Effects of connectivity on the forest bird communities of adjacent fragmented landscapes

Abstract

Summary. We assessed bird sensitivity to forest fragmentation in two adjacent landscapes in the Atlantic Forest of southern Brazil. One landscape is naturally fragmented and has high connectivity, whereas the other is human-fragmented and has low connectivity. We tested whether the sensitivity of bird species to fragmentation depends more on the intrinsic characteristics of the birds than on landscape connectivity. Point counts were used to sample small and large forest remnants in each landscape. The abundance of each species in these remnants was used as a proxy for sensitivity. To test whether the two landscapes differ in connectivity, we compared the following landscape metrics: landscape shape index (LSI), proximity index (PROX) and connectance index (CONNECT). We analysed the sensitivity of 85 species, 51 of which occurred exclusively in one of the two landscapes. In the landscape with low connectivity we recorded a large number of sensitive species. Among the 34 species that occurred in both landscapes, 24 species (18 non-sensitive and six sensitive) had the same sensitivity. Landscape connectivity seems to be more significant when we focus on the bird communities as a whole. However, when we focus on the same bird species in different landscapes, intrinsic characteristics of species seem to affect their sensitivity to fragmentation more than does landscape connectivity, especially for bird species with lower sensitivity. Therefore, our results show that increasing landscape connectivity may not be the best tool for bird conservation in naturally fragmented landscapes. Nevertheless, it will be important to test further whether forest bird species are more sensitive to environmental degradation in naturally fragmented landscapes than in human-fragmented landscapes.