FEATURE
Moreover, in parrot retinas, each cone has four oil-droplet filters, being respectively polarising, clear, yellow and red. Thus – we have just three simple colour receptors, whilst parrots have four types of cone, each with four filters, giving an effective sixteen combinations. They can see more colours and shades than we can, as well as UV and polarised light. A parrot can look up into an intensely bright sky and see a distant dot as a hazardous bird of prey, while we will be simply squinting against the dazzling light. Anyone who is colour blind will know that
taking away just one of our colour receptors makes a big difference to our visual perception. Ultraviolet light does not penetrate through glass, so imagine then how a parrot’s normal perception of its world will be drastically altered when housed indoors. No wonder that parrots want to take flight and escape into the rich colourful outside world when they see an open window or door! There is no doubt that a parrot’s world looks very different to a human’s world. This perception of ultraviolet light is
important both for feeding and courtship in parrots. Ripe fruit glows with UV reflectance: Mark showed pictures of him walking around a supermarket with his Green-winged Macaw, with the bird ‘identifying’ the ripest apples! Male and female plumage that appears identical to us with our limited faculties will be very different to a courting parrot’s eyes. Thirty
A Sun Conure, showing yellow and red feathers coloured with psittacofulvin pigments; dark blue and black containing the pigment melanin; blue feathers from light refracting through the feather structure; and green colouring being a mixture of yellow pigment and blue refraction.
Blue-fronted Amazon parrots were studied under UV light, with particular reference to their wing and head feathers. These are areas of the body most used in courtship display. Sex of the birds was determined with 100% accuracy using the colour difference. Patagonian Conures were studied in a similar way, and cock birds were found to reflect far more bright green under UV light, while hens reflected more blue, and their red abdominal patches appeared different between the sexes with UV reflectance.
BIRD SCENE 29
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