Assessing Aquatic Avian Biodiversity along Hydropower Dam Gradient: Understanding Impacts of Kurichhu Dam-Induced River Fragmentation in Kurrichu River Basin

Humans are the dominant ecological and evolutionary force on the planet today, transforming habitats, polluting environments, and changing climates. Obstruction to the passage of flowing rivers has a significant environmental impact on fish. It causes rippling effects on wildlife, food web, and habitat throughout the river ecosystem. However, little is known about how these fragmented habitats impact aquatic avifaunal diversity and composition along the stretch of the river. The Kurichhu hydropower dam has disconnected the continuity of upper and lower portions of the Kurichhu River for over 14 years. To investigate this, avian community data were collected at 51 point-count stations, with 17 plots each: in R (Reservoir), AR (Above Reservoir), and BD (Below Dam) along the Kurichhu hydropower dam gradient. In total, 587 individual birds of 33 species distributed under 14 families were encountered. Shannon-wiener diversity among these three sites was higher for the R pool ( H′ = 3.04) than AR ( H′ = 2.74), and the lowest was in BD ( H′ = 2.44). Menhinicks richness index was higher for AR ( D = 2.40) than the R pool ( D = 1.95) and lowest found in BD ( D = 1.73). This study recorded two species of birds in vulnerable and another two species of the order charadriformes in the near-threatened category. Our findings found that habitats along Kurichhu, around Gyelposhing area, are an important stopover and staging area for migratory waterbird species. In light of these findings, addressing the ecological ramifications of river fragmentation on avian diversity is crucial. The marked variation in species richness and diversity across the river segments highlights the pressing need for targeted conservation strategies. To mitigate adverse impacts, we recommend implementing ecological flow regimes and creating wildlife corridors to reconnect fragmented habitats, enhancing habitat quality and supporting avian biodiversity.