BirdNote® /Hummingbirds See Red
Air Date: Week of August 5, 2011
Hummingbirds’ eyes are designed to attract them to shades of red to yellow. As Michael Stein of BirdNote® reports, the birds preference for red is not the only reason they zoom in on a particular food.(Photo: © Tom Grey)
[BIRDNOTE® THEME MUSIC]
GELLERMAN: The color red signals 'stop', 'danger', or anger. But as Michael Stein explains in this week’s BirdNote®, the hummingbird sees red differently.
[Whistling wing sounds of male Rufous Hummingbird]
STEIN: The hummingbird we hear zipping by is likely seeking out red blossoms, or making a beeline for a backyard nectar feeder accented with red plastic. What is it about hummingbirds and the color red? Red flowers, and of course red feeders, are often rich sources of food for hummingbirds. The color red often signals high-octane fuel for their intensely active way of life.
[More Rufous Hummingbird sounds]
STEIN: The hummingbirds’ sense of color is due to the dense concentration of cones in its retina. The cones themselves contain pigments and oil droplets in shades of yellow to red, which seem to act like filters. The filters appear to heighten color sensitivity in the red to yellow range, while muting colors such as blue. But it turns out that it’s the nectar, not the color, that makes the most difference with hummingbirds.
By varying the nectar content of flowers, researchers were quickly able to switch hummers from a preference for red to a preference for the most nectar-rich flowers, regardless of color. So even though hummingbirds’ eyes have a heightened sensitivity to colors in the red to yellow range, the little sprites are fast learners and will go to where the nourishment is.
[More Rufous Hummingbird]
GELLERMAN: That’s Michael Stein, of BirdNote®. To see more photos of hummingbirds, flit over to our website, loe.org.
Sounds of the Rufous Hummingbird provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Wing sounds recorded by G. A. Keller; call while perched G.A. Keller.
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