(CNN) If you ever find yourself hanging out on Antarctica's Danger Islands, we hope you like penguins. There's a lot of them there.

A previously unknown "mega-colony" of Adelie penguins have been found on the islands, which sit on Antarctica's northern tip.

More than 1.5 million of the birds were found in 2015 during a survey of the area, according to a report in the journal Scientific Reports.

Researchers estimate the Danger Islands hold the largest colonies of Adelie penguins in Antarctica and the third- and fourth-largest colonies in the world. Even more interesting, scientists think the penguins have flourished on the Danger Islands for decades, while other colonies of the birds have declined on other parts of the continent, especially on its western half.

So how were all those birds missed for all these years? Well, the Danger Islands are fairly remote, even by Antarctica standards. It's locked up in sea ice most of the year, and even in summer it's difficult to reach.

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