How does birds avoid collisions with objects and each other?

Optic Flow Cues Guide Flight in Birds

Partha S. Bhagavatula, Charles Claudianos,Michael R. Ibbotson and Mandyam V. Srinivasan

Current Biology, 27 October 2011

The moment-to-moment challenges of rapid flight of birds through cluttered environments have always fascinated people. Australian scientists have unraveled the mystery surrounding how birds avoid collisions with objects and each other.

The researchers say the birds do this by using cues derived from the image motion that is generated in the eyes during flight.

The scientists investigated the ability of budgerigars to fly through narrow passages in a collision-free manner, by filming their trajectories during flight in a corridor where the walls are decorated with various visual patterns.

The researchers sums up like this “The results demonstrated unequivocally and for the first time, that birds negotiate narrow gaps safely by balancing the speeds of image motion that are experienced by the two eyes and that the speed of flight is regulated by monitoring the speed of image motion that is experienced by the two eyes.”