Time activity budget and foraging behavior: important determinants of resource sharing and guild structure in wintering waterbirds

The main focus of this work was to study the use of freshwater wetlands by 12 waterbirds (4 resident species and 8 Palearctic migrant species) during the wintering period in West Bengal, India. From morning to evening hours, the time budget of waterbirds changed significantly. The differences in diurnal activities between migrants and residents were statistically significant. Foraging niche overlaps were calculated based on foraging habitats and techniques; five migrant species had exceedingly high niche overlaps (habitats 0.80-0.99; techniques 0.79-0.99). Overlap among resident birds or migrant species was much lower (habitats 0.01-0.56; techniques 0.01-0.66). Niche dimensions like the foraging habitats (1.26-3.47) and foraging techniques (1.13-4.54) and these two dimensions together (1.64-8.63) calculated the niche breadths. A mean Euclidean distance of 5.63 in Cluster analysis constructed on two niche dimensions reliably defined four distinct guilds. The post hoc test highlighted significant differences between the intra-guild niche breadths. Proportional differences in the uses of foraging habitats and techniques and temporal variations in foraging activities accommodated residents and winter migrants in the study sites. Such information would be crucially important for the conservation and effective management strategies of Indian waterbirds and their habitats, situated along the East Asian-Australian and Central Asian Flyways, which are significant tropical wintering grounds for migratory waterbirds.