Chickens, much like most birds and some mammals have three eyelids. They have upper and lower eyelids (like us) and a third eyelid that sweeps in from the side called a translucent nictitating membrane.
How Many Eyelids Does a Chicken Have on Each Eye?
As explained in the opening comments above, chickens have three eyelids on each eye. It’s not always easy to see their third eyelid, but it’s definitely there.
In fact, I’ve included a video below showing a chicken’s third eyelid flicking across their eye below so you can see exactly what I mean.
Their upper and lower eyelids are not the same as ours. They do not move them much, and certainly do not use them to blink as we do.
Related - Do chickens blink? (Only with their third eyelid!)
Why Do Chickens (and Other Animals) Have a Third Eyelid?
Birds and some other animals such as cats, camels, and polar bears, have a third eyelid called a nictitating membrane.
Interestingly we have the remnant of this same third eyelid ourselves. I’m talking about that little pink thing, that bit of flesh in the inside corner of your eye.
That’s right. According to RealClearScience, that is the remnant of a third eyelid that we used at some point during our evolution for the same reasons that other creatures have one today.
The main reason animals have this extra eyelid is that they aren’t able to use their hands or fingers to help get the dirt and debris out of their eyes.
Their third eyelids basically operate like windshield wipers. Because they can’t use a digit to get annoying bits of dirt and debris out of their eyes, a sleeve-like piece of skin does it for them.
It also helps keep the surface of their eyes moist and clean. It’s one of those evolutionary things that serves an important purpose so it’s stayed with the animals that need it.
If you watch the video below closely, you'll see their third eyelid flicking across the chicken's eye as it "blinks":
What Color Eyes Do Chickens Have?
Chickens’ eye color is an interesting topic. Chicks start off with dark eyes, looking like small black dots.
After about 8 weeks of age and as their eyes develop you will be able to see the difference between their black pupils and the colored part of their eye which is the iris.
In my experience, the most common eye color for chickens is a yellow-orange color. Browsing pictures online too, it does seem to be the most common color.
They can also have red, brown, gold, black, and even pink if they’re albino. If you spot one of your chickens’ eyes has changed color, that is something to get checked out as there are some diseases that can cause this.
Do Chickens Sleep With Their Eyes Closed?
This is another interesting question, and one I’ve seen debated a lot over the years.
Some owners say their chickens seem to sleep with their eyes open. Some say they have their eyes closed.
So, which is it?
Well, it can actually be a combination of both, or one or the other. Chickens are able to independently operate each eye while sleeping.
This means they can literally sleep with one eye open, and often do! When a group of chickens is on a perch, one on either end will literally act as a lookout keeping their outside eye open.
Another interesting fact about how chickens sleep is that they will often turn their heads upside down, and raise their lower eyelid to cover their eyes.
Third Eye Membrane Problems and Issues
There are a few eye injuries and infections that chickens are prone to. Although, in my experience, eye issues are not that common.
The most common causes of eye infections are bacterias. Salmonella, for example, can cause purulent conjunctivitis and will often be obvious when pus and inflammation are visible. This bacteria often causes inflammation of the third eyelid, too.
Sometimes fungal infections can cause the third lid to become inflamed too. The most common fungal infection is called aspergillus.
Typical symptoms for an aspergillus infection are respiratory problems, but it can also cause inflammation around and their eyes.
Whatever the cause, if you can see you have one or more chickens with eye issues unless you have experience dealing with similar issues, you’re best off consulting an avian vet.
The likelihood is they’ll treat the infection with antibiotics. But it’s important to know what exactly is the cause of the infection, as well as how contagious it is, what aftercare is required, and so on.
Related - Wondered if chickens have eyelashes? I explain whether they do or not in this post.
Now you know, chickens actually have three eyelids. Two that you can see, although they don’t use them to blink or close their eyes as we do.
Plus, another one that helps out by cleaning and protecting their eyes as you could see in the video I posted above.
Why do humans have a third eyelid - RealClearScience.com
Image credits - Photo by Hello I'm Nik ? on Unsplash