Archived 2012-2013 topics: Tsingy Wood Rail (Canirallus beankaensis): newly recognised and Near Threatened?

This discussion was first published as part of the 2012 Red List update, but remains open for comment to enable reassessment in 2013. Tsingy Wood Rail Canirallus beankaensis was recently described as a new species by Goodman et al. (2011), who studied the morphology, plumage and genetics of two specimens, in relation to that of Madagascar Wood Rail C. kioloides. This species is currently known from a restricted area of lowland central-western Madagascar, including portions of the Bemaraha and Beanka Massifs, and has so far been found at elevations of 100-320 m in areas of limestone karst with rock pinnacles, known as tsingy (Goodman et al. 2011). The tsingy landscape holds a portion of the seasonsally dry deciduous forest of western Madagascar (e.g. Du Puy and Moat 1996), and the species itself has often been recorded in canyons and valleys that are closed or bordered by exposed rock and contain relatively dry deciduous forest (Goodman et al. 2011). Mapping of the species’s likely range, based on the distribution of the vegetation and geological characteristics that are indicative of the tsingy landscape (Du Puy and Moat 1996) in the vicinity of known records, has resulted in an estimate for its Extent of Occurrence (EOO) of c.3,800 km2 (see draft range map). This estimated EOO meets the range size threshold for Endangered under criterion B1 (EOO <5,000 km2). However, the species’s habitat and population are not regarded as severely fragmented (which according to the IUCN Red List criteria and guidelines is defined by over 50% of suitable habitat existing in patches too small to support viable populations and separated by distances several times larger than the species’s average long-term dispersal distance) owing to difficulties for humans in the access to and utilisation of much of its range, and it is unlikely to be restricted to a few locations (where a ‘location’ is defined as geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals present). BirdLife draft range map for Tsingy Wood Rail, with points showing the locations of the two specimens studied by Goodman et al. (2011) (click on map to see larger version) Although much of the tsingy region is not vulnerable to human modification, limited habitat loss and degradation are thought to be taking place through shifting cultivation, conversion to pasture, wood harvesting and extraction of other forest resources. These threats are further limited by the low human population density and alleviated by the legal protection of the Tsingy de Bemaraha in a national park and strict nature reserve (del Hoyo et al. 1996, Taylor 1998, Rasoloarison and Pasquier 2003). However, in 1984 oil prospectors created a seismographic trail through the tsingy by means of explosives, thus facilitating access to areas that were previously impenetrable (Rasoloarison and Paquier 2003). Fires are set in the nature reserve in order to stimulate the growth of grass for grazing and to clear trails. Such uncontrolled fires and tree-cutting for house construction, fences and firewood are the primary causes of forest destruction, and some hunting is known to take place (Rasoloarison and Paquier 2003). A continuing decline in the number of mature individuals can be inferred to be taking place owing to the on-going but limited loss and degradation of suitable habitat, as well as the likelihood of limited hunting pressure, bearing in mind that not all of the species’s estimated range is protected. Given that this species is estimated to have a very small range, it may also have a small population (e.g. del Hoyo et al. 1996, Taylor 1998), and thus is likely to number fewer than 10,000 mature individuals, potentially meeting the thresholds for Vulnerable under criterion C2. However, there is apparently no information available on the species’s sub-population structure, i.e. whether all mature individuals form one sub-population or, if not, whether all sub-populations number no more than 1,000 mature individuals (where ‘sub-populations’ are defined as geographically or otherwise distinct groups between which there is little demographic or genetic exchange, i.e. typically one successful migrant per year or less). It is therefore proposed that the species be listed as Near Threatened under criteria B1a+b(iii,v); C2a(ii), on the basis that it has a very small range and probably has a small population, with continuing declines observed in the area, extent and/or quality of habitat and inferred to be taking place in the number of mature individuals, but with no information on the sub-population structure or evidence to suggest that the population is severely fragmented or restricted to a few locations. Comments on this proposed listing are invited and further information would be welcomed. References: del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the birds of the world, Vol 3: Hoatzin to Auks. Barcelona, Spain: Lynx Edicions. Du Puy, D. J. and Moat, J. (1996) A refined classification of the primary vegetation of Madagascar based on the underlying geology: Using GIS to map its distribution and to assess its conservation status. Pp 205-218 in Lourenço, W. R. (Ed) Biogeography of Madagascar. Paris, France: Orstom Éditions. Goodman, S. M., Raherilalao, M. J. and Block, N. L. (2011) Patterns of morphological and genetic variation in the Mentocrex kioloides complex (Aves: Gruiformes: Rallidae) from Madagascar, with the description of a new species. Zootaxa 2776: 49-60. Moat, J. and Smith, P. (2007) Atlas of the Vegetation of Madagascar. Richmond, UK; Kew Publishing, Royal Botanic Gardens, Kew. Rasoloarison, V. and Paquier, F. (2003) Tsingy de Bemaraha. Pp1507-1512. In Goodman, S. M. and Benstead, J. P. (Eds) The Natural History of Madagascar. Chicago, IL: University of Chicago Press. Taylor, B. (1998) Rails: A Guide to the Rails, Crakes, Gallinules and Coots of the World. Sussex, UK: Pica Press.

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One Response to Archived 2012-2013 topics: Tsingy Wood Rail (Canirallus beankaensis): newly recognised and Near Threatened?

  1. While habitat loss or modification probably isn’t the major threat to this species, the surface area of suitable habitat within its range is probably quite small as it only occurs in narrow canyons filled with forest. Thus the total population could be smaller than estimated. In addition the species is very vulnerable to hunting and except for a few areas that have significant tourist traffic (near Antranombazaha, the access point to Antsalova, and the southernmost portion of Bemaraha near Bekopaka) the reserve is not well patrolled or visited, so access for hunting is probably common or regular. In the north of the species’ range the pinnacle karst is known as a refuge for cattle bandits who usually live off animals they can catch in the vicinity such as birds and lemurs.
    When I visited Antranombazaha in 1998 the species was very wary of people suggesting that they were hunted. We encountered only two groups in a radius of ~3km from the camp in the forest.

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