There’s an abundance of bird species, most of which have specialized traits that help them get through their day.

Not all species of birds have large talons to catch their prey, or are able to drill a hole to hide their food. But no matter what species you choose to examine, all birds share one unique visual capability – the ability to see the standard color range, but also the reflective ultraviolet light spectrum.

This unique sense is crucial for finding food, locating a mate, spotting prey, and a whole lot more.

Cones in the retina of the eye are cells responsible for detecting color. Humans only have three cones (red, blue and green), but birds can have four cones or more, depending on the species. This allows them to see within the spectrum of ultraviolet light.

Bird’s Eye View

Human’s Eye View

Birds that are active during the day have better detection of color than birds active at night. Nocturnal birds such as owls have a larger number of cells that allow them to enhance their sight in low-light conditions. They might not see colors as clearly as diurnal birds, but having more rod cells lets in more light.

Having such an exceptional sense certainly changes a bird’s perspective on everything in its environment. Birds can see visible colors more distinctly than a human because each cone in a bird’s eye holds a drop of colored oil that selectively filters out specific colors. This is similar to how a camera lens works. It gives the bird greater sensitivity to shades of colors. In turn, it allows the bird to visualize contrast in its surroundings. It then gives them the ability to see through other prey’s camouflage.

As an example, fish-eating birds then can see more clearly through deeper water, allowing them to catch their prey more easily.

Raptors (hawks, owls, falcons) can track their prey with the use of the UV light. Rodents splatter urine as they walk along, marking their territory. The urine becomes vibrantly noticeable in ultraviolet light. A raptor can then hone in directly on where their prey is located.

For birds that eat seeds, berries and insects, the ability to see ultraviolet is a direct advantage. Some fruits, including berries, are covered in a waxy coating that reflects the ultraviolet light, allowing the bird to see its food more clearly. Some insects and flowers and other plants also reflect ultraviolet light.

Birds use this unique sense of seeing in the ultraviolet range to defend their territory, choose a mate and distinguish their eggs from parasite eggs (i.e., eggs lain by lazy birds that prefer someone else hatch and raise them).

Even if the parasite eggs are identical from the eyesight of a human, the original nest builders see the difference and often remove the intruders from the nest. A pair of adult birds might look exactly alike to a human, but to the birds, with their ability to see ultraviolet, they can easily identify the males from the females.

The advancing study of how birds see has contributed to the development of tools that help keep birds safer. For example, adding ultraviolet reflective substances to window decals helps to prevent birds from flying into glass doors and windows. Field items used by birdwatchers can be treated to prevent birds from detecting the ultraviolet light, which then acts as camouflage.

One thing that was developed, I’m not so sure I agree with – collars for cats that are designed with reflective UV light. The concept is that the predator (in this case the cat) will be more visible to the bird, and it can quickly escape. That’s fine for a small bird, but what if that bird is a hawk or an owl? Wouldn’t that attract the raptor to see the cat as prey? Adios, Fluffy.

Even if you have only three cones in your eye, keep them open out there anyway. You never know what you might see or find – even if you can’t perceive the incredible spectrum of ultraviolet light.

Mari Carbajal is a docent-naturalist at the Placerita Canyon Nature Center.