|Location||St Helena (to UK), Tristan da Cunha|
|Central coordinates||12o 18.00' West 37o 6.00' South|
|IBA criteria||A1, A2, A4i, A4ii, A4iii|
|Altitude||0 - 2,060m|
|Year of IBA assessment||2004|
Site description The site comprises the whole of Tristan Island, as described in the ‘General introduction’.
Key Biodiversity See Box and Table 2 for key species. Although as many as 56 bird taxa have been recorded, there are now only 13 known species of breeding seabirds and two species of resident landbirds. The seabirds include Eudyptes chrysocome moseleyi, Diomedea chlororhynchos, Phoebetria fusca, Pterodroma macroptera, P. mollis, P. incerta, Pachyptila vittata, Procellaria cinerea, Puffinus gravis, P. griseus, Catharacta antarctica, Sterna vittata and Anous stolidus. Tristan is the only known breeding site within the group for Pterodroma incerta and of Puffinus griseus, while numbers of Diomedea chlororhynchos are the highest for any island in the Dependency. Pterodroma brevirostris and Puffinus assimilis may also breed. Pterodroma macroptera, P. incerta and Procellaria cinerea have not been proven to breed elsewhere in the Tristan group, possibly because they are winter breeders. There are currently an estimated 40,000 breeding pairs of seabirds, most known from the south-eastern quadrant, which has suffered least from human disturbance. The estimated breeding density is only 500 pairs per km². The terrestrial species include the restricted-range Gallinula comeri, introduced from Gough Island (SH008) in 1956 (3,000 pairs, 1993 estimate), and Nesocichla e. eremita, confined to this island and numbering 40–60 pairs in 1974.There are more records of non-breeding visitors and vagrants on Tristan than from the other islands of the group. This is probably due to the island’s larger size and permanent human presence. Also, due to persecution, there are fewer Catharacta to prey upon them as they arrive. Most records are from the settlement area. Seabirds include Diomedea exulans, D. melanophris, Macronectes giganteus, M. halli, Fulmarus glacialoides, Daption capense, Procellaria a. aequinoctialis, P. a. conspicillata, Puffinus gravis, Oceanites oceanicus, Pelagodroma marina and Larus dominicanus. Shorebirds and landbirds include Casmerodius albus, Egretta thula, Bubulcus ibis, Porphyrula martinica, Calidris fuscicollis and Hirundo rustica. The strong westerlies create favourable conditions for a crossing from South America, and this would explain the presence of gallinules and other non-breeding landbirds that have reached Tristan from that continent. The site requires much further field study, especially the southern side.
Non-bird biodiversity: There are no endemic mammals. The only breeding native mammal is the fur seal Arctocephalus tropicalis, of which there is a small colony at Cave Point on the southern side of the island. Elephant seals Mirounga leonina haul out regularly on Tristan beaches and breed sporadically. Eubalaena glacialis (EN) occurs in offshore waters between September and November, but in very low numbers. Of 62 native terrestrial invertebrates recorded, only four are endemic.
|Species||Season||Period||Population estimate||Quality of estimate||IBA Criteria||IUCN Category|
|Northern Rockhopper Penguin Eudyptes moseleyi||breeding||2004||3,860 breeding pairs||-||A1, A4ii||Endangered|
|Sooty Albatross Phoebetria fusca||breeding||1974||2,000-3,000 breeding pairs||-||A1, A4ii||Endangered|
|Atlantic Yellow-nosed Albatross Thalassarche chlororhynchos||breeding||1980||21,600-35,600 breeding pairs||medium||A1, A4ii||Endangered|
|Pterodroma macroptera||breeding||1974||1,000-3,000 breeding pairs||-||A4ii||Not Recognised|
|Broad-billed Prion Pachyptila vittata||breeding||1974||1,000-10,000 breeding pairs||-||A4ii||Least Concern|
|Soft-plumaged Petrel Pterodroma mollis||breeding||1974||100-500 breeding pairs||-||A4ii||Least Concern|
|Atlantic Petrel Pterodroma incerta||breeding||1974||100-200 breeding pairs||-||A1, A4ii||Endangered|
|Grey Petrel Procellaria cinerea||breeding||2002||30 individuals||good||A1||Near Threatened|
|Gallinula nesiotis||-||-||-||-||A1||Not Recognised|
|Antarctic Tern Sterna vittata||breeding||1974||50-70 breeding pairs||-||A4i||Least Concern|
|Tristan Thrush Nesocichla eremita||resident||1998||present||-||A1, A2||Near Threatened|
|A4iii Species group - seabirds||breeding||1974||50,000-99,999 individuals||unknown||A4iii|
|Land-use||Extent (% of site)|
|nature conservation and research||-|
References Broekhuysen and Macnae (1949), Brooke (1979), Christophersen (1947), Cooper et al. (1995), Crawford (1941, 1982, 1999), Elliott (1953, 1957), Fraser et al. (1994), Glass et al. (2000), Hagen (1952), Helyer and Swales (1998), Holdgate (1958, 1965), Richardson (1984), Rowan (1951), Rowlands (1992, 1994), Ryan et al. (1990), Stattersfield et al. (1998), Swales (1996), Swales et al. (1993), Wace and Holdgate (1976).
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Recommended citation BirdLife International (2015) Important Bird and Biodiversity Area factsheet: Tristan Island. Downloaded from http://www.birdlife.org on 28/11/2015
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