Bird Community Structure in the South Kainakary and Pallithode Agroecosystems of Central Kerala

Abstract

Introduction: Birds are key bio-indicators of environmental quality and ecosystem health due to their sensitivity to habitat alteration and pollution. Agroecosystems, particularly in tropical regions, are increasingly exposed to anthropogenic pressures including chemical inputs, plastic waste accumulation, land-use transformation, and infrastructural expansion. Such stressors can influence avian diversity, abundance, and community structure. Central Kerala hosts diverse wetland-linked agroecosystems that differ in hydrological regimes (freshwater vs. saline), potentially affecting species assemblages and ecological stability. Understanding bird community responses in these landscapes is essential for evaluating ecological risks and informing sustainable management practices.

Objectives: 1. To assess and compare bird species diversity and community structure in freshwater (South Kainakary) and saline (Pallithode) agroecosystems. 2. To evaluate community composition using standard biodiversity indices. 3. To examine potential anthropogenic and environmental risk factors influencing avian distribution.

Methods: The study was conducted from January to December 2023 in two agroecosystems of Central Kerala: South Kainakary (freshwater) and Pallithode (saline). Monthly bird surveys were carried out using standardized line transect and direct observation methods during peak activity hours (morning; 6-10am). Species identification was performed using standard ornithological field guides.Community structure was analyzed using: Margalef Richness Index (DMg), Shannon–Wiener Diversity Index (H'), Simpson’s Diversity Index (D), Berger–Parker Dominance Index (d) and Pielou’s Evenness Index (J'). Comparative analysis was conducted to evaluate ecological variation between sites.

Results: A total of 92 bird species belonging to 15 orders and 38 families were recorded. Passeriformes was the most dominant order (24 species), whereas Columbiformes, Apodiformes, Podicipediformes, and Psittaciformes showed lower representation. Pallithode (saline agroecosystem) exhibited higher species richness and diversity (DMg = 8.75; H' = 2.43; J' = 0.54), indicating a relatively stable and heterogeneous bird community. In contrast, South Kainakary showed higher dominance values (Berger–Parker d = 0.48; Simpson D = 0.27), suggesting concentration of individuals among fewer species. Field observations revealed multiple anthropogenic stressors including land-use changes, plastic accumulation, domestic waste discharge, tourism disturbance, and hazards from electric transmission lines and communication towers, potentially posing chemical and environmental health risks to avifauna.

Conclusions: The saline agroecosystem of Pallithode supports greater avian diversity and evenness compared to the freshwater agroecosystem of South Kainakary, which shows higher species dominance. Anthropogenic pressures, including pollution and infrastructural expansion, may influence community structure and ecological stability. Continuous monitoring and integrated habitat management strategies are essential to mitigate environmental risks and sustain avian biodiversity in agroecosystems of Central Kerala.