Threatened species of South Africa’s Moist Highland Grasslands
South Africa’s grasslands comprise around 16.5% of the country’s land surface and are one of the most threatened ecosystems, with more than 33% irreversibly transformed and only 2.7% formally protected. This threatened biome hosts a multitude of rare, threatened and/or range-restricted species, with two such species being the Yellow-breasted Pipit Anthus chloris and Rudd’s Lark Heteromirafra ruddi. Each species is the focus of studies based at the Fitz.
Yellow-breasted Pipits are restricted to well-managed grasslands along the eastern escarpment of South Africa marginally entering eastern Lesotho and western Swaziland. Concerns that this species’ total population size and range are decreasing resulted in a study to investigate the drivers of any decline. Darren Pietersen, a PhD student at the University of Pretoria supervised by Andrew McKechnie, Ray Jansen and Ian Little, is employing a multi-faceted approach to determine the current distribution and status of Yellow-breasted Pipits in southern Africa, as well as investigating potential sources of decline. Darren and the team conducted bird- and plant community surveys, together with veld condition assessments, at 46 sites spanning the known and potential distribution of this species. These data are being used to assess the habitat preference of this species across its range, as well as assessing the feasibility of using bird community assemblages (and Yellow-breasted Pipits in particular) as a rapid-assessment indicator of Moist Highland Grassland ecological integrity. To determine the distribution of Yellow-breasted Pipits, verified sightings were combined with our records. The resultant database was combined with appropriate climatic variables and analysed in Ecological Niche Modelling software to predict the species’ potential range. The results suggest that the species is occupying most of its potential range, at least at the macro-scale, and that the main drivers of this species’ occupied range are occurring at the local scale (specifically grazing and burning regimes, confirming the results of previous studies).
The patchy occurrence of Yellow-breasted Pipits has raised concerns about the genetic diversity of this species and whether there is still gene flow between its fragmented populations. To address these questions, we sequenced DNA from the three main populations and will soon be subjecting these data to population genetics analyses. Lastly, to investigate the possibility that Yellow-breasted Pipits are a taxonomically ancient (basal) lineage that may have adapted to a climate and habitat that are receding due to a changing environment (both naturally- and anthropogenically induced), we are also elucidating the taxonomic placement of Yellow-breasted Pipits within the Motacillidae. As a spin-off of this study, we are also hoping to present a robust phylogeny of the sub-Saharan Motacillidae. Although this aspect is still ongoing, initial analyses suggest that some taxonomic changes may be required.
Rudd’s Lark was the focus of Wesley Gush’s CB MSc project, supervised by Claire Spottiswoode, David Maphisa and Paul Donald. Wesley’s research aimed to test whether the species has declined in one of its population strongholds, the Wakkerstroom area, and if so why. Wesley found both lower numbers of Rudd’s Larks and a lower probability of encountering Rudd’s Larks, compared to an identical survey conducted by David Maphisa in 2002–2004. Some previously suitable grassland habitat has been lost through conversion to crops, although the species has also declined within the remaining area of grassland habitat. The specific drivers of this decline remain unclear given that changes in grassland structure detected between 2002 and 2016 did not correspond with the Rudd’s Lark’s observed habitat selection. Taken together, these findings are concerning given that the Wakkerstroom area is considered to be one of the last remaining strongholds for the species, and may call its IUCN threat status of globally Vulnerable into question. A priority for future research will be to understand what limits Rudd’s Larks to its current pockets of occupancy within its remaining apparently suitable grassland habitat, and so to better inform rangeland management.
DST-NRF CoE grant; Clancey bequest; Endangered Wildlife Trust; Rufford Small Grants Fund; Tshwane University of Technology; Julian Francis.
Prof. Andrew McKechnie (U. Pretoria)
Prof. Ray Jansen (Tshwane University of Technology)
Dr Ian Little (Endangered Wildlife Trust)
Prof. Claire Spottiswoode (FIAO, UCT and U. Cambridge)
Dr David Maphisa (SANBI)
Dr Paul Donald (BirdLife International)
Students: Darren Pietersen (PhD, Pretoria), Wesley Gush (CB MSc, UCT)