Sexual maturity in Barn Owl (Tyto alba)

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 ...