Data from: Maize-field complexity and farming system influence insectivorous birds’ contribution to arthropod herbivore regulation

The contribution of insectivorous birds to reducing crop damage through suppression of herbivory remains underappreciated, despite their role as cropland arthropod predators. We examined the roles of farming system crop cover pattern and structural configuration in influencing assemblage composition of insectivorous birds and their herbivorous arthropod prey across maize fields, and determined how bird exclusion affects crop herbivory levels. To achieve these objectives, data were collected across a sample of organic and conventional small-scale non-Bt maize farms in western Kenya. Assessments of abundance, diversity and richness of insectivorous birds, and abundance of their arthropod prey, were compared between organic and conventional small-scale non-Bt maize on monocultured and intercropped farms. We also employed bird exclusion experiments to assess impacts of bird predation on herbivorous arthropod abundance. Results showed that higher structural heterogeneity supported higher insectivorous bird richness, particularly under organic systems, dense trees, large woodlots and thick hedgerows. Bird abundance further increased with crop diversity but not in relation to cropping method, hedgerow type or percent maize cover per se. Conversely, herbivorous arthropod abundance and richness increased on conventional farms and those with higher percent maize cover, but were unaffected by cropping methods, tree or hedgerow characteristics. Birds’ arthropod prey were more abundant under completely closed compared to open or semi-closed plots, confirming a significant linkage between birds and herbivorous arthropod suppression. In this study, we demonstrate importance of structural heterogeneity in agricultural landscapes, including diverse croplands and on-farm trees to maximize insectivorous birds’ contribution to reducing crop arthropod herbivory. Bird encounter incidents across the farms surveyedSpecies of insect-eating birds that were encountered across all farms. List includes generalist species that consume insects and other food typesEstimated global populations per hectare of bird species fro each farm from DistanceEstimated population of bird species across the entire collection of farms studied. Population estimate are per hectare and are derived from the DISTANCE protocol, projected from regional average estimates for each of the farms surveyed