Complex landscapes stabilize farm bird communities and their expected ecosystem services.
Abstract
Birds play many roles within agroecosystems including as consumers of crops and pests, carriers of pathogens and beloved icons. Birds are also rapidly declining across North America, in part due to agricultural intensification. Thus, it is imperative to identify how to manage agroecosystems to best support birds for multi-functional outcomes (e.g. crop production and conservation). Both the average amounts of services/disservices provided and their temporal stability are important for effective farm planning. Here, we conducted point count surveys for 4 years across 106 locations on 27 diversified farms in Washington and Oregon, USA. We classified birds as ecosystem service or disservice providers using indices spanning supporting, regulating, provisioning and cultural services/disservices. We then examined service/disservice index pairwise correlations and assessed the relative importance of local, farm and landscape complexity on the average and temporal stability of avian service/disservice provider indices. Generally, service provider indices (production benefitting birds, grower appreciation and conservation scores) were positively correlated with each other. Foodborne pathogen risk, grower disapproval and identity/iconic value indices were also positively correlated with each other. However, the crop damaging bird index generally had low correlations with other indices. Farms that implemented more conservation-friendly management practices generally had higher average service provider indices, but farm management did not impact disservice provider indices, except for grower disapproval. Average disservice provider indices were lower on farms in complex landscapes. Local vertical vegetation complexity tended to increase the temporal stability of service provider indices but did not affect the disservice provider indices. Greater landscape complexity was generally associated with increased temporal stability of service and disservice provider indices. Increased landscape complexity may stabilize bird communities by increasing bird community evenness, which in turn, positively predicted temporal stability of all service/disservice provider indices. Policy implications. Our results suggest that farmers can effectively manage their farms to harness ecosystem services from birds through farm diversification. Disservices provided by birds, however, appear to be most negatively impacted by landscape-level complexity. Thus, greater incentives for farmers to increase semi-natural cover at the landscape scale are likely necessary to achieve multifunctional outcomes for conservation and agriculture.