What do crows in Vienna Zoo?

Corvids are renowned for making use of anthropogenic resources. Species like ravens and crows can often be found in and around human settlements, typically in groups of different sizes. Recent research indicates that these groups are not entirely anonymous crowds, as some individuals meet regularly at the same or at different locations. What causes birds to join, and stay, in a particular group is the topic of a current FWF-funded research program, whereby ravens are studied across the Northern Alps, and crows are studied within the city of VIenna. The objective of the present study is to include visitors of Zoo Vienna (Tiergarten Schönbrunn) in our scientific research on corvids via a citizen science approach. Specifically, citizen scientists shall investigate which species of wild crows regularly use the zoo, where the crows prefer to hang out in the zoo, and what the crows do at the different locations. The goal is to describe the grouping dynamics of crows in the different areas of Zoo Vienna and to test effects of environmental factors like food abundance and predation risk on the birds grouping behaviour. Interested visitors will be guided to actively engage in the monitoring of crows via a special app (crowdsourcing); they can also contribute to the improvement of the app and the refinement of research methods (participatory science) in the course of feedback rounds and special workshops.

Ravens and crows are renowned for using anthropogenic food sources. Although their foraging groups have a fluid character, with individuals coming and going, recent studies indicate that these groups are not entirely anonymous crowds. Some individuals meet regularly, possibly because they develop individual preferences for specific locations or for social constellations. What makes individuals join groups has been studied in ravens on a large geographical scale, across the Alps. We here use crows to study group choices on a small scale, as crows exploit various food sources in cities. The Zoo Vienna not only offers a variety of foraging opportunities for crows but also attracts thousands of visitors per day. We thus applied a Citizen Science (CS) approach to examine effects of foraging sites (enclosures with different zoo animals) on crows' group formation. Furthermore, we used the CS approach to focus on rare events like interactions between crows and zoo animals and to learn about the lay persons' ability to distinguish between different corvid species. Despite of severe restrictions due to Covid-19 pandemic, including four lockdowns in the course of a 2-year frame, the CS approach worked exceptionally well: zoo visitors got involved in data collection via the newly developed App "KraMobil", resulting in more than 17.000 entries over the summer period in 2020 and 21. While the analysis of this substantial data set is still ongoing, preliminary findings indicate that the foraging groups of crows are rather small, which fits well to previous studies on crows in Vienna zoo. We can also confirm the strength of the CS approach in detecting rare events: in comparison to the impressive number of 1042 sightings on inter-specific interactions collected via crowdsourcing in this project, two master students could previously only observe 19 of such cases within a similar observation period. Finally, a comparison between the species-detection data and the answers provided in a verbal survey among 230 people showed that participants were able to identify the crow species much better as they thought they would. Taken together, these findings reveal the attractiveness and appropriateness of the CS approach on behavioral studies in an urban setting like the Zoo Vienna. Follow-up studies are already in preparation.