Virtually all animal species live in fluctuating environments. Although physiological and behavioral responses to changes in environmental conditions influence fitness outcomes, individuals from a population do not always respond similarly. To understand how individuals cope with changing environments, and whether their responses can allow populations to evolutionary adapt to global change, we need to quantify among- and within-individual sources of phenotypic variation. Using hand-raised great tits (Parus major) kept in outdoor aviaries, we measured individual responses in circulating corticosterone and hemoglobin concentrations, metabolic rate, and breath rate to a simulated cold spell, and in vertical flight performance to simulated molt. We assessed reaction norms repeatedly, in winter and spring of their first year of life and again at these same times in their second year of life. We focused primarily on trait plasticity, quantified as the reaction norm slope, and tested for its variation at the population-level, among-individual level and within-individual level, between seasons and years. We found that individuals differed in their degree of plasticity in corticosterone, breath rate and flight performance. Furthermore, individuals showed ‘’plasticity of plasticity’’ in most traits across seasons and years. Finally, plasticity was moderately to highly repeatable in all traits investigated. These findings suggest that: a) individuals can tailor their plastic responses to the ecological context; b) there is significant standing phenotypic variation in plasticity that could buffer the population from environmental variation; c) plasticity may be genetically determined and if targeted by selection, could enable evolutionary adaptation to global change.