In no other group of perching birds has evolution produced such a degree of variation as in the 120 species of crows and jays that inhabit the world today. They range from the tiny Hume's Ground-jay of the steppe-highlands of Tibet to the huge Thick-billed Raven of the mountains of Ethiopia. Some are exceedingly beautiful in color, grace, and form; others are sinister in appearance. Some appear in tales of mythology and superstition; others are merely regarded as agricultural pests. The great majority, however, remain largely unknown, coming into contact with humans mainly when their...