Terns are elegant sea and marshland birds that live throughout the world. In Europe and North America a total of twenty-three species is represented, all of which are dealt with in this book. The variations among the species and their subspecies is great, and identification is therefore often highly problematic. Terns are long-distance migrants and can be seen regularly on passage between their normal breeding and wintering areas.Klaus Malling Olsen devotes much attention to the immature and winter plumages of these birds, which are generally inadequately described in most other field guides, while he also deals in depth with the problems of moult, species, and subspecies. The text covers the bird in the field, moult, and the bird in the hand. The author concludes each species account with extensive data on measurements and weight and an itemized key to identification. The text is accompanied by over forty color plates, which have been specially prepared for this guide by the talented Swedish bird artist Hans Larsson. The book is completed with a forty-eight-page representative photographic section.