Members of the scientific community have marveled for years at the Australian bowerbird's elaborate courtship ritual, in which the male bowerbird builds an elaborate edifice of a twig canopy arching over an avenue (called a "gesso") of stones, bones, and shells in order to impress on a female bowerbird that he is dexterous and, therefore, a good lay. Female bowerbirds are attracted to the biggest structures containing the shiniest pebbles, — a fact that ornithologists seem to find hilarious — but research has revealed that males have employed an optical illusion in order to avoid the hard work of finding and arranging paving material for their avenues. Using a forced perspective trick that even medieval painters couldn't quite figure out, male bowerbirds arrange stones at the avenue's entrance from smallest to largest, thus making it appear more like a Champs-Elysees and less like a seedy alley in Perth (Perth, I'm sure, is a wonderful city).
In the January 20 issue of Science, Laura A. Kelley and John A. Endler of Deakin University in Australia explain that, since female bowerbirds prefer the grandest gessoes, they tend to choose males who've most successfully created the illusion of grandness. Based on the success of the male bowerbird's illusions, they further claim that
illusions may be widespread in other animals because males of most species display to females with characteristic orientation and distance, providing excellent conditions for illusions.
In Bowerbird Romance, Master Illusionists Get the Girls [Scientific American]
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