Birds of colorful feather competing together: New Zealand-led study

Colorful plumage in birds isn't always for the boys and might have little to do with attracting a mate, according to a New Zealand-led study out Thursday.

The study, which involved researchers from Australia, Canada and Germany, found that social and lifestyle factors could explain the bright feathers on some birds, said Massey University scientists.

The findings challenge the orthodox explanation for the bright coloring of the males of some species and the duller appearance of the females, which was the sexual selection theory that predicted males benefited in competing to attract females and produce more offspring.

The scientists analyzed the coloration of almost 6,000 species of passerine birds, commonly known as "songbirds", that include more than half of all bird species.

They first developed a new way of measuring colorfulness that indicated how "male-like" or "female-like" the plumage was in each sex of each species.

This allowed them to measure whether males were more colorful than females, whether both males and females were drably colored, or whether both males and females were colorful.

They found that in areas where females had to compete for resources or mates, or help defend their territory, they were also brightly colored, but when environmental or social pressures on females were relaxed, they lost their bright coloration.

The key evolutionary pattern was for coloration to decrease in females when it was not needed-the opposite pattern to what was previously thought.

"A shortfall of the classical sexual selection theory is that it works so well at explaining colorful plumage in males that the rest of the variation is often forgotten about. Our research demonstrates that bright female plumage is also functional and very important," lead author Associate Professor James Dale said in a statement.

"This is also the first study to clearly show that tropical species are more colorful than birds from other regions on earth. This does beg the question about what exactly it is about the tropics that favors more colorful plumage. We suspect that competition is fiercer in tropical environments, but more research is needed." Endit