Females produce more colourful eggs when males sing faster: My males song turns me on! (#401)
Maternal investment can play an important role for offspring fitness, especially in birds, as females have to provide their eggs with all the necessary nutrients for the development of the embryo. It is known that this type of maternal investment can be influenced by the quality of the male partner. In this study we first verify that male song is important in the mate choice of female Eurasian reed warblers, as males mate faster when they sing more complex. Furthermore, female egg investment varies in relation to male song characteristics. Interestingly, clutch size, egg weight or size, which can be considered as high-cost investment, is not influenced by male song characteristics, whereas comparably low-cost investment types like investment into diverse egg components are adjusted to male song characteristics. In line with this, our results suggest that female allocation rules depend on investment type as well as song characteristics. For example, egg white lysozyme is positively correlated to male song complexity. In contrast, a negative correlation exists between song speed and syllable repetitiveness and egg yolk weight as well as egg yolk testosterone concentration. Thus our results suggest that female egg investment is related to male song performance in several aspects, but female investment patterns regarding various egg compounds are not simply correlated.