Data Zone
Justification of Red List category
This species is restricted to lowland forest in a region where this habitat-type is being cleared and degraded at a rapid rate. As such, rapid population declines are suspected, and the species is consequently listed as Vulnerable.
Population justification
The population size of this species has historically thought to have been small, although there is little evidence to support this. Singh et al. (2021) predicted that the area of suitable habitat for this species (in 2010) was c.45,000 km2. Even allowing for a substantial contraction in the area since then (thought to have been 20-35%), the area of habitat available to this species remains large: c.30,000-36,000 km2. On Palawan, one of the species' two congenerics, P. falcata, has been recorded at densities of 4.8 and 11.2 individuals/km2 in advanced secondary growth and old growth respectively (Mallari et al. 2011). Although the suitability of these figures for P. leucogrammica is ultimately unknown, eBird (2022) suggest the two species' have similar detectability. If the true density of P. leucogrammica lies somewhere between 5-10 individuals/km2, and the calculation made by Singh et al. (2021) is correct, the species likely still numbers in the hundreds of thousands, set here to 75,000-150,000 assuming approximately 50% occupancy.
Trend justification
Using a Maxent approach derived from climate and land-use layers with GBIF (2019) data, Singh et al. (2021) predicted that the area of suitable habitat for this species will fall by 66–71% between 2010 and 2050, equivalent to declines of 25–26% over three generations (10.5 years) if a linear decline is assumed. This rate of reduction is also supported by historic and future projections of remote-sensed forest cover data (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein), which suggest forest cover reduced by 23-25% in the three generations to 2021, with similar projected losses into the future based on data from between 2018 and 2021. Given this species' high forest dependence, these are considered the minimum rates of population loss. There is concern, however, that these reductions in habitat area do not necessarily fully account for threats in this species' decline. It appears to be intolerant of even moderate habitat degradation (Lambert 1992) such that selective logging is thought to impact it, as is the increasing fragmentation of suitable forest patches (Collar and Robson 2020). Overall therefore, it is plausible that population reductions exceed 30%, and this is accepted here with a likely rate of decline of 25-35% over three generations.
Ptilocichla leucogrammica is endemic to the island of Borneo where it occurs in Sabah and Sarawak, Malaysia, Brunei, and Kalimantan, Indonesia (BirdLife International 2001).
This species frequents lowland, tropical evergreen forest and sometimes peat swamp forest, ascending into the foothills locally to c.600 m. It is usually found in pairs on the ground in dark and shady understorey vegetation.
Forest destruction on Borneo has been extensive, for timber and conversion to agriculture. In particular the rapid expansion of oil palm has driven the conversion of the majority of remaining lowland forest in the region. Using a Maxent approach derived from climate and land-use layers with GBIF (2019) data, Singh et al. (2021) predicted that the area of suitable habitat for this species will fall by 66–71% between 2010 and 2050, equivalent to declines of 25–26% over three generations (10.5 years) if a linear decline is assumed. This rate of reduction is also supported by historic and future projections of remote-sensed forest cover data (Hansen et al. 2013, Global Forest Watch 2022), which suggest forest cover reduced by 23-25% in the three generations to 2021, with similar projected losses into the future based on data from between 2018 and 2021.
Conservation Actions Underway
No species-specific action is known for this species. It occurs in numerous protected areas (Singh et al. 2021, UNEP-WCMC and IUCN 2022).
Conservation Actions Proposed
Survey lowland forest throughout Borneo to clarify the range, status and ecological requirements of this species, and assess the scale of threats that it faces. Formulate a management strategy for this species and a suite of other birds largely reliant on lowland forest in the Sundaic region. Promote the effective management of existing protected areas in this region and the expansion of the protected-area network. Lobby for reduced logging and sustainable logging practices throughout its range. Continue to monitor habitat loss using remote sensing data (e.g. Global Forest Watch 2022).
15 cm. Small, terrestrial, forest-dwelling babbler. Warm brown upperparts. White throat lightly scaled dusky, pale sides of head and supercilium mottled dusky. Rest of underparts blackish with broad white streaks. Short tail and pinkish, relatively long legs. Similar spp. Striated Wren-babbler Kenopia striata is smaller with pale streaks on upperparts and wholly pale underparts. Voice Song consists of two pure tone notes fii-fii.
Text account compilers
Berryman, A.
Contributors
Lambert, F., van Balen, B.S., Davidson, G., Benstead, P., Taylor, J., Allinson, T & Gilroy, J.
Recommended citation
BirdLife International (2024) Species factsheet: Bornean Wren-babbler Ptilocichla leucogrammica. Downloaded from
https://datazone.birdlife.org/species/factsheet/bornean-wren-babbler-ptilocichla-leucogrammica on 23/11/2024.
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 23/11/2024.