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Population Dynamics of Breeding Waterfowl

V. Egg Survival

C. Sex Ratio of Hatching Young

There is no evidence that primary sex ratios (at fertilization) of ducks differ from 50:50 (Bellrose et al. 1961). The secondary sex ratio (of newly hatched young) of four species of ducks showed a slight preponderance (51.8%) of males (Sowls 1955:164). Correspondingly, Hochbaum (1944:51) reported that females made up 52.7% of dead Canvasback embryos. LeBlanc (1987b) found a preponderance of males (54.1%) from five- and six-egg clutches of Canada Geese that were recaptured at six to eight weeks of age. Harmsen and Cooke (1983) found for Snow Geese not only gosling sex ratios very near 50 %, but also binomial variation among clutches, suggesting that females do not carry mutations tending to favor production of one sex. Ankney (1982) noted a relationship among Snow Geese between egg sequence and sex, with the first two eggs in a four-egg clutch more likely to produce males and the last two females.

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