True love for zebra finches

Zebra finches select their mates based on compatibility over quality.

Two Zebra Finches gaze at each other as love birds.  The birds are posed in a natural habitat background.

Homo sapiens is not the only species for which beauty is in the eye of the beholder. Zebra finches, too, are highly individualistic in what they find attractive in a mate, and new research suggests why.

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In most species, individuals compete for the highest-quality mates – those equipped with the best genes to pass on to their offspring, for example, or the best at provisioning young. Those of the highest quality are most in demand.
But zebra finches are different in that individuals vary wildly in their mate preferences.

“It seems that compatibility is much more important than quality,” said Wolfgang Forstmeier of Germany’s Max Planck Institute for Ornithology to BBC Wildlife. “Even the scruffiest, sickliest-looking birds are first choice for someone. There’s a different lid for every pot.”

Forstmeier’s team have now shown that when birds are allowed to choose their mates freely, they raise 37 per cent more chicks than pairs whose mates were selected for them by the biologists. In the arranged marriages, the partners are apparently unable to work well together to raise their brood.

“It seems like they are just not excited enough by the partners we give them,” Forstmeier explained. “The females lay more infertile eggs, after apparently not copulating enough. The males don’t seem to be stimulated enough to attend the nest well and look after the young.”

So why should zebra finches do things so differently from almost all other animals? In most species, said Forstmeier, idiosyncratic mate preferences are a disadvantage, because it inevitably reduces your options. But for zebra finches, that is unlikely to be a problem.

“In the wild, these birds live in very, very large flocks, so there is no shortage of choice. They can afford to keep searching until they find the right match,” Forstmeier continued. “It’s the same for humans. How do you say it? There are plenty more fish in the sea.” 

Source PLOS Biology

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Read more wildlife news in BBC Wildlife Magazine.