Scientists have stumbled across a huge group of previously unknown Adélie penguins on the most northerly point of the Antarctic Peninsula.
Numbering more than 1.5 million birds, they were first noticed when great patches of their poo, or guano, showed up in pictures taken from space.
The animals are crammed on to a rocky archipelago called the Danger Islands.
The researchers, who detail the discovery in the journal Scientific Reports, say it is a total surprise.
"It’s a classic case of finding something where no-one really looked! The Danger Islands are hard to reach, so people didn’t really try that hard," team-member Dr Tom Hart from Oxford University, UK, told BBC News.
The scientists used an algorithm to search images from the American Landsat spacecraft for sites of possible penguin activity.
Landsat does not return especially high-resolution pictures and so when the system flagged potential colonies, they had to be followed up with much sharper pictures for confirmation.
"And the sheer size of what we were looking at took our breath away," said Dr Heather Lynch from Stony Brook University, New York.
"We thought, ’Wow! If what we’re seeing is true, these are going to be some of the largest Adélie penguin colonies in the world, and it’s going to be well worth our while sending in an expedition to count them properly."
But, as the name implies, the Danger Islands are notoriously difficult to reach.
Even in the austral summer, the ocean surrounding the archipelago is filled with the kind of thick sea-ice that ships try to avoid.
However, in December 2015, the team did manage to get on the ground to begin its count. And one of the most effective techniques was to deploy drones, which flew above the birds to make large mosaics of their nesting sites.
"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," explained Prof Hanumant Singh from Northeastern University.