Iridescent Starling
It is quite easy to tell male from female Starlings in spring as they have a different colour to the bill base; Blue for a boy, pink for a girl. You can see the pale blue bill base here on this male. Another clue is that males sing at this time of year.
The beautiful purple and green iridescence is not formed by pigments, but by refraction of light through a microscopically thin transparent layer on the feathers. Light reflects off both the front and back of this layer and the light travels slower through the layer causing minute phase differences in the light which creates colours. Miniscule differences in the thickness of the layers create different colours; purples or greens in this case. The same thing happens with a drop of oil on a puddle. Each rainbow colour is created by tiny differences in the thickness of the oil layer. But if you catch the bird at the wrong angle the colours disappear and the bird just looks black, exactly the same as the iridescent colours on hummingbirds. Incidentally the word iridescence comes from Iris, the personification of the rainbow in Greek mythology. That's why beautifully coloured things like eyes and flowers are named iris.
Iridescent Starling
It is quite easy to tell male from female Starlings in spring as they have a different colour to the bill base; Blue for a boy, pink for a girl. You can see the pale blue bill base here on this male. Another clue is that males sing at this time of year.
The beautiful purple and green iridescence is not formed by pigments, but by refraction of light through a microscopically thin transparent layer on the feathers. Light reflects off both the front and back of this layer and the light travels slower through the layer causing minute phase differences in the light which creates colours. Miniscule differences in the thickness of the layers create different colours; purples or greens in this case. The same thing happens with a drop of oil on a puddle. Each rainbow colour is created by tiny differences in the thickness of the oil layer. But if you catch the bird at the wrong angle the colours disappear and the bird just looks black, exactly the same as the iridescent colours on hummingbirds. Incidentally the word iridescence comes from Iris, the personification of the rainbow in Greek mythology. That's why beautifully coloured things like eyes and flowers are named iris.