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Melanin-based coloration covaries with ovary size in an age-specific manner in the barn owl.
While the adaptive function of black eumelanin-based coloration is relatively well known, the function of reddish-brown pheomelanin-based coloration is still unclear. Only a few studies have shown or suggested that the degree of reddish-brownness is associated with predator-prey relationships, reproductive parameters, growth rate and immunity. To gain insight into the physiological correlates of melanin-based coloration, I collected barn owl (Tyto alba) cadavers and examined the covariation between this colour trait and ovary size, an organ that increases in size before reproduction. A relationship is expected because melanin-based coloration often co-varies with sexual activity. The results showed that reddish-brown juveniles had larger ovaries than whiter juveniles particularly in individuals in poor condition and outside the breeding season, while in birds older than 2 years lightly coloured females had larger ovaries than reddish-brown conspecifics. As barn owls become less reddish-brown between the first and second year of age, the present study suggests that reddish-brown pheomelanic and whitish colorations are associated with juvenile- and adult-specific adaptations, respectively.
Aging/physiology, Animals, Color, Feathers/physiology, Female, Heart/anatomy & histology, Male, Melanins/physiology, Organ Size, Ovary/anatomy & histology, Ovary/growth & development, Reproduction, Sex Characteristics, Strigiformes/anatomy & histology, Strigiformes/growth & development, Testis/anatomy & histology
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