<p>Global habitat loss and urban expansion are intensifying human–wildlife conflicts worldwide, particularly involving migratory birds that cause harm through fecal contamination, aesthetic degradation, and the risk of disease transmission, yet remain challenging to manage due to their broad-scale movements. We investigated the migratory connectivity and migration patterns of the Eastern Rook (<i>Corvus frugilegus pastinator</i>), an urban-adapted species that has become a major source of conflict with residents in Korea. Using hydrogen stable isotope (δ²H) and mitochondrial DNA analyses, we examined 66 carcasses from four wintering sites in Korea. Feather δ²H values did not differ significantly among wintering sites, and isoscape-based assignment revealed broadly overlapping breeding origins around the Mongolia–Russia and China–Russia border regions. No clear latitudinal trend in breeding origins was detected, suggesting the absence of chain migration. Adults consistently had higher δ²H values than first-winter individuals, likely reflecting age-related differences in molt timing and location. Genetic analyses revealed high intermixing among wintering populations, with no evidence of distinct population structure. Together, these findings suggest that Korean wintering rooks constitute a diffuse population, implying that localized lethal control is unlikely to be effective. Non-lethal strategies, including habitat modification, alternative roosting sites, and deterrence measures, should be prioritized to mitigate conflicts.</p>