you are in a movie theater watching an action film. Your
head is fixed on the screen. How do you follow the
action from one side of the screen to the other? Usually
by moving your eyes. Actually, we humans have a high
degree of eye movements that allows us to track objects
and communicate signals to other human beings. Although,
the degree of eye movement differs between bird species,
it is overall more constrained than in humans.
birds solve the problem of tracking objects with eyes
placed peripherally and limited eye movements? The
solution to this evolutionary riddle is simple: moving
moving the head, birds can focus on two images at the
same time (one per eye, as eyes are placed
peripherally). However, to keep track of what is going
on around its head, birds move their heads very
quickly. How quickly?
Have a look at this
Quick Time®). Even better: try to
count the number of all head-movements
this bird exhibits while pecking at seeds. The video
lasts 1 min and 23 seconds, so you can calculate the rate of head
movement per min.
video again, but
now focus on
how the bird moves its head right before going head-down.
As you will see, one of its eyes focuses on the seeds on the
ground by placing the head in a 90°
angle in relation to the
many things to study about head movements, as we do not
know how they vary in species with different
configuration of visual fields. Our research will
address between-species variation in head movements.
Foraging and visual fields