Justification of Red List Category
This rail qualifies as Vulnerable because it has a small population, which is likely to be undergoing a continuing decline and severe fragmentation owing primarily to habitat loss. However, recent records may in part reflect its reclusive nature and potentially wider distribution than previously thought. Further surveys are needed to clarify its status.
The population is estimated to number 2,500-9,999 mature individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 3,750-14,999 individuals, rounded here to 3,500-15,000 individuals. However, with recent observations on Buton of this species, it likely has a wider distribution than previously thought and so with further information this population estimate may be revised upwards.
This species is suspected to be in decline owing to forest loss, even within protected areas, as well as hunting pressure and predation by introduced species. However, a lack of robust survey data prevents an accurate estimation of its population trend.
Gymnocrex rosenbergii is known from Sulawesi and the nearby island of Peleng, Indonesia (BirdLife International 2001), and has recently been found on Buton (Martin et al. 2015). Specimen records and sightings suggest that it is relatively widely distributed and locally fairly common. However, it appears to have declined, and has probably disappeared from much of the Minahasa peninsula, and indeed lowland Sulawesi. Recent records derive from few localities, suggesting that it is now rare and local, although its retiring habits undoubtedly result in it being under-recorded. Its current status on Peleng (where it is known from just three specimens) is unknown.
It inhabits dense primary and old secondary tropical evergreen (sometimes relatively dry) forest, usually between 150 and 900 m. However, recent records from c.1,700 m suggest that its altitudinal range is broad. Records indicate a preference for thick understorey (comprising small saplings, palms, rattans and bamboos), forest streams and pools. It has also been encountered in dense, low forest/shrub regrowth on recently abandoned rice-fields. It is a very poor flier, and is therefore presumably largely sedentary. Its call is potentially a significant aid to detection.
The impact of extensive lowland deforestation on Sulawesi, as a result of land clearance for transmigration settlements, agricultural and infrastructure development and large-scale logging, is unclear. However, habitat destruction, degradation and fragmentation certainly pose the main threats to the species. In Indonesia new regional autonomy laws were passed in 1999 (and enacted in early 2000), which empower regional governments to determine the licensing of forest concessions and exploitation of natural resources. Unfortunately there has also been a significant increase in the amount of logging taking place in protected areas since decentralisation, especially in Sulawesi. The harvesting of rattan in the lower elevations of Lore Lindu National Park may be impacting the species (K. D. Bishop in litt. 2012). Its near flightlessness renders it vulnerable to predation, particularly by introduced predators (e.g. dogs), and hunting (using snares) may pose a local threat.
Conservation Actions Underway
It is known to occur in several protected areas, including Bogani Nani Wartabone, Lore Lindu and Rawa Aopa Watumohai National Parks, Gunung Klabat, Pengunungan Palu and Tangkoko DuaSudara and Gunung Ambang Nature Reserves (BirdLife International 2001, N. Brickle per T. O'Brien in litt. 2007); however, in recent years deforestation has continued both within and adjacent to protected areas in northern Sulawesi (T. O'Brien in litt. 2007).
30 cm. Medium-sized, secretive, forest rail. Conspicuous patch of bare cobalt-blue skin around eye. Black crown, underparts and tail, rufous upperparts and wings. Similar spp. Only other forest rail in range is Snoring Rail Aramidopsis plateni which is grey on mantle, face and breast, barred on flanks and lacks bare blue patch around eye. Hints Pursue or play-back any low resonant calls heard in forest undergrowth. Voice Snoring sound apparently similar to A. plateni. Also quiet clucking sound in alarm.
Text account compilers
Davidson, P., Westrip, J., Bird, J., Tobias, J., Taylor, J., Benstead, P.
Martin, T., Naliko, M., Bishop, K., O'Brien, T.
BirdLife International (2018) Species factsheet: Gymnocrex rosenbergii. Downloaded from http://www.birdlife.org on 11/12/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 11/12/2018.