Researchers used a drone to capture images of a huge, previously unknown colony of 1.5 million Adelie penguins on the Danger Islands, The New York Times reported Monday. The colony of roly poly tuxedo wearers are located between the tip of South America and Antarctica, and originally gave themselves away by leaving enough of their pink-colored poop smeared across the island that it was visible via satellite. For 40 years, researchers had thought the population of Adelie penguins was declining, but it turns out they are just very good at hiding.

It took several years for scientists to prepare an expedition to go take a penguin census, as well as create a drone that could withstand the weather — the temperature in the Danger Islands averages between 0 and -10 degrees Celsius throughout the year. The islands not only have extreme temperatures, but are surrounded by difficult-to-navigate waters. The penguins do not mind.

“The drone lets you fly in a grid over the island, taking pictures once per second. You can then stitch them together into a huge collage that shows the entire landmass in 2D and 3D,” Hanumant Singh, Professor of Mechanical and Industrial Engineering at Northeastern University and co-principal investigator on the study, told the Woods Hole Oceanographic Institution.