Penguin poop visible from space just helped scientists discover a previously unknown, massive colony of Adélie penguins on a chain of remote Antarctic islands, according to a new study published in Scientific Reports.

In 2014, Stony Brook University's Heather Lynch and NASA's Mathew Schwaller identified guano stains in satellite images of the Danger Islands, a rocky archipelago off the Antarctic Peninsula. The visible guano marks signaled that a large population of penguins was living there. When the scientists launched an expedition to the islands to learn more, and counted birds by hand and with a camera-equipped drone, they discovered a "supercolony" of more than 1.5 million Adélies.

"Until recently, the Danger Islands weren't known to be an important penguin habitat," Lynch said in a press release. By this count, the islands are actually home to the largest population of the species on the Antarctic Peninsula.

The Danger Islands were discovered by British explorer James Clark Ross in 1842, and got their name from the fact that they are often hidden under ice. Ross and his crew almost crashed their ships on them—"appearing among heavy fragments of ice, they were almost completely concealed until the ship was nearly upon them," as the USGS's Geographic Names Information System explains. They're still hard to access and dangerous to visit because of the thick ice that surrounds them. And that makes them perfect for penguins.

Thomas Sayre McChord, Hanumant Singh, Northeastern University, © Woods Hole Oceanographic Institution

Penguins depend on sea ice for survival, and in places where sea ice is disappearing, their populations are declining. The western Antarctic Peninsula has seen huge declines in Adélie penguin populations as the ice has melted—up to 80 percent in some colonies since 1981, by one estimate. But because of the geographic variation in how climate change has affected temperatures, the population decline hasn't been the same everywhere, and other colonies have even grown. This new discovery tracks with Lynch's previous research, which has found that the impact of climate change on Antarctic penguins will be highly variable depending on the location.

“Just because a huge colony was just found doesn't mean that colonies in areas where sea ice isn't great aren't declining," University of Minnesota ecologist Michelle LaRue wrote in an email to Mental Floss. “If the sea ice conditions at the Danger Islands colony all of a sudden saw similar trends in sea ice decline, I would still expect that colony to decline, too." LaRue has worked with Lynch to study penguin populations before, but wasn't involved with this latest study.

The paper also shows how useful the combination of satellite, ground observation, and drones can be in counting penguins in remote areas. The drone was able to capture images like the one above every second as it flew over the island, creating 2D and 3D views of the whole area. This made their overall population count more accurate, which will aid researchers in tracking changes in the colony as time goes on.