Bird communities of two forest types in Chitwan Valley, Nepal

Maintaining biological diversity is an important objective at Chitwan National Park (CNP), the most visited national park in Nepal. Given human uses and manipulations of forests both in and around CNP, developing forest management guidelines that can both support human use of trees and sustain the biological diversity of the forests is a high priority. In Febniary 2009 we measured bird communities with point counts, woodpecker abundance with playback, and collected vegetation data in Sal Shorea robusta and riverine forests in CHP and a nearby community forest to provide basic data on bird-habitat associations with an emphasis on woodpeckers. Riverine forest had over twice the density of trees per ha (many small trees), higher tree species richness, and greater basal area than Sal forest. Sal forest had more large trees than riverine forest. We detected 71 bird species during the point counts in the study forests, 18 more during playback sessions, and an additional 12 species that were more associated with adjacent habitats (e.g., wetlands or flying overhead) for a total of 101 species. Among resident species, 31% were primary or secondary tree-cavity nesters. On average for point counts, we detected 29.5 bird species (2.2 woodpeckers) on transects located in riverine forest and 23.3 bird species (1.8 woodpeckers) in Sal forests, but the difference was not statistically significant. While riverine forest had several commonly occurring species not detected in Sal forest, the opposite was not the case. The regression of woodpecker species richness against large tree density in both Sal and riverine forests was positive, but not statistically significant. As a method of sampling woodpeckers, playback resulted in approximately twice the number of individuals and species compared to detection from point counts.