This is the second edition of the Identification Guide to North American Birds, Part 1. An important change from the first (1997) edition is the presentation of revised and consistent moult and plumage terminology, including designations of preformative moults and formative plumages, along with the inclusion of "WRP" age and plumage codes (in addition to BBL age codes) that reflect this terminology. Terminology is now consistent for all North American birds treated in Parts 1 and 2.
Other changes include the addition of 21 new species accounts including those among four new families (New World Parrots, Old World Parrots, Bulbuls, and Munias), presentation of measurements in tables for greater ease of comparison, and inclusion of exposed culmen, tarsus, and mass values for each species and sex, and for many subspecies. Fifteen new figures have been added, many of which emphasize "moult clines" for ageing, e.g., as presented for passerines to the left.
Information has been substantially revised through the evaluation of digital images, comments received from hundreds of users since 1997, and the incorporation of over 1,295 additional scientific papers and online resources. The recognition of subspecies has been overhauled in an attempt to provide a consistent and practical taxonomy. The authors have learned a lot since 1997 and this revised edition reflects this progress.
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