Why do pigeons bob their heads when they walk?

Most evidence suggests that the head bobbing serves a visual function.

See video: http://in.youtube.com/watch?v=NHtrsbw3K0g

This has always been an intriguing phenomenon. Pigeons (or ‘Rock Pigeons’ to be exact) have a peculiar habit of bobbing their heads up and down when they walk. This leads to a common misconception – that the legs of a pigeon are somehow connected to their heads. When they walk, they move their heads up and down; when they stand still, there is no movement!

Birds have eyes on either side of their head, so don't have stereoscopic vision. In order to see depth, they take snapshots with the same eye from two points, and their mind makes the depth calculation.

In order to shed more light on this conundrum, one must first understand the basics of ‘bird vision’. From Ornithology (the science of birds), it can be inferred that as the pigeon’s eyes are on the side of its head – allowing a greater range of vision to stay vigilant against predators from all directions – they also disable the pigeon from its sense of depth. Pigeons cannot establish distances easily. Luckily we humans have eyes on the front of our heads, giving us depth perception.

For the pigeon to compensate this shortcoming, the bird moves its head, deciding on differences in apparent motion from nearby and/or distant objects. Closer objects move faster, distant objects move slower.

Now when rock pigeons stop in one place, there is no requirement for depth perception, hence the cessation of the head bobbing. But once they start foraging for food again, the need for depth kicks in and they start moving their heads up and down – giving the illusion that their heads are somehow connected to their feet!

To illustrate this concept, here is a common example: In the past, you may have tried to shoo away a pigeon in an outdoor picnic area. When a hand is wafted towards the pigeon, it turns sharply head first – in a desperate attempt to ascertain the depth of the attack – before attempting to fly/walk away. It all happens very quickly, but look out for it next time!

Chickens bob their heads while walking. So do cranes, magpies and quails. In fact, head bobbing is a unique feature in birds and occurs in at least 8 of the 27 families of birds.

There are a few theories why some birds bob their heads when they walk:
1. Assists with balance
2. Provides depth perception
3. 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.

Picture a pigeon on a moving treadmill. What do you think would happen as the pigeon walks with the speed of the treadmill and its environment remains relatively the same? Dr. Barrie J Frost (1978) did this experiment and the pigeon’s head did not bob.

Dr. Mark Friedman (1975) also conducted a series of experiments to test the head bobbing actions of birds, using doves. His research demonstrated that the head movement is controlled more by visual stimulation than movement of the body.

Scientists continue to research head bobbing in birds. For example, scientists are currently investigating question such as “Why do some birds exhibit head bobbing, while other do not?” For more information on this topic see the related Web sites section.