Effects of land-use and landscape characteristics on avian diversity and abundance in a boreal agricultural landscape with organic and conventional farms

Organic farming has been shown to be beneficial to many taxa associated with farmland habitats, but its importance in mosaic farmland landscapes is poorly understood. The impacts of organic farming have been suggested to be more pronounced in large-scaled homogeneous landscapes than in more heterogeneous mosaic ones, but studies conducted in wider landscape scale have remained scarce. We studied the effects of organic farming, landscape structure and agricultural land-use on field-dwelling farmland birds (14 spp.) at the species and assemblage level in a boreal farmland mosaic landscape (arable area ca. 20 km2), where organic farming comprises ca. 10% of the arable area. The analysis was conducted in a landscape scale using spatial regression methodology that incorporates spatial autocorrelation into models. Landscape structure and agricultural land-use were the principal determinants of the bird assemblage, whereas organic farming was favourable only to skylark and lapwing, but not to overall bird density, species richness, diversity or biomass. The species differed significantly in their habitat associations; however, agricultural grasslands strongly and positively determined the majority of the studied variables describing the bird assemblage. Since landscape structure and crop types are not necessarily included in organic regimes, we propose that considerable attention should be paid to make various crop and landscape types represented in organic regimes, particularly in mosaic landscapes.