Breeding season management is unlikely to improve population viability of a data-deficient migratory species in decline

A major challenge in conservation is developing effective approaches to mitigate population declines in the face of ongoing environmental change. For migratory species, it is often more feasible to implement management during periods of stationarity, like the breeding season, when populations are less mobile. However, such management strategies are only successful if the demographic rates targeted (e.g., reproductive rates) contribute substantively to population growth. Thus, evaluation of population growth rate sensitivity to variation in demographic parameters is needed to determine the most effective conservation strategies. This is especially true for small and declining populations that require targeted and urgent action to mitigate declines under current and future environmental change. Here, we used a coupled integrated population model-Bayesian population viability analysis (IPM-BPVA) to estimate demographic rates and population viability within the context of climatic and management-related changes for a data-deficient, declining population of black terns in the Upper Midwestern United States. We found that current conservation efforts during the breeding season are unlikely to reverse the declines observed within the last decade (from an average of 307 breeding pairs in 2013 to 53 in 2022). Rather, interventions aimed at increasing adult survival are projected to reduce local extinction probability by 30-46 % compared to no additional management or management targeting other rates, depending on the climate scenario. Our results highlight the importance of enhancing management efforts for migratory species during migration and nonbreeding periods, which constitute a much larger, and generally riskier, proportion of the annual cycle compared to the breeding season.