My broad research area involves the ecological and evolutionary processes that promote divergence in wild vertebrate systems. I am interested in the relative roles of microevolutionary processes that are responsible for phenotypic divergence and speciation. I take an empirical approach, focusing on avian groups to examine differentiation in both continental and island systems. I use a variety of methodologies to answer questions about processes of phenotypic and genetic differentiation, including studies of ecology, behaviour, morphology and population and quantitative genetics.