LITTLE DINOSAURS AND EARLY BIRDS

. . . or how the one evolved from the other. Kaufmann talks about how scales gave way to feathers and how feathers help to regulate body temperature, and he reviews two theories on how birds began to fly. (One posits tree-dwelling ancestors, the other two-legged runners after insects.) With serviceable illustrations, this is a reasonable companion to last year's Flying Reptiles, though here Kaufmann's overall presentation of natural selection and his specific explanations--of ""cold blooded,"" for example--lack the other book's clarifying edge.