Investigation on the foraging ecology of black crowned cranes at Lake Tana, Ethiopia, in the context of climate change impacts

Abstract

There are significant gaps in understanding the food resources of the black crowned crane in the Lake Tana wetlands. This study examined macroinvertebrates in crane habitats, investigated the impact of rainfall on macroinvertebrates in relation to pollution tolerance, and identified macrophytes and crop seeds as food sources for cranes. Thirty- one macroinvertebrate taxa were identified across the two selected study sites, Chimba and Yiganda wetlands. The Chimba site was more affected by rainfall variability, showing a dominance of tolerant taxa in 2014, indicative of high organic pollution from runoff. In contrast, Yiganda exhibited greater resilience. Although macroinvertebrate biomass remained stable across years, significant spatial variation was noted between sites. Diversity indices revealed moderate community richness, and rarefaction analysis indicated an increase in diversity over time. Four key macrophytes – Cyperus rotundus, Sacclolepis africana, Leersia hexandra, and Oryza longistaminata – dominated crane habitats, with L. hexandra and O. longistaminata being preferred. Grass seed biomass peaked after the rainy season with no significant spatial variation. Crop analysis showed cranes notable preference for teff. The study findings quantitatively highlight the significance of macroinvertebrates, native grasses, and agricultural crops in the crane diet, providing essential baseline data for developing wetland management strategies that balance crane conservation with agricultural productivity in this ecologically important region.