Why Do Female Cardinals See Red?


By Sarah Wilson, MA

It’s long been known that female Northern Cardinals prefer the reddest males around. What hasn’t been understood until recently is why?

The first clue to this mystery is that what birds eat impacts how they look. It does for us, too. If we consistently binge on carrots, overtime we can turn ourselves a harmless and temporary shade of orangey-yellow. Change our diet, and we return to our usual skin tone.

Cardinals, too, can change their color by eating a lot of colorful foods. But, given that all the Cardinals in a given area are probably eating much the same diet, why is there a range of redness among the males? Because some birds covert one carotenoid (color pigment in food) to another especially well. That conversion, which takes place within the bird’s cells, is reflective of general cellular health. Healthy cells make for a healthy bird.

So, why do female Cardinals see red? Because they know that the reddest males are the fittest males.

Nature is amazing.