Identification Guide to North American Birds

Figure 138 from the Second Edition of Part 1: Absence (HY/SY) and presence (AHY/ASY) of "molt clines" to assist with ageing many passerines.
The Second Edition to Identification Guide to North American Birds, Part 1, is now out! An important change from the first (1997) edition is the presentation of revised and consistent molt and plumage terminology, including designations of preformative molts and formative plumages, along with 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 "molt clines" for ageing, e.g., as presented for passerines to the left. Information has been substantially revised through evaluation of digital images, comments received from hundreds of users since 1997, and the incorporation of over 1,295 additional scientific papers and on-line resources; see above for links to Literature Cited Section and Errata. Recognition of subspecies has been overhauled in an attempt to provide a consistent and practical taxonomy. We have learned a lot since 1997 and this revised edition reflects the progress we have all made!
Figure 555 from Part 2: Age criteria for Atlantic and Horned (inset) Puffins