The evolutionary, ecological and behavioral questions posed by obligate brood parasites are among the most intriguing of all contemporary ornithological topics. Avian brood parasites lay their eggs in the nests of other birds and may be a major contributing factor driving several species of songbirds to near extinction. As one of the first books to present a comprehensive overview of this fascinating phenomenon, this work discusses the comparative biology and co-evolutionary adaptations exhibited by the five families of birds that engage in such behavior. Several chapters dealing with the comparative biology of both intraspecific and interspecific brood parasites, are followed by individual accounts of all known species--nearly 100 altogether, primarily cowbirds and cuckoos. Some of the more remarkable behavioral and structural adaptations of these birds include egg mimicry, juvenile mimicry, elimination by starvation or actual attack of other nestlings or host eggs, and even the learning and partial mimicry of host song traits. An extended glossary, a list of Latin names, 400 literature citations and range maps of all parasitic species discussed are also included. Detailed line drawings by the author enhance this synthesis of biological and ecological information.