Future directions for bird-provisioned pest control studies in conventional agricultural systems

Agricultural expansion is a major conservation threat to birds and other taxa. Paradoxically, birds may provide an important pest-removal service to farmers. Historical interest in biological control by birds waned after the advent of synthetic pesticides in the 1920’s, but interest is once again increasing as people search for a sustainable way to both feed a growing population and conserve biodiversity. Most of the current research on biological control by birds in agriculture takesplace in “wildlife friendly” and tropical systems, where birds have found to be effective at removing pests. However, in the US, large conventional farms comprise most of the cultivated land area. Conventional farms differ from wildlife-friendly farms in their structural, floristic, and landscape complexity and in their resulting bird communities. Nevertheless, birds may provide equally significant pest control services on conventional farms. Ecological theory suggests that the strength of top-down effectswill increase with (1) increasing plant productivity, (2) little intra-guild predation, and (3) niche complementarity among predator species. Conventional farms may fit these criteria for strong top-down effects well. I address future directions for bird pest control services research, and present preliminary results from a study in conventional agriculture. More study is needed to determine the existence and/or strength of these ecosystem services in conventional agriculture, and how they are distributed within and among farms. With this information, we can determine whether some of the negative impacts of conventional farming can be reduced by encouraging birds on farms, decreasing pesticide use, and maintaining crop yield.