How a chicken sees is much more amazing than you probably think, and completely different to what you see. Here are ten amazing and little known facts about chicken eye-sight.
1. Chickens see 300 degrees around them
Humans can only see things in about a 180 degree arc, but chickens can see 300 degrees around them because they can see with each eye independently – this is called monocular vision.
2. Chickens can’t swivel their eyes in their eye sockets
If they want to see something at the edge of their field of vision, they need to move their whole head.
3. Chickens use each eye independently, one near other far sighted
Right before a chick hatches, it turns inside its shell and tucks its head underneath its right wing, and this causes different development of the left and right eye. The right eye develops near-sightedness, and the left eye develops far-sightedness. So a chicken will use her right eye for searching for bugs and tasty morsels on the ground close to her, while at the same time using her left eye to keep a lookout for danger.
4. Chickens see fast movement better than humans
Chickens have better motion sensing ability than humans because of special structures in their retina called double cones. To a chicken, a fluorescent light flickers like a strobe light.
5. Chickens don’t see well in low light
Chickens’ eyes have fewer rods than humans, so their ability to see in low light is not nearly as good as ours.
6. Chickens eyelids close from bottom to top. And sideways.
Chickens close their eyes by moving their bottom eyelid up towards their top lid, and hardly move their upper lid at all.
Chickens also have a third eyelid, called a nictitating membrane. It’s a semi-transparent membrane underneath her eyelids, and it slides sideways across the eye from the front corner of her eye. It helps clean her eyeball, and protect her eye from dust and dirt.
7. Baby chicks see better than baby humans.
Baby chicks can see as well as an adult chicken. They even have colour preferences – they prefer red and orange rather than green or blue.
8. Chickens see in tetrachromatic colour.
Chickens see more colour than we do. We can see in colour because we have three kinds of specialised cones in our retina. The cones contain opsin proteins which are sensitive to light at three different wavelengths – red, green and blue – that’s called “trichromatic”. Chickens have “tetrachromatic” colour vision - sensitive to red, green and blue, but also the very short violet and even ultraviolet wavelengths.
Seeing ultraviolet means they see everything differently. Even when the male and female birds look the same in our colour spectrum, they can look different when the ultraviolet spectrum is included. The down of a healthy baby chick reflects more ultraviolet than a chick who is not so well. The mother hen can tell which chicks are healthy just by looking.
9. Even blind chickens can see light
The amount of light that a chicken is exposed to affects their egg laying – during the long bright days of summer they lay more eggs than in the short dull days of winter. And this is true even if the chicken is blind! She can sense light reaching her pineal gland right through her skull.
The pineal gland is located under her skull in the middle of her head. The pineal gland releases melatonin in response to periods of darkness, and switches off melatonin release on exposure to light. And the chicken’s skull is thin enough so that this organ can sense light and darkness right through the skin and bone. So even a blind chicken still responds to the seasonal change of light by coming into lay in the spring.
10. Chickens prefer beautiful humans.
And if all of this is making you wonder how beautiful you look to your chickens, then you might be surprised to know that it’s about as beautiful as you look to other people. A study in 2002 tested the preference of chickens for human faces. Surprisingly enough, the chickens showed the same preference for symmetrical faces that humans do.
For more fascinating facts, hints and tips about caring for your chickens, and the sheer pleasure of chickens, subscribe to my channel: Chickens in my garden - New Zealand
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