VU
Stejneger's Petrel Pterodroma longirostris



Justification

Justification of Red List Category
This species qualifies as Vulnerable owing to its very small breeding range, which renders it susceptible to stochastic events and human impacts. Confirmation that introduced predators are causing a decline may qualify it for uplisting to a higher threat category.

Population justification
In 1986, the population was estimated at 131,000 pairs, implying a world population in excess of 400,000 individuals.

Trend justification
The population is estimated at 131,000 pairs (Carboneras 1992d), but more recent estimates suggest that it may be lower (Hodum and Wainstein 2003, 2004) and declining.

Distribution and population

Pterodroma longirostris breeds on Alejandro Selkirk Island in the Juan Fernández Islands, Chile. The population is estimated at 131,000 pairs (Carboneras 1992d), but more recent estimates suggest that it may be lower (Hodum and Wainstein 2003, 2004) and may be declining. It is a migrant to the north-west Pacific off Japan (Roberson and Bailey 1991). Birds appear to move through a corridor south-east of Hawaii in April-June (Roberson and Bailey 1991), with some straying as far south as North Island, New Zealand (Falla 1962). There may be a clockwise movement through the north Pacific in late summer and autumn, with birds recorded off California, USA (Roberson and Bailey 1991).

Ecology

It nests in burrows on slopes in Dicksonia externa fern-forest and adjacent grasslands at elevations of 700-1,1120 m (J. C. Torres-Mura in litt. 1999, Reyes-Arriagada et al. 2012). Breeding begins in November. One egg is laid in late November-early December with hatching in late January-mid February. Fledging occurs in May. It forms mixed-species colonies with Juan Fernandez Petrel P. externa (Carboneras 1992d), typically forming small monospecific clusters of burrows in shallow soils within the larger P. externa colony (Hodum and Wainstein 2003, 2004, Reyes-Arriagada et al. 2012). It feeds in pelagic waters primarily on squid and small fish (Hodum and Wainstein 2003, 2004).

Threats

Predation by feral cats, introduced brown rats Rattus norvegicus (Jones et al. 2008) and house mice Mus musculus has been documented (Hodum and Wainstein 2003, 2004) and may be causing a population decline (J. C. Torres-Mura in litt.1999, Hodum and Wainstein 2003, 2004, Hodum 2009). Stejneger's Petrel appears to be disproportionately preyed upon in comparison with the larger Juan Fernandez Petrel and there is the suggestion that a population decline has occurred most likely driven by predation at breeding sites (Shirahai et al. 2015). Additionally, feral cats prey on near-fledging chicks when they are on the surface exercising their flight muscles, although predation rates have not been quantified (Hodum 2009). Rodents also contribute to slowing native forest regeneration by eating fruit, seeds and seedlings. Cattle are a potential problem, causing defoliation, accelerated soil erosion and compaction, their impact however, seems to be limited to lower elevations than Stejneger’s Petrel is known to nest.

Due to being a restricted range species, Stejneger’s Petrel is very vulnerable to habitat shifting and alteration due to climate change, as well as extreme weather events, such as four landslides caused by a storm in 2002.

Conservation actions

Conservation Actions Underway

The Juan Fernández Islands were designated as a national park in 1935 (protected from 1967) and a UNESCO 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) which included goat control, but it concluded in 2003. The islands have been nominated for World Heritage listing (Hulm 1995). Park 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 1992). Population monitoring plots were established between 2003-2006 by Oikonos Ecosystem Knowledge (Hodum 2009). Oikonos also maintains an ongoing small-scale community conservation education programme in the islands, including on Alejandro Selkirk. Incipient invasive plant species are also being systematically eliminated from the island by Oikonos in collaboration with the Corporación Nacional Forestal (CONAF), the Chilean agency that administers the park.

Conservation Actions Proposed

Maintain and expand population monitoring plots (Hodum and Wainstein 2003, 2004, Hodum 2009). Determine contemporary breeding population size. Eradicate introduced fauna (feral cats, rats, mice and goats) from Alejandro Selkirk. Eradicate invasive and incipient invasive plant species from the island. Improve community awareness of the status of the species and the need for eradication programmes.

Identification

26 cm. Small, typical M marked gadfly petrel. Dark grey upperparts with sharp M mark. Bold and very dark grey cap and mask, extending to dark grey half collar on upper breast. Dark grey rump and uppertail-coverts. White throat and lower chest/belly. Predominantly white underwing, but black tip and narrow black trailing edge, extending to leading edge with slight thickening at carpal joint. Similar spp. Separated from most other small gadfly petrels by whiter underwing. Cook's Petrel P. cookii and de Filippi's Petrel P. defilippiana have paler crown and nape, and outertail feathers that are paler than central feathers. Pycroft's Petrel P. pycrofti has less extensive dark patch around eye. Juan Fernández Petrel P. externa is larger, with white on rump and small black carpal patch.

Acknowledgements

Text account compilers
Moreno, R., Stuart, A., Fjagesund, T., Bird, J., Frere, E., Hermes, C., Lascelles, B., Clay, R.P., Martin, R., Calvert, R.

Contributors
Torres-Mura, J., Hodum, P.


Recommended citation
BirdLife International (2019) Species factsheet: Pterodroma longirostris. Downloaded from http://www.birdlife.org on 21/04/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/04/2019.