Three Gadwalls Showing Their Nictitating Membranes
A nictitating membrane is a translucent third eyelid present in some birds that can be drawn across the eye for protection and to moisten it while maintaining visibility. It can make the eye look white. It was quite a coincidence to have all 3 gadwalls cover their eyes like this at the same time. The coot does not, you can see its red eye.
Gadwall (Anas strepera)
American Coot (Fulica Americana)