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Exaggerated tail feathers of birds constitute a standard example of evolution of extravagant characters due to sexual selection. Such secondary sexual traits are assumed to be costly to produce and maintain, and they usually are accompanied by morphological adaptations that tend to reduce their costs. The aerodynamic costs for male barn swallows Hirundo rustica of having long tails were quantified using aerodynamics theory applied to morphological data from seven European populations. Latitudinal differences in tail length were positively correlated with differences in flight costs predicted by aerodynamics theory. A positive relationship between aerodynamic costs of long tails and the degree of sexual size dimorphism was found among populations.

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A peacock's tail: how Darwin arrived at his theory of sexual selection

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Have peacock tails lost their sexual allure? | New Scientist

By Colin Barras. They judged tail quality in two ways — first by simply measuring tail length, and secondly by taking photos of each male during the tail-fanning display ritual and counting the number of eyespots. Next they examined whether females chose mates with the best-quality tails. Rather than consider what is unusual about their study, they conclude that peahens in general do not prefer males with elaborate trains. Takahashi argues that it is the failure to find a relationship that makes her study so important. She says this undermines the assumption that the train is a sexual signal. Trending Latest Video Free.
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Have peacock tails lost their sexual allure?

The plumage of the male bird represented a hole in his theory of evolution. Sexual selection was of strategic importance to Darwin, says Evelleen Richards, an honorary professor in history and philosophy of science at the University of Sydney: it was a naturalistic account for aesthetic differences between male and female animals of the same species, shoring up his defence of natural selection. In, On Darwin and the Making of Sexual Selection , published last month by the University of Chicago Press, Richards explores this confluence of connections Darwin had to make and, just as crucially, the challenges he had to overcome in order to reach his conclusion.
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Sexual Selection I t was Charles Darwin who originally proposed that the so-called secondary sexual characteristics of male animals -- such as the elaborate tails of peacocks, bright plumage or expandable throat sacs in many birds, large racks in mooses, deep voices in men -- evolved because females preferred to mate with individuals that had those features. Sexual selection can be thought of as two special kinds of natural selection, as described below. Natural selection occurs when some individuals out-reproduce others, and those that have more offspring differ genetically from those that have fewer. In one kind of sexual selection, members of one sex create a reproductive differential among themselves by competing for opportunities to mate.

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