Data Zone
Justification of Red List category
This species has been recorded in small numbers at a small number of localities and so its population size is likely to be very small. Its population size is inferred to be declining due to ongoing habitat degradation and predation by invasive American Mink. For these reasons, the species is listed as Vulnerable.
Population justification
The species's population size is poorly known, but given that there were no documented records from 1959 to 1998, it is likely to be rare. It is fairly common at a handful of sites, with no known locality holding a population of more than c.35 individuals (Mazar Barnett et al. 1998, 2014, Imberti and Mazar Barnett 1999). Extensive surveys carried out between 1998 and 2006 at 58 wetlands distributed over an area of c.700,000 km2 detected a maximum of 175 individuals in total, at 22 localities that collectively held approximately 85 km2 of habitat (Mazar Barnett et al. 2014). Surveys in Santa Cruz in 2009-2013 detected at least one individual at each of two more localities (Roesler et al. 2014). Given the difficulty of detecting the species, there are likely to be undetected individuals. Nevertheless, the total population size is very unlikely to exceed 10,000 mature individuals, and could plausibly be less than 2,500 mature individuals (Mazar Barnett et al. 2014), so it is here placed in the band 1,000-9,999 mature individuals, with a best estimate in the range 2,500 - 9,999 mature individuals.
The subpopulation structure is poorly known, but a record of a vagrant individual in the Falkland Islands indicates that the species is able to disperse over large distances, so there is likely to be a degree of connectivity between habitat fragments. The population is therefore assumed to have a single subpopulation.
Trend justification
The species is threatened by continuing overgazing at some localities such as El Zurdo (A. de Miguel, I. Roesler and L. Fasola in litt. 2018), and by invasive American Mink Neovison vison, which is expanding its range (Mazar Barnett et al. 2014, Roesler et al. 2014, Fasola and Roesler 2016). Surveys in Santa Cruz found that the species's population density and site occupancy were negatively affected by the presence of mink (de Miguel et al. 2019). The species's range appears to have contracted considerably in the long-term, with no recent records from much of the known historical range. The species's population size is therefore inferred to be undergoing a continuing decline, the rate of which is unknown.
Rallus antarcticus is known from southern Chile and Argentina. It is thought to have populations in five geographically distinct areas: 1) the Magellanic steppe south of the Gallegos River and Coyle River Basins; 2) the transitional region of the Torres del Paine and Glaciares National Parks; 3) around Gobernador Gregores, along the Chico River Basin; 4) the Deseado River Basin; and 5) along a coastal axis in north-eastern Patagonia (Mazar Barnett et al. 2014). The species has been recorded historically in Tierra del Fuego, Buenos Aires, and Rio Negro, Santa Cruz and Chubut in Argentina, and in Valparaiso, Santiago, Colchagua, Llanquihue and Magallanes in Chile. It was previously known from just a few specimens and sight records, and since 1959, there were no documented records until the species was rediscovered in 1998, at Estancia La Angostura, Santa Cruz, Argentina (Mazar Barnett et al. 1998). Further fieldwork in 1998-2006 recorded the species at a total of 21 localities in in Santa Cruz, Chubut, Buenos Aires and Rio Negro, Argentina, and in Magallanes (XII Region), Chile (Imberti and Mazar Barnett 1999, Imberti and Mazar Barnett 2003, Pugnali et al. 2004, Soave et al. 2009, Mazar Barnett et al. 2014). Surveys in Santa Cruz in 2009-2013 detected the species at two more localities (Roesler et al. 2014). Records from Buenos Aires, Rio Negro and the Valdes Peninsula were made outside the breeding season and may have represented migratory or vagrant individuals (Mazar Barnett et al. 1998, Pugnali et al. 2004, Mazar Barnett et al. 2014). A record from the Falkland Islands (Malvinas) is likely to have been a vagrant individual, suggesting a tendency to undergo long-distance movements (Pugnali et al. 2004). All recent records fall outside the historical range, suggesting a large range contraction (J. Mazar Barnett in litt. 2000, 2003). Nesting has been confirmed only in Torres del Paine National Park, Chile (Matus et al. 2017) and in a locality adjacent to Los Glaciares National Park in Argentina (Moroni and Salvador 2016).
It occurs in marshy steppe wetlands, where there are large patches of dense and tall (c.2 m) rushbeds Schoenoplectus (Scirpus) californicus, usually surrounded by wet meadows with lush green grass, and associated with a permanent water body, such as a river, stream or lake (Mazar Barnett et al. 1998, A. Jaramillo in litt. 2000, Imberti and Mazar Barnett 2003, Mazar Barnett et al. 2014). It appears to leave sites with less favourable habitat during the winter, and some northerly post-breeding dispersal or possibly partial migration may occur, at least in southern populations (Mazar Barnett et al. 1998, 2014).
Intensive grazing by cattle and sheep has degraded wet grassland and marshes across much of the species's current and historic range, especially in the Tierra del Fuego steppe (Mazar Barnett et al. 2014). In surveys, the species was not recorded at sites that had been degraded through overgrazing (Imberti and Mazar Barnett 2003, Mazar Barnett et al. 2014, de Miguel et al. 2019). Overgrazing continues to pose a threat at some localities where the species has been recorded, such as at El Zurdo, Santa Cruz (Mazar Barnett et al. 2014, S. Imberti in litt. 2020). However, two of the most important populations, at Estancias Brazo Norte and La Angostura, are currently managed appropriately with only light grazing (Mazar Barnett et al. 2014). Marshes at La Soledad and El Sosiego ranches are also subject only to light grazing (Mazar Barnett et al. 2014). Burning and harvesting of aquatic vegetation to promote spring growth and to produce hay for cattle may also be pressures (Fjeldså 1988). These practices are now much less common than they were in the past (Blanco and Canevari 1995, Mazar Barnett et al. 2014), but surveys in Santa Cruz found that the species's population density was negatively affected by habitat burning (de Miguel et al. 2019). Burning leads to a decreased density of rushes, making the habitat less favourable to the Austral Rail (de Miguel et al. 2019).
Water extraction for agriculture and other purposes, and modification of watercourses through canalisation and damming also negatively impact on wetlands (J. Mazar Barnett in litt. 2000, 2003, Imberti and Mazar Barnett 2003). Important populations at Estancia El Sosiego and near Punta Banderas, Parque Nacional Los Glaciares, would be flooded by the completion of two dams that are being constructed on the Río SantaCruz, affecting the natural outflow of Lago Argentino (de Miguel et al. 2019).
Habitat in Central Chile, where the species was recorded historically, has been degraded via firewood extraction and conversion to agriculture (Mazar Barnett et al. 2014). Any further development of further intensive agriculture in suitable river valleys is likely to involve irrigation and wetland drainage and thus the loss of wetland habitat (Imberti and Mazar Barnett 2003).
The species is also threatened by invasive American Mink Neovison vison, which may have played a role in the species's decline (Fraga 2000, Mazar Barnett et al. 2014). The mink is present in northern Magallanes and Santa Cruz, including in some river basins inhabited by the Austral Rail, and its range is expanding (Mazar Barnett et al. 2014, Roesler et al. 2014, Fasola and Roesler 2016). Surveys in Santa Cruz found that the species's population density and site occupancy were negatively affected by the presence of mink (de Miguel et al. 2019).
Conservation Actions Underway
The species is listed as nationally Endangered in Argentina (MAyDS and Aves Argentinas 2017). It occurs in several protected areas including Torres del Paine, Pali Aike and Los Glaciares National Parks, Bosques Petrificados Natural Monument, Península Valdés and Laguna Nimez (Imberti and Mazar Barnett 1999, A. Jaramillo in litt. 2000, Imberti and Mazar Barnett 2003, Mazar Barnett et al. 2014, S. Imberti in litt. 2020).
Extensive mink control has taken place in the Buenos Aires Lake Plateau area, and there were plans to expand control efforts into the lowlands where they may benefit the rail (Fasola and Roesler 2016). At La Angostura, a portion of the wetland is managed to protect rails to support birdwatching tourism (de Miguel et al. 2019).
20 cm. Small, boldly patterned rail. Buffy-brown upperparts streaked black. Pale slaty underparts with sides of breast washed brown. Black lower belly and vent barred white. White undertail-coverts. Red iris. Dusky red bill. Pinkish-red legs. Similar spp. Plumbeous Rail Pardirallus sanguinolentus is larger with longer, green bill, plain upperparts and unbarred rear. Other similarly patterned crakes are much smaller. Voice Series of 5-10 high-pitched and strident pí-ríc notes introduced by a single píc, also a loud call pi-choj (usually higher at the beginning) that seems to be a duet but it is performed by one bird, and a recently-described tri-ti-ti-ti-ti-ti (S. Imberti in litt. 2007).
Text account compilers
Wheatley, H.
Contributors
Imberti, I., Jaramillo, A.P., Mazar Barnett, J., Pearman, M., Capper, D., Sharpe, C.J., Benstead, P., Symes, A. & Pilgrim, J.
Recommended citation
BirdLife International (2024) Species factsheet: Austral Rail Rallus antarcticus. Downloaded from
https://datazone.birdlife.org/species/factsheet/austral-rail-rallus-antarcticus on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/12/2024.