Dept. Chairman and Curator of Birds at the American Museum of Natural History, co-author with Dr. Robert Cushman Murphy of Land Birds of America, and a leading U.S. ornithological scholar, Dean Am-don writes here in specific and somewhat technical terms of the distribution of birds over the globe. He discusses physical barriers to mobility, the place of the ecological niche, the effect of predators, parasites, climate, man. Dominant species possess a broad ecological tolerance. He considers species dynamics (when species meet) and distribution, then the distribution of higher systematic categories, taking the crow family as his case of cosmopolitanism. His interest tends to become increasingly specialized as he proceeds and may leave the general reader lagging behind. An American Museum Science Book published by the Natural History Press.