Why are the eggs of the marsh wren deep brown, the winter wren's nearly white, and the gray catbird's a brilliant blue? And what in the DNA of a penduline tit makes the male weave a domed nest of fibers and the female line it with feathers, while the bird-of-paradise male builds no nest at all, and his bower-bird counterpart constructs an elaborate dwelling? These are typical questions that Bernd Heinrich pursues in the engaging style we've come to...