Roosting Patterns and Site Selection among Sympatric Egret Species in a Tropical Wetland Ecosystem in India

Communal roosting, where individuals of the same or different species gather at a shared location to rest, is an adaptive behaviour widely observed in birds and other animal taxa. While it provides benefits such as energy conservation, predator avoidance, and social communication, communal roosting also carries risks, including disease transmission. This study addresses a gap in the knowledge of roosting behaviour among waterbirds, particularly four sympatric egret species, by examining their roosting patterns and roost site selection in a tropical wetland in the Gangetic Plains of Uttar Pradesh, India. Observations conducted over three years recorded habitat variables at the roost, roosting behaviours, emergence and settling times, and pre- and post-roosting activities of four egret species: cattle egret (Bubulcus ibis), little egret (Egretta garzetta), median egret (Ardea intermedia), and great egret (Ardea alba). Statistical analyses revealed significant correlations between roosting patterns and daylight cycles, with emergence positively correlated with sunrise (cattle egret r = 0.991, little egret r = 0.766, median egret r = 0.970, great egret r = 0.899; all P < 0.01) and settling with sunset (cattle egret r = 0.980, little egret r = 0.996, median egret r = 0.966, great egret r = 0.899; all P < 0.01). Day length was negatively correlated with total roosting duration (cattle egret r = -0.699, P = 0.05; little egret r = -0.854, median egret r = -0.856, great egret r = -0.866; all P < 0.01). The comparative analysis of median values revealed significant differences in emergence and settling times, total roosting duration, and pre- and post-roosting behaviours across the four egret species. In contrast, no statistically significant differences were observed in medians of roost site habitat characteristics among the sympatric egret species, suggesting an absence of distinct habitat preference within shared roosting sites. This study enhances understanding of communal roosting dynamics in tropical wetlands and provides insights into the roosting ecology of sympatric egrets, contributing to broader avian conservation efforts.