The majority of deforested land in Latin America has been converted to pasture, creating an inhospitable landscape for wildlife that depend on dwindling tropical forests. The systematic incorporation of trees into pastures (i.e., silvopastures) has been shown to ameliorate the negative effects of cattle production on avian biodiversity. However, evidence suggests that despite a substantial improvement over conventional pastures, silvopastures support relatively depauperate avian communities when compared to other agroforestry systems such as shade coffee. Prior silvopastoral studies have quantified avian species richness and abundance to provide a limited measure of avian habitat quality in these systems, but foraging behavior studies can generate a mechanistic understanding of habitat quality and may provide critical information for conservation efforts. We studied the foraging behavior of avian insectivores in forest fragments and silvopastures in the Colombian Andes to determine if silvopastures provide adequate resources for avian insectivores and to identify microhabitats and tree species that could be incorporated into silvopastures to improve habitat quality. We selected five focal avian species to test for differences in foraging efficiency between habitats and included 15 additional species sorted into two groups (sensitive or adaptive) to evaluate microhabitat and tree species preferences.
Results/Conclusions
All focal species attacked prey less frequently in silvopastures than in forest fragments, suggesting that avian insectivores commonly found in silvopastures may fare better in forest fragments. Furthermore, Hylophilus semibrunneus and Hemithraupis guira travelled greater distances per movement while foraging in silvopastures. Conversely, Vireo olivaceus and Polioptila plumbea employed a higher proportion of glean attack maneuvers in silvopastures than forest fragments, possibly related to greater predation of Lepidoptera larvae in silvopastures by these two species. Sensitive species were restricted to forest fragments and preferentially foraged in Cupania americana, Inga spp. and Machaerium spp. Adaptive species preferred Anacardium excelsum, Inga spp., Croton magdalenensis and Machaerium spp. in forest fragments but foraged non-selectively in silvopastures. Overall, while some avian insectivores compensated for lower attack rates in silvopastures by changing foraging behavior, silvopastures appeared to act as energetic sinks, which may reduce reproductive success. Sensitive bird species were largely understory species that are unlikely to utilize silvopastures without substantially greater structural complexity. However, incorporation of preferred tree species could prevent silvopastures from serving as ecological traps for the avian species that are already utilizing them.