Abstract
Sex allocation theory predicts that females mated to attractive males produce more sons than females mated to unattractive males. However, previous tests of this hypothesis have obtained mixed results. We suggest that females differ in the traits they find attractive. To test this proposition, we assessed female zebra finches’ preferences for males banded with red or green plastic leg bands and then tested the sex allocation pattern of females paired with preferred and non-preferred males. Although most females preferred red-banded males, 34% of females consistently preferred green-banded males. The sex ratio at laying and hatching was not influenced by paternal preferred status. However, the fledging sex ratios differed between females paired with preferred and non-preferred males due to sex-biased chick mortality; sons of females paired with preferred males were born heavier and were more likely to survive than daughters. Our results indicate that female zebra finches show individual variation in their preferences for colour banded males, although females do not seem to adjust the offspring sex ratio in response to their mate’s band colour. However, the differential post-hatch mortality suggests females may differentially allocate resources into male and female eggs according to their individual mate preferences.
