Waterfowl Diversity and Feeding Ecology in Panidihing Bird Sanctuary, Sivasagar District, Assam, India

Abstract

Wetlands of the Brahmaputra floodplain support rich waterfowl communities whose foraging ecology reflects the dynamic habitat conditions shaped by seasonal hydrology. This study investigated the dietary composition, foraging behaviour, and niche partitioning of eight duck and goose waterfowl species in Panidihing Bird Sanctuary, Assam, based on three years of field observations (2021-2023) across 13 sites. Direct behavioural sampling, videography, and coexisting habitat measurements were used to document feeding strategies, diet types, and habitat preferences. Waterfowl diversity showed a steady improvement over the study period, with the Shannon-Wiener index rising from H′ = 1.412 (2021) to 1.543 (2022) and 1.745 (2023), indicating an increase in evenness and species balance. Shallow-water zones formed the most important feeding habitat (42% of records), followed by open water (32%) and grasslands (26%). Species exhibited clear trophic and spatial segregation: feeding activity ranged from 16% in Ruddy Shelduck to 37% in Indian Spot-billed Duck, while guild representation showed dominance of dabbling omnivores and aquatic-terrestrial herbivores (25% each). Foraging techniques were led by dabbling (n=8) and diving (n=4), with minor occurrences of surface skimming and kleptoparasitism. Dietary analysis revealed that benthic invertebrates and aquatic plants contributed the highest proportions (22.86% each), followed by fish (20%), while grasses and phytoplankton made up smaller shares (17.14% each). These patterns demonstrate strong niche partitioning determined by morphological traits, water depth preferences, and habitat heterogeneity. The findings highlight the importance of maintaining shallow wetland habitats and natural hydrological regimes to sustain diverse waterfowl assemblages in floodplain ecosystems.