17 Nov 2015 Ethereal Colour in Nature, by Chané Jacobs
Having seen the rainbow long before I caught sight of the lilac breasted roller, I anticipated this shot when the bird landed on a branch near Camp Jabulani, posing with its face to the light. I approached slowly and stopped in a position so that the rainbow was directly behind the roller. I knew that I had only a few seconds before the bird flew away, so I hastily snapped a couple of photos. This is the one that turned out best, and I was absolutely ecstatic with the result. It is very unlikely that I will ever encounter such a sight again where such an abundance of colour is condensed in the same frame.
Birds can discriminate between greater varieties of colours than humans, including ultraviolet wavelengths. Arboreal bird species often display their bright, beautiful markings to members of the opposite sex, as a way of attracting attention. As their nests are built in trees, the birds provide shelter and natural forms of camouflage to their eggs, unlike the terrestrial bird species that tend to be a more uniform colour.
The beautiful colours of these birds are the result of pigmentation in the feathers. There are 3 different pigment groups, each resulting in a unique effect.
- Carotenoids are responsible for the bright yellow in many bird species, including the blackburnian warbler. These yellows arise from ingesting plants or insects that consume carotenoids.
- Melanins give feathers strength, and are often black, reddish brown or pale yellow in colour (depending on the concentration of the pigments at any location on that particular species). Melanins are particularly prominent in flight feathers, clearly seen on the wing tips, and reinforce feathers for the ongoing wear and tear caused by flying.
- Porphyrines, when exposed to ultraviolet light, are fluorescent. A wide range of colour can be produced by porphyrines – including pink, green, red and brown. This is clearly seen with the lilac breasted roller. The blue on the wing, however, is due to the non-iridescent feathers that scatter incoming light due to tiny air pockets in the barbs of the feathers.
The magnificent spectrum of light appearing in the sky behind the roller, otherwise known as a rainbow, is caused by the reflection, refraction and dispersion of light through millions of tiny droplets of water suspended in the air.
Or some say it is simply the magic of Kapama Game Reserve…