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Animal tracking has become an effective way to identify where and when migratory species encounter threats throughout their annual cycle. Yet, untracked or poorly tracked species and undiscoverable or inaccessible data for the species that have been tracked mean that gaps in the knowledge of where and when species occur are still an issue for conservation. These gaps in knowledge of species movements have been termed the “movement shortfall”. Here, we quantify the movement shortfall for North American migratory birds by comprehensively reviewing full annual cycle tracking data and identifying gaps and biases in how, where, and what species are tracked with electronic tracking devices. We found 30 species for which tracking is not feasible given body size constraints, no data for 291 trackable species, and restricted or reduced data accessibility for an additional 59 species. Thus, despite the ability to …