In fact, when chickens and pigeons move their heads, like us humans, their viewing angle doesn’t stay constant. So when they shake their heads, they can’t fix their eyes. This head-nodding can be seen in 8 of 27 bird families, including quails and cranes.
Even if people go back and forth when they want to see something, their eye muscles will make a movement called the vestibulo-ocular reflex. This movement adjusts our focus when we try to see something. Well, if chickens and pigeons are different from us, and if they bounce their heads, their viewing angles don’t stay the same, then why do they keep shaking their heads?
Where pigeons and chickens walk with their heads bouncing is their focal point.
In other words, these animals are trying to go in the direction they want to see by making their heads like this. In this way, they cannot see places that are out of their field of vision. This is exactly the reason for the movement.
The real reason behind this move:
The reason behind this move, which makes some of us smile as we look at it; It was detected in 1978 by researchers at Queen’s University in Canada, through an experiment called the treadmill. After this experiment, it was revealed that the pigeons did not actually shake their heads, but simply tried to lead them forward.
The head movement of these creatures consists of two stages; push and hold. During pushing from these movements, the heads of the animals go 5 cm forward. Then the holding motion begins and the head remains stationary. As such, the head seems to move backwards relative to the forward body.
For example, a pigeon can push and hold 5 to 8 times per second, which is a bit too fast for us humans’ eyes. The idea that these animals shake their heads is thus an illusion.
This movement is actually a physiological necessity for these creatures to perform the act of seeing.
For example, if the heads of these animals remain stationary only during the holding phase, this will cause them to have blurred vision. That’s why they need to balance pushing and holding. Chickens and pigeons wouldn’t be able to see clearly if they were shaking their heads constantly. Ultimately, these cute friends of ours don’t actually shake their heads, it seems like they are shaking us because of this movement.
In fact, it’s not just these animals that make this head-nodding motion. We humans can too. How Does? When moving in space, humans quickly move their eyeballs, not their heads, to correct their vision. That is, people’s eyes do not move continuously and smoothly, they jump from one point to another. If this is the name of the movement, it is saccade.
When the eye comes to the end of a saccade, it stops for a short time and waits for the retina for the brain to process the image on the retina, and we fix our retina for this process. People do this fixing movement the most when they are moving fast. In other words, pigeons’ eyes can move up to 10-20 degrees, but their heads move faster. In other words, we can say that it is normal for them to fix their viewing angles using head movement.
Sources: Wired, Evolution Tree, Ungo
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