A census of breeding seabirds conducted at eastern Heard Island in 2003–04 has confirmed long-term increases in the breeding population of king penguins and black-browed albatrosses.
The census was conducted in the ice free areas between Fairchild Beach in the northeast and Long Beach in the southwest. Seabird breeding colonies and nests were also mapped using the Global Positioning System (GPS). The census and GPS survey aimed to provide current information on the distribution and abundance of breeding seabirds on Heard Island and followed similar studies conducted in 2000- 01. Census data were also available for several species, from the 1940s to the present, allowing long-term trends in the breeding populations of these species to be assessed.
Since the late 1940s, breeding populations of king penguins have increased exponentially, doubling every five or so years. The current breeding population estimate is 60 000 pairs, with at least another 45 000 non-breeding birds present on the island during the 2003–04 summer. Similarly, the black-browed albatross population has trebled since the late 1940s. This increase is thought to be due to either improved breeding success resulting from regional warming, or the adults feeding at trawlers working within their foraging range, or both. The Heard Island black-browed albatross population is less than one percent of the global population, but its increase is counter to almost all other populations, which are decreasing because of interactions with longline fisheries.
While the king penguin and black-browed albatross populations on Heard Island are increasing, historical images and early surveys suggest that there are fewer colonies and reduced breeding populations of macaroni, rockhopper and gentoo penguins, than in the past. The reason for this is unknown and further surveys are required to confirm the trend.
Heard Island’s seabirds have not suffered the devastating impacts of human activities or introduced predators, such as cats and rats, suffered by similar populations on other subantarctic islands. These undisturbed seabird populations provide a valuable baseline and comparative data with breeding populations on other islands. Information collected during the 2000–01 and 2003–04 surveys will be used in the management of the Heard Island and McDonald Islands Marine Reserve and will allow status updates of these species, as required under legislation and national and international conservation agreements.
Eric Woehler
Institute of Antarctic and Southern Ocean Studies and Australian Antarctic Division