Penguins in press
Penguin research made the scientific spotlight this year, as Australian Antarctic Division scientists clarified how many emperor penguin colonies call the Australian Antarctic Territory home, and revealed some good news on the resurgence of king penguins on Macquarie Island, after their encounter with near-extinction.
Counting emperor penguin colonies
When is a cluster of emperor penguins not a colony? According to Australian Antarctic Division penguin biologist, Dr Barbara Wienecke, emperor penguins (Aptenodytes forsteri) congregate when they moult or mate. However, it is only groups of penguins with chicks that can be truly identified as a breeding colony. This distinction has contributed to confusion over how many emperor penguin colonies there are in the Australian Antarctic Territory (AAT), with estimates of 13, 15 and 17 colonies. In addition, some reported colony sightings have never been confirmed.
To try and reduce the uncertainty over the number of emperor penguin colonies in the AAT, Dr Wienecke collated observations from expedition narratives, log book entries, published literature, maps, photographs and satellite images, from the 1950s to today. She then excluded sightings of birds without chicks, airborne sightings not confirmed by a ground visit, and sightings that were never confirmed on subsequent visits.
'When emperor penguins are observed in January/February, there is a possibility that they have gathered at a moult location, which is not necessarily the same as their breeding site,' Dr Wienecke says.
'Even in winter, a group of emperor penguins is not immediately indicative of a breeding colony unless breeding activities are observed – such as incubation or the presence of chicks. Juveniles and sub-adults are rarely seen at the colonies and it is likely that they congregate anywhere on the ice.'
Dr Wienecke's review identified 11 confirmed breeding colonies in the AAT and 8 unconfirmed breeding colonies. Two of the confirmed colonies, at Taylor Glacier and Auster, are part of long- term population studies. As a result of this study Dr Wienecke recommends a change to the listing status of emperor penguins by the International Union for the Conservation of Nature, from 'of least concern' to 'data deficient'.
'As we have no firm understanding of the number of existing breeding colonies, we cannot estimate the size or trends of the global population of emperor penguins. We need to explore the coastline of the AAT in detail to help resolve this,' she says.
The application of remote sensing technology may prove an efficient and effective way to do this. Recently, the British Antarctic Survey used satellite images of the Antarctic coastline to identify likely emperor penguin colonies, based on faecal stains. Ground visits or high resolution images can now be used to confirm these sightings.
'This is an exciting new development that has brought us one step closer to assessing how many colonies there really are, both in the AAT and right around Antarctica,' Dr Wienecke says.
- Barbara Wienecke. Emperor penguin colonies in the Australian Antarctic Territory: how many are there? Polar Record, 45(0): 1-9, 2009.
- Barbara Wienecke. The history of the discovery of emperor penguin colonies, 1902-2004. Polar Record, (in press).
King penguin populations bounce back from the brink
Macquarie Island king penguins came close to extinction in the late 19th and early 20th centuries, as blubber oil gangs supplied a commercial oil market and collected eggs for food. At least two breeding colonies, thought to number in the hundreds of thousands of birds, were reduced to piles of bones or a few thousand birds between 1810, when the island was discovered, and 1912. However, once exploitation ceased in 1918 and the island became protected, there was a resurgence in the population of these resilient birds.
In 1995 scientists from the Australian Antarctic Division observed the first eggs laid near the site of one mass slaughter, at Gadget Gully on The Isthmus (see map). The first chick was fledged in 1996. Over the next five years the colony increased on average 66% per year.
A second colony at Lusitania Bay increased from a remnant population of about 3400 birds, in 1930, to about 170 000 breeding pairs in 2000. This population has begun to spill over into nearby breeding ground, which includes The Isthmus.
'Currently there are four king penguin colonies on the east coast of Macquarie Island: one each at Lusitania Bay, Green Gorge, Sandy Bay and now The Isthmus,' Antarctic Division biologist, Dr John van den Hoff, says.
Evidence of local king penguin population fluctuations prior to human interference is also apparent on the island, possibly due to landslips, storm events, volcanic activity, food availability, and a 'catastrophic mid-Holocene event'.
Dr van den Hoff says the ability of king penguin populations to overcome such odds suggests that they are resilient to catastrophic events.
'This may be because their breeding cycle ensures that some proportion of the breeding and non-breeding populations are absent from breeding islands during the year, providing a buffer and continued potential for population growth,' he says.
Dr van den Hoff proposes that a non-invasive study of the Gadget Gully colony be established, to help scientists understand the breeding cycle of king penguins at Macquarie Island and clarify how this cycle responds to changes in food availability, due to climate variability.
- John van den Hoff, Clive R. McMahon and Iain Field. Tipping back the balance: recolonization of the Macquarie Island isthmus by king penguins (Aptenodytes patagonicus) following extermination for human gain. Antarctic Science, 21(3): 237-241, 2009.
- King penguins recolonise Macquarie Island – news story