Open image gallery
The Orange Ground Thrush Zoothera gurneyi is restricted to scattered fragments of Afrotropical forest in South Africa and Swaziland. Within the region the species is suspected to have undergone a population decline which, together with an AoO less than 2 000 km2, means that it approaches the thresholds for the criteria for regionally Vulnerable.
The Orange Ground Thrush has a wide but highly fragmented Afrotropical distribution extending from the Democratic Republic of the Congo to South Africa. An isolated population occurs in the highlands of Angola (Mills et al. 2011). Within the region, it is found in Afromontane forests from the Soutpansberg in Limpopo Province, through KwaZulu-Natal and as far south as the Amatola Mountains, Eastern Cape. In Swaziland it is known only from Mgwayiza Forest in Malolotja Nature Reserve (Boycott and Monadjem 1998). The species is largely sedentary, with local seasonal movements possibly dictated by soil moisture and related prey availability (Earlé and Oatley 1983). The bird is suspected to undertake altitudinal migrations (Quickelberge 1989), although Oatley (2005) makes mention that these movements may be ascribed to juvenile dispersal or drought conditions. The EoO provided by SABAP2 is 23 7089 km2 which represents a decrease of 5.7% since 1997. The AoO has decreased from 24 624 km2 to 14 379 km2, a decrease of 41% between reporting periods. Significantly, forest vegetation types covered only 10.9% of the pentads including the species, meaning that the actual AoO is closer to 1 564 km2.
The global population size has not been quantified, but the species is reported to be scarce to locally common (Urban et al. 1986). A density of 4 pairs/4.5 ha has been recorded in prime habitat (Earlé and Oatley 1983). The regional population is estimated to be in the region of 5 000 mature individuals. The size of the Swaziland population is unknown but unlikely to exceed 40 pairs (Monadjem et al. 2003). Confidence in this regional population estimate is low.
The global population is suspected to be in decline due to habitat loss but the rate of decline is unknown (BirdLife International 2014). In the absence of regional population estimates it is not possible to obtain an accurate regional population trend. An examination of the change in regional AoO (41%) and assuming that, for a habitat-restricted species, a decline in AoO would be mirrored by a population decline, indicates that the regional population may be in decline. It is not know whether this decline exceeds the 30% threshold to quality this species as Vulnerable. Confidence in this regional population trend is medium.
Habitat loss is the primary threat to this species, particularly as it is highly localised and naturally restricted to a geographically limited vegetation type. Trampling and grazing by livestock entering forests is considered to be lesser threat (Allan 2000). Through their dung, hides and hooves, livestock animals also introduce weeds and pioneer plants along forest clearings and pathways; it is thought that establishment of a dense, weedy understorey layer will be detrimental to the Orange Ground Thrush and other terrestrial forest insectivores. Additionally, animals may create additional paths and serve to open up the forest, which allows more sunlight to penetrate to the forest floor and exacerbates the establishment of a dense understorey devoid of leaf-litter. Additional threats to indigenous forests include degradation through clearing for cultivation, harvesting of forest plants for traditional medicine purposes, and removal of wood for fuel or building materials. Indigenous forest corridors may be damaged during harvesting of adjacent alien commercial plantations (Allan 2000). Swaziland's Mgwayiza Forest, despite being located within a protected area, is facing threats from mining (Monadjem et al. 2003).
The species protected under the Swaziland Game Act but otherwise no species-specific conservation measures are currently underway.
The ongoing protection fragmented patches of Afromontane Forest distributed along the south-eastern and Eastern Escarpment is essential for the protection of this species. Many of the forests where it occurs are nominally protected, and a full review of its conservation status is recommended.
* Conduct surveys of all forest patches that supports this species to obtain accurate estimates of population size and occurrence densities. Territory mapping based on singing males in accessible parts of forests may be a practical way of estimating population sizes.
* In particular, the isolated forests in Eastern Cape should be surveyed (also for Spotted Ground Thrush G. guttata).
* The Orange Ground Thrush is adaptable to large gardens adjacent to indigenous forests, where it becomes habituated to man; if such artificial sites are managed in accordance to the species' ecological requirements, they may prove valuable for research and conservation.