Male bowerbirds use their intelligence to impress the females, constructing elaborate structures called bowers to attract mates. They are not only master builders, but also accomplished artists. Males of some species decorate their bowers lavishly with flower petals and sparkly manmade objects. The Satin bowerbird even paints the walls of his bower with charcoal or chewed up berries. Male Great bowerbirds are even more remarkable. Their bowers, which are among the most complex of all, are true marvels of avian architecture. But as well as being builders and artists, males of this species are also magicians – the bowers they build are like a house of illusions, with built-in visual tricks that manipulate females' perceptions and increase their likelihood of choosing the builder as their mate. Bowerbirds are a family of twenty species that are native to Australia and New Guinea that are renowned for their unusually complex mating behaviour. The Great bowerbird of northern Australia is the largest species in the family. Males sport brownish-grey plumage build bowers, and spend many months building their bowers. The bowers consist of a thatched twig tunnel forming an avenue of approximately half a metre in length, opening out onto a court whose floor is covered with bones, shells and stones. When a potential mate steps into the avenue, the male stands in the court just by the avenue's exit, displaying to her the colourful objects he has collected, one after the other. Two years ago, John Endler of Deakin University and his colleagues reported that the males use visual illusions when constructing their bowers. They do so by arranging the objects covering the floor of the court in a particular way, so that they increase in size as the distance from the bower increases. This positive size-distance gradient creates a forced perspective which results in false perceptions of the geometry of the bower, which is visible only to the female when she is standing in the avenue. From her point of view, all of the objects in the court appear to be the same size. Consequently, she may perceive the court as being smaller than it actually is, and the male to be bigger.
Saturday, January 28, 2012
Bowerbird builds a house of illusions to improve his chances of mating
Neurophilosophy for a while now. His blog has recently been picked up by The Guardian, so congratulations to him. As a visual artist interested in why people began making art in the first place, his recent post struck a chord with me. Check out the entire post here. But here is a bait to attract your attention: