Changing numbers

  • Arjen, do you want to go to the Adelies?
  • Sure, why not?

We were at Petermann Island on the Antarctic Peninsula and I had been standing at a Gentoo Penguin colony. A nice day, sunny, relatively warm (too warm for the Peninsula…) and I had been observing our Chinese guests and Gentoo Penguins for a while. Adelies would make a nice change.

The last Adelie Penguins at Petermann Island?

When I was at Petermann 10 years ago, around 15% of the colony were Adelie Penguins, the other 80% Gentoo. This was already a big change from 80% Adelies back in the early eighties of the previous century. Now I’d only seen a few Adelies, but this question over the radio made me believe the large part of the colony was somewhere else. When I arrived at the right place, I only saw 20 pairs of Adelie Penguins, together with many Gentoos. I kept on looking for a while, but it turned out this was it! From the nearly 500 breeding pairs in 2005/2006, only less as 50 were left (this is not an official count, just the impression that I had while standing there).

The exact reason for the decline of the Adelie Penguins and the increase of the Gentoo Penguins at this site more research is needed as I could do in the few hours I was there. However, the Adelie Penguin is a true Antarctic species, breeding only on the southern parts of the Antarctic Peninsula and on mainland Antarctica. The Gentoo Penguin is a much more generalist species, breeding on the (warmer) northern parts of the Peninsula. It would make sense that the Gentoo can cope better with the changing circumstances as the more cold-adapted Adelie…

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