Landscape composition is more important than local vegetation structure for understory birds in cocoa agroforestry systems

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Biodiversity-friendly agricultural systems allow the maintenance of native species even in highly fragmented landscapes by providing corridors to species dispersion and offering supplementary resources for animal populations. In the tropical region, cocoa agroforestry systems are of great importance for biodiversity conservation as they maintain part of the native vegetation, and therefore can be used by the local fauna. In this system, understory of native forests is replaced by cocoa trees, which are shaded by large old-growth trees. However, the persistence of native species in cocoa agroforests depends on local vegetation characteristics but also the landscape structure in which these systems are located. Here, we investigated the influence of landscape composition (i.e. amount of forest cover, cocoa agroforestry and cattle pasture) and local vegetation structure (i.e. number of native and cocoa trees, basal area of native trees and canopy closure) on understory birds in 18 cocoa agroforestry systems located in three regions in the Brazilian Atlantic forest, presenting distinct land use contexts. Specifically, we assessed the effects of these landscape and local features in predicting richness and abundance patterns of the entire community, and also in distinct ecological groups, such as forest-dependent and non-forest-dependent birds, and insectivores, frugivores, and omnivores. Using generalized linear models and Akaike information criterion, we observed lower species richness of complete community, non-forest and omnivorous birds in the most deforested region. Also, our findings demonstrated that cocoa agroforests integrated in more forested landscapes harbor greater richness and abundance of frugivorous birds. Conversely, the increase in cattle pasture amount at the landscape had a harsh effect on all bird groups evaluated. Regarding local vegetation, we observed that the increase of canopy closure leads to greater abundance of insectivorous birds in cocoa agroforestry systems. Similarly, abundance of non-forest species increased in agroforests with higher number of cocoa trees. Our study demonstrated that cocoa agroforestry systems can provide complementary habitats for many species, including forest birds, and therefore can mitigate the effects of habitat loss. However, this key benefit for bird conservation will be more effective when these agroforestry systems are located in more forested landscapes, with low amount of cattle pastures. Our findings therefore reinforce the alarming need to maintain and recover landscape-scale forest amount to ensure species persistence of birds in anthropogenic landscapes, even in those comprising biodiversity-friendly land uses such as cocoa agroforestry systems.