In a test three years ago, using a $5.99 marker, scientists darkened the rust-colored breast feathers of male New Jersey barn swallows, turning lighter birds to the level of those naturally darkest. They found that the marked-up males were more attractive to females and mated more often.Scientists recently repeated the test and this time they found out that the more attractive appearance, at least in the bird world, triggered changes to the animals' body chemistry, increasing testosterone."Other females might be looking at them as being a little more sexy, and the birds might be feeling better about themselves in response to that," said study co-author Kevin McGraw, an evolutionary biology professor at Arizona State University.McGraw said the findings are surprising, in part because the hormonal changes occurred after only one week.In the 30 male barn swallows who were darkened, testosterone was up 36 percent after one week, during a time of year when levels of that hormone would normally drop.Source: Discovery News
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