Sexual selection is widely viewed as one of the major mechanisms of evolution and impacts on a wide range of organisms’ traits from the genomic level to social behaviour. Here I propose a multidisciplinary research programme that combines the approaches and tools of evolutionary biology, brain research and advanced phylogenetic statistics to investigate three fundamental but controversial aspects of sexual selection. First, the causative relationship proposed between the intensity of sexual selection and the disparity in parental care between the sexes is ambiguous. Using a large dataset on reproductive behaviour, ecology and life history of birds and new directional comparative methods I will test whether evolutionary changes in intensity of sexual determines parental care patterns or vice versa. Furthermore, I will test new hypotheses on the relationships of sexual selection to finer components of care, and also to parental sex roles, not investigated by earlier works. Second, I will conduct new analyses on how sexual selection affects (or is affected by) brain size evolution, including tests to explore causative relationships between these traits and also between brain size and parental sex roles. Finally, I will investigate how sexual selection affects the rates of phenotypic changes, that is important for the understanding of basic evolutionary processes (e.g. speciation) but has been rarely estimated empirically by comparative studies. The proposed projects will provide an excellent opportunity to learn new research methods and to produce new and valuable scientific results in the field of evolutionary biology. The Fellowship will also strength my research management and communication skills, and increase my general knowledge on international science that is essential for my future academic career from running independent research to high quality teaching.