A Bird’s Eye View: Why Birds’ Vision is So Different From Ours
Birds have five senses, like we do, but some experts argue that a bird’s keen sense of direction should count as a sixth sense. One thing is for sure: ornithologists agree that vision is a bird’s sharpest sense. In fact, a bird can see more colors than a human can.
A Broader Spectrum of Vision
Bird vision studies have surprised experts. Not only do birds perceive familiar colors, but they also can see colors that are part of the ultraviolet, or UV, spectrum. Because of its ability to see these additional shades of color, the bird’s eye has far better visual acuity than the human eye.
The bird’s eye can determine the slightest differences between shades of color that the human eye is unable to detect. The explanation for this ability lies in the cones in the retina. Cones, or cells, in the bird’s retina help detect and differentiate color. Humans only have three cones in the eye’s retina. Birds have four, allowing for a broader spectrum of vision. This advantage enables the bird’s eye to detect the slightest contrast of color in their environment, helping them spot prey.
See also: Flower Colors that Attract Birds
Beyond the Human Eye
Having a broader spectrum of vision beyond what humans can see comes with many benefits. Ornithologists know that birds perceive differences in many objects that humans cannot:
Finding Fruit
Birds can see fruits such as berries and those with waxy coatings more clearly than humans. Waxy coatings reflect UV light, making them stand out against leaves and plants in the bird’s eye view. This assists birds in foraging. Certain insects and flowers reflect UV light, which also aids birds in finding these nutritious food sources.
Locating Prey
Hawks and eagles use this keen ability to see colors on the UV spectrum in their hunt for prey. Just as pet supply retailers sell UV light tools for pet owners to determine if their cat or dog has soiled areas in their home, eagles and hawks pick up the trails of mice and other rodents’ urine because of the urine’s high visibility in UV light. Whether the prey is visible or not isn’t relevant.
Recognizing Plumage
Because of their ability to see colors in the UV spectrum that the human eye can’t see, plumage of birds will appear different to other birds. Birdwatchers may not be able to clearly differentiate one gender from another in a species. Birds, with their keen ability to differentiate shades, can tell male from female. This is due to their ability to see markings on some bird species only visible in UV light. They often use these UV markings to select mates or tell individual birds apart.
Credit: TracyDifferentiating Eggs
It is common for interlopers to leave their own eggs in a different bird’s nest. It’s a great way to outsource the incubation process. A bird’s ability to differentiate shades on the UV spectrum helps nesting birds know when an egg is not their own. An interloper’s eggs may have similar visible colors and markings to their own. Being able to differentiate shades in the ultraviolet spectrum allows them to reject the imposter eggs.
See also: All About Hummingbird Nests
The Benefits For Birdwatchers
Understanding how birds perceive color is an ongoing study for ornithologists. Still, the results of research have already yielded beneficial advancements for birdwatchers. Equipment and tools that enhance the birdwatching experience include:
- The window decals recommended to keep birds from hitting the windows of your house now have UV reflective properties to work more effectively.
- Collars for cats, known predators of birds, are designed to reflect UV light to signal their presence to birds, giving birds warning to remain out of the cat’s sight.
- Clothing worn by birdwatchers is specially made to not reflect UV light, keeping the birdwatcher better camouflaged from a bird’s view. This helps the wearer remain out of the bird’s sight, helping them spot more reticent species of birds.
- To the delight of backyard birdwatchers, bird feeders are being designed with UV patterns that help catch a bird’s eye and lure them to visit feeders more readily. Ornithologists believe this will also increase the number of species backyard feeders may attract.
Night Vision vs. Day Vision
With colors in nature being more visible in daylight, it makes sense that diurnal birds (birds most active in daylight) have the sharpest sense of color.
Nocturnal birds have a different advantage when it comes to vision. Ornithologists have discovered a great number of rod cells in their eyes. Rod cells allow nocturnal birds to pick up whatever light is available, meaning they see better in conditions where light isn’t present. Still, colors will not be perceived by nocturnal birds as clearly as diurnal birds.
See also: A 5 Step Plan for Nighttime Birdwatching
Looking Forward
These fascinating discoveries are just the beginning of a whole new topic of discussion for ornithologists and birdwatchers alike. As more discoveries come to light, birdwatchers can utilize new tactics and gear each time they head out on a birding venture.
Discoveries in bird vision continue to show both ornithologists and birdwatchers that there is still much to learn about birds. While we may think we are seeing a dazzling array of colorful feathers at our backyard feeders, in comparison to a bird’s vision, we humans are colorblind.
