Per Alström is Professor of Ornithology at Uppsala University’s Department of Ecology and Genetics and the Swedish University of Agricultural Sciences. A keen birder since his childhood in southwest Sweden, Per started travelling abroad at an early age, and he has spent many years in the field in some 20 countries in Asia, as well as multiple trips to North America and parts of Africa. He is the author of more than 100 scientific articles (including many on difficult-to-identify bird species), was the senior author of two highly acclaimed books, A Field Guide to the Rare Birds of Britain and Europe (1991) and Pipits and Wagtails of Europe, Asia and North America (2003), and co-author of chapters in two volumes of Handbook of the Birds of the World (2004, 2006). Per is Adviser to the IOC World Bird List, and Deputy Editor-in-Chief of the international ornithological journal Avian Research. Krister Mild was a freelance ornithologist and sound recordist for many years, but is now employed at the Department of Natural Resources, Swedish Environmental Protection Agency. He has published a large number of identification articles in different European birdwatching magazines and has produced cassettes and CDs of bird vocalisations from different parts of the Palearctic. He has travelled much, mainly in Europe and Western Asia, and is a member of the Swedish rarities committee. Bill Zetterström is an engineer from Sweden. He has been interested in birds most of his life and has travelled widely. He has been drawing since childhood, though he only took up painting birds in 1988. In 1989 he was voted 'Swedish bird painter of the year', and he has done some plates for a forthcoming handbook to the birds of the Indian subcontinent.