Conservation work on Inaccessible Island
- Tristan Science - Research and conservation activities at Inaccessible Island
Submitted by Tristan Times (Sarah Glass) 19.12.2009
Peter Ryan & Rob Ronconi tell us about valuable research on Inaccessible Island.
We visited Inaccessible Island for two months in October-December 2009 to tackle a number of conservation, monitoring and research questions. For Peter Ryan, it was his tenth visit to the island, while for Rob Ronconi it was his first chance to see where the Great Shearwaters he studies off the Canadian east coast breed. After spending three weeks on Gough Island, we were landed at Blenden Hall by the helicopter from the SA Agulhas. The hut was in fine shape, and with new batteries installed for the two solar panels we were soon settled in and ready to work. Our first task was to check the litter on the beaches, repeating surveys dating back to 1984. Not surprisingly the amount of litter washing up has increased, with some types of litter (such as plastic bottles and shoes) increasing faster than others. As before, most comes from South America, followed by oriental countries (presumably from their large fishing fleets operating in the South Atlantic). We also checked the amount of plastic eaten by seabirds by examining the pellets regurgitated by Skuas (Seahens). Compared to previous years, there was a marked increase in plastic.
Our next job was to tackle the flax on Pig Beach Hill, which was missed when the flax team in 2007 was stranded on Nightingale. This turned out to be a bigger job than anticipated. On our first visit we killed 20 or so plants, but found several more we didn't have time to deal with. Then when we returned, we found some more, so what should have been an easy day became another epic. And then, when we thought we'd got them all, we spotted a few more plants further up Waterfall Valley, which necessitated another visit, and the discovery of yet more plants, including one on the south side of Pig Beach Hill, overlooking Harold's Plain. In the end we spent 4 days flaxing (not counting commuting days to the camp at Denstone Hill), but we are now confident that few if any remain on the plateau.
We also repeated surveys of alien plants around the island to check whether their ranges are increasing. If nothing else, this is a great excuse to explore the island. We found few changes in alien plants, although two new species were discovered. Both were localised, and so measures were taken to eradicate them from the island. The alien plant surveys also improved our knowledge of some of the native species. For example, Pepper Trees Peperomia beteroana and the scarce grass Agrostis trachylaena were found along the Twin Falls river above Cove Rock. Both species previously were thought to be confined to the Waterfall Valley. The Nightingale Brassbuttons Cotula moseleyi is now common along the scarp edge between North Point and the East Road, suggesting it is a relatively recent arrival from Nightingale Island.
The other big task started in October was the census of Spectacled Petrels or Ringeyes. This repeated surveys made in 1999 and 2004, and showed that Ringeye numbers continue to increase. We estimate at least 15,000 pairs now breed on the island, compared to perhaps 10,000 pairs five years ago. Unfortunately, repeat counts of Mollies and Sooties were less encouraging, with both species of albatross having decreased by about 10% since 2004. In November, the Great Shearwaters returned and Rob got stuck into monitoring a series of burrows around the hut at Blenden Hall, while Peter spent most of his time chasing buntings around Denstone Hill. At times we felt like the Stoltenhoff brothers, with one on top of the island and the other at the bottom! However, we did get together to deploy satellite tags onto Sooty Albatrosses, Ringeyes and Great Shearwaters as part of a project funded by BirdLife International to better understand the at-sea movements of seabirds threatened by longlining and other fishing activities. Rob also put small depth recorders onto a few Great Shearwaters. Although on most days they seldom dive to more than 10 metres, the record dive was to 17 metres! We also checked the diet of breeding Skuas around the island, and were able to confirm breeding by Great-winged Petrels when we found a large chick in a Skua midden on Harold's Plain.
Despite the discovery of a few new alien plants on the island (which we immediately attempted to eradicate), Inaccessible remains in good condition from a conservation perspective. We thoroughly enjoyed our visit, and thank the Island Council and Administrator for approving it. We are especially grateful to the captain and crew of the Edinburgh and Tristan Conservation's Norman Glass for getting us safely off the island on 1 December, and for our subsequent visits to Nightingale, Alex and Stoltenhoff, where we were able to do some more alien plant control work.
Peter Ryan & Rob Ronconi
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"Alex" refers to Alex Island, sometimes called Middle Island, located just north of Nightingale.