Penguin Research Update from South Georgia Newsletter

Baby King Penguins, Where Do They Go?

Little was known about where king penguin chicks go when they fledge and first head to sea, or why some survive their first year when many don’t, so researchers have been trying to answer these questions with fieldwork based in South Georgia and the Falkland Islands.

To discover where newly fledged king penguin chicks go researchers put small satellite tags on chicks in two colonies in December 2007. The study sites in South Georgia and the Falklands contrasted, being located on different sides of the Antarctic Polar Front (APF) and having a different climate. The APF is a key oceanographic feature generally thought to be important for king penguin foraging success.

Of the fledglings tracked, eight penguins were tracked for periods greater than120 days; seven of these (four from South Georgia and three from the Falkland Islands) migrated into the Pacific. Results showed that birds from both sites foraged predominantly in the vicinity of the APF. Only one bird, from the Falkland Islands, moved into the Indian Ocean, visiting the northern limit of the winter pack-ice; three others from the Falkland Islands migrated to the eastern coast of Tierra del Fuego before travelling south. The birds usually swam no more than 10km in a day, though they could travel more than 100km in 24 hrs. The tracks of the tagged birds from the two colonies can be seen in the figure below.

Though migratory behaviour from both sites was broadly similar, the young birds from the Falkland Islands spent more time in comparatively shallow waters whilst the new fledeged birds from South Georgia spent more time in deeper waters. The satellite tracks also showed that, to start with, the young birds stayed clear of areas being used by adult birds. King penguins usually spend four or five years “exploring the Southern Ocean” before they settle down and start breeding, the researchers noted.

A paper on the study entitled ‘Post-fledging dispersal of king penguins (Aptenodytes patagonicus) from two breeding sites in the South Atlantic’ was published in PLOS ONE on May 14th by authors Kelmens Putz, Phil Trathan, Martin Collins, Sally Poncet and Benn Luthi.

The satellite tracks obtained from the South Georgia juvenile king penguins. The breeding site is marked by a yellow asterisk over South Georgia. Track colours represent a monthly time scale, with positions in pink (December 2007), blue (January 2008), yellow-green (February), orange (March), golden (April), red (May), olive (June), violet (July) and green (August 2008). The black line indicates the approximate position of the Antarctic Polar Front.

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Ten Year Study Of Bird Island Macaroni Penguins

Scientists at Bird Island have been studying macaroni penguins for over ten years. The BAS-led team of scientists studied the birds during a period that their numbers were declining. The macaroni penguin population on South Georgia has declined by almost 70% since the early 1980s.

The electronically tagged macaroni penguins are recorded by a sensor as they pass through this gate at the entrance to their colony on Bird Island. Photo BAS.

Since 2003 birds that had been fitted with small electronic tags have passed an electronic scanner at the entrance to the colony, which records the birds as they come and go. The resultant data was analysed to determine survival rates. The results have now been presented in a paper.

The penguins’ survival rates are influenced by both environmental and predation pressures. The scientists found penguins were particularly vulnerable to predation by other seabirds such as giant petrels. The macaroni chicks were found to be particularly vulnerable, with only a third surviving their first fledgling year.

Catharine Horswill, from BAS, said: “Penguins are facing rapid changes in their environment, but at South Georgia we found compelling evidence that predators are the most important factor influencing the survival of chicks as they leave the colony for the first time. This is a big leap forward as we had no idea that predation could be such a strong driving force. Knowing what drives survival rates of penguins puts us in a much better place to predict how these populations may change in the future.”

The research paper, ‘Survival in macaroni penguins and the relative importance of different drivers; individual traits, predation pressure and environmental variability.’ is published by the Journal of Animal Ecology.
Info BAS

This very short video shows the macaroni penguins crossing the recording bridge.

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