Males of the large capulinero , a typical Australian bird, find mates by decorating their courtship sites in a way that creates an optical illusion , according to a study published in the journal Science . To court females, these birds gather a collection of gray bones, shells, stones and other objects and spend hours arranging the pieces in front of a kind of corridor made up of two walls and a densely woven straw floor. The male places the larger objects further from the entrance to the avenue and the smaller ones closer. Since objects normally appear smaller with distance, it creates the perception that the objects are all roughly the same size. When the female "peeks" through this tunnel, she experiences an optical illusion known as "forced perspective ."
In the new study, Laura Kelley and John Endler show that females of this species tend to choose males whose constructions produce the best versions of this illusion . It is not yet clear why the illusion is linked to mating success, but one possibility is that when the decoration appears more uniform, the brightly colored objects displayed by the male better capture the attention of the female. It is also possible that this spatial arrangement makes the hallway look smaller and the male proportionally larger.
