Page last updated at 06:53 GMT, Thursday, 8 October 2009 07:53 UK

Lowly females pick mediocre mates

By Victoria Gill
Science reporter, BBC News

Zebra finch pair (R.F. Lachlan)
The females seem to know what "quality category" they are in

Low-quality females prefer low-quality males, at least in the avian world.

This is according to research published in the Royal Society journal Proceedings B, testing female zebra finches' taste in males.

As adults, the low-quality females showed a preference for the songs of males of the same quality, and for the male birds themselves.

Evolutionary biologists previously thought that females would always opt for the best male available.

The study was led by Marie-Jeanne Holveck from the Centre of Functional and Evolutionary Ecology in Montpellier, France.

She explained that low- and high-quality birds differ in almost every important characteristic, including metabolism, longevity and attractiveness.

The two individuals just accept each other faster - they just go for it
Marie-Jeanne Holveck

Her team was able to breed high-quality and low-quality finches simply by changing the size of the brood in which the birds were raised.

In larger broods there is more competition between the chicks, she told BBC News, "so the larger groups produce lower quality chicks".

Dr Holveck's team tested the female chicks' preferences for males.

"We trained in what we call an operant cage. They were trained to peck two keys, and each time they pecked a key it played a male's song," she told BBC News.

One of the keys played the song of a high-quality male and the other played a low-quality male's song.

"I think this is a powerful test, because it's the female telling us what she would like to hear," said Dr Holveck.

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This low-quality female repeatedly returns to peck the button on the right, which plays the song of low-quality male finch.

The low-quality females repeatedly pecked the key that played a low-quality male's song.

Only male finches sing, and the song is an important reproductive signal to the females.

In the second part of her experiment, Dr Holveck found that these song preferences "actually translated into preferences for the live males".

"And quality-matched pairs," she explained, "bred faster - producing eggs faster than the mismatched pairs.

"The main reason, we think, could be that the two individuals just accept each other faster - they just go for it.

"The really amazing thing is that the females are able to recognise what 'category' they are in. We'd like to investigate further to find out how they do this."

Joseph Tobias, a zoologist from Oxford University who was not involved in this study, said the findings were interesting.

"While [this] doesn't overturn evolutionary thinking, it does reveal some interesting trade-offs in breeding decisions," he said.

"It also raises the intriguing possibility that the environment in which individuals are reared strongly influences their mating preferences as adults."



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