Sunny, Nama2026-07-292026https://digitalrepository.wii.gov.in/handle/123456789/1457Riverine alluvial grasslands of the Brahmaputra floodplains are among the most dynamic and threatened ecosystems in India. These floodplain grasslands, maintained by annual flooding and sediment deposition, host a unique assemblage of obligate grassland birds dependent on early and mid-successional habitats. However, quantitative information on the population status and habitat requirements of these species is limited especially in the riverine grasslands of D'Ering Memorial Wildlife Sanctuary, Arunachal Pradesh. In this context, the present study was designed to estimate the population density of obligate grassland birds and to explore the influence of habitat characteristics on their distribution in this dynamic floodplain ecosystem. The study was conducted across the three management ranges of D’Ering Memorial Wildlife Sanctuary using 252 systematically distributed point count stations. Bird surveys were conducted using passive point counts and call-playback surveys while acoustic triangulation was used to estimate the position of vocalising birds for distance sampling analyses. Habitat selection was assessed using micro-habitat variables, grass species composition, vegetation structure and landscape attributes such as island age and island size. Generalized Linear Models (GLMs) were used to identify habitat variables associated with species occurrence while community level responses were assessed using Non-metric Multidimensional Scaling (NMDS). When comparing survey methods, call playback greatly enhanced detectability of all four focal species by eliciting vocal responses from individuals hidden in dense grasslands. However, passive aural point counts produced more precise density estimates with consistently lower coefficients of variation, indicating that observations made under natural behavioural conditions better satisfied the assumptions of distance sampling. The successful application of acoustic triangulation further demonstrated its usefulness for estimating detection distances of vocally active grassland birds in dense alluvial grasslands where direct visual observations were often not possible. Habitat‐selection analyses indicated that obligate grassland birds were influenced primarily by vegetation structure, grass composition and floodplain succession rather than simply habitat area. The Saccharum spontaneum–Typha latifolia grass assemblage was the most important predictor of species occurrences for all four focal species, and taller grasslands were consistently favoured over shorter vegetation. Three of the four focal species had higher probabilities of occurrence on younger alluvial islands, indicating a strong association with early-successional floodplain habitats maintained by natural flooding. Community-level analyses further demonstrated a clear ecological separation between obligate grassland birds and habitat generalists along vegetation and successional gradients. Obligate species were associated with younger islands dominated by tall-grass communities, whereas habitat generalists occurred more frequently on older islands characterised by increasing woody vegetation. These results emphasize the importance of flood-driven succession in structuring both species-specific habitat selection and overall composition of the grassland bird community .the results demonstrate that conservation of obligate grassland birds requires the maintenance of the ecological processes that sustain floodplain grasslands rather than simply protecting static habitat patches. Passive aural point counts combined with acoustic triangulation provide a robust structure for long-term monitoring of cryptic grassland birds, while maintaining natural flood regimes and a heterogeneous mosaic of grasslands across different successional stages is likely to be fundamental for sustaining the tall-grass bird guild of D'Ering Memorial Wildlife Sanctuary. The study provides the first quantitative baseline on population density and habitat selection of obligate grassland birds from this protected area and offers a foundation for future ecological research and long-term monitoring of riverine grassland ecosystems.enRiverine alluvialGrasslandPopulation statusHabitat selectionPopulation densityGrassland birdsThesis