The Relationship Between Bird Communities and Habitat

Abstract

To assess the impact of habitat disturbance on birds in the Yuksom–Dzongri trekking corridor in western Sikkim, India, the relationships between bird community attributes—including migratory groups and feeding guilds—and vegetation variables were examined. Birds were observed in 19 100-m-long transects, 3 times per season per transect, for 2 seasons from 1997 to 1998 and 1998 to 1999, in an area where forests are subject to various degrees of pressure from human disturbances. Closed canopy forests with relatively undisturbed habitat showed significant variation in habitat attributes, suggesting complexity of habitat structure. Bird species richness and diversity were significantly related to moderately disturbed habitats represented by Principal Component Analysis (PCA), where vegetation heterogeneity (vertical stratification and species composition) was greater. Analysis by migratory groups did not show an interpretable relationship with the habitats, except for the seasonal movements of migratory groups when correlated with altitudinal gradient along the corridor. However, feeding guilds showed significant relationships when correlated with different habitat types. Guilds such as insectivores showed a significant positive relationship with relatively undisturbed habitat, whereas nectarivores and granivores were associated with disturbed habitat. Such relationships have the potential to help assess bird communities and their habitat preferences. Long-term monitoring at landscape level is necessary to understand the dynamics of habitat use patterns by bird communities in relation to spatial and temporal changes.