Delayed maturation of plumage coloration and plumage spottedness in the barn owl (Tyto alba)

The Barn Owl (Tyto alba) varies in plumage from dark reddish-brown to white , and from heavily marked with black spots to immaculate. Males are commonl y lighter coloured and less spotted than females. I assessed whether male a nd female Barn Owls delay the full expression of plumage coloration and spo ttedness to the second year of life. In Switzerland, I quantified the two t raits of birds captured at the nestling stage, first, second and third year of life. Males and females became lighter coloured only from the first to the second year. Males became less spotted only from the first to the secon d year, and females less spotted from the nestling stage to the first year but more spotted from the first to the second year. Females were also simil arly spotted at the second and third year of age. By cutting off small piec es of feathers of females I could recognize which feathers had later been r enewed. After a complete moult old females did not change in plumage charac teristics.