Chickens are fascinating and complex creatures; they are sociable but have an established pecking order when it comes to new flock members. Hens are good mothers whilst cockerels are protective and brave in the face of predators. Most importantly, despite the expression “bird brain”, hens are highly intelligent, employing behaviour that seems to us repetitive and bizarre but serves an important function.
A mother hen will sit on a clutch of eggs for 21 days depriving herself of food and exercise if necessary. She will pluck out breast feathering to produce a bald spot which is placed in close contact with the eggs to transfer heat. Her plumage provides a warm, humid environment and her body protects the eggs from predators. She turns her eggs regularly until three days before hatching. Chicks will communicate with each other whilst in the shell by peeping to ensure synchronization and enabling a clutch of eggs to hatch together. Once hatched they will use filial imprinting to attach them to one stimulus, normally the parent bird.
Your hen’s brain
Bird brain is often used as a derogatory term referring to someone not very bright. Yet chickens have very complex brains and use the information they process in a very particular way.
The chicken brain consists of two halves (known as hemispheres). Each half helps it to process information in a different way. This is known as lateralization, and it is more pronounced than that of the human brain. It is fascinating to realise that not only can a hen see the world using both eyes (binocular vision) they can also use each eye to look at a separate image at the same time with no overlap of visual information between the eyes (monocular vision).
Being a prey animal in nature the chicken relies on the location of its eyes to give a panoramic view of the environment and to warn of potential danger from predators, for this it uses its monocular vision. Its binocular vision is used when foraging for food and to identify other members of the flock.
Here is the clever part, chickens can process two sets of information at the same time! Whilst using one eye to look for food, the other eye is scanning for predators. If you have ever tried sneaking up behind a hen you will know how well this system works!
Have you ever wondered why your hens perform the same scratching routine in a set pattern using a series of alternative scratches? Chickens usually start with their right foot which is controlled by the left side of the brain. If the chicken finds food with its right foot, the right eye will see it first. The left side of the brain linked to the right eye is responsible for the chicken deciding if an object is food or not. A quick decision can then be made, and the food is quickly eaten.
When your chicken is still in the egg waiting to hatch, the left side of the head is usually tucked under the wing. More light, therefore, passes through the shell and reaches the right eye at the important time when the nerves associated with vision are developing. The young chick, therefore, has a natural preference to use the right eye to peck at feed and the left eye tends to be used more for identifying predators. Rather like a human child being right or left-handed.
Finally, ex-commercial caged hens that have never walked on solid ground or experienced sunlight will immediately demonstrate natural behaviours such as dust bathing, sunbathing, and scratching the ground despite never having any experience of these conditions. This shows us that behaviour is intrinsically innate and not learned.