Fourth Edition. The Peterson Field Guide Series R Sponsored by the National Audubon Society, the National Wildlife Federation, and the Roger Tory Peterson Institute Americas Best-Selling Field Guides THE PETERSON IDENTIFICATION SYSTEM Roger Tory Petersons unique system shows exactly what features to look for to tell one species from another. EASE OF USE Peterson Field Guides are designed to work in the field, and every illustration, every word, is directed to that end. THE AUTHORS AND ILLUSTRATORS For each Field Guide, an author with expertise in the subject and an experienced artist work closely with the editors to ensure