Why Are Male Birds More Colorful Than Female?

Male birds are often the more showy of the species.

Male birds are generally more genetically attractive then their female counterparts in regards to color and plumage, having distinctly more intricate and elaborate designs, a brighter and glossier sheen, and larger feathers. Charles Darwin had several theories to explain why nature selects for this in numerous animal species. Darwin's thinking has been built upon by further studies.

Sexual Advantage

In order to ensure reproduction, males develop more attractive features so they can more easily attract a mate. According to an article by Robert Heinsohn, professor of evolutionary biology at the Australian National University, published in the Sept. 12, 2005, edition of "Scientific American," female birds may see the degree of color in a male bird as a sign of his physical state and how well he can provide for them. For example, more nutritive seeds in a bird's diet enhance pigment color.

Territory

Colors can also be used to mark territory. Heinsohn's article cited red-winged blackbirds, which have a red spot they use to show other males to indicate a territory is taken and that they are willing to fight to preserve it. This spot is only shown to males of the same species and can be hidden so as to not attract predators.

Protection

Female birds while pregnant or nesting are more at risk for being attacked by predators. Darwin theorized that giving the females a more dull appearance allows them to blend in more easily with their surroundings. This allows them to lay eggs, and then raise the subsequent chicks, allowing for species growth.

Chemical Design

Adrianne Appel, in her article published in the Nov. 22, 2006, edition of "National Geographic News" remarked upon studies done in Spain which may prove that increased testosterone in male birds has a direct relation to the amount of carotenoids ingested. Carotenoids are the chemicals that enhance brightness and can be found in several berries and insects. The theory is that males eat more during mating season, thus indirectly increasing their testosterone and boosting their breeding chances.

Exceptions

In some bird species, the females are more colorful. Heinsohn listed such examples as button quail, phalaropes and sandpipers. With these species, the males take care of the eggs and chicks while the females guard them. The females also compete to mate with the males.

References

• "Scientific American", Why are male birds more colorful than female birds?; Robert Heinson; September 12, 2005
• "National Geographic News"; Testosterone gives male birds their color, scientists say; Adrianne Appel; Nov. 22, 2006