Habitat–occupancy associations and tree-species use patterns by breeding birds in Tibetan sacred forests

Abstract

Himalayan forests are undergoing rapid changes due to population growth and economic development and their associated bird communities are among the most threatened and least-studied on earth. In the Chinese Himalaya, traditionally managed Tibetan sacred forests are keystone structures for forest bird conservation. Yet, it remains unclear which fine-scale habitat characteristics of the sacred forests are best associated with Himalayan forest bird species. Our goal here was to quantify the relationship between forest habitat characteristics and bird communities in Tibetan sacred forests to understand habitat associations of common forest birds in the Chinese Himalaya. In 2010 and 2011, we conducted bird point counts and habitat surveys at 62, 50-m radius, sample points distributed within and adjacent to six Tibetan sacred forests in northwest Yunnan, China. From this data, we constructed habitat–occupancy relationship models for 35 bird species and documented tree-use patterns of 14 common arboreal foraging bird species. Our modeling results revealed that large diameter trees and heterogeneity in vertical vegetation structure were the most important habitat characteristics, and were positively associated with occupancy of 63 % of the study bird species. Furthermore, we found that occupancy of eight bird species of conservation concern was related to specific thresholds of forest integrity characteristics. For example, predicted occupancy of three of eight species was high in forested habitats with >15 % bamboo cover and was greatly reduced when bare ground cover exceeded 5 %. We found that bird species foraged on pine (Pinus densata, 58 % more than it was available) and poplar (Populus davidiana, 41 %) in higher proportion to their availability, but that foraging success was highest on fir (Abies spp.), oak (Quercus spp.), willow (Salix spp.) and Chinese Larch (Larix potaninii). Our findings suggest that, although conservation is not a primary management goal of Tibetan sacred forests, these lands harbor critical habitat features for forest breeding birds of the Chinese Himalaya.