Male fairy-wrens are not always what they seem

In a new study from Monash University, experts have found that when it comes to brightly colored males, looks can be deceiving. The ornithologists report that the vibrant colors of superb fairy-wrens do not necessarily correlate with male quality. 

Among many animal species, the females prefer males with the most elaborate and dramatic appearance, and this preference drove the evolution of bright coloration. It is expected that brilliant colors are only acquired and maintained by “high quality” males with plenty of resources, sharp skills, or high social status. 

Females pursue high quality males to guarantee their offspring will have good genes and the greatest chance of survival. 

“We examined whether only the best quality males with excellent resources can produce the most vibrant colors and whether only the best quality males can maintain their colors in pristine condition,” said study lead author Dr. Alex McQueen. “We also tested this in an experiment, by administering testosterone to some males which caused them to produce breeding colors in winter.”

“Surprisingly, we found that all male superb fairy-wrens produced and maintained vibrant colors, regardless of their ‘natural quality’. Also the males that had to produce breeding colors in challenging winter conditions displayed vibrant colors that were indistinguishable from other males.”

Each year, male superb fairy-wrens transform their color by moulting from a brown plumage to an ultraviolet blue and black breeding plumage. The males flaunt their new feathers to impress females during elaborate sexual displays.

“We predicted that maintaining their colors would be especially important in this species for two reasons: first, males that are preferred by females produce their breeding plumage earlier than all other males, many months before the start of breeding, meaning that those early males display their breeding colours for the longest time each year; and second, ultraviolet blue feathers have been shown to readily fade over time in other birds,” said Dr. McQueen.

For the investigation, the researchers measured the colors of specific wild male fairy-wrens several times a year. The experts also recorded how much time males spent preening when they were in their brown non-breeding plumage and colorful breeding plumage.

“We were very surprised to find that male breeding colors do not fade with time,” said Dr. McQueen. “Despite keeping their colors in pristine condition, males did not spend more time preening while in breeding plumage.”

Instead, the males “retouched” their breeding colors by replacing a few blue feathers at a time throughout the breeding season.

“Our study shows that the vibrant breeding colors of male superb fairy-wrens are unlikely to signal male quality to females,” said Alex. “We also found that males are careful to keep their feather colors in excellent condition for sexual displays.”

The study is published in the journal Behavioural Ecology.

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By Chrissy Sexton, Earth.com Staff Writer