Effects of diet on plumage coloration and carotenoid deposition in red and yellow domestic canaries (Serinus canaria)

Atlantic Canaries (Serinus canaria) are the most commonly kept caged bird with extensive carotenoid-based plumage coloration. Domestic strains of canaries have been bred for a variety of colors and patterns, making them a valuable model for studies of the genetic bases for feather pigmentation. However, no detailed account has been published on feather pigments of the various strains of this species, particularly in relation to dietary pigments available during molt. Moreover, in the twentieth century, aviculturists created a red canary by crossing Atlantic Canaries with Red Siskins (Carduelis cucullata). This "red-factor" canary is reputed to metabolically transform yellow dietary pigments into red ketocarotenoids, but such metabolic capacity has yet to be documented in controlled experiments. We fed molting yellow and red-factor canaries seed diets supplemented with either β-carotene, lutein/zeaxanthin, or β-cryptoxanthin/β-carotene and measured the coloration and carotenoid content of newly grown feathers. On all diets, yellow canaries grew yellow feathers and red canaries grew orange or red feathers. Yellow canaries deposited dietary pigments and metabolically derived canary xanthophylls into feathers. Red-factor canaries deposited the same plumage carotenoids as yellow canaries, but also deposited red ketocarotenoids. Red-factor canaries deposited higher total amounts of carotenoids than yellow canaries, but otherwise there was little effect of dietary supplementation on feather carotenoid content, hue, or chroma. These observations indicate that canaries can use a variety of dietary precursors to produce plumage coloration and that red canaries can metabolically convert yellow dietary carotenoids into red ketocarotenoids.