Normally colour is derived from pigment. This makes it possible to colour clothes, foods, paint etc by simply adding various pigments to the underlying substance.
Iridescent colour does not result from pigment but from sub-micron structures that causes interference and diffraction of light. This is called structural colour.
It appears that the peacock’s, bright iridescent feathers may be covered in brown (melanin) pigment. The pigment appears to absorb background light and in doing so make the iridescent colour appear more vivid.
What inspired the unusual common name, Secretarybird, (Afrikaans: Sekretarisvoël) for this bird?
Perhaps we will never know for certain.
It is regularly told in South Africa that the common name of the Secretarybird is due to the dark quill like feathers, resembling a quill pen behind the ear (apparently common practice for an 18th century secretary).
A more recent theory is that “secretary” is a French corruption of the Arabicsaqr-et-tair or “hunter-bird”. Inspiration or after the fact fit?
The Secretarybird (Afrikaans: Sekretarisvoël) has the longest legs of any raptor. It use these long legs to kill pray, including snakes. It’s got a cool “serpent hunter” sounding scientific name Sagittarius serpentarius.
They have a normal upper lid that closes downwards when the owl blinks, a lower lid that closes upwards when the owl is asleep and a third translucent eyelid that closes diagonally across the eye to moisten and protect it while maintaining vision.
This third eyelid is called a nictitating membrane and can be seen in the left hand side eye of this Spotted Eagle Owl.
This photo was taken at Eagle Encounters at the Spier wine farm outside Stellenbosh, Western Cape, South Africa.