Among birds, shorebirds provide some of the more unique opportunities to examine basic problems in behavior, ecology, and evolution. This is in large measure due to the diversity, both behaviorally and ecologically, of a group closely related taxonomically and distributed throughout the world. The overall aim of these two volumes is to provide a representative selection of current research being conducted on shorebird behavior and ecology. Traditionally, marine birds have included those species that breed in large colonies on offshore islands along coasts (see Volume 4 of this series). Although shorebirds have generally not been considered within this group, the fact that almost 40% of the species breed along coasts and more than 60% often or always spend the nonbreeding season in coastal habitats more than justifies their inclusion as marine birds (at least those species that totally or partially depend upon the marine environment). Their inclusion markedly increases species diversity in marine birds since shorebirds add about 217 species to the 280 that are traditionally thought of as marine.