The Cost of Urban Expansion: Habitat Loss and Shifting Distribution of Long-Legged Wading Birds in a Peri-Urban landscape gradient

Urbanisation, a key indicator of socioeconomic development, often comes at the cost of natural habitats, particularly in peri-urban wetlands. Human-influenced wetlands may refuge diverse avian species, but the extent of their effectiveness remains uncertain. Ardeidae species are often considered effective bioindicators of wetland health, due to their high mobility and dependence on wetlands for foraging. This study assessed the influence of land use patterns on the Ardeidae community structure across four peri-urban regions of Kolkata, India. A total of 20,537 individuals belonging to six commonly found Ardeidae species were recorded. The aquaculture farms had the highest abundance (75.18% of observations) of Ardeidae species, indicating their importance as foraging habitats. Land Use and Land Cover changes over two decades from Kolkata and its surrounding landscapes revealed rapid urban expansion, increased waterbodies (primarily aquaculture farms), and substantial loss of tree cover. The generalist species comprised 65.26% of overall observations, suggesting higher resilience to urbanised habitats. Whereas marshland specialists showed vulnerability to urban-driven habitat changes. Conversely, open-water foragers were scarce in urban-fringed areas, but abundant in fish farming, which further heightens the conflict between aquaculture farms and the species. The Generalised Linear Mixed Models highlight the importance of habitat heterogeneity to support a wide range of species assemblages. This study emphasised that urban sprawl has negative impacts on Ardeidae community structure. Effective conservation in urbanising areas requires the protection of multifunctional wetlands, establishment of buffer zones, promotion of sustainable aquaculture, and involvement of local communities in conflict mitigation.