Diurnal raptors of Eastern Himalayan foothills: Taxonomic and functional diversity attributes

Abstract Raptors are crucial indicators of ecosystem health, and thus, requires research attention. Despite an upsurge in Indian ornithology, raptors remain poorly studied, particularly in Northeast India. Here, we measured the taxonomic and functional diversity of raptors in Manas National Park, Assam. The study was conducted between 2018–2022. We surveyed 39 standard transects and recorded 776 individuals of raptors belonging to 30 species in different habitats: forest, open and mosaic. The taxonomic alpha diversity was highest in mosaic habitat and lowest in the forest habitat. Crested Serpent Eagle (Spilornis cheela) was the most abundant raptor in open and forest habitats, while Collared Falconet (Microhierax caerulescens) was dominating in mosaic habitats. Of the recorded raptor species, 66.67% were classified as residents, and 33.37% were winter migrants. We also measured the functional alpha diversity of raptors using the data collected from AVONET database. We used ten functional traits and evaluated the functional alpha diversity indices. The functional richness was the highest in open habitats and functional divergence was the highest in mosaic habitats, also functional evenness was the highest in open habitats and lowest in mosaic habitats. We suggest intensified research on raptors in the region, to identify and address critical research question which facilitates the conservation of these apex predators.