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Pterodroma externa

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AVES PROCELLARIIFORMES PROCELLARIIDAE

Scientific Name: Pterodroma externa
Species Authority: (Salvin, 1875)
Common Name(s):
English Juan Fernandez Petrel, Juan Fernández Petrel
Spanish Peterel de las Juan Fernádez

Assessment Information [top]

Red List Category & Criteria: Vulnerable D2 ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Brooke, M. & Torres-Mura, J.
Facilitator/Compiler(s): Calvert, R., Clay, R., Lascelles, B., Temple, H.
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.

Geographic Range [top]

Range Description: 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.

Countries:
Native:
Chile; French Polynesia; Guam; Mexico; United States
Vagrant:
Australia; Japan; New Zealand
Present - origin uncertain:
Costa Rica; Ecuador; French Southern Territories; Kiribati; Peru; Pitcairn
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: 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.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and 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).

Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): 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 [top]

Conservation Actions: 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.


Citation: BirdLife International 2012. Pterodroma externa. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 23 October 2014.
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