Effect of natural and anthropogenic landscape matrices on the abundance of subandean bird species

The nature of the landscape matrix can control the capacity of forest organisms to move among forest patches. Some matrices may constitute foraging or breeding habitat and, as a result, could influence the local abundance of forest organisms and their persistence in fragmented landscapes. This study represents a first approach to examining the effect of natural vs. anthropogenic landscape matrices on the abundance of neotropical birds in forest sites. The influence of three contrasting matrices on the relative abundance of 113 bird species in a subandean region was evaluated. Species were grouped into categories showing the same response to the matrix, and these groups were then examined to determine whether ecological characteristics or taxonomic affinities were associated with responses to surrounding matrices. The abundance of individual species in forest plots within a continuous forest matrix was compared with their abundance in forest fragments embedded in pastures or exotic-tree plantations. The matrix surrounding forest areas was a major factor influencing bird abundance: 65.5% of the species showed significant differences in abundance among sites surrounded by different matrices. The most important explanatory factors in the variation in abundance within fragments were: abundance within continuous forest, presence in the anthropogenic matrices, migratory strategy, and habitat association. Species with small geographic ranges and species of terrestrial insectivores had low tolerance to fragmentation. Responses were highly species specific and largely independent of foraging strata, trophic group, and taxonomic affinities. Several lines of evidence indicate an increased connectivity among forest remnants surrounded by exotic-tree plantations compared to pastures. Landscape supplementation by the exotic-tree plantation matrix was observed for a hummingbird species. These results suggest that structurally complex anthropogenic matrices have potential as management tools for bird conservation by complementing habitat protection and restoration.