By Bill Pulliam
I have a couple of nephews who have lived in California for many years. Both are keenly interested in the natural world and love spending time in the wilds looking for snakes, birds, and other creatures. When they come visit us, it is always interesting to see the Tennessee natural landscape through different eyes. Different, not only in that they are young and from the west coast, but also because they are both red-green color-blind.
Most of us humans see the world through three primary colors, determined by the three visual pigments in our eyes. These three primary colors are not a “real” property of nature; they are just a peculiarity of our own eyes and minds. Some other animals see four primary colors, many see only two or have no color vision at all. The most common types of unusual color vision in humans are grouped together as red-green color-blindness, but they are not actual color “blindness” at all. This is just two-color vision rather than three-color. Blues and yellows are perceived normally, but the red-green distinction is weak or absent. About 10 percent of men have some degree of red-green color-blindness, which doubtless includes many Validity readers. It is much more rare in women.
Birds typically have strong color vision, sometimes much better than our own, using four primary colors and a broader rainbow encompassing hues we cannot see at all. Color is very important to many birds in their lives.
All major field guides for identifying birds are written by and for people with typical three-color vision. There are very few resources out there targeted to the color-blind birder. Obviously this presents challenges. Features that are described as “dramatic,” “brilliant” and “unmistakable” might be mushy, subtle or even invisible to you if you are one of these men. Add to this the large variability between color-blind men, and in many ways you are on your own.
Personally I only have a little bit of second–hand experience with color-blindness, but I have a lot of experience with bird identification. One of the things you learn over the years is how many different factors go in to being able to find and identify birds in the wild. Color patterns are only one item among many. There are skilled, experienced, accomplished color-blind birders in the world, each having found his own way through the challenges.
First among these challenges is the obvious one: the missing colors. Color patterns that are promoted in the field guides as clear and reliable identification characters may be essentially useless. To most birders the difference between male Summer and Scarlet Tanagers is clear cut: rich red with slightly darker wings versus flaming scarlet with boldly contrasting jet black wings. But if you are color-blind this is likely to be more akin to dark and dusky with darker duskier wings, versus dark and dusky with black wings. And, neither bird will contrast much with the leafy forest canopy in which it lives. But, there are other differences between these birds. Their voices are quite distinct (and they are far easier to hear than to see), they have subtle differences in their shape and structure and their bills show a small color difference that might be more apparent to you than to most observers.
Overall, if you are a color-blind birder, you may well develop your total birding skills faster than average. We who have many decades behind us rely to a great extent on things like voice, structure, flight style, behavior and many other subtleties that have nothing to do with color patterns when we identify birds. Pay attention to these and you will become a better birder sooner, not later, than someone who happens to have three-color vision.
Even on the color perception front, it is not all bad news. Red-green color-blindness is not only about reduced color perception. In the mushy middle of the color wheel are many yellowish-greens, bluish-greens, olive drabs, muted browns, and other hues often indistinct to typical eyes. These colors are abundant in nature. To most, this forms a mosaic of browns and greens with subtle color variations.
But to many color-blind eyes, these colors become soft shades of blue and yellow, with more contrast and better color distinctions than what most of us see. There are no LGBs (Little Green Birds), there are LY&BBs (Little Yellow and Blue Birds). This enhanced contrast also often makes patterns that are subtle to typical eyes jump out for the color-blind.
The ability of the red-green color-blind to spot military camouflage is well known; this can also work to spot natural camouflage. We once went hiking in the woods of west Tennessee with one of our nephews looking for snakes. A motionless cottonmouth on the forest floor was almost invisible to us but was easy for him to spot.
Returning to the example of the tanagers, the females of these two species are often difficult to distinguish, showing subtle differences in the shades of green and contrast with the wings. These might well be right in the range where they could be more obvious for many color-blind birders, not less. You might also find it easier to spot the heron in the grass, the owl in the tree or the sparrow on the twig.
The bird books will not give you guidance on the patterns that could be conspicuous to you but subtle for the rest of us, but you can learn these with practice. You may also find that the color reproduction in some books is better for you than others, so try a variety of them and see. Flip through and see which books show a Cardinal, a Robin and a Carolina Wren that look the same in the book as they do to you in the real world.
So far I have only been talking about color-blind men, as over 95 percent of color-blind people are male. A very small number of women will also have similar forms of color-blindness; for them the situation is the same as for the men. But for a much larger group of women, things are more complex. Few women express color-blindness, but over 10 percent of human females are carriers. If you are a woman with a color-blind father or son, you are a carrier. A color-blind brother gives you a 50/50 chance.
Even if you have no close relatives who are color-blind, you still might be a carrier. Surprisingly, because of the more complicated genetics of women, female carriers of color-blindness seem to wind up with better color vision than other women, not worse. They seem to get both the improved resolution of colors in the mushy middle, plus full perception of reds and greens. In some ways they resemble the birds and bees that see four primary colors rather than just three. Of course this can be a great asset to birding or any other visual activity.
So remember, guys, that if the women in your life sometimes seem to be able to see differences in color that are invisible to you, it may well be true.
Bill Pulliam got started in birdwatching by his junior high science teacher in 1974, and has been an avid birder ever since in 48 U.S. states and 7 foreign countries. He is currently the Tennessee editor for eBird, an online project that compiles millions of observations from tens of thousands of birders around the world.