Dominance rank and offspring sex ratios in domestic fowl

Research on both mammals and birds suggests that parental features, such as body condition and dominance rank, could influence sex ratios. This study examined the effect of male and female dominance rank on hatching sex ratios in domestic chickens, Callus gallus domesticus. Twenty-four dominant males and 24 subordinate males were each placed in a pen with eight females. Females that were mated to a dominant male in the first 3 weeks of the experiment were mated to a subordinate male in the second 3 weeks and vice versa. Sex ratios (number of females/male) at hatch were not directly affected by male and female dominance status. Females that were mated to a subordinate male in the first trial, however, produced more variable sex ratios in the second trial. This effect was not evident for females mated to dominant males first. In addition, both groups of females produced more daughters in the second trial than in the first, although this effect was only significant for females that mated with subordinate males first. The results did not support the hypothesis that females should alter the sex ratio of their offspring based on their own dominance status or that of their mates. They did provide evidence, however, that sex ratios in chickens may be indirectly influenced by the status of the male.