Combined effects of habitat and interspec ificinteraction define co-occurrence patterns of sympatric Galliformes

Background:Disentangling the relative importance of environmental variables and interspecific interaction in modulating co-occurrence patterns of sympatric species is essential for understanding the mechanisms of community assembly and biodiversity. For the two sympatric Galliformes, Silver Pheasants (Lophura nycthemera) and Whitenecklaced Partridges (Arborophila gingica), we know little about the role of habitat use and interspecific interactions in modulating their coexistence. Methods:We adopted a probabilistic approach incorporating habitat preference and interspecific interaction using occupancy model to account for imperfect detection,and used daily activity pattern analysis to investigate the cooccurrence pattern of these two sympatric Galliformes in wet and dry seasons. Results: We found that the detection probability of Silver Pheasant and White-necklaced Partridge were related to habitat variables and interspecific interaction. The presence of Silver Pheasant increases the detection probability of White-necklaced Partridge in both the wet and dry season. However, the presence of White-necklaced Partridges increases the detection probability of Silver Pheasants in the wet season, but decreases the probability in the dry season. Further, Silver Pheasants were detected frequently in the sites of high values of enhanced vegetable index (EVI) in both the wet and dry season, and in sites away from human residential settlement in the wet season. Whitenecklaced partridges were mainly detected in low EVI sites. The site use probabilities of two Galliformes were best explained by habitat variables, Silver Pheasants and White-necklaced Partridges preferred steeper areas during the wet and dry season. Both species mainly occurred in low EVI areas during the wet season and occupied sites away from the resident settlement during the dry season. Moreover, the site use probabilities of two species had opposite relationships with forest canopy coverage. Silver Pheasants preferred areas with high forest canopy coverage whereas White-necklaced Partridges preferred low forest canopy coverage in the dry season, and vice versa in the wet season. Species interaction factor (SIF)corroborated weak evidence of the dependence of the site use of one species on that of the other in the either dry or wet season.Temporally, high overlapping of daily activity pattern indicated no significantly temporal niche differentiation between sympatric Galliformes in both wet and dry seasons. Conclusions:Our results demonstrated that the presence of two species influenced the detection probability interactively and there was no temporal partitioning in activity time between Silver Pheasants and White-necklaced Partridges in the wet and dry seasons.The site use probability of two Galliformes was best explained by habitat variables, especially the forest canopy coverage.Therefore, environmental variables and interspecific interaction are the leading drivers regulating the detection and site use probability and promoting co-occurrence of Silver Pheasants and White-necklaced Partridges.

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.