Researchers from the University of Wisconsin - Milwaukee have found that the evolution of the color of the plumage of birds depends less on the gender and more on predation and success of foraging.
Male birds tend to have feathers that are brighter and more colorful to attract female birds as mates, with experts suggesting that evolution has made the male birds more colorful to maintain this trait. However, the findings of the research team are the opposite.
The researchers, namely Peter Dunn and Linda Whittingham, biological science professors at UW-Milwaukee, along with Jessica Armenta, a graduate student, tested their hypothesis which states that evolution has instead caused male birds and female birds to have more similarities, as opposed to more differences such as in the color of their plumage.
The team studies 977 bird species, finding that male counterparts indeed have feathers that are brighter in color. However, the findings also revealed that the markings of male and female birds have become less different over time, as the animals attempt to blend in with their surroundings to hide themselves from predators.
The research found that natural selection, which includes factors relating to migration, breeding in certain subtropical locations and taking care of their young, is as strong as sexual selection in the evolution of the color of a bird's plumage/
"Although most studies of bird plumage focus on dichromatism, evolutionary change has most often led to similar, rather than different, plumage in males and females," the researchers wrote in their study, adding that it is behavior and ecology that is the main driving force behind the plumage color of both male and female birds and not their sexes.
It took Armenta four years to gather and analyze data of the 977 bird species involved in the study, across a total of six museums in the U.S. and Australia. Armenta studied three male birds and three female birds for each specie.
Whittingham and Dunn ran an analysis on the data that Armenta collected, assigning a color score to each bird based on the hue and brightness of its plumage. The colors were also examined according to 10 measures of natural and sexual selection.
The researchers found that, for the instances where birds in both genders are more similar in the color their plumage, it was due to natural selection. For species where there is an increased difference in plumage color between genders, it was due to sexual selection.
Dunn said that their research would hopefully make researchers think more on how the plumage color of birds affect their survival across both sexes.
Photo: Steve Wilson | Flickr
