Pigeons Lock Eyes Forward During Flight, First In-Air Tracking Shows

Scientists fitted common pigeons with a lightweight rig of mirrors and cameras plus a backpack containing a control board and battery to record eye movements during flight. Six pigeons flew between perches 20 metres apart indoors, and three pigeons flew about 25 metres outdoors to return to a coop. After takeoff the pigeons increased pupil size and adopted a fixed eye position in their heads.

The eyes rotated forward on average, and whenever the head moved the eyes moved in synchrony with it. The fixed position aligns with the primary horizontal axis of the birds’ vision and their vestibular system. Ivo Ros at the California Institute of Technology said the alignment may help pigeons distinguish their own motion from external motion such as moving branches or predators.

Pigeons can move their eyes independently with a maximum amplitude of about 15 degrees, according to Graham Martin at the University of Birmingham. During the recorded flights, however, eye movements measured less than 1 degree. Eye movements normally give pigeons a horizontal field of view of about 340 degrees.

Ros noted that locking the eyes forward is likely to reduce that field and create a larger blind spot behind the bird. All test flights occurred when the birds were low to the ground. Ros said the pattern might differ at higher altitudes where fewer objects rush past, and he wondered how eye position would change during flock flight.

Martin suggested other birds, including predators such as peregrine falcons, may also stabilize eye position during curved pursuit paths. 064.