Bird Physiology Affected by Feather Color

June 4, 2008 by  
Filed under Features

New research conduced by a team from the Arizona State University revealed with startling certainty that the color of a bird has a massive effect on its physiology. During the course of the experiment a number of male barn swallows had their breast feathers artificially colored to match those of more desirable males. The results showed that the change in color didn’t just affect the eligibility of the males in the females eyes, but it actually changed the birds own body chemistry.

Assistant Professor Kevin McGraw commented that it was always traditionally thought that the bird’s internal processes determined their external appearance. However, the new research indicates that when the birds perceived a change in their coloring it directly affected their internal physiological state. At a time in the breeding cycle when the bird’s sex steroids are usually declining, these birds showed a massive jump in testosterone levels after just one week. McGraw also noted that the speed at which these changes took place suggested that the tiny birds had a very dynamic system.

The change in plumage coloring also had other effects on the birds. The birds that had been purposely altered with a non-toxic marker were found to breed earlier in the season and to father more young. Their females also cheated less frequently. However, the increase in activity seems to have had a marked effect on the health of the bird too, as many of them not only had increased androgen levels but showed a marked decrease in weight. This seems to confirm that plumage conveys accurate and honest information about the health of the animal and that it is usually only the healthiest and fittest birds that develop the richer coloring. Darker feather colors are not only more biochemically costly to produce but they also make the bird more vulnerable to predators. Thus only the fittest birds with naturally higher levels of testosterone are naturally capable of producing this sort of plumage, making them more appealing to females and increasing their chances of successfully producing offspring.

The striking change in the hormone levels of the bird might make one think of how a good haircut or a new suit can make you feel a million times better about yourself and more appealing to the opposite sex. Clearly this is not just a phenomenon that occurs in humans and the research suggests that there is more to it than just ‘feeling good’.

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