The other day we wrote a post about the reduction in genetic diversity among commercial chicken breeds that attracted a surprising amount of informed comment (surprising to us, anyway; I think it shows more about the general knowledge of a city boy like me than anything else). So while we were on the subject of chickens (as we are so often because we write a lot about avian influenza) I thought I’d post up this remarkable YouTube video illustrating chicken head control. First a little background from the point of view of a human.
Humans also have remarkable abilities when it comes to head and eye control. There are six (extraocular) muscles that control each of our two eyes and since binocular vision depends upon both eyes peering at the same point they have to be coordinated. Moreover when you turn your head or your body but keep looking at the same point, the muscles have to coordinate precisely to keep the eyes pointing one way even though your head is pointing another (or moving in parallel when you look to the right or left). Remember these are two different kinds of movement. In convergence on a point the eyes are moving in opposite directions to each other, while in gaze to the right or left they are moving in the same direction. Four of the six muscles are aligned on a straight line (hence they are rectus muscles, numbers 2 – 5, below), while two are aligned obliquely (oblique muscles that pull the eye downward and laterally or upward and laterally, numbers 6 and 8). Here’s a pic:
This is all coordinated through the central nervous system, via three of the twelve cranial nerves (the 3rd, 4th and 6th; cranial nerves are nerves that come directly from the brain rather from the spinal cord). It is a very intricate and precisely coordinated system.
What does this have to do with chickens? Well chickens are amazing animals in their own right. We might think they aren’t very intelligent (their brains are quite small, i.e., they are bird brains) but small or not, it is capable of some pretty remarkable feats. So without further ado, we present the amazing video of chicken head control: