Have you ever wondered just how well your chickens can see? Or if they see in color or black & white? Or have you marveled at how they can spy a tiny bug or seed in the grass? Well wonder no more! I've assembled some fascinating facts about chicken eyesight for your reading enjoyment.
Chickens see basically the same way humans do - in color. They have a cornea and iris in each eye through which light enters before reaching the cones in the retina that sense the different colors. But that's about where the similarities end. Did you know:
- Chickens possess not only the three basic color cones that humans do (red, yellow and blue) but also an ultra-violet light (UV) cone. This allows them to differentiate between and see far more colors and shades than humans can.
- The UV cones help them to find shiny bugs, seeds, berries and fruits easily among non-UV reflecting grass and dirt.
- A mother hen also uses her UV cones to sense which chicks are healthiest, since growing feathers reflect UV light. She can therefore determine which chicks are growing fastest and strongest, and devote more of her energy to them to ensure they survive, since they have a better chance over weaker chicks.
- Chickens also have a motion-detecting cone in their eyes. This enables them to sense slight movements more easily such as bugs creeping through the grass or a predator lurking.
- Because chickens' eyes are more sensitive to light than humans and can detect far more subtle motion, the use of artificial light can lead to pecking within a flock because the flicking of a light bulb that is invisible to us humans appears to them like a rotating disco ball (trust me, being under a disco ball would make me grouchy too!)
- Because chickens evolved after the dinosaur age and didn't spend millions of years as nocturnal animals like many other species, their night vision is poor due to their low light sensitivity never having developed in the retina.
- In addition to the upper and lower eyelids similar to that which humans have, chickens have a third eye lid called a nictating eyelid that slides horizontally across their eye instead of moving up or down. This membrane is transparent, so often while dust bathing or foraging in dirt, chickens will close the nictating eyelid to keep debris out of their eyes.
- A chicken can use each eye independently on different tasks simultaneously.
- Just before hatching, a chick turns in the shell so its right eye is next to the shell (and absorbs light through the shell) and its left eye is covered by its body. As a result the right eye develops near-sightedness to allow a chicken to search for food, while the left eye develops far-sightedness, to allow a chicken to search for predators from afar. That is why when a hawk flies overhead, you will notice your chickens tilt their heads with their left eye to the sky.
- A chicken's eyes are about 10% of the entire mass of its head (conversely a human's eyes are only 1%) to allow them to see larger and more clear images.
- Because their eyes are on the sides of their head instead of the front, chickens have a 300 degree field of vision without turning their head, compared to the 180 degree field of vision a human has.
- Chickens can sense the presence or absence of light through the pineal gland in their brains, so even a totally blind chicken can still sense daylight as well as the changing seasons using the pineal gland.
So, now you know. Chickens see and sense far more than we as humans do. Fascinating animals, chickens.
The Eyes Have It by Julie Moore, Your Chickens Magazine, November 2013
If you like us on Facebook and our blog, you'll LOVE my new book
Order your copy ---> HERE!