White Breasted Nuthatch Cardinal

Can Birds See In Color?

The answer is yes, but there are qualifiers to this answer.  Research into bird vision and their ability to differentiate colors began back in the early 70s. In the following decades scientists compared the three kinds of cone cells in our retina; the ones used to see in color (red, green and blue) and then looked at the retinas of birds and discovered that for diurnal (active by day) birds, there are four kinds of cone cells receptive to red, green, blue, and ultraviolet (UV) wavelengths. In addition, birds have a tiny drop of colored oil in each cone cell, which acts like a filter to minimize the amount of UV light coming in.  This bit of oil also allows birds to differentiate between similar colors far better than we can.IMG_4941_edited-1

But before we go further; an explanation of  just what is meant by UV light.  Most of us are very well aware today of the danger UV rays pose to our exposed skin.  That is because UV light is a form of electromagnetic radiation.  It is invisible to our eyes and so it is easy to ignore warnings from our parents or the medical establishment.  When our skin is exposed to too much UV radiation our body’s natural defense is to activate the melanin pigment, which absorbs UV light.  Melanin is what gives us our suntans, but get too much and even melanin cannot stop the damage to our cells.  Sometimes the DNA in our cells will mutate because of the UV radiation and that’s where the real danger comes – in the form of cancer.

The first line of defense from harmful UV radiation is the ozone layer, which will absorb most of the harmful ultraviolet B, or shortwave rays.   That’s one of the reasons there was so much concern back in the early 80s when a large springtime ozone hole appeared over the Antarctic. Happily, citizens of the world recognized the threat and in 1987 the Montreal Protocol was signed by every country in the United Nations, CFCs were phased out of production and the hole gradually shrunk.ruby throat 41 (2)

But UV light is still all around us, though we humans cannot see it with our eyes.  We can use a prism to break up radiated light into the visible spectrum of blue to green to yellow to orange to red.  But beyond the blue lies the ultraviolet.   It’s impossible for us to really know what the world looks like through a bird’s eye, but we can speculate that colors may be more intense due to UV reflectance.

There are many ways that their ability to see color, especially in the UV range helps birds. Scientists have discovered that the plumage of some birds reflects UV light, which could have implications for identifying male and female. Many baby birds also have a very bright gape (lining and edges of their mouths) which seems to stimulate the parents to offer food.  UV light reflects off of some berries and fruit, as well as some insects and certain flowers, thereby drawing the attention of birds. We have all seen how hummingbirds zero in on red flowers, so it’s not surprising that most hummingbird feeders are at least partially red, though having a yellow ‘flower’ also seems to be important.  American goldfinches are often seen perched on goldfinch on coneflowerssunflowers and other yellow flowers which makes the Finch Flocker nyjer seed feeder a good bet.

Maybe the next generation of bird feeders will have special UV designs that birds can’t resist. In the  meantime there is much more to learn and understand about bird’s vision.