Enhancing Knowledge about the Lesser Spotted Woodpecker Dryobates minor in Southern Germany, with Citizen Science

Monitoring is essential in conservation biology for assessing a species' population status and development. Many broad-scale programs rely on citizen science approaches but surveying rare or elusive species often requires specific training for volunteers. The Lesser Spotted Woodpecker Dryobates minor is an indicator of healthy forest ecosystems, particularly structurally rich deciduous and riparian forests. The species is difficult to observe due to its elusive behaviour, making reliable information about population status and habitat requirements scarce. Recognizing this critical data gap, a citizen science project was initiated in Hesse and Bavaria, Central and Southern Germany. The project, integrated into the national monitoring of rare breeding birds, trained volunteers to systematically map this species. Monitoring was conducted from 2021 to 2024 along 187 monitoring transects using playbacks to lure woodpeckers and the NaturaList app to record observations. Additionally, habitat data, such as the number of dead trees, proximity to water bodies and habitat type, were collected. Cavity cameras were used to monitor active breeding cavities. Lesser Spotted Woodpeckers were detected during 323 of 1012 surveys (32%), with detection probability peaking in March. The prior bird knowledge of the citizen scientists positively influenced detection probability. Species occurrence probability was highest in deciduous, riparian, and mixed forests characterized by large amounts of standing dead trees. Nest survival was 74%, with 1.8 fledglings per brood on average. Predators included Great Spotted Woodpeckers Dendrocopos major, and Garden Dormice Eliomys quercinus. Nest survival increased with the number of standing dead trees in the vicinity of breeding cavities. These findings emphasize the importance of deciduous forests and standing deadwood in supporting the species' occurrence and nest survival and highlights the value of citizen science as powerful tool for generating large-scale data, enabling more effective long-term monitoring of elusive species.