Cousin is a beautiful, small island (27 ha) situated less than 2 km west of Praslin. The site also includes c.105 ha coastal marine habitat. Its large plateau extends over most of the island and is covered with indigenous mature woodland dominated by Pisonia grandis, Morinda citrifolia and Ochrosia oppositifolia. It is almost encircled by a long sandy beach (the shape and width of which changes with each monsoon) with tall Casuarina equisetifolia and Cocos nucifera trees. The southern coast of the island is, however, rocky. A hill, rising to 69 m, occupies the centre of the southern half of the island. It is dominated by bare rock and boulders, low woodland and Pandanus balfourii, Ficus reflexa, F. lutea, Euphorbia pyrifolia shrubs, tall herbs and ferns. An area of mangrove and small, temporary freshwater pools are also found. Cousin was formerly a coconut plantation, but most of the trees have now been cut down. Nature conservation, research and ecotourism (day visits, confined to main paths only) are the only human activities (plus some limited fishing by the staff). The reserve funds itself through ecotourism. A marine park, extending 400 m into the sea, hosts pristine coral reefs.
See Box and Table 2 for key species. This IBA is one of the sites of highest ornithological interest in Seychelles. It used to be the last refuge of Acrocephalus sechellensis, with 26–29 individuals surviving in 1959. After conservation efforts and the population’s recovery, birds were translocated from here to two other islands. In 1999 the population on Cousin was 353 birds with 104 occupied territories. Cousin is also one of the only four islands hosting Foudia sechellarum, with 800–1,200 birds in 1997. A small breeding population of Copsychus sechellarum was established in 1995, when three pairs were translocated from Frégate; in 1997 the population had risen to 25 birds with four occupied territories. Two other more common endemics, Nectarinia dussumieri (c.250 birds) and Alectroenas pulcherrima (a few birds only) are also found, as well as the interbred Streptopelia picturata picturata x rostrata, (50–100 individuals, with some showing characteristics of the endemic subspecies). A large colony of seabirds, dominated by Anous tenuirostris, is present from May to September. Smaller numbers of Anous stolidus (1,300 pairs) also breed during the south-east monsoon. Gygis alba, Phaethon lepturus and Sterna anaethetus (c.600 nests) breed all year-round. During the north-west monsoon, the hill supports an important breeding colony of Puffinus pacificus whereas P. lherminieri (c.1,000–1,500 pairs) nests all year-round, on the plateau. Several hundreds of both Fregata ariel and F. minor can be seen soaring or roosting in trees. A few waders are also present year-round, the commonest being Arenaria interpres (50–100 birds). Gallinula chloropus (10–20 pairs) and Butorides striatus (1–2 pairs) also breed on the island.
Non-bird biodiversity: There are three species of skink, Mabuya wrightii, M. seychellensis and Pamelascincus gardineri and two geckos, Phelsuma astriata, Ailuronyx sechellensis; all endemics. A small population of the rare terrapin Pelusios subniger and 12 individuals of the giant tortoise Dipsochelys dussumieri are also present. It is also an important nesting site for the turtles Eretmochelys imbricata (CR) and, occasionally, Chelonia mydas (EN).
BirdLife International (2019) Important Bird Areas factsheet: Cousin Island Special Reserve. Downloaded from http://www.birdlife.org on 16/01/2019.