Publication of A Field Guide to the Birds

Roger Tory Peterson's guide is widely credited as the first modern field guide, and the book that turned birdwatching from a specialist pursuit into a mass hobby. Its innovation was the Peterson Identification System: small arrows drawn onto the illustrations pointing at exactly the field marks, a stripe, a wingbar, a bill shape, that separate one species from a similar-looking other, so a reader in the field could identify a bird by silhouette and pattern alone rather than needing a specimen in hand. Houghton Mifflin's first printing of 2,000 copies sold out within a week. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/