I filmed this pair of Kookaburras as they were being swooped by an aggressive territorial butcherbird Kookaburras, like many birds, have a nictitating membrane, often called a third eyelid, which they can draw across their eye. This membrane is transparent or translucent and moves horizontally, protecting and moisturizing the eye while still allowing some vision. It's an adaptation for various reasons, including protection from attacks, debris, cleaning, and preventing retinal damage. #kookaburr