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Meeting report – Tropical forests and islands

BOU 1998 annual conference, University of Edinburgh
by Juliet Vickery

The BOU's 1998 annual conference in Edinburgh, “Tropical Forests and Islands” focused on two habitats which, where they occur together, represent among the most threatened in the world. The degree of threat was all too apparent from talks that swept across the oceans of south East Asia, India, the Atlantic and the Caribbean. In Indonesia it is predicted that, by 2010, all forest outside nature reserves and below 1000m will be selectively logged. In Mauritius, 750 introduced plants now compete with only 650 native species and in the Cayman Islands 85 per cent of land without a house already is up for sale. Many of these islands support unique species and it is difficult to exaggerate the seriousness of the threat to biodiversity, in general, and birds in particular. Malaku Province, Indonesia, is home to over 90 species of birds of which 76 are restricted to single islands. Forty per cent of the birds on Sao Tome, Gulf of Guinea, are endemic and the Seychelles and Lesser Antilles have 12 and 11 endemic birds respectively.

The attraction to scientists of these remote specks of land derives from a combination of their uniqueness and the challenge of their inaccessibility but, as Michael Poulsen (BirdLife International) illustrated, a challenge that usually pays off. The BOU-funded expedition to Malaku Province had to make two attempts to reach the, hitherto unconquered, 2200m mountain summit of Buru, one of the five main islands of the Province. Though they successfully reached 1800m and this was enough to yield sightings of the Rufous Throated White-eye Madanga ruficollis at 1540m – a species not seen for 70 years.

The processes by which these remote islands “acquire” their flora and fauna has always fascinated scientists. For example, have species colonised archipelagos by island-hopping along the chain or reaching islands independently from the mainland? Peter Jones (University of Edinburgh) considered the evidence for these two processes for birds in the Gulf of Guinea. The very low level of species sharing between Bioko, the island closest to mainland Africa, and the more distant islands suggest independent colonisation. However, the picture is complicated by the fact that sea level rise 10,000 years ago almost rendered Principe a missing link in the chain, reducing its size from 1179km2 to 128km2 and almost certainly resulting in the loss of part of its avifauna. Single isolated islands provide much simpler systems than archipelagos in which to study island biogeography a point highlighted by Philip Ashmole's (University of Edinburgh) work on St Helena and Ascension. These are among the most isolated islands in the world, they are volcanic, and so have always been isolated, are relatively simple geologically and have been colonised by species almost entirely through winds and currents from the southeast. However, while St Helena is around 14 million years old, Ascension is only about 1.5 million years old and may provide a snap shot of St Helena's past. For example, whilst both islands are estimated to have been colonised by approximately 30 species of spider these have speciated into 46 endemic species (12 endemic genera) on St Helena compared with only 4 on the younger Ascension.

The major threats to these islands are usually considered to be habitat destruction and the introduction of exotic species. However, a fascinating study of the Mauritius Fody Foudia rubra by Roger Safford (University of London) graphically illustrated the danger of automatically adopting the view “native equals good, foreign equals bad”. This endemic bird species relies heavily on groves of introduced Japanese Red Cedar Cryptomeria japonica within native woodland for successful nesting. Nutritionally poor foliage and extremely sticky resin, makes this introduced tree highly unattractive to mammals such as rats and mongoose; mammals frequently predate Fody nests in native trees so Cryptomeria provides breeding birds with a safe haven. In addition to human-related threats, isolated island populations are extremely vulnerable to stochastic events as Peter Evans (University of Oxford) highlighted from research on Dominica, Lesser Antilles. Two hurricanes, in 1979 and 1980, wiped out the remnant population of Imperial Parrots Amazona imperialis in the south of Dominica now confined to the central mountain massif of Morne Diablotin.

The uniqueness of many island species also makes them attractive to the pet trade, something that may underlie the decline of many of the 36 parrot species of Wallacea, Indonesia. Stuart Marsden (Manchester Metropolitan University) reported on a long term research aimed at determining sustainable levels of exploitation of some of these parrot species. Information about the current level of the trade and estimates of population sizes of parrot species, derived from field surveys and land use maps, suggest that harvest levels of around 17 % are unsustainable for species such as the White Cockatoo Cacatua alba whereas much lower levels of harvesting (<5 %) have very little effect on species such as the Tanimbar Corella Cacatua goffini.

Ultimately the value of detailed research on these islands lies in the legacy it leaves not only in terms of healthy wildlife populations but also in enabling local people to continue the conservation work. The Malaku project has involved training Indonesians in bird census techniques and skills required to raise public awareness of conservation issues. In Dominica, detailed ecological understanding of behaviour and distribution of a range of taxonomic groups has made it possible to consider ways of developing carefully controlled nature tourism to boost the island's struggling economies without endangering its wildlife.

St Helena stands as a sad monument to our past carelessness and ignorance. Biologically, this is probably the most devastated island in the world. Five landbirds went extinct so quickly after colonisation in the 1500s that no equivocal records exists of living specimens. Real hope that, where scientists work with local people to raise commitment and belief in the value of their wildlife, a species fate can be turned around comes from the Seychelles (Geoff Watson, Scottish Natural Heritage). Here the Seychelles Magpie Robin Copsychus sechellensis and Seychelles Brush Warbler Bebrornis sechellensis have, literally, been rescued from the brink of extinction – the latter, down to 20 individuals in 1968 is now around 2000. Research such as that presented at this conference provides hope that St Helena's history will not repeat itself on other biological treasure islands.

The BOU was delighted to welcome Jared Diamond (University of California) who gave a fascinating Alfred Newton Lecture focussing on his work on the soil eating habits of the Eclectus Parrots Eclectus roratus and Sulphur-crested Cockatoos Cacatua galerita at land slide sites in the forests of New Guinea. The usual explanations for such behaviour are that birds are seeking grit to grind food, essential minerals that are rare in the diet or a buffer to counteract acids which cause indigestion. However the soil in question was too fine to be of any use for grinding, too low in minerals to be a dietary supplement and had lower buffering capacity than distilled water. Instead it seems the parrots' quest for soil is related to the toxicity of their diet. The birds feed largely on seeds – high in lipids and proteins but also in toxins such as strychnine and quinine. The soil binds these chemicals, preventing them being absorbed through the gut wall and effectively detoxifying the food.

Away from the lecture theatre, conference goers were well fed and watered and had an array of displays, poster presentations and of course the BOU shop to occupy what little free time they had left. Saturday evenings lavish conference dinner was preceded by a reception to mark the publication of the latest BOU Checklist, The Birds of St Helena. The launch was honoured to have present three of the five authors - Neil McCulloch, Trevor Trueman and principal author, Beau Rowlands. The two missing authors, Stors Olson and the late Richard Brooke, were toasted by those present, on their collective achievement.

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