Helpers at birds’ nests: a worldwide survey of cooperative breeding and related behavior.

In this expanded edition, Skutch describes the cooperative behaviour of more than fifty families of birds. Each family is introduced by a brief sketch of its distribution and outstanding features, followed by intimate, nontechnical accounts of the helpful behaviours that have been most carefully studied. Skutch considers the significance of helpful birds and discusses the theoretical aspects of cooperative breeding, its evolution, kin selection, altruism, and demography.