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 po stjuvenile moult in a Great Tit population in southern Finland. Date of hat ching explained most of the variation in moult parameters. Onset of moult w as closely connected with hatching date: Great Tits from first broods start ed 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 repea t 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 moul t are in concordance with experimental data on photoperiodic control of mou lt. 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 o f moult. This contradicts the recent protein stress and condition hypothese s.