Data Zone
Justification of Red List category
Polyplectron schleiermacheri is an elusive species, and there is much uncertainty over its ecology and status. However, severe deforestation of its lowland habitat suggest an absolute minimum reduction in its population of 25% over the past three-generations. However, the species suffers from a plethora of additional impacts. Severe fragmentation, habitat degradation, widespread hunting, and domestic and international trade are suspected to be seriously compounding declines in the population. A reduction in the population of 25-60% is precautionarily suspected to have occurred over the past three-generations, and the species is therefore listed as Endangered.
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).
Polyplectron schleiermacheri is endemic to Borneo, where it is known from Sabah, Malaysia and Kalimantan, Indonesia. The species may also occur in Sarawak, Malaysia, with unconfirmed records from steep slope forest Bario and Kapit near Nanga Gaat (McGowan and Garson 1995, Smythies 1999). The record from Bario is supported by a preserved tail feather definitely belonging to a peacock-pheasant and the Kaip record reportedly included one sighting of a female (BirdLife International 2001). With no other records from Sarawak since this time, the species' presence in this region is treated as uncertain.
P. schleiermacheri is thought to predominantly occupy primary lowland forest on alluvial soils, preferring forested ridges, below 1,000 m (Mann 2008). Confirmed records stem from secondary and primary forest along rivers, hill forest, and temporarily dry swamp forest, preferring alluvial soils (BirdLife International 2001).
However, there is uncertainty in the species' habitat preferences. GIS analysis based on interview data suggest the species only occurs on lowland plains and forests with fertile soils, not occupying hill or mountain forest (O'Brien et al. 1998), however the methodology and interpretation of results from this study have been criticised (Sözer et al. 2000). Further, surveys for the species in Sungai Wain Protection Forest in east Kalimantan from 1997-2002 recorded the species in alluvial, swamp, slope, high-flat and ridge forest, but most often in high-flat and ridge forest (Fredriksson and Nijman 2004). This study considered the species as sedentary but highly elusive, only being sighted on seven occasions during the study period. Additionally, camera trap records from Kuamut Forest Reserve, Sabah, recorded up to three birds from previously logged forest (Mohamed et al. 2017). Therefore, previous suggestions of habitat associations for this species may be biased from the patchiness of records, rather than representing a true preference of the species.
The species produces only a single egg per clutch and consequentially has a low reproductive rate (Corder and Davison 2021).
As a lowland species, the primary threats for P. schleiermacheri are deforestation and habitat degradation (McGowan and Garson 1995, Mann 2008). The loss of lowland forests on Borneo, particularly those on alluvial soils which the species seems to prefer (Mann 2008), are continually being cleared and degraded due to logging and, more significantly, the planting of oil-palm and rubber plantations (Descals et al. 2021, Wang et al. 2023). Although there is some uncertainty regarding the habitat type this species prefers, interviews with locals suggest the species is never found in agricultural land and as this increasingly becomes the dominant land-type on Kalimantan, declines in the population are expected to follow (O’Brien et al. 1998, Savini et al. 2021). Several areas where the species has been historically recorded have been either completely cleared, or partially logged (O’Brien et al. 1998). Habitat is also lost because of severe forest fires, which can disproportionately impact logged forests (Siegert et al. 2001). Particularly, after droughts in 1997-98, fire resulted in the loss of almost three quarters of primary forest within Sungai Wain Protection Forest (van Nieuwstadt 2002). It was estimated in 1997, using habitat maps and locality data from a range of sources, that the amount of suitable habitat for the species had decreased to 0.2% of the pre-1970 area, the most of any partridge or pheasant in the study (McGowan and Gillman 1997).
Habitat fragmentation is likely a concern for this species, given its inferred inability to disperse through unsuitable habitat (BirdLife International 2001, Simamora et al. 2021). Considering the species also has a seemingly low population density, it likely exists in small and isolated populations (BirdLife International 2001). These factors suggest that with the continuing loss of habitat, the species will be increasingly susceptible to hunting, trade, and stochastic events (BirdLife International 2001). The loss of potentially breeding individuals is of particular concern as the species has a low reproductive rate (single egg clutches) which suggests that the consequentially slow rate of population increase (Corder and Davison 2021) may be unable to compensate for the loss of individuals from hunting and/or habitat loss.
The species is also impacted by subsistence hunting, but also to supply logging teams with meat (BirdLife International 2001, Mann 2008), and it is likely to be suffering from hunting everywhere it occurs (O’Brien et al. 1998, Fredriksson and Nijman 2004). A study in central Kalimantan interviewed locals in 50 villages (O’Brien et al. 1998), and almost all respondents suggested that the species is captured by snares, mostly for food, and 85% also believed that the population was declining (O’Brien et al. 1998). There are a few reports of both domestic (to Jakarta) and international (to Singapore) trade of the species (BirdLife International 2001), but observations in 2023 from online markets suggest this threat is continuing (A. Berryman pers. obs. 2024).
Conservation Actions Underway
CITES Appendix II. The species is known from Sungai Wain and Gunung Lumut Protection Forests, Gunung Palung National Park, Deramakot Forest Reserve (McGowan and Kirwan 2020), Danau Sentarum National Park (BirdLife International 2001), and Kuamut Forest Reserve (Mohamed et al. 2017). In Sungai Wain Protection Forest, commercially valuable trees around the exterior of the reserve have been spiked with steel nails, which has halted logging and illegal hunting as a result (Fredriksson and Nijman 2004). Additionally, there has been awareness and education work, alongside the establishment of a stakeholder management board, and the regeneration of recently burnt areas (Fredriksson and Nijman 2004).
Male c. 50 cm (tail c. 19–20 cm); female c. 35·5 cm (tail 15·5–18 cm). Rather small, relatively short-tailed peacock-pheasant. Male has throat and centre of breast pure white, and metallic blue-green sides of breast; upperparts more rufous than in P. malacense, with smaller ocelli and somewhat hair-like feathers on crown which can be elevated to form small, bushy, forward-leaning crest, while nape feathers can be fanned into short ruff. Female lacks spurs (two in male) and distinctive head markings, apart from white throat; more reddish than female P. malacense, with shorter tail; lacks ocelli on uppertail-coverts, and has smaller, ill-defined ocelli on rectrices. Bill and legs dark grey, bare skin around eye reddish, and irides pale bluish (male) or brown (female). First-year male is like adult female, but larger and brighter, with outer webs to flight feathers mottled and barred rufous and buff, and has vermiculated underparts. Juvenile apparently undescribed, although is presumably much like adult female. Sounds: song is a series of increasingly loud, harsh cackles, typical of Polyplectron, as well as a loud disyllabic crowing “kank kank”, with an almost quacking quality to it.
Text account compilers
Berryman, A., Richardson, L.
Contributors
Davison, G., Lambert, F., van Balen, B.S., Berryman, A., Benstead, P., Bird, J., Taylor, J., Ashpole, J, Keane, A. & Davidson, P.
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.