If you have been on the Internet for a while, you have probably been made aware of the secret shrimp colors: the colors the human eye cannot perceive, but mantis shrimp can due to them having more color receptors than we do. Bouts of incredible jealousy aside, it makes you wonder whether there are secret bird colors we are not aware of.
In short: yes. To understand how birds see the world’s colors, we need to first understand how and what we see. Our eyes are equipped with three types of color-sensitive receptors–blue, green and red–that allow our eyes to perceive what are known as spectral hues, a very fancy term for the colors of the rainbow. Because our blue and red color receptors get activated at the same time, we can also see purple, a so-called pure non spectral color. Birds, however, have not three, but four color cones. They are tetrachromatic (as opposed to our trichromatic selves), and can access colors within the ultraviolet (or UV) spectrum.
Alongside sounding incredibly cool, here is how their visual superpowers also come incredibly handy in the great outdoors.
You might struggle to distinguish berries among the undergrowth when on your afternoon walk through the woods, but birds haven’t got the same problem. That is because, as opposed to green leaves, seeds, fruits and berries reflect UV light and develop a coating as they ripen, making them pop.
Think of it as important food items being spray-painted neon yellow, for example! The same is true of certain flowers. Though already lush and beautiful to our trichromatic eyes, they must really look like a feast to birds. But what’s a great food source if you can’t remember where it came from? That is why hummingbirds have learned to associate certain colors with delicious nectar.
It’s not only plants that have a big “Eat me!” sign glued to their backs. Unfortunately for them, so do insects; their body coatings reflect UV light, making them that much more inviting to our insectivorous friends. And did you know urine likewise reflects UV light? It’s how kestrels and other birds of prey locate rodent prey. Uh-oh, mister vole… Looks like urine trouble!
By now you probably know that red birds get like that because of the food they eat and that more vibrant colors mean a healthier bird. It just so happens that the robustness of their immune system is imprinted on them from the moment they hatch. When you’re a tired bird mom or dad and food is finite, who are you going to feed first? As brutal as the reality may be, you are going to choose the chick that is likeliest to survive, and the amount of UV light your kids reflect is going to help you decide just who that is.
In the darkness of the excavated tree trunk you call home, glowing beak spots can also help you find where those hungry mouths are in the first place. Kind of like homing beacons… Pun intended.
Being a parent is a demanding job that most certainly isn’t for everybody, and there are a few species of birds, notably cuckoos and cowbirds, that seem to agree. Why go through the hassle of raising a brood, when you can just deposit your egg in the nest of an unsuspecting songbird and have them do all the work. You can even camouflage the egg to look like one of their own. Just you try and catch me!
Or so we would have thought. However, though they may look identical to us, some birds have learned to pinpoint and eject the unwanted parasite, and this nifty party trick may be accomplished thanks to UV markings invisible to the naked human eye.
The age-old question we ask ourselves when identifying birds is, Why are males so snazzy and colorful, while females are so dull and brown? Well, when it comes to plumage, beauty really is in the eye of the beholder. It turns out that those lovely ladies are not as dull as we may have thought; and that species where males and females look identical may not be as identical after all! Blue tit males, it would seem, reflect more UV light than females, and the ladies seem to prefer mates that reflect the most light.
Studies have shown that UV markings help them differentiate between individuals and choose a mate. And what is better than looking sexy while still keeping a low profile with regard to predators? Since the latter see only in the violet range, our spectacularly flamboyant Casanova just looks dull to them. Double win!
Bird migration is an incredible phenomenon, and there are several theories as to how these intrepid travelers figure out where to go, and how they get back home. One such theory is that birds use the Earth’s magnetic fields as their personal roadmap.
Incredibly, it has been suggested that they can see the magnetic fields in question thanks to certain photoreceptive proteins called cryptochromes that are contained in their right eye, helping to keep them on the right track! Red light, which is located at the opposite end of our visual spectrum, also interferes with their magnetic compass. That is where UV vision can come in handy.
See you later
Whether it is navigating treacherous terrain, optimizing feeding time or searching for the love of your feathered life, there is certainly more than meets the eye when it comes to how birds see. So, next time you want to call a little brown bird dull, remember, they may be breathtakingly beautiful to the ones who matter! As for us, how birds truly see the world will, sadly, have to remain a figment of our imagination!