Grey-headed Albatross and chick on Bird Island, photograph by Stephanie Prince

 José Seco (Department of Chemistry, University of Aveiro, Portugal) and colleagues have published in the journal Environmental Pollution on mercury levels in Southern Ocean biota, including by analysis of feathers of chicks from five ACAP-listed albatrosses and petrels collected on Bird Island in the South Atlantic.

The paper’s abstract follows:

“Biomagnification of mercury (Hg) in the Scotia Sea food web of the Southern Ocean was examined using the stable isotope ratios of nitrogen (δ¹⁵N) and carbon (δ¹³C) as proxies for trophic level and feeding habitat, respectively. Total Hg and stable isotopes were measured in samples of particulate organic matter (POM), zooplankton, squid, myctophid fish, notothenioid fish and seabird tissues collected in two years (austral summers 2007/08 and 2016/17). Overall, there was extensive overlap in δ¹³C values across taxonomic groups suggesting similarities in habitats, with the exception of the seabirds, which showed some differences, possibly due to the type of tissue analysed (feathers instead of muscle). δ¹⁵N showed increasing enrichment across groups in the order POM to zooplankton to squid to myctophid fish to notothenioid fish to seabirds. There were significant differences in δ¹⁵N and δ¹³C values among species within taxonomic groups, reflecting inter-specific variation in diet. Hg concentrations increased with trophic level, with the lowest values in POM (0.0005 ± 0.0002 μg g⁻¹ dw) and highest values in seabirds (3.88 ± 2.41 μg g⁻¹ in chicks of brown skuas Stercorarius antarcticus). Hg concentrations tended to be lower in 2016/17 than in 2007/08 for mid-trophic level species (squid and fish), but the opposite was found for top predators (i.e. seabirds), which had higher levels in the 2016/17 samples. This may reflect an interannual shift in the Scotia Sea marine food web, caused by the reduced availability of a key prey species, Antarctic krill Euphausia superba. In 2016/17, seabirds would have been forced to feed on higher trophic-level prey, such as myctophids, that have higher Hg burdens. These results suggest that changes in the food web are likely to affect the pathway of mercury to Southern Ocean top predators.”

With thanks to Richard Phillips.

Reference:

Seco, J., Aparício, S., Brierley, A.S., Bustamante, P., Ceia, F.R., Coelho, J.P., Philips, R.A., Ryan A., Saunders, R.A., Fielding, S., Gregory, S., Matias, M., Pardal, M.A., Pereira, E., Stowasser, G., Tarling, G.A., Xavier, J.C. 2021.  Mercury biomagnification in a Southern Ocean food web.  Environmental Pollution 275. doi.org/10.1016/j.envpol.2021.116620.

John Cooper, ACAP Information Officer, 16 February 2021

The current island field team, Vonica Perold, Roelf Daling and Kim Stevens, during the annual count of incubating Tristan Albatrosses, photograph by Kim Stevens

 With the delayed attempt to eradicate Gough’s House Mice now once more underway it is hoped that from next year the island’s Critically Endangered Tristan Albatrosses will be able to breed without having to face many of their chicks succumbing to night-time attacks during the austral winter- as expressed in a Facebook post by the UK’s Gough Island Restoration Programme (GIRP):

A colour-banded Tristan Albatross reveals its egg during the annual count, photograph by Roelf Daling

“Numbers are in! Our team just returned from their island-wide count of incubating Tristan albatrosses and the total is 1439!  Due to mice predation, the breeding success of these gentle giants is exceptionally poor compared to similar species on rodent-free islands.  We aim to reverse the species’ fortunes by eradicating mice from Gough Island.  The only realistic chance of removing all the mice will be over the southern winter.  So, while we can’t prevent the loss of eggs and young chicks to mice this year, we do hope chicks which survive until the end of winter will then have a decent chance to fledge successfully.  And as adults start returning to the island in November for the onset of the next breeding season, this particular threat should hopefully have been removed once and for all!”

The Tristan Albatross, along with the equally Critically Endangered Waved Albatross Phoebastria irrorata of the Galapagos, have been chosen by ACAP as ‘feature species’ to support this year’s World Albatross Day on 19 June.  To this end 24 high-resolution posters suitable for display have been produced from three photographs of each species with texts in four languages, available for free downloading.  More artworks depicting both threatened species will follow as World Albatross Day approaches.

