Conserving islands and their birds
Oceanic islands hold a disproportionately large amount of terrestrial biodiversity, yet are extremely vulnerable to introduced species: more than 90% of recent bird extinctions have been of island birds. Fortunately, eradicating invasive species can restore island ecosystems, provided there are strict controls on the subsequent import of people and materials. Birds are flagships for the conservation-management and restoration of island ecosystems. Our work focusses on South Africa’s Prince Edward Islands and the UK Overseas Territory of Tristan da Cunha and Gough Island.
This programme is mainly concerned with the impacts of introduced predators, especially House Mice Mus musculus, but also is involved in the eradication or control of introduced plants and invertebrates. The impacts of House Mice on seabirds were only discovered in the early 2000s, following research by Fitz students in collaboration with the Royal Society for the Protection of Birds (RSPB) at Gough Island. Since then, they have been found to attack seabirds on Marion Island, and plans are underway to try to eradicate the species at both islands.
Activities in 2018
- Peter Ryan accompanied New Zealand expert Keith Springer and BirdLife SA’s Andrea Angel to Marion Island in April-May 2018 to prepare for the planned mouse eradication on Marion Island. Keith produced draft project and operational plans for the eradication, building on John Parkes’ feasibility report drafted in 2014. Peter and Andrea conducted bait uptake trials to demonstrate that all mice will eat bait, including cave trials to ensure mice in caves are reached by aerial baiting. Andrea also set up husbandry trials to assess the feasibility of taking Lesser Sheathbills Chionis minor into captivity.
- Autumn surveys were conducted for the fourth successive year to monitor the spread of mouse attacks on large chicks of Grey-headed Thalassarche chrysostoma and sooty albatrosses Phoebetria spp. at Marion Island.
- Marion Island’s Environmental Conservation Officer (ECO) Charlotte Heijnes was trained to conduct various studies, including assessing the start and end of mouse breeding across an altitudinal gradient, bait preference and toxicity trials, and monitoring cloud heights through the proposed winter baiting window. In late May 2018 she was joined by a secondECO, Monica Leitner. Together they repeated toxicity trials for mice on Marion Island and found that all mice died even at relatively low doses of brodifacoum, suggesting that the unexpected results obtained in 2017 were a result of the diet being fed to the mice in the lab. They also ran a series of husbandry trials with caged sheathbills, which suggest that it will be very challenging to keep a large number of captive sheathbills during an eradication attempt.
- Ben Dilley and Delia Davies completed their second field season on Nightingale Island in early 2018 as part of an EU-BEST project awarded to Tristan Conservation to collect basic biology information on the Endangered Wilkins’ Bunting Nesospiza wilkinsi. Ben returned to Nightingale in September 2018 to obtain a third year of re-sighting data which will allow survival estimates to be made for the two cohorts of chicks banded in 2016/17 and 2017/18.
- Peter Ryan led a three-month trip to Inaccessible Island from September to December 2018 to continue his decadal monitoring of the island’s birds. which commenced in the late 1980s. He was accompanied for the first three weeks by Maëlle Connan (NMU), and for the rest of the visit by PhD student Ben Dilley. On the trip to Tristan, they were able to advise the RSPB team heading to Gough, which included Dr Stefan Oppel, who has taken over the lead on research for the RSPB at Gough, and the contingent sent to prepare for the mouse eradication in 2020.
- The most worrying development on Inaccessible Island since Peter’s last visit in 2011 was the ongoing spread and rapid increase in impact of the introduced Soft Brown Scale Coccus hesperidum and itsassociated sooty mould Seiridium phylicae on Phylica arborea trees. The fruit of these trees are crucial for the large-billed buntings on Inaccessible and Nightingale Islands. In 2018, fruit loads in the worst affected area were barely 20% of those found on unaffected trees, and many large trees had died. Only two male large-billed birds remained in this area, both apparently mated to small-billed females. It appears that the scale insect invasion is breaking down the ecological segregation among bunting morphs in this area. This is of grave concern for Wilkins’ Bunting Nesospiza wilkinsi on Nightingale Island, which has a total population of only around 400 individuals. In 2017/18, Ben and Delia found that Soft Brown Scale had spread throughout most of Nightingale Island, and urgent steps are being taken to explore the viability of using tiny parasitic wasps to control scale insect populations on both islands.
- Ben Dilley completed his PhD on the impacts of mice on seabirds at Marion and Gough Islands.
- At the end of 2018, the RSPB finally appointed an operations manager for the project to eradicate mice from Gough Island in 2020. The project will be supported logistically by the South African Department of Environmental Affairs (DEA).
- Less good news is the fact that Sagina procumbens control/eradication operations were scaled back on Gough Island, despite the apparent success of spraying with a herbicide cocktail. Hopefully this decision will be re-evaluated after the mouse eradication, depending on the rate of spread of Sagina over the intervening two years.
- More worrying news is that Chris Jones and Michelle Risi observed the first evidence of mice attacking an adult Northern Giant Petrel on Marion Island in 2017, and Jaimie Cleeland and the RSPB team on Gough recorded the first mouse attack on an adult Tristan Albatross Diomedea dabbenena at Gough Island in early 2018. The implications of these records were discussed in a paper in Antarctic Science.
- The June 2018 issue of National Geographic included an article on seabirds featuring the impacts of mice on Marion Island’s seabirds. Peter Ryan and Ross Wanless obtained a US $125,000 grant to assist with planning for the Marion eradication attempt.
- PhD student Stefan Schoombie led on a paper on Avian Pox in seabirds on Marion Island that was published in Antarctic Science, and Ben Dilley’s paper reporting how mice are causing low breeding success among burrowing petrels on Marion Island also appeared in Antarctic Science in 2018.
- Peter Ryan contributed to a paper in PLoS ONE, published in early 2019, identifying priority islands for restoration through eradication of introduced predators, led by Nic Holmes from Island Conservation.
Agreement on the Conservation of Albatrosses and Petrels; BirdLife International; DST-NRF CoE grant; EU-BEST; Royal Society for the Protection of Birds; South African National Antarctic Programme; UK Overseas Territories Environment Programme.
Prof. Peter Ryan (FIAO, UCT)
Dr Alex Bond (formerly at the RSPB)
Dr Richard Cuthbert (formerly at the RSPB)
Trevor Glass (Tristan Conservation Department)
Dr Stefam P[[e; (RSPB)
Dr Ross Wanless (FIAO, UCT and BLSA)
Student: Ben Dilley (PhD).
Research assistants: Jaimie Cleeland, Kate Lawrence and Fabrice Lebouard (Gough 2017/18), Chris Jones, Michelle Risi and Alexis Osborne (Gough 1018/19) and Delia Davies (Nightingale).