A Bird’s-Eye View
One of the many things that make penguins unique from other birds is that they spend time underwater and on land. They go into the ocean to hunt for food and travel; on land, they breed, raise their young, and molt. The penguin eye has several adaptations that allow penguins to see well on land and out in the ocean.
Penguins have a flattened cornea that refracts light less strongly than human or fish corneas. Their strong eye muscles change the shape of their eye lens to create a sharp, clear image both on land and in water. In addition to this, penguins have a nictitating membrane, also referred to as a third eyelid. This membrane protects their eyes from any debris that might be underwater. These visual adaptations give penguins superb vision in and out of water, and means they don’t have to wear goggles when they go out in the ocean!
Penguins rely heavily on visual cues for foraging, making underwater vision a must for survival. As mentioned in a previous blog about penguin taste, penguins do not rely on taste for selecting their food. Great vision on land is also necessary to identify their mate, young, nesting site, and to avoid potential predators.
So how do their eyes tell them what a yummy feast might be? It is thought that penguins, as well as many other species of birds, can see ultraviolet light (wavelengths of 320 to 400 nanometers) that humans cannot see. The way that UV light reflects off different fish may show the penguin that it is appetizing.
UV light may also reflect off penguin feathers to help penguins identify each other and assist them in mate selection. King and emperor penguin beaks reflect UV light and are thought to be a part of the mate selection process. Penguins can also identify fish by size and by smell.