1. Department of Genetics, Evolution and Environment; University College London; Gower Street London WC1E 6BT UK
2. Bird Group; Department of Life Sciences; The Natural History Museum; Akeman Street Tring Hertfordshire HP23 6AP UK
3. Terrestrial Ecology Research Group; Department of Ecology and Ecosystem Management; Technische Universität München; Hans-Carl-von-Carlowitz-Platz 2; D-85354 Freising-Weihenstephan Germany
4. Ornithology Section; Department of Zoology; National Museums of Kenya; P.O. Box 78420-00500 Nairobi Kenya