Data Zone
Justification of Red List category
This species is very poorly known. Following a review of available evidence (Berryman and Boakes 2023), the species is determined to be known from just eight specimens, collected in an eight-year window between February 1894 and April 1902 in the Bornean Central Highlands. These specimens are known from only three localities, one of which is imprecisely known. With more than 120 years since the last sighting, despite some moderate search effort, it is possible that this species is very rare. However, its sole congener is known to be highly elusive, and the area of potentially suitable habitat on Borneo is vast, poorly surveyed and often remote; it may consequently have a large population that is impervious to possible threats. Given the litany of uncertainties regarding this species' population size, trend and range, determining its relative extinction risk is currently not possible. Accordingly, it is listed as Data Deficient.
Population justification
Entirely unknown. Berryman and Boakes (2023) determined that the species has not been seen since 1902 (contra Orenstein et al. 2010, Eaton et al. 2021), despite moderate effort at localities from which was collected and/or is likely to occur; consequently, its population may be small. However, the same authors also identified that, if like R. longirostris, it is extremely elusive, it could simply have very low detectability and/or have strict habitat requirements that have not yet been identified. Given that a large area of suitable habitat remains, its population may, in fact, be very large. In the absence of even cursory data, qualitative and quantitative estimations of this species' abundance are not possible.
Trend justification
With no confirmed sightings for more than 120 years (see Berryman and Boakes 2023), there are no available data on population trends. Plausible threats for this species include logging and hunting, however whether these are causing ongoing declines is totally unknown.
Enigmatic. Rhizothera dulitensis is likely to be endemic to the Bornean Central Highlands, although its distribution within this is unknown. Berryman and Boakes (2023) reviewed the evidence for the species' occurrence at the four localities often listed for it (e.g. by Mann 2008, Eaton et al. 2021): Mt. Dulit, Batu Song and Mt. Murud (all in Sarawak), and Mt. Kinabalu (Sabah; Davison 2008). They determined that only Mt. Dulit and Mt. Kinabalu could be considered confirmed locations (specimens from these two sites span 1894 to 1898). Mt. Murud is almost certainly an error interpreted from the original label of a specimen collected in 1902 (see Berryman and Boakes 2023 for detail), and may refer instead to Murud Kecil. The origin of Batu Song as a locality is entirely obscure and not accepted here. In any instance, the species is known from only Malaysia, however Berryman and Boakes (2023) suggested that it probably occurs too in Kalimantan, Indonesia, given the contiguity of habitat spanning the central highlands. Claims from elsewhere are not upheld in the absence of evidence.
Unknown. The only available data on this species' ecology is that which can be inferred from labels of the eight known specimens. Berryman and Boakes (2023) interpreted these data and suggested the species occurs at 900–1,200 m, with a likely preference for good or primary forest (as with its sole congener).
Unknown, with no confirmed records since 1902. Hypothetical threats include logging (although this species' elevational range escapes the worst of Sundaic forest loss) and hunting, although Berryman and Boakes (2023) reported that where asked about the species, hunters in its range were not familiar with it.
Conservation and research actions underway
The species is included in the 'Search for lost birds' project by American Bird Conservancy, BirdLife International and Re:wild, supporting field expeditions to search for the species (Rutt et al. in prep.). No direct ongoing conservation action is known for this species. Several areas of ostensibly suitable habitat (including 7,000 km2 in Kayan Mentarang National Park, Kalimantan) are protected, but uncertainty with regards to this species' distribution makes conservation action difficult.
Conservation and research actions proposed
The action first needed for this species is its rediscovery (as outlined in Berryman and Boakes 2023). If and when it is rediscovered, determining its basic ecological tolerances (including its elevational span and habitat requirements) will be important, as will determining its true range. Population size and trend information is also needed, as is a determination of the threats impacting it, including the elucidation of whether selective logging and hunting is affecting it. A revised Red List assessment once these facets are known will allow for a more precise quantification of its extinction risk. Areas that are found to host the species should be protected and, if hunting is proven to be a key threat, discussions and negotiations with local communities should be undertaken to ameliorate its impact.
c. 37 cm. Long, fairly stout decurved bill, rufous face, broad grey band on throat and upper breast and clean white belly, upperparts brownish. Similar spp. Long-billed Partridge R. longirostris is similar but with rufous belly and greyish-rufous flanks, as well as whitish spots in the wing.
Text account compilers
Berryman, A.
Recommended citation
BirdLife International (2024) Species factsheet: Dulit Partridge Rhizothera dulitensis. Downloaded from
https://datazone.birdlife.org/species/factsheet/dulit-partridge-rhizothera-dulitensis on 26/12/2024.
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 26/12/2024.