Justification of Red List Category
This species occurs in a small range. The total population is small, and ongoing degradation and loss of wetland habitats are leading to population declines. The species is therefore listed as Vulnerable.
The species is localised, but fairly common in suitable habitat (Taylor and Sharpe 2020). Based on an observed population density of 68 individuals/km2 at Laguna de Tota and under the assumption that 50% of the remaining habitat is occupied, the total population has been estimated at 5,600 individuals (Renjifo et al. 2016). This roughly equates to 3,700 mature individuals.
The population structure has not been investigated. It is hypothesised that the species forms several subpopulations separated by mountain ranges (Fundación ProAves in litt. 2020; L. Rosselli and F. G. Stiles in litt. 2020), though this requires confirmation (see Renjifo et al. 2016; Taylor and Sharpe 2020). Based on the spatial spread of sites with high concentrations of the species, it is here tentatively assumed that the species forms five subpopulations, the largest of which may well number below 1,000 mature individuals.
The species is undergoing a population decline as suitable habitat within its range is destructed and degraded; it has disappeared from some localities that were formerly occupied (Renjifo et al. 2016; L. Rosselli and F. G. Stiles in litt. 2020; Taylor and Sharpe 2020). Observational data suggests that the population is experiencing steep declines of up to 40% over ten years in some wetlands (L. Rosselli and F. G. Stiles in litt. 2020), in other wetlands the population seems to remain stable (Fundación ProAves in litt. 2020), while in others it fluctuates or even increases over time (Novoa Salamanca 2014). Fundación ProAves (in litt. 2020) have placed the overall decline in the band 10-19% over ten years, but to account for varying trend estimates and more rapid declines in some areas, it is precautionarily assumed that the rate of decline may be steeper than this. It is thus here placed in the band 10-29% over ten years.
Rallus semiplumbeus occurs on the Ubaté-Bogotá plateau in Cundinamarca and Boyacá in the east Andes of Colombia. The race peruvianus of Peru is only known from its type material, collected in 1886, and is probably extinct (del Hoyo et al. 1996). The species has been recorded at over 150 localities in montane and páramo wetlands and lakes (Fundación ProAves in litt. 2020). Notable sites include Laguna de Tota, Laguna de la Herrera, Parque La Florida, Conejera Marsh and Laguna de Fúquene (Lozano 1993; F. G. Stiles in litt. 1999; Renjifo et al. 2016).
The species occurs in the temperate zone, at 2,500-4,000 m (occasionally as low as 2,100 m), in savanna and páramo marshes. Characteristic wetland habitats are fringed by dense, tall reeds, bulrushes and vegetation-rich shallows (F. G. Stiles in litt. 1999). It appears to be particularly associated with tall reeds, preferring Schoenoplectus californicus, Typha, Juncus and two other aquatic plants, Limnobium laevigatum and Eichornia crassipes (O. Cortes in litt. 2007; Renjifo et al. 2016; Pérez-Guevara and Botero-Delgadillo 2020; L. Rosselli in litt. 2020). The species survives in small patches of habitat; already wetlands as small as 0.5 ha are probably suitable for breeding (Fundación ProAves in litt. 2020; Taylor and Sharpe 2020). It has occasionally been reported from heavily degraded wetlands and even small streams in the city of Bogotá (Fundación ProAves in litt. 2020). It uses flooded pasture and small overgrown dykes and ponds, but probably not for breeding (Fjeldså 1990, P. Salaman in litt. 1999). It feeds primarily on aquatic invertebrates and insect larvae, but also takes worms, molluscs, dead fish, frogs, tadpoles and plant material. Breeding probably takes place year-round (Taylor 1996; Renjifo et al. 2016). Nests have been found in Schoenoplectus and Typha beds adjoining shallow water (F. G. Stiles in litt. 1999).
Bogota Rail is heavily threatened by the loss and degradation of its habitat through drainage of wetlands, agricultural encroachment and subsequent pollution by effluents and agrochemicals (Lozano 1993; Renjifo et al. 2016; Taylor and Sharpe 2020). Drainage has caused massive habitat loss on the Ubaté-Bogotá plateau, and few suitably vegetated marshes remain because of pollution and siltation. All major savanna wetlands are seriously threatened, mainly by drainage, but also by agricultural encroachment, erosion, dyking, eutrophication (caused by untreated sewage effluent and agrochemicals), insecticides, tourism, hunting, burning, trampling by cattle, harvesting of reeds, fluctuating water-levels and increased water demand. The fringing habitat at Laguna de Tota has been reduced to less than 2 km2, and its continuing decay is reducing food availability (Varty et al. 1986). Laguna de la Herrera is affected by hunting, cattle trampling and irrigation schemes, and La Conejera Marsh and Laguna de la Florida are threatened by road construction and illegal settlement (Lozano 1993; P. Salaman in litt. 1999; F. G. Stiles in litt. 1999).
Predation of adults and nestlings by feral dogs, cats and rats is a further threat, but their impact on the population size is not known (Lozano 1993; O. Cortes in litt. 2007; Renjifo et al. 2016; Taylor and Sharpe 2020).
Conservation Actions Underway
The species occurs within Chingaza, Sumapaz and probably Cocuy Natural National Parks (Renjifo et al. 2016). 33 ha of La Florida wetland is part of a District Park (Loziano 2002). It further occurs in six protected urban wetlands in Bogota (L. Rosselli in litt. 2020), but many wetlands within the range are unprotected. A community-based monitoring programme has been established in the Laguna de Fúquene (Renjifo et al. 2016). The Bogota Rail Project, led by Humedales de Bogotá and Bogotá Birding, is carrying out awareness-raising campaigns in schools (O. Cortes in litt. 2020). Environmental education workshops for local schoolchildren are being held in the Tota and Fúquene areas (Renjifo et al. 2016).
25 cm. Very vocal, medium-sized rail. Slate-grey sides of face to belly, with pale throat and black flanks, coarsely banded white. Dull olive-brown streaked black above, with dull rufous shoulders. Conspicuous dull red bill and legs. Similar spp. Differs from sympatric rails in grey underparts, and red bill and legs. Voice Loud, sharp, piercing peep, and rapid, short chattering when alarmed.
Text account compilers
Benstead, P., Botero-Delgadillo, E., Cortés, O., Fundación ProAves, Khwaja, N., Pilgrim, J., Rosselli, L., Salaman, P.G.W., Sharpe, C.J., Stiles, F.G. & Symes, A.
BirdLife International (2022) Species factsheet: Rallus semiplumbeus. Downloaded from http://www.birdlife.org on 21/01/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/01/2022.