In
mid march, I had been to Sewri for a flamingo watch. It was a thrill to see the
beautiful avians take flight. But not only that, I also got an opportunity to see a great
variety of other water birds.
I
felt sad that such a biologically diverse ecosystem of the Sewri mudflats is
contaminated with oil spills. There are also a few wrecked boats lying near the
jetty.
On
one such old boat, I got an opportunity of seeing a Kingfisher take shelter.
And how beautiful it was! Turquoise blue plumage, with red straps on the wings.
Made me wonder where the bright blue colour comes from.
Usually,
the colour of a living organism comes from a pigment. Pigments are chemicals
produced by cells that not only perform some important function in the organism,
but also impart a distinct colour to the organism. For example, the green
pigment chlorophyll not only imparts a green colour to the plant, but its main
function is to trap light energy so that the plant can make food by
photosynthesis.
The
fruits and flowers of plants are colourful due to pigments like anthocyanin,
betalain etc..These pigments make the fruits and flowers attractive to insects,
animals and birds, thus helping in pollination or seed dispersal.
The
flamingoes are basically grayish white in colour. But the more they feed on
shrimps, the more pink their plumage becomes. That is because, the shrimps
contain the pigments alpha and beta carotenoids which are blue or green in
colour. When the flamingo digests this pigment, it turns pink in colour.
But when it comes to the kingfisher, it is an
entirely new story! The colours of the Kingfisher are not due to any blue pigment,
but due to the diffraction of light by the feathers. The true colour of the
Kingfisher’s plumage is a dull brown! But the beautiful blue is due to the
structure of their feathers, and the way their feathers reflect light.
And
how can we miss out on the magnificent peacock! The peacock’s colours too are
due to reflection of light – but in a different way. If you have had an
opportunity to see one these beauties, you may have noticed that as you look at
the peacock from different angles, you see different colours! These colours are
called iridescent colours. This is
seen because different waves of light interfere with each other, either
enhancing each other or nullifying each other, and as a result giving rise to
changing colours.
Further reading:
1. www.biologymad.com/resources/beetroot%20pigment2.doc
2. http://www.ias.ac.in/jarch/proca/1/1-7.pdf
3. http://www.webexhibits.org/causesofcolor/7D.html
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