Species Diversity, Population Structure and Population Densities of Birds in Southern African Grasslands

Grasslands occupy 24% of Earth’s surface and in most areas of the world are either destroyed, fragmented or converted into cultivated field. In Africa, their biodiversity is still insufficiently known. This study reports on the avian assemblages associated with grasslands in South African Highveld and Lesotho Drakensberg. Special attention was paid to the species richness, diversity, and population densities and dominance of particular species. Birds were counted by means of the Line Transect Method in three distinguished grassland types: Dry Cymbopogon-Themeda Grassland (transect length: 28 km), Wet Cymbopogo-Themeda Grassland (27 km) km, and Mountain Themeda-Festuca Grassland (31 km). In total, 86 bird species were recorded. While cumulative dominance was similar between the Dry and Wet Grassland (61-65%), these two were much different from that in the Mountain Grassland (46%). However the dominance index was similar in all three grassland types compared (0.25-0.33). Only one species, the Long-tailed Widow was a common dominant species for all three grassland types. African Stonechat, Wing-snapping Cisticola, Levaillant’s Cisticola and Yellow Bishp were dominant only in the Mountain Grassland; Northern Korhaan and the Clapper Lark - only in the Dry and Wet Grassland; Ostrich, Cloud Cisticola, African Quailfinch and Pied Starling – only in the Dry Grassland, while the Helmeted Guineafowl, Zitting and African Pipit – only in the Wet Grassland. Despite these obvious differences in dominance and population densities of species, Diversity and evenness indices were similar in all three grassland types. Shannon’s Diversity Index (H’) varied between 1.22 and 1.35; Simpson Diversity Index between 0.91 and 0.94, while Pielou’s dominance Index (J’) varied between 0.33 and 0.36. However, Sørensen Similarity Index between the three grassland types was low, ranging between 0.07 and 0.26. Proportions of ecological guilds were similar in the Dry and Wet Grassland, but differed from mountain Grassland. In comparison with other tropical grassland, avian communities in southern Africa are characterized by higher species richness and higher its variance between particular grassland types.