Introduction
When we think of light, we typically think of the sun or electric bulbs. However, there’s another form of light – the “ostrich light” – that deserves more attention. Ostriches and some other birds have a specialized structure in their eyes that allows them to see ultraviolet light. This ability has important implications for their behavior and survival.
The Anatomy of the Ostrich Eye
To understand how ostriches are able to see ultraviolet light, we need to examine the anatomy of their eyes. Like other birds, ostriches have a third eyelid, called the nictitating membrane, which is translucent and helps moisten and protect the eye. However, unlike most birds, ostriches have a small area in their retina that contains a high concentration of double cones, a type of photoreceptor cell. Double cones are typically responsible for perceiving color, but in the case of ostriches and other birds that can see ultraviolet light, they have an extra cone pigment that’s sensitive to UV.
The Benefits of Ultraviolet Vision
Ultraviolet vision allows ostriches to see details that are invisible to us, such as urine stains on the ground left by other animals or the glossy sheen on certain fruits and insects. This ability is especially useful for finding food and avoiding predators. For example, some caterpillars have evolved to reflect UV light, which makes them easier to spot for birds with UV vision. Ostriches can also use their UV vision to communicate with each other, since some of their feather patterns are UV-reflective.
The Evolution of UV Vision in Birds
It’s not clear exactly when and how UV vision evolved in birds, but scientists believe it may have initially evolved as a way to find food. Many fruits and flowers have UV patterns that are invisible to mammals but highly visible to birds, which might have given birds an advantage in foraging. Over time, this ability may have become more specialized, with some birds like ostriches and parrots developing highly complex UV vision.
