Plumage

Abstract: FEMALE choice of mates based on the expression of characters that correlate with male quality remains a controversial and largely untested idea1. By choosing quality males, females stand to gain resources2, genetic benefits for their offspring3–5, or both. In the house finch (Carpodacus mexicanus), male plumage coloration is a function of dietary intake of carotenoids6,7. Here I present results of field studies that indicate that females prefer to mate with colourful males and that plumage brightness correlates with a male's capactity for parental care and perhaps its genotypic quality. Artificially brightened males paired more quickly and frequently than sham control or lightened males. Among unmanipulated males, plumage coloration was correlated with nest attentiveness and overwinter survival. In addition, there was a positive correlation between the coloration of fathers and sons.

Abstract: 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

Abstract: This work falls into two parts. The first section gives a short general summary of the plumage of birds, its structure, arrangement and functions and briefly reviews the various types of moult patterns which are found and the ways of recording them. The second part gives a systematic species-by-species account of points including the number of flight feathers, the sequence, season and rate of moult, its relationship to breeding and migration, and the extent of the post-juvenile moult. In addition, scatter diagrams of primary moult score plotted against date are given for some species.

Abstract: The hypothesis that ornaments can honestly signal quality only if their expression is condition-dependent has dominated the study of the evolution and function of colour traits. Much less interest has been devoted to the adaptive function of colour traits for which the expression is not, or is to a low extent, sensitive to body condition and the environment in which individuals live. The aim of the present paper is to review the current theoretical and empirical knowledge of the evolution, maintenance and adaptive function of colour plumage traits for which the expression is mainly under genetic control. The finding that in many bird species the inheritance of colour morphs follows the laws of Mendel indicates that genetic colour polymorphism is frequent. Polymorphism may have evolved or be maintained because each colour morph facilitates the exploitation of alternative ecological niches as suggested by the observation that individuals are not randomly distributed among habitats with respect to coloration. Consistent with the hypothesis that different colour morphs are linked to alternative strategies is the finding that in a majority of species polymorphism is associated with reproductive parameters, and behavioural, life-history and physiological traits. Experimental studies showed that such covariations can have a genetic basis. These observations suggest that colour polymorphism has an adaptive function. Aviary and field experiments demonstrated that colour polymorphism is used as a criterion in mate-choice decisions and dominance interactions confirming the claim that conspecifics assess each other's colour morphs. The factors favouring the evolution and maintenance of genetic variation in coloration are reviewed, but empirical data are virtually lacking to assess their importance. Although current theory predicts that only condition-dependent traits can signal quality, the present review shows that genetically inherited morphs can reveal the same qualities. The study of genetic colour polymorphism will provide important and original insights on the adaptive function of conspicuous traits.