Avian traits link divergent population responses to environmental change across North America

Birds are in decline globally. However, at finer spatial scales, species often exhibit notable geographic variation in how their populations are changing. Understanding why population trends vary within and across species remains a gap that impedes conservation. Here, we leverage over ½ million bird captures from 356 North American banding stations to derive temporal trends in local abundance and productivity for 46 species and examine whether 11 dimensions of environmental change explain geographic variation in species' population trends. We found that all species had local populations that were increasing, decreasing, or stable. Critically, we show that geographic variation in abundance and productivity trends is linked to changes in the local environment. While individual species vary markedly in their responses to different forms of environmental change, trait-based explanations reveal why this variation exists. Specifically, visual capabilities, aerial lifestyle, thermal niche, vocal characteristics, and life-history traits explain demographic responses to changes in light pollution, air pollution, temperature, human population, and land cover, respectively. These results support recent links between ecological traits and responses to global change, and by elucidating these relationships, we provide key information to forecast how understudied species will respond to environmental change. Furthermore, by identifying the most relevant forms of environmental change to individual species and where their populations are impacted, our results can inform policy. Importantly, multiple forms of environmental change in this study can be mitigated within local municipalities with existing solutions, indicating that high-impact conservation actions that have positive consequences for birds are within reach.