Relationship between Occurrence of Birds and Vegetation Structure of Riparian Habitats

Abstract

Riparian lands and their vegetation provide important habitat for terrestrial animals includingbirds. Even though riparian lands may occupy only a small percentage of the catchmentlandscape they provide nesting and feeding habitats for a large number of bird species. Butdue to construction of dams, human uses of riparian vegetation, logging, road construction,livestock grazing and sand mining riparian habitats are depleting in Sri Lanka. The presentstudy was aimed to compare habitat use by birds with available riparian vegetation, and tocompare bird population characteristics among riparian habitats with different vegetationstructure. In order to achieve the objectives, occurrence of birds was studied in two differentriparian systems; ‘Loggal oya’ and ‘Minipe’ area of Mahaweli River which are having twodifferent vegetation structures. There are significant differences in the abundance of canopyvegetation and understory vegetation and no such difference in abundance of groundvegetation between two sites. 500 m line transects with a width of 40 m were placed parallelto the stream flow and birds were recorded. Birds were recorded for 10 minutes at each of 10equally spaced stations along the transect and while moving between stations. Species andnumber of birds were recorded. Seventy four bird species were observed with a highestdiversity in the Loggal oya (H’=2.58 with respect to H’=2.42 in Minipe). Bird density wasalso higher in the Loggal oya with a significant difference. Canonical correspondanceanalysis showed that Canopy cover is the highest contributing factor for the distribution ofbirds. A positive correaltion was observed between the vegetation structure and theabundance of birds thus, concluding that riparian habitats are imporatant areas for birds for itssurvival. By understanding the associations between birds and habitat, management activitiescan be implemented to provide appro-priate habitat for desired species.