Abstract
Farmland bird populations in Europe have experienced a decline the last forty years due to agricultural intensification and land abandonment. This included Yellowhammer (Emberiza citrinella) populations. Yellowhammer population decline have been monitored in the period between 2000-2017 by the Norwegian monitoring programme for agricultural landscapes. This study investigates if specific land type combinations, climate variables, together with geographic location can explain yellowhammers distribution and abundance in Norway. A generalized additive binomial model was used to explain yellowhammer distributions. This showed that this species distribution had become more restricted throughout the monitoring period, and that geographic location and land type combinations were significant. For yellowhammer abundance a generalized additive quassi-Poisson model was the most adequate, showing that yellowhammer abundance declined in the monitoring period. In addition, geographic location and land type combinations were also significant in the abundance model. Both models showed that land types had a stronger explanatory effect than climatic variables. The distribution model was considerably more accurate than the abundance model. This was probably due to a low amount of observations of yellowhammer in each monitoring plot every year. This study confirms the importance of having long time series data of farmland birds, and that the conservation of cereal crops and vegetation around fields in the Norwegian agricultural landscape is important for good nature management.