A ‘WAD2021’ Tristan Albatross poster, photograph and design by Michelle Risi

Read about the threats facing the Tristan and the other albatrosses in illustrated species summaries produced for the general public and for learners as part of last year’s World Albatross Day celebrations.

John Cooper, ACAP Information Officer, 15 February 2021

Lord Howe Island

In 2019, after a long period of discussion and planning, an operation to eradicate non-native Black Rats Rattus rattus and House Mice Mus musculus on Australia’s inhabited Lord Howe Island was carried out.  The Lord Howe Rodent Eradication Project included the use of over 20 000 poison bait boxes and the dropping of bait by helicopter away from areas of human habitation and activity over the southern winter.  As well as endemic land birds, the World Heritage Island supports breeding populations of burrowing petrels and shearwaters, all of which were known or thought likely to be deleteriously affected by the introduced predators.

The prevailing “rule of thumb” is that two years are allowed to pass before the success of an island eradication operation is officially announced.  This is to give sufficient time for any target animals possibly remaining to be discovered.  However, with only a few months to go before the two years are up it is notable that the natural environment on Lord Howe is flourishing.  No observations of rats, rebounding vegetation and invertebrate populations and the doubling of numbers of the endemic and Endangered Lord Howe Woodhen Hypotaenidia sylvestris (following their being taken into temporary captivity) are all welcome signs that have been recently reported.

Flesh-footed Shearwater pair and breeding habitat on Lord Howe Island

Photographs by Ian Hutton

As for the island’s procellariform seabirds, project biologist Terry O'Dwyer of the New South Wales Department of Planning, Industry and Environment states that “the breeding success rate of petrels on the island has jumped from 2 or 3 per cent to more than 70 per cent” following the eradication exercise.  Lord Howe supports breeding populations of Black-winged Pterodroma nigripennis and Providence P. solandri Petrels along with Flesh-footed Ardenna carneipes (a proposed candidate for ACAP listing), Wedge-tailed A. pacifica and Little Puffinus assimilis Shearwaters.

The likely success of the Lord Howe project, despite the earlier misgivings of some of the island’s human population, should provide lessons for eradications that might be planned for other inhabited islands, such as New Zealand’s Great Barrier Island and the United Kingdom’s Tristan da Cunha.  Both islands support ACAP-listed species that breed in the face of introduced predators.

Read more here.

John Cooper, ACAP Information Officer, 12 February 2021

The Pelagic Australis ready to sail from Cape Town Harbour

Following the cancelling of last year’s attempt to rid Gough of its House Mice that attack and kill many of the island’s seabirds – as a necessary consequence of the COVID-19 pandemic – the United Kingdom’s Gough Island Restoration Project announced last November its intention to make another attempt this year.  With the pandemic still raging globally it is good to report that the 2021 eradication exercise got going this week with the first sailing from Cape Town on Monday [1 February] on the yacht Pelagic Australis, as reported on the GIRP Facebook page:

“And they are off!  Fair winds and following seas to the first Gough-bound team members of the 2021 Restoration Project who set sail from Cape Town today!  The team and ship’s crew have all been living under quarantine for the last two weeks and had to pass multiple COVID-19 tests along their journeys before being allowed to board the ship.  We have many more COVID-19-related hurdles to navigate before the operation is completed, but we are delighted that the 2021 restoration is underway!”

Leaving the inner harbour

Photographs from the GIRP Facebook page, courtesy of the Royal Society for the Protection of Birds

The Gough sailing comes in the same week as the commencement of duties of the project manager for the Mouse Free Marion project, which will be learning from GIRP as it works towards eradicating albatross-killing mice on South Africa’s Marion Island in 2023 (click here).

POSTSCRIPT: The yacht has reached Gough Island.

"After nine days of sailing half-way across the South Atlantic, our first team has just landed at Gough Island for the 2021 operation, so we're all very excited that this bodes well for navigating all the Covid restrictions and hurdles that running the operation this year may bring! Greeted by the G66 ‘overwinterers’, the restoration team will be getting straight on with the job of preparing everything needed before the operation can begin. First up, creating temporary additional sleeping quarters ready for the arrival of the remaining team members!" - GIRP Facebook page.

John Cooper, ACAP Information Officer, 04 February 2021, reposted 11 February 2021, updated 12 February 2021