Anna's Hummingbird
The shining magenta Face on this Anna's Hummingbird is not created by pigments, but by the structure of its feathers. There is a microscopically thin translucent coating on the surface of each wing scale and light reflects off both the front and the back of this layer. This layer also causes refraction (light travels slightly slower through it compared with air). But because the layer is so thin the light waves interfere with each other causing distortion of the colours, albeit pretty distortion. The same principle applies when a microscopically thin layer of oil floats on water, and you get a spectrum of colours. If the layer were just a few millionths of a millimetre thicker, the feathers would appear a different colour, just as the swirling colours of an oil sheen are caused by miniscule differences in the thickness of the oil layer. And if you view from the "wrong" angle, the shining colours disappear and the face just looks dull and dark. Incidentally the word iridescent comes from Iris, who was a Greek Goddess, and the personification of the rainbow. That is why the word iris is used to describe colourful things like eyes and flowers.
Anna's Hummingbird was named after Princess Anna d'Essling the 19th century Duchess of Rivoli, wife of Prince Victor Massena and son of one of Napoleon's Marshalls. It was named by René Lesson, a French naturalist who also had the Pool Frog (Pelophylax lessonae) named after him.
I photographed this male Anna's Hummingbird by the banks of the San Diego river in California, just before we set off on the Baja cruise.
Anna's Hummingbird
The shining magenta Face on this Anna's Hummingbird is not created by pigments, but by the structure of its feathers. There is a microscopically thin translucent coating on the surface of each wing scale and light reflects off both the front and the back of this layer. This layer also causes refraction (light travels slightly slower through it compared with air). But because the layer is so thin the light waves interfere with each other causing distortion of the colours, albeit pretty distortion. The same principle applies when a microscopically thin layer of oil floats on water, and you get a spectrum of colours. If the layer were just a few millionths of a millimetre thicker, the feathers would appear a different colour, just as the swirling colours of an oil sheen are caused by miniscule differences in the thickness of the oil layer. And if you view from the "wrong" angle, the shining colours disappear and the face just looks dull and dark. Incidentally the word iridescent comes from Iris, who was a Greek Goddess, and the personification of the rainbow. That is why the word iris is used to describe colourful things like eyes and flowers.
Anna's Hummingbird was named after Princess Anna d'Essling the 19th century Duchess of Rivoli, wife of Prince Victor Massena and son of one of Napoleon's Marshalls. It was named by René Lesson, a French naturalist who also had the Pool Frog (Pelophylax lessonae) named after him.
I photographed this male Anna's Hummingbird by the banks of the San Diego river in California, just before we set off on the Baja cruise.