Yesterday evening, the skies darkened… Not just the impending dusk, but the arrival of Great Shearwaters in their tens of thousands. They had spent the day at sea, congregating in huge rafts just offshore and were now descending upon the land. For the Great shearwaters, it is the start of the breeding season, so pairs are beginning to take up residence in their burrows. A little later, as we wandered up to helipad, the night air was filled with a multitude of calls – not just those of the shearwaters, but also those of Atlantic petrels, Soft-plumaged petrels and White-faced storm petrels –strangely resembling what one might imagine to be an enormous crèche of human babies babbling away to each other. In the torchlight, we could see their ghostly shapes soaring above our heads, as they were making their way to their nest burrows.
It’s an amazing wildlife spectacle. But it’s just a typical night around the Gough Island field base. At least, it is when the wind and rain of the Roaring Forties subside.
During the day, the spectacle continues. Above the cliff-side, Sooty albatross are soaring, sometimes in synchronous formation on their courtship flights, or landing on the cliffs to begin nesting. As we have been hiking the mildly treacherous path along the top of the cliffs, we have encountered nesting “mollies” – Atlantic yellow-nosed albatross sitting on the perfectly cylindrical mounds of mud that constitute a nest. In recent days, we have spotted some of the mollies sitting on the first eggs of the season – an entire year’s worth of reproductive investment encapsulated in one precious egg. Down on Seal Beach, the Northern rockhopper penguins have arrived, scrambling over the rocky ledges and squabbling over nest sites. Around us, the flightless Gough moorhens scurry amongst the tussock grass and bog ferns. Occasionally, we have been lucky enough to spot inquisitive Gough buntings – either the territory-holding adults, or “streaky” juveniles – foraging for seeds or insects.
Gough Island is a bird (and bird-lover’s) paradise. But it is a paradise rapidly being degraded. The impact of the introduced mice and their predation on seabird chicks is sadly one of the reasons that Gough is now most famous.
Two days ago, we hiked up into the hills that rise steeply to the centre of the island, to the place named Gonydale – rugged and picturesque like a Scottish glen, but even more notable as a breeding site for the Tristan albatross, or “gonies” as they're known on Tristan and after which the valley is named. We were delighted to find a number of Tristan albatross chicks, still in nests scattered throughout the valley, steadily shedding their down and waiting for their flight feathers to grow in. Yet here we witnessed the devastating impact of the mice. Of the Tristan albatross nests that have been monitored by the RSPB’s overwintering team, only about one in five have made it to the stage of a chick close to fledge – roughly a quarter of the breeding success rate that should be expected for the species. So many of the chicks have died as the result of the predatory mice literally eating them alive – the wounds evident on their bodies.
The impact of chick and egg predation by mice is mirrored throughout so many of Gough’s other seabirds, and Gough buntings, who also struggle to raise chicks.
All this helps to explain why our team of five arrived on Gough nearly two weeks ago, having boarded the research vessel Agulhas II in Cape Town, ten days previously. Among us are a helicopter pilot, a structural engineer, a logistics specialist, an island eradication expert and myself, an aviculturist. Our goal is to develop the action plan for the RSPB’s project to eradicate mice from Gough Island in 2020, with support from the governments of Tristan da Cunha, South Africa and the UK.
One of the reasons why Gough is attractive to so many seabirds is its remote location, 800km south of Tristan da Cunha, itself recognised to be the most remote island community in the world. It is this remoteness that will present so many challenges to the project. There is only one scheduled voyage each year to Gough, the Agulhas II, on which we arrived. People and cargo must be airlifted onto the island by helicopter from the ship (except for the very brave who could take a small boat to shore and are lifted up the cliff in the basket of a crane).
Obviously there will be no opportunity to nip down to the builders’ merchants or supermarket if we forget to pack something. So we have been trying to meticulously plan the logistics for the project for which resources will include four helicopters, eradication gear, avicultural equipment, and all the supporting infrastructure necessary to accommodate the team and our activities.
The mouse eradication effort has a proposed timeline for May-July, specifically to coincide with the winter when the majority of Gough’s seabirds are out at sea, rather than incubating eggs or raising chicks. But the island’s two endemic landbirds, the bunting and the moorhen, inhabit Gough all year round. So I have been developing the plan that will ensure that the bunting and moorhen populations will stay secure throughout the eradication effort. To achieve this, the team will need to capture a number of buntings and moorhens and keep them in a captive setting, before releasing them when we are sure the baiting is complete and it is safe for the birds to return to the wild.
We will need to construct cages and pens, as well as a veterinary clinic and food prep tent. It will be a major challenge to house the birds in facilities that will not only withstand the notorious Gough weather, but will be constructed around the rugged terrain, tussock grass and seabird burrows. Several previous studies have already kept buntings and moorhens briefly in captivity on Gough, and have successfully developed appropriate diets – this is not as simple as it sounds since there are biosecurity issues associated with bringing food containing seeds and insects to Gough. Arguably the biggest challenge of all will be the actual capture of the birds, transporting them from isolated locations along the precipitous and very slippery footpaths back to the Gough Island base – a job for only the most skilful and athletic of fieldworkers.
This fortnight has been full of “firsts” for myself. I have watched a southern right whale relaxing amongst kelp in the bay. I have been introduced to pairs of curious buntings as they responded to the recordings of other birds, whom they perceived had entered their territory. I have been surprised to see moorhens scavenging at the carcasses of dead seabirds. I have survived my first close encounter with a skua, but have scratches on my knees after failing to dodge the defensive bites of rockhoppers. I have experienced (and outlived) the carnivorous feast of my first braai (South African barbecue). I have witnessed the splendour of an adult Tristan albatross soaring through Gonydale, before landing at its nest to feed its enormous chick. But I have also witnessed for the first time the devastating impact that the introduced mice are having on Gough’s birds and fragile island ecology, emphasising why it is so crucial that we must restore this ecosystem to its pristine state, by eradicating the mice.
Blog by Richard Switzer, Senior Conservation Officer and Aviculturalist for The Gough Island Restoration Project
Acknowledgement
The Gough Island Restoration Programme is being carried out by the RSPB in partnership with Tristan da Cunha, BirdLife South Africa and the Department of Environmental Affairs in South Africa and Island Conservation. The programme is part-funded by the RSPB, the UK Government, the National Fish and Wildlife Foundation and other generous individuals and organisations. If you would like to support our efforts to save the Critically Endangered Tristan albatross and Gough bunting, please get in touch or you can donate using our online form.