Spatial distribution of aquatic birds in Anavilundawa Ramsar wetland sanctuary in Sri Lanka
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Biotic and abiotic factors that influence the avian distribution in a dry zone wetland was investigated by studying the distribution of Asian Openbill (Anastomus oscitans), Cotton Pygmy-goose (Nettapus coromandelianus) and Pheasant-tailed Jacana (Hydrophasianus chirurgus) in Anavilundawa Ramsar sanctuary in Sri Lanka in 2006. Their distribution was recorded in Anavilundawa, Suruwila and Maiyawa reservoirs, their catchments and respective paddy fields, through line transects. The floral cover of surface water was recorded by floating quadrates. Water lily (Nymphea spp.) was the dominant flora in Anavilundawa reservoir, invasive water hyacinth (Eichhornia crassipes) in Suruwila reservoir and a native lotus (Nelumbo nucifera) in Maiyawa reservoir, respectively. Anavilundawa area had a higher distribution of birds than in the other two areas. Among the three species observed, Asian Openbill distribution was mainly restricted to Anavilundawa whereas Pheasant-tailed Jacana was present in all three areas. Nesting of Asian Openbill occurred only in Anavilundawa while nesting of Pheasant-tailed Jacana was only observed in Maiyawa. Among the three species recorded, Cotton Pygmy-goose numbers were the least. Asian Openbill preferred dead trees and trees with no leaves for nesting and perching over live trees. It is concluded that the spread of invasives such as Water hyacinth and Salvinia (Salvinia molesta) forming mats over surface water have reduced the abundance of habitat specialists like Cotton Pygmy-goose.
KeywordsInvasive flora Eichhornia crassipes Salvinia molesta Asian Openbill Cotton Pygmy-goose Pheasant-tailed Jacana Avian distribution Native invasives
The authors thank Department of Wildlife Conservation, Sri Lanka for their permission to conduct field work at Anavilundawa Ramsar sanctuary. M. D. S. T de Croos, K. Wijenayake, G. Thilakeratne and C. Pathirage are acknowledged for assistance in the field. We appreciate the help of Anavilundawa temple and villagers. Wayamba University of Sri Lanka funded the study.
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