I am a behavioural and evolutionary ecologist with a strong interest in (quantitative) genetics, mostly using wild bird populations as model systems. I study individual variation in social behaviour from an eco-evolutionary perspective, with a focus on aggression, mate choice, parental care, and cooperation and conflict within the family. In my research, I combine diverse methods, ranging from behavioural observations and field experiments to using individual-based long-term population and pedigree data for quantitative genetic analyses. Ultimately, my research aims at understanding the eco-evolutionary causes and consequences of individual variation in behaviour and reproductive success (biological fitness).