{"id":635,"date":"2020-02-21T20:34:27","date_gmt":"2020-02-21T20:34:27","guid":{"rendered":"https:\/\/nowthatswild.com\/new\/?p=635"},"modified":"2020-02-21T20:34:44","modified_gmt":"2020-02-21T20:34:44","slug":"the-nictitating-membrane","status":"publish","type":"post","link":"https:\/\/nowthatswild.com\/new\/the-nictitating-membrane\/","title":{"rendered":"The Nictitating Membrane"},"content":{"rendered":"

\"eagle\"\"eagle<\/p>\n

By Nicole Reggia<\/p>\n

Bald eagles, like other birds, have incredible eyesight. To help their vision stay sharp, they have the help of an inner eyelid called the nictitating membrane or plica semilunaris. This membrane is clearly visible, mid-blink, in the picture above and can be captured with a fast shutter speed camera.<\/p>\n

Eagles and other birds have three eyelids: top, bottom and horizontal. As the bird blinks, the nictitating membrane slides horizontally across the eye beginning in the inside corner, closest to the beak, then moves across to the outside corner. In addition to protection while attacking prey, this membrane keeps the eye moist and clear of dust. And, because the membrane is transparent, eagles never lose sight of their prey when the membrane draws across the eye.<\/p>\n

In most mammals, there is only a small vestigial remnant of the nictitating membrane in the corner of the eye. However, polar bears, aardvarks, camels, seals, marsupials and monotremes do have fully functional membranes. A good video of a crocodile’s nictitating membrane in slow motion can be viewed here:<\/p>\n