Early‐life diet composition affects phenotypic variation of correlated animal personality traits

Behavioural traits are under both genetic and environmental influence during early life stages. Early environmental conditions related to the amount and type of food have been found to alter behaviour in many organisms. However, how early life diet affects the variation in and the correlation between behavioural traits is largely unknown. Using a multivariate approach, we investigated how variation in parental prey selection is related to three repeatable nestling personality traits, and explored the within and between-individual covariation between these behaviours in a wild passerine, the great tit (<i>Parus major</i>). Our results confirm that breath rate, docility and handling aggression (HA) in great tit nestlings are repeatable traits. Contrary to our expectation, the three nestling personality traits did not form a behavioural 'syndrome' on the phenotypic level in the study population, but we found two of three expected phenotypic correlations, mostly at the within-individual level. Moreover, we found that breath rate significantly decreased with a higher number of spiders in the diet, and docility and handling aggression were significantly and inversely related to higher numbers of noctuids and tortricids in the diets of individuals within broods. Thus, our findings suggest that provisioning quantity and quality during the early life, affects variation in behavioural phenotypes, which occurs mainly at the within-individual level.