Effects of livestock grazing on an Afromontane grassland bird community in the Bale Mountains of Ethiopia

Abstract

Livestock grazing has been considered to be one of the major causes for biodiversity degradation worldwide. In this study, we examined this effect on Afromontane grassland birds by comparing their diversity between ungrazed and grazed grassland sites in the northern Bale Mountains, Ethiopia. We counted birds and recorded vegetation height and cover along 28 (14 in each land-use type) 1 km transects. We used six different diversity measures (richness, evenness, Shannon diversity, taxonomic diversity and taxonomic distinctness) to express bird diversity and explored which of these measures better reveal the diversity pattern. Vegetation structure differed significantly between the two sites; the first two principal components accounted for 78% of the variation. Discriminant function analysis (DFA) showed bird diversity to differ significantly between the two sites; taxonomic diversity (Delta) contributed the most to the difference between the two sites, while species richness contributed the least. The results of ANOVA indicated that all diversity measures, except species richness, were significantly higher in the protected site compared to the unprotected site. In general, this study showed that grazing had negatively affected bird diversity in the study area and the use of taxonomic diversity measures had enabled us to reveal the impact better.