Lots of birds bob their heads while walking. In fact, head bobbing is a unique feature in birds and occurs in at least eight of the 27 families of birds.
There are a few theories why some birds bob their heads when they walk. That it assists with balance, it provides depth perception, and lastly, it sharpens their vision.
However, most studies suggest that birds in motion bob their heads to stabilize their visual surroundings. In comparison, we rely more on our eye movements, not our head movements, to catch and hold images while in motion.
Research shows that the head bob has two phases: hold and thrust.
For the hold phase, the body moves forward as the bird walks, but the head stays still, creating the illusion that the head is moving backward.
In the thrust phase, the head moves forward faster than the body, so the head gets thrust out in front.
There are two reasons a bird might do this. One: it might help the bird walk. When birds hop, they hunch down, then launch their heads (and the rest of themselves) forward.
This isn’t all that different from the head bob, so it could be that the thrust step gives them extra forward motion while walking.
The second possibility: head bobbing lets birds see better.
Seeing while moving is tricky – if your eye moves too fast, the image is blurry; and even if the image is sharp, it’s hard to judge the motion of things you see if you’re moving too.
This is why birds keep their heads still if you move them.
Head bobbing lets the head stay still for a moment (hold), then move quickly (thrust) to the next hold point.
If they didn’t head bob, their heads would be moving more or less constantly, which would make vision harder.
It turns out that not only is vision the primary reason for head bobbing, but birds actually adjust their walking in order to accommodate their head bobbing, and achieve the best vision.
So, that head bobbing pigeon you see walking round town? He’s doing it to keep an eye on you!