Mass-change during moult in the Great TitParus major

Open Access
Publisher Website
Google Scholar
Abstract
Changes in mass during moult were investigated by analysis of data recorded on standard moult cards by members of the British Trust for Ornithology Ringing Scheme. In the analysis of post juvenile moult, all available cards that presented wing length, mass and time of capture were used. The analysis of adult post-nuptial moult was restricted to cards from a single year. Juvenile mass correlated strongly with body size, time of day and the number of greater coverts being replaced. After controlling for the effects of size and time of day, mass was found to increase with date except in those individuals in which all juvenile greater coverts were retained. In these birds residual mass declined with date. In adult males, mass increased with both date and moult scores of primary, secondary and tertial remiges and of rectrices but because of the strong correlations between moult scores and date, the true relationship was not clear. In adult females, mass declined with date before increasing again. Unlike the males, female moult scores did not predict body mass. However, the timing of moult was a strong predictor of body mass. The differences between age and sex groups are discussed in relation to the nutritional demands of moult.