Science/AAAS; (inset) J. J. Harrison/Creative Commons

ScienceShot: Bird Masters of Illusion

It takes some trickery for a male great bowerbird (Ptilonorhynchus nuchalis) to hold a female's attention. He spends a majority of his time building and performing upkeep on an intricate structure called a bower to attract members of the opposite sex. Two stick walls arch over the east and west sides of the bower, and a courtyard filled with trinkets—such as rocks, sticks, shells, and bones—stretches from south to north. Last year, researchers discovered that the male organizes these trinkets, or "gesso," so that the largest ones lie farthest from where the female stands. From the female bowerbird's perspective, the objects all appear to be the same size, an illusion called forced perspective by filmmakers and photographers. Now, researchers who recorded the scene at the bowers of 20 males in northern Australia have shown that the better the gesso objects are arranged in this way, the better a male's chances of mating with a female. The illusion may hold the female's attention for longer than a poorly arranged gesso, the researchers suggest online today in Science, giving the male time to mate with her. Or the pattern may hint that the male has other qualities the female is looking for in a mate.

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