Aquatic bird species richness and distribution in relation to reservoirs' limno-chemistry in Tigray National Regional State, northern Ethiopia

Abstract

Summary 1. Knowledge of the relationship between biodiversity and environmental factors provides insight into patterns of species richness and distribution in limnetic ecosystems. To this end, this study was conducted to test the effect of limnological characteristics of reservoirs on bird species richness and distribution along an age gradient of limnetic ecosystems in Tigray National Regional State. 2. To evaluate the relationship between limnological characteristics of reservoirs and patterns of bird species richness and distribution, six physicochemical variables, three morph-edaphic and biological variables were recorded for 35 reservoirs and analyzed by multivariate statistical techniques. Species richness data was subjected to a multiple regression analysis at limnological variables, biological variables and age of the reservoirs in order to investigate the most important explanatory factors influencing avian species richness and their distribution using Redundancy analysis (RDA). 3. 85 bird species from 54 genera, 25 families and 15 bird orders were recorded, with mean species richness 14.236.72 (mean  standard deviation) per reservoir. Five of these species are near threatened (NT) while other two species fall under critically endangered (CR) and vulnerable (VU) conservation status designations, respectively. Bird species richness was positively correlated with surface area of reservoirs. The RDA analysis identified two significant RDA axis and 34.4% of the variation in species richness is explained by environmental variation (R2adj = 0.34375; P < 0.001). Generally, water chemistry appears to play only a minor part in affecting bird species richness in reservoir in Tigray, Northern Ethiopia. However, chemical variables may be helpful to distinguish between used and unused sites for some species. 4. The result provides an important insight on the ecological relationship between waterbirds species richness and limnological characteristics of reservoirs. And plays a role towards strengthening our knowledge on aquatic bird ecology and natural history of African Eurasian Migratory waterbirds.