Breeding prerequisites for ortolan bunting emberiza hortulana in Swedish farmland, with special focus on foraging

Abstract

ORTOLAN BUNTINGS are rapidly decreasing in Sweden, mainly due to changes in agricultural practices. Landscape simplification due to the removal of semi-natural elements leads to a lack of breeding habitats. Furthermore, due to intensive artificial fertiliser applications and advanced agricultural equipment and technology, crops grow taller and denser than 50 years ago. In Kvismaren, south central Sweden, Ortolan Buntings have been studied since 2009. Here, we focus on one question: what defines a good foraging microhabitat? In 2017, five nests were located, and we made 271 observations of feeding parents. Average foraging distance at different nests varied between 47 and 114 m. About 70 % of the foraging activities took place within crop fields. Ortolans mainly utilized unsown rows, that tractors later follow during e.g. spraying, and patchy parts of standing crops. Invertebrates extracted from those areas looked dark, suggestive of ground-dwelling species. Our management recommendation to leave two unsown rows (amounting to 37.5 cm in width) to create better microhabitats can be achieved by most farmers, but might not be sufficient to maintain the population. No conservation efforts of a reliable positive effect are known to date.