I am an integrative behavioural and evolutionary ecologist studying the evolution of social behaviour and life history patterns in social animals, with the goal of discovering why and how animals cooperate or compete with each other. My research focuses on behaviour as this is the level at which organisms interact most directly with their physical and social environment. I integrate empirical and theoretical studies to obtain deeper knowledge of the evolution of adaptive behavioural responses. I focus on long-term studies of wild birds in naturally varying environments; these are complemented with experimental studies at the individual and local population levels. Starting in 1985, I established one of the best known model systems in evolutionary ecology: the Seychelles warbler. Warblers normally produce one chick per nest and can be cooperative breeders, in which more than two individuals are engaged in raising the single offspring. My research focuses on two groups of questions:

1. What drives the evolution of group living and cooperative breeding?

2. What drives the evolution of sex allocation?

I publish regularly in the fields of evolutionary biology, behavioural biology, zoology, ecology, and genetics, but also in theoretical biology, biodiversity conservation, environmental sciences, immunology and endocrinology, and occasionally in psychology, molecular biology and medical science. Starting January 2020, I am a member of the Editorial Board of the journal Behavioral Ecology.