Northern Prairie Wildlife Research Center
Population Dynamics of Breeding Waterfowl
IV. Clutch Size and Egg Size
Much debate remains about the factors ultimately limiting clutch size and causing its seasonal decline in waterfowl. Our review suggests that the physical condition of the laying female is a primary proximate determinant in some species. Condition is in turn affected by food supplies, age, and other variables. Drent and Daan (1980) proposed that smaller clutch sizes are optimal for some individuals of a population (late arrivals, or those with inexperienced mates or in marginal habitat) because these females would potentially suffer a greater decline in survival by producing more eggs than would a female in a better situation. Genotypic variation has also been demonstrated, and parasitism, where it occurs, has an additional effect.
Survival of young hatched from larger eggs may be enhanced in certain situations, but the determinants of egg size are unclear.
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