Context-specific repeatability of personality traits in a wild bird: a reaction-norm perspective

Animal personality is defined as behavior that is consistent across time and context. We here applied a reaction-norm perspective implemented as a random regression phenotypic model (RRPM) to behaviors measured on blue tits Cyanistes caeruleus. During 3 consecutive breeding and winter seasons (2007–2009), a total of 508 wild-caught blue tits were assayed in a standard, artificial setup (a bird cage) for 1) activity, 2) time to escape, and 3) neophobia-related behavior. Activity was found to be repeatable both within and across seasonal contexts, but escape time and neophobia-related behavior were repeatable only in winter. Our RRPM confirmed that this latter finding was due to crossing of the individual-specific reaction norms between the 2 seasonal contexts. Our work illustrates how a behavior measured in a standardized manner may or may not be repeatable across time within a context but not between contexts, depending on the interindividual variation in reaction-norm properties. Our findings suggest that research on animal behavior plasticity can benefit from taking onboard context-specific analyses in a more explicit manner than what is typically done.