EFFECTS OF LAND-USE AND TSETSE-FLY CONTROL ON BIRD SPECIES RICHNESS IN SOUTHWESTERN ETHIOPIA

Successful control of tsetse (Glossina spp.)-transmitted trypanosomias is in the Ghibe Valley, Ethiopia, appears to have accelerated conversi on of wooded grassland into cropland. Land conversion, in turn, may ha ve fragmented wildlife habitat. Our objective was to assess the influe nce of the expansion of agricultural land-use, brought about by tsetse control, on ecological properties by using bird species richness and composition as indicators of environmental impacts. We sampled bird sp ecies richness and composition (using Timed-Species counts) and habita t structure (using field sampling and remote sensing) in four land cov er/land-use types in areas subjected to tsetse fly control and adjacen t areas without control. At the height of the growing season bird spec ies numbers and vegetative complexity were greater in the small-holder , oxen-plowed fields and riparian woodlands than in wooded grasslands or in large-holder, tractor-plowed fields. Species composition was hig hly dissimilar (40-70% dissimilarity) comparing among land-use types, with many species found only in a single type. This implies that trypa nosomiasis control that results in land conversion from wooded grassla nds to small-holder farming in this region may have no adverse impacts on bird species numbers but will alter composition. These results als o suggest that moderate land-use by humans (e.g., small-holder field m osaics) increases habitat heterogeneity and bird species richness rela tive to high levels of use (e.g., tractor-plowed fields). Tsetse contr ol may be indirectly maintaining species richness in the valley by enc ouraging the differential spread of these small-scale, heterogeneous f arms in place of large-scale, homogeneous farms. Nevertheless, if the extent of small-holder farms significantly exceeds that of present lev els, negative impacts on bird species richness and large shifts in spe cies composition may occur.