On the relationships of birds and their habitat requirements Insights from a tropical rain forest in Silent Valley National Park, Western Ghats, India

Abstract

At Silent Valley National Park, (SVNP) the habitat associations for birds and the effects ofenvironmental variables, seasonality at various altitudes have been studied. We used bird count datacollected from 60 plots during 2002-2005 at 30-m fixed radius point count stations. A total of 5,253individuals belonging to 108 species were recorded which includes 14 species endemic to WesternGhats. Breeding of32 species were recorded with 517 nests. Highest species richness was found inthe wet evergreen forest sites. Species richness was significantly lower in broad-leaved hill forestfollowed by montane wet temperate forest compared to the other habitat types. Both total birdabundance and species richness were highest within the evergreen habitat of SVNP, which offereddistinctive vegetation. Bird diversity followed the same pattern, evergreen followed by grasslands andmontane wet temperate forest and then by broad-leaved hill forest. Our analysis showed that altitudeappears to be the primary environmental variable responsible for the distribution of species. Weexamined nest-site characteristics and degree of partitioning among 12 major co-existing bird speciesbreeding in SVNP. Habitat characteristics of nest sites differed significantly among species, indicatingstrong nest-site partition ing. The 12 variables for all 442 nest sites were collectively subjected to PCAto determine the relationships of the 12 species in the "habitat space" of SVNP. To summarize thedifferences in the nest site "gestalts" of the species, and to identify the best contributors of theirstatistical separation, Stepwise Discriminant Function Analysis was performed on the entire set of 12variables.