|Location||Mauritius, Outer Islets|
|Central coordinates||57o 48.00' East 19o 49.00' South|
|IBA criteria||A4i, A4iii|
|Altitude||0 - 162m|
|Year of IBA assessment||2001|
Site description Serpent Island is the most remote and inaccessible of the five northern islets of Mauritius (area given as 19 ha in some publications). The islet is in the shape of a dome (162 m high) with a circular base and extremely steep slopes. The lower slopes are marked by hollows, overhangs and ledges, with low cliffs around the shore, whereas the upper slopes are relatively smooth. Vegetation is almost absent; the three plant species recorded are all rare, although common elsewhere. A thin coating of guano covers the rock surface. Landing is extremely difficult. As on Round Island, exotic rodents have never become established. However, a vast colony of surface-nesting seabirds covers the whole islet and this, combined with the near-absence of vegetation, gives Serpent Island a totally different character. It has an ecosystem of vertebrates and invertebrates, many perhaps endemic to the islet, most living independently of any vegetation.
Key Biodiversity See box for key species. The seabird colony consists mainly of terns (Sterninae). Populations are very large (estimated totals up to 850,000 pairs), but have never been reliably censused. Around 50 pairs of Sula dactylatra (of the scarce Indian Ocean race melanops) are also present. Unusually for the region, Anous tenuirostris nests on the ground. Pterodroma arminjoniana visits from nearby Round Island, but has not been proven to breed. Phaethon rubricauda formerly bred and may still do so occasionally. The island has no potential for landbirds.
Non-bird biodiversity: Reptiles: Nactus serpensinsula (VU) (islet-endemic subspecies; species otherwise occurs only on Round Island), Gongylomorphus bojerii (possibly islet-endemic subspecies). Arachnids: undescribed lizard-eating tarantula Pterinochilus sp. (Theraphosidae). Other islet-endemic invertebrates likely to be found.
|Species||Season||Period||Population estimate||Quality of estimate||IBA Criteria||IUCN Category|
|Sooty Tern Onychoprion fuscatus||breeding||-||250,000-500,000 breeding pairs||-||A4i||Least Concern|
|Brown Noddy Anous stolidus||breeding||-||10,000-100,000 breeding pairs||-||A4i||Least Concern|
|Lesser Noddy Anous tenuirostris||breeding||-||10,000-100,000 breeding pairs||-||A4i||Least Concern|
|A4iii Species group - seabirds||breeding||-||1,000,000-2,499,999 individuals||unknown||A4iii|
|Protected area||Designation||Area (ha)||Relationship with IBA||Overlap with IBA (ha)|
|Ile aux Serpents||Nature Reserve||31||is identical to site||31|
|Land-use||Extent (% of site)|
|nature conservation and research||-|
References Bell et al. (1994), Lloyd (1846), Newton (1960), Safford (1993b), Vinson (1950, 1953).
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Recommended citation BirdLife International (2015) Important Bird Areas factsheet: Serpent Island. Downloaded from http://www.birdlife.org on 27/04/2015
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