Dependence of postjuvenile moult on hatching date, condition and sex in the Great Tit

We examined the influence of hatching date, nestling condition (body mass), size and sex on the age at the onset, and on the duration and extent of postjuvenile moult in a Great Tit population in southern Finland. Date of hatching explained most of the variation in moult parameters. Onset of moult was closely connected with hatching date: Great Tits from first broods started moulting in July and birds from second broods started in mid-august. The age at the start of moult decreased from 56 to 42 days from first to repeat and second broods and the duration of moult decreased from 67 to 59 days. Variation of moult parameters with date of hatching and the timing of moult are in concordance with experimental data on photoperiodic control of moult. Females started to moult older and moulted less extensively than males, especially in first broods. Residual body mass during moult reflected the state and intensity of moult, but did not correlate with the final extent of moult. This contradicts the recent protein stress and condition hypotheses.