MASS-CHANGE DURING MOLT IN THE GREAT-TIT PARUS-MAJOR

Changes in mass during moult were investigated by analysis of data rec orded on standard moult cards by members of the British Trust for Orni thology Ringing Scheme, In the analysis of post-juvenile moult, all av ailable cards that presented wing length, mass and time of capture wer e used. The analysis of adult post-nuptial moult was restricted to car ds from a single year. Juvenile mass correlated strongly with body siz e, 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 t o 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 sco res of primary, secondary and tertial remiges and of rectrices but bec ause of the strong correlations between moult scores and date, the tru e relationship was not clear. In adult females, mass declined with dat e before increasing again. Unlike the males, female moult scores did n ot predict body mass. However, the timing of moult was a strong predic tor of body mass. The differences between age and sex groups are discu ssed in relation to the nutritional demands of moult.