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Lipids with long conjugated carbon chains often absorb light in the visible spectrum, producing a variety of pigments and dyes.

Birds acquire the pigments that produce their characteristic colors the plant materials (or creatures that have ingested plant materials) that comprise their diet. Carotenoids give rise to pigments that produce bright red, orange, and yellow colors.

Why do male and female cardinals have differing colorations?


Male cardinals have a predilection for a specific type of plant material containing the carotenoids for their color, while females prefer a different diet with different carotenoids.


Males and females transport the same quantity of carotenoids to the follicles, but have differing concentrations of the enzymes that generate the pigments in their feather follicles. The extreme difference in concentration of pigment produced within each feather follicle is what gives rise to the variance in coloration.


Male and female cardinals eat the same diet, but have sex-dependent differences in intestinal uptake and processing of carotenoids to generate the pigments which are then deposited in the feathers.


Both sexes produce and transport the same amount of pigments, but females have enzymes in the feather follicles that degrade those pigments to remove most coloration from the females.

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