Thanks to UV vision, birds see the world very differently than we do
Birds and UV Light: The Eyes Have It
How do birds detect ultraviolet (UV) light?
To answer this question you must understand avian eye structure. The human retina has three kinds of cone cells (receptors used for color vision): red, green and blue. By contrast, birds active during the day have four kinds, including one that’s specifically sensitive to UV wavelengths. There’s another difference: In birds, each cone cell contains a tiny drop of colored oil that human cells lack. The oil drop functions much like a filter on a camera lens. The result is that birds not only see UV light, they are much better than humans at detecting differences between two similar colors.
What does the world look like to a bird with UV vision? “We can’t imagine,” says Auburn University ornithologist Geoffrey Hill. Since birds can detect more colors than humans can, scenes may appear more varied. And colors that already are bright to human eyes are—if amplified by UV reflectance—probably even brighter to birds.