Roosting Behavior of Waterbirds at Ruhuna University Premises in Sri Lanka

Communal roosting is a habit of many waterbirds. Although it is a common behavioural pattern, only a few documentary records are available in Sri Lanka. Therefore, the present study aimed to investigate the roosting behaviour of waterbirds at Ruhuna University Premises, Sri Lanka. The study was conducted from November 2020 to February 2021 covering 20 field visits. During field visits, the abundance of waterbirds, their arrival time, intra-species, and inter-species interactions were observed. The responses of roosting waterbirds to human disturbances and occasional visitors to roosting sites were also recorded. The waterbirds roosted on a single Sonneratia caseolaris tree, located at the waterbody closer to the bank. Eleven species of waterbirds were identified, and the Cattle Egrets (Bubulcus ibis) were prominent (93%). The diversity and species abundance gradually increased during the study period. The highest species richness (11) and diversity (H- 0.8832) were recorded in February. The roosting behavior of birds has been altered by human disturbances. The waterbirds co-existed on the roosting site with inter- and intra-species associations while maintaining hierarchical levels (different height levels of the tree). Sixteen species of occasional visitors were recorded, and they left the site with the arrival of regular waterbirds.