Figure 1.

Variation in the time of completion of the moult into nuptial plumage. (a) Frequency distribution across all years. The shading depicts five classes of males used in statistical analysis. The peak at eight weeks refers to males that have used the post-breeding moult to renew their nuptial plumage. The peak at 48 weeks refers to males that failed to achieve full nuptial plumage. Only a very small number of males (at 52 weeks) never moulted. (b) The effect of age of the male on the probability of early moult (N=sample size for each age class). (c) The effect of summer rain on the probability that birds at least 4 years of age will moult early (N=sample size of older birds in each season).