Migration represents one of the most energetically demanding phases in the life cycle of long-distance migratory birds. Pre-migratory fattening is a critical preparatory stage characterized by hyperphagia, rapid fat accumulation, organ remodelling, and immune modulation. Although the gut microbiome has been recognized as a key contributor to these physiological adaptations, the role of the gut virome remains poorly understood. In this study, the diversity, functional potential, and temporal dyna