Semi-natural habitats on organic strawberry farms and in surrounding landscapes promote bird biodiversity and pest control potential

Agricultural intensification and expansion have degraded biodiversity in agroecosystems, jeopardizing the ecosystem services provided by wildlife. Birds can act as particularly important purveyors of ecosystem services to farmers by consuming arthropod pests. Some bird species, however, may sometimes act as pests themselves by consuming crops. Further, on-farm management practices (e.g., crop diversity, vegetative structure) and the complexity of the surrounding landscape can shift the balance of bird-mediated ecosystem services and disservices through changes in bird community composition. Here, we explored how organic strawberry farms in California could be managed to bolster bird biodiversity and shift community composition from strawberry-consuming to pest-eating species. Using multi-species N-mixture models we found that semi-natural habitat at the landscape (1000 m) and farm (50 m) scales were positively associated with mean abundance of all birds, with varying effects on different species. In particular, we found that the mean local abundance of species that consume Lygus spp. (a major pest), but not strawberry-consuming species, increased with semi-natural habitat at the farm scale. Nest density in developed areas within farms also increased with greater semi-natural habitat in the landscape, while nest density in semi-natural habitat within farms decreased with increasing semi-natural habitat in the landscape. Further, nest density of Lygus spp. eating birds increased with increasing local semi-natural habitat. These results suggest that increasing semi-natural habitat at the landscape and local scales can bolster bird abundance across farms, while pest control can be promoted locally by conserving or restoring semi-natural vegetation at the farm scale.