A Red Bird in a Brown Bag

Abstract

The House Finch is among the most mundane birds, so ubiquitous and familiar across the U.S. and Canada that it does not rate a glance from most bird enthusiasts. But males have carotenoid-based plumage coloration that varies markedly among individuals, making the House Finch a model species for studies of the function and evolution of colorful plumage. In more depth and detail than has been attempted for any species of bird, this book takes a tour of the hows and whys of ornamental plumage coloration. The book begins by reviewing the history of the study of colorful plumage, which began in earnest with the debates of Darwin and Wallace but which was largely forgotten by the middle of the 20th century. Documenting the extensive plumage variation among males both within and between populations of House Finches, the book explores the mechanisms behind plumage variation and looks at the fitness consequences of condition-dependent ornament display for both males and females. The book concludes by examining the processes by which carotenoid-based ornamental coloration may have evolved.

Phenotypic plasticity, sexual selection and the evolution of colour patterns

“…Carotenoidfree diets result in very little colour in normally pigmented species, such as the house finch, Carpodacus mexicanus (reviewed by Hill, 1994a;Hill, 2002;Hudon, 1994) and great tit Parus major (see Figs·2, 3). Canaries are fed cayenne pepper and other additives to improve their feather colouration (Vriends, 1992).…”

“…A final example of genetic evolution comes from Hill's work on the size of the red breast patch of the male house finch (Hill, 1993;Hill, 1994b;Hill, 2002). Subspecies from Mexico and Michigan have similar patch colours, but the Mexican subspecies has a smaller patch (Fig.·4).…”

“…Subspecies from Mexico and Michigan have similar patch colours, but the Mexican subspecies has a smaller patch (Fig.·4). Using morphological and biogeographical evidence, Hill estimated phylogenetic relationships among the subspecies (Hill, 1994b;Hill, 2002), and concluded that the Mexican subspecies was the derived one (however, the direction of evolution is not critical for the argument). Hill found that carotenoid manipulated diets prior to moult affected patch colour of both subspecies, but the size of the patches was not affected (Fig.·2) (Hill, 1993;Hill, 1994b).…”

“…Hill brings several lines of circumstantial evidence that this is indeed the case [ (Hill, 2002), chapter 11], including the finding of lower carotenoid concentrations in the diet of the Mexican population, as determined from gut contents.…”

Decreased hydrophobicity of iridescent feathers: a potential cost of shiny plumage

“…handicap) to the male (Andersson, 1994;Zahavi, 1975). Although studies have shown physiological, maintenance or viability costs for red, pigment-based colours (Hill, 2002;Olson and Owens, 1998), few have identified such costs in iridescent feather colours (Hill et al, 2005;McGraw et al, 2002). Further, to understand both the evolutionary trajectories of iridescent traits and whether signal honesty plays a role in the evolution of iridescent plumage coloration, it is necessary to determine the costs and limits of such traits .…”