Predation pressure by birds and arthropods on herbivorous insects affected by tropical forest restoration strategy

Recovery of animal-dependent ecosystem functions is a key component of ecological restoration on degraded tropical forest lands. One of these functions, regulation of herbivorous insects by predators, shapes tropical communities through cascading trophic effects. An improved understanding of how predation pressure on herbivorous insects varies with reforestation strategy, management decisions, and landscape context would guide restoration practice. We measured predation pressure by birds and arthropods on dummy caterpillars in five forest types in Panama. These land covers represent natural and managed forest conditions: non-native monoculture plantation, native multispecies plantation, young natural forest succession, secondary gallery forest, and old-growth forest. We also placed dummy caterpillars in residential countryside, a heavily disturbed nonforest land cover. In three land covers, we surveyed bird communities to examine the relationship between predator abundance and predation pressure. Predation pressure from birds was lowest in the intensively managed plantations and highest in land covers with structurally complex vegetation: successional forest, gallery forest, and residential countryside. In the non-native plantation, bird predation increased with proximity to gallery forest. We found strong correspondence between bird abundance and bird attacks on dummy caterpillars. Arthropod predation pressure was highest in the native plantation but, unlike bird predation pressure, did not vary strongly by land cover. Our results suggest that ecosystem functions by insectivorous birds can be enhanced on reforestation lands by incorporating unmanaged areas and tolerating nonplanted understory vegetation. We recommend that, regardless of management objectives, forest managers adopt a holistic approach to reforestation to facilitate recovery of animal-dependent ecosystem functions.