Data Zone
Justification of Red List category
This species has a small population which is thought to be declining due to ongoing habitat loss and degradation caused by land conversion and fires. It is therefore listed as Vulnerable.
Population justification
No records of this species exist between 1971 and 2005, when c. 10 individuals were recorded (seven birds were seen and another pair or group were heard) at Mts Moco and Soque (Mills et al. 2013). Surveys between 2005 and 2009 estimated that c. 75 pairs occur on Mt Moco (Mills et al. 2011). In 2010, a significant but unquantified population of individuals was discovered in the Namba Mountains, where the species was found to be fairly common, and which likely holds the largest population of this species (Mills et al. 2013). Individuals have also been recently recorded in Tundavala (eBird 2023), but it is not possible to quantify the population there based only on this information.
Overall, the global population has been estimated at between 462-1,050 pairs and 1,040-2,080 pairs, depending on the amount of forest cover left in Angola (M. Mills in litt. 2010, Mills et al. 2011). The latter is likely an over-estimate unless the species is tolerant of a wider range of habitats than is currently known, hence the global population is currently best placed in the band 1,000-2,499 mature individuals (M. Mills in litt. 2010). Further fieldwork is needed to improve the accuracy of the population size, but considering the small extent of suitable habitat present within the species' range and elevation limits (2,000-2,500 m), the species' population size is unlikely to be large.
Trend justification
The species is considered to be highly dependent on Afromontane forest edge habitat, specifically on forest edge undergrowth, and is only found in areas which contain, or are adjacent to Afromontane forest, and is therefore directly linked to its existence. The exception to this is on Mount Soque, where Afromontane forest has been completely lost; this area contained a remnant population of four pairs in 2005, using vegetation similar to that found in forest edge (e.g., dense scrub). This subpopulation is therefore likely to be non-functional and an extinction debt generated from the clearance of the forest.
Due to land use change for grazing and agriculture and forest fires, which may be exacerbated in the future by climate change, Afromontane forest, within the physically restricted elevation limits of the species (which is confined to the highland plateaux or 'sky islands'), is estimated to be undergoing a decline of approximately 11% over the species' past three generations (16 years), 19% between 2022 and 2037, and 15% over the next three generations (Powell et al. 2023, Global Forest Watch 2023, using Hansen et al. [2013] data and methods disclosed therein). Although it could be argued that forest loss would equate to higher areas of forest edge habitat, as most forest loss is artificial, it is considered unlikely that the edge undergrowth specific to this species' habitat would be able to establish and mature enough, and over a sufficient amount of time on average for the species to disperse and reproduce sufficiently to contribute to a stabilisation or increase in the population size before this habitat is yet again destroyed, either at the same place or somewhere else.
Considering the species' dependence on Afromontane forest edge habitat, the absence of a functional population where this habitat has been removed, and the continuing loss of this habitat through land conversion and fires, it can be inferred that the species is undergoing a continuing decline in population size, which may also be exacerbated by some hunting pressure (Dean 2001; M. Mills in litt. 2005, 2010). Due to the uncertainty of the severity of the impact on the species caused by the loss of its habitat, and the potential for additional impact from hunting pressure, the rate of this decline has not been quantified.
Pternistis swierstrai is endemic to western Angola and has been found from Tundavala in Huila District north to Cariango in Cuanza Sul District, on inselbergs in Huambo District and in the Bailundu Highlands (Dean 2000). On Mt Moco in the Bailundu Highlands, only c.15 patches of true Afromontane forest survive (1-15 ha), all in deep ravines (Dean 2001), although there are other more extensive patches of sub-montane forest in western Angola (M. Mills in litt. 2005, 2006, 2007, 2010). In 2010, a significant population of individuals was discovered in the Namba Mountains (Mills et al. 2013), and observations have been recently recorded from Tundavala (eBird 2023). No recent records of the species exist from Hanha, Mombolo or Cariango (Mills et al. 2011).
Habitat: It is found in montane areas where it is known mainly from habitats inside and adjacent to forest edge. In forest, it stays within the dense undergrowth of bushes, shrubs, grasses and large ferns, and in outside of forest edge in habitat similar to such undergrowth. In the Namba Mountains, which contains approximately 85% of the remaining Afromontane forest of southwest Africa, and where continuous forest patches are relatively large (26.4 ha on average), it has been recorded as fairly common in the forest edge and adjacent thickets, but was not recorded at all in the forest interior (Mills et al. 2013). Where patches of forest are smaller, such as on Mount Moco, it was very rarely recorded in forest patches of less than 1 hectare, and was recorded once as venturing into grassland adjacent to the forest (Mills et al. 2011). On Mount Soque, where all Afromontane forest has been lost, only four pairs remained in 2005, using the only suitable habitat left to them in the form of heavily vegetated and shrubby gullies and dense shrub around the mountain summit (Mills et al. 2011). It absence from very small woodland patches, and from the interior of large patches of woodland, as well as the very small remnant population on Mount Soque demonstrate the species' high dependence on Afromontane forest edge habitat. Diet: It feeds on grass and legume seeds and insects picked from the leaf-litter. Breeding: Its breeding ecology is virtually unknown, but juvenile specimens collected in August suggest a breeding season in May or June.
On Mt Moco, it is threatened by clearing and burning for subsistence farming and the remaining forest patches are disappearing rapidly (Dean 2001, Mills et al. 2011). Fires have also been recorded in the Namba Mountains during surveys between 2020-2022, both anthropogenic and naturally occurring, within the forest, with many hectares lost (Powell et al. 2023). Climate change is likely to exacerbate this threat, as dry conditions are becoming more common, and consequently fires more severe, and it is likely that the Afromontane forest habitat that the species depends on would not be able to persist if fires regularly occurred within it (Powell et al. 2023). Hunting may also be a problem in this area, although in August 2005 birds were recorded very near to the largest village (M. Mills in litt. 2005, 2006, 2007, 2010), and little evidence of hunting was recorded during surveys on Mt Moco between 2005-2009 (Mills et al. 2011).
Conservation Actions Underway
A protected area of c.60 km2 at Mt Moco was proposed in the 1970s, but has not yet been established (Huntley and Matos 1994).
33 cm. Black-and-white, terrestrial gamebird with red bill and legs. Adult male striking black-and-white with broad, black breast-band on white with black spotted underparts. Upperparts at closer range very dark brown. Female has similar underparts to male, but shows paler, more rusty back, mantle and upperwings. Voice Described as a cackling similar to Jackson's Francolin Pternistis jacksoni or Hildebrandt's Francolin P. hildebrandti.
Text account compilers
Rotton, H., Rutherford, C.A.
Contributors
Bird, J., Butchart, S., Calvert, R., Dean, R., Ekstrom, J., Keane, A., Mills, M., Shutes, S., Symes, A., Taylor, J. & Vaz Pinto, P.
Recommended citation
BirdLife International (2024) Species factsheet: Swierstra's Spurfowl Pternistis swierstrai. Downloaded from
https://datazone.birdlife.org/species/factsheet/swierstras-spurfowl-pternistis-swierstrai on 26/11/2024.
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 26/11/2024.