Effect of Human Disturbance on Feeding Behavior and Activity Time Budget of Lesser Adjutant Stork Leptoptilos javanicus (Horsfield, 1821) in Nepal

Abstract

Understanding how animals allocate their time among essential behaviors such as foraging, self-maintenance, and reproduction is critical for effective conservation, especially in human-modified landscapes. The study investigated how Lesser Adjutant Storks (Leptoptilos javanicus) adjust their behavior in response to human disturbance in the Janakinagar-Murtiya Important Bird and Biodiversity Area of Nepal. Using the Focal Animal Sampling method, we captured 600 min of video footage along road transects during the summer of 2023 and winter of 2024. The analysis revealed significant seasonal shifts. During the summer, vigilance dominated the activity budget (47.18%), while feeding was comparatively low (15.06%). In contrast, during winter, storks prioritized feeding (30.33%) over vigilance (23.32%). Kruskal–Wallis and Dunn's post hoc tests confirmed that both feeding and vigilance varied significantly across seasons (p < 0.05), suggesting that species adjust their time budgets based on resource availability and predation risk. Moreover, multinomial regression analysis indicated that human disturbance significantly influenced vigilance, with storks in high disturbance areas displaying greater vigilance than those in low disturbance areas (p < 0.05). These findings were further supported by a Likelihood Ratio Test (LRT = 263.82, df = 6, p < 0.05), confirming that disturbance level had a significant effect on behavioral variation. Collectively, the study suggests that vigilance behavior increases in both frequency and intensity under higher disturbance, potentially at the cost of feeding time and energy intake. This underscores the importance of minimizing human disturbance and conserving critical foraging habitats to support the long-term survival of the Lesser Adjutant Stork population in increasingly human-dominated landscapes.