Earth ObservatoryScienceEarth ObservatoryPink Penguin Guano Provides…EarthEarth ObservatoryImage of the DayEO ExplorerTopicsAll TopicsAtmosphereLandHeat & RadiationLife on EarthHuman DimensionsNatural EventsOceansRemote Sensing TechnologySnow & IceWaterMore ContentCollectionsGlobal MapsWorld of ChangeArticlesEarth Matters BlogBlue Marble: Next GenerationEO KidsMission: BiomesAboutAbout UsSubscribe🛜 RSSContact UsSearch Pieces of sea ice drift near Antarctica’s Danger Islands in this image, acquired on January 22, 2023, by the OLI (Operational Land Imager) on Landsat 8. Several of the islands are stained pink by guano from Adélie penguins with a krill-rich diet.NASA Earth Observatory/Michala Garrison The pinkish orangey hues of Antarctica’s Danger Islands aren’t due to minerals in the rocks or lichens covering them. Instead, the color comes from the islands’ iconic black and white inhabitants. Dense colonies of Adélie penguins on Antarctica’s islands and coasts produce large quantities of guano, extensive enough to be seen in satellite images. The color of the droppings can even provide clues into the penguins’ diet, since krill tints the guano pink, giving researchers a unique way to monitor penguin populations. Analyzing three decades of Landsat images, scientists found that Adélie penguin diets vary around the Antarctic continent and are tied to sea ice conditions. In areas with less sea ice, the penguins have a krill-rich diet; in areas with more sea ice, they eat more fish, which is associated with healthier long-term population trends. ‘Sea ice is such a hugely important factor in the Antarctic marine environment,’ said Casey Youngflesh, an assistant professor at Clemson University in South Carolina who led the new study. ‘The structure of the region’s food web is changing in response.’ A colony of Adélie penguins is visible in this image captured by a drone during a research expedition to the Danger Islands.Thomas Sayre-McCord/WHOI/MIT Adélie penguin colonies might be remote and often inaccessible, but the stark and treeless Antarctic environment provides a rare opportunity to study the entire population from space, Youngflesh said. Previous research identified colonies based on satellite images of guano stains on rocky shores. Youngflesh and his colleagues visited the colonies to collect and analyze guano samples, allowing them to link specific color spectra observed by satellites to the balance of krill and fish in penguin diets. Now, surveying more than 100 sites around the perimeter of Antarctica with Landsat images captured between 1984 and 2013, the scientists have connected penguin diets to the surrounding sea ice conditions during the breeding and nesting seasons. Between November and February, colonies around the Antarctic Peninsula and West Antarctica, where temperatures were warmer and sea ice sparser, favored a krill-based diet. In East Antarctica, where sea ice cover was more extensive, colonies feasted on more fish—a higher-quality food resource and one that leads to better chick growth and survival. A given colony’s diet also changed year to year with shifting sea ice conditions. Antarctic sea ice was relatively stable, or even increased in some regions, during the years of the study. However, since 2013 Antarctic sea ice has reached record lows, with decreasing sea ice predicted for the future. That could lead to Adélie penguins leaning more heavily on krill, Youngflesh said. But the demand for krill is increasing, he noted, due to fishing and rebounding populations of other predators like seals and whales. The researchers are now developing computer models to use Landsat 8 and Landsat 9 data to continue tracking penguin diet and how the population responds to environmental change. NASA Earth Observatory image by Michala Garrison, using Landsat data from the U.S. Geological Survey. Drone image by Thomas Sayre-McCord (Woods Hole Oceanographic Institution/MIT). Story by Kate Ramsayer. Downloads January 22, 2023 JPEG (2.51 MB) Drone image JPEG (1.35 MB) References & Resources Clemson News (2026, July 7) Clemson researcher uses satellites to track what penguins eat from space. Accessed July 24, 2026. Landsat Project Science Support (2018, December 12) Determining Penguin Diet with Landsat (and Piles of Poo). Accessed July 24, 2026. NASA Earth Observatory (2017, June 13) Penguin Droppings Are Fertile Ground for Science. Accessed July 24, 2026. Youngflesh, C., et al. (2026) Space-based monitoring of penguin diet links sea ice, food webs, and population change. Current Biology, 36(14), 3707-3714.e5. You may also be interested in: Stay up-to-date with the latest content from NASA as we explore the universe and discover more about our home planet. Barents Sea Tied to Low Arctic Sea Ice 4 min read Patches of open water in the region contributed to low sea ice extent across the Arctic in March 2026, which… Article Record-Setting Retreat of Hektoria Glacier 5 min read Scientists relied on satellite data to understand how the Antarctic glacier lost so much ice so rapidly. 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