Indicators of Species Richness of the Raptor Guild of the Carnivore Community of Afro-Alpine Habitats in the Bale Mountains, Ethiopia

Indicator species may provide useful substitute for large scale surveys to monitor biodiversity. We conducted surveys in the Afro-alpine habitats of the Bale Mountains National Park (BMNP) with the objective of identifying indicators for the species richness of the raptor guild. Raptors were counted by scan sampling technique from a suitable vintage point. Three classes of 18 sample units grouped according to the variability of the moorland ecosystem in the magnitude of process variables important for raptor species richness were used in determining the indicator value of species as a function of their abundance concentration and the percentage of species occurrence per sample group. This procedure determined indicator values for all species in the resident raptor community. Comparison with randomly expected values demonstrated that only Aquila verreauxii and A. chrysaetos have indicator values that were significantly larger than the randomly expected values. The species richness estimated using the abundances of these two species predicted the observed species richness of the whole community in a linear regression model that explained 66% of the deviance in the data set. Furthermore, the species richness of the community predicted by process variables had correlation of very high significance with that predicted by the indicator species. We have thus identified two indicator species to a raptor guild of the BMNP and demonstrated that these two species encapsulated most of the information regarding the species richness response of the guild to key process variables in the Afro-alpine moorland ecosystem. Our findings contribute significantly to current and future efforts of monitoring the biodiversity of the park providing a cheap and quick means of data generation relevant for making management decisions.