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Juan Fernandez Petrel Pterodroma externa

Justification
This species is classified as Vulnerable owing to its very small breeding range, in which it is susceptible to to human impacts and stochastic events. Confirmation that introduced predators are causing a decline would result in an uplisting to Critically Endangered.

Taxonomic source(s)
Brooke, M. de L. 2004. Albatrosses and Petrels Across the World. Oxford University Press, Oxford.
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.
SACC. 2006. A classification of the bird species of South America. Available at: #http://www.museum.lsu.edu/~Remsen/SACCBaseline.html#.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Identification
43 cm. Large, grey-and-white petrel. Black cap extends to below eyes while white of throat may extend up behind eyes, enhancing capped appearance. Grey upperparts and upperwing, with black "M" across wings. Base of grey tail can show whitish horseshoe. White underparts. White underwing with narrow black trailing edge, black tip, narrow black edge to leading edge distal to carpal joint and then short, bolder, black bar extending from joint towards centre of wing. Similar spp. Larger than overlapping Stejneger's Petrel P. longirostris, and has different underwing pattern. Hawaiian Petrel P. sandwichensis has darker cap and more extensive black on underwing.

Distribution and population
Pterodroma externa breeds on Alejandro Selkirk Island in the Juan Fernández Islands, Chile. It is very numerous, but could be declining (Schlatter 1984), although there is no firm evidence of this (Brooke 2004). It is a transequatorial migrant, dispersing over the tropical and subtropical waters of the east Pacific, north to Hawaii, USA, and is regularly seen off west Mexico, with vagrants recorded in New Zealand and east Australia (Carboneras 1992d, Patterson 1996). Further information may indicate declines that would warrant uplisting the species.

Population justification
In 1986 the population was estimated at 1,000,000 pairs, which extrapolates to a world population of at least 3,000,000 individuals. There is no firm evidence of decline.

Trend justification
There is no firm evidence of decline (Brooke 2004).

Ecology
It is highly pelagic, rarely approaching land except at breeding colonies. It nests in burrows on slopes in Dicksonia externa fern-forest and adjacent grasslands at elevations of 600-1,000 m (J. C. Torres-Mura in litt. 1999). One egg is laid in October-November (Carboneras 1992d) and chicks hatch in Feb-March (Hodum and Wainstein 2003). It is dependent on subsurface predators, especially yellowfin tuna, to drive prey to the surface (Au and Pitman 1986, Ballance et al. 1997).

Threats
The goat population was reduced by a Dutch hunting control programme in the late 1990s through to 2003 (6,000 down to 2,000), but remains a problem in all breeding colonies. Given that the control programme is no longer active, the population will presumably rebound within the next few years. Goat impacts include habitat alteration through plant consumption and also, at times, direct collapses of burrows (Hulm 1995, J. C. Torres-Mura in litt. 1999, Torres in litt. 2007, Hodum in litt. 2007). Feral cat predation is thought to be causing a population decline, with a preliminary estimate of 2-3% annual mortality from cat predation. Brown rats Rattus norvegicus also prey on chicks although the incidence appears low and restricted to certain habitat types (J. C. Torres-Mura in litt. 1999, Hodum in litt. 2007). Dogs may also be causing a population decline (J. C. Torres-Mura in litt. 1999). Flash flooding in 2002 caused severe localised habitat loss with an estimated 30,000 burrows destroyed (Hodum and Wainstein 2003). In 1995, a fire destroyed habitat at the edge of the principal colony and directly killed thousands of birds (J. C. Torres-Mura in litt. 1999, Hodum in litt. 2007). Decreased lobster catches near Isla Robinson Crusoe are displacing fishers to Alejandro Selkirk (where the species lives between September and May), resulting in an increase in human disturbance on the breeding grounds (J. C. Torres-Mura in litt. 1999). Fisheries may be indirectly impacting upon the species by depleting stocks of subsurface predators. During the night there are some collisions of birds with the lights of the village on Alexander Selkirk (especially on misty nights). The village is inhabited from September to May, during the period of lobster exploitation (Hodum in litt. 2007). The species is potentially threatened by climate change because it has a geographically bounded distribution: its altitudinal distribution falls entirely within 2,000 m of the highest mountain top within its range (1,649 m).

Conservation Actions Underway
The Juan Fernández Islands were designated as a National Park in 1935 (protected from 1967) and a Biosphere Reserve in 1977 (Stattersfield et al. 1998, J. C. Torres-Mura in litt. 1999). The Chilean government began a habitat restoration programme in 1997 (J. C. Torres-Mura in litt. 1999), and the islands have been nominated for World Heritage listing (Hulm 1995). Reserve rangers have been trained in fighting fires, but there is only one ranger on Alejandro Selkirk (J. C. Torres-Mura in litt. 1999). Sheep were removed from Alejandro Selkirk in 1983 (Carboneras 1992d). A Dutch funded goat eradication programme was unsuccessful. Conservation Actions Proposed
Establish population monitoring plots (M. de L. Brooke in litt. 1999). Improve sustainable management of yellowfin tuna stocks. Eradicate introduced fauna (goats, cows, rats etc) from Alejandro Selkirk. Monitor effects of flash floods on colonies.

References
Au, D. W. K.; Pitman, R. L. 1986. Seabird interactions with dolphins and tuna in the eastern tropical Pacific. Condor 88: 304-317.

Ballance, L. T.; Pitman, R. L.; Reilly, S. B. 1997. Seabird community structure along a productivity gradient: importance of competition and energetic constraint. Ecology 78: 1502-1518.

Brooke, M. De L. 2004. Albatrosses and petrels across the world. Oxford University Press, Oxford.

Carboneras, C. 1992. Procellariidae (Petrels and Shearwaters). In: del Hoyo, J.; Elliott, A.; Sargatal, J. (ed.), Handbook of the birds of the world, pp. 216-257. Lynx Edicions, Barcelona, Spain.

Hodum, P.; Wainstein, M. 2003. Biology and conservation of the Juan Fernadez seabirds community.

Hulm, P. 1995. Robinson Crusoe's Islands face an uncertain future. Plant Talk: 19-21.

Patterson, R. M. 1996. RAOU records appraisal committee: opinions and case summaries 1992-1995. Submission no. 168. RAOU Report 101.

Schlatter, R. P. 1984. The status and conservation of seabirds in Chile. In: Croxall, J.P.; Evans, P.G.H.; Schreiber, R.W. (ed.), Status and conservation of the world's seabirds, pp. 261-269. International Council for Bird Preservation, Cambridge, U.K.

Stattersfield, A. J.; Crosby, M. J.; Long, A. J.; Wege, D. C. 1998. Endemic bird areas of the world: priorities for bird conservation. BirdLife International, Cambridge, U.K.

Further web sources of information
Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Calvert, R., Clay, R., Lascelles, B., Temple, H.

Contributors
Brooke, M., Torres-Mura, J.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Pterodroma externa. Downloaded from http://www.birdlife.org on 25/11/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/11/2014.

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.

Additional resources for this species

ARKive species - Juan Fernández petrel (Pterodroma externa) 0

Key facts
Current IUCN Red List category Vulnerable
Family Procellariidae (Petrels, Shearwaters)
Species name author (Salvin, 1875)
Population size mature individuals
Population trend Stable
Distribution size (breeding/resident) 44,100,000 km2
Country endemic? Yes
Links to further information
- Additional Information on this species