Today, most meadow-breeding birds are endangered due to mowing. The detection of their nests with the help of UAVs (unmanned aerial vehicles) promises less effort and disturbance. However, there are considerable uncertainties concerning the disturbance of the breeding birds. This article proposes an approach and presents first results on how the effects of disturbance caused by UAVs can be measured at breeding-bird sites on cultivated pastures. During the research project „FHprofUnt 2018: Farming 4.0 im Grünland“, the effects of disturbance by UAVs were investigated at different flight altitudes, by measuring the heartbeat-rate of a breeding Eurasian Curlew (Numenius arquata). In addition, the heartbeat-rate response caused by raptors flying over and other disturbances was measured. The results show that different flight levels of the UAV caused different heartbeat responses. Also, the increased heart-rates measured as a reaction to UAVs are comparable with responses to overhead raptors. In this article the method to investigate the heart-beat response and first results were presented. In the course of this Project further birds will be studied to increase the significance of the results. The selection of parameters regarding the disturbance of the birds is discussed.