The site comprises the whole of Nightingale Island as well as Middle and Stoltenhoff Islands and the offshore islets and stacks, as described in the ‘General introduction’.
See Box and Table 2 for key species. At least 30 bird taxa are known. Thirteen species of breeding seabird and three of the native landbirds occur. The seabirds comprise Eudyptes chrysocome moseleyi, Diomedea chlororhynchos, Phoebetria fusca, Pterodroma mollis, Pachyptila vittata, Puffinus gravis, P. assimilis, Pelagodroma marina, Fregetta grallaria, Pelecanoides urinatrix (>20,000 pairs), Catharacta antarctica, Sterna vittata and Anous stolidus. The breeding population of P. gravis is the largest known, and at the highest density, in the world, with an estimated one million pairs per km². Pterodroma brevirostris may also breed. The terrestrial species include Nesocichla eremita procax (330–560 pairs, 1974 estimate), Nesospiza acunhae questi (560–1,120 pairs, 1974 estimate) and N. wilkinsi wilkinsi (30 pairs, 1974 estimate).Non-breeding visitors include Diomedea melanophris, Macronectes giganteus, M. halli, Fulmarus glacialoides, Daption capense, Procellaria a. aequinoctialis, P. a. conspicillata and Larus dominicanus.
Non-bird biodiversity: The only breeding native mammal is Arctocephalus tropicalis. At least 31 species of native terrestrial invertebrates are known, including five endemic listroderine weevils and seven endemic drosophilid Scaptomyza.
Pressure/threats to key biodiversity
The site has been less affected by alien animals than the other sites, and no alien vertebrates have become established. Besides the annual harvest by Tristan islanders of Eudyptes chrysocome moseleyi eggs and Puffinus gravis eggs and chicks, of which the annual toll is not high, the remaining seabirds are little affected. The introduction of mammalian predators and tussock fires are the principal threats, while the recent die-back of trees, possibly caused by an introduced fungal pathogen, is being investigated, but is potentially, serious for Nesospiza wilkinsi.