PhD project: A first realistic quantitative test of sex ratio modification theory in a wild population

During my PhD, I study the evolution of sex ratio modification. I try to understand why parents change the sex ratio of their offspring and why there is variation between individuals (i.e., why does not everyone produce a 50/50 sex ratio for example?). I study this in the Seychelles warbler (Acrocephalus sechellensis), which produces extremely skewed sex ratios under certain circumstances. I will make models to predict under what circumstances it is more beneficial to produce either sons or daughters. Subsequently, I will test if real-life individuals change their offspring sex ratio according to our models, and we will test the long-term fitness benefits of sex-ratio modification behaviour.