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Earth Notes: Hummingbird Vision


What does a flower look like to a hummingbird? New research says it’s probably nothing like what humans perceive, because hummingbirds can spot ordinary colors blended with ultraviolet light. 

Humans have three types of receptors called “cones” in our eyes, which allow us to see three colors: red, blue, and green. When you blend light that is widely separated in the color spectrum, you get something called a “nonspectral color.” Red and blue, for example, make purple.

Sadly for humans, purple is the only nonspectral color we can see. But hummingbirds have four cones in their eyes. The extra cone allows them to see ultraviolet light.

So what happens if you mix red or green with ultraviolet? A research team led by Mary Stoddard of Princeton University wanted to know if hummingbirds can spot these weird blends of color. They set up two feeders at the Rocky Mountain Biological Station in Colorado. One feeder had sugar water and other just water. Both feeders had LED lights that emitted different colors. Broad-tailed hummingbirds quickly learned which colors were associated with a sugary snack, and they had no trouble telling apart the ordinary green, red, or yellow lights from the LEDS that emitted an ultraviolet combination.

Scientists believe nonspectral colors are hidden in flower petals and feathers, so a hummingbird’s world is painted in a dazzlingly array of these secret hues. Other birds, reptiles, and even fish have four cones in their eyes—and probably so did the dinosaurs. They get to see what humans can only imagine.


Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.