Effects of Habitat Structure and Invasive Alien Plant Species on Bird Assemblages in Jalthal Forest, Eastern Nepal

Abstract

Invasive alien plant species (IAPS) are recognized to have an impact on faunal diversity and the global environment by changing the sort of native habitat in which they thrive. The Jalthal forest is one of the most invaded forests in eastern Tarai. Hence, this study aimed to find out the effects of IAPS cover on the occurrence of birds. By dividing the IAPS cover into three classes (Low, Medium, and High) outer one km strip of the forest was sampled. A total of 89 point count stations were deployed for the point count survey of birds. Generalized linear model (GLM) was done to understand the relation of the diversity and abundance of birds with environmental variables. Spearman's rank correlation was calculated to understand the relation of abundance and richness of different feeding guilds with the cover of IAPS. Canonical Correspondence Analysis (CCA) was done to understand the association of different feeding guilds with disturbance variables and habitat types. A total of 86 species of birds belonging to 13 orders and 41 families were recorded. The insectivorous birds had the highest species richness. Wooded grassland had the highest diversity of birds. Bird species richness and abundance decreased significantly when the distance to the nearest water source, IAPS cover, and shrub cover increased. The Sal (Shorea robusta) forest was found to be the most preferred habitat type, however, the preference of habitats by feeding guilds was conditional. Jalthal forest is Nepal's only forest of its kind, and it is heavily infested by IAPS, more research into biodiversity and the effects of IAPS on biodiversity is in this forest required.