In the bird world,
special coloration of feathers and quality of feathers plays a great role in
the choice of mates for breeding purposes. Ornithologists call this process
“sexual signaling”.
An English Budgie
and a Common Parakeet (photo: Dawn Griffard)
The female bird will make
a careful selection of a potential mate by examining the quality of his
feathers along with the brightness, iridescence and
saturation of their hues. Female
birds are so judgmental because they instinctively want to choose the
healthiest male to mate with in order to ensure the continuation of their
species.
High quality feathers
require a lot of energy and strength to create and maintain. Weak and sickly
males cannot afford such flashy feathers, as they must use every ounce of their
energy for mere survival. Therefore, that showy male is the best choice with
which to create strong, healthy babies. However, the cost of such flamboyance
is high. Bright colors and an often long, heavy tail mean that the male is more
conspicuous to predators and may have a harder time escaping through flight due
to the added weight.
Because of the high cost
of these bright colors, some species’ spring molt creates what is called an
“alternate plumage”, which allows them to have brighter feathers for just the
breeding season. This can be seen in the bright spring colors of buntings,
grosbeaks and wood-warblers. This spring molt may be just a partial molt which
replaces feathers in only certain areas. This requires much less energy than a
complete molt.
While we humans can see
many of those gorgeous feather colors that birds can display, some birds can
see so much more. Humans can see only a portion of the electromagnetic
spectrum. The electromagnetic spectrum is the range of all possible frequencies
of electromagnetic radiation. The “visible spectrum” is the portion of the
electromagnetic spectrum that is visible to the human eye. Birds can see the
same visible spectrum that we can, but they can also additionally see the
ultraviolet spectrum. The ultraviolet spectrum is invisible to the human eye. The fact that the ultraviolet light can be seen by birds opens up a whole other
world of possible “sexual signaling” coloration.
A photo sowing the
fluorescent feathers of a parakeet under a blacklight (photo: Dawn Griffard)
Just like those colors
that can be seen in the visible spectrum, colors that can be seen only in the
ultraviolet (UV) spectrum can be difficult for the birds to create and maintain. Therefore, they are also proof of the
strength and excellent health of the bird that displays them with gusto.
Recent studies have found
that it is mainly parrot species that display these ultraviolet colorations. Most species of parrot are not sexually dimorphic, which means that males and
females have similarly colored feathers. For example, the northern cardinal is
clearly sexually dimorphic – the male bird is bright red, while the female is
dull brown/gray with somewhat red wings and
tail. Most parrot species do not have these noticeable differences in
coloration. Perhaps this is why they have the added ability to create the
different colors in the UV spectrum in addition to the visible spectrum – to
prove their virility.
A male and female
Blue Front Amazon Parrot (photo: Dawn Griffard)
In addition to the UV
reflective plumage, many of these parrots also have “fluorescing” plumage. Fluorescent and UV reflective plumage on parrots are often found adjacent to
each other and are most often found in body regions associated with active
courtship displays. Although it has not yet been proven, it follows that this
coloration is probably also used in sexual signaling for breeding purposes.
Coloration and feather
quality is not always the way that males (and sometimes females) prove their
worth. Sometimes it also involves an elaborate song or a complicated dance. But a beautiful song or
dance without a fitting costume is a pale performance.
Submitted by Dawn Trainor
Griffard, World Bird Sanctuary Naturalist
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