Current view: Data table and detailed info
Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
IUCN Red List criteria met and history
Red List criteria met
Red List history
| Migratory status |
not a migrant |
Forest dependency |
high |
| Land-mass type |
shelf island
|
Average mass |
- |
Population justification: There is very little exact information on the population size of the species. Recent records suggest that the species' is very rare, with only three records from Kuamut Forest Reserve in 2016 (Mohamed et al. 2017), and the only a single account by a hunter from 13 sites in the Kerangas (Woxvold and Noske 2011). However, the species has presumably always been difficult to detect, which may reflect low densities (McGowan and Kirwan 2020), but could also be attributed to its elusive nature, making it difficult to ascertain a true population size. Regardless, there have been some attempts to estimate the population size. Surveys in 1995-96 estimated 525-2,100 individuals in East Kalimantan and 2,450-9,800 in Central Kalimantan (Sözer et al. in BirdLife International 2001), but a revision of the population density based on trapping success rates estimated 20,427-81,618 individuals (Sözer et al. in BirdLife International 2001). However, this estimate is again revised to give 4,085-16,324 individuals when the population density is extrapolated only to forested areas where the species is known to occur (Sözer et al. in BirdLife International 2001). An additional estimate of 12,246-48,971 individuals is provided by extrapolating over a larger range (Sözer et al. in BirdLife International 2001). Although no population size was calculated, a 1996 study utilised interviews and questionnaires with locals from 97 villages across Central Kalimantan, with results suggesting the species may be more widespread (yet patchily distributed) than previously considered (O'Brien et al. 1998). However, there has been some contention over the methodology of this study (see Sözer et al. [2000] and Kinnaird and O'Brien 2000).
These population estimates, varying in the range and density figures used in the calculations, reflect the difficulties in estimating the population density when species' presence (and density) is highly uncertain. Furthermore, there is uncertainty over the species' exact habitat preferences and tolerances (e.g., see O'Brien et al. [1998], Fredriksson and Nijman [2004], and Mohamed et al. [2017]). Therefore, any attempts to extrapolate population densities to an area of habitat will be fraught with uncertainty. The estimates provided above fail to account for the species' presence in Sabah (Mohamed et al. 2017), but likely also overestimate the extent of occupied habitat. Taking into account that the species is thought to have declined since these previous estimates were made, a population of 5,000-25,000 mature individuals is suspected.
Trend justification: There are no population data from which to directly establish a trend in this species, but rates of forest loss in its range over the past three generations have been so rapid it is almost certain that it has declined rapidly in parallel. Savini et al. (2021) estimated that between 2000 and 2018, P. schleiermacheri lost 12.5% of suitable habitat; however, the underlying range map used to analyse these data interpreted the species as a mid-elevation species, an interpretation no longer believed to be correct on the pattern of available records (BirdLife International 2001, Mann 2008, Eaton et al. 2021, eBird 2024).
Across the entirety of its mapped range, 23% of forest cover was lost in the three generations (19.2 years) to 2024 (Global Forest Watch 2024, based on data from Hansen et al. 2013 and methods therein). However, despite substantial camera-trapping effort, there are very few recent records of the species in Sabah (Mohamed et al. 2017, Eaton et al. 2021, eBird 2024). The species evidently has a stronghold in extreme lowland (<200-300 m) alluvial forests in Kalimantan (O'Brien et al. 1998), where remote sensing data indicate a catastrophic reduction of c.33% in forest cover in the three generations to 2024 (Global Forest Watch 2024). The vast majority of this reduction in forest cover has been driven by the widespread conversion of Borneo's lowland forests to palm-oil and rubber plantations (Descals et al. 2021, Wang et al. 2023), where there is no evidence that this species can persist. Based on these two calculations, P. schleiermacheri is estimated to have declined by an absolute minimum of 25% over the past three generations. There are several reasons to believe, however, that rates of population decline may have been (perhaps substantially) more rapid than this minimum.
First, the remote sensing data used above makes no account for forest degradation and modification, which is known to be widespread on Borneo (see Grantham et al. 2020) but for which there is no reasonable way of quantifying the impact on the population of P. schleiermacheri. Second, habitat fragmentation, particularly on the periphery of this species' mapped range, is increasingly believed to be a problem for many species on Borneo (Simamora et al. 2021) with an inferred poor ability to disperse. While the impact on this species is ultimately unknown, given fragmentation is thought to be an acute problem for Galliformes more broadly (i.e. Savini et al. 2021), it is reasonable to infer that fragmentation may be compounding population declines. Third, hunting for local end-use was identified (O'Brien et al. 1998) as a plausibly significant threat in Kalimantan, with birds frequently reported by villagers as being hunted with snares. While it is inevitable that P. schleiermacheri will, to some extent, have been hunted on Borneo for centuries, the increasing human population and, perhaps more significantly, the increasing accessibility of forests driven by the expansion of Kalimantan's road network, mean that the overall hunting pressure on this species has likely increased over the past 2-3 decades. Fourth, there is some limited evidence of trapping of this species for the pet trade (BirdLife International 2001, A. Berryman pers. obs.). So intense are the pressures imposed on this species by hunting and trapping, that Symes et al. (2018) predicted a population reduction of c.48% over the past three generations because of trapping alone by assigning probability curves according to expert opinion on trade desirability in conjunction with accessibility (based on a distance to forest edge from remote sensed forest data).
The combined impact of these four threats, all of which are suspected to compound gross rates of forest loss, is unknown. However, comparing the extent of historical records identified in BirdLife International (2001) and Mann (2008) with recent records (e.g. Mann 2008, Boakes et al. 2020, Eaton et al. 2021, eBird 2024) reveals a substantial contraction in range far beyond that of forest cover loss alone, even when accounting for differences in survey effort.
Accounting for all identified threats (which do not operate independently), rates of population decline in this species over the past three generations (19.2 years: 2004-2023) are precautionarily suspected to lie in the band 25-60%. Future rates of decline are even harder to predict, but are suspected to be less (suspected here to fall in the bracket 10-49%) owing to slowing rates of deforestation in Kalimantan in recent years (2019-2023), driven chiefly by declining oil-palm expansion (Gaveau et al. 2022).
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
Recommended citation
BirdLife International (2024) Species factsheet: Bornean Peacock-Pheasant Polyplectron schleiermacheri. Downloaded from
https://datazone.birdlife.org/species/factsheet/bornean-peacock-pheasant-polyplectron-schleiermacheri on 23/12/2024.
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 23/12/2024.
