Abstract
Behavioural plasticity is an important mechanism allowing animals to cope with changing environments. Theory has hypothesized the existence of ‘plasticity syndromes’—positive correlations in plasticity across multiple behaviours within an individual—affording a generalized ability to respond to environmental change. However, the occurrence of correlated plasticities and their potential fitness consequences in natural populations remain untested. Using a 40‐year dataset on free‐ranging Magellanic penguins, we find evidence of both positively and negatively correlated behavioural plasticities. Plasticity did not strongly affect lifetime reproductive success, but its effect on interannual performance varied significantly by environmental context: plasticity reduced success in average oceanic conditions, increased success in anomalously productive conditions and, contrary to expectation, did not buffer against anomalously unproductive conditions. Such results highlight the complex patterns and consequences of plasticity across behaviours, individuals and environments, and the context‐dependent role that correlated plasticities play in the adaptive capacity of populations to environmental change.