An Approach to the Study of Molts and Plumages

During the course of studies of the molts and plumages of certain waterfowl and other birds, it has become apparent to us, as it has to a number of other workers, that the description of plumage successions has often been hampered by the lack of a uniform and practical terminology. It was our original intent to introduce a new terminology applicable, as far as possible, to all birds, in order to eliminate some of the semantic difficulties of the past. As this project progressed, it became obvious that knowledge of the plumage stages of many species is sadly incomplete or poorly understood; further study revealed the need of a reexamination of many long-held concepts of plumage succession and of more precise definitions of widely but ambiguously used terms. The subject is too large to be covered in a single paper. We propose here to discuss plumage succession beginning at the time of loss of the juvenal plumage, i.e., the bird's first covering of true (in some cases modified) contour feathers. We hope in a later paper to analyze the development of the plumages from the embryo through the completed juvenal plumage. We have adopted this reversed chronological sequence because of the complexity of the question of the natal downs and their origin, which we intend to investigate at some length. We hope in this paper to throw new light on concepts of plumage and molt, and we present a framework within which descriptive and comparative studies may be made. In spite of the vast progress made by many workers in recent decades in understanding some of the factors which affect the physiology of molt (genetic control, hormonal balance, photoperiod, temperature, diet, etc.), it must be remembered that such information is available for but a small fraction of the species of birds of the world. We believe it is greatly desirable to have