Habitat and dietary specialized birds are the main seed dispersers in forest understory

Each species in a plant-bird seed dispersal network plays different roles in network structure, the bird species being more topologically important, but not necessarily the most resistant to habitat disturbance. As a result, we aim to identify the extinction proneness traits that most effect the centrality metrics and determine the complementary specialization in the networks. We utilized four plant-bird networks from understory forest fragments in the Brazilian Cerrado, and for each species we applied three metrics: normalized degree, closeness centrality and betweenness centrality. Using a PCA analyses we unified all indices as the first principal component (PC1) and measure the extinction proneness traits (frugivory level, forest dependence and disturbance sensibility) with a GLM to best explain the variance in PC1. We also measure the complementary specialization in seed dispersal services on the four networks. The model containing frugivory level and forest dependence clearly explains the variance in PC1 (AICcw= 0.938). Three networks presented high specialization and low redundancy. In the understory of forest fragments in Cerrado, obligate frugivores and forest dependent species are the main seed dispersers, but ecologically specialized species tend to be more vulnerable to alterations in the environment. The seed dispersal services in these habitats are also very dependent on dispersal agent diversity, presenting a low redundancy, as the seed dispersal is dependent on species with low ecologically equivalent pairs.