Protected Landscape with Natural Habitat inside Urban Area Could Conserve Avifauna Biodiversity: A Long-term Study from an Overpopulated Subtropical Megacity

Abstract Natural habitats were converted to human-modified landscape as a result of urbanizations in metropolitan areas which resulting in alteration of avian species composition. Analyzing bird habitat preferences and seasonal dynamics can help us better understand how they adapt to changing environments. We used the point count approach at Bangladesh's National Botanical Garden to gain a thorough picture of how a protected landscape playing role in avian biodiversity conservation in a mega-populated, highly polluted city with experienced with extremely modified natural habitat. Along with impacts of habitat heterogeneity and temporal changes on avian community composition was also detected for this three years long survey. Observations based on habitat and seasonal trends revealed a diverse avifauna with 133 bird species (about 20 percent of the country's avifauna) and 5931 individuals belonging to 16 orders and 46 families. Richness and abundance of birds varied significantly among the habitats and season types. The highest richness, abundance and diversity indices was calculated for tree (H = 3.645, D = 0.966) and the pair-wise ANOVA test for habitats was significant only for tree. Red-vented Bulbul Pycnonotus cafer ranked as the most abundant species and we found seven generalist species based on their habitat preferences. Bird assemblages were richer in winter showed significant variation in pair-wise ANOVA test. Although bird diversity was found maximum in winter (H = 3.935, D = 0.976), evenness was calculated the highest for rainy season (E = 0.711). The findings of this study demonstrated that bird variety is strongly linked to their various habitats and seasons. Avifaunal persistence was aided by habitat heterogeneity, which provided optimal foraging, roosting, and breeding options for birds. Diverse type of native plantations habitat and wetlands with natural habitat could aid in conservation of avian communities in urban area. The diversity of bird species revealed the ecosystems' intactness and ecological soundness. This finding provides the foundation for a long-term study of the bird-habitat connection and seasonal fluctuations.