Drivers of Bird Species Richness within Moist High-Altitude Grasslands in Eastern South Africa

Abstract

Moist high-altitude grasslands in South Africa are renowned for high avifaunal diversity and are priority areas for conservation. Conservation management of these areas conflicts with management for other uses, such as intensive livestock agriculture, which requires annual burning and leads to heavy grazing. Recently the area has become target for water storage schemes and renewable electricity energy projects. There is therefore an urgent need to investigate environmental factors and habitat factors that affect bird species richness in order to optimise management of those areas set aside for conservation. A particularly good opportunity to study these issues arose at Ingula in the eastern South African high-altitude grasslands. An area that had been subject to intense grazing was bought by the national power utility that constructed a pumped storage scheme on part of the land and set aside the rest for bird conservation. Since the new management took over in 2005 the area has been mostly annually burned with relatively little grazing. The new management seeks scientific advice on how to maintain avian species richness of the study area. We collected bird occurrence and vegetation data along random transects between 2006 and 2010 to monitor the impact of the new management, and to study the effect of the habitat changes on bird species richness. To achieve these, we convert bird transect data to presence only data to investigate how bird species richness were related to key transect vegetation attributes under this new grassland management. First we used generalised linear mixed models, to examine changes in vegetation grass height and cover and between burned and unburned habitats. Secondly, we examined how total bird species richness varied across seasons and years. And finally we investigated which habitat vegetation attributes were correlated with species richness of a group of grassland depended bird species only. Transects that were burned showed a larger decrease in vegetation cover compared to transects that were not burned. Grass height increased over time. Bird species richness was highest in summer compared to other seasons and increased over time. Overall bird species richness increased over the three summer surveys but species richness of birds that prefer heavily grazed habitat showed little change over the three years. Changes in bird species richness were best explained by the model with grass height for combined species richness of grassland depended birds but also for birds that prefer heavy grazing when treated alone. On one hand birds that prefer moderate grazing were best explained by a null model. However, overall bird species richness was better positively correlated to grass height than grass cover or dead grass. We conclude that frequent burning alone with relatively reduced grazing led to higher but less dense grass, which benefited some species and disadvantaged others. We suggest that management of this grassland use combination of fire and grazing and leave some areas unburned to acc...

Management factors affecting densities of common grassland birds of high elevation grasslands of eastern South Africa: Ingula as a case study

“…In particular, South Africa's moist grasslands harbor globally significant biodiversity, supply essential ecosystem services, support crop and livestock, forestry and settlement, yet are poorly conserved (O'Connor and Kuyler 2009). This area also coincides with high avifaunal species richness, diversity and endemism (Maphisa et al 2016). As a result, a number of Important Bird and Biodiversity Areas (IBAs) have been proclaimed in the area (e.g.…”

“…It is the site of the Eskom Ingula Pumped Storage Scheme (Ingula or IPSS), the main purpose of which is to augment electricity to the national grid during periods of peak consumption demand (Maphisa et al 2016).…”

“…Regionally, fire is an important conservation management tool used both on private and state lands to make habitats suitable for birds (Parr and Chown 2003). In addition to heavy livestock grazing and other agricultural activities, this area is a target for energy development projects to meet growing human demand for electricity and water for consumption (Maphisa et al 2016).…”

“…Burning is the main management tool in agricultural lands and conservation areas in this region (Parr and Chown 2003). Some studies indicate that inappropriate use of fire and grazing leads to degradation of grasslands in this region (Maphisa et al 2009(Maphisa et al , 2016Little et al 2015a).…”

“…Summers coincide with breeding for most birds and is the period with the highest species richness in this area (Maphisa et al 2016). We used the following eight species: Cape Longclaw (Macronyx capensis), Wing-snapping Cisticola (Cisticola ayresii), African Pipit (Anthus cinnamomeus), African Quail Finch (Ortygospiza atricollis), Yellow-breasted Pipit (Anthus chloris), Red-capped Lark (Calandrella cinerea), Zitting Cisticola (Cisticola juncidis) and Common Quail (Coturnix coturnix).…”