The eyelids of a Herring Gull don’t blink; the eye is lubricated by a transparent "nictitating membrane" that exists under their regular eyelids and moves horizontally across the eye. The membrane stays over the eyes while the gull is flying, protecting against harsh weather, like goggles. Nictitating membranes are found in fish, amphibians, reptiles, mammals, and birds, with the exception of the Horned Owl, whose upper eyelid is mobile.