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
14.236.72 (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.