Tuesday, 6 September 2016

Seminar by Prof John Endler on bird courting habits, Thur 12-1

The Cognitive Research Group is proud to host a seminar by Professor John Endler. Professor Endler is visiting from Deakin University, hosted by Dr. Andrea Griffin.

TITLE: Visual tricks and illusions used by great bower birds when courting females.

WHEN: Thursday September 8, 12-1pm.

WHERE: Psychology / Aviation Building, Keats Reading Room (AVLG17).


Bowerbird males build and decorate bowers which are used only for attracting mates and mating, and they steal from and destroy each others' bowers.  This and the fact that bird vision is fairly well understood gives an unparalleled opportunity for experimenting with various aspects of signalling in undisturbed wild birds. Using principles of bird colour vision physiology we can show that they choose coloured objects which significantly contrast with their own plumage, the bower and the visual backgrounds.  We can also show that the choice of colours is innovative; the idea of bowerbirds choosing colours which elaborate their own plumage is an artifact of biases in human vision. Great Bowerbird males make a 0.6m long bower avenue opening up to 1 m courts at each end. The courts are covered with gray and white objects and coloured objects are displayed on or over them.  The coloured objects are outside the female's field of view until he displays them and then tosses them outside her view again, further increasing colour contrast.  The courts consist of gray and white objects which increase in size with distance from the female within the bower avenue and this creates forced perspective which gives the illusion of a very regular pattern.  This pattern regularity could be a direct target of female choice but also generates further illusions with the coloured objects. The quality of the forced perspective illusion significantly predicts female mating preferences.  Bowerbirds also create illusory effects by painting the inside of the avenue, resulting in chromatic adaptation. Finally, they present colours and shapes as "now you see it now you don't", and also without repeating, which prevents other forms of sensory adaptation.  Given that almost all visual displays of almost all animals are presented from a predetermined direction and orientation relative to the receiver this raises the possibility that illusions may be used in communication in a wide variety of species.