This colorful eyelid is known as a nictitating membrane. It is found in most predatory birds. It is a clear membrane that the Great Grey Owl can use to cover the eye protecting it from thrashing prey, unseen branches while flying through dense forest, or just to re-wet the eye balls. This owl’s nictitating membrane looks so colorful due to the reflection from the sun.
Gear: Canon 60D, Sigma 50-500 mm f/4.0-6.3
Settings: 1/640 sec, f/8.0, ISO 200