A test of the utility of exotic tree plantations for understory birds and food resources in the Colombian Andes

The spatial distribution and abundance of animals are in part determined by the distribution and abundance of their resource base. In the Central Andes of Colombia, monospecific tree plantations have been used to recover vegetative cover in watershed protection programs, but these plantations differ from natural forests in structure, composition, and resources available to wildlife. To evaluate these plantations as habitat for wildlife, we compared the diversity and abundance of understory birds, flowers, and fruits between juxtaposed 40-yr-old patches of exotic Chinese ash (Fraxinus chinensis) plantations and naturally regenerated forest of the same age. We observed more fruiting species in the regenerated forest, but there were no differences in total flower and fruit availability between habitat types. We also observed differences between habitats in the size of some understory shrubs, but these differences did not lead to differences between habitats in the diversity and abundance of birds. Capture rates of nectarivores correlated with resource abundance at sampling plot scale, but no such correlation was found for frugivores. Understory frugivorous birds are apparently functioning at a larger spatial scale than the patchiness created by the two habitats. Nectarivorous birds are responding to small-scale patchiness in resource availability, but not to the different habitats. These results indicate that at small scales, the ash plantation understory provides adequate habitat for birds.