Prairie strips as a mechanism to promote land sharing by birds in industrial agricultural landscapes

Reserving large patches of perennial vegetation has been shown to facilitate biodiversity conservation in industrial agricultural landscapes, but high demand for agricultural products challenges their establishment. Responding to this situation, in 2007, we experimentally integrated diverse native perennial vegetation (i.e., prairie) within annual row crops as a part of the Science-based Trials of Rowcrops Integrated with Prairie Strips (STRIPS) project in Iowa, USA. Four treatments were applied to small (0.47-3.19 ha) watersheds and included: 100% row crops (0% prairie) farmed on a soybean (Glycine max)-maize (Zea mays) rotation, and three treatments with prairie strips comprising 10% or 20% of the watershed area with the remaining area in row crops. This study evaluated bird response to these treatments between 2007 and 2012. We observed a total of 52 species using the experimental sites across six years of study, with 16 species comprising 99% of the observations. Bird abundance, species richness, and diversity positively responded to prairie within row-crop fields: we specifically recorded 1.53-2.88 times more birds, 1.53-2.13 times more bird species, and 1.40-1.98 times greater diversity in treatments with prairie compared to the 0% prairie control. Several generalist species - Eastern kingbird (Tyrannus tyrannus), American robin (Turdus migratorius), and common yellowthroat (Geothlypis trichas) - were statistically more abundant in treatments with prairie, and song sparrow (Melospiza melodia) were more abundant in one specific prairie treatment, whereas no species was statistically more abundant in the 0% prairie control. We found few differences between 10% and 20% prairie treatments, but recorded increases in bird abundance, richness, and diversity from 2007 to post-establishment years. This experiment suggests that incorporating prairie strips into annual row crops has the potential to increase agricultural land sharing by birds.