Gottwald, I.; Steindl, S.; Strasser, F.; Kiesel, M.; Rainer, H.; Haring, E.; Kapun, M.

To efficiently mitigate biodiversity loss both robust ecological data and broader societal engagement are needed. Citizen science offers a pathway to address these dual challenges by combining data collection with public involvement. Here, we introduce the citizen science project Vienna City Fly, conducted at the Natural History Museum Vienna (NHMW), which used fruit flies (Drosophila) as a model organism group for urban biodiversity research and public engagement. Participants deployed standardized traps across Vienna, enabling systematic sampling and active participation in research, which resulted in hundreds of fly collections, thousands of sampled fly specimens and new insights into the biodiversity and ecology of the collected fly species, demonstrating the feasibility of large-scale ecological research through public collaboration. To assess motivational drivers and perceived impacts of participation, we conducted an online survey (N=59) using the validated psychometric MORFEN-CS scale. Survey results revealed that nature conservation values and the intention to contribute to biodiversity conservation emerged as the strongest drivers of engagement, complemented by sociopolitical responsibility and citizen science-based motivations. Reported outcomes include knowledge gain (61%), more positive attitude toward study organisms (50%), and increased awareness of biodiversity (30%). Satisfaction was very high, with 85% rating their experience at the top of the scale and all participants expressing willingness to join future citizen science projects. Recruitment occurred mainly via social networks, and the sample of participants was highly educated, indicating limits to inclusivity and reach. Our findings demonstrate that citizen science can contribute to robust ecological data collection while gaining knowledge and awareness. Natural history museums, as trusted institutions, play a key role in facilitating such initiatives. Overall, Drosophila research proves to be a suitable field for citizen science, combining accessibility with strong potential for advancing ecological and biodiversity research as well as public engagement in urban biodiversity research.