The Sub-Antarctic island of South Georgia is home to some of the world’s largest breeding aggregations of penguins. Long-term monitoring studies reveal that the local population trends are complex. Some species and colonies have rapidly declined, but others have increased or remained stable. For example, the local population of macaroni penguins rapidly declined between the 1970s and early 2000s. During the same period of time, the local king penguin population increased. Within each of these species, individual colonies changed at different rates and a small number changed in opposite directions. Thus, it appears that the penguin species and colonies of South Georgia have responded differently to climate change and anthropogenic pressures such as fisheries, and historic sealing and whaling activities that changed the community structure. Unravelling these processes is considered an important challenge and has been the focus of extensive research [1][2][3]. Recent work [4] on the macaroni penguin indicated that their survival rates are controlled by trophic levels both above and below them, highlighting the need to consider multiple drivers simultaneously. The population of penguins on South Georgia currently represents around 15% of the global macaroni penguin population, 26% of the global gentoo penguin population, 28% of the global king penguin population, and less than 1% of the global chinstrap penguin population.

Slideshow

In the Southern Atlantic Ocean, Bird Island sits off the north western tip of South Georgia. The Bird Island Research Station in Fresh Water Inlet supports the long-term monitoring of several different species of Antarctic predator. (photo Cat Horswill).

Macaroni penguins return to South Georgia in the Austral summer to breed. Some of the largest macaroni penguin colonies in the world can be found on South Georgia and its associated near-shore islands. (photo Mick Mackey).

Rafts of gentoo penguins return to Johnson Cove on Bird Island every night throughout the year. (photo Mick Mackey).

A macaroni penguin uses the surge of a wave to clamber up the rocks at the bottom of the Big Mac colony on Bird Island. (photo Cat Horswill).

A gentoo penguin comes ashore on Landing Beach, Bird Island. (photo Mick Mackey).

A pair of macaroni penguins bow to each other at their nest site. Bowing is often followed by an ecstatic display of loud braying. (photo Cat Horswill).

A pair of king penguins engage in a courtship display. The male flaunts his bill at the female. (photo Mick Mackey).

The king penguin colony at St Andrews Bay is one of the largest on South Georgia. The colony has over 100,000 birds. (photo Cat Horswill).

A pair of newly hatched gentoo chicks on Landing Beach, Bird Island. Each pair of gentoo penguins will hatch one or two chicks. (photo Cat Horswill).

A gentoo chick grows its adult feathers on Landing Beach, South Georgia. (photo Cat Horswill).

Curious king penguins at St Andrews Bay. (photo Mick Mackey).

Approximately one in every 1000 Antarctic fur seal pups is born with a blond leucistic morph. At South Georgia, Antarctic fur seals are considered to be a major competitor and predator of penguins during the breeding season. (photo Mick Mackey).

Many Antarctic fur seals concentrate their winter foraging in the waters around South Georgia. (photo Mick Mackey).

At South Georgia, giant petrels obtain food from marine and terrestrial sources by predation and scavenging. (photo Mick Mackey).

An elephant seal hides in the tussock grass on Bird Island. Non-breeding elephant seals often haul out away from the breeding beaches on the mainland. (photo Mick Mackey).

An elephant seal wallows in the shallows close to the king penguin colony at St. Andrews bay, South Georgia. The Cook Glacier on the left and the Heaney Glacier on the right extend into the bay. (photo Cat Horswill).

Cat Horswill
British Trust for Ornithology

Mick Mackey
Freelance photographer

References

[1] Croxall, J.P., Trathan, P.N. & Murphy, E.J. (2002) Environmental Change and Antarctic Seabird Populations. Science, 297, 1510–1514.
[2] Forcada, J. & Trathan, P.N. (2009) Penguin responses to climate change in the Southern Ocean. Global Change Biology, 15, 1618–1630.
[3] Trathan, P.N., Ratcliffe, N. & Masden, E.A. (2012) Ecological drivers of change at South Georgia: the krill surplus, or climate variability. Ecography, 35, 983–993.
[4] Horswill, C., J. Matthiopoulos, J. A. Green, M. P. Meredith, J. Forcada, H. Peat, M. Preston, P. N. Trathan & N. Ratcliffe. (2014) Survival in macaroni penguins and the relative importance of different drivers; individual traits, predation pressure and environmental variability. Journal of Animal Ecology, 83, 1057-1067.
top