Variation in egg quality and composition in the Mallard Anas platyrhynchos.
Three complete Mallard Anas platyrhyncos clutches from a single site were analysed to determine intra-and inter-clutch variation within and among clutches in quality and composition. Variation between clutches was significantly greater than within clutches in all the examined criteria of egg composition, except for the percentage of water found in yolk. In addition the weight of the yolk was proportional to fresh egg weight. When log transformations were used, the slope of the regression was greater than unity, indicating the proportional contribution of yolk increased respectively with egg weight. A total of 26 eggs from four locations was analysed and no regional variation in egg composition was found but there was variation in egg quality (lipid and protein). The factors affecting the production of a ‘good egg’ and what in fact is a ‘good egg’ are discussed. In the Mallard, as in other Anseriformes, it appears that larger eggs may confer a survival advantage to the subsequent young.