For decades now, biologists have believed the number of Adélie penguins on the Antarctica peninsula have been declining. But scientists have just discovered a "supercolony" of more than 1.5 million of the penguins off of the peninsula's northern tip.

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The discovery is credited to researchers at the Woods Hole Oceanographic Institution who studied NASA satellite imagery of Antarctica's rocky Danger Islands and in 2014, noticed significant guano (seabird feces) stains on the rocks.

The massive number of stains was enough evidence to warrant further study of the area.

Since then, the researchers used drones to survey the Danger Islands. The devices took photos every second, and then the scientists stitched them together into a collage to show the entire landmass in 2D and 3D, researcher Hanumant Singh said in a statement.

Using those massive stitched images, his team used neural network software to search for penguin nests autonomously. They eventually found more than 750,000 pairs of penguins living in the same region.

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"Until recently, the Danger Islands weren't known to be an important penguin habitat," researcher Heather Lynch said in a statement, noting that these supercolonies have gone undetected for decades largely due to how remote and treacherous the islands and surrounding waters are.

"Not only do the Danger Islands hold the largest population of Adélie penguins on the Antarctic Peninsula, they also appear to have not suffered the population declines found along the western side of Antarctic Peninsula that are associated with recent climate change," coauthor Michael Polito also said in a statement.

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The researchers hope to conduct further study to understand why the penguins chose the Danger Islands and how they’re surviving in such huge numbers with the effects of climate change.

The new findings also lend enough evidence to support proposed Marine Protected Areas (or MPAs) near the Antarctic peninsula.

"Given that MPA proposals are based in the best available science, this publication helps to highlight the importance of this area for protection," Mercedes Santos, a scientist unaffiliated with the study, but on an international panel that decides on the placement of MPAs, said.

Read the full study at Nature.com.