Melting glaciers opened new nesting real estate for Adélie penguin in Antarctica. The penguins’ march into new breeding space helped fuel a baby boom for the birds.
Glaciers and steep cliffs limit the expansion of Beaufort Island Adélie penguin (Pygoscelis adeliae) colony’s nesting grounds. Earth scientists recently documented how as the glaciers retreated, young penguins slowed their emigration from the island and starting putting down roots in the newly ice-free areas, especially after 2005.
Beaufort Island lies in the Ross Sea, one of the most isolated and pristine areas on Earth. The Ross Sea’s ice shelf covers 487,000 square kilometers (188,000 sq. mi.), approximately the size of France.
Although the glaciers are retreating on Beaufort Island, the sea ice there actually expanded in some parts of Antarctica as the region warmed. However, the PLOS ONE study authors noted this expanded sea ice also is more predictably pocked with holes called polynyas, which allow penguins access to the bird’s prey, such as crystal krill (Euphausia crystallorophias) and silverfish (Pleuragramma antarctica).
The increase in penguins may also be tied to a boom in silverfish populations, wrote the study authors led by Michelle LaRue of the University of Minnesota. Commercial fishing of the Antarctic toothfish (Dissostichus mawsoni) may have also reduced that fish’s predation on the silverfish leaving more for the birds, according to research published in Fish and Fisheries.
With both more abundant food and more room to hatch babies, the Ross Sea Adélie penguins may have benefited from industrial fishing and climate change, two human-related activities that have harmed many other species.
Over the 52-year study period, the Beaufort Island Adélie penguins increased nesting density and area, even opening up a new sub-colony on the north shore of the island. Three other penguin colonies nest in the Ross Sea area. These penguin populations also grew in recent years. Other Adélie groups haven’t been so lucky. The Adélies on the Antarctic peninsula have suffered due to loss of sea ice around the lower latitudes of the Antarctic continent.
IMAGE: The colony of Adelie Penguin at Cape Royds on Ross Island, Antarctica. (Peter West, National Science Foundation)