More Adelies

Just before leaving on the previous trip, an article was published in Nature where the discovery of a colony of 1.5 million Adelie Penguins was announced. An earlier, partial, count had resulted only in 300.000 penguins, meaning another 1.2 million penguins were discovered. The Danger Islands, where these colonies were found, consist of nine islands, seven of which have significant colonies of Adelies. Most of these colonies were never counted.
As I got quite a few questions about this during the trip, a little info in this post.

How is it possible that so many penguins were unnoticed?
Antarctica is a vast continent, and most of it is rarely visited by humans, so it is well possible that colonies, even of this size, stay unnoticed for a long time. The Danger Islands, where these colonies are found, are located on the northeastern side of the Antarctic Peninsula, the area which is visited most by both scientists and tourists (most of my trips go to this area as well). That makes the discovery of these colonies slightly more surprising, but the Danger Islands are in a quite shallow part that is often blocked by sea ice from the Weddell Sea Gyre. This makes that these islands are rarely visited.

Adelie Penguin colony at Franklin Island


Is it likely that there are more unknown large colonies?
It is, of course, difficult to say things about things that aren’t discovered yet. But I would definitely not be surprised if more (significant) colonies of Adelie or Emperor Penguins will be made in the next couple of years. We will keep on exploring new areas, and with improved satellite images it will be easier to find colonies in remote locations which then can be counted with the use of UVA’s (as was done in this case).

What does this mean for the population of Adelie Penguins?
Simply said, we now know that there are 1.2 million Adelies more as we thought previously. As these colonies were never counted, we can’t say that the population has increased. The total known number on the West Antarctic Peninsula and the north-western part of the Weddell Sea are now more as doubled (without the Danger Islands a little over 600.000 breeding pairs of Adelies were known in this area (and now 750.000 pairs in the Danger Islands).

A moulting Adelie Penguin 


Can anything be said about how Adelie Penguins are doing? What about Climate Change?
On the West Antarctic Peninsula, the population of Adelie Penguins is declining. They are dependent on sea ice, and a rapid decrease of this is found in this area, resulting in a decrease in Adelie numbers. On the Weddell Sea (eastern) side of the Peninsula, this decrease is not apparent. This side still has a lot of sea ice, brought north with the Weddell Sea gyre, resulting in reasonably stable numbers of Adelie Penguins. The only population on the Danger Islands that was counted before, the one on Heroína Island, seems stable, with around 300.000 breeding pairs both in 1996/1997 and in this study.

This stable trend is also found in other parts of the continent.

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