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
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.