The main aim of my work is to understand basic relationships between behaviour, hormones and reproductive success and how these relationships vary on a seasonal basis and in different environments. I am using birds as model systems to study the role of the steroid hormones testosterone and corticosterone as mediators of reproductive behaviours (e.g. territorial behaviour, song and parental care). My study sites lie in tropical East Africa and in temperate Europe. In particular, I currently study how life history variation has shaped variation in behaviour and physiology in stonechats and how habitat fragmentation and degradation affects behaviour, physiology and fitness of an East African cloud forest bird species.