Justification of Red List Category
Until 1998, there were only three records of this species since 1900, and none since 1959. Surveys have now found it to be more widespread and numerous than previously feared. The known population remains small, fragmented and probably declining, qualifying it as Vulnerable. However, the voice was only determined in 1998, and further surveys may find it with some regularity, potentially resulting in a future downlisting to Near Threatened.
A population estimate of 2,500-9,999 mature individuals has been derived from analyses of recent records and surveys by BirdLife International (2001). This is equivalent to 3,750-14,999 individuals, rounded here to 3,500-15,000 individuals.
This species's population is suspected to have decreased slightly in line with levels of habitat degradation owing to agricultural development, particularly intensive grazing of the steppes, water extraction and (previously) harvesting of aquatic vegetation for cattle.
Rallus antarcticus was rediscovered in 1998, and has been subsequently found at seven localities in Santa Cruz and two in Chubut, Argentina, and two in Magallanes, Chile (Mazar Barnett et al. 1998b, Imberti and Mazar Barnett 1999, Pugnali et al. 2004, Soave et al. 2009, M. Pearman in litt. 2003, J. Mazar Barnett in litt. 2000, 2003). It is fairly common at three sites, with the largest population holding c.35 birds (Mazar Barnett et al. 1998b, Imberti and Mazar Barnett 1999, J. Mazar Barnett in litt. 2000, 2003). Curiously all recent records fall outside the historical range, despite searches at former haunts (J. Mazar Barnett in litt. 2000, 2003). The fact that it has been found in Patagonia in the breeding season, whereas the historical Buenos Aires specimens were taken in autumn/winter may indicate that the species is migratory (Mazar Barnett et al. 1998, Pugnali et al. 2004), although old breeding records from central Chile suggest otherwise (A. Jaramillo in litt. 2012). A tendency to undergo long-distance movements is suggested by a recent record from the Falkland Islands (Malvinas) (Pugnali et al. 2004). It was previously known from a few specimens and fewer confirmed sight records, with none since 1959. In addition historical records exist for Buenos Aires, Río Negro, Santa Cruz and Tierra del Fuego, Argentina, and Valparaiso, Santiago, Colchagua and Llanquihué, Chile. The population is estimated at 2,500 to 9,999 individuals, but recent surveys at the nine locations only added a further 125 individuals to the known total, and there are concerns that the population may actually be below 2,500 (J. Mazar Barnett in litt. 2000, 2003). The last major surveys, carried out between 1998 and 2006 over an area of c. 700,000 km2, detected a maximum of 175 individual rails at 22 localities (Mazar Barnett et al. 2014).
It occurs in marshy Patagonian steppe wetlands (Mazar Barnett et al. 1998b, J. Mazar Barnett in litt. 2000, 2003), where there are large patches of dense and tall (c.2 m) rushbeds Schoenoplectus (Scirpus) californicus, and open areas, densely covered by Myriophyllum sp. and lush green grass (Mazar Barnett et al. 1998b, A. Jaramillo in litt. 2000). Some northerly post-breeding dispersal or possibly partial migration may occur, at least in southern populations (Mazar Barnett et al. 1998b).
The most serious threat is the planned development of intensive agriculture in suitable river valleys (S. Imberti in litt. 1999). Intensive grazing of the steppes may have affected wetlands, because the resulting bare soil has been deposited in pools and marshes by the wind (Fjeldså 1988). There has been extensive harvesting of aquatic vegetation for cattle (Fjeldså 1988). However, this practice is now limited in many areas (Blanco and Canevari 1995), and rushbeds at the site of the rediscovery (and presumably elsewhere) have increased in recent years owing to the particularly wet climate (Mazar Barnett et al. 1998b). Water extraction for agriculture and other purposes may negatively impact on wetlands (J. Mazar Barnett in litt. 2000, 2003).
Conservation Actions Underway
Targeted surveys are responsible for recent records (Mazar Barnett et al. 1998b, A. Jaramillo in litt. 2000, J. Mazar Barnett in litt. 2000, 2003). One population lies adjacent to Los Glaciares National Park but, since cattle graze inside and outside the reserve, its extension would currently offer minimal protection (J. Mazar Barnett in litt. 2000, 2003). Laguna Nimes municipal reserve offers some protection (S. Imberti in litt. 2007). In Chile, it occurs in Pali Aike and Torres del Paine National Parks (Imberti and Mazar Barnett 1999, A. Jaramillo in litt. 2000), with extensive habitat remaining in the former (Imberti and Mazar Barnett 1999). It has bred in Torres del Paine National Park (Matus and Jaramillo, unpublished: A. Jaramillo in litt. 2012).
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
Benstead, P., Capper, D., Mazar Barnett, J., Pilgrim, J., Sharpe, C J, Symes, A.
Jaramillo, A., Imberti, I., Pearman, M., Mazar Barnett, J.
BirdLife International (2020) Species factsheet: Rallus antarcticus. Downloaded from http://www.birdlife.org on 02/06/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/06/2020.