Justification This species has been uplisted to Endangered becuase it has an extremely small occupied breeding range, and there is now evidence that that chick predation by introduced mice is causing very low breeding success and is likely to be causing the population to decline. It has not been recorded from Tristan de Cunha for 35 years, and, were it to be confirmed as extinct there, it may qualify for uplisting to Critically Endangered.

Family/Sub-family Procellariidae

Species name author (Schlegel, 1863)

Taxonomic source(s) AERC TAC (2003), Brooke (2004), Dowsett and Forbes-Watson (1993), SACC (2005 + updates), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Identification 43 cm. Large, stocky, dark brown-and-white petrel. Uniformly dark chocolate-brown above and on upper breast. Head can appear grey in worn plumage. Sharp demarcation from brown upper breast to white lower breast and belly. Brown vent, undertail-coverts and tail. Uniform brown underwing. Similar spp. Soft-plumaged Petrel P. mollis has patterned underwing. Trindade Petrel P. arminjoniana has white wing flashes. Hints May flap at top of glides unlike most Pterodroma spp. Concentrates around subtropical convergence.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

5,000,000

decreasing

16,600,000 km²

Yes

Range & population Pterodroma incerta breeds only on Gough Island, Tristan da Cunha (St Helena to UK). It is absent from Nightingale where there is no suitable habitat, and probably also from Inaccessible, although it is possible that a small number of birds could breed there because there have been no surveys during the winter breeding season⁵, and Tristan, where though the population was estimated to be 100-200 pairs in 1972-1974, there have been no records since then at it is now beleived to be extinct on that island^4,5. On Gough, the first quantitative population estimate indicates a total of around 1.8 million pairs⁶, considerably larger than the earlier estimate of at least 20,000 pairs⁵. Recent evidence suggests that fledging success is very low, less than 20% during the last five years and perhaps as low as 2% in 2007, and this is likely to be driving a long term decline^6,8,9. At sea, it is practically restricted to the South Atlantic, occurring off the east coast of South America to the west coast of Africa^2,5.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: It feeds mainly on squid with some fish and crustaceans³. It nests in burrows dug in peaty soils in fern-bush vegetation from 50-300 m on Gough and formerly, at higher elevations on Tristan. Nothing is known of age of first breeding, breeding frequency or survival⁵.

Threats This species was once of major economic importance to the Tristan Islanders as it was one of the few sources of food in winter but, by the 1940s, the birds had become scarce⁴. It is very unlikely to be exploited today⁵. On Tristan, rats and are present and have probably driven it to extinction^4,9. On Gough, the only potential introduced predator is the house mouse Mus musculus and recent research reveals that mice are predating chicks and causing very low breeding success which is driving the long-term decline^6,7,8,9. The large population of native Southern Skua Catharacta antarctica feed on seabirds including P. incerta⁴. Night strikes (as a result of being attracted to lights) are a further threat. This has been ameliorated at the Gough meteorological station, but may still pose a problem on ships at sea⁵.

Conservation measures underway On Tristan, a programme to eradicate cats was successful in the 1970s. Gough is a nature reserve and World Heritage Site¹. The first ever quantitative population survey was undertaken on Gough, 2000/1, coupled to research into breeding ecology and reproductive output⁶. During 2003-6, further research on reproductive output and mouse predation was conducted. Searches on Tristan da Cunha have failed to locate any birds⁸.

Conservation measures proposed Eradicate mice from Gough. Minimise the risk of further introduced species establishing on Gough, particularly any rat Rattus species⁵. Confirm the status of the population on Tristan da Cunha.

References 1. Cooper and Ryan (1994). 2. Enticott (1991). 3. Klages and Cooper (1997). 4. Richardson (1984). 5. P. G. Ryan in litt. (1999). 6. Cuthbert (in press). 7. Cuthbert and Hilton (in press). 8. Wanless et al. (2007). 9. R. Wanless et al in litt. (2007).

Text account compilers Rob P Clay (Guyra Paraguay), Jonathan Ekstrom (BirdLife International), Rachel McClellan (BirdLife International), Sue Shutes (BirdLife International), Alison Stattersfield (BirdLife International), Helen Temple (BirdLife International)

Contributors Richard Cuthbert (Royal Society for the Protection of Birds), Geoff Hilton (Royal Society for the Protection of Birds), Peter G. Ryan (Percy FitzPatrick Institute of African Ornithology), Ross Wanless

IUCN Red List evaluators Stuart Butchart (BirdLife International), Simon Mahood (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Pterodroma incerta. Downloaded from http://www.birdlife.org on 10/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums