Factors influencing abundance of butterflies and burnet moths in the uncultivated habitats of an organic farm in Denmark

Biotic and abiotic factors causing aggregations of butterflies were investigated in a variety of uncultivated habitats on an organic farm in Denmark. By combining the method of butterfly transect counting with multiple regression analysis, environmental and floral variables influencing butterfly abundance in linear and non-linear uncultivated habitats were identified. Dependent variables were: butterfly totals, Thymelicus spp. (mainly T. lineola), Aphantopus hyperantus, Maniola jurtina, Pieris rapae/napi and four mobility groups. In linear habitats, environmental variables of major importance were: insolation, width of non-crop ground vegetation and abundance of nectar sources, while in non-linear habitats these were: larval host plants, presence of stream and degree of grazing. Among the preferred nectar sources were: Knautia arvensis, Trifolium pratense, Cirsium spp. and Hieracium pilosella. Most butterfly species had significantly higher abundances in non-linear habitats compared to linear habitats. The impact of different environmental and floral variables on the butterfly fauna is discussed, emphasizing the major importance of certain habitat types and characteristics for the butterfly species inhabiting uncultivated habitats surrounded by cultivated fields. (C) 2001 Elsevier Science Ltd. All rights reserved.