Hummingbirds can use torpor to reduce their metabolic rates overnight as part of a strategy to manage daily energy balance or to maximize energy storage during certain life stages. However, the proximal mechanisms that trigger (or delay) torpor use, and how these vary temporally and in response to the environment, are poorly understood. While torpor may be used only when energy stores fall below a critical level, an ‘emergency only’ strategy may be abandoned to facilitate fat conservation during migration. We tracked body composition and torpor use in male ruby-throated hummingbirds (Archilochus colubris) throughout the breeding season and the beginning of the fall migration period using quantitative magnetic resonance, respirometry, and thermal imaging. During the summer, birds entered torpor at very low estimated fat stores (~5% of body mass). Interestingly, torpor use occurred repeatedly during the migratory period in birds that had accumulated high body fat stores (>25%). Additionally, hummingbirds decreased torpor duration, and increased torpor depth in the migration season. Overall, in the breeding season, leaner hummingbirds used torpor more often and longer, when their energy reserves approached a low emergency threshold. However, torpor use at high fat stores in the migratory season suggests that some individuals are also able to use torpor to facilitate storage of fat needed to fuel their migratory journey. This study explores individual variation in hummingbird torpor use to elucidate the mechanistic link between torpor use and seasonal changes in body composition.