Ducks Grow Tiny Clear Shields Over Their Eyes
When diving or flying through wind and rain, many ducks slide a thin, transparent third eyelid across each eyeball. This nictitating membrane acts like built-in goggles that keep their vision clear underwater or at high speeds.
💡 Fun detail:
The membrane moves so quickly that we almost never notice it, yet it lets a duck keep hunting even when a river is splashing or a storm is raging.
Source: Cornell Lab of Ornithology