The most colourful terrestrial vertebrates are birds, the hands down-they are only creatures rivaled by insects and reef fish.
Birds have two fundamental color sources, like butterflies and moths. The more common are pigments that are chemicals in the bones or in the skin.
It is the reflected light reaching our eyes that absorbs certain wavelengths of light, and reflects others. The wavelength of the light stimulates the color we feel
Our retinas ‘ write the receptors. The smallest wavelengths can be considered to be “violet” in the visual part of the electromagnet spectrum and the longer to be “red.”
Thus, in their feathers a cardinal has a pigment that absorbs all wavelengths except those that are recorded as red when it enters our visual system.
When there is no reflection of light, we see darkness; white is whenever all wavelengths are reflected.
However, pigments never produce blue and iridescent colors in birds.
The blues are made of minute pollen droplets that are in diameter lower than the wavelength of red light. The blues are “structural colours.”
These particles can affect only shorter, “blue” wavelengths-reflected in all directions. They are “sparse.” Thus, when seen at separate angles in reflected light, the structural blue colours stay the same.
But the blue disappears if it is seen with transmitted light (that is, with the leaf between the light source and the observer).
Differential reflection of wavelengths produces Iridescent colors from the extremely altered Barbel of the rotational feathers that face the incoming light by means of a flat surface. The barbel’s detailed design represents some wavelengths and absorbs others, and with the angle of reflection the reflected wavelength shifts.
The structural color is recorded by the eye as a result of the wavelength reflected and the angle of the light, the reflective surface and the eye changing.
Like birds that haven’t been changing to please the human ear, birds haven’t evolved to please our eyes.
The most stunning colors usually impress members of the same kind
The classic instance is the tail of the pact, but it is illustrated by the brightly colored male Scarlet Tanager or King Eider. The bird often avoids predation in the non-demonstration of colors. An instance of such a cryptic colouration is the camouflage of a King Eider woman on her nest.
Many unnoticed birds display so-called’ counter shading; they are darker behind, and gradually lighter until their stomach is pure white. The bird absorbs most of the light above, where the light is brightest, and reflects the light below, where the light is dimest.
The bird tends to remove a strongly defined shadow. Most shorebirds have counter-shaded but the split between darker back and light abdomen can be quite sharp as with Snowy Plover.
“Disruptive” coloration— use striking designs to disassemble the bird’s contour
Another detection prevention technique. For example, in some circumstances, Killdeer and Semipalmated Plovers are extremely hard to see. Of course, among these birds, which merely take the background color against which they reside is the extreme in cryptic colour.
The classic instance is Ptarmigans in their white, pure winter plumage.
Birds often use colors to identify with and therefore keep other members of their flock.
For example, shorebirds like Ruddy Turnstones and Willets have been showing colored patterns in flight. Colors, such as inside chicks ‘ mouths, can also serve to boost feeding of their parents.
The feeding movements of young people may be directed by other colours, like the red dot on the Herring Gull’s note, which promotes young people to seek food and stick their heads to the adult’s mouth.