Virginia Wildlife Demo - 13

©Maslowski Photo

bluebirds manage to be blue? e trick is that
most blue animals aren't using pigments at all.
Instead their blues are made when light hits
microscopic gaps in their surface layer. ese
gaps act like little prisms-splitting, adding,
and subtracting wavelengths of light. When
light hits these gaps, they shift the wavelengths so that reds and yellows are cancelled
out, and blues and violets are amplified. A
similar trick explains the iridescent, shimmery patterns that we see on starlings and
hummingbirds. It also explains why the deepness of the blue or the shine of the shimmer is
dependent upon the viewpoint from which
you're looking at a feather. e feather only
refracts light back to specific viewing angles.
e bottom line: ere is more to color
than first meets the eye. Walking through the
forest on a spring morning is like walking
down a busy city street; you're being bombarded with signs, signals, warnings, and advertisements. All you have to do is open your
eyes. *
Jason Davis is an assistant professor of biology at
Radford University. His research focuses on
physiological processes in wild animals.

The contrasting black and white stripes of a skunk provide an unmistakable warning. Right, the
pale blues and deep reds of this tom turkey's wattle make him irresistible to females of his species.

ed woodpeckers all get their hallmark reds
and yellows from the carotenoids in their
diets. If they are fed a perfectly healthy, but
otherwise carotenoid-free diet, these normally colorful birds become a drab grayishbrown.
is isn't to say that animals don't have
some amazing tricks in their own color
palettes. Some species of birds produce porphyrin pigments. Porphyrins can provide a
green or yellowish hue, but their most impressive eﬀects only show up under ultraviolet light. UV light makes porphyrins
fluoresce, glowing brightly. Humans can't see
into the UV end of the spectrum, but many
birds can, so a sparrow that looks boring and
brown to you might be bright and colorful
when seen through the eyes of other sparrows.
Surprisingly, the trickiest color for animals to make is just plain old blue. Most animals can't produce blue pigment molecules,
and the delicate blue cyanins of plants don't
survive digestion. So how do creatures like

©Jason Davis

green light and it won't do very well, because
it won't be able to absorb enough light energy
to photosynthesize correctly.
Chlorophyll is far from the only pigment that plants make. In fact, plants are
masters of color chemistry, able to produce
and combine pigments to produce an enormous range of hues. For instance, carotenoid
pigments create reds, oranges, and yellows,
lending color not only to carrots but also to
tomatoes, bell peppers, and roses. At the other
end of the spectrum, plants make bluish-purple cyanidin pigments. Cyanidins make blueberries blue, and give characteristic shades to
the tissues of grapes, violets, and cabbages.
However, though pigments are easy for plants
to manufacture, they can be quite diﬃcult for
animals to produce. Most animals can make
melanin, a pigment that absorbs most wavelengths of light and so appears dark brown or
blue-black. But red and yellow pigments are
much harder to make for animals, so they
typically steal them from the plants they eat.
House finches, cardinals, canaries, and pileat-

Virginia Wildlife Demo

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