Positive Auswirkungen des Ökolandbaus auf Vögel der Agrarlandschaft – Untersuchungen in Schleswig-Holstein auf schweren Ackerböden

Summary

In 2001 to 2003 numbers of breeding birds were recorded on sample plots of the Federal Institute of Organic Farming in Trenthorst (Schleswig-Holstein, Germany), an adjacent conventional farm and on a field with long time organic farming. A complete breeding bird survey during the transition phase from conventional to organic farming in 2001 revealed a rich avifauna of hedgerows and woodland and a relatively poor avifauna of open fields. The number of Skylark territories on the plot of the Institute increased considerably after the conversion from conventional to organic farming whereas the numbers of territories on the control plot with conventional farming remained stable. The highest density of Skylark territories was found on the plot which had been part of an organic farm since many years. The numbers of Yellowhammer territories fluctuated largely in parallel to the availability of field margin strips both on the conventional and the organic plots. During the breeding season both aerial hunters (swallows and swifts) and raptors significantly preferred organic fields over conventional fields. Outside the breeding season, densities of raptors (in autumn and in winter), seed-eating birds (in autumn) and insect-eating birds (in autumn) were significantly higher on organic than on conventional plots. Organic fields more often held stubbles and/or green vegetation in the non-breeding season. On organic farms, carnivorous birds had significantly higher densities both on fields with stubbles and green vegetation. Granivorous birds had significantly higher densities on stubble fields and insectivorous birds had higher densities on fields covered by green vegetation. There was a significant positive correlation between density of seed mass and density of granivorous birds.