Parasitism, commensalism, symbiosis, and the origins of parasitism, with the effect on host and parasite, are discussed in a comprehensive manner in this book. The fleas, lice, protozoa, flies, and mites that associate themselves with birds are the ones the authors have found in England. The chapter on the fauna of birds' nests should interest any amateur naturalist. The final chapters are devoted to birds that are "parasites" on other birds for part of their existence, such as the cuckoo. The book is written for the amateur rather than for the professional parasitologist. An appendix, however, presents an extensive bibliography, together with an index of popular and scientific names.