The funky chickens
Less fun but slightly more informative:
Why they do this?, surely not just for our entertainment:
In order to spot potential food that is moving within a stationary background, the chickens must stabilise their eyes in space. Then the only thing that moves within the image falling on their retinas, is the moving target (e.g. a wriggling worm).
Their brains are unable to compute what is happening from a moving frame of reference. They cannot calculate the effect of a moving point of view on a stationary scene to detect movement within the scene (e.g. a wriggling worm), so they stabilise their head (more specifically their eyes). As explained in “Bottleneck”, this enables them to detect movement, using the inherent fading property of the eye, rather than by intensive cerebral processing.
These videos are relevant to the section: – Evolution of the Seeing Eye in Chapter 2 – Sense and sense ability, in the book: Bottleneck – our human interface with reality