Pterodroma externa 

Scope: Global

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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
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, 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.

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.
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.

Previously published Red List assessments:

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 occurrence:
Chile; French Polynesia; Guam; Mexico; United States
Australia; Japan; New Zealand
Present - origin uncertain:
Costa Rica; Ecuador; French Southern Territories; Kiribati; Peru; Pitcairn
Additional data:
Estimated area of occupancy (AOO) - km2:13Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:44100000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):600
Upper elevation limit (metres):1000
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.

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

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

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
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): 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 2012: e.T22698030A40203402. . Downloaded on 26 October 2016.
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