Posted by: Anne Murray | May 9, 2013

The bright colours of nature

Blue is an unusual colour in the animal kingdom, especially in northern latitudes, where muted shades of brown or grey are more common.  Blue plumage in birds is not a result of pigmentation but a consequence of light refraction through microscopic bubbles in the feather structure.

A trio of blue songbirds  are among my favourite B.C. birds:  mountain bluebirds, western bluebirds, and lazuli buntings.  Male mountain bluebirds are a beautiful turquoise, while the westerns have vermilion red chests and a contrasting deep blue head and back.  Lazuli buntings are named for the semi-precious blue stone, lapis lazuli.  All three birds spend the summer in B.C.’s  sunny Interior.

Light refraction is the reason the Steller’s jay (the common blue jay of the west, and BC’s provincial bird) will often appear very dark or even black, until, in turning, its back and tail suddenly flash with rich blue tones.  Many species of birds and insects have such structural modifications that create dramatic iridescence. Butterfly wings have crystal nanostructures (think unbelievably small) that selectively scatter light, revealing breathtaking colours.

The glittering throats, or gorgets, of male hummingbirds are caused by a combination of refraction and pigmentation, as is the green plumage of many tropical birds.  Carotenoids are natural pigments that reflect specific wavelengths of light, and result in red and orange colours, like those suffusing the plumage of house finches and orioles.  As male house finches mature, their red colour intensifies.  Black or brown colours in animals are due to the pigment melanin, which is also found in humans. It is synthesized within the body, unlike carotenoid which animals cannot produce.  Birds with red or orange plumage must therefore obtain their pigment from consuming parts of plants, such as seeds and berries.

Even experienced naturalists can be deceived by the colour of a bird’s plumage, if viewing conditions are difficult.  The speculum on a mallard’s wing can look green or blue, entirely depending on the angle, while even brilliant plumage can look all dark when seen against the light.  Identification becomes easier if one understands the nature of colours.


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