie, UNCW

ANTARCTICA – Researchers recently discovered that Antarctica’s most populous colony of Adélie penguins may have once been nearly twice the size it is today. Clues about why the colony grew so large and what caused the population to decline could help scientists chart the penguins’ response to changes in climate and food resources.

Collaborative research conducted by Louisiana State University (LSU), University of North Carolina Wilmington (UNCW), University of California at Santa Cruz and University of Saskatchewan led to this discovery at Cape Adare, Antarctica.

“The goal of this multi-institutional collaborative project is to use penguins as sensitive indicators of past changes in the Antarctic marine environment,” said LSU Assistant Professor Michael Polito, the principal investigator of the project.

"Samples from this newly discovered ancient colony at Cape Adare will allow us to track the penguins’ diets and population movements relative to natural and human-induced shifts in climate and food availability.”

Last month, a research team led by UNCW Professor Steve Emslie visited the large breeding colony of Adélie penguins at Cape Adare in the northern Ross Sea, which currently has more than 338,000 breeding pairs in one area.

During this visit, they found an abandoned 'supercolony' on an upper ridge, which the researchers estimate was populated by more than 500,000 breeding pairs or more than 1 million penguins based on the total area of the abandoned nesting sites.

About 2,000 years ago there may have been a large influx of penguins to the colony at Cape Adare as climate shifted causing ice to block access to other nesting colonies farther south along the Antarctic continent, the researchers theorise. As the Cape Adare colony grew, the nesting grounds expanded to the upper ridge. However, a supercolony can thrive only as long as rich food resources are available.

“Many seabirds have large breeding colonies today that are located near abundant food resources,” Emslie said.

“Most of those colonies are in decline, though, due to changing ocean temperatures and other factors that impact those food resources.”

The researchers will use radiocarbon dating to pinpoint the age of the abandoned nesting sites and stable isotope analysis of the colony’s ancient penguin feathers and eggshells to determine what the penguins’ diets were at the time the supercolony was active. This will lead to further clues as to when and why the Cape Adare colony shrunk to its current size.

“Understanding the past diets and population movements of penguins will help us better understand how these predators, and the Antarctic marine ecosystem as a whole, will respond to current challenges such as global climate change and expanding commercial fisheries,” Polito said.

Source
Clues to penguins' response to climate change may be uncovered in recently abandoned 'supercolony' [news release], 16 February 2016, Louisiana State University