Originally The Color of Sex.
Male house finches (Carpodacus mexicanus) have carotenoid-based ornamental plumage coloration. In previous research it was shown that for a single population of house finches in a single year, males that paired were on average redder in plumage coloration than males that did not pair, and males with redder plumage tended to nest earlier than males with less red plumage.
One of the most widespread ornamental traits among birds is carotenoid-based red, orange, and yellow plumage coloration. Carotenoid pigments cannot be synthesized de novo by birds or by any vertebrates; they must be ingested. Because carotenoid pigments must be derived from food, expression of carotenoid pigmentation is dependent on access to sufficient amounts of foods that provide the right type of carotenoid pigments. The physiological condition of a bird at the time of molt, independent of parasitic infection, has also been invoked as a factor in the efficiency with which ingested carotenoids might be used to pigment feathers.
Models of sexual selection predict that condition-dependent ornamental traits such as carotenoid-based plumage coloration should be of particular interest to females when they choose a mate.
In both laboratory and field experiments, female house finches have been shown to prefer mates with redder and more intensely pigmented plumage.
One result of female preference for redder males is that the mean redness of paired male house finches is greater than the mean redness of unpaired males, among male house finches that pair, redder males tend to initiate nesting earlier (i.e., their mates lay eggs earlier) than less red males.
Rybird deductive corollary, Good food and hygiene offers better choices of a mate, thus better sex. We already knew that, but they had to prove it.
Previous condensed from: http://beheco.oxfordjournals.org/content/10/1/48.full
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