Volume 4 of the acclaimed Handbook of the Birds of the World series covers some of the most vibrant and diverse non-passerine bird families across four orders, presenting a global perspective on avian richness. This volume features 837 species—making it the most species-rich non-passerine volume in the series—including sandgrouse, pigeons and doves, cockatoos, parrots, turacos, and cuckoos. A foreword by Jürgen H. Haffer introduces key discussions on species concepts and taxonomy in ornithology, setting the stage for the depth of detail that follows. Major families such as Columbidae (pigeons and doves, 309 species), Psittacidae (parrots, 322 species), and Cuculidae (cuckoos, 136 species) are treated in full, alongside Pteroclidae (sandgrouse), Cacatuidae cockatoos), and Musophagidae (turacos). These groups are found across all continents, and many include species of critical conservation concern. Highlights include 70 colour plates, 236 vivid photographs, 837 detailed distribution maps, and nearly 7,000 bibliographical references. Species accounts provide in-depth information on appearance, habitat, behaviour, feeding, breeding, movements, and conservation. The volume also examines key taxonomic questions—such as separating cockatoos as their own family—and addresses nomenclature issues, especially within fig-parrots and other complex groups. Lavishly illustrated and scientifically thorough, this volume is an indispensable reference for ornithologists, birders, researchers, and conservationists interested in the global diversity and status of these iconic bird families.El Volumen 4 de la aclamada serie Handbook of the Birds of the World abarca algunas de las familias de aves no paseriformes más vibrantes y diversas, distribuidas en cuatro órdenes, y ofrece una perspectiva global sobre la riqueza aviar.