H is for Hue – The Secret Miracle of Birds
The secret universe of birds is extraordinary – and completely unavailable to us. Their vision has more acuity – they can see far finer grades of every colour than we can. A lemon-yellow petal to them may be a myriad of lemon-ness we will never experience.
Colour is parts of light. Our eyes contain three cones that perceive red, blue and green light. From those colours and mixes of them, we see all the many colours available to us (but not in as much detail as a bird would) from that part of the spectrum, our visible spectrum.
But birds have a fourth cone, and that cone is sensitive to ultraviolet light, or UV. They see all colours available to us plus the finer grades of those, plus uv colours plus all those red, green, blue hues mixed with uv colours – colours that we cannot even guess at.
Even when we look at petals and feathers and things which we know look different under uv light – we can only see that they are different, like looking at red and yellow in black and white, we see one is darker, one is lighter, but we cannot see the colour. Because we have no cone we cannot see UV, but also, our brain would not be able to decode the colours we were seeing.
What sort of a world do birds inhabit? A very different one to us.
Photo © Ralph Arvesen.
Poem © Liz Brownlee.
Information from the book Bird Colouration by Geoffrey E. Hill, pub. National Geographic April 2010.
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