Keeping up appearances: male fairy-wrens show looks can be deceiving

December 22, 2020

In many animals, female preference for males with the most elaborate appearance is an important factor in the evolution of bright and dramatic colours.

Females are thought to prefer colourful males because only 'high-quality' males - those with the most resources, superior foraging skills or social status - can produce and maintain the most vibrant colours.

By choosing these high-quality males, females may ensure a good father or good genes for their offspring.

But do high quality males that are preferred by females invest more in their appearance?

A new study by Monash University ornithologists suggests, not necessarily.

Led by PhD graduate Dr Alex McQueen, from the Monash University School of Biological Sciences the study published in Behavioural Ecology examined whether conspicuous colours of superb fairy-wrens signal male quality.

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

"Surprisingly, we found that all male superb fairy-wrens produced and maintained vibrant colours, regardless of their 'natural quality'. Also the males that had to produce breeding colours in challenging winter conditions displayed vibrant colours that were indistinguishable from other males," she said.

Every year male superb fairy-wrens change colour by moulting from a brown non-breeding plumage to an ultraviolet blue and black breeding plumage.

While they are in their breeding plumage, males flaunt their colours to females by performing elaborate sexual displays.

"We predicted that maintaining their colours 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 Alex.

The research team measured the colours of the same, wild male fairy-wrens several times a year.

And they recorded how much time males spent preening when they were in their brown non-breeding plumage and colourful breeding plumage.

"We were very surprised to find that male breeding colours do not fade with time," said Alex.

"Despite keeping their colours in pristine condition, males did not spend more time preening while in breeding plumage," she said.

The research team found that instead males 'retouched' their breeding colours by replacing a few blue feathers at a time throughout the breeding season.

"Our study shows that the vibrant breeding colours 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 colours in excellent condition for sexual displays."

Monash University

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