I sure enjoyed my time spent photographing Short-eared Owls last week in Box Elder County in Northern Utah. They are amazing owls to see in flight, while hunting, preening or simply perched and looking around. I even have a few images of other Short-eared Owls dozing on fence posts but I do love to see their gorgeous yellow eyes. It might be because owls have front facing eyes or that their eyes are large or maybe both, but their eyes mesmerize me. Owls use both their hearing and sight when they are hunting prey.
Some birds, sharks, reptiles, and mammals have a translucent or transparent third eye lid called a nictitating membrane. This image shows a Short-eared Owl nictitating membrane that is partially exposed. The dark line near the center of the eye is the edge of the nictitating membrane. Unlike upper and lower eyelids which open and close vertically the nictitating membrane moves horizontally across the eye.
Nictitating membranes in owls moisten the eyes and protect them from dust, debris, while feeding their young or while catching or consuming prey animals. Since this owl was just perched it may have been just moistening its eyes with the membrane. Because the membrane is transparent owls can still see through the membrane.
I observed and photographed a Great Horned Owl nest for several weeks in Florida during the nesting season in 2008 where the female owl had a nictitating membrane in her right eye that was stuck in a position where it always showed. I am not certain what caused that to happen but I do know it didn’t prevent the owl from hunting for prey nor did it hinder her from taking care of her young probably due in part to the transparency of the membrane. Her single owlet branched and fledged in her care.
Life is good.