The HANZAB entry for Adult Male goes on: ‘… often with paler blue (168B) outer ring; also described as blue or violet; when distressed, such as when captured, some birds have a magenta or red tinge to iris, caused by vascularisation round
inner rim of iris’. With same cautions as previously I offer a representation of colour 168B:
The vascular magenta can easily be seen in a well-lit image (either from flash or digital brightening). Examples below, which give some idea of the structure of the veining. . It might be due to excitement – along with the protruding
eye. It is difficult to gauge whether it varies over time in an individual bird. However it is certainly not limited to highly stressed captured birds, but is evident in birds that are engaged in moderately unexcited bower-tending, or even resting on a branch.
