Birds and bats reduce insect biomass and leaf damage in tropical forest restoration sites

Abstract

Both birds and bats are important insect predators in tropical systems. However, the relative influence of birds and bats on insect populations and their indirect effects on leaf damage have not previously been investigated in tropical forest restoration sites. Leaf damage by herbivorous insects can negatively affect the growth and survival of tropical plants and thus can influence the success of tropical forest restoration efforts. We used an exclosure experiment to examine the top-down effects of birds and bats on insects and leaf damage in a large-scale forest restoration experiment. Given the potential influence of tree planting design on bird and bat abundances, we also investigated planting design effects on bird and bat insectivory and leaf damage. The experiment included two planting treatment plots: islands, where trees were planted in patches, and plantations, where trees were planted in rows to create continuous cover. In both types of plots, insect biomass was highest on tree branches where both birds and bats were excluded from foraging and lowest on branches without exclosures where both birds and bats were present. In the island plots, birds and bats had approximately equal impacts on insect populations, while in plantations bats appeared to have a slightly stronger effect on insects than did birds. In plantations, the levels of leaf damage were higher on branches where birds and bats were excluded than on branches where both had access. In island plots, no significant differences in leaf damage were found between exclosure treatments although potential patterns were in the same direction as in the plantations. Our results suggest that both birds and bats play important roles as top predators in restoration systems by reducing herbivorous insects and their damage to planted trees. Tropical restoration projects should include efforts to attract and provide suitable habitat for birds and bats, given their demonstrated ecological importance.

Neotropical rainforest restoration: comparing passive, plantation and nucleation approaches

“…Most practitioners consider planting high density of trees in total area a tried-and-true method, but plantations can also be expensive and ecologically insufficient in many environmental contexts (Murcia 1997;Souza and Batista 2004;Sampaio et al 2007;Rey Benayas et al 2008) since they still relies on natural processes, for example, the recovery of pollinators (Dixon 2009), seed dispersers, consumers and mycorrhizae (Ruiz-Jaen and Aide 2005; Brudvig 2011; Morrison and Lindell 2012). More than creating vegetative cover, the success of habitat restoration depends on the arrival of these wildlife colonists (Wunderle 1997;Scott et al 2001;Bowen et al 2007;Pinotti et al 2012;Chazdon 2014;Peña-Domene et al 2014).…”

Bats in the Anthropogenic Matrix: Challenges and Opportunities for the Conservation of Chiroptera and Their Ecosystem Services in Agricultural Landscapes

“…However, bats capable of gleaning insect prey from substrates exist throughout the world, and their impacts could be monitored via exclosure studies and disentangled from those of birds. This approach has been used fruitfully in the past five years, demonstrating significant increases in arthropod density when bats are absent, in agroecosystems (Williams- Guillén et al 2008;Maas et al 2013), reforestation (Morrison and Lindell 2012), and natural forests (Kalka et al 2008). In Mexican polycultural shade coffee, arthropod densities on coffee plants during the rainy season nearly doubled in the absence of bats, with marked increases in densities of hoppers, katydids, cockroaches, and beetles (Williams- Guillén et al 2008).…”

Landscape Context Mediates Avian Habitat Choice in Tropical Forest Restoration

“…Many tropical bird populations are in decline because of habitat loss [14], [15], but forest restoration aims to reverse this trend through gains in habitat [16]. Correspondingly, birds provide ecosystem functions that reduce biotic barriers to forest succession [17]–[19], including, seed dispersal [20]–[22], increased germination via gut passage [23], herbivorous arthropod control [24], and pollination [25], [26].…”