In this book, the first New Naturalist Monograph on a species of bird, Dr. Stuart Smith, author of How to Study Birds, has concentrated the result of years of observation and research on the Yellow Wagtail. Dr. Smith writes from his own experience of practical field-studies, his continual hobby and spare-time occupation. Most field-workers have their "own" bird, or birds, and Stuart Smith's favourite is Motacilla flava flavissima, the Yellow Wagtail of the British Isles, a subspecies, practically confined to these islands, of a species which is widely distributed in the Old World. The British Yellow Wagtail in particular, and the Yellow Wagtail species in general, have been deserving of study and monography for many years. Dr. Smith's middle chapters, on territory, display and reproduction, are based on many hours of careful observation in the field, and much careful deduction therefrom. His other chapters give us a statement of the complex systematics and distribution of the species - a statement which was badly needed - for the flava wagtails are in an unstable state from the evolutionary point of view. There is no doubt that this monograph, with its very beautiful and accurate paintings by Edward Bradbury, will be not only invaluable to biologists in their study of the future evolution of the species, but will appeal to ornithologists and amateurs alike by the lively and pleasant quality of the writing, the interesting and extremely informative presentation of the subject, and the learned bibliography.