Important Bird Areas the British Indian Ocean Territory Peter Carr

Important Bird Areas The British Indian Ocean Territory Peter Carr Abstract The Chagos Archipelago, which has been known as the British Indian Ocean Territory since 1965, holds 18 species of breeding seabirds, many of them in internationally important numbers. The entire area, with the exception of Diego Garcia and its immediate surrounding waters, was designated a Marine Protected Area (MPA) in 2010, the largest MPA declared in the world so far. This UK Overseas Territory also hosts a Ramsar site based upon Diego Garcia, as well as ten Important Bird Areas (IBAs). Recent research has shown that a further two sites deserve IBA status. All of these sites have been designated IBAs for their breeding numbers or congregations of seabirds. There is a paucity of landbirds and no endemics. Human influence on the avian populations of the archipelago has been catastrophic. There is evidence of immense seabird colonies at one time but these had all disappeared by the late nineteenth century. Introduced Black Rats Rattus rattus continue to suppress numbers of breeding birds in most islands of the archipelago, while conversion of native forests to coconut Cocos nucifera plantations has deleteriously altered the terrestrial environment of most islands. There is evidence that a small recovery of breeding seabird numbers is taking place on some islands, though much more research is needed. Returning many of the islands to a rat-free, coconut- managed state, which could assist seabird recovery, is a matter of funding and political will, rather than a ‘green dream’. ying at the southern end of the Lakshadweep–Maldives– LChagos ridge and approxi- mately in the centre of the Indian Ocean, over 2,000 km from Africa, Indonesia and mainland Asia, are the five atolls of the Chagos Archipelago. Comprising some 55 islands, they are found between 05°15’S to 07°27’S (240 km, north to south) and 71°15’E to 72°30’E (140 km east Fig. 1. The British Indian Ocean Territory. to west). The archipelago has the Great Chagos 642 © British Birds 104 • November 2011 • 642–659 The British Indian Ocean Territory Bank at its centre, the world’s largest atoll. This Banhos are 3,751 mm/year and 3,999 mm/ is mostly underwater, though there are seven year respectively. Rain falls mainly between islands on its western rim and one island on October and April, when the winds are light the northern edge. To the north of the Great to moderate and generally from the north- Chagos Bank lie the atolls of Peros Banhos and west. Between December and February, the Salomon; to the southwest is Egmont; and to Inter-Tropical Convergence Zone (ITCZ) is the south the largest island, and the only over or just south of Chagos, before it moves inhabited atoll, that of Diego Garcia. Young in north. For the rest of the year, the southeast geological terms, being some 2,000–5,000 years trades blow strongly and there is less rain old (Topp & Sheppard 1999), and low-lying during this period. The low latitude of (the vast majority of all islands bar Diego Chagos means that developing tropical Garcia are below 3 m above sea level), the Ter- cyclones are weak, the maximum wind speed ritory extends over a total area of around recorded being a peak gust of 120 km/hr in 60,000 km2, yet only a tiny fraction of this, 1984 (Topp & Sheppard 1999). about 60 km2, appears above the surface of the ocean (Eisenhauer et al. 1999). A brief history of the British Indian Ocean Territory Climate The Chagos Archipelago was thought to have The Chagos Archipelago has a typical trop- been first discovered by a Portuguese captain ical maritime climate. The average tempera- named Pedro Mascarenhas in 1512, but the ture on Diego Garcia is 27°C and the average initial settlers were French and landed on maximum and minimum are 29°C and 25°C Diego Garcia around 1785. They were dis- respectively (FCO 1993). The average rainfall placed by a British East India Company on Diego Garcia is 2,599 mm/year, but the colonising expedition in April 1786. This northern atolls are the wettest in the Indian venture was short-lived and by October of Ocean – the averages on Salomon and Peros the same year the expedition departed, to be Andy Williams Andy 345. North Brother, one of the IBAs of the British Indian Ocean Territory, in July 2009. This unusual island has cliffs of up to 5 m high and holds breeding populations of both Audubon’s Puffinus lherminieri and Wedge-tailed Shearwaters P. pacificus, as well as 650 pairs of Brown Booby Sula leucogaster during the most recent survey, in July/August 2009. The BIOT Patrol Vessel can be seen offshore. British Birds 104 • November 2011 • 642–659 643 Carr ownership of the archipelago changed hands, coconut-plantation life continued, pros- pered and expanded out to all the other atolls of the archipelago from its initial base on Diego Garcia. This industry eventually declined in the Chagos in the 1900s, probably because of the competition from palm oil that was grown Janet Prushansky on the mainland at lower 346. Resurgent Island, July 2009. costs. replaced later that decade by lepers from From 1814, the archipelago was adminis- Mauritius, who were marooned on the island tered from Mauritius. This changed in 1965, by the French. By 1793, the French had estab- when the British Indian Ocean Territory lished a colony on Diego Garcia using an (BIOT) was formed, prior to Mauritian inde- economy based on exportation of coconuts pendence in 1968. The original BIOT to Mauritius, these being harvested by a included the Chagos, Aldabra, Desroches and labour force of slaves originating from East Farquhar Archipelagos. However, Aldabra, Africa and Madagascar. The British captured Desroches and Farquhar became part of the Mauritius and Réunion in 1810, during the Republic of Seychelles when it became inde- Napoleonic Wars. Under the Treaty of Paris pendent in 1976. The Chagos remained as in 1814, Réunion was restored to France, and BIOT and, following an Exchange of Notes Mauritius and its dependencies, including between the UK and the USA in 1966, all the the Seychelles and the Chagos Archipelago, islands were given over to defence purposes were ceded to Britain. While the national for an initial period of 50 years. It was announced in 1970 that a British/American communica- tions facility was to be con- structed on Diego Garcia, and this became operational in 1973 (FCO 1993). The start of construction of the military facility on Diego Garcia her- alded the removal of the last of the plantation workers, first from Diego Garcia, in 1971, and from the outer islands by 1974. Diego Garcia has been developed for military purposes several more times in the 40-odd years since the first construction workers landed on the island and, at the time of writing, is a full Naval Support Facility that is capable of sup- porting air-force activities. No other island in the archipelago has been developed and all Janet Prushansky 347. The Striated Heron Butorides striata is a natural colonist, have remained free of perma- which occurs throughout the British Indian Ocean Territory; nent inhabitants since at least Diego Garcia, November 2009. 1974. 644 British Birds 104 • November 2011 • 642–659 The British Indian Ocean Territory The historical impact of humans tion and export. These native trees, chiefly on the British Indian Ocean Calophyllum inophyllum, Barringtonia asi- Territory atica, Cordia subcordata and Pisonia grandis, Very few of the islands have remained all provided nesting platforms for seabirds, unscathed by the impact of human settle- especially Red-footed Boobies Sula sula and ment. Guano was mined for fertiliser and Lesser Noddies Anous tenuirostris. They were then shipped abroad from Diego Garcia (Edis replaced by a monoculture of coconut stands 1993). These deposits probably arose from that did not offer the same breeding oppor- the terns, boobies and frigatebirds that, tunities for seabirds, because of the lack of according to the naturalist G. C. Bourne, protruding boughs and branches to provide were ‘breeding in countless numbers’ in Sep- nesting platforms. tember 1885 (Bourne 1886). The huge Only islands that were too difficult to numbers of seabirds reported by Bourne had farm for coconuts have remained relatively all but disappeared from Diego Garcia by the environmentally unscarred and, amazingly, early 1900s and the same pattern is very likely some have also remained rat-free. These to have been replicated on all the other atolls. islands – all of the Great Chagos Bank The cause of catastrophic declines in islands, with the exception of the once- breeding seabirds is the familiar oceanic- inhabited Eagle Island (the second-largest island tale of unfettered harvesting of birds island in the Chagos), six islands in northeast and eggs by humans combined with the Peros Banhos, and three small islands in introduction of alien animals. In the Chagos Diego Garcia – offer a view of what the Archipelago, these consisted, at various times habitat must have looked like before the in the islands’ history, of sheep, cattle, horses arrival of humans. These islands are each and donkeys, together with (and having the unique, with differing vegetation zones and greatest impact on birds) dogs, pigs, cats and associations. The islands that have sandy Black Rats Rattus rattus (Edis 1993). beaches generally have a beach crest of At the same time as the introduction of Scaevola taccada interspersed with Argusia alien predators came the environmental and (Tournefortia) argentea, coconut and occa- ecological traumas associated with the sionally Morinda citrifolia and Guettarda destruction of the native hardwood stands, speciosa.

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