Efeito da estrutura do habitat na distribuição espacial de duas espécies de tinamídeos (Aves: Tinamidae) na floresta de terra-firme na Amazônia Central

Abstract

The influence of environmental heterogeneity on the distribution of arboreal birds has been studied intensively, but such effects are little studied in terrestrial birds in tropical forests. Here we investigate how the spatial distribution of two terrestrial bird species from the family Tinamidae is modulated by the variation in the natural structure of central Amazonian terra-firme forest. We test five descriptors of forest structure (dead fallen trunks, canopy openness, tree abundance, leaf-litter depth and distance to water bodies) as explanations for the variation in the spatial distribution of Great (Tinamus major) and Variegated (Crypturellus variegatus) Tinamou. Between October 2012 and April 2013, we used 30 listening points to estimate the frequency of occurrence of these species within a 25 km² area. Studies were conducted between 05:30 and 10:00 h using passive listening and playback. In the same area we used 250 x 40 m plots to measure the forest structure components. Multiple linear models indicated that the frequency of occurrence of Tinamus major was not explained by any tested component of the forest structure. However, the number of Crypturellus variegatus encounters increased significantly in areas beneath more open canopy and where there were more fallen dead trunks. It diminished in areas where leaf litter was deeper. The results provide additional evidence that forest heterogeneity can be an important factor influencing the spatial distribution of terrestrial birds. In addition, this study contributes to the knowledge of how terrestrial birds respond in different ways to the spatial variation in the same components of structure of Amazonian terra-firme forest.