A male hummingbird simply pausing on a perch can mesmerize us with his colorful, iridescent plumage. But it turns out we humans are likely missing the full effect—because hummingbirds see colors that humans cannot detect, a new study says.

Scientists have long known that birds probably have better color vision than humans do. Like most primates, humans are trichromatic—that is, our eyes have three types of color-sensitive receptors or cones: blue, green, and red. But birds have four color cones, meaning they are tetrachromatic.

With our three color cones, we can see the colors of the rainbow—red, orange, yellow, green, blue, indigo, and violet—the so-called spectral hues. We can also see one pure nonspectral (meaning, not in the rainbow) color, purple,