Effects of forest fragmentation on nocturnal Asian birds:A case study from Xishuangbanna,China

Owls have the potential to be keystone species for conservation in fragmented landscapes, as the absence of these predators could profoundly change community structure. Yet few studies have examined how whole communities of owls respond to fragmentation, especially in the tropics. When evaluating the effect of factors related to fragmentation, such as fragment area and distance to the edge, on these birds, it is also important in heterogeneous landscapes to ask how ＇location factors＇ such as the topography, vegetation and soil of the fragment predict their persistence. In Xishuangbanna, southwest China, we established 43 transects （200 mx60 m） within 20 forest fragments to sample nocturnal birds, both visually and aurally. We used a multimodel inference approach to identify the factors that influence owl species richness, and generalized linear mixed models to predict the occurrence probabilities of each species. We found that fragmentation factors dominated location factors, with larger fragments having more species, and four of eight species were significantly more likely to occur in large fragments. Given the potential importance of these birds on regulating small mammal and other animal populations, and thus indirectly affecting seed dispersal, we suggest further protection of large f ragments and programs to increase their connectivity to the remaining smaller fragments.

Effects of ice storm on species richness and abundance of resident birds in subtropical forest in southern China

Between January and February 2008,a severe ice storm occurred in southern China.The storm damaged nearly 21 million hectares of forest lands with broken branch,trunk breakage,and stem bending of many trees.This natural disturbance provides a unique opportunity to study impacts of extreme climatic event on forest birds.Using hierarchical multi-species occupancy model(species richness;27 species)and N-mixture model(abundance;3 species),we investigated how the storm affected resident bird species in subtropical forest in southern China.We sampled birds at Chebaling National Nature Reserve in Guangdong Province,monthly for 1 year each before and after the storm by mist nets.To take into account variations in temperature between years and between months,we incorporated monthly mean temperature into the models as an additional covariate.Observed species richness was greater before the storm.Estimated species richness(from the hierarchical model)also tended to be greater before than after the storm although 95%Bayesian credible intervals of these estimates were overlapped.Temperature showed a negative effect on estimated species richness,indicating greater species richness during winter.Among three species captured the most,abundance of Chestnut Bulbul(Hemixos castanonotus)significantly decreased after the storm.Other two species,Grey Treepie(Dendrocitta formosae)and Huet’s Fulvetta(Alcippe hueti)showed insignificant responses to the storm.Our study indicates that the 2008 ice storm may not have a significant impact on species richness of resident birds in subtropical forest;however,the effect can be species-specific and negative to some species’population.