My main research interest is to understand the ways in which animals are physiologically organized depending on the environment in which they live. I focus on three physiological systems: i) reproduction, ii) endocrine control mechanisms, and iii) the circadian system. To study physiological adaptations, I compare bird populations across latitudes, both intraspecifically (using great tit, Parus major, populations across Europe) and interspecifically (temperate versus tropical birds). My research integrates physiology, ecology and evolution and is aimed at a functional understanding of short- and long-term animal-environment interactions.