The oceanographic and coastal features of the British Isles provide a wealth of ideal habitats for breeding seabirds and it is no surprise that the British and Irish seabird populations are of international importance, both in sheer numbers and in species diversity. Indeed, for some species British waters are host to the greater part of the world's population. This book presents the most up-to-date information available on these seabird populations, their numbers and distribution, and their changing fortunes in recent years. The Operation Seafarer survey, carried out in 1969-70, provided a baseline for future work that led to the establishment of the Seabird Colony Register by the Seabird Group and the Nature Conservancy Council. The results and analysis of their counts during 1985-87 form the basis for this book. Improved census methodology and a new computerised database has set *the standards for seabird monitoring in future decades. In Part 1 the general biology and population trends of British seabirds are described to set the scene for Part 2, in which the results and analysis for each of the 24 breeding species are given in detail. Full descriptions of the counting methods and the estimating factors used provide guidelines for future surveys not only in Britain, but wherever seabirds are of interest and importance. No-one with an interest in seabirds or conservation can afford to be without this authoritative book, nor but be grateful to the small army of professionals and amateurs who have so ably explored our coastal habitats. Illustrated by Keith Brockie