The involvement of citizens in research projects led by professional scientists, a phenomenon known as citizen science, is increasingly rising. While advancements in information technology in the past few decades have fostered online participation, motivating participants is still a crucial aspect. With this respect, the phenomenon of nudging, i.e. directing citizens into better behaviors, attracted recent academic, managerial and political attention. With this study we would like to contribute to this stream of research evidencing that providing suggestions is more effective than shockvertising or forcing mechanisms when promoting and motivating citizen scientists towards behavioral changes. The technique of nudging is here experimentally ...