Many field ornithologists record where and when they identify species of birds, especially when they encounter a species out of its normal range or for the first time. Until now, however, a checklist based on the Sibley-Ahlquist-Monroe classification has not been available. In this book, Burt L. Monroe, Jr., and Charles G. Sibley provide a list of 9,702 living avian species based on their 1990 book Distribution and Taxonomy of Birds of the World and its 1993 Supplement.