PhD ceremony: T. Limbourg, 13.15 uur, Academiegebouw, Broerstraat 5, Groningen
Thesis: Parental care in relation to offspring sex and mate attractiveness in the blue tit
Promotor(s): prof. M.E. Visser, prof. S. Daan
Faculty: Mathematics and Natural Sciences
Because investment in offspring is costly, individuals of the blue tit have to decide carefully how much energy they invest in current offspring and how much they retain for future offspring. An optimal allocation is dependent on the value of the offspring which is not equal for all young. Some will have higher chances of survival or will be more attractive and will therefore produce more offspring themselves. These offspring are of high value and suited for high parental investment.
One of the factors that might predict that success of the offspring is their gender. However, the research of Tobias Limbourg shows that sons and daughters in blue tits are equally fed by their parents. Next to that Limbourg found that feeding frequencies were also not related to the number of sons (the sex ratio) in the brood. But the relationship between feeding frequencies of males, but not of females, and sex ratio was different in each year of his research.
Another factor that determines the value of offspring is the attractiveness of the parents. Blue tits carry feathers on their head that reflect in the ultraviolet light (UV) and this is related to their attractiveness. As expected, Limbourg found that male and female parents adjusted their feeding frequencies to the attractiveness of their partner. Females fed their young more when the male was attractive and reflected a lot of UV. Males on the other hand fed less when their female had high UV, which suggests that males find this high UV unattractive in females.
