The Bees Do It, but What About the Birds? Evidence for Sex Ratio Adjustment in Birds

Abstract

In birds, the female is responsible for determining the sexes of her offspring, and she accomplishes this by donating either a W or a Z chromosome to the egg. There is now a large body of evidence that female birds can adjust which sex chromosome the eggs receive in response to the social and/or environmental conditions surrounding them. In this chapter, I highlight the many factors that have been shown to influence avian sex ratios and highlight the need for a multipronged approach incorporating multiple life history traits when attempting to understand the adaptive significance of sex allocation in birds.