Sexual maturity varies with melanic plumage traits in the barn owl

Abstract

The age at first reproduction can significantly impact fitness. We investigated the possible source of variation in the age at first reproduction (‘sexual maturity') and its consequences for lifetime reproductive success in a wild population of barn owls. This raptor is sexually dimorphic for two melanin‐based plumage traits shown to covary with sex‐specific behaviour and physiology. We observed that females were sexually mature earlier than males, an effect that depended on the colour of their plumage and birth date. Among females born early in the season, dark melanic (i.e. more pheomelanic with large and many black feather spots) yearlings were sexually mature earlier than light melanic females. The relationship was in the opposite direction in those born late in the season. In yearling males, the opposite result, albeit less pronounced, was discovered, i.e. lightly melanic males born early in the season were sexually mature earlier than dark melanic males, an effect that was in the opposite direction in males that were born late in the season. Individuals that matured faster produced a larger number of fledglings per year than individuals that matured slower, an effect that was found only in dark melanic females and in light melanic males. Dark melanic females also achieved a higher lifetime reproductive success (LRS) than light melanic conspecifics. Our results suggest that a light melanic plumage is beneficial in males and a dark melanic plumage in females suggesting sexually antagonist selection.