Diversity and distribution of birds in villages in the Kalahari
Van Rooyen, Neil David
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Urbanisation and human settlements affects natural habitats in South Africa and around the world through the removal of vegetation, construction of roads and houses, and by various forms of pollution. The Bophirima District of the North West province is a desert margin area - a fragile ecosystem facing the threat of desertification and land degradation. The area has a high diversity of bird species, but is also an area where small villages and human settlements are continuing to modify the natural environment. To determine the effect of urbanisation in a desert margin area, bird surveys were done in three of these settlements. Three habitat types were present at each village - natural, edge, and village habitat. The structure within the villages consisted of unpaved roads, small houses, and several other small buildings. Data was collected in and around the villages by plotting out evenly-spaced point count sites on a 250 x 250 m grid across each village, covering all three habitat types. Bird species were identified, and the number of individuals per species was recorded at each site over four surveys. Surveys were done with the expectation that bird numbers and species richness would be higher within the villages, as predicted by the "intermediate disturbance hypothesis". Bird numbers and species diversity were expected to decrease toward the edges and outskirts of the villages, where the opportunities created by urbanisation were missing. Different guilds were also expected to show different responses to urbanisation and habitat change. Geostatistical analyses, analyses of variance (ANOVA) and an indicator species analysis was performed. The results did indeed indicate that urbanisation increased the overall species richness and number of birds. The reasons for this can be attributed to an increase in additional food and water sources within the villages, as well as the availability of nesting sites, shelter and perches created by buildings, rooftops, poles, fences and other man-made structures. At the edges of the village and in the surrounding habitat, bird numbers and species diversity were often significantly lower, probably due to the absence of these man-made structures and anthropogenic resources. In terms of feeding guilds, an increase in granivores was observed within the villages, while insectivores and carnivores showed higher abundances in the natural habitats. Nesting guilds which responded positively to urbanisation were tree- and structure-nesters, while ground- and shrub-nesters preferred the natural habitats. It was concluded that bird distribution was very much affected by areas where their food and nesting requirements could best be fulfilled. In a desert margin area, where avian diversity is currently threatened by global warming and land degradation, these villages could serve as important conservation sites for birds. Several questions still need to be answered through future research, but it is recommended that proper management strategies and sustainable development plans are implemented to ensure the maintenance of species richness and bird numbers in such villages.
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