Identifying effective actions to guide volunteer-based and nationwide conservation efforts for a groundnesting farmland bird

International audience

anglais. 1. Modern farming practices threaten wildlife in different ways, and failure to identify thecomplexity of multiple threats acting in synergy may result in ineffective management. Toprotect ground-nesting birds in farmland, monitoring and mitigating impacts of mechanicalharvesting is crucial.2. Here, we use 6 years of data from a nationwide volunteer-based monitoring scheme of theMontagu’s harrier, a ground-nesting raptor, in French farmlands. We assess the effectivenessof alternative nest protection measures and map their potential benefit to the species.3. We show that unprotected nests in cultivated land are strongly negatively affected byharvesting and thus require active management. Further, we show that protection fromharvesting alone (e.g. by leaving a small unharvested buffer around the nest) is impaired bypost-harvest predation at nests that become highly conspicuous after harvest. Measures thatsimultaneously protect from harvesting and predation (by adding a fence around the nest)significantly enhance nest productivity.4. The map of expected gain from nest protection in relation to available volunteers’ workforcepinpoints large areas of high expected gain from nest protection that are not matchedby equally high workforce availability. This mismatch suggests that the impact of nest protectioncan be further improved by increasing volunteer efforts in key areas where they are lowrelative to the expected gain they could have.5. Synthesis and applications. This study shows that synergistic interplay of multiple factors(e.g. mechanical harvesting and predation) may completely undermine the success of wellintentionedconservation efforts. However, identifying areas where the greatest expected gainscan be achieved relative to effort expended can minimize the risk of wasted volunteer actions.Overall, this study underscores the importance of citizen science for collecting large-scale datauseful for producing science and ultimately informs large-scale evidence-based conservationactions within an adaptive management framework.