Northwestern transboundary area of Bangladesh: a key to sustaining a quarter of the country's avian species

In the face of global forest ecosystem decline, non-protected transboundary areas like agroforestry can play a crucial role for conserving avian species. A comprehensive study on agroforestry birds in Tetulia, the northernmost area of Bangladesh, was conducted across four sites from November 2021 to October 2022. A total of 174 species (5479 contacts) of avifauna were recorded. The order Passeriformes had the highest avian diversity (70 species, 40.22%), followed by Charadriiformes (20 species, 11.50%), Accipitriformes (17 species, 9.77%), and Pelecaniformes (13 species,7.47%). The species list showed that resident birds were higher (122 species, 70.11%) than migratory birds (52 species, 29.89%). The highest richness (144 species), abundance (N = 1581), and diversity (H = 4.522, Ds = 0.984) were observed in site A1. The heterogenous nature of site A1 contributed to this result although spatial bird diversity was non-significant. The highest species richness, abundance, and diversity indices of birds showed in the winter season because of the presence of migratory species. The frequent bird activity, less anthropogenic pressure, and high detection probability during winter can influence the seasonal bird diversity result. The homestead habitats displayed the highest diversity indices (H = 4.051, Ds = 0.977) and evenness (E = 0.736) due to the diversity of plants. Birds in tea garden and agricultural land shared similar species, while water bodies associated with tea garden had more distinct species with a negative correlation value. The low-contrast edge between tea garden and agricultural land made a positive relation in bird composition. The top ten abundant species contributed 28.71% of total and jungle babbler (Turdoides striata) had the highest relative abundance. The baseline data we have collected holds significant potential for informing future research endeavors. Policymakers can leverage this foundational information to initiate conservation measures aimed at protecting the avifauna within the study site.