Who would have thought- Sunglasses For Chickens! They were invented in 1939 to control cannablistic behavior of chickens.
Held on the chicken’s beak with a cotter pin through the nostrils of the bird. Chickens are provoked by the sight of blood and will peck at each other, eventually killing off much of the flock. These red lenses prevented chickens from seeing the red blood and calmed their behavior. These have not been manufactured for many years and we do not have any available for sale. These glasses are now considered a collector’s item. Source
Then I ran across Rooster Sunglass Drive Chickens Wild from Austrian Post, apparently they are still being used today!