From nestling to adult: personality traits are consistent within but not across life stages in a wild songbird

Personality traits can remain consistent throughout adult life, but it is less clear when these behavioural differences first arise and whether they are maintained across ontogenetic stages. We measured personality across three life stages (nestling, fledgling, and adult) in a wild population of superb fairy-wrens (Malurus cyaneus). We assessed (1) boldness (response to human handling, at all three stages), (2) exploration (response to a novel environment, in fledglings and adults) and (3) aggressiveness (response to mirror-image stimulation, in fledglings and adults). Personality differences were often consistent within life stages but never across them: specifically, aggressiveness was repeatable in fledglings and all three traits were repeatable in adults. We had insufficient statistical evidence for the presence of behavioural syndromes between any of our three personality traits, either at the fledgling or adult stages. Our results suggest that long-term personality traits may not become entrenched until adulthood in this species.