1. Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK (, )
2. Avian Science Research Centre, Scottish Agricultural College, Ayr KA6 5HW, UK ()
3. Laboratoire d'Ecologie, CNRS UMR 7625, Université Pierre et Marie Curie, 7 quai St Bernard, Case 237, F-75252 Paris Cedex 05, France ()
4. Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK ()