A supercolony of about 1.5 million Adelie penguins was discovered in the Danger Islands. Why weren't they discovered before, and how did the scientists determine the number of birds on the islands?
Adelie Penguin Supercolony Discovered
The global Adelie penguin population has been believed to be continuously declining in the last decades, sparking concern and worry for the species. In fact, just last October, disaster struck a colony of Adelie penguins when only two out of 40,000 chicks survived starvation. The incidence was so devastating that some have called it "Tarantino does Happy Feet" because of the sheer number of penguin deaths.
Now, in contrast to devastating news of animal deaths and population decline, researchers announced the discovery of a previously unknown Adelie penguin colony of about 1.5 million birds. The rediscovery was made thanks to 2014 NASA satellite imagery of extensive guano stains in the islands, suggesting that the islands hosted a large number of penguins.
Since 2015, a team of researchers have been studying the massive penguin population in the islands, which is said to have 751,527 pairs of Adelie penguins. That is more than the rest of the Antarctic Peninsula combined. In total, the researchers surmise that the islands host a population of about 1.5 million Adelie penguins plus several population of gentoo penguins in Brash Island and 27 nests of chinstrap penguins at Heroina Island.
What Took So Long To Make The Discovery?
The Danger Islands are so named for a good reason. It's not easily accessible. It is made up of nine islands which stretch to about 35 kilometers in the northernmost tip of the Antarctic Peninsula. Although the islands aren't exactly remote, the currents brought in by the Weddell Sea moves sea ice northward, making access to the islands quite difficult. In fact, even its most accessible island, Heroina Island, only sees one ship docking per year.
Furthermore, even though a previous geological survey captured images of Adelie penguins on all the islands before, it was only when the satellite survey hinted the possibility of a large penguin population that their presence went noticed.
How Did Researchers Count The Penguins?
It wouldn't have been easy to track 1.5 million penguins on nine islands, so how did the researchers count them? The researchers combined good old manual labor with technology. In their land surveys, researchers manually counted the nests they saw, counted the nests in the captured panoramic photographs, and counted the individual penguins from the images captured by the quadcopter.
The quadcopter was flown above the islands no higher than 45 meters to maintain the image quality for individual penguin identification. It took pictures of the island once per second, and the researchers combined the photographs into a collage which displayed the islands in both 2D and 3D. With the available images, researchers then used a neural network software to analyze the images by the pixel in search of penguin nests.
The Importance Of Danger Islands
Until this discovery, the Danger Islands were not known to be an important penguin habitat. Now, however, it is considered a hotspot. Apart from the fact that the islands host a large population of penguins that are declining in numbers elsewhere, the importance also lies not just in how many penguins there are, but also in how they have thrived in such large numbers in that particular area.
"The population of Adélies on the east side of the Antarctic Peninsula is different from what we see on the west side, for example. We want to understand why. Is it linked to the extended sea ice condition over there? Food availability? That's something we don't know," said Michael Polito of Louisiana State University, coauthor of the paper.
The paper is published in the journal Scientific Reports.