chicken anatomy – the nictitating membrane

I was out snapping photos of the chickens again yesterday. I zoomed in close and used a fast shutter speed to try to capture the moment they peck at food. I captured this image:

Do you see that white thing covering her eye? It turns out that when the chickens peck at the something they actually blink too. Birds have a third eyelid called the nictitating membrane which both lubricates and protects their eyes.

This nictitating membrane is between the other two eyelids and the cornea and has its own lubricating duct equivalent to our tear duct. (from here)

I feel like I learn something new about the chickens almost every day.