The Granitic Seychelles are in the north-east of a larger archipelago which includes a chain of low-lying coralline islands (see Aldabra, EBA 099). The inner islands were once part of the ancient landmass of Gondwanaland, and are the world's only isolated granite islands, all other oceanic islands being limestone or volcanic. The largest island is Mahé (154 km²), which rises to 914 m on Morne Sechellois, the highest point in the group.

The native vegetation of the Granitic Seychelles before settlement was probably closed broadleaved forest, which can be divided into lowland rain forest (long since disappeared), dry forest (including the palm forests of Praslin and Curieuse where the famous coco de mer palm Lodoicea maldivica survives), and moist forest at high altitudes (e.g. on Mahé and Silhouette). Vegetation on the lower granitic islands (e.g. Frégate, Aride and Cousin) is scrubby (but includes important stands of native trees) and has more in common with the coralline islands (Procter 1984).

The endemic birds are all forest species, and several are able to use secondary forest and plantations. Distribution between islands appears patchy (see 'Distribution patterns table', below) as several of the multi-island species have become extinct on at least one island (although some have been reintroduced). Today only two species are confined to single islands: Otus insularis on Mahé and Terpsiphone corvina on La Digue.

The EBA also holds two endemic subspecies of particular note: Black Parrot Coracopsis nigra barklyi, the national bird of the Seychelles, which is confined to palm forest on Praslin, with a few birds also on Curieuse; and Seychelles Turtle-dove Streptopelia picturata rostrata, which has interbred with the introduced nominate race from Madagascar such that only a very few individuals showing characteristics of true rostrata survive, with examples on Cousin, Cousine, Frégate and Bird Island (to the north of the EBA).

The lowland forests of this EBA were cleared by early settlers for timber, for spice and later coconut plantations, and for firewood to fuel the cinnamon distilleries. Today pockets of near-natural forest remain only at higher altitudes in the more inaccessible central areas but these often contain exotic species. Not surprisingly the islands have suffered many extinctions including the loss of two bird taxa, Psittacula wardi and Zosterops mayottensis semiflava, and at least 41% of their island populations of birds (Diamond 1984). Habitat alteration and predation by introduced cats and rats (especially black rat Rattus rattus) are the likely causes of most such extinctions, and these factors continue to be major threats. Frégate, Aride, Cousin and Cousine are the only islands to have remained rat-free (but see below) and have therefore been vitally important refuges. In 1995 it was discovered that Frégate had been invaded by brown rats R. norvegicus via boat cargo and, although a poisoning and trapping programme is under way, total eradication is unlikely unless substantial additional funding is obtained (McCulloch 1996).

Introduced predators (e.g. rats and Common Mynah Acridotheres tristis) and habitat destruction continue to pose a serious threat to the species with tiny ranges. Thus, on Mahé, Zosterops modestus is confined to three tiny rural and residential areas (totalling less than 5 km²) and may number just 5-6 pairs (25-30 individuals) (Rocamora et al. in press), although these white-eyes have recently been discovered on Conception (L. Chong-Seng per G. Rocamora in litt. 1997), a small island c.2 km from Mahé; this population is being censused and hosts at least eight more pairs, though the total world population of this species is still probably under 100 birds (G. Rocamora in litt. 1997). Also on Mahé, Otus insularis is recorded only from forest (virtually all secondary) at 250-600 m with a population of perhaps 80 pairs. On La Digue, Terpsiphone corvina inhabits mature stands of trees (estimated to cover 41 km² in 1992) and numbers c.70 territorial pairs, habitat destruction for housing development being the main problem (Rocamora et al. 1997).

On Aride, where a single female Foudia sechellarum has become established within a population of introduced Madagascar Red Fody F. madagascariensis, there is concern that hybridization between the two species could endanger any future of F. sechellarum on Aride and, in the longer term, on neighbouring islands (Lucking 1997).

Specific conservation efforts, including several years of research and species/habitat management by BirdLife International, have been directed in particular towards two of the highly threatened species, Copsychus seychellarum and Acrocephalus sechellensis. As a result the population of C. seychellarum on Frégate has risen from 12 individuals in 1965 to 42 in 1996, with additional translocated birds on Cousine (six birds), Aride (one surviving out of six) and Cousin (six, which have produced 11 additional young) (Watson et al. 1992, R. Lucking per G. Rocamora verbally 1996; see also McCulloch 1996). The population of A. sechellensis on Cousin has risen from c.30 birds in 1965 to c.350 in the 1990s, when subsequent monitoring showed that this represented the carrying capacity for the island, and thus permitted a translocation programme to Aride (1,000+ birds in 1996) and Cousine (80 birds in March 1994) (Komdeur et al. 1991, Komdeur 1994, Cuthbert and Denny 1995, A. Skerrett in litt. 1996). A specific project to save Zosterops modestus from extinction has recently been proposed by BirdLife International in collaboration with the Division of the Environment.

There are several protected areas in this EBA, namely the Morne Seychellois National Park (30 km²) on Mahé, the Praslin National Park (3.4 km²) which includes the Vallée de Mai National Park (a World Heritage Site, 0.2 km²) on Praslin, Aride Special Reserve (0.6 km²), Cousin Special Reserve (0.3 km²), La Veuve Special Reserve (0.1 km²) on La Digue which protects some habitat for Terpsiphone corvina, Curieuse National Park (15 km²) which covers both the island and surrounding sea, and three islets, Ile Seche, Vache Marine and Les Mamelles, originally established to protect seabird nesting sites.

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Granitic Seychelles. Downloaded from https://datazone.birdlife.org/eba/factsheet/106 on 23/11/2024.