Whilst most seabirds of the Southern Ocean breed during the summer months, the grey petrel (Procellaria cinerea) takes an unusual approach: it rears its young in the middle of the sub-Antarctic winter. Snow, sleet and strong winds are part of everyday life on Macquarie Island – conditions to which this robust seabird species has adapted exceptionally well. At the same time, it plays an important ecological role by transporting nutrients from the Southern Ocean to land, thereby enriching the island’s ecosystems.
Historical records show that grey petrels were still breeding on Macquarie Island in 1911, but later disappeared completely. It was not until 1999 that breeding birds were recorded again – shortly after feral domestic cats had been successfully removed by the Tasmania Parks and Wildlife Service. With the subsequent eradication of rabbits, rats and mice, the recolonisation of the island continued. In addition to the elimination of rats as nest predators, the disappearance of the rabbits also allowed the dense tussock grass stands to regenerate, providing the birds with ideal breeding sites.
Grey petrels lay a single egg in March or April. The chicks hatch in May or June and then spend more than 100 days in their underground nesting burrows before fledging in the spring.
For the first time since 2018, a team from the Australian Antarctic Division (AAD) is once again systematically surveying the breeding colonies. Wildlife biologist Dr Sarah-Lena Reinhold, gamekeeper Karina Sorrell and ranger Gemma Rushton are using special burrow scopes to search for breeding burrows and record eggs, chicks and adult birds. The work is arduous: the researchers often have to crawl for hours through dense tussock grass and muddy terrain to track down the hidden nests.
Despite the encouraging return to Macquarie Island, the grey petrel remains threatened worldwide. Among the greatest threats are bycatch in commercial longline fisheries, the impact of climate change on food availability in the Southern Ocean, and increasing marine plastic pollution.
The current survey will continue over several years to produce an updated population estimate for the entire island for the first time in a long while. The data collected is intended to show how the populations are developing and to further improve conservation measures for this threatened species. The monitoring forms part of the inter-agency Macquarie Island Wildlife Monitoring Programme and also provides important information for the Agreement on the Conservation of Albatrosses and Petrels (ACAP). The return of the grey petrels is a striking example of how effective, consistent conservation measures can enable the repopulation of previously lost breeding grounds.
Rosamaria Kubny, Polarjournal