Data Zone
Justification of Red List category
Caloperdix oculeus is listed as Near Threatened under Criterion A2cd+3cd+4cd. The species is widespread, but recent records suggest that it may have undergone a reduction in its range from loss of habitat, particularly in Sumatra and Peninsular Malaysia where it has disappeared from certain regions. The additional impacts of hunting which are expected to impact the species across its range suggest a reduction in the population of 10-29% over three generations.
Population justification
There have been no surveys which allow an estimation of the population size. The species occurs in several disjunct regions across its range and is patchily distributed (Eaton et al. 2021, McGowan et al. 2023). It is apparently widespread on Peninsular Malaysia (Puan et al. 2020), but scarce in Thailand (Madge and McGowan 2002, McGowan et al. 2023) and Borneo (Mann 2008) and rare on Sumatra (McGowan et al. 2023). The species was known from 32 localities in 1997 (McGowan et al. 1998), but its range may have contracted in response to habitat pressures. The species now appears to be extinct outside of national parks on Sumatra (Boakes et al. 2018), and recent records across Peninsula Malaysia and Thailand suggest it is now incredibly rare in the centre of the peninsula, and likely only occurs in isolated areas in the north and south (eBird 2024). The overall area of habitat remains rather large however, particularly on Borneo, and it is likely that the global population size of this species remains rather large.
Trend justification
Forest loss in the Sundaic region is widespread, caused by a combination of selective logging, subsistence farming, and larger scale plantations (BirdLife International 2001). Within the current range of C. oculeus, 14.5% of forest cover has been lost between 2000 and 2023, equating to a suspected 9-11% reduction in the population in the past three generations (Global Forest Watch 2024, based on data from Hansen et al. [2013] and methods therein). This rate likely underestimates population declines however, as the range of the species appears to have contracted in recent years. The species was considered widespread in Sumatra, but has not been seen outside of protected areas since 1991 (Boakes et al. 2018). Similarly, the species has not been recorded in the central regions of the Malaysian/Thai peninsula since the 1990s (eBird 2024), an area which has suffered from considerable forest loss (Global Forest Watch 2024). The species is now more often found on hillslopes in Malaysia, which is likely due to the loss of suitable habitat at lower elevations (Madge and McGowan 2002). A similar process has likely occurred in Borneo, where the species is found only at higher elevations between 1,000 and 1,200m (Mann 2008, Puan et al. 2020) and the forest loss in the lowlands immediately surrounding its Bornean range is considerable (Global Forest Watch 2024). Although the species appears to have some tolerance for degraded habitats, occurring in secondary regrowth forest and scrub (McGowan et al. 2023), its disappearance from areas in Sumatra (Boakes et al. 2018), Malaysia, and Thailand (Madge and McGowan 2002, eBird 2024), suggest it has a specific niche that is being lost, or the continued fragmentation of habitat has reached a critical point in some these areas.
It is also likely that hunting and trade is compounding rates of population decline. It is used for local consumption in Borneo (Supiandi et al. 2021) and hunting is apparently widespread in Thailand (McGowan et al. 2023). The species has also appeared in low numbers in market surveys on Sumatra (Shepherd 2006).
Considering the additional range reductions, along with hunting impacts (Supiandi et al. 2021, McGowan et al. 2023), a reduction in the population over three-generations of 10-29% is suspected.
Furthermore, declines are expected to continue into the future. Habitat modelling based on climate change and socioeconomic scenarios project a 77-99.9% chance of extirpation in Thailand by 2070 (Pomoim et al. 2022), and a c. 50-80% reduction in suitable habitat across its entire range by 2100 (Namkahn et al. 2022). Further research is required on the habitat requirements, disturbance tolerances, and population size and distribution of the species to fully understand the future risk of declines under climate change, but these projections suggest a high likelihood of additional habitat loss over the next three-generations for the species.
Caloperdix oculeus occurs in south-eastern Myanmar and Thailand, northern Sarawak, eastern Sabah, and Peninsula Malaysia, and Sumatra and Kalimantan, Indonesia (BirdLife International 2001, McGowan et al. 2023). Appears scarce across its range (BirdLife International 2001, McGowan et al. 2023) but little is known about its population size and distribution, and the species potentially occurs in under-surveyed areas throughout its range.
The habitat of C. oculeus varies across its range. Typically, it is found in both primary and secondary evergreen and semi-evergreen forest up to 1,200 m (Wells 1999, Eaton et al. 2016), but has been found up to 1,375 m (Sheldon et al. 2013). Its habitat is typical of this description on the Thai-Malay Peninsula, but on Borneo it is found in montane forest on hillsides and sandy valley bottoms in highlands between 1,000 and 1,200 m (Mann 2008, Puan et al. 2020), and in Thailand it is also found in bamboo regrowth generally up to 915 m (Treesucon and Limparungpatthanakij 2018). It appears to have tolerance for degraded habitats, as secondary regrowth scrub is apparently its main habitat on Sumatra, occurring in hills and low mountains from 150-1,000 m (van Marle and Voous 1988, Madge and McGowan 2002, McGowan et al. 2023).
C. oculeus has some tolerance for degraded habitats, occurring in secondary regrowth forest and scrub (McGowan et al. 2023). Regardless, forest loss in the Sundaic region is widespread, caused by a combination of selective logging, subsistence farming, and larger-scale plantations (BirdLife International 2001). Presumably, forest loss has led to some reduction in the range of the species, as it has not been seen outside of protected areas on Sumatra since 1991 (Boakes et al. 2018), and recent records suggest the species may have disappeared from the centre of the Thai-Malay Peninsula (eBird 2024). Forest and other anthropogenic pressures in the lowlands of Malaysia has likely caused the species' range to retract to higher elevations where suitable habitat is intact (Madge and McGowan 2002).
The species may also suffer a significant reduction in range by the end of the century as a result of shifting habitat due to climate change. There has been a projected 77-99.9% chance of extirpation in Thailand by 2070 based on optimistic and pessimistic climate change projections (Pomoim et al. 2022), and a c. 50-80% projected reduction in suitable habitat across its entire range by 2100 using several climate change and socioeconomic scenarios (Namkahn et al. 2022). Further research is required on the habitat requirements, disturbance tolerances, and population size and distribution of the species to fully appreciate the future risk of declines under climate change.
There is also likely a reasonable decline as a result of the trade and hunting of the species. It is used for local consumption in Borneo (Supiandi et al. 2021), and hunting is widespread in Thailand (McGowan et al. 2023). The species has also appeared in low numbers in market surveys on Sumatra (Shepherd 2006).
Conservation Actions Underway
CITES Appendix III in Malaysia. Known from several protected areas in all countries where it occurs, including Kaeng Krachen and Thaleban National Parks in Thailand, Taman Negara National Park in Malaysia, and Gunung Leuser and Kerinci Seblat National Parks on Sumatra (McGowan et al. 2023).
23-27 cm, distinctive with a bright rufous head and underparts, black mantle and flanks with white scallops, and olive-brown wings with large black spots. Dark brown bill and iris. 11 primaries (including remicle), curved secondaries, and 14 tail feathers. It is eutaxic. Feathers have a long aftershaft. Down is on apteria only. Sexes are similar in all plumages (but females have 0–1 yellow tarsal spurs compared to 1–2 in males). Sounds: Song a series of gradually accelerating and ascending whistles, subsequently bursting into several harsher notes, e.g. “wee-we-we-wi-wiwiwiwiwiwi.. kee-crrow..kee-crrow..kee-crrow”.
Text account compilers
Richardson, L.
Contributors
Taylor, J., Mahood, S. & Benstead, P.
Recommended citation
BirdLife International (2024) Species factsheet: Ferruginous Partridge Caloperdix oculeus. Downloaded from
https://datazone.birdlife.org/species/factsheet/ferruginous-partridge-caloperdix-oculeus 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.