Pterodroma incerta 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Procellariiformes Procellariidae

Scientific Name: Pterodroma incerta
Species Authority: (Schlegel, 1863)
Common Name(s):
English Atlantic Petrel
French Pétrel de Schlegel
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International.
Identification information: 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.

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(v) ver 3.1
Year Published: 2015
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Cuthbert, R., Hilton, G., Ryan, P. & Wanless, R.
Facilitator/Compiler(s): Clay, R., Ekstrom, J., McClellan, R., Shutes, S., Stattersfield, A. & Temple, H.
This species has been listed as Endangered because 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.

Previously published Red List assessments:
2010 Endangered (EN)
2008 Endangered (EN)
2007 Vulnerable (VU)
2006 Vulnerable (VU)
2004 Vulnerable (VU)
2000 Vulnerable (VU)
1996 Vulnerable (VU)
1994 Vulnerable (VU)
1988 Lower Risk/least concern (LR/lc)

Geographic Range [top]

Range Description: 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 season (P. G. Ryan in litt. 1999), 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 (Richardson 1984, P. G. Ryan in litt. 1999). On Gough, the first quantitative population estimate indicates a total of around 1.8 million pairs (Cuthbert in press), considerably larger than the earlier estimate of at least 20,000 pairs (P. G. Ryan in litt. 1999). 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 (Wanless et al. 2007, R. Wanless et al in litt. 2007, Cuthbert in press). At sea, it is practically restricted to the South Atlantic, occurring off the east coast of South America to the west coast of Africa (Enticott 1991, P. G. Ryan in litt. 1999), occasionally rounding the Cape of Good Hope into the Indian Ocean (Hobbs in litt. 2009).

Countries occurrence:
Argentina; Brazil; Falkland Islands (Malvinas); Namibia; Saint Helena, Ascension and Tristan da Cunha; South Africa; Uruguay
Antarctica; Israel; Jordan; South Georgia and the South Sandwich Islands
Estimated area of occupancy (AOO) - km2: 64
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 15700000
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Number of Locations: 2
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Lower elevation limit (metres): 50
Upper elevation limit (metres): 600
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: On Gough, Cuthbert in litt. (2001) estimated 1.8 million breeding pairs, suggesting a world population of around 5 million birds.

Trend Justification:  R. Wanless in litt. (2007) has commented that population models using data (except breeding success) from Bermuda Petrel Pterodroma cahow suggest the population is declining at a rate of 1.3% per annum.

Current Population Trend: Decreasing
Additional data:
Continuing decline of mature individuals: Yes
Extreme fluctuations: No Population severely fragmented: No
No. of subpopulations: 1 Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: Yes
No. of individuals in largest subpopulation: 100

Habitat and Ecology [top]

Habitat and Ecology: It feeds mainly on squid with some fish and crustaceans (Klages and Cooper 1997). 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 survival (P. G. Ryan in litt. 1999). Heavily affected by Hurricane Catarina in March 2004, 354 birds were recorded blown inland, all in heavy moult and near starvation (Bugoni et al. 2007). Larger numbers of females among these were thought to be due to difference in at-sea distribution or in body condition (Bugoni et al. 2007). Evidence suggests moult is completed during exodus period and before egg-laying, which occurs from 15 June to 21 July (Cuthbert 2004).

Systems: Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat: Unknown
Generation Length (years): 15.6
Movement patterns: Full Migrant
Congregatory: Congregatory (and dispersive)

Threats [top]

Major Threat(s): 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 scarce (Richardson 1984). It is very unlikely to be exploited today (P. G. Ryan in litt. 1999). On Tristan, rats and mice are present and have probably driven it to extinction (Richardson 1984, R. Wanless et al in litt. 2007). 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 (Wanless et al. 2007, R. Wanless et al in litt. 2007, Cuthbert in press, Cuthbert and Hilton in press). The large population of native Southern Skua Catharacta antarctica feed on seabirds including P. incerta (Richardson 1984). 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 sea (P. G. Ryan in litt. 1999). The mortality associated with Hurricane Catarina points to a potential threat from hurricane activity in the South Atlantic, postulated to increase in frequency with global warming (Bugoni et al. 2007).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
On Tristan, a programme to eradicate cats was successful in the 1970s. Gough is a nature reserve and World Heritage Site (Cooper and Ryan 1994). The first ever quantitative population survey was undertaken on Gough, 2000/1, coupled to research into breeding ecology and reproductive output (Cuthbert in press). During 2003-6, further research on reproductive output and mouse predation was conducted. Searches on Tristan da Cunha have failed to locate any birds (Wanless et al. 2007).

Conservation Actions Proposed
Eradicate mice from Gough. Minimise the risk of further introduced species establishing on Gough, particularly any rat Rattus species (P. G. Ryan in litt. 1999). Confirm the status of the population on Tristan da Cunha.

Citation: BirdLife International. 2015. Pterodroma incerta. The IUCN Red List of Threatened Species 2015: e.T22698084A84681773. . Downloaded on 30 November 2015.
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