article_snippet: The findings challenge a key element of the evolutionary theory that was first proposed by Charles Darwin 156 years ago.
article_snippet: Male and female Choco Toucan's (pictured above) both share the same brightly coloured plumage, suggesting another force other than sexual selection is driving the evolution of bright colours in feathers of some birds .
article_snippet: Rather than the bright colours of male birds appearing because of sexual selection - where a trait evolves over time because it is seen as attractive or a signal of fitness by the opposite sex - other forces of natural selection are at work.
article_snippet: The researchers say that the environment a species lives in, how a species cares of a species young and migratory behaviour appear to influence a species plumage.
article_snippet: so this should hopefully get researchers to think more about how color affects survival, especially predation and foraging success, in both sexes.'
article_snippet: The debate over the differences in colour between species of birds has raged ever since the time of Darwin and Alfred Russel Wallace.
article_snippet: While Darwin based Darwin theory of sexual selection on the idea that brightly coloured males were preferred by females, giving brightly coloured males a competitive advantage, Alfred Russel Wallace pointed out that in many species females are as brilliantly coloured as the male.
article_snippet: Alfred Russel Wallace suggested instead that the differences between the sexes - known as sexual dichromatism - were the result of females needing better camouflage to prevent their nests from being raided by predators.
article_snippet: This would suggest that sexual preference for bright colours plays a more powerful role in determining the evolution of a species than other pressures.
article_snippet: By looking at where the birds sat in the phylogenetic tree, however, the birds were able to conclude that over evolutionary time the colour difference between species appears to have declined.
article_snippet: Overall, both natural and sexual selection have influenced the evolution of bird coloration, but in many respects, natural and sexual selection have acted on two different axes: sexual selection on an axis of sexual differences and natural selection on an axis of color (for example, dull or bright) in both sexes. '
article_snippet: Thus, debate about the causes of variation in bird coloration may be resolved by recognizing that natural and sexual selection have generally acted on two different axes.'
highlights_snippet: The findings challenge Charles Darwin's theory of sexual selection in birds .