Abstract:Oil palm plantations are rapidly expanding in tropical areas, although the nature of the impacts on the functional roles of the different species in the ecosystem is poorly understood. The present study is the first assessment of how oil palm affects the functional diversity of birds in the Brazilian Amazon and tests the hypothesis that converting forest to oil palm decreases functional diversity of bird communities, selecting species more tolerant to environmental disturbances. We conducted point counts to survey bird communities in 16 plots in the eastern Amazon. We sampled 32 points in riparian forest, 128 in oil palm and 160 in forested habitats. To test whether the conversion of forest into oil palm plantations affects functional diversity of birds we calculated the FD (Functional Diversity) and FRic (Functional Richness) indices. To examine whether oil palm plantations select species functionally more similar than expected by chance we used a null model (SES.FD). FD was significantly higher in the forest plots in comparison with riparian forests and oil palm, and lower in oil palm when compared with riparian forests. FRic, in turn, was greater in forest plots than in oil palm and in riparian forest. These results show that the conversion of forested areas to oil palm represents a great loss of functional strategies. The SES values indicate that in forested habitats bird communities tend to be functionally clustered while in the oil palm they are functionally overdispersed. The functional traits most affected by oil palm were those associated with diet and foraging stratum. In short, oil palm plantations reduced functional diversity of birds, although the presence of riparian forests within the plantations and the fragments of forest adjacent are extremely important for the maintenance of ecosystem services.

Oil palm (Elaeis guineensis) is a rapidly expanding crop in the Amazonian region of Brazil. Brazilian law requires all landowners, including oil palm plantations, to maintain forest reserves and forested riparian corridors as a way to limit biodiversity losses. Because of these laws and the forest-like structure of oil palm, these plantations may function as habitat for some native species in the region. We tested this assumption by experimentally translocating Cinereous Antshrikes (Thamnomanes caesius), a forest understory insectivorous bird and nuclear member of mixed-species flocks, from forest reserves to riparian corridors within a large oil palm plantation landscape and tracked their movements back to their home ranges. In total, we recorded the movements of 18 individuals, 8 of which were translocated. The other 10 individuals were tracked within their home ranges in the forest reserves. Six of the eight translocated birds successfully returned to their forest home range, but only one bird flew through the more direct route back through the oil palm matrix while the rest took longer routes through adjoining riparian corridors. Homing time for translocated birds averaged 9.57 (AE2.23 SE) days. The home range of birds within the forest reserves averaged 2.39 (AE0.69 SE) ha, and, with the exception of the single returning bird, Cinereous Antshrikes were never detected in oil palm. Our results suggest that oil palm plantations are a barrier to movements of our study species, and that riparian corridors connecting forest fragments may be effective routes for dispersal.

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