Bird Species Diversity and Community Structure Across Southern African Grassland Types

Grasslands occupy 24% of the Earth’s surface. In most areas of the world these are either destroyed, fragmented or converted into cultivated fields. 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 Euplectes orix was a common dominant species for all three grassland types. African stonechat, wing-snapping cisticola Cisticola ayresii, Levaillant’s cisticola Cisticola tinniens and yellow bishop Euplectes capensis were dominant only in the Mountain Grassland; northern black korhaan Afrotis afroides and the eastern clapper lark Mirafra fasciolata—only in the Dry and Wet Grassland; ostrich Struthio camelus, cloud cisticola Cisticola textrix, African quailfinch Ortygozpiza atricollis and pied starling Spreo bicolor—only in the Dry Grassland, while the helmeted guineafowl Numida meleagris, zitting cisticola Cisticola juncidis and African pipit Anthus cinnamomeus—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 Evenness 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.