Within-clutch variability in shape of 1743 eggs from 301 nests of Emperor Geese (Chen canagicus) laid over a 5-yr period was measured. Individual females laid similar shaped eggs in successive years, and eggs among clutches within females could not be distinguished. Cluster analysis correctly identified 69.9% of 136 known conspecific parasitic eggs. Repeatability estimates of elongation (0.73), sphericity (0.72), maximum width (0.69) and radius of the point (0.68) were high and similar to repeatability estimates of egg mass and volume of other species. Although width, volume and area measurements varied inversely with spring population size, shape variables did not. The consistency in shape variables despite changes in egg size suggests that shape variables may be used to separate and identify individuals within and among years despite changes in the population that may result in changes in egg size. Differences in egg shape among eggs within a nest are viable criteria for identifying parasitic eggs, especially when used in conjunction with other methods.
