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.
Roulin
Alexandre
A
Department of Ecology and Evolution, Biophore, University of Lausanne, Lausanne, Switzerland. Alexandre.Roulin@unil.ch
D000375:Aging / Q000502:physiology; D000818:Animals; D003116:Color; D005241:Feathers / Q000502:physiology*; D005260:Female; D006321:Heart / Q000033:anatomy & histology; D008297:Male; D008543:Melanins / Q000502:physiology*; D009929:Organ Size; D010053:Ovary / Q000033:anatomy & histology* / Q000254:growth & development; D012098:Reproduction; D012727:Sex Characteristics; D020305:Strigiformes / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D013737:Testis / Q000033:anatomy & histology
D008543:Melanins; C018362:pheomelanin; C041877:eumelanin