Research interests
I have broad research interests in ecology and evolution, with the main emphasis currently on the following five themes.

Climate change and its ecological and evolutionary consequences. Rapid climatic change has affected numerous living beings, although the long-term consequences for individuals, populations and species remain poorly understood. I have personally worked on long-term projects on birds and their parasites since 1971. Together with Prof. P. Berthold and Dr. W. Fiedler, I am currently co-editing a book on birds and climate change to be published by Oxford University Press in 2010.
Ecological and evolutionary consequences of Chernobyl. The nuclear reactor disaster at Chernobyl 26 April 1986 caused radioactive contamination of vast areas in Ukraine, Belarus and Russia. Highly heterogeneous levels of contamination provide a unique opportunity to do research on the consequences of radiation including effects of radiation on mutation rates and adaptation to radiation. Together with Prof. T. A. Mousseau I am currently working on birds, insects and plants.
Parasite-host coevolution. Parasites constitute important selective forces affecting all living beings, with consequences for life history, sexual selection and interactions among species. I am working on parasite-host interactions, including interactions between cuckoos and their hosts, the micro-organism communities of birds, and the causes and consequences of host immune responses.
Sexual selection and the evolution of secondary sexual characters. I have broad interests in the evolution and the maintenance of secondary sexual characters, and the evolution of signals and their information content. I have pursued these interests in long-term studies of several populations of barn swallows, but also in comparative analyses.
The ecology and evolution of urbanization. Large areas are currently being urbanized, and this tendency will continue for at least the next century. Adaptation of living beings to this novel environment characterized by long growing seasons, high productivity and high levels of pollution provides a unique opportunity to investigate evolution in action. I have established a European network on urbanization of birds to investigate these questions